B. Further analysis of data of flight 1-52-85 indicated an apparent correlation of the aircraft vibrations induced by SAS, the IFDS power transients sufficient to cause computer shutdown, and the noise in the MIT data system. The direct cause was not determined by ground testing. A SAS test series proved that power breaks of even short duration caused a malfunction to occur. Voltage drops to 90 volts produced a 6 cps response in the SAS servo outputs with deflection of .050 to .250 inches. Electrical noise as produced by AC motor fields or operation of solenoids and relays always produced a 6 cps response at the SAS servo. It is known that the Honeywell IFDS will not operate with a voltage spike to less than 99 volts. A major configuration change was made following flight 1-52-85 including removal of the MIT experiment and replacement of the #2 APU and alternator unit. Ground APU runs with alternator power were made with SAS and IFDS operating without incurring the flight power transients.

C. Checks were made to determine the cause for pilot presentation malfunctions of flight 1-52-85. The a indicator "director controller" channel was reversed causing corresponding reversed direction indication. The b indicator was operating normally. An IFDS run was made to verify normal operation of the 3-axis ball pitch axis. The q-vernier setting was demonstrated with a "Goniometer" input. These tests revealed cause for the a-bar malfunction only. A notable fact was evident in that the q-vernier range was ±5 degrees with one degree per graduation (unlike the flight simulator with 2 degrees per graduation.)
 

B. The following changes were made to the flight experiment configuration:
 

D. The final nose gear configuration was installed including revised scoop door captive roller, reversed scoop door hook actuation direction, beefed up gear uplock hook, beefed up F-7 door brackets, and flexible nose gear door mounting brackets (utilizing Belleville washers.) A spare door previously fitted to X-15-1 was used, and considerable effort was expended in fitting the new door brackets and door to the aircraft.

E. Engine S/N 108 (unvectored) replaced engine S/N 107 because of the engine hydraulic leak.

F. The q-vernier indicator range was changed to a plus or minus (10) degree range with two degrees per graduation.

G. The No. 2 APU S/N 25 (alternator S/N ZW6977) was replaced because of alternator drive pad seal leakage. APU S/N 20 (alternator S/N ZW6978) was installed.
 

B. A complete physical inspection was accomplished on all main landing gear components. A major discrepancy was revealed in the lower half of one drag-link assembly. The elbow cam fitting on the upper end was bent such that misalignment, over the drag-link length, of 3/4 inch was produced. A survey of X-15 stock parts also uncovered a drag-link lower piece with the same type deformation; the part was not new, but its history was not available. The cause for this type of failure could not be resolved (NAA was made aware of the condition.) A replacement piece was installed.

C. A 360 day ejection-seat inspection was accomplished.

D. An engine run was accomplished on March 19, 1965 with engine S/N 106. Severe pump oscillations were experienced on the igniter start; the run was completed. A "slot" run (power-pack disconnected) was accomplished to eliminate the metering valve as the cause. Since oscillations were obtained on the slot run, the catalyst bed was considered faulty. Engine S/N 108 (unvectored chamber) was installed and a satisfactory run was accomplished on March 22, 1965. A satisfactory APU run was made and included a generator power run with IFDS and SAS operating. The power noise experienced in the previous flight was not obtained. A high vibration level was noted on APU S/N 20 at turbine frequency due to a seal condition.

E. An aircraft basic weight measurement of 13,624 pounds was obtained prior to mating.

F. The aircraft was mated on March 24, 1965. A flight scheduled for March 25, 1965 was canceled by weather. After the cancellation a complete gear drop with operational nose-gear initiator was satisfactorily accomplished. The gear sequence was Left main, Right main at 29# pull force; and nose-gear at 34.5# pull force with 10-3/4 inch handle extension.

B. The engine thrust appeared low during flight with 575 psig chamber pressure.

C. The 3-axis ball, a cross-pointer was inoperative during flight. The b cross-pointer was offset 2° to the right.

D. The pilot noted structural vibrations on several occasions approaching high key. The SAS performed normally through these flight conditions.

E. The new propellant jettisoning procedure (remaining in jettison until landing) was utilized and resulted in a reduced landing weight. This procedure is allowed by a revised propellant system configuration incorporating a shutoff valve between the emergency source bottle and the #2 source system. The weight at landing was estimated at 14,700 pounds; the previous procedure would have produced an estimated 15,070 pounds landing weight (370 pounds reduction.)