The Bell P-39 Airacobra saw several iterations and modifications as it transitioned from prototype to production. The final sixty aircraft from the initial order of eighty Airacobras, originally designated as P-39Cs, were completed as P-39D-BEs, marking the beginning of significant changes to the aircraft’s armament, structure, and overall combat capability.
Key Features and Modifications of the P-39D-BE:
Armament Changes:
- The P-39D-BEs eliminated the two .30-caliber machine guns from the nose but added four .30-caliber machine guns to the wings, similar to the British Airacobra I.
- This configuration required a reinforced wing structure to support the additional weight of the guns and their ammunition, with each wing carrying 1,000 rounds per gun, resulting in a total of 4,000 rounds on board.
Structural Enhancements:
- The aircraft were equipped with self-sealing fuel tanks and additional armor plating, improving their survivability in combat.
- A centerline bomb rack was added beneath the fuselage, capable of carrying an external fuel tank or a 250- to 500-pound bomb.
Engine and Exhaust:
- The P-39D-BEs were powered by the Allison V-1710-35 engine, which typically featured six exhaust stubs on each side. However, some units were observed with twelve stubs on each side, indicating minor production variations.
P-39D-1-BE and P-39D-2-BE Variants:
Following the production of the P-39D-BEs, Bell produced 705 units of the P-39D-1-BE, which were almost identical except for a key change in armament:
- 20-mm Cannon: The 37-mm cannon was replaced with a 20-mm cannon, similar to the setup on the Airacobra I/P-400.
- Tail Fillet: The P-39D-1-BE introduced a tail fillet at the base of the vertical stabilizer, which became a standard feature on all subsequent Airacobra variants and was retrofitted to earlier models.
The P-39D-2-BE variant followed, with 158 units produced. These were equipped with the more powerful Allison V-1710-63 engine, which generated 1,325 horsepower, improving the aircraft’s overall performance.
Combat and Deployment:
- Mixed Squadrons: The P-39D-1-BEs and P-39D-2-BEs were deployed in mixed squadrons alongside P-400s in the Pacific Theater, becoming the first American Airacobras to see combat. They were instrumental in early engagements against Japanese forces.
- Lend-Lease to the Soviet Union: A number of these aircraft were provided to the Soviet Union under the Lend-Lease Act, where they played a crucial role on the Eastern Front.
- Photographic Reconnaissance Versions: Some early P-39D models were modified for photographic reconnaissance, designated as P-39D-3-BEs and P-39D-4-BEs, which retained the V-1710-35 engine but were equipped with K-24 and K-25 cameras.
Specifications:
Versions:
- P-39D-BE: 60 units
- P-39D-1-BE: 705 units
- P-39D-2-BE: 158 units
- Photographic Reconnaissance: 26 P-39D-3-BEs and 11 P-39D-4-BEs
Powerplants:
- P-39D & P-39D-1-BE: Allison V-1710-35 (1,150 hp)
- P-39D-2-BE: Allison V-1710-63 (1,325 hp)
Performance:
- Maximum Speed: 368 mph at 12,000 feet
- Rate of Climb: 5.7 minutes to 15,000 feet
- Ceiling: 32,100 feet
- Range:
- Maximum: 1,545 miles
- Combat: 800 miles
Dimensions:
- Wingspan: 34 feet
- Length: 30 feet, 2 inches
- Height: 11 feet, 10 inches
Weight:
- Empty: 6,300 pounds
- Gross: 7,830 pounds
- Maximum Take-off: 8,200 pounds
Fuel Capacity:
- Internal: 120 gallons
- External: 95 gallons