Boeing P-26 Variants

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Aerofax Minigraph 8

BoeingP.26 Variants by Peter Bowers ISBN 0·942548·13-2

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THE BOEING P-26 VARIANTS STORV

Three-quarter front view of the Boeing XP-936 wind tunnel model without propeller. Also missing are the flying wires for the wings and tail surfaces and other miscellaneous details such as the radio mast and exhaust pipe complex. Model, dated February of 1932, was meticulously built of hardwood with a metal Townend ring and engine parts.

CREDITS: The author and Aerofax, Inc. would like to express their thanks to the following individuals who contributed photographs andlor data to this Minigraph: Dana Bell, Jack Binder, Dustin Carter, Robert Cavanagh, Harry Gann, Walter Jefferies, Fredrick Johnsen, John and Joe Kobe, Edward LePenske, Edward Maloney, Mike McCary and Crown Hobbies of Dallas, David Menard, AI Hansen, James Morrow, Marilyn Phipps of Boeing Historical Services, Kenn Rust, Victor Seely, Jay Spenser, Gordon Swan borough of Air International, Robert Volker, Gordon Williams, and the late A.U. Schmidt, Eugene Sommerich, and Joseph Nieto.

PROGRAM HISTORY: The Boeing P-26, unofficially nicknamed Peashooter (in the 1930's the term Peashooter was often applied to single-seat pursuit aircraft; in the context of present-day historical references, the term is generally considered to apply specifically to the Boeing P-26), is unique among US Army pursuit aircraft for at least two reasons: it was not developed under a standard US Army Air Corps experimental contract, but rather as a private venture of the manufacturer with the aid and encouragement of the Air Corps Materiel Division at Wright Field, Dayton Ohio; and it broke the established Air Corps tradition of dual procurement of equivalent models (Curtiss P-6 and Boeing P-12 pursuits; Curtiss 0-1 and Douglas 0-210-38 observation models simultaneously, for example). While the Curtiss XP-934 (later designated XP-31 by the US Army Air Corps) was considered the Boeing XP-936's (P-26 family prototype) primary competition, only the Boeing pursuit was to see production. This reached a total of only 136 P-26NBIC airframes. Though appearing small, this order represented the largest single new pursuit design procurement since 1921. There was, however, justification for the small production run, as both the Army and Boeing realized that the new monoplane was strictly an interim model. In fact, an entirely new generation of high-performance monoplanes, with more powerful engines and structural and aerodynamic improvements, was already under consideration. In its transitional role, the P-26 was also notable for being both a last and a first. It was the last Army pursuit

to feature both an open-cockpit and fixed landing gear with externally-braced wings; and concommiUantly, it was also America's first production all-metal monoplane pursuit. Production P-26's had a US Army service life of eight and one-half years and eventually became the first US service aircraft to be passed on to other nations for continued use. At the time, this was considered extremely unusual as previous US military aircraft had been scrapped or relegated to training schools following their sevice careers. It is interesting to note that the last two of the numerous P-26's relegated to foreign service use were not retired until 1956. Both aircraft, at the time operated by the Guatemalan Air Force, were returned to the US. They are, today, the only known surviving P-26's. In 1931, when Boeing's historically significant P-12 and

F4B biplane fighter series was still selling well to the US Army and Navy, respectively, Boeing intuitively foresaw that the end of the biplane era was near. In fact, the company had just introduced a revolutionary commercial monoplane, the Model 200 Monomail, and had already interested the Army in its Model 214 and 215 twin-engine bomber derivatives which the Army bought as the Y1 B-9 and YB-9, respectively. Even more significant was the fact that the company was then designing an equivalent civil transport, the Model 247, which was soon to revolutionize the air transport industry. Since the speed of the new B-9 was expected ·to be greater than that of contemporary pursuit aircraft, Boeing offered the War Department an opportunity to develop a new pursuit generation that would be faster than the new bombers then under develqpment.

Wood and fabric full-scale mock-up of XP-936 lacks tail surfaces and landing gear. Noteworthy are the external wing root mounting of the camera gun, the abbreviated windscreen and headrest, and the use of a rea; engine. Photo was taken on November 25, 1931.

Boeing had already anticipated the advent of the monoplane pursuit with the Model 96 of 1929, a highwing design that the Army financed as the XP-9 for a low priority experiment using all-metal construction. The Model 96 number was in the sequence of Boeing design numbers reaching back to the Boeing Model 1 of 1916. Not every Boeing design study assigned a number was built and not every assigned number was given to an airframe; there was, in fact, a series of model numbers from 104 through 199 that was reserved for Boeing-designed airfoils. The XP-9 proved unsatisfactory aerodynamically, but Boeing tried again in 1930 with its Model 202 and 204 which were nearly identical all-metal parasol monoplanes tested by the Army and Navy as the XP-15 and XF5B-1 , respectively. Both were essentially conventional biplanes with their lower wings removed. No orders for these aircraft were placed. Following introduction of the revolutionary Monomaif in May of 1930, Boeing initiated preliminary studies for a new pursuit, the Model 224, in February of 1931. This was essentially a scaled-down Monomaif with a similar low tapered cantilever wing housing a backwardretracting landing gear, all-metal semi-monocoque construction, P-12E tail surfaces, and a 550 hp Pratt & Whitney Wasp engine. Old pursuit traditions were maintained in the form of an open cockpit. Informal discussion of the Model 224 between Boeing and Wright Field representatives aroused little official interest; regardless of major advances the Army had no requirement for a new pursuit aircraft at the time. Boeing therefore shelved the Model 224 and went b~ck to the drawing board to layout a more simplifiecf design, the Model 245. The Model 224 concept was not to die out just yet, however. It was revamped two years later as the Model 264, which first flew in January of 1934. The Army bought three examples as the YP-29 for service test, but did not order the type into production. By that time, with a new generation of larger, more powerful, and more streamlined pursuits on the drawing board, the YP-29's actually offered too little, too late. The Model 245 was a wire-braced midwing monoplane, still with the Wasp engine and open cockpit, but. with a rigid single-leg landing gear attached to the fuselage. The basic concept of the forthcoming P-26 was now established. Wright Field representatives quickly saw the design's potential and with suggestions and recommendations, they encouraged Boeing to expand and develop the studies further. The result was the Model 248, a low wing monoplane with fixed landing gear attached to a stub center section integral with the fuselage that was very similar in appearance to that found on the new record-holding Gee Bee racer. The wing was wirebraced from the landing gear and top of the fuselage. Wright Field representatives, though still hobbled by Headquarters budgetary constraints and no specific requirement for a new pursuit, now saw a design that it wanted. An ingenious solution to the Army's dilemma was soon worked out. Boeing would design and build three prototype pursuits and deliver them to Wright Field for Army testing on a bailment contract as company-owned aircraft. To reduce initial costs, Wright Field would lend Boeing all the hardware that was normally supplied as government furnished equipment (GFE) for contracted military aircraft. This included the powerplant, the propeller, the armament, instrumentation, and other items, all of which nearly equalled the cost of the airframe in which it was installed. This proved advantageous to both parties as it allowed the Army Air Corps to evaluate a new and advanced design at essentially no cost; and Boeing took a relatively small financial gamble on a possible substantial order in the shrunken military and civil aircraft market of the early Depression Years. XP-936: Design work on the Boeing Model 248 (the prototype for the P-26 family) started in September of 1931, under the direction of Project Engineer Robert Minshall. The Model 248 was later assigned the Wright Field XP-936 designator. This represented number 936 in a series of experimental aircraft, both military and civil, tested at Wright Field and its predecessor, McCook Field back to 1917. Originally, the "P" stood for the word "plane", but by the time the series reached 9QO, the letter indicated the type of aircraft (as P for Pursuit, B for Bomber, etc.). The XP-936 designation was assigned upon signing of the bailment contract for the first three aircraft on December 5, 1931. There was a time advantage in developing the new pursuit as a private venture instead of as Army property. As an Army-owned model it would have to incorporate 2

many of the detailed requirements of the Army's bible, the Handbook of Instructions for Airplane Designers (HIAD). Boeing was guided by the major requirements in this publication, but was able to eliminate many of the lesser ones as being unnecessary for a "proof of concept" prototype. The first metal was cut on the prototype aircraft in January of 1932, and in an attempt to speed up the main construction process, Boeing early-on elected to move engineers and drafters into the construction area to be in close proximity to the actual aircraft. Many parts were actually built from free-hand sketches and on a handfitted basis. Ten weeks after the cutting of the first metal, the prototype XP-936, cln 1678, was completed at Boeing Field. This aircraft, with ballast in place of armament and fuel in the main tanks only, was successfully test flown for the first time on March 10, 1932, from the company's Boeing Field, Seattle, Washington facility. A preliminary evaluation permitted company test pilot Les Tower to conclude that the new aircraft had excellent flight characteristics. Following additional test flights under the auspices of Boeing, Tower, on April 16th, ferried the XP-936 to Wright Field where it was formally turned over to the Army on April 25th. The second XP-936, cln 1679, destined for static test, was flown away on April 22nd by Lt. L.H. Dawson, an Army pilot, even though it was still Boeing property. It reached Wright Field via a circuitous route; March Field, California, and the Anacostia Naval Air Station, Maryland. Upon arrival at Wright Field, it entered the static test laboratory and never flew again as Army property. The third XP-936, cln 1680, was flown directly to Selfridge Field on May 6th by Maj. G. E. Brower for evaluation by the three squadrons of the 1st PUrsuit Group. Oddly, though the XP-936's were company-owned aircraft, they did not carry civil registrations. Apparently their military markings and coloring, plus the "XP-936" lettering on their tails, qualified them as military aircraft in the eyes of civil officials and thus legitimized the absence of civil registration. XP-26: After the initial XP-936 flight test program was completed by Boeing and Army pilots (all three aircraft were officially acquired from Boeing by the Army under a purchase contract signed on June 15, 1932), the Army cautiously concluded that the type was indeed a significant improvement over available pursuits and therefore a worthy addition to the operational inventory. Though concern over high landing and takeoff speeds, overly long takeoff and landing distances, slow response to throttle retardation, and rapid acceleration in a dive (considered a negative characteristic at the time!), remained, it nevertheless elected to squeeze production funding out of an already overburdened budget. A last minute addition to the 1932 Fiscal Year Budget, which ended June 30,1932, included funding for an initial P-26 order. Interestingly, once they became Army property, the three XP-936 prototypes were assigned a standard US Army Pursuit-series designator, XP-26, to indicate that they were technically experimental prototypes (official acknowledgement of the designation assignment was consequent to the acquisition of the aircraft on June 15, 1932). Army serial numbers 32-412, 413, and 414 were assigned at this time, identifying the 412th, 413th and 414th Army aircraft procured in Fiscal Year 1932 (July 1,1931 through June 30,1932). Y1P-26: As a deviation from standard practice, the three prototypes did not retain their X-prefixes permanently, as was customary for new prototypes. Instead, the Army decided to change the status of the new aircraft from "Experimental" to "Service Test", thus requiring the replacement of the "X" prefix with the "Y" prefiX. To complicate things even further, in some cases, such as with the three P-26 prototypes, the designation became Y1 P-26 to indicate that the aircraft were paid for with the F-1 funds rather than regular Air Corps appropriations. Usually, service test models were procured on separate contracts and were different aircraft than the prototypes. XY1P-26: As a still further oddity, the X and Y1 designations were combined briefly in August of 1932, as the XY1 P-26. This was apparently for administrative purposes only, though it must have caused some rather serious confusion among bureaucrats requiring accurate designation information I P-26: Eventually, all the prefixing designators were dropped, as was customary in the Air Corps during this time, and the XY1, Y1, and Y prefixes were removed from the P, and three prototypes thus becoming simply P-26.

Though the fate of the second P-26 was sealed when it became a structural test article at Wright Field (being removed from the Air Corps inventory in September of 1932), the first and third aircraft had relatively long lifespans. The first P-26 remained at Wright Field during most of its flight test and evaluation program, and then was assigned to Chanute Field, Rantoul, Illinois. Eventually it was declared "Class 25" and was utilized for ground crew training. It had ac.cumulated a total of 465 Army flight hours by this time and was eventually scrapped. The third P-26 prototype shuttled back and forth between Selfridge and Wright Fields on various test and evaluation programs before crashing on October 12, 1934, due to the loss of a wing in flight near Baltimore, Maryland, with a total of 344 Army flight hours in its log book. Boeing Model 266: Flight and structural testing of the three prototypes had led to a number of relatively minor changes in the production airframes and other systems. Among these were the elimination of the mainwheel cowling protrusions visible just behind the rear strut fairings; a change to smaller-diameter main gear and tailwheel wheels and tires, and reduced area ailerons. Less noticeable but of perhaps greater importance were the various internal changes which included redesign of the wing structure (though the physical dimensions of the wing remained essentially unchanged with the exception of an 11-5/8" increase in span); and provision was made permitting the installation of Type A-4A skis or Type A-8 wheel-skis as alternatives to the standard landing gear. In addition to changes brought on by design considerations, there were also areas of contention expressed by the various test pilots who had been privileged to fly the two available XP-936 prototypes. Among these were: no handles or steps were provided to aid a pilot wearing bulky flying clothes during ingress and egress; the instrument panel and engine cowling vibrated excessively at low and high engine rpm; and some controls were inaccessible from the seat when the pilot was properly strapped in place. Additionally, it was noted that forward vision was obscured during taxi by the Townend ring; and stability during takeoff, due to the short coupled landing gear, was marginal. Pilots also noted that normal flight attitude recovery was slow following pitch change inputs; an unassisted recovery to level flight during a banking maneuver at high speed was difficult to obtain and usually resulted instead in an ever-increasing spiral to the left, and eventually, a spin; and landing speed (82 mph) and landing roll-out (350 to 400 yards) were excessive. P-26A: The initial Army order, placed on January 28, 1933, was for 111 production P-26A's. This was later amended to include an additional 25 aircraft, thus giving a total of 136. Unit cost, less GFE, was $9,999, with total airframe production costs being $1,163,192. A parallel Army contract with Pratt & Whitney resulted in an order for 121 R-1340-27 Wasp engines at at total cost of $540,778. On November 24, 1933, less than a year after the Army ordered the production version of the XP-936, the first P-26A was assembled on Boeing Field. Boeing test pilot Les Tower made the first flight on December 7th. The first article, 33-28, was turned over to Air Corps Captain C. H. Strohm on December 16th, and he promptly took off for Wright Field. The first P-26A for a squadron, 33·30, left the same day for Barksdale Field, near Shreveport, Louisiana, piloted by Lt. E. M. Robbins of the 20th Pursuit Group. The last P-26, 33-138, would be delivered to the 1st Pursuit Group at Selfridge Field just over six months later, on June 30, 1934. P-26B: The first batch of P-26A's was followed by a contract revision calling for an additional twenty-five aircraft, this being the result of a good P-26A service record. These were identical to the first P-26A's except for the addition of flaps. Later, as a result of the successful service testing of seven Curtiss P-12E's with fuel-injected R-1340 engines (leading to a temporary XP-12K designation being applied), Wright Field decided to try fuelinjected engines on the P-26A. Consequently, the first two P-26A's in the second production lot were ordered to be completed with the injected engines. The new engine was the R-1340-33 which, since it was appreciably heavier Gust over 100 pounds) than the carburetor-equipped -27, caused ballast to be added to the tail to maintain proper c.g. requirements. Because of the extensive system and weight changes involved, the Air Corps redesignated the R-1340-33-equipped aircraft P-26B and Boeing consequently assigned a revised'model number, 266A. The engine change and the addition of the flaps raised the unit cost of the two P-26B's to $14,009, less GFE. The first P-26B, 33-179, was flown to Wright Field for test

on June 20, 1935. The second, 33-180, was flown to Selfridge Field on June 21 st, where it became the personal mount of Lt. Col. Ralph Royce, Commanding Officer of the1 st Pursuit Group. P-26C: The remaining 23 aircraft, still with the original -27 engines, were redesignated P"26C under a Change Order issued in February of 1936, to indicate the fact that they had flaps and other minor changes as factory installed items. The Boeing Model number remained 266. Later, when the Army decided to refit all the surviving P-26C's with the fuel injected -33 engines, the designation changed to P-26B (a rare case of a designation reverting to an earlier designator). The last flyable P-26B, 33-197, converted from a P-26C, was relegated to Class 26 (non-flying) duty on October 22, 1942, with a total of 1,261 airframe hours. Since the P-26B's and P-26C's were additional articles on the original contract, the increased quantity reduced the basic unit price by $500. The flaps and engine changes were additional costs above the unit price. The first delivery of a P-26C was on February 10, 1936, and the last was on March 7. All were flown to the 1st Pursuit Group at Selfridge Field. All but six, 33-190, -193, -196, -198, -201, and -202 (which had been attrited by mid-1937), were converted to the P-26B configuration at the Fairtield Air Depot later in 1937. The high-time P-26Cto-B conversion, 33-183, had 1,952 flight hours. Based at Wheeler Field, Hawaii, it survived Pearl Harbor and continued to fly until it was surveyed on May 13, 1942. RP-26: The RP-26 designation was the result of an October 22, 1942 decision to put certain obsolescent combat aircraft in a new Restricted category that prevented them from being used for their designated mission, in this case, Pursuit. The designation applied primarily to the few P-26A's that remained in squadron service in the Canal Zone. ZP-26: The ZP-26 designator was the result of a December 11, 1942 Army declaration that surviving P-26A's were too old to qualify for the RP designation. In so doing, the aircraft were declared obsolete and designated ZP-26A, accordingly. This was a long establised designation that had been applied to many obsolete tactical types that still had useful lives as testbeds, squadron hacks and other miscellanea. Unlike the products of most other aircraft manufacturers, P-26's did not simply roll out the Boeing factory door, taxi out to a runway, and flyaway to their assigned post. To the contrary, the original Boeing factory (Plant 1 after 1936) was a former yacht works on the west side of the Duwamish River south of Seattle that had no adjacent flying field. The P-26's were built in a WW1 addition to this plant, and then trucked in a disassembled state to Boeing Field on the King County Airport located on the east side of the river some two miles away. There, final assembly was undertaken in a large brick hanger leased from the county. Flight testing, consisting of three hours of shakedown flying by Army service pilots, was conducted from the airport runway facilities. Delivery to their assigned units, the 20th, 17th, and 1st Pursuit Groups (in that order), took place direct from Boeing Field (export Model 281 's were crated at the factory for surface shipment; from 1937 on, P-26's reassigned to overseas bases were disassembled, crated, and shipped by the Army).

Boeing Model 281 (Export): In a further break with precedent, the Army allowed Boeing to sell export versions of the P-26A before that model had been in Army service for five years. Though unstated at the time, this decision also served to confirm that the P-26 was strictly an interim design. Except for minor departures from HIAD requirements and different equipment details, the Model 281 was identical to the P-26A. The Model 281 was the end result of an in-house decision on the part of Boeing management to attempt to penetrate the small but potentially lucrative export market. Sufficient interest on the part of the Chinese Central Government of Chiang Kai-shek led to a commitment by Boeing to utilize company funds for production of additional aircraft over and above those required by the Army Air Corps. The first Model 281, painted Army olive drab and chrome yellow, but"carrying the civil registration X12271 and cln 1959, flew for the firsnime on August 2, 1934. Shortly afterwards, it was modified by Boeing to test the wing trailing edge flaps that were later retrofitted to the P-26A's. B~ing also tested a set of revised, open well wheel fairings, or "pants", on the demonstrator that allowed the alternate installation of low-pressure Goodyear Airwhee/s. The latter were incorporated in the Model 281 in order to accommodate the rough field re-

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BOEING MODEL 224

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Main fuselage bulkheads of the first XP-936 are seen aligned in the primary assembly jig during the initial stages of construction. Drafters and engineers worked side by side with the aircraft as it was built. Photo was taken on February 2, 1932.

~ ;;" _ l~ A P-26A fuselage is seen in its construction jig immediately prior to the application of external skin. Noteworthy are the fuselage formers, bulkheads, and stringers. Also note complex jig assembly for positioning and forming tail wheel cut-out.

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Taken in September of 1933, left side-view of P-26A fuselage is seen following application of skin and prior to attachment of wings, engine and engine mount, tail surfaces, landing gear, and headrest assembly. Large cutout for tail wheel is particularly distinctive. 3

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Front view illustrating the first Boeing Model 248, identified as the first of three XP-936's (Boeing cln 1678) by the US Army Air Corps. The photo was taken at roll-out on March 17, 1932, at Boeing Field. Note location of pitot boom on left wing.

quirements expected to emanate from export sales. Twelve Model.281's were built, with two, X12271 and X12275, being used as demonstrators. X12271 was disassembled and shipped to China on September 15th, but was soon destroyed in a flight demonstration accident. Fortunately, with the exception of the accident, the initial parts of the demonstration had gone well and had left the Chinese with a positive impression. Accordingly, ten production Model 281's, cln's 1960, 1961, and 1965/1972 were ordered by the Chinese government and paid for mostly with funds raised by solicitation boxes in Chinese restaurants in the US. Deliveries of the Chinese aircraft began on December 12, 1935, and were completed on January 5, 1936 Gust before P-26C deliveries began). As shipped to the Chinese, the Model 281's were painted over-all light gray, with the blue and white Chinese 12-point star only on the undersurfaces of the wings. Later, they were repainted over-all olive drab and more complete markings were applied. The ten Model 281's saw light but significant action against the Japanese in the Nanking area, where they were based at Chuying airfield. Japanese efforts to penetrate south toward Nanking led to the city becoming a primary tamet for G3M2 bombers of the Kanoya Kokutai which by then were operating out of Taipei, Taiwan. On August 20, 1937, six G3M2's were destroyed in the ensuing air battle, with only one Model 281 receiv-

ing relatively minor damage. Unfortunately, spares shortages, accidents, and poor maintenance qUickly ended the Model 281 's r61e in the events leading to WW2. By the lime Nanking fell to the Japanese on December 13,1937, none of the Chinese Model 281's were still flyable. The second Model 281, X12275, cln 1962, was delivered to Barajas airfield, near Madrid, Spain on April 10, 1935, for demonstration to the Aviacio'n Militar under the direction of Direccio'n General de Aerona'utica. There, with company test pilot Les Tower and Boeing Vice President Erik Nelson overseeing reassembly, the aircraft was made ready for its flight demonstration. Though they were impressed with the performance of the Model 281, the Spanish government refused to buy the type in quantity. The unit price of Pts. 500,000 was considered too expensive for an already stretched Spanish military budget. The single Model 281 demonstrator was bought, however, with the idea of studying its design for potential application to indigenous fighter aircraft development. The Model 281 had been delivered to Spain only minimally equipped. It mounted no guns and there was no sychronizer gear on the engine. Later, the Spanish Air Force installed two British Vickers machine guns in underwing pods outboard of the propeller arc and integrated the aircraft into a mixed complement Republican

Twenty-six partially completed P-26A's are visible in this photo taken inside Boeing's production facility in March of 1934.

fighter unit. It was later shot down over Getafe by Rebel aircraft on October 21, 1936.

MODIFICATIONS: As with all high-performance military aircraft, P-26's were subject to a number of post-delivery modifications of both minor and major importance. The principal ones consisted of the following: Headrest: A Barksdale Field pi lot, Lt. Frederick I. Patrick, was killed during a forced landing on a routine cross-country flight on February 22, 1934. Though the plane, 33-46, flipped onto its back without major structural damage, the headrest sheared off following the flipover and Patrick's neck was broken. This accident resulted in the February 27th grounding of the entire 28-plane P-26A fleet until a fix could be developed. Since this was the first P-26A to crash, it was sent to Wright Field for study and the fuselage was used to static-test a new headrest. Boeing and Wright Field worked together to develop a new higher (8") headrest with substantial inner structure that could resist a 27,600 lb. vertical load, 13,000 lb. forward load, and a 7,080 lb. side load. Boeing installed the first new headrest on 33-56, which had yet to be delivered. Aircraft still at the factory were modified there. with deliveries resuming on March 27th. The others were modified at Army bases. All work on the headrest

Roll-out day shot of first XP-936. Aircraft had olive drab fuselage with yellow wings and tail surfaces. Vertical fin stripe w~sblue, and rudder stripes were red and white. Short headrest and fairing are particularly noticeable in this view when compared to the late P-26A configuratIOn. Also dlstmctlve IS the excessive bafflmg VISible on the nose cowling.

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modifications was completed by May 21st. Stabilizer Gravel Deflectors: Although they looked like the well-known black rubber de-icer boots, the sheet rubber covering on the lower leading edge of the horizontal stabilzer was there to prevent gravel kicked up by the propeller slipstream and the wheels from denting the sheet metal skin. Because of the rubber, the unique scalloped paint scheme of the 17th Pursuit Group was not applied to the underside of the stabilizer. Wing Flaps: The Army was unhappy with the high 82 mph landing speed of the P-26A. Consequently, both the government and Boeing developed flaps for retrofit to existing P-26A's. The National Advisory Committee for Aeronautics (NACA) designed four different sets and tried them as simple plywood structures wired onto P-26A 33-56 which was mounted in the full-scale wind tunnel at Langley Field, Virginia. Wright Field then built what proved to be the least desireable of the four, a one piece unit that crossed the fuselage from aileron to aileron and had a deep bow in the middle to conform to the fuselage underside when retracted. This was installed on 33-28, which soon crashed fol' the reasons the NACA had said it would-blanking of the airflow to the tail at low (landing) speed. A further disadvantage of the one-piece flap was that it precluded installation of the belly bomb rack. The Boeing flaps, which were handcranked down to a 45-deg. deployment angle, were more complex and expensive than the NACA-developed units in that they were recessed into the underside of the wing. They were in four sections, with the ouler ones overlapping the inner ends of the ailerons. Boeing tested them on the first Model 281 (foreign sales P-26), and then sent the aircraft to Wright Field for Army trials. The Army accepted the Boeing design, which reduced the landing speed to 73 mph, and starting in the spring of 1935, cycled the entire P-26A fleet through Boeing's Seattle facility for the Boeing flap retrofit. The 17th Pursuit Group from March Field, just redesignated an Attack Group and giVing up its P-26's, was the first to send its P·26's to Boeing, and these aircraft, when their respective retrofit was completed, were then distributed to the 1st and 20th Pursuit Groups. P-26's of the 20th Pursuit Group were retrofitted next, followed by the 1st. All P·26A's were fitted with the new flaps by the fall of 1935. Pitot Tube: The pitot tube of early production P-26A's, mounted on the right wing (the XP-936 had its pitot tube mounted on the left Wing), was found to oscillate in flight. An interim measure in which these tubes were shortened produced a constantly increasing airspeed error which read up to 13 mph low at 200 mph. The tube was eventually replaced with a more rigid, interim length design. Engine Change: As noted later, the 19 surviving P·26C's were refitted with R-1340-33 fuel-injected engines in 1937 and were redesignated P-26B. An easy recognition point was elimination of the two air intakes for the downdraft carburetor located on the top of the fuselage, just behind the engine. Exhaust Stacks: Pilots complained about glare from the short upper exhaust stacks during night flying, so, starting in October of 1935, the exhaust from cylinders 1, 2, and 9 was fed into a single collector stack that discharged on the right side of the nose just above the stack for cylinder 8. The other stacks remained single. New Tail Wheel: In 1936, Boeing developed a new tail wheel assembly that featured a smaller wheel with an oleo-pneumatic shock absorber that projected well below the fuselage instead of being nested in it. The new style was adopted in May by the Army and was installed in the P-26 fleet at Army depots. Fuselage Reinforcement: Midway through the P-26's service career skin wrinkles were detected on the fuselage midway between the cockpit and tail. Starting in 1935, it became necessary to remove some skin to perform an internal reinforcement modification. Evidence of this repair in the form of fresh paint is visible in some photographs.

OPERATIONAL PROBLEMS: The P-26 fleet had its share of accidents. The rate was not significantly greater than for other Air Corps models, but for some reason the airplane seemed to get more than its fair share of publicity. The narrow landing gear, cQl.lpled with the P-26's high center of gravity, troublesome mechanical brakes, and "soft" shock absorbers, was responsible for many ground accidents. If the pilot hit the brakes too hard, or if one brake locked or faded during application, the aircraft could easily flip onto its back. If one shock absorber depressed too far on a cross-wind landing roll, the wind could get under the high wing and cause a ground loop that could also easily lead to a nose-over.

The first XP-936 is seen with uncovered P-26A landing gear, the late P-26A headrest, and the original olive drab fuselage color changed to blue. The photo was taken on August 2, 1936, at the Allegheny Country Airport.

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In spite of Army coloring and markings, all three XP-936's were Baing-owned when tested by the Army under a bailment contract. This is the seldom-seen XP-936 No.2, photographed at Anacostia NAS on June 1, 1932.

The No. 3 XP-936 is seen during tests at Wright Field still with the early headrest and an over-all olive drab paint scheme. The pilot is wearing a standard seat-pack type parachute and is holding the small cockpit hatch that facilitated ingress and egress. Other accidents resulted from ordnance and equipcraft previously assigned to Barksdale Field and 12 ment. On several occasions, for instance, flares on the previously assigned to Selfridge Field. These equipped belly bomb rack ignited and set the airplane on fire. On the 3rd Pursuit Squadron which eventually flew the P-26 other occasions, pilot mismanagement of the fuel for no less than five years while successively operating system, or unpredictable system failures, resulted in out of Clark, Nichols, and Iba Fields. Additional P-26's engine stoppage and subsequent forced landings. Such were eventually assigned to the 3rd in order to make up landings, often taking place on unsuitable surfaces, for attrited aircraft, and a surplus led to the re-equipping made nosing-over almost inevitable. of the 17th Pursuit Squadron with some of its original OPERATIONS: P-26's when it arrived on Nichols Field in late 1940. In the Philippines, 12 P-26A's were transferred to the With a few exceptions, all of the P-26's were delivered from the factory to the operating squadrons of the three Philippine Army Air Force starting in .July of 1941. These stateside pursuit groups, the 1st, 17th, and 20th. As aircraft were utilized to form the 6th Pursuit Squadron these premier .organizations acquired later equipment, at Batangas Field, and on December 10th, entered combat when a number of Mitsubishi Zero-Sen fighters made their P-26's were passed on to other groups as indicated in the accompanying chart. No P-26's were sent out of an initial strafing attack on Zablan Field. Further comthe country until the spring of 1937, and then only to bat ensued during the following two weeks, with at least Hawaii, the Philippines, and the Canal Zone. Some'pura half dozen P-26's getting involved in air combat with suit groups activated as late as 1940 were provided with Zero-Sen fighters and G3M bombers. Though hopelessIy outclassed by the more modern Japanese aircraft, the obsolete P-26's as initial equipment. It should be noted that after 1938, few squadrons having P-26's were fUllyP-26's miraculously managed to score several victories equipped with that model alone. before the Japanese landed in force at Limon Bay on The first overseas deployment of the P-26 took place December 24th. An order to burn the remaining P-26's in the spring of 1937 with the arrival, at Clark Field, of the 6th Pursuit Squadron, though later rescinded, was unfortunately carried through, and accordingly, all reLuzon, the Philippines, of 14 P-26's that included 2 air-

5

maining aircraft were destroyed. During 1938, P-26's were assigned to Wheeler Field, Hawaii, and Albrook Field, Panama Canal Zone. No less than 42 P-26's were sent to Hawaii to equip the 18th Pursuit Group (6th and 19th Pursuit Squadrons), though some 20 of these were later reassigned to the Philippines during late 1938 and early 1939. As the P-26's entered service in Hawaii, additional aircraft were being assigned to Aibrook Field in the Panama Canal Zone where they equipped the 16th Pursuit Group (24th and 29th Pursuit Squadrons). These aircraft provided the primary Canal air cover until supplanted by Curtiss P-36A's in 1940. Eleven P-26A's remained in the Panama Canal Zone in 1940, and most of these were eventually transferred to a US Army organization known as the Panama Canal Department Air Force (often referred to as the Panama Air Force) which, in turn, sold some of them to Guatemala for use by the Cuerpo de Aeronautica Militar. These aircraft were suppiemented by an additional four P-26A's which were acquired directly from the Air Corps. Guatemalan P-26's were reassigned to the Escuadro'n de Caza at Camp de la Aurora, Ciudad de Guatemala and utilized as front line fighters and advanced trainers for most of their Guatemalan careers. At the time of the Pearl Harbor debacle, there were only four P-26's left in the continental US. Additionally, there were seven in Panama, eight in Hawaii, and six still in US service in the Philippines. Altogether, 31 P-26A's and 14 converted P-26B's were sent to Hawaii, 34 P-26A's to the Philippines, and 26 P-26A's to Panama. The service career of the P-26A in Air Corps service spanned just under a decade. The last flyable example in US Army service, 33-89, was transferred to the Guatemalan Air Force from Albrook Field, Canal Zone, on May 4,1943, with 2,302 flying hours in its log books. The high-time US Army P-26A was 33-122. Unfortunately, it was written off following an accident in Panama in June of 1942 with some 2,550 hours logged.

The following is a complete listing of all P-26A/B/C US Army Air Corps unit assignments: GROUP

SQUADRON

1st Pursuit

P·26 YEARS '37·'38 '34·'35 '37·'38

STATION

'38·'41 '40·'41 '40·'41 '38-'39 '40-'41 '41 '41 '39 '34-'35 '34·'35 '34·'35 '41 '38·'41 '41 '41 '40 '34·'38 '34·'38 '35·'38 '40 '40 '40

Selfridge Selfridge Selfridge Selfridge Nichols PI Nichols. PI Nichols. Clark PI Canal Zone Wheeler TH Wheeler TH Wheeler TH Canal Zone March March March Wheeler TH Wheeler TH Wheeler TH Wheeler TH Wheeler TH Barksdale Barksdale Barksdale Selfridge Selfridge Bolling

'41 '41 '40-'41 '40·'41 '40-'42 '34·'36

Canal Zone Canal Zone Canal Zone Canal Zone Canal Zone Bolling

Air Corps Technical School

'34·'37

Chanute

MaterIel Division

'33-'40

Wright

17th

27th

4th Composite

15th Pursuit

16th Pursuit 17th Pursuit (to 17th Attack Group 3-1·35) 18th Pursuit

94th 3rd 17th 20th 29th 45th

46th 47th 24th 341h 73rd 95th 61h

19th

20th Pursuit

44th 73rd 78lh 55th 77th

79th 31st Pursuit

39th 40th 41st

32nd Pursuit

51st 53rd 28th 30th 31st

37th Pursuit

Bolling Field Air Corps Detachment

'34·'38

Notes: (1) fransferred as a new 17th P.S. with the same insignia to Philippines and re-equipped with P-26's and P-35's. (2)Activated in February of 1940 in 35th P.G. at Moffett Field with P-36A's. Transferred to the Philippines and given P-26's and P-35A's.

REPLACED NOTES BY (1) P·6E P-35 P-16 PB-2A PB-2A P-35 P-6E P-35 P-12E P-40B Mixed w/P-35A's on transfer from 1st PG Mixed w/P-35A's (2) P-12E P·36A Mixed wfP-36A's P-36A Activated 1211140 (3) P-40 Activated 12/1/40 (4) P-12E P-36A P-12E P-12E P-12E P-12E P-12E P-12E P-12EIF P-40 P-12E Activated 10/4/41 P-36A (5) Activated 1/1141 P-40 new squadron P-40 P-12E P-36A P-12E P·36A P-12E P·36A P-12E P·36A Activa!ed 2/1/40 Mix w/P-35 P-39 Mix w/P-35 Activated 2/1140 P-39 Mix w/P-35 To Selfridge P-39 11140 Initial Equipment P-36A Activated 1/1141 Initial Equipment P-36A Activated 1/1/41 Initial Equipment P-40 Activated 2/1/40 Initial Equipment P-40 Activated 2/1140 Initial Equipment P-40 Activated 2/1140 33-56,33-57,33-77 mixed wlother models

REPLACED

Mixed w/other models 33-28,33-48,33-52.33-56,33-179; 33-179 wlo 6/20/40; 33-78 trans. to Wright Field 717/40 and wlo 12113/40

(3) 1 P-26 with P-40·s. (4) 1 P-26 with P-36A's. (5) 2 P-26's with P-40's.

P·26A/B/C OVERVIEW:

A P-26A is seen in conventional markings at an unidentified airfield in New York on March 15, 1934. In this view the height of the modified headrest is readily apparent.

Clean P-26A warms up for mission. Aircraft has extended headrest and fairing and is apparently painted in conventional scheme of olive drab with yellow wings.

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A line-up of P-26A 's with the first aircraft providing a view of the Boeing-designed flaps in their extended position.

6

This P-26A lacks the forward cowling-mounted radio antenna mast that is so prominent on most "Peashooters". Vertical fin antenna mast is visible.

BASIC MARKINGS: Four basic US Army color schemes were used during the P-26's service career. As originally buill, they all had chrome yellow wings and tail surfaces with olive drab (o.d.) fuselages and landing gear. In May of 1934, a Technical Order was issued calling for the replacement of the o.d. with a shade called Light Blue. The latter was actually a medium blue and because the change was not required to be immediate, manufacturers were permitted to consume existing stocks of o.d. paint before changing to the new color. Although P-26C's were delivered as late as March of 1936, no Boeing employee can recall ever having seen a blue-painted aircraft in the factory. In 1938, with many newall-metal aircraft entering service in natural metal finish, over-all silver was decreed as the standard coloring for tactical aircraft. Some older blue and yellow models still in service were repainted at squadron level. Again, there was no hurry, and relatively few P-26's found their way into silver paint. Starting in February of 1941, tactical aircraft in the squadrons were repainted in o.d. on their top and side surfaces and with light gray undersurfaces. The old Army tail stripes were deleted, as were the upper right and lower left wing stars. Additionally, a star was added to each side of the fuselage. Very few of the P-26's still in service at that time were given the new arrangement. Some in the Philippines were still in silver or even blue and yellow after the Japanese attack on December 8, 1941 (the date in the Philippines).

INDIVIDUAL AND UNIT MARKINGS: Most P-26's in squadrons or special organizations carried that organization's insigne on each side of the fuselage. Aircraft attached to group headquarters carried group insigne. A notable exception, from 1934 to 1939, was the 20th Pursuit Group. All three 20th PG squadrons carried group rather than squadron insigne. Individual aircraft were numbered separately within the group. The 1st Pursuit Group had a unique system; the last two digits of t~e Air Corps serial number were painted on the vertical fin and engine cowling of its P-26's. The P-26's of the 17th Pursuit Group were numbered 1-18 for the 34th Squadron, 32-60 (with gaps) for the 73rd, and 61-90 for the 95th. Group headquarters aircraft were 100-103 and the Wing Commander's aircraft was 00. Confusion exists from the fact that former 17th Pursuit Group P-26A's which went to the 1st and 20th Groups retained their original 17th P.G. color schemes but got new identification numbers in their new groups. The P-26A's of the 20th Pursuit Group were first identified by big white block numbers 0-48 on the fuselage. These were changed to black numbers on the fin and upper left wing in 1935. Usually, but not always, the last two digits of the serial number were preceded by the number 1 for individual aircraft identification. Other groups that had hand-me-down P-26's used more arbitrary tail numbers. From 1938 into 1940, the system changed. Groups were identified as to type and number by letters, as PT for the 20th Pursuit Group, T being the 20th letter of the alphabet. The aircraft number was carried below the letters on the fin and following them on the upper left wing, now for all groups. In 1940, the system was revised to use the actual group number, as 18P for the 18th P.G. This time the aircraft number was above the group identification on the fin. The 18th P.G. in Hawaii misapplied the new designator as 18 PG instead of 18 P. Application of squadron colors, leader stripes, etc., was not standardized for most of the P-26 era and cannot be detailed nere. Some comments on this subject, however, appear in the photo captions.

Top view of the first production P-26A, 33-28, taken on delivery day, December 16, 1933, at Boeing Field. Revised elliptical wing shape is particularly noticeable. Panchromatic film gives light-color accent to yellowpainted wings and tail surfaces.

Other not.able differences between the P-26A (Boeing Model 266) and the XP-936 were revised landing gear fairings, a pitot mast on the right wing (instead of the left), a higher headrest, and flush instead of brazier-head rivets. Aircraft 33-28, shown, had antenna masts installed, but no radio.

THE SURVIVORS: Two of the Guatemalan P-26A's, 33-123 and 33-135, were still intact in 1957. Both were eventually retrieved for display in the US and are currently displayed in the colorful markings of the 34th Pursuit Squadron of the 17th Pursuit Group (though neither airplane is known to have served with the 17th PG). P-26A, 33-123 was first delivered to the 94th Pursuit Squadron at Selfridge Field on June 20th, 1934, and was marked as Plane No. 23. It was soon transferred to Group Headquarters and flown with group, rathQl' than squadron insigne. A nose-over accident occurred in September of 1934, and repair was undertaken at Fairfield Air Intermediate Depot. In August of 1938, it was sent to the San Antonio Air Depot for a major overhaul, and from there, it went to Rockwell Field, San Diego, for disassembly and shipment to the Canal Zone. It was retired from Albrook Field, CZ, in August of

The first P-26A, 33-28, at Wright Field, displaying the Wright Field arrow insignia on the fuselage. Panchromatic film has caused darkening of yellow wings and red and blue tail markings.

7

Another view of 33-28 at Wright Field. Again, orthochromatic film has caused darkening of the yellow wings and red and blue tail markings. Note that both wings had Air Corps star.

1943, after logging some 2,454 flying hours. From Albrook Field it was transferred to Guatemala. In 1957, it was acquired by Edward T. Maloney of California, who brought the airplane back to California for display in his new aviation museum which was then located near Claremont, California (the museum has since moved to Chino, California). After several years of static display it was restored to flying condition and painted in the 34th Pursuit Squadron markings (but with its correct 1st Pursuit Group Number 23). F(}jlowing restoration, it took to the air for the first time on September 17,1962. Flown occasionally since, it is presently the only flyable P-26 in the world. The fuselage is painted blue (which no 17th Pursuit Group P-26 ever was). The only other surviving P-26, 33-135, was delivered to the 94th Pursuit Squadron at Selfridge Field on June 27th, 1934, and was marked No. 35. After an accidentfree career, it too was sent to San Antonio for overhaul and to Rockwell for disassembly and shipment, in September of 1938, to Panama. It was sold to Guatemala in August of 1942, having logged 2,552 flight hours, and was acquired by the Smithsonian Institution shortly after Maloney acquired 33-123. It was then placed' on longterm loan to the AF Museum, which restored it as NO.7 of the 34th Pursuit Squadron. Accurately painted with an olive drab fuselage, 33-135 was displayed at the AF Museum from 1959 thru 1975. It is now hanging in the National Air & Space Museum in Washington, D.C.

CONSTRUCTION AND SYSTEMS: Five P-26A's are seen lined up on Boeing Field in June of 1934. These aircraft have the new high headrest but no radio masts. All P-26A's were flown away without radios. Note the variety of flying clothes being worn by the Air Corps ferry pilots.

The first P-26B, rolled out on June 29, 1935, was identical to the P-26A except for the addition of wing flaps and the change to a fuel-injected engine. Visible in this view are the split flap sections.

Three-quarter rear view of the first P-26B. The vertical fin, horizontal stabilizers, elevators, and wings were painted yellow. The fuselage was olive drab and the rudder was red and white with a large vertical bar of blue.

8

As the Army's first all-metal pursuit aircraft, the P-26 series utilized structure developed by Boeing on its earlier Model 96/XP-9, the Model 200 and 221 Monomail singleengine transports, and the Model 214 and 215 (which became the Army's B-9 bomber). Design experience in this new area remained limited and accordingly, the structure was not only very conservative, but was also highly redundant and considerably overweight. The fuselage was a semi-monocoque structure with load carrying aluminum skins flush riveted to six main bulkheads and 13 intermediate formers. These formers and the interconnecting longitudinal members were rolled to a hat-section from flat aluminum sheet. The fuselage cross-section was roughly tear-shaped at the front, changing to a nearly oval shape at the tail. It was necessary to install a small hinge-down door to simplify pilot access. Because there were no straight lines to the P-26 fuselage, the sheet aluminum skins could not be put on in large flat-wrapped sheets. Instead, the skin was put on in long narrow longitudinal strips, starting at the bottom with the higher skins overlapping shingle-fashion. The tighter curves of the nose ahead of the firewall were formed on hydropress dies. The engine mount was a separate removable steel tube frame that was bolted to the No. 1 bulkhead. Rubber bushings in the forward mounting ring dampened engine vibration. The required design loads for the fuselage were 12.0 positive and 8.5 negative, and the XP-936 passed these with 13.39 and 9.5, respectively. The static testing was not carried to the point of destruction because it was desired to save the fuselage for other tests. The wing, which utilized a Boeing 109 airfoil, was built in three sections consisting of two removable outer panels and an integral stub center section to which the landing gear was attached. The wings used two main spar assemblies built up of flat sheet aluminum and riveted-on flanges. Ribs were built up of rolled hat sections and short aluminum tubes with their ends flattened for riveting. The wings were covered with sheet aluminum riveted in place. Brazer-head rivets were used on the Model 248/XP-936 and flush rivets were used on all other models. Wing design loads were 12.0 positive and 4.0 negative. At the high angle of attack condition, the wing passed without failure. In the inverted position, it was overloaded by 25% to a factor of 5.0 without failure. The flying wires tested from 13.0 to 14.25 before failure. The cantilever fin and horizontal stabilizer used a semblance of the traditional spar-and-rib construction technique. There was a hinge-line spar of aluminum channel and a similar diagonal spar. These were connected by four traditional ribs. Other ribs ahead of the diagonal formed the leading edge. Each structure was covered with sheet aluminum. There was no fixed leading edge structural member; the upper and lower skins were flanged aDd flush-riveted to each other. The ribs served mainly as spacers for the skins rather than as traditional

compression members. Except for use of smooth instead of corrugated skins, this detail was a direct inheritance from earlier Boeing pursuits and fighters dating back to the Navy F3B-1 of 1927. In spite of redundant structure, the horizontal stabilizer did not test well, showing impending failure at 90% of the design load of 253 lbs. per sq. foot. Reinforcement was added in order to meet the load requirement and the unit eventually passed the test. The vertical fin withstood 130% of the 189.6 lbs. per sq. foot design load without failure. The elevators, rudder, and ailerons differed notably from the fixed surfaces. Each had a channel spar at the hinge line but the ribs were pressed aluminum diagonals that again served mainly as spacers for top and bottom skins that were riveted to each other at the trailing edges, again an element inherited from earlier Boeing designs. The elevators had a Handley Page balance area ahead of the hinge line (inherited from preceding Boeing pursuits such as the P-12B/F4B-2 and on). The ailerons were similar in design, but were of the Frieze type wherein a portion of the upward moving aileron projected below the lower surface of the wing to add drag on the inside of the turn and reduce "adverse yaw" phenomenon. Each elevator was fitted with a trailing edge tab that was controlled from the cockpit to correct the longitudinal trim-a first for a production American aircraft. It had been developed in Europe and Boeing pioneered its use in the US. The tab was irreversible under air load, being actuated by a screw. Displacing the tab upward caused the airstream to deflect the elevator downward, thereby trimming the aircraft nose-down. Previously, longitUdinal trim had been obtained at the cost of mechanical complexity by rotating the entire horizontal stabilizer about the rear spar line. Trim for both ailerons was by means of fixed sheet aluminum tabs extending beyond the trailing edge and adjusted by hand on the ground. A similar rudder tab was added to the P-26A later. The landing gear was a complex structure consisting of a rigid V-frame connected to both wing root spars and anchoring the flying wires at the iower point. Shock absorption was by means of a Boeing-built oleo-pneumatic shock strut pivoted at the toplfront spar junction, and held forward of the low point of the rigid "V" by a pivoting arm. On the XP-936, each wheel was mounted in a fork, which required removal of the axle in order to remove a wheel or change a tire. This was soon replaced by a mislabelled "single leg" unit that secured only the inboard end of the axle, allowing the wheel to be slipped off easily. Since the wire braced system was unstable with the wing wires slacked off or removed, it was necessary to install a spreader bar between the two landing gear units and keep the inboard crossed wires tight. Braking was mechanical land actuation was by toe action· at the top of the rudder pedals. For parking, the brakes were locked by means of a handle on the pilot's auxiliary instrument panel. Streamlining involved spacers between the arms of the "V" to support aluminum skins. The upper portion of the shock strut was covered by wraparound sheet aluminum fastened to the V-leg, but the formed wheel pants were attached to the shock strut and moved with it. Spacing from the fixed fairing was maintained by rub strips. It became common practice in some squadron operations

to remove the outboard side paneis of the multi-sectioned "pants" for flight. Armament was the Air Corps standard of two .30 caliber Browning machine guns firing through the propeller, each with 500 rounds of ammunition, or one .30 caliber M-2 on the left side of the cockpit floor and one .50 caliber M-2 with 200 rounds on the right. The guns were modified so that the left-hand gun was fed from its right side while the right-hand gun was fed from the left. Ammunition boxes were underneath the floor ahead of the 55-gallon fuel tank. The guns were charged by pullcables with T-handles at each side of the pilot's seat back. The electrical firing circuit was controlled by a selector switch on the pilot's aUXiliary panel. Ammunition counters for each gun were on the same panel. The single gun trigger was built into the forward side of the control stick grip. A type C-3 gun sight was mounted ahead of the windshield and a type G-4 camera gun could be installed on the top of the right-side wing stub. Power for the camera gun was provided by two dry batteries carried in the rightside ammunition box. A standard Air Corps Type A-3 bomb rack, capable of holding two 100 lb. demolition bombs, five 3D-lb. fragmentation bombs, or two parachute flares, was installed under the belly. Two-way voice radio was just coming into use when the P-26A's entered service. The standard radio was the low-frequency SCR-( )-183 radio. The letters SCR identify Signal Corps Radio and the blank parenthesis are filled by letters indicating the particular manufacturer of the set or component. The BC-( )-180 transmitter was located on the cockpit floor ahead of the control stick and beneath the auxiliary panel. The control box was on the left side of the cockpit above the throttle. The SCR-( )-192 receiver was in the baggage compartment on the right side of the bulkhead. The tuning controls were on the right side of the cockpit opposite the transmitter control. There were two separate antenna. A mast ahead of the windshield supported transmitter wires running to each wingtip. A short mast on the top of the vertical fin supported the longitudinal receiver antenna wire. Only provision for radio equipment was made at the factory; radio was installed by Army personnel at squadron level. The P-26 was a pioneer in the use of a liquid oxygen system for high-altitude work. A Type B-11 vaporizer and storage bottle were mounted on the backside of the cockpit rear bulkhead, to the left of the zippered canvas baggage compartment. An access door in the side of the fuselage made it possible to service the system with the vaporizer and storage bottle in place. The pressure gauge and adjusting needle valve were clamped to the right edge of the pilot's instrument panel. After P-26A deliveries began, the Army decided that emergency flotation gear was desireable. Aircraft 33-52 was then pulled from the inventory to serve as a testbed and accordingly, two bags were installed in streamlined aluminum "slippers" attached to the upper surface of each wing stub. The carbon dioxide bottle was installed to the left of the pilot's seat and actuated by a cable and T-handle in the left rear corner of the cockpit. An emergency hand pump was carried in the headrest. It was necessary to contour the bags to fit around the landing wires above the wing. All P-26's from 33-53 and on had provisions for flotation gear built in at the factory.

------

-

A P-26B sits on the ramp at Boeing Field. This aircraft does not have an antenna mast and appears to be seen prior to delivery.

Earlier aircraft from 33-28 thru 33-51, were not retrofitted. Because of the externai "bolt-on" nature of the flotation system, problems of being stepped on, and interference with the camera and gun installation, the flotation bags were seldom installed. At least one P-26A was lost when one of the flotation bags came open in flight.

POWERPLANT: In choosing an engine for the P-26, Boeing selected one that it had been using in pursuit and fighter aircraft since 1926. The Pratt & Whitney R-1340 Wasp had long held a reputation for dependability and ruggedness, and though it was not a state-of-the-art design, it \'las nonethe-less determined to be suitable for Boeing's new pursuit by the company powerplant staff. The R-1340 (R = radial; 1340 = piston displacement to the nearest five cubic inches) was a nine-cylinder, aircooled radial rated at 550 hp. More powerful, but also larger and heavier engines were available, but were not suited to the design concept of the P-26. The competing Curtiss XP-934 Swift, for instance, started with a 700 hp Wright R-1820F Cyclone air-cooled radial, but shortly afterward, had it replaced by an older 600 hp Curtiss V-1570 Conqueror liquid-cooied V-12. The Wasp was designed by engineers who had left the old Wright Aeronautical Corporation to design a better air-cooled radial. They received initial encouragement and orders from the US Navy, which saw and quickly appreciated the weight-saving and reliability advantages of conventionai air cooling. Throughout the 1920's and into the early 1930's, service engines were identified by the makers' designation such as R-1340B, 1340C, etc. The addition of a supercharger would be indicated by a prefixing S, such as SR-1340D. The XP-936 in fact used the SR-1340E, which delivered 522 hp at 2,200 rpm at 10,000 feet through a two-blad·e ground-adjustable fixed-pitch propeller. By the time the P-26A entered service in 1934, the Army and Navy had adopted a new system separate from the manufacturers'. The basic type and displacement figures were retained, but the stage of development was identified by sequential dash numbers with "even numbers" being set aside for Navy engines and "odd numbers" being set aside for Army. The P-26A's and C's used the R-134D-27. Interestingly, though this engine was supercharged, it did not incorporate the S-prefix in its designator. The P-26B used the R-1340-33, which had direct fuel injection instead of carburetors and a new control lever in the cockpit that COmbined the functions of throttle and mixture control into one unit. Fore-and-aft movement controlled the throttle, while rotation of the knob enriched (counter-clockwise) or leaned (clockwise) the mixture. Because of the altitUde supercharging, the engines in the P-26's were limited to less than full power below 6,000 feet by a throttle stop. Sea-level output of the R-1340-27 (P&W's R-1340-S2E) was 500 hp at 2,200 rpm for takeoff, . and 570 hp at 2,200 rpm at 7,500 fee.t. The engine was equipped with an inertia starter cranked by hand or with a powered flexible shaft engaging a drive on the left side of the nose. The "engage" handle was in the cockpit to the left of the instrument panel. In the P-26's, the engine was enclosed in a Boeing varia-

The twenty-three P-26C's were identical to the P-26A's except for minor equipment differences and the fact that they were built with flaps. This one is seen outside the Boeing factory in early 1936.

9

tion of a Townend "anti-drag" ring and the forward crankcase was covered by a unique Boeing oil-coolershutter assembly that Boeing called a nose cowling. Fuel was carried in three tanks: a 55-gallon main tank in the belly and one removable 26-gallon auxiliary tank in the root of each outer wing panel. The last 20 gallons in the main tank were considered the reserve supply. A single fuel tank selector (there were two on the XP-936 and the early P-26A's) was mounted on the auxiliary panel. The handle for the manual fuel pump used in starting was mou nted on the left side of the cockpit on the same mount as the elevator trim control. An eight-galion oil tank was installed ahead of the no. 1 bulkhead. The oil circulated from the engine back to the tank through a core-type cooler installed below the engine accessory section.

SERIAL NUMBERS:

SPECIFICATIONS AND PERFORMANCE:

(Ibs.lsq.·) Height (tail up) Height (tail down) Wheel track Wheel base Empty weight

Gross weight

XP-936 23'5.13" 27'0" 150.0 sq.' 4.86

P-26A

18.26 9'4.5" 10'5" 5'1,5"

19.76

23"7.25" 27'11.6" 149.5 sq.' 5.21

9'4.5" 10'5"

Ibs.

5".5" 15.0' 2,196 Ibs.

2,740 Ibs,

2,955 Ibs.

15.0'

2,070.5

P·268 23'9"

P·26C 23'9"

27'11.6"

27'11.6" 149.5 sq.'

149.5 sq.' 5.21 20.45 9'4.5" 10'5" 5".5" 15.0' 2,301 Ibs.

3,060 Ibs,

222 mph

Max. speed @ 5.1 .•

211 mph

Service ceiling" Absolute ceiling" Rate of climb (per min.)· Range·

30.700' 31,600' 2.260' 358 mi.

234.0 mph 211 mph 27,400' 28.300' 2,360' 635 mi.

235

235

mph

mph

215 mph 27,000'

?

2,300' 635 mi.

215 mph

27.000' ? 2,360' 635 mi.

• Please nole that because of differenl methods of testing and calculation, performance figures obtained by Boeing and Wright Field for the same aircraft are not always identical. The figures presented here are from Boeing.

AVAILABLE SCALE MODELS AND DECALS: The following is a complete listing of all known P-26 plastic kits and decals: Kits

The three XP-26's were given Army Air Corps serial numbers A.C. 32-412 through 32-414. Air Corps serial numbers for the 111 P-26A's were 33-28 through 33-138, paralleled by Boeing c/n's 1804 through 1914. The 25 follow-on aircraft were 33-179 through 33-203, though the Boeing c/n's were not in parallel. The two P-26B's were 33-179 and 33-180, but their Boeing c/n's were 1919 and 1916, respectively. Aircraft 33-181 through 33-183 were P-26C's with Boeing c/n's 1915, 1928 and 1917, respectively. P-26C's 33-184 through 33-191 were matched by Boeing c/n's 1920 through 1927, but aircraft 33-192 had c/n 1918. The remaining P-26C's, 33-193 through 33-203, had matching Boeing c/n's 1929 through 1939.

Fuselage length Wingspan Wing area (gross) Wing aspect ratio Wing loading

Max. speed @

optimum alt.·

5.21 20.56 9'4.5" 10'5" 5".5" 15.0' 2,332 Ibs. 3,074 lbs.

1I100th: AHM 1I72nd: Advent, Revell 1/48th: Aurora, K&B Decals Microscale: 1J32nd-32-31

ABOUT THE PHOTOGRAPHS: The photographs used In Minigraph 13 reflect the stateof-the-art In photography at the time the P-26 was in service. Of course there was no significant color photography in the 1930's when the P-26 was in its heyday, so all P-26 photos, with few exceptions, were taken in black and white. The color photos used in Minigraph 13 depict the two surviving P-26A's, both of which are wearing notably inaccurate markings and color schemes. Aircraft were not photographed extensively by the government in the 1930's. The manufacturer took "around-the-clock" and detail views for his own records, in support of required customer documentation and limited pUblic relations work. The customer-in this case the US Army Air Corps-also took its own identification views at Wright Field when prototypes and early production models were ·sent there for testing. The user organizations, most notably the squadrons, were also short on conventional aircraft photos. Most squadron-related imagery tended to subordinate the aircraft to the people who might be involved. In-flight views were usually reserved for the more spectacular images, most notabiy long shots of the aircraft in formation.

It therefore remained for the amateur enthusiasts and photo collectors, who had easy access to Air Corps bases in those relaxed days, to photographically document production aircraft in operational settings. Concern about markings, multiple views of the same aircraft without . background distraction, closed doors, and centered controls, helped push the quality of amateur aircraft photography to a level on par with whatever could be obtained from more professional sources. Any markings change was a valid reason for enthusiasts to shoot the same aircraft more than once; companies and government agencies rarely bothered. The majority of the collectors and enthusiasts in the 1930's used a standard folding camera that required size 616 film. This produced negatives that were approximately 2-3/4" x 4- 112 "-ideal for the oblong proportions presented by aircraft sitting static on the ground. Before 616 roll film was discontinued in 1975, most collectors had already switched to the more convenient 35mm format. There were basically two types of black and white film available in the 1930's. Verichrome, the cheapest, was an orthochromatic film that made red appear to be almost black, yellow to appear very dark, and blue to appear significantly lighter in the positive print. A faster and more expensive film was Super-X, which was a panchromatic film that rendered red as a light shade of grey, blue as a darker shade, and yellow as almost white. These characteristics were particularly noticeable when Super-X was used with an amber filter.. Collectors, as Is often the case today, shot negatives not only for their own files, but also for others with whom they traded. This trading, which in the case of many photos in this book took place nearly a half-century ago, today causes problems in determining accurate credit lines. A print supplied by one collector could easily have been made from a negative taken by another. This problem is made significantly more complicated by the fact that some negatives, during the half-century that has passed since they were taken, have passed through many hands, with the name of the original photographer having long ago been lost in the trading process. Accor· d ingly, the majority of the photos in this book are a mix of Boeing, Army, and Individual collector's photos, properly credited wherever possible. The structural and detail photos, unless otherwise noted, are from the files of the Boeing Company.

The Boeing Model 281 was the export version of the P-26A and differed from it only in minor details. This aircraft is the first demonstrator (X-12771) at roll-out at Boeing Field on August 2, 1934. Coloring was the same olive drab and yellow seen on most production P-26A's. Note total absence of antenna masts on both the forward cowling and the vertical fin. 10

Three-quarter rear view of the first Model 281 demonstrator providing detail markings reference. Boeing logo on vertical fin is noteworthy, as is X-12771 registration on rudder. Note that the horizontal stabilizer root fairing is painted yellow and that the leading edge is black. Also visible on the wingtips are the fairings for the navigation lights.

P-26B of the 17th Pursuit Squadron photographed on orthochromatic film. Yellow wing appears as dark as the olive drab fuselage.

A P-26A of the 94th Pursuit Squadron also photographed on orthochromatic film. Note how light the later blue fuselage appears compared to the yellow tail. The • fuselage band is red.

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The crude figure 8 in washable paint identifies a 94th Pursuit Squadron P-26A entered in the 1935 Mitchell Trophy Race at Selfridge Field.

A lineup of P-26A's of the 94th Pursuit Squadron at Selfridge Field. Tail numbers are last two digits of aircraft Army serial number.

P-26B. 33-194, of the 17th Pursuit Squadron, converted from a P-26C. After mid-1937, a diagonal stripe identified the leader of "B" Flight in a squadron.

P-26A, 33-124, of the 94th Pursuit Squadron with wide red, white, and blue stripes on the wing in addition to the squadron's red fuselage stripe.

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The 27th Pursuit Squadron also had P-26A's, but they were not photographed as extensively as those of the 17th and 94th Squadrons.

P-26A, 33-133, with open-sided wheel pants, 1st Pursuit Group insignia on the engine cowling, and the group commander's name, "Pilot - Col. Royce", painted on the engine cowling as well.

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P-26A, 33-123, was originally assigned to the 94th Pursuit Squadron but was transferred to the Headquarters Squadron of the 1st Pursuit Group and carried the group insignia on its fuselage.

P-26A, 33,195, formerly qf the 95th Pursuit Squadron, as flown by the 1st P.G. in its original markings with the 95th Squadron insignia removed and the last two digits of the Army serial number added to the cowling/fin.

J P-26A, 33-122, of the 17th Pursuit Squadron with the new tail designator adopted in mid-1937. PA 22 translates as 20th Pursuit Group, Airplane No. 22.

P-26A, 33-64, in the black-and-white markings of the 34th Pursuit Squadron. Absence of forward antenna mast indicates no radio.

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P-26A's of the 34th Pursuit Squadron (foreground) and 73rd Pursuit Squadron (background) at March Field, California, in 1934.

12

P-26A of the 73rd Pursuit Squadron. "Bear" insignia and red and yellow trim (wings and vertical fin) are notable.

Water-paint camouflage is seen as applied to a 34th Pursuit Squadron P-26A for the 1934 West Coast War Games. Note squadron patch on ground crew member's jacket.

All P-26A's of the 17th Pursuit Group are seen lined up for inspection at March Field. Aircraft 102 and 100 were assigned to Group Headquarters; 00 was assigned to Wing Headquarters.

Initial markings for the 20th Pursuit Group's P-26A's were large white block figures on the fuselage, 0 thru 48.

Interim markings are seen on a 20th Pursuit Group's P-26A. Markings consisted of scalloping in the squadron colors applied with an appropriate outline to the engine cowling.

An oddity of the 20th Pursuit Group was that the group insignia, rather than the squadron insignia, was applied to all aircraft. Note how light the blue fuselage of this P-26A appears when photographed on orthochromatic film.

P-26A, 33-102, transferred from the 17th Pursuit Group to the 20th. Note group rather than squadron insignia on fuselage and three-color cowling of a headquarters and headquarters squadron aircraft.

Eighteen P-26A's of the 20th Pursuit Group, all with group insignia on the fuselage and a mix of cowlings in solid squadron colors and three-color group headquarters coloring.

Nine P-26A's of the 20th Pursuit Group headquarters and headquarters squadron with three equal color areas on the cowlings and the new tail designators of the mid-193711940 period. PT translates to 20th P.G.

13

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P-26A's of the 20th Pursuit Group's 77th Pursuit Squadron with 193711940 tail designators and new standardized command stripes in the squadron color (white).

P-26A, 33-77, was defivered to Bolling Field on April 24, 19:1'4. Note Bolling Field insignia and blue and yellow striped cowling.

The first P-26A, 33-28, after crashing at March Field on October 23, 1934, while testing experimental wing flaps. Note how the modified headrest protected the cockpit area after the aircraft flipped over.

The first Model 281 demonstrator is seen on September 13, 1934, crated for shipment to China. Note the extra set of low-pressure Goodyear "Airwhee/s".

All ten of the Boeing Model 281 's ordered are seen shortly after their arrival at Nanking, China, in 1936. Each aircraft was assigned a large fuselage number from 1 thru 10. Note lack of radio antenna masts on the fuselage and vertical fin. Also note that some aircraft have tail wheel fairings and some do not.

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A P-26A of the 19th Pursuit Squadron, 18th Pursuit Group, over Oahu, Hawaii, on March 6, 1939. The fuselage command stripes and engine cowling are painted gold. The base fuselage color is blue. 14

Starting in 1940, formerly blue-and-yellow P-26A's were repainted over-all silver. The aircraft shown are in the 19th Pursuit Squadron, 18th Pursuit Group, Wheeler Field, Hawaii.

The last P-26B in the continental US, 33-197, shown in olive drab and gray camouflage when it was the only P-26 in the 40th Pursuit Squadron, 31st Pursuit Group at Selfridge Field, in early 1941.

P-26B, 33-197, at its last flying station-the 10th Air Base Group at Chanute Field, Rantoul, Illinois. It was based there from June of 1941 thru October of 1942.

The P-26A's transferred to the Philippines Army Air Force from July to November of 1941, retained their US Army colors and markings.

The last P-26A to be photographed in US Army markings. P-26A, 33-49, is seen at Guatemala City, Guatemala, on May 11, 1943. The tail serial number, adopted in January of 1942, translates to 33-49.

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Guatemalan Air Force P-26A in flight after WWII. The fuselage has been stripped of paint and shows original anodized metal.

P-26A, 33-92, of the 94th Pursuit Squadron is seen on skis. Note the cutout on the inner side of the wheel pants to accommodate the hydraulic snubber.

P-26A, 33-56, with Bolling Field markings, is seen mounted in the NACA full-scale wind tunnel at Langley AFB, Virginia, in order to test experimental flap installations.

Decoration of the second Model 281 demonstrator was inspired by the P-26A's of the 34th Pursuit Squadron. The fuselage and landing gear were gloss black and the wings and tail were yellow. 15

Fresh paint on the fuselages of these 94th Pursuit Squadron P-26A's is evidence of the recent reinforcement of the upper aft fuselage structure. Aircraft No. 23 is 33-123, now owned by the Planes of Fame Museum.

On most P-26A's, the open cockpit door covered the aircraft serial number which was stenciled in black or white on the left fuselage side along with crew weight information.

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."'ollowing an accident which resulted in serious damage to the airframe: P-26A, 33-103, is loaded on a truck at snow-covered Selfridge Field for a trip to the repair depot.

Wright Field technicians mounted this P-26A on a decorated truck as part of the Field's participation in a Dayton parade.

Two Chinese Model 281 's are seen undergoing maintenance in a Nanking hangar. The aircraft on the left has the original over-all gray scheme while the aircraft on the right is in the la ter over-all olive drab scheme

P-26A of the 6ih Pursuit Squadron, 18th Pursuit Group, in Hawaii in 1939. The cowl and forward fuselage are trimmed in red with a white outline.

P-26A, 33-135, as presently displayed in the National Air & Space Museum in Washington, D.C. This aircraft was displayed in the AF Museum for many years.

Edward Maloney's (Planes of Fame Museum) restored P-26A, 33-123, on September 24, 1962. Its appearance at that time was spoiled by the prevailing FAA requirement calling for foot-high registration numbers on all civil aircraft.

16

Seen in July of 1969, during an Ontario, California airshow, Ed Maloney's P-26A was still wearing the large civil registration (N-3378G) required at the time'by the Federal Aviation Administration. This rule has now been rescinded and the large N-number has been removed.

Seen in August of 1978, during a Chino, California airshow, Ed Maloney's P-26A no longer had large civil registration on fuselage side. Vertical fin color also had changed from yellow to white, and the black tail number, 23 had been revised in shape and location. Additionally, the vertical fin and horizontal stabilizer leading edge scallops had been changed in color from blue to red.

17

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Ed Maloney's P-26A, one of two complete P-26's extant in the world, is the only one that remains flyable. Demonstrations of this ability are sporadic-and almost always well-attended by buffs and enthusiasts. This 1978 photo was taken as the aircraft taxied out for take-off from its home field in Chino, California.

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Recent photo of Ed Maloney's P-26A, taken in May of 1983, during a display at the Chino, California airport. Red, white, and blue color scheme of the 17th Pursuit Group, 34th Pursuit Squadron is not accurate for this particular unit. Maloney acquired 33-123 in 1957.

18

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The P-26's Df the 1st Pursuit GrDup at Selfridge Field had the squadrDn insignia backed with a diagDnal band in the squadron cDIDr until mid-1937. The 17th squadron used white with a black bDrder; the 27th, dark yellDw with a black bDrder; and the 94th (shown), a red stripe with a yellDw bDrder. The fin number (which represented the last twD digits of the Army serial number) and the cDwling number were in the squadron cDIDr. The fuselage, cDwling, and landing gear cDfDr changed from Dlive drab tD medium blue during 1936 and early 1937.

The 17th Pursuit Group had unique markings fDr its P-26A's during the year that it had them. The squadrDn number was carried in large white Dr yellDw blDck figures IDngitudinally under the belly, and the individual airplane number was carried similarly Dn the tDR Df the fuselage and Dn each side Df the fin. P-26A, 33-51, ND.2 Df the 34th Pursuit SquadrDn, is illustrated with a white fin and headrest, and the tDp Df the stabilizer scallDped in black. The fuselage striping was black and white.

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Each squadrDn Df the 17th Pursuit GrDup carried squadrDn insignia in the standard pDsitiDn shDwn. P-26A, 33-60, nD. 30 Df the 73rd Pursuit Squadron, had a red fin, stabilizers, and headrest with yellDw scallDping and red and yellDw fuselage striping. AlsD, each pilDt's name in the grDup was carried in a shield in the squadron cDIDr just ahead of the left side Df the cDckpit. RibbDns above and belDw the shield Dn nD. 2 Df the 34th SquadrDn read "CDmmunicatiDns Officer".

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P-26A, 33-84, Df the 95th Pursuit SquadrDn. The tail and headrest cDIDrs were blue with yellDw scallDps; the fuselage striping was blue and yellDw. After the 17th Pursuit GrDup became the 17th Attack Group Dn March 1, 1935, it gave up its P-26A's between April 2nd and August 25th. Those that went tD the 1st Pursuit Group retained their unique 17th Group markings, deleting Dnly the Driginal squadrDn insignia and airplane numbers and adding the 1st Pursuit GrDup fin and cDwling numbers that matched the last twD digits Df the aircraft's Army serial number.

--

In mid-1937, the leader's stripes were standardized at two 4" vertical bands in the squadron color for squadron leaders, a single 4" vertical band for A-Flight leaders, a forward-sloping band (like the old 1st Pursuit Group) for B-Flight leaders, and an aft sloping band for C-Flight leaders. Cowlings were in the squadron color except for the group headquarters and headquarters squadron; in a three-squadron group the cowling was trisected in the three squadron colors. At the same time, the group designators were added to each side of the fin and sometimes the upper left wing. PT here identified the 20th Pursuit Group. This leader's P-26 of the 79th Pursuit Squadron (color white) of the 20th Pursuit Group uses the number 100.

In 1941, some of the P-26's still in US Army service were repainted in the new olive drab and gray camouflage. National insignia application was modified to one star on the upper left wingtip, one on the lower right, and one on each side of the rear fuselage. The colorful Army rudder stripes were deleted. In January of 1942, the aircraft's Army serial number was added to the rudder and fin in a minimum of four 8-inch block figures in either black or yellow. The first digit of the fiscal year was deleted; 33-183 appeared on this P-26C/B conversion as 3183. The red center in the American star marking was deleted on May 15, 1942, because of its similarity to the Japanese "meatball".

The ten Boeing Model 281 's delivered to China were originally painted over-all light gray with national insignia .only on the wingtips and large black identification numbers 1 thru lOon the fuselage. Later, the aircraft were repainted over-all olive drab with 12 alternating white (from the top) and blue horizontal rudder stripes and the Chinese 12-pointed star on the fuselage. The Model 281 demonstrator that crashed in China was painted US Army olive drab and yellow and carried the US civil registration XI2271.

20

When Guatemala established an Air Force in the 1920's it used a star-in-circle marking on the wings and fuselage, similar to that used by the US but in Guatemala's national colors of blue-white-blue. The rudder stripes were vertical blue-white-blue; the markings are still in use today. The P-26A's acquired from the US Army in 1942143 merely had Guatemalan markings applied over the US markings. Later, the Guatemalan P-26A's were camouflaged in green. After the war, some had their fuselage paint stripped and were seen flying in the irregUlar gray of the anodized aluminum skin. The fuselage star of the P-26A's was replaced by large training numbers after the war.

BOEING MODEL 281, X12771-Boeing's first Model 281 demonstrator was painted olive drab and yellow, like its US Army counterparts. There were no trim markings, however, except for the gloss black horizontal stabilizer leading edge. Note that the horizontal stabilizer and vertical fin fairings were painted yellow. The X12271 registration, visible on the rudder, the top of the right wing, and the bottom of the left, was painted in black. The Boeing logo on the vertical fin also was biack, as was the wing walkway at the wing root.

21

Scale: 1/32nd Drawn by Jay Miller 21

22

The only other known intact P-26A is 33-135, now owned by the National Air & Space Mus,eum. Like Maloney's aircraft, the NASM's P-26A is painted in the markings of the 17th Pursuit Group, 34th Pursuit Squadron-though the base color is olive drab, rather than blue.

The standard yellow wings and olive drab fuselage markings seen on most P-26A's offered a pleasing contrast in colors. The NASM's P-26A, seen during its tenure at the AF Museum near Dayton, Ohio, and prior to being placed on display, had previously worn the markings of the Guatemalan Air Force.

23

The AF Museum had P-26A, 33-135, on loan for some seven years prior to returning it to the Smithsonian Institution's National Air & Space Museum. Today it hangs in the latter and is visually accessible from both ground and second and third floor levels of the main NASM building. The revised pitot boom, visible in this view, is noteworthy.

The cockpit of Ed Maloney's P-26A has been significantly changed from the original. The instrument panel has been substantially revised, the guns have been removed (the mounts are visible, however), and the canvas covering is missing from the map and manual rack. Visible in this photo is the crank handle for flap actuation.

24

The standard P-26A cockpit was relatively spartan by contemporary standards. The fuselage walls remained uninsulated, the guns, mounted on either side of the flooring protruded into the cockpit, and instrumentation was minimal, to say the least. The throttle quadrant is visible on the left, the control stick is seen in the center, and the auxiliary instrument panel is directly in front of it.

The XP-936 had the same instruments as the later P-26A, though both differed in detail and layout. Main fuel tank is visible under flooring.

The P-26A main instrument board contained primary flight instrumentation, the pull handle for the starter (extreme left), fuel and oil pressure gauges, a standard 8-day clock, the supercharger pressure gauge, and an engine tachometer.

25

The P-268 cockpit was almost identical to the arrangement found in late P-26A's except for the modified throttle/mixture control lever and the relocation of the right-side cockpit light. The latter was due to the addition of the wing flap control handle. Note primitive radio equipment ahead of control stick.

The early model P-26A auxiliary instrument board permitted control of the fuel management system, lighting, and weapons.

26

Some 20th P.G. P-26A's, such as 33-59, had the US Army serial number stenciled on the inside of the door to permit ready identification when the door was folded down. Door was hinged at its base and facilitated pilot ingress and egress. The door was on the left side of the fuselage, only.

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The P-26C cockpit was identical to that of the P-26A except for the revised auxiliary instrument panel and the addition of the wing flap control handle. On all P-26's, instrument panel glare was controlled by giving the panel surfaces a black crackle finish. The instruments were individually lighted for night ,'lying. Descriptive panel reproduced on the back cover of this Minigraph is visible to the left of the throttle quadrant.

P-26A INSTRUMENT PANa DETAILS

STARTER-~

PULL

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COUNTERS

BOEING NAME. PLATE

The microphone for radio-equipped P-26A 's (33-65 of the 94th P.S., shown) was hung on an elastic cord stretched across the cockpit.

27

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Left side view of a P-26A cockpit illustrates the hinged door, the throttle quadrant, the trim handles, the portable starter crank, the left gun, and the carburetor heat control.

The view looking forward in a P-26A, showing the permanent locatifms of the radio on the right and the liquid oxygen system on the left.

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Equipment in the Model 281 for export was identical to the standard P-26A except for a different radio (not installed in photo). Note flap handle and indicator.

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All P-26's and the Model 281 used standard Air Corps bucket seats designed for a seat-tYPe parachute. The seat back cushion could be used as a life preserver in water emergencies. 28

~, ~ Right side view of a P-26A cockpit illustrates the rack for maps, reports, ang the flight handbook, the right gun, and miscellaneous electrical accessories.

Canvas baggage compartment, with zippered back for access to rear fuselage, is laced into grommets in the side of bulkhead no. 2. The Boeing nameplate is visible on the right and the Air Corps nameplate on the left.

P-26A RADIO EQUIPMENT

RECEIVER CONTROL

RECEIVER MAST

RECEIVER. TUNING CONTROl..

RECEIVER ANTENNA

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The XP-936 fuselage as se~n from the cockpit. The interior was painted with red oxide primer and then with silver lacquer.

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Forward structure of the improved, strengthened, and lengthened P-26A Headrest.

ll-'_ Original P-26A headrest was shorter and on its front end, significantly more rounded than its replacement. BlaCk leather cushion prGvided minimal comfort for pilot. Note handle below headrest fOr removing panel for bag"gage compartment· access.

The first XP-936 had an undesireable airflow problem around the cockpit and headrest, so Wright Field developed some changes. Note the riveted-in patch changing the fuselage contour, the enlarged headrest, and the added slot structure to smooth the airflow around the interim headrest.

29

The original XP-936 landing gear had a full fork on the shock strut and it was necessary to remove the axle in order to replace the wheel. Tires shown are General "Streamlines" and not Goodyear "Airwheels".

The landing gear structure was not stable until both the inside cross-wires, shown, and the flying wires were installed. When the wings were off, a spreader bar, shown, was installed to maintain tension.

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____.....'"'-_..:z':2lit~~~_~ P-26A landing gear are shown attached to a jig that was designed to assist in attachment of fairings. Wheel pant construction details are readily apparent in this view. ;

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The XP-936 wheel fairing, shown, was attached to the wheel pivot arm and moved with it in an arc. On the P-26A/Model 281, the fairing was attached to the shock strut to permit vertical movement. _:::;;;0..........- - . - - - - -

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Front view of complete P-26A landing gear. Note rub strips for moveable wheel pants and the reversion by the flying wires to a round section where they cross.

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Three-quarter front view of complete P-26A landing gear. Fairings for flying wires are notable. Rub strips are particularly visible from this angle.

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MAIN LANDING GEAR PARKING BRAKE LEVCR

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LANDING GEAR IN "TAll" POSITION

A detailed view of one of the several ski-wheel landing gear systems available for the P-26A. Note how the wheel fairings have been cut to accomodate the ski snubbers. Skis fit either wheel.

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The P-26A tail wheel installation is seen without fairing in place. The tail wheel was steerable via cables attached to the rudder pedals. Proximity of tail wheel to fuselage was somewhat unusual.

External view of the new P-26 tail wheel assembly. This was retrofitted to all P-26A's, B's, and C's in service, starting in late 1936. Note sheet metal covering over old cutout.

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The P-26A tail wheel installation is seen with fairing in place. The fairing had relatively close tolerances and could be troublesome if) muddy or highly vegetated environments.

In 1936, Boeing developed a new P-26 tail wheel assembly. It pivoted about the apex to the left and was attached to an oleo-pneumatic shock absorber.

31

CONTROL SYSTEM

....ILEROI't &. ELEVATOR CONTROLS

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A top side view of the wing framework in its jig. Wing construction was relatively uncomplicated yet sufficiently rugged. Forward and aft spars were braced by external flying wires .

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The nearly completed outer wing panefs of the first XP-936 are seen in their assembly jig. Notice the nearly symmetrical rounding of the wingtips-which differed can· siderably from the later semi·tapered P-26 wing. Visible in this view are the ailerons, some ribbing, and most of the wing skin.

Bottom (left) and top (right) views of the finished P-26A wing providing details of flying wire attachment points, flying light positions, location of wing markings, and aux· iliary fuel door location. Wings were painted yellow and provided with markings prior to installation. Compare wingtips of P-26A wing to those of XP-936, above.

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Wing root stub mounts wing hinge points for both spars. Brazier-type rivets were obviously not in short supply at Boeing at the time the P-26 was being built!

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The spars for the center section extended across the fuselage at main bulkheads nos. 1 and 3. Note the recessed structure and hinge points in the trailing edge for wing flaps.

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The Model 281/P-26A wing flap had a recessed trailing edge so that it could extend past the aileron. The single spar is a torque tube.

The trailing edge cove for the wing flaps. This Model 281 wing was built initially to use flaps. modified to accommodate them; the P-26B's and C's were built with flaps. for access to the auxiliary fuel tanks.

A P-26A aileron is seen half-covered in its assembly jig. Note six hinge points. Not visible is ground-adjustable trim tab.

Built-up tail assembly hinges for the P-26A. Hinges were relatively simple ball bearing types that required periodic hand-lubrication.

33

The horizontal stabilizer was a non-adjustable cantilever unit of conventionaL construction. The hinge mounts for the elevator can be seen protruding from the trailing edge.

• Tail assembly was conventional with normal vertical and horizontal tail surfaces, a single rudder, and elevators. A small trim tab was mounted on the inboard trailing edge of each elevator.

The vertical fin was a fixed cantilever unit of conventional construction. It was offset to the left side of the aircraft some 3 deg. to compensate for engine torque.

~-

r.

<0

~.

g~

<;

ig"

The single-piece P-26A rudder is seen in its jig during construction. The ribbing and external skin were all-metal. There were three hinge points and a single leading edge spar. There was no trim tab.

34

RIGHT E:LEVAT0!3.

The elevator was divided into two sections, one of which is shown in its jig. The ribbing and external skin were all-metal. Each elevator section had three hinge points and a single leading edge spar. The cutout for the trim tab is visible on the upper right corner.

f

FUEL SYSTEM


r 55 GAL.. TOTAL. MAIN TANt<.

j ,---

i-

.042 ACU .... 4S0 VENT

GRAV"Y 'LAPPER VALVE

~...;,=,-"""", __(-J~==~j _

_ . __._- 1<:.-2 COCK - 0-2

PUMP STRAINER

NOTE: ALL F'UEL L.INES ~ •.042 ALU ..... ALec 460, UNL.ESS OTHERWISE NOTED,

The 55-gallon main gas tank was installed under the cockpit flooring through removeable panels. The supporting metal tray and cables are noteworthy.

Upside-down view of the fuselage illustrates the gas tank door installation that covers the gas tank in the wing center section.

35

J'" ~.

~.

~.

~

1l. ~ g'

i§"

~

~

"Q'" VltW c.on'U~G

"(o»~~ClI:LY·~_es_3;1f

Top view of the cowling covering the engine mount and engine accessories behind the engine. Note sight mount and offset antenna mast.

Installation of Pratt & Whitney SR-1340E "Wasp" engine in the Boeing XP-936.

Overhead view of Pratt & Whitney R-1340-27 engine in a P-26A. Airspeed venturi is visible between left and center cylinders.

RIGHT 510E view COWLINGMODtL p- 2faA

Right side view 0Ip-26A cowling and Townend ring. Second exhaust stack from top is routed so that the heat it generates Can be used for Carburetor heating,

Left side view of P-26A cowling and Townend ring. As with right side, second exhaust stack from top is routed so that the heat it generates can be used for carbUretor heating.

.:111 1:1

Right side view of P-26A powerplant installation gives good detail of exhaust pipe configuration, engine mounts, carburetor heating system, oil tank, and other miscellaneous accessories.

36

i! Left side view of P-26A powerplant inStallation gives good detaif of exhaust pipe configuration, engine mounts, carburetor heating and oil cooling systems, oil tank, and gun barrel extension tube.

Close-up detail of powerplant accessory area provides good view of 2-wire electrical system and gun barrel extension tube.

The fower end of the steel-tube engine mount bolted directly to the front spar. The box-like structure projecting forward from the No. 1 bulkhead accommodated the pilot's feet and rudder pedals. Silver paint is typical of interior coloring.

Front view of freshly overhauled Pratt & Whitney R-1340-27 "Wasp" engine ready for installation in Ed Maloney's refurbished P-26A, 33-123, in September of 1962.

Overhead view of engine accessory area details down-draft carburetion, engine mount, and other miscellaneous engine accessories.

{ <xl

Rear view of R-1340-27 prior to installation in Ed Maloney's P-26A. Note dual magnetos, intake manifold configuration, and oil sump.

Pratt & Whitney R-1340-27 engine with ring cowling and engine cowling as installed in a Boeing P-26A. Ring cowling improved airflow through and around cylinders.

37

c: ~

."

0

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0

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Though taken in 1962, this photo of Ed Maloney's P-26A gives a good visual impression of the 1930's vintage hand-cranked starting method using the aircraft's inertia starter.

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For routine operations, the Army used an electrically-driven energizer with a geared drive to wind up the inertia starts on P-26's. This is P-26A, 33-51, of the 34th Pursuit Group.

~-<-~~. ...... ~~ ~~. ~~

Two 116-pound demolition bombs are seen mounted on a US Army Type A-3 bomb rack beneath the first XP-936 on March 14, 1932. Drag was obviously not a major consideration in the design of the rack!

Another view of the Type A-3 bomb rack with two 116-pound demolition bombs. Bomb release was strictly mechanical and actuated by a handle inside the cockpit.

,..------~-_.

Five 25-pound fragmentation bombs are seen mounted on a A-3 bomb rack on P-26A, 33-62. The bombs could be dropped individually or all at once.

38

Front view of five 25-pound fragmentation bombs mounted under P-26A, 33-62. The fragmentation bomb was primarily an anti-personnel weapon. Bomb release mechanism is visible on right end of rack.

A parachute flare is seen being carried qn an A-3 bomb rack under a P-26A. The normal load in this configuration was two flares. This flare is marked "inert".

-_.-

~

~

The ammunition box was installed just ahead of the 55-gallon belly fuel tank, permitting the ammunition to feed vertically the two guns installed above it.

~

The camera gun was mounted on the P-26's right wing root and the operating batteries were carried in the right-hand ammunition box. The gun "barrel" was actually a long lens.

Another view of the camera gun installation. The area of coverage was not as restricted as it appears as the target being filmed was usually several hundred feet in front of the aircraft.

A ground crewman is seen loading the left-hand .30-calibre machine gun of a 20th Pursuit Group P-26A, on November 3, 1937. Ammunition was pulled up from the ammo box through doors on each side of the fuselage.

39

ARMAMENT SYSTEM

BOMB RACK SYSTEM GUN CONTR,OL. SWITCH

r.30

,r-AMM. COUNTER.S

CAL.

~EEO

CHUTE

,--.30 CAL. EJECT. CHUTE:

AAMING HANDLE TVPE 8-3

R.!-l.F'EED

Bo....e RELEASE HANOL..£. TYPE A-3

RE:F"ER TO E:LECTR.ICAL

DIAGRAM FOR GUN CONTROLS.

801018 AACK TVPE ....-3 R.H.

The removable /lotation bags are seen inflated on P-26A, 33-52, during functional tests at Wright Field. The bags were made of rubberized canvas and formed to fit under the wing /lying wires. The bags proved troublesome in service and were easily punctured and periodically accidentally in/lated. Accidental inflight inflations could prove ·fatal.

Front and side· views of the Goodyear-manufactured /lotation bags in their inflated condition. The entire system, mounted in a wing upper surface fairing, was mechanically attached to the wing root section with a mechanical actuator connected to a handle in the cockpit. A pressurized carbon dioxide system inflated the bags when the handle was pulled.

40

AEROFAX INC. is pleased to announce its new MINIGRAPH aircraft monograph series. These high-quality, authoritative booklets have been created for the serious enthusiast and modeler and are desiilned to provide textual and pictorial detail not usually found in other readily available books of this type. Each MINIGRAPH contains over 100 photos, fOld-out-type multi-view drawings, color scheme information, systems drawings, and high detailed and accurate text. An extensive title listing is currently in preparation. MINIGRAPHS presently available (marked with an *) or due for delivery during 1985 include the following: . MINIGRAPH 1: LOCKHEED SR·71 (A.12fYF·12/D·21)" MINIGRAPH 2: MCDONNELL DOUGLAS F·15A/B" MINIGRAPH 3: GRUMMAN F·14A/B" MINIGRAPH 4: MCDONNELL F·4D MINIGRAPH 5: MCDONNELL F·101B/F" MINIGRAPH 6: BOEING B·52G/H MINIGRAPH 7: GRUMMAN EA·6A/B MINIGRAPH 8: BOEING P-26 VARIANTS" MINIGRAPH 9: NORTH AMERICAN A3../A·5 VARIANTS MINIGRAPH 10: ROCKWELL INTERNATIONAL SPACE SHUTTLE MINIGRAPH 11: LOCKHEED P·3 VARIANTS MINIGRAPH 12: SAAB ..·35 VARIANTS MINIGRAPH 13: MCDONNELL RF·4 VARIANTS" MINIGRAPH 14: LOCKHEED F·94 VARIANTS If you find the new MINIGRAPH series to you liking and would like to have your name added to our mailing list, please drop us a line at P. O. Box 120127, Arlington, Texas 76012. We would like to hear from you and would particularly appreciate comments, criticisms, and suggestions for future titles. AEROFAX is also in need of interesting, previously unpublished photos of aircraft for use in forthcoming MINICRAPH titles and other AEROFAX publications. If you have such items in your files, please consider loaning them to AEROFAX so that others may have a chance to see them, too. You will, of course, be credited if your photo is used, and a free copy of the publication in which it is used will be sent. AEROFAX is planning to publish a new aviation magazine and 1985 will likely see the appearance of the first issue. If you would like to have your name added to the mailing list of those who will be receiving introductory copies and introductory subscription rates, please write. And don't forget the other fine AEROFAX publications, including the definitive AEROGRAPH series describing the General Dynamics F-16, the Air National Guard, and the Lockheed U-2. Forthcoming AEROGRAPH titles due for release in 1985 include the Convair B-58 and the Douglas A-3. AEROFAX looks forward to hearing from you .... Thanks for your interest, Jay Miller and the AEROFAX, INC. Editorial Staff

WEIGHT

DATA

EMPTY CREW

POUNDS

2213

200

ARMAMENT

125

EQUIPMENT

73

F'UEL MAIN 52.3 GALS.SPEC. 314 INCLUDES 20 GAL. RESERVE (ACTUALTANK CAP'Y 55 GALS.)

AUXILIARY 52 GALS._312 AUXILIARY TANK INST. (2) 77

30

AUXILIARY 3.95 GALS._30 NORMAL LOAD

WING BRACE WIRES WIRE PART SIZE LGTH !!!!!- LGTH OFTHD. NAME~. am'Q !lli. LH INNER .LYING .RQNT RYING REAR .LYING ffiONT LAND'G REAR LANDG

3-4512 AN678AC7850 AN676AC80 AN676AC8875 AN676AC1065O

742

GROSS WEIGHT_ _ 2S55

i

1-*-2020 eo*~ 69

4

78

4 4

2i 21

-24 6B _24 IOGlE

4 2

2 2

-24

i

2

2

2 I I I

FUEL SYSTEM LEFT AUX. TANK 26 GALS.

RIGHT AUX. TANK 26 GALS.

MAIN TANK 55 GALS. (INCL. 20 GAL. RESERVE)

PRIMER VENT

LANDING WIRES MUST BE RIGGED TO APPROX.2200"rENSION WING INCIDENCE ANGLE 1° DIHEDRAL 4° LEVELING LUGS ARE lOCATED ON FLOOR NEAR PIL.OT~ SEAT.

MOVEMENT OF CONTROL SURFACES SURFACE ABOVE NEUTRAL BELOW NEUTRAL AILERON ELEVATOR ELEVATOR F"LAP RUDDER

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24° 30· 30· 30° LEFT

ISO 26° 30° 30° RIGHT

40'·-

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OIL MAIN 4 GALS.

RIGGING DIAGRAM

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K-2 COCK PUMP B-2 REL. VALVE C-2 STRAINER F-4 PUMP CARBURETOR RIGHT ANGLE DRIVE

~--D-2

! ..

VENTS 042ALU • Pl=tIMER LINE A-.026 COPPER. GAGE L.INE *"-.032 COPPER PUMP DRAIN *-.042 AL.UM. AL.L. OTHER WNEe ~·.042.ALUM. AL.L. ALUM. ALeo 4 S.O.

FUEL SYSTEM INST. SEE DWG.15-2707. ELECTRICAL WIRING DIAGRAM SEE: DWG. 6-3008. ONE WIRE SYSTEM F"OR: A.C. 33-28 TO A.C.33-51 INCL. A.C. 33-53 TO A.C.33-IOS INCL. DWG. S-3463, TWO WIRE SYSTEM F"OR: AC. 33 -52 A.C. 33-107 TO A.C.33-138 INCL.