2. The SAS electronics case and gyro assembly were replaced and an alignment was accomplished, reference the previous comments in I-B.

3. The follow-on experiments which were installed and preflighted included:

5. The engine indicator "No Drop" light placard was revised to read "23 Seconds" to better define subsequent pilot action in flight.

6. Engine S/N 110 was replaced with S/N 107 because of pin hole leaks in the chamber. Deterioration would be expected during each run, and since a ground run was necessary, the engine was replaced prior to the ground run. The engine transducer mounts were relocated from the engine to the aircraft during the engine change.

2. Rescaling of the IFDS parameters was accomplished to obtain usable data. The parameters included longitude, latitude, H-dot, and altitude.

3. Because of the cold in-flight environment of the IFDS, one of the heat and vent exhaust ducts near the IFDS computer was removed and plugged. Checks were made to insure blower surge was not produced by the system flow restriction and higher pressure. Tests indicated that the computer local inlet temperature was not significantly changed by the heat and vent duct deletion. A flat plate was installed over the computer aft end to provide partial recirculation between outlet and inlet blowers. A temperature rise of approximately 25°F above bay ambient was obtained at the blower inlet with the flat plate. It is evident that 40°F to 50°F inlet temperatures to the computer can be provided if the initial bay temperatures are controlled prior to system turn-on.

4. Two switches were added to the cockpit pedestal panel:

2. A 10 psig gear case relief valve was used on APU S/N 25, replacing the normal 7.5 psi valve to prevent overlap of the regulator setting and relief reseat.

2. The air density experiment was sent to University of Michigan for incorporation of the radioactive source and final configuration.

3. Post flight engine leak checks revealed several pin hole tube leaks in the convergent throat area of S/N 107. The condition was accepted for the next engine operation. The pin holes occurred in an area of extensive Rokide loss.

4. Satisfactory APU load check runs and BCS, RAS operational checks were accomplished on December 16, 1964.

5. A malfunction of the "C" Radar system was noted during preflight and the electronic case assembly was replaced.

6. An abraded area in the elevator-lid seal was found to have a small leak during closeout preparation. Spare seals were not available, and a temporary repair using RTV 731 was attempted. The repair was satisfactory and prevented an extended delay.

7. The aircraft was mated to B-52 #008 on December 22, 1964. The front hook load cam and roller did not make proper contact. High friction in the moving pieces was suspected. By preloading the parts during the lowering of the nose-gear hoist produced roller-cam contact. Safety was not a concern unless the roller positioning link dropped overcenter which would allow the hook to disengage. A proper link angle, although small, was obtained.

8. Excessive winds and clouds on the scheduled flight date, December 23, 1964, required rescheduling after the holidays. The aircraft was demated to accomplish system preflights.

9. A rerun of the MIT Horizon Photometer preflight revealed failure of a power relay which would have prevented operation.

10. The MLG lower trunnion clevis fittings and the pins were checked for deformation because of the deformations experienced on X-15-3.

11. The pitch-yaw RAS valve was replaced because of leakage.

12. During the preflight of RAS, spurious, irregular yaw-channel operation occurred. The bench checkout of the case was normal; reinstallation of the case and subsequent testing and preflight were satisfactory. Improper pin contact is suspected.

13. The aircraft was mated on January 5, 1965. The B-52 front hook on #008 was disassembled, deburred, and Teflon spray coated after the previous hook cam-roller contact problem. Good operation was obtained after this rework.

14. The scheduled flights on January 6 and January 7 were canceled by weather. On January 8, after partial service, snow on Delamar was reported by the weather plane. The same conditions existed on Mud Lake, and the aircraft was demated and rescheduled for January 19, 1965. A basic weight measurement of 14,082 pounds was made after demating.

15. Engine S/N 107 was replaced with S/N 110. S/N 110 is an unvectored engine.

16. An engine run was accomplished on January 14, 1965. Several discrepancies were noted including pump oscillation, leakage from the lox-fill flapper valve, and engine hydraulic fluid leakage from the thermal relief valve. Later data analysis indicated air was entrained in the engine hydraulic system, since the "V" port pressure did not show its characteristic sensitivity on data.

17. A SAS alignment was accomplished because of unacceptable differential servo displacements.

18. Replacement of the seat half of the seat-suit electrical disconnect was required because of pin damage to the face mask heater circuit.

19. The aircraft was mated on January 18, 1965.

20. The flight was canceled on January 19, 1965 after a 2 hour hold for weather. Review of the IFDS turn-on activities indicated the computer malfunction detector light was not obtained with a program-halt condition (normally obtained at the end of final alignment.) IFDS F-3 was removed and replaced with IFDS F-l including computer S/N F-2 with the computer-dump protection circuit. During the subsequent IFDS operation in the aircraft, an open malfunction detector lead was found, and while checking, the lead was shorted causing failure of the malfunction detector in CEU F-l. The CEU was removed, repaired, and reinstalled. The flight scheduled for January 20, 1965 was rescheduled for January 21, 1965 to accomplish the IFDS work.

21. The flight was canceled on January 21, 1965 because of IFDS. A short IFDS align cycle time of 9.5 minutes was obtained instead of a normal 14 minutes time. Computer F-3 was installed, and a turn-on indicated the computer compute mode was terminated after 2.5 seconds. Cable wiring checks revealed that shorting of an analog output signal was the cause.

22. The flight was canceled for weather on January 22, 1965. The IFDS turn-on and align performance was satisfactory.

23. Flight l-A-82 was accomplished on January 26, 1965 with John B. McKay as pilot and carried on B-52 #008.

At 15 minutes to launch the IFDS velocity started to diverge with oscillations of the inertial rate-of-climb. After the declared abort, the inertial altitude was unclamped (altitude switch on) with a corresponding altitude divergence. After landing, the altitude reference switch was found in the 2.5K position with no explanation of who or how it was moved from the 45K position. (The pilot indicated he did not alter the position after the last selection of 45K). Post flight checks after flight included:

2. The No. 2 APU on-off-jettison valve was replaced because of leakage.

3. Extensive analysis of the IFDS flight problem on l-A-82 in addition to cold environmental testing in the laboratory indicated the Verdan computer is subject to the possibility of number changes in the computer memory and logic changes during the turn-off sequence. Changes were made to the heat and vent system to raise the bay temperature at the computer inlet. Tests indicate computer-inlet temperatures in the area of 20°F to 30°F are critical.

4. Environmental tests in the X-15 elevator bay with the IFDS were conducted to determine the effects of plugging the IFDS computer area exhaust duct. Plugging of the duct did not raise the local temperature at the computer inlet. A 25°F temperature level was obtained with both blowers BLN2, and 40°F to 45°F with one blower BLN2 and one blower ONLY. The 25°F temperature level was reached in approximately 5 minutes.

5. APU load-check runs were accomplished on February 3, 1965. A high No. 1 APU bearing temperature of 160°C was obtained using the no-precool procedure. No restrictions were found in the APU cooling supply to account for the high temperature. A BCS and RAS operation was made satisfactorily.

6. A second series of IFDS environment tests was made with a direct recirculation duct between computer exhaust and inlet blowers. The computer inlet temperatures were excessive. A flat plate was located approximately one inch from the computer blower faces, forming a boxed-off enclosure with open ends. Good results were obtained with a general 25°F temperature rise at the computer inlet over the bay ambient temperature. The plate was permanently attached to the frame of the lower elevator.

7. The MIT experiment experienced a failure of a 3000-volt power supply during preflight. A replacement unit was flown out from MIT.

8. Failure of several FM-FM/PDM multiplex units was encountered. A preliminary bench setup was required to prevent failures in the aircraft before tuning could be accomplished.

9. The aircraft was mated on February 8, 1965 with a successful IFDS simulated flight accomplished after mating.

10. The flight was canceled on February 9, 1965 because of snow on Delamar. Demating was accomplished the next day because of unfavorable lake reports, and to allow X-15A-2 to proceed with a captive flight for landing gear checkout.

11. Selected preflights were accomplished, and the IFDS computer power-dump circuit in the CEU was repaired. The RH SAS servo was replaced because of static hydraulic leakage. The replacement servo would not unlock properly and, in turn, was replaced.

12. Satisfactory APU load-check runs were accomplished on February 12, 1965. The BCS and RAS were also qualified for flight.

13. The aircraft was mated on February 18, 1965.

14. Flight l-A-83 was accomplished on February 19, 1965 with John B. McKay and carried on B-52 #008. The #2 APU would not run properly, with extremely slow start and eventual overspeed. Post flight analysis indicated a blowing gearcase relief valve impinged on the H2O2 filter body causing freezing of the hydrogen peroxide and flow restriction. The flight was conducted through an igniter idle check of the engine. The IFDS was operated in the altitude unclamped mode back to landing with good results. The Tonopah radar was inoperative. The aircraft was demated for APU system maintenance.

2. Inspection of the B-52 pylon after demating (flight 1-A-83) indicated severe permanent buckling of the fairing beyond previous experience. An inspection of the pylon structure and hook rigging did not indicate primary structure was affected. After a warming period and movement of the B-52, the severity of the buckling decreased.

3. An APU load check run, with BCS leak check and RAS operation, was accomplished on February 23, 1965. A 10 psig gear case relief valve was used on the No. 2 APU to replace a component with a nominal 7.5 psig setting.

4. The aircraft was mated on February 24, l965. The hydraulic system was found to be contaminated with large particles after a hydraulic stand change (greater than 100 microns.) Fluid circulation reduced the contamination to an acceptable level.

5. Flight l-A-84 was accomplished on February 25, 1964 with John B. McKay as pilot and carried on B-52 #008. The flight was canceled by local weather at EAFB. A malfunction of the SAS in-flight test was encountered where the pitch and yaw channels did not trip in the monitor test. An improper ground was found to be the cause of the SAS in-flight test problem. The in-flight test box was replaced, the appropriate ground pins in a connector were cleaned, and a satisfactory operation was obtained.

6. Leakage of the engine hydraulic system was evident after flight l-A-84 and traced to the engine governor mounting flange. A leakage rate determination with the engine hydraulic pump operation was made, and the leak was accepted for flight.