X-15 OPERATIONS FLIGHT REPORT



FLIGHT NO: 1-35-56 DATE OF REPORT: 5/27/63

PILOT: J. B. McKay DATE OF FLIGHT: 5/15/63

CARRIER AIRCRAFT: B-52 #003 LAUNCH LAKE: Delamar

PURPOSE OF FLIGHT: 1. Induced Turbulence with KC-1 and

2. Traversing Probe Evaluation

I. Discussion of Previous Operations

A. The revision to the ASAS switching network, which included the addition of a capacitor and diode, has eliminated the normal SAS roll trip-out experienced at launch of the two previous flights. II. Aircraft Configuration Changes A. The left main landing gear strut was replaced because of a compression buckle adjacent to the upper fitting attachment weld. NAA and NASA personnel disagreed on changes in the buckle intensity following flight 1-34-55. NAA personnel had observed the part during the period of ECP-X-15-155 modification and indicated the buckle dated back to the Mud Lake landing on flight 1-25-44, January 10, 1962. The strut experienced 31 landings at replacement, nine landings following the Mud Lake landing.

B. Air loads imposed on the nose gear pilot inspection door during the opening sequence had been causing deformation of the hinge attachment. A door beef-up of the hinge attachment structure was completed per sketch #776 prior to flight. This configuration change may be related to the door opening in flight.

C. Diodes were installed in the SAS servo solenoid circuit to attenuate engage transients. Manual disengagement of one channel has caused the remaining channels to trip-out in past operations.

 III. Instrumentation Changes A. An instrumentation package including the traversing probe, a two point pressure rake, and two static orifices was incorporated on panel No. 69. IV. Preflight Events A. In an effort to determine the cause for high, oscillating chamber temperatures during previous flights, all the components in the #l system were functionally checked. All parts operated normally. During a subsequent system operation, the pneumatic GN2 supply line for the LN2 injector was abnormally cold and showed frost up to the sensor element. This condition affects the temperature regulation, and an additional heat exchanger was added to provide two passes across the blower inlet to preheat the pneumatic control gas. Normal temperature control was attained following the modification.

B. APU S/N 26AN was removed following flight 1-34-55 for X-15-3, and reinstalled in X-15-1 #2 position following flight 3-16-26. The APU S/N 26AN was again removed for use in X-15-3. APU S/N 24AN replaced S/N 26AN, and a satisfactory load check run was accomplished for flight.

C. The SAS gain selector panel was replaced during the preflight to correct an intermittent condition in the pitch channel at gain 4.

D. The fuel and lox tank regulators were replaced during functional checks: the lox tank regulator required approximately 10 seconds to recover from the unlock condition in jettison, and an external control gas leak was experienced on the fuel regulator.

E. A frequency response test was accomplished on the RAS system to define the conditions of a 13 cps system response in the previous flight. A frequency range of .5 cps to 20 cps was investigated. The roll system functioned throughout the range and the pitch yaw system deteriorated above 15 cps. It is suspected that the SAS system will propagate the 13 cps horizontal stabilizer frequency when aircraft motions occur at this frequency.

F. A preflight ground run was accomplished with engine S/N 107 on May 11, 19663.

 V. Flight Events A. The engine operated until fuel depletion at 84.3 seconds. The fuel was off-loaded with a 46.5 gallon ullage.

B. The nose gear inspection door opened in flight approximately 174 seconds after launch at flight conditions 5180 fps, 91.6K altitude, 661 lbs per sq. ft. dynamic pressure, and 5.22 M. A severe yaw condition resulted and was accompanied by a roll SAS trip-out. Data indicated transients sufficient to induce the SAS trip-out. The SAS was successfully reengaged. Cause for the unscheduled door opening will be investigated.

C. The traversing probe seized approximately 2 seconds after engine burnout, apparently the result of minimum clearances provided in fabrication. Adjustments are in progress to provide adequate clearance.

D. The nose gear extended with the wheels skewed to the right. Evidence on the lake track indicated both tires to be intact at touchdown. The LH tire failed on touchdown as a result of the skewed condition, however, the RH wheel continued to carry the load well into the runout as evidenced by the track of the wheel on the lake. The final portion of the runout was made successfully on the wheel rims. The reason for the gear misalignment has not been determined.

 Approved by: Prepared by:

Perry V. Row Ronald S. Waite

X-15 Senior Project Engineer X-15 Project Engineer