Boeing XB-15

Infobox Aircraft
name=Boeing XB-15

caption=XB-15 on a test flight
type=Heavy bomber
first flight=1937-10-15
primary user=United States Army Air Corps
more users=
number built=1 prototype
unit cost=
variants with their own articles=Boeing XC-105

The Boeing XB-15 (Boeing 294) was a United States bomber aircraft designed in 1934 as a test for the United States Army Air Corps to see if it would be possible to build a heavy bomber with a 5,000 mile (8,000 km) range. It was originally designated the XBLR-1 ("experimental bomber, long range"). When it first flew, it was the most massive and most voluminous airplane ever built in the United States. It set a number of load-to-altitude records, including a 31,205-pound flight to 8,200 feet (July 30 1939).

The aircraft's immense size allowed for passages within the wing, which the crew could use to make minor repairs in flight. Due to the technology of the time, a 5,000 mile flight took thirty-three hours at it's 152-mph cruising speed; the crew was made up of several shifts, and bunks allowed them to sleep when off duty.


The XB-15 was designed to be powered by liquid-cooled 1,000 hp (750 kW) engines. When these were not developed, 850 hp (637 kW) radial air-cooled engines were used instead. These engines left the bomber significantly underpowered; its top speed of 200 mph (322 km/h) was far too slow for a combat aircraft, and the project was abandoned. Even without the improved defensive armament that would have been needed in service, the XB-15 had a maximum takeoff weight 5,000 pounds greater than the later B-17G, but with a total engine output of 1,800 less horsepower.

No B-15s were put into service; the Army Air Corps converted the only prototype into a transport designated the XC-105, which carried freight around the Caribbean during World War II. The XC-105 was scrapped in Panama in 1945.

Technological achievements

Despite its cancellation, the XB-15 did feature a number of significant innovations:
* Automatic Pilot
* De-icing equipment
* Auxiliary power units independent of the main engines to power the electrical system
* Engines serviceable in flight using an access tunnel inside the wing
* Crew compartment with rest bunks, galley and lavatory
* Double-wheel main landing gear.


* United States Army Air Corps
** 2nd Bombardment Group

pecifications (XB-15)

aircraft specifications

plane or copter?=plane
jet or prop?=prop

length main=87 ft 7 in
length alt=32.6 m
span main=149 ft 0 in
span alt=45.5 m
height main=18 ft 0 in
height alt=5.5 m
area main=2,780 ft²
area alt=258 m²
empty weight main=65,000 lb
empty weight alt=29,484 kg
loaded weight main=69,000 lb
loaded weight alt=31,298 kg
max takeoff weight main=77,000 lb
max takeoff weight alt=34,927 kg

number of props=4
engine (prop)=14-cylinder Pratt & Whitney R-1830-11
type of prop=radial engines
power main=850 hp
power alt=640 kW

max speed main=200 mph
max speed alt=170 knots, 320 km/h
cruise speed main=152 mph
cruise speed alt=132 knots, 245 km/h
combat radius main=3,400 mi
combat radius alt=3,000 nm, 5,500 km
ferry range main=5,130 mi
ferry range alt=4,460 nm, 8,250 km
ceiling main=18,900 ft
ceiling alt=7,830 m
climb rate main=670 ft/min
climb rate alt=3.4 m/s
loading main=25 lb/ft²
loading alt=120 kg/m²
power/mass main=0.049 hp/lb
power/mass alt=81 W/kg

** 3× .30 in (7.62 mm) machine guns
** 3× .50 in (12.7 mm) machine guns
bombs=12,000 lb (5,400 kg)

External links

* [ Boeing's description of the XB-15]
* [ Encyclopedia of American aircraft]
* [ USAF Museum description of XB-15]

ee also


* B-17 Flying Fortress
* Boeing Y1B-20
* Boeing 314

similar aircraft=
* Martin XB-16
* Boeing Y1B-20

* List of bomber aircraft
* List of military aircraft of the United States

see also=

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