RESTRICTED.

Air Corps TECHNICAL REPORT No. 4465. dated June 16, 1939
ON
FUEL CONSUMPTION TEST IN FLIGHT – XB-15
AIRPLANE WITH FOUR (4) R-1830-11 ENGINES

CONCLUSIONS

a. With the present engines, propellers and instruments, the average range of the XB-15 airplane with 4190 gallons of fuel is about 3500 miles in standard still air, subject to the following variations: mixture setting ±20%, cruising speed ±5%, altitude ±5%, engine condition ±5%, and initial weight and balance ±3%. In addition, wind, weather, etc. affect the range appreciably and usually adversely.

b. There is a definite need on multi-engine long range airplanes of much more reliable means of engine economy control. Toward this end the following would prove beneficial: (1) a reliable torque or horsepower indicator on each engine; (2) full feathering propellers with synchronizers, of a type which permits a selective fixed pitch condition to be used for precise setting of the mixture control; (3) much more reliable instruments and instrument installations throughout; (4) liquid cooled engines, which permit closer control of engine operating conditions, (temperature, etc.); (5) extensive flight research.

c. If the foregoing needs were fulfilled, the range expectancy of the XB-15 airplane would be increased to at least 4500 miles.

d. The exhaust gas analyzers as installed in the XB-15 airplane are not only entirely unreliable, they may even be misleading to a hazardous extent. (See figure 5, page 27). The flow meters, on the other hand, are fairly accurate and reliable.