March 13, 1968

MEMORANDUM for Assistant Chief, Research Projects

Flight 1-74-130 was flown on March 1, 1968, by William A. Dana for the purpose of aircraft checkout following electrical system modifications. The flight was planned to subject the aircraft to the same environment that existed on flight 1-73-126 when total electrical system failure occurred.

The maximum velocity attained was 4250 feet per second (a Mach number of 4.36) at 76,000 feet. A maximum altitude of 105,000 feet was attained.

The primary flight objective and acceptable data were obtained.

Flight Track and Profile

The radar track and profile for this flight are shown in figure 1.

The launch was at Hidden Hills #1 from 45,000 feet, IAS-220 kts, and Mach 0.81. Engine light occurred 0.65 seconds after launch. The launch transients were normal.

The profile was flown essentially as planned. The pilot reported that the inertial height indicated 1000 feet low at launch and continued to lag radar callouts. He adjusted the profile by pushing over to zero g at NASA l's call of 60,000 feet instead of the planned 0.2g. The pilot reported shutdown at the planned velocity of 4100 feet per second; however, preliminary radar data indicated a maximum velocity of 4250 feet per second. The total burn time at 100 percent thrust was 64 seconds. The "equivalent" 100 percent thrust, including thrust buildup and decay, was 65.7 seconds; 1.7 seconds longer than planned which correlates with the higher velocity. The planned pullup to 8° alpha after shutdown was performed and a maximum altitude of 105,000 feet was reached. The inertial height continued to indicate low and indicated a maximum of 100,000 feet. The pilot used speed brakes to adjust for a high energy condition as a result of the 150 feet per second higher velocity. The pattern was normal except for a malfunction of the pilot's G-suit which cut in at approximately 1.5g and caused severe discomfort to the pilot while maneuvering in the pattern.

Stability and Control

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

The pilot reported that the aircraft exhibited less damping at minimum dynamic pressure (approximately 150 pounds per square foot) than the simulator and, therefore, he could not maintain the angle of attack as in the simulator.
 
 

Weight and Balance

A time history of the total airplane weight is shown in figure 3 and the time history of the longitudinal center of gravity position is shown in figure 4.

Air Force Western Test Range Launch Monitoring

Although the planned altitude would not be sufficient to permit the extension of the experiment, power to the experiment was turned on. Postflight examination revealed that the video recorder did not operate as a result of a blown d.c. fuse in the frequency converter. A laboratory check with a replaced fuse produced no discrepancy. Since the fuse is sensitive to quick operation of the power switch, the experimenter believes that the fuse was blown prior to flight date. A fuse check item has been added to the preflight checklist.

MIT/Apollo Simultaneous Photographic Horizon Scanner

The experiment was in position 5 to prevent cycling during the flight since the altitude was not sufficient for proper operation. Power to the experiment was turned on as part of the electrical checkout. No discrepancies were noted. The experiment will not be flown on the next flight. The Barnes modified edge tracker has been installed in the alternate system. The modified experiment is being environmental tested.

Operational Discrepancies

This was the first flight using fiber optics on the cockpit camera. The camera is mounted in the instrument bay with the lens on the left side of the cockpit and adequately shows the left side of the cockpit panel. The quality of the film and location of the camera, however, does not permit precise readings of the prime flight instruments. The standard cockpit camera will be re-installed on the right side of the cockpit and both camera will be used during future flights.

While in the pattern, the pilot's G-suit cut in when a 1.5 to 2g turn into downwind was executed. On the downwind leg when the g-force had decreased to about 1g, the suit released. The G-suit activated during the 1.5g turn into base leg and cut out again when the g-force decreased to about lg. This cutting in of the G-suit caused extreme discomfort to the pilot.

A postflight investigation revealed that the anti-g spring in the suit had been improperly installed allowing the inflation valve to operate at lower than normal g-loadings. The spring has been correctly installed and an investigation is underway to evaluate methods in which the pilot may dump the G-suit in case of a premature activation.

Data Systems Discrepancies

Discrepancies noted on the flight were:

James R. Welsh, Head

X-15 Research Project Office