PILOT: John B. McKay FLIGHT DATE: July 8, 1965

CARRIER AIRCRAFT: B-52 #008 LAUNCH LAKE: Delamar

ENGINE SERIAL: 103

FLIGHT PURPOSE:
 

(1) Star Tracker

(2) Pilot Altitude Buildup

(3) Advanced X-15 Landing Dynamics

FLIGHT CONDITIONS:
 

Vmax 5250 fps

Hmax 212,600 feet

Mmax 5.14

Qmax 1621 psf

The primary purpose of flight 2-40-72 was to view the star gamma in the constellation Cassiopeia. The required attitudes for this task, as stipulated by the experimenter, were q = 4.66° and f = 35.89°. The heading required was the same as the launch heading, (i.e. 214° magnetic).

The Star Tracker experiment was unsuccessful with respect to the stellar photography phase.

The pilot experienced great difficulty in acquiring and maintaining the Star Tracker attitudes. The camera platform was against the "stops" for all but a few seconds of the experiment duration.

A primary cause of this situation is the fact that "RAS," (reaction control augmentation system), did not function during the ballistic phase. The situation is summated by the stability and control report as follows:
 

"RAS made one input early in the flight and then failed to operate for the rest of the flight. BCS inputs were spaced far enough apart and too near the peaks of the oscillations to be totally effective in damping out the pitch oscillation that occurred during the ballistic portion of the flight. The pilot was not using any aerodynamic control in this area. Pilot ratings for the Star Tracker attitude task were 5.5 in pitch, 2.5 in roll and 3.5 in yaw."
  The apparent damping problem with use of the manual BCS inputs can be explained by the fact that the internal data showed unusual time lags between the pilot inputs and the firing of the H202 rockets. An investigation of the BCS system revealed five system check valves that did not meet specifications.

A serious problem was indicated during reentry, when the pilot found it difficult to maintain the required trim angle of attack. The required a was 18°, and this should have been maintained with the use of full back trim (dh = -25°). The pilot was holding dh = -25° plus some additional dh and yet was able to hold only 16° a. This angle of attack decreased to 14° as the Mach number decreased before pushover. As a result the dynamic pressure in flight exceeded the planned by about 700 psf.

The main problem involves a discrepancy between the stabilizer angle commanded and the true stabilizer position. Data have been requested to determine the actual magnitude of the discrepancy and the effects of other variables. One indication of the problem is that on flight 2-41-73 during the reentry, the pilot was commanding a dh = -25° but was getting only 18° dh on the stabilizers. The pitch stick bungee forces have been increased for flight 2-42-74 to compensate for the stabilizer drift from the trim position. This problem has existed since the airplane returned from the contractor. Several requests have been made by this office to the Research Division to investigate the X-15-2 control system, however, no action has been taken. It is the opinion of this office that unless the control system problem is solved that this airplane is not qualified for altitudes in excess of 230,000 feet.

The Star Tracker experiment was successful to the extent that the ultraviolet spectrometer data indicated that altitudes in excess of 212,000 feet are required for adequate Star Tracker data.

The landing dynamics data are being used for continuing studies in that area. The landing gear loads during flight were close to those predicted. It has been recommended that the instrumentation for thermal loads on the main landing gear be deleted. Enough experimental data points have been obtained so that the engineers are confident that the gear loads for any given flight can be predicted with good accuracy.
 
 

X-15 Research Project Engineer