Seversky P-35

Seversky P-35
Seversky P-35A of the Commander (two circumferential strips) of the 27th Pursuit Squadron, 1st Pursuit Group
Type:	Fighter plane
Design country:	United States
Manufacturer:	Seversky Aircraft Corporation
First flight:	August 15, 1935
Commissioning:	1937
Number of pieces:	136

The Seversky P-35 was a 1935 fighter aircraft manufactured by the American manufacturer Seversky Aircraft Corporation. It was the first single-seat fighter of the United States Army Air Corps (USAAC) with a closed cockpit and retractable landing gear.

history

development

The origins of the P-35 go back to the all-metal amphibious aircraft Seversky SEV-3 from 1933. The Seversky BT-8 trainer aircraft was derived from this, but it was clearly underpowered and was quickly replaced by the North American BT-9 .

The concern of the company owner De Seversky was to develop the SEV-3 into more than a training aircraft. In the winter of 1934/35, therefore, the cutting of the first parts for another landplane variant of the SEV-3, designed by chief designer Alexander Kartweli , which was called the SEV-2XP (two-seater, eXperimental Pursuit ). The prototype received a 750 hp Wright R-1670 radial engine and a fixed pant leg chassis. Otherwise, the differences to the BT-8, with the exception of the armament, were small. This consisted of a 0.50 MG (12.7 mm) and a 0.30 MG (7.62 mm), which fired rigidly forward, and a movable 0.30 MG (7.62 mm) in the rear cockpit.

In May 1935, de Seversky decided to use the prototype at the USAAC competition for a successor to the outdated Boeing P-26 , which actually required a single-seat aircraft. In addition, de Seversky learned that the competing designs Curtiss 75 and Northrop 3A , unlike the SEV-2XP, had a retractable landing gear, which gave these machines an advantage in terms of top speed. On June 18, 1935, the 2XP suffered considerable damage during transport to Wright Field , where the comparison flight was to take place.

Not least because of the small number of participants in the competition, de Seversky received permission to repair the machine. Northrop was also given this opportunity, as the 3A suffered from severe vibration problems. After the 3A was lost on a test flight over the Pacific, only the Curtiss 75 remained as the only competitor. With the Seversky prototype restored in August 1935, the time was used and the SEV-2XP was converted into the single-seater SEV-1XP according to the tender. This now also had a retractable landing gear. In addition, the back of the fuselage ran upwards into an edge ( razorback ), which was retained until the P-47 as a typical characteristic of Seversky fighters. The original 750 hp engine was replaced by a more powerful version of the Wright R-1820 . Curtiss then brought a lawsuit that Seversky had not repaired the prototype, but built a new aircraft.

On August 15, 1935, the 1XP reached Wright Field. After extensive testing by the Materiel Division, both Billy Mitchell and his other confidante Chennault were convinced that Seversky would have won the elimination race. In fact, the USAAC rejected both candidates in December 1935 for not achieving the required speed of 480 km / h (300 mph). The actual reason, however, was rather that the United States Department of War, after the bad experience with building the BT-8, did not believe that de Seversky was actually able to deliver a larger number of the machines in a short time. In May 1936 another comparison flight took place, in which the SEV-1XP (this time with Pratt & Whitney engines) and the Curtiss 75 took part again. But this time both achieved even worse flight performance than in the first comparison. The other participants Consolidated PB-2 and Vought 141 did not perform well either. This time, however, the 1XP was declared the winner and on June 16, 1936 Seversky received a contract for the delivery of 77 machines and additional spare parts, which corresponded to a further 8 aircraft.

Series production

The series version differed from the demonstration aircraft, among other things, by the omission of the wheel covers, a 3 ° V-position of the wings and additional armament of a 0.30 cal. And a 0.50 cal. MG above the engine, which fired through the propeller circle. The decisive factor for the success of the comparison flight was the introduction of integral tanks , which enabled the range to be increased by 50% to 1840 km. The Curtiss prototype only reached 1120 km. Because the seat was positioned further forward, the pilot had a better view. The larger fuselage with its own payload compartment also allowed a passenger to be taken along in an emergency.

The fact that Curtiss-Wright also received an order for 210 P-36s in July 1937 was mainly due to the fact that the USAAC did not want to rely on just one manufacturer as the sole supplier of fighter aircraft, especially since Seversky still did not have a single one a year after the order was placed Copy of the P-35 had delivered. Full series production did not begin until November 1937. In order to demonstrate the superiority of the P-35 to the public once again, long-distance races were held and air races took part.

The last example of series production commissioned by the USAAC (36-430) had a landing gear that could retract completely into the wing and a Pratt & Whitney engine with 1150 hp. This machine was given the military designation XP-41. The top speed of 516 km / h was only 16 km / h higher than that of the P-35A.

Racing planes

Seversky built a second SEV-1XP with a more powerful engine, which took part in the Bendix Air Race from Burbank (California) to Cleveland (Ohio) in September 1937 as the SEV-S2 (Special # 2) . The original 1XP also flew in the race as the SEV-S1 with Frank Sinclair at the wheel. The S1 took fourth place, while the S2 with Frank Fuller won the race and $ 13,000 in prize money. The third-placed Jaqueline "Jackie" Cochran, who flew a Beechcraft Model 17 Staggerwing, received the S1 from Seversky and with it on September 21, 1937 set some flight records for women. On March 12, 1938, both signed a contract according to which Seversky should build a racing plane based on the P-35 for Cochran. Chief designer Kartveli mainly reduced the resistance of the cell, which then also served as the basis for the XP-43. The new machine, named AP-7, flew 67 km / h faster than the production P-35. With the AP-7, Cochran was able to win the Bendix race in September 1938. On April 6, 1940, she set a new speed record for the 2000 km route with the machine.

commitment

The first P-35s went to the 1st Pursuit Group in Selfridge Field , Michigan . The P-35's performance was poor, but it was relatively robust. Deliveries stopped in 1938. The P-35 design was the basis for other aircraft, such as the Italian Reggiane Re.2000 and the Polish PZL.50 Jastrząb , which should replace the PZL P.11 .

To increase sales, Alexander P. de Seversky personally made a tour of Europe in a P-35 in early 1939. He was the first American allowed to fly the new Supermarine Spitfire . Sweden finally bought a modified P-35, called the EP-106 to its outdated Gloster Gladiator - Double Decker to replace. The EP-106 had a 1,000 hp (750 kW) Pratt & Whitney R-1830-45 twin-wasp engine. Sweden ordered 120 EP-106s, of which 60 were delivered. The machines had two 7.9 mm machine guns in the aircraft nose and one 13.2 mm machine gun each in the wings. They flew more than 40 km / h faster than the original P-35 and could carry 160 kg of bombs. In Sweden they were given the designation J 9 .

After the US arms embargo on June 18, 1940, no more machines could be exported. The remaining EP-106s were given to the USAAC as P-35A and received American machine guns again. Twelve machines were delivered to Ecuador . 48 machines went to the Philippines . Here they took part in the defense from December 1941 to January 1942. The machines were hopelessly inferior to the Japanese hunters. Only eight machines were ready to fly on December 12, 1941.

In 1942 the machines were renamed the RP-35A and completely withdrawn from fighting. The Swedish J 9 remained in service until 1944. The last machines were finally withdrawn from reserve stocks here in 1951.

Today there is still one J 9 in the museum of the Swedish Air Force and one in the private Fantasy of Flight collection in Florida . The only surviving P-35 is in the National Museum of the United States Air Force in Dayton ( Ohio ).

Designations

Two years after the first 1XP was built (around the end of 1937) de Seversky decided to retroactively assign the AP (Army Pursuit) prefix to all aircraft designs that were potentially usable as fighter aircraft. The second 1XP was subsequently given the name AP-2 in addition to the S2 . The assignment of the work numbers did not follow any recognizable system.

"Seversky's method of assigning c / ns was at best enigmatic and illogical, especially to outsiders — c / n 1 shows up two years after c / n 301, and 301 changed to c / n 35 for one modification, there were found two c / n 2s, and curious large gaps between numbers. All that has caused much head-scratching among researchers, and we have no answers if you happen to have questions. "

- aerofiles.com

variants

Prototypes

Aircraft registration	Factory name	annotation
(N) X18Y	SEV-2XP, SEV-1XP, SEV-S1	1 copy
NX70Y (n. Wiki-commons)	SEV-S2 (Special # 2, Bendix Air Race)	2nd copy of the 1XP
NX1390, NR1390	AP-1 (Army Pursuit 1)	1 copy
NX1250, NR1250	AP-2	1 copy
NX2597	AP-4	1 copy
NX1384	AP-7
36-430	XP-41 (AP-4D)	last, rebuilt copy of the order for 77 aircraft
NX1291	DS-1 (Doolittle Special)	Racing plane
NX2587	EP-1	improved P-35 as export version, 1 copy

Series executions

Military. designation	number	annotation
P-35	76	first production version, Pratt & Whitney R-1830-9 engine with 850 hp (634 kW)
P-35A	60	After the start of the war USAAC took over the 60 aircraft of the third Swedish order lot (15 + 45 + 60 pieces), Pratt & Whitney R-1830-45 engine with 1,050 hp and reinforced armament
EP-106	120 ordered, 60 delivered to Sweden	Series version of the EP-1, military designation in Sweden J9

production

Acceptance of the Seversky P-35 / EP-1 and 2PA / AT-12 by the USAAF:

version	1937/38	1939	1940	1941	TOTAL
P-35	76				76
XP-41	1				1
EP-1		12	48		60
P-35A			54	6th	60
2PA			2		2
AT-12			47	3	50
TOTAL	77	12	151	9	249

Technical specifications

Seversky P-35A

Parameter	Data of the P-35A
crew	1
length	8.2 m
span	11.0 m
Wing area	20.4 m²
height	3.0 m
Empty mass	2070 kg
Takeoff mass	2770 kg
drive	1 × radial engine Pratt & Whitney R- 1830-45 Twin Wasp with 1,050 PS (approx. 770 kW)
Top speed	467 km / h
Marching speed	418 km / h
Service ceiling	9570 m
Range	1530 km
Armament	two 7.62 mm machine guns, two 12.7 mm machine guns, up to 160 kg external bomb load

Countries of operation

• Ecuador , Japan , Sweden and the USA

literature

• James K. Libbey: Alexander P. de Seversky and the Quest for Air Power. Potomac Books, 2013, ISBN 978-1-61234-179-8
• Davis L. (1994) P-35: Mini in Action (Mini Number 1). Squadron / Signal. ISBN 0-89747-321-3

Web links

Commons : Seversky P-35  - collection of pictures, videos and audio files

• P-35 in the USAF Museum

Individual evidence

1. ↑ de Seversky had good contacts with Mitchell since the 1920s and was regularly briefed by him about the military's plans with regard to procurement
2. ^ Libbey, p. 117
3. ^ Libbey, p. 124.
4. ↑ Statistical Digest of the USAF 1946, p. 100 ff .; Butler, Phil: Air Arsenal North America, Hinckley 2004, p. 267 f.
5. ↑ Angelucci, Enzo and Peter M. Bowers . The American Fighter . Sparkford, Yeovil, UK: Haynes Publishing, 1987. ISBN 0-85429-635-2