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Hello everybody. Today, I’d like to suggest the Boeing XB-15 for US Aviation in War Thunder. The XB-15 was designed and built between 1934 and 1935 and became the very first four-engined American heavy bomber ever envisaged in the US. Only one prototype took its maiden flight in 1937, debuting as the largest and heaviest aircraft ever constructed in the US at that time.
Key Characteristics
- First four-engined American bomber in the US aviation history
- 200-mph (320-km/h) heavy bomber
- Six turrets with one machine gun each
- 8,000-lb basic payload or 12,000-lb overload payload
History
BackgroundOn April 14, 1934, the US Army Air Corps issued a request for a “hemisphere defender,” a long-range bomber capable of flying 5,000 miles (8,047 km) while carrying a 2,000-pound (910 kg) payload at 200 mph (322 km/h). To meet this requirement, Boeing submitted its Model 294 design (later designated XB-15), while Martin proposed the Model 145-A (designated XB-16). The Army ultimately favored Boeing’s submission, deeming Martin’s proposal insufficient.
On June 28, 1934, Boeing was awarded a contract to conduct wind-tunnel tests, provide design data, and construct a mockup under the designation XBLR-1 (Experimental Bomber, Long Range). A year later, on June 29, 1935, the Army contracted Boeing to build a prototype, which was redesignated XB-15 in July 1936 when the XBLR category was eliminated.
Design and FeaturesThe XB-15 was a massive, four-engine, mid-wing cantilever monoplane with an all-metal semi-monocoque construction. It was powered by four 1,000-horsepower Pratt & Whitney R-1830-11 engines. Boeing developed the XB-15 based on its earlier YB-9 bomber, though the XB-15’s trailing wing surfaces were covered in fabric instead of metal.
The aircraft’s interior reflected luxury airliner standards of the era. The ten-man crew was housed in a fuselage equipped with heating, ventilation, rest bunks, a lavatory, and an in-flight kitchen. Engineers could access the engines mid-flight via crawlways inside the wings, enabling repairs. It also featured auxiliary engines to power a 110-volt electrical system, an innovation in aviation at the time. Additionally, the XB-15 was outfitted with cutting-edge autopilot and deicing systems.
The XB-15 had retractable landing gear, with each main undercarriage leg fitted with dual wheels to reduce pavement loading. Defensive armament included six machine guns positioned in the nose turret, forward and rear ventral turrets, top turret, and waist blisters. Sources differ on whether its armament comprised two or three .50-caliber heavy machine guns and four or three .30-caliber medium machine guns, with a total ammunition load of approximately 7,200 rounds. The XB-15 could carry an 8,000-pound (3,600 kg) payload under standard conditions, though it could be overloaded to carry up to 12,000 pounds (5,400 kg) over shorter distances.
Testing and AchievementsFirst flown on October 15, 1937, the XB-15 became the largest and heaviest bomber ever built in the United States at the time. Its serial number was designated 35-277. However, its sheer weight overtaxed the Pratt & Whitney engines, limiting its maximum speed to just 200 mph (320 km/h). This performance shortfall led the Army to opt for Boeing’s parallel development, the B-17 Flying Fortress, as its primary bomber fleet.
After flight testing, the XB-15 was assigned to the 2nd Bomb Group in August 1938 for service evaluation and to familiarize crews with long-range bomber operations. It demonstrated exceptional endurance and payload capacity.
In February 1939, following a devastating earthquake in Chile, the XB-15 delivered 3,250 pounds (1,470 kg) of Red Cross medical supplies, earning its crew the Mackay Trophy for the most significant humanitarian flight of the year. On July 30, 1939, it set two world records, lifting a 22,046-pound (10,000 kg) payload to 8,228 feet (2,508 m) and a 31,164-pound (14,136 kg) payload to 6,562 feet (2,000 m).
In April 1940, the XB-15 conducted classified bombing tests in Panama, assessing canal lock defenses. Despite only three out of 150 bombs had hit the target, the results informed bunker reinforcement strategies. It also undertook reconnaissance missions over the Galápagos Islands. Later in 1940, its defensive armament was removed during maintenance at Duncan Field, Texas.
Wartime Service as XC-105With the onset of World War II, the XB-15 was converted into a heavy cargo aircraft and redesignated XC-105 in May 1943. Modifications included a cargo hoist, larger cargo doors, and an increased maximum gross weight of 92,000 pounds (42,000 kg). Nicknamed “Grandpappy” by airmen of the 20th Troop Carrier Squadron, the XC-105 was decorated with a nose art featuring an elephant carrying a crate labeled “supplies.”
Operating primarily from Albrook Field in Panama, the XC-105 transported freight, passengers, and mail across the region, including to Miami and the Galápagos Islands. It also conducted antisubmarine patrols to protect the Panama Canal. Over 18 months of service, it carried 100,000 pounds (45,360 kg) of cargo, 50,000 pounds (22,680 kg) of mail, and more than 5,300 passengers—a remarkable achievement for a pre-war aircraft.
After eight years of service, the XC-105 was retired in December 1944. In May-June 1945, it was scrapped at Albrook Field in Panama, just around the end of World War II. The remaining scrapped airframe was left at Diablo dump, a swampy landfill southwest of the runway, where it was sunk from the sight. Today, the former dump is now an industrial area, with “Grandpappy” buried underneath.
Specifications
Boeing XB-15General Characteristics
- Crew: 10
- Length: 87 ft 7 in (26.695 m)
- Height: 18 ft 1 in (5.51 m)
- Span: 149 ft (45.415 m)
- Wing Area: 2,780 sq ft (258.27 sq m)
- Powerplant: 4 x Pratt & Whitney R-1830-11 radial engines
→ 850 hp (625 kW) each at 2,450 rpm @ 5,000 ft (1,520 m)
→ 1,000 hp (735 kW) each for take-off- Empty Weight: 37,709 Ib (17,141 kg)
- Gross Weight: 65,068 lb (29,514 kg)
- Maximum Takeoff Weight: 70,706 lb (32,139 kg)
Performance
- Power-to-Weight Ratio: 0.06 hp/lb (0.099 kW/kg)
- Cruising Speed: 152 mph (245 km/h) @ 60% power @ 6,000 feet (1,830 m)
- Altitude Speeds:
- 200 mph (322 km/h) @ 5,000 ft (1,520 m)
- 197 mph (317 km/h) @ 6,000 ft (1,830 m)
- Wing Loading: 23.4 lb/sq ft (114.3 kg/sq m)
- Rate of Climb: 670 fpm (3.4 m/s)
- Time to Altitude:
- 7.1 minutes to 5,000 ft (1,520 m)
- 14.9 minutes to 10,000 ft (3,048 m)
- Service Ceiling: 18,900 ft (5,760 m)
- Absolute ceiling: 20,900 ft (6,370 m)
- Combat Range: 3,500 miles (5,474 km) w/ 2,511 pounds of bomb payload
- Max. Range: 5,130 miles (8,260 km)
Armament
- Turrets:
- 2 or 3 x 0.50-cal. M2 Browning machine guns
- 4 or 3 x 0.30-cal. M1919 Browning machine guns
- A total ammunition of 7,200 rounds
- Bombs:
- Basic bomb load: 8,000 lb
- Maximum overload bomb load: 12,000 lb
Cockpit
See Also - Douglas XB-19 (Formerly XBLR-2)
Conclusion | Why it should be in the game
The US aviation tech tree currently lacks a low-tier heavy bomber, and the XB-15 would be an excellent candidate to fill this gap. As the first four-engine bomber, it could be placed at the lowest BR, potentially around 2.3, which preceded iconic American bombers like the B-34, B-25, and B-17. Besides, the XB-15 holds historical significance due to its valuable service with the US Army Air Corps, leading me to believe it deserves the addition to the game.
- U.S. Bombers: 1928 to 1980s (1984)
- Boeing Aircraft Since 1916 (1989)
- American X & Y Planes Volume 1: Experimental Aircraft to 1945 (2009)
- The one and only Boeing XB-15 — General Aviation News
- Boeing's XB-15 Paved the Way for Heavy Bomber Design - PlaneHistoria
- Boeing XBLR-1/XB-15/XC-105
- Boeing XB-15 - Wikipedia
Thank you for taking the time to read my suggestion! 😃