July 31, 1967

MEMORANDUM for Chief, Research Projects

Approximately 69 seconds after launch, a complete electrical failure occurred and the engine shut down. This resulted in the loss of telemetry, communications, radar tracking, and temporary loss of all hydraulic power. The pilot was able to reactivate one of the airplane's two hydraulic systems and make a successful landing at Mud Lake, Nevada. Extensive tests and investigations have been performed and are still underway to find the cause of the in-flight failures.

Flight Track and Profile

The radar tracking and profile, up to time of telemetry loss, are shown in figure 1.

Launch was at Smith's Ranch #l with conditions normal. Engine light occurred 1.0 second after launch. Increase to 100% thrust took 2.2 seconds. The planned 34° of q was reached at 25.8 seconds and held around 35° until shutdown. There were no significant deviations from the planned track up to the time of engine shutdown. Available data indicate that engine shutdown occurred approximately 69 seconds after light at an altitude of 104,000 feet. A successful landing was made at Mud Lake, Nevada. The third skid and flaps did not extend. Landing speed was in excess of 250 knots. Landing slideout distance was 9050 feet.

Stability and Control

The time history of the significant stability and control parameters telemetered during the flight is shown in figure 2.

The ballistic portion of the flight was flown without electrical or hydraulic power. Just before re-entry, the pilot was able to reactivate one of the two hydraulic systems for entry and landing. The BCS system was fired but gave little or no control.

Air Force Western Test Range Launch Monitoring

Preliminary data indicate that the IR-signal was erratic throughout the flight and the UV-signal was lost 41.6 seconds after launch. These problems will be investigated after the experiment has undergone complete environmental test. The experiment was not extended because of the electrical failure.

MIT/Apollo Simultaneous Photographic Horizon-Scanner

Preliminary data indicate that there were no discrepancies; however, the experiment is being subjected to environmental test. Data for the experiment were not obtained because of the electrical failure.

Operational Discrepancies

After approximately 69 seconds of engine burn time the engine shut down, instrument panel warning lights began coming on, and all telemetry, radar, and communications were lost. The sequence of the warning lights was: Gross malfunction (inertial system computer), three SAS lights and vibration malfunctions (engine), and number two generator out light. Then all lights and cockpit camera went off indicating complete electrical failure. This sequence occurred in seven seconds.

The pilot reported that the aircraft would not respond to control inputs and the side stick would not move full throw, indicating a complete loss of hydraulic power. By turning on the emergency battery, the pilot was able to re-start the #l Auxiliary Power Unit giving him hydraulic power for a successful entry and landing. The flaps and third skid are wired to the main DC bus which was dead. As a result, the landing was made without flaps or third skid.

The pilot experienced difficulty in opening the canopy and in disconnecting the suit-to-seat disconnect. As a result, after the canopy was opened the pilot elected to pull the restraint release handle which also fires the head rest. The head rest struck the canopy with enough force to tear the canopy inner skin, crack the left inner windshield, and bounce downward striking the pilot on the back of the head. Normal opening of the canopy requires that the seal be deflated before the canopy can slide aft. The first motion of the canopy opening handle unlocks the canopy and vents the seal. Testing shows that the time required to vent the seal is approximately 15 seconds during which time movement of the canopy is very difficult. Test on the suit-to-seat disconnect shows that the unlocking force rises significantly when tension is applied to the disconnect halves. The difficulty experienced by the pilot is attributed to the N2 pressure through the disconnect from the suit vent nitrogen system. In the future all X-15 pilots will make an unassisted practice exit from the X-15 on the ground with complete pressure suit connected and canopy closed.

Extensive inspections and tests have been and are still being performed on the airplane. To data the following have been accomplished:

The following investigations and tests are underway:

Data Systems Discrepancies

As a result of the electrical power failure, no data were obtained after approximately 70 seconds. The discrepancies noted for the data obtained up to that time were: channel #33 of the 0-42-36C oscillograph (rudder pedal force) appeared erratic and data are questionable; channel #27 of the 0-12-36C oscillograph (right and left roll BCS) disappeared; the time code generator had wrong time of day but a time correlation was easily made; the film in the P-3-4E altitude and airspeed recorder stuck to the takeup reel as a result of excessive heat but data were useable. All discrepancies are being corrected.
 
 

E. J. Adkins, Chief

X-15 Research Projects Office

Subject: Supplementary Report on X-15 Flight l-73-126

Final data indicate that the maximum velocity attained was 4210 feet per second (a Mach number of 4.17) at 108,000 feet and the maximum altitude attained was 173,000 feet.

Flight Track and Profile

The radar track and profile shown in figure 1 has been revised to show the projected track and profile after shutdown. The projected values are the results of simulations flown on the X-15 simulator by Major William J. Knight, the pilot of flight l-73-126, incorporating final radar and telemetry data.

MIT/Apollo Simultaneous Photographic Horizon Scanner

The experiment was subjected to environmental testing in the BEMCO 6 cubic foot altitude chamber during the week of July 24. No discrepancies were noted.

Air Force Western Test Range Launch Monitoring

The experiment was subjected to environmental testing in the altitude chamber during the week of July 31. No discrepancies were observed for altitudes less than 45,000 feet and temperatures greater than 0°F. A functional check at 100,000 feet and -60 °F disclosed large power transients and the frequency converter fuse was blown. The fuse was replaced and another run under the same conditions was attempted. Between 90,000 and 95,000 feet, power transients resulted in the blowing of two 15-ampere fast-blow fuses in the lab wall power. The experiment would no longer function properly after this run. Investigation showed evidence of arcing at altitude. The A phase and C phase pins of the experiment's power plug were burned off and the plug was split between all three phase pins indicating strong arcing between the A phase and the other two phases. See figure 2.

The experiment was returned to Nortronics and repaired to flight condition. It was then placed in Nortronics' space chamber and taken to altitude on August 16. At altitude a transistor failed in the radiometer as was the case on flight 1-73-126. The transistor was replaced. On August 21, the experiment was again subjected to an altitude run in Nortronics' chamber. Again power problems were encountered similar to these found on the last run in the BEMCO chamber. The experiment has been removed from flight status until all problems have been solved.

Operational Discrepancies

Because of the power failure experienced on flight 1-73-126, the APU control circuitry of the aircraft is being rewired with careful attention to routing in order to eliminate the possibility of a simple failure affecting both circuits. Also, the experiments are being moved to the secondary bus so that they will not be transferred to the remaining APU in the event of an APU or generator failure. The emergency battery has been replaced with one similar to that used in the F-104 aircraft. The additional capacity of this battery will allow addition of the flaps and third-skid circuitry on the emergency bus.

Although it is thought that the problems discovered with the WTR experiment could have resulted in the failures experienced on flight 1-73-126, it is felt that the conditions under which the failures occurred can not be duplicated during ground-tests in a manner that would prove to be conclusive; therefore, the investigation of the failures experienced during flight 1-73-126 have been concluded.
 
 

E. J. Adkins, Chief,

X-15 Projects Office