NASA FRC

 
  November 1, 1965

MEMORANDUM for Chief, Research Division X-15 Project Office

FROM: X-15-3 Research Project Engineer

SUBJECT: Flight Research Report on flight 3-50-74 flown on October 12, 1965, by Capt. W. Knight I. PURPOSE OF FLIGHT
1. Pilot Checkout


II. FLIGHT PLAN

The flight was planned to provide the pilot with full thrust experience to 4500 fps, and familiarization with various damper configurations.

The flight was flown as planned. No. 2 APU shut down 1.5 seconds after launch during engine start. When the hydraulic pressure dropped to approximately 1000 psi, the left servo mechanically locked and remained so for 3.6 seconds. Because no limit cycle is sensed, gain increases to super-critical values. This is why, when hydraulic pressure returned, an oscillation developed in pitch and roll. The SAS servos lock-up at pressures lower than 900 psi. Change-over to the alternate hydraulic system occurs at approximately 800 psi. Because of actuator orifices servo lock-up occurs before change-over of hydraulics. On ships 1 and 2, the reverse is true.

Following loss of #2 APU, it is recommended that the adaptive system be switched to fixed gain.


Joseph A. LaPierre

Aerospace Engineer