Boeing P-26 Peashooter / 281
The Model 248 would form the basis for the P-26, and Boeing created a combat aircraft. A low-wing monoplane with the wing centre section built into the fuselage and also mounting the fixed undercarriage. The wing was fabric-covered and wire-braced and armament would consist of two machine-guns.
After examination, USAAC officials decided that the Model 248 incorporated what they wanted, but there was no budget for a new aircraft. In order to create flying prototypes, the Air Corps and Boeing devised that Boeing would build the airframes at company expense while the Air Corps would supply Boeing with such items as engines, propellers, armament, instruments and other equipment. In a normal military aircraft contract, these items would be supplied to the manufacturer as government furnished equipment (GFE).
This arrangement was mutually advantageous - Boeing could build a new design without going bankrupt while the Air Corps would get a new fighter to test virtually free.
Boeing Project Engineer Robert Minshall started work on the Model 248 during September 1931. The aircraft was given the military designation XP-936. Assigned by Wright Field, this designation meant that the Model 248 was the 936th experimental design (military or civil) to be evaluated by Wright Field. A contract for the first three XP-936 aircraft was signed on December 5, 1931.
Since the aircraft was not being developed to strict military guidelines, Boeing was given a free hand,
The first XP-936 was completed in little more than 70 days. In order to save more time, the aircraft was not fitted with armament, and test pilot Les Tower took the new aircraft into the air on March 10, 1932.
Flight testing also proceeded at a rapid pace (all structural stress testing was still on paper) and the aircraft showed better performance that the P-12F biplane. After limited flight testing, the aircraft was accepted by the USAAC on April 25 at Wright Field, where more advanced testing by a number of Air Corps pilots would take place.
The three XP-936s should have carried civil registrations. However, they were delivered in the military style paint of the day with XP-936 painted on the airframes, apparently in an effort to make the civil aviation authorities think they were in fact military aircraft.
The second XP-936 had been selected for structural testing. These test aircraft were usually non-flying examples, but this example flew from the outset and was delivered by air to Wright Field. Departing Boeing Field on April 22, the aircraft was flown by Lt. L.H. Dawson - another odd procedure since the aircraft was still Boeing property and probably should have been flown by a company test pilot. Once at Wright, the airframe was statically tested (probably to destruction) and it is very unlikely that the second XP-936 ever flew again.
For the third XP-936, the Air Corps determined that this example would be service-tested by USAAC pilots. Accordingly, the machine went to Selfridge Field in Michigan, departing Boeing on May 6. Once again, the aircraft was flown by a USAAC pilot - Maj. G. Brower and it went to the Ist Pursuit Group where pilots from the group's three squadrons put the XP-936 through a rigorous flight schedule.
On June 15, 1932, the three prototypes were officially taken over by the Air Corps with the signing of a purchase contract. Army officials noted that the aircraft was an improvement over previous pursuits, but noted their opinion in cautious language since funding was in such short supply.
The three XP-936 prototypes were essentially handbuilt, so a more economical way of building the fighter was required. Because the P-26 had few straight lines its fuselage had to be covered using long horizontal aluminium strips, beginning at the bottom of the fuselage, each strip overlapping slightly and thus producing a "shiplap" effect.
Stress analysis being a new art, most builders incorporated excessive strength. The P-936's wing was good for +12g and -4g. When the wing was loaded while inverted it withstood 5g without failure. The flying wires reached +14.25g before failing. The Boeing 109 aerofoil was used.
The wing comprised a centre section integral with the fuselage and carrying the undercarriage and a bomb rack, and two removable outer panels based on two spars of builtup flat sheet aluminium. A generous number of ribs of built-up rolled hatsections and short aluminium tubes contributed to the wing's strength. A thin sheet-aluminium skin was riveted to the wing structure. The XP-936s had brazier-head (flattishdomed) rivets, but production aircraft had flush riveting to reduce drag. Most of the skinning was anodised to protect against corrosion.
The XP-936's tailplane began to fail at 90 per cent of its design load (which was 2531b/sq.in), and had to be greatly reinforced. The fin was tested to 130 per cent of its design load (189.61b/sq.ft), Unlike the wing, the tail was of unbraced cantilever design, the all-metal units being built in the spar-and-rib style. Aluminium channel was built into a hinge-line spar, and there was also a diagonal spar. There was no solid leading edge; the upper and lower skins were joined by flush riveting. The ribs did not act as compression members, but were essentially spacers for the aluminium skins.
The control surface hinge lines were channel spars, and pressed aluminium diagonal ribs carried the top and bottom aluminium skins, which were riveted together at the trailing edge. The elevators incorporated the first use in the USA of trim tabs to adjust longitudinal trim in flight. Each aileron had a groundadjustable aluminium trim tab.
The removable welded -steel -tube engine mounting was fixed to the first fuselage bulkhead. Hydropress dies were used to form the smoother panels ahead of the firewall.
The welded steel-tube undercarriage incorporated a rigid 'V' structure attached to the wing root spars that also provided an anchor for the flying wires. Boeing-built oleopneumatic shock struts were used. Each leg held just the inboard axle end, allowing easy removal of the wheel and tyre, The undercarriage was faired with aluminium, and the wheel spats were press-formed from aluminium sheet and attached to the shock strut so that the spat moved with the strut. The undercarriage could become unstable with the flying wires loosened or removed, so a spreader bar was added between the undercarriage legs.
Fuel was carried in a main tank in the fighter's belly, holding 55 US gal, plus removable 26 US gal tanks in each wing root. There was an 8 US gal oil tank in front of the first bulkhead. The cylinders were encircled by a Townend ring to reduce drag.
The two 0.30in-calibre Browning machine-guns could be changed for a 0.30in gun on the port cockpit floor and a 0.50in gun to starboard. The smaller-calibre weapons had 500 rounds each, but only 200 rounds were provided for the 0.50in gun. A Type A-3 underfuselage munitions rack carried a range of light ordnance.
Once contracts were in place and construction on the P-26A had started, few problems were encountered and production gathered pace. By June 1934 all 111 production examples had been delivered.
The first production run averaged out at $9,999 for each aircraft, but this did not include the government furnished equipment (GIFIE) such as engines, radios and armament. The rapid delivery also meant that problems inherent with the design had not really been rectified.
While squadrons were getting used to the type, the global financial and political situation was changing. American expenditure on military aircraft had risen from $25m for the fiscal year 1925 to $69m for FY 1931, and increasing political tensions around the world had led to an arms race. During 1935, the Italian leader Benito Mussolini had given orders to attack Ethiopia while Hitler made his new Luftwaffe public.
In the USA the new Roosevelt administration was backing drastic social reforms to ease the nation out of the grips of the Great Depression, and also allocating unprecedented funds for military aviation. The Baker Board recommended that the Air Corps increase its inventory to 2,320 aircraft while a General Headquarters Air Force (GHOAF) was established for operations not dependent on ground forces. Officially begun in March 1935, the GHOAF had been structured so that its aircraft could be concentrated for a military attack in any direction.
The GHOAF comprised all the attack, bomber and fighter units in the USA, but excluded observation units and five PGs deployed overseas. Between June 1932 and January 1940, total Air Corps strength consisted of 15 Groups. The general staff in charge of operations saw little use for additional aircraft and rarely expended all the funds assigned. Into all this planning came the force of Peashooters.
The aircraft went to the l st, 17th, and 20th PGs. For the pilots, their only training came in the form of reading extremely condensed pilot's notes. Tactics related mainly back to lessons learned during World War One.
The aircraft's tailplane was easily damaged by rocks and gravel when operating from rough fields, so sheet rubber was added to the lower leading edge of the unit, leading to speculation that the P-26 was fitted with de-icers. It wasn't.
Pilots converting from biplane fighters found the Peashooter's landing speed - 82 mph. - to be disconcertingly high. The National Advisory Committee for Aeronautics (NACA), Boeing and the Air Crops worked on the problem and developed four different types of flaps which were tested in the wind tunnel at Langley Field, Virginia, using 33-56 as a guinea pig. It appears that the least effective unit was chosen by Wright Field, installed on 33-28 which, when flight tested, crashed because the flaps blanked out the tail surfaces during approach (which NACA had predicted).
Boeing developed a flap system that was complex and expensive to produce. These were tested on the first of the export variant, the Model 281, which was sent to Wright Field for testing. These flaps brought the landing speed down to 73 mph and the Air Corps accepted the design. In May 1935, Boeing began to receive the P-26 fleet for flap fitting. The first unit to arrive was the 17th PG from March Field, California. This unit had been redesignated as an attack group and would soon give up the Peashooters for more effective equipment. All the P-26s had been fitted with flaps by November 1935.
Pilots who undertook high-g manoeuvres found that certain aircraft were developing skin wrinkles between the tail and cockpit. Boeing recommended a strengthening of the fuselage. Part of the skin was removed so that structural modifications could be made. Also, a new tailwheel assembly was added to improve ground handling.
Although the P-26 was used mainly for daylight operations, pilots complained about exhaust glare in flight during night or twilight conditions. Accordingly, the exhaust system was modified to prevent this problem. Also, pilots found that the pitot tube on the starboard wing would vibrate heavily in flight. Boeing reduced the size of the tube, but this gave inaccurate airspeed readings and a final fix was accommodated by adding a more rigid pitot tube.
Once in service, the P-26 demonstrated a problem that could not be fixed, however. The narrow undercarriage, high centre of gravity and spongy shock absorbers resulted in many nose-overs. The remedy was to issue bulletins to pilots on how to avoid this occurrence.
With the aircraft distributed to the three Groups, the usual flying took place with units practicing tactics, formation flying, cross-country flights and participating in war games. The P-26 was quickly eclipsed by the Seversky P-35 and Curtiss P-36 and Peashooters began to go to second and third-line units.
During 1938, the 18th PG received at least 42 P-26s for the defence of Hawaii. Although these machines were theoretically phased out by the time of the Japanese attack on Hawaii on December 7, 1941, at least a dozen were present at Wheeler Field. One account states that none of these aircraft received damage; another proclaims that several were destroyed or damaged.
The Peashooter apparently did not take any part in the defence of Pearl Harbor, and those remaining may have been retained as hacks or advanced trainers. Thus, the service life of the Peashooter was brief and while the aircraft introduced new features it was also a design that was obsolete from the start. It was also the last production fighter design built by Boeing.
Boeing decided to create an export variant of the P-26A as the Boeing Model 281. This was essentially a standard P-26A airframe with equipment added per the customer's order. Reasoning that these aircraft would be operated off fields more primitive than the American military, Boeing made a study on how to reduce the aircraft's comparatively high landing speed. The first Model 281 (c/n 1959, carrying American civil registration X12771), made its first flight on August 2, 1934. The aircraft was painted in standard Air Corps colours of Olive Drab and Chrome Yellow. After several flights, Boeing installed split trailing-edge flaps which reduced the landing speed. The Air Corps took note and accordingly had their P-26As retrofitted.
At this time, there was a great deal of upheaval in China as various factions fought for control - all the while being watched by Japan. Using company money, Boeing sought out further interest from the Chiang Kaishek government. Meanwhile, the Model 281 was tested with revised wheel fairings more suited to primitive environments and the aircraft was tested with Goodyear Airwheels for use on undeveloped fields.
An order for ten Model 281s for China was finally received, and much of the purchase money was raised by the Chinese community in America. Deliveries of the Model 281 were made between December 2, 1935, and January 5, 1936.
The Chinese 281s were dismantled after test flights and then sent by ship to China where they were reassembled and test-flown. The aircraft were based at Chuying airfield, near Nanking. By this time, invading Japanese forces had begun to overwhelm Chinese forces, and Nanking was an inviting target for "Nell" bombers operating from Taipei on Formosa (now Taiwan).
It is not known if the Japanese were aware of the ten Model 281s based at Nanking, or whether some of them were being flown by mercenary pilots. On August 20, 1937, a force of "Nell" bombers set forth to attack Nanking, all with inadequate defensive armament and without fighter escort (the fighters simply did not have the range). As the bombers arrived over Nanking, they were met by the 281s. Six of the Mitsubishis were destroyed and one of the 281s received light damage. The Japanese seemed to be willing to accept the losses and kept sending the bombers to attack Chinese targets. After securing bases on the mainland, the bombers were able to conduct raids deep into China.
Although records are incomplete, it appears that the Boeings continued to score successes. However, lack of spare parts and the introduction of Japanese fighters into combat meant that when Nanking fell on December 13, 1937, none of the Boeings was airworthy.
During this troubled period, Spain also took interest in the Model 281 and X12275 (c/n 1962) was shipped across the Atlantic and reassembled for test flying at Barajas airfield near Madrid on March 10, 1935. A contract had originally been signed by the Direccion General de Aeronjutica on January 16, 1935, with Boeing and an individual named Alfonso Albeniz. The fighter was demonstrated to the Spanish by company test pilot Les Tower with Boeing vice-president Erik Nelson in attendance.
The Spanish liked the Model 281, but they did not like the price. Accordingly, during June 1935, the Spaniards contracted with Hawker Aircraft in the UK for 50 Fury biplane fighters to be built under licence by Hispano-Suiza.
The Model 281 did not return to Seattle but remained at Barajas. When the Spanish Civil War started on July 17, 1936, the 281 was flown to Cuatro Ventos airfield near Madrid. The aircraft had arrived in Spain with no armament and no synchroniser gear so the Spaniards modified the aircraft to mount two British Vickers machine-guns in pods under the wings, after which the Republican Boeing began flying combat missions.
American mercenary pilot Eugene Finnick described the Boeing as "an old rattletrap". However, the Boeing kept operating and by mid-October 1936 it was one of only three operational fighters left at Getafe. On October 21, it was shot down in a battle with three Fiat CR.32s over the airfield. Pilot Ramon Puparelli escaped by parachute, but the combat career of the sole Spanish 281 was most definitely over.
Sometime later, the Spanish embassy in Paris paid Wilbur Johnson (a Boeing representative) $20,000 for the aircraft.
In addition Panama and Guatamala received ex-USAAC P-26.
In total, only 136 P-26s were built.
The Model 224 would later be refined into the Model 264 and the Air Corps would eventually acquire three as the P-29.
Boeing P-26A Peashooter