scope:

Description of Driving Event:

In the gathering of test data for IRT fan blades, data was extrapolated for test section airspeeds greater than approximately 200 mph using the 20% air blockage models. A desire was expressed for more accurate results of higher test section airspeeds ranging up to 350 mph using the 20% air blockage models. A temporary method was found which would provide the desired airspeed at a relatively low cost.

This new method consisted of replacing the original fan blades, installed in 1944, with a modified set of spares. The modification included reshaping the blade hubs to an increased angle of attack of 5 degrees.

The modified fan blade's performance with a reasonable stall margin was calculated to have increased the test section airspeed from 190 mph to 245 mph using the 20% air blockage model. In addition, the drive motor, rated at 5000 hp, only required 2400 hp at 300 mph and maximum rpm. The modified fan blades will take advantage of the remaining horsepower with no alterations of the motor.