In 1934 there was an announcement of the United States Army Air Corps for a heavy bomber with a range of 5,000 miles ( 8050 km ). The first name of the USAAC for the design was XBLR -1 (experimental status, bomber, long range, model 1). The application name " BLR " was only used for 1935-1936 only three designs. Even before the first flight, it was renamed the XB- 15th When the XB -15 first flew on October 15, 1937, she was the largest and most voluminous airplane, which was built up to that point in the U.S..
It broke a number of records in the payload. On 30 July 1939, a record flight was made with 14,154 kg at 2500 m altitude. Due to the size you could move around on shafts in the wings, for example, to carry out minor engine repairs. As the airspeed was low, took a 5,000 -mile flight several days. For this purpose there was even a sleeping area for the crew members.
It was planned to install 1000 hp water-cooled engines, but due to lack of engines R -1830 -11 radial engines were 850 hp ( 637 kW) Pratt & Whitney payable used. The aircraft was therefore greatly underpowered and only reached a top speed of 322 km / h Since this was far too slow for an acceptable heavy bombers, the project was discontinued. No XB- 15 was put into service, the prototype for the XC -105 cargo aircraft for the USAAC was instead converted.
Outstanding innovations in the XB -15
- Automatic de-icing aircraft
- Power supply independent of the engines
- Engines maintainable through service transitions in flight
- Schlaf-/Aufenthalts- and laundry room for the crew
- Double frosted retractable landing gear