August 27, 1964

MEMORANDUM for Chief, Research Division

Subject: Preliminary results of X-15 Flight 3-30-50

The X-15 flight 3-30-50 was executed on July 8, 1964. The pilot was Captain Joe Engle. A heading of 214° magnetic was used at launch. Delamar #l was the launch lake.

The launch conditions for flight 3-30-50 were as follows:

MH-96 - "Adaptive"

R.C. - "Auto"

BCS - "On"

heading vernier - "Standby"

launch point coordinates: 37° 18' N, 114° 36' W

A maximum altitude of 170,400 feet, and a maximum velocity of 5,145 feet per second were attained during the flight.

The total flight time was 596 seconds, (9.91 minutes). The powered portion of the flight lasted 79.25 seconds.

B. Mission Objectives

Flight 3-30-50 had the objectives of:

C. Stability and Control

At launch a pilot induced pitch oscillation was started, (the pilot commented, at the debriefing, that he had the impression the dampers disengaged at launch). The pitch velocity (q) after launch had maximum values of 12°/sec and -8°/sec. An angle of attack of 14.8° was attained 2.25 seconds after launch. A "b" oscillation of »±3° was started at launch, but went unnoticed by the pilot. Subsequent investigation indicates the oscillations were induced by the aileron input used to decrease rolloff at launch.

Ten seconds after launch all dampers disengaged. The dampers remained disengaged for 107 seconds. Pitch oscillations were coincidental with the damper failures, (q = 6.2°/sec and -3.2°/sec).

The pilot commented that it was extremely difficult to stabilize on 28° q during the boost phase. An analysis of the internal data revealed large oscillatory excursions in angle of attack during boost, (10° > a > 4°). Normal acceleration (Az) varied between 0.7 and 2.0 g's, and q oscillated between 28° and 23.5°. The maximum recorded pitch velocities during climbout were; q = 11.2°/sec and q = -9.8°/sec.

After engine shutdown oscillations in three axes were recorded. These oscillations had reached a peak, at the time of damper reengagement, indicating the following values:

13.5° > a > -5.2°

18.5° > q > 1.0°

7.5° > b > -4°

0° > f -93.5°

All oscillations were damped after the reengagement, by the pilot, of the damper system.

The damper system malfunctioned a second time for a period of 30 sec. during the ballistic phase of the flight; however, no significant control problems resulted.

D. Handling Qualities

The control task difficulties have already been discussed under section (c). The pilot ratings for the four primary phases of the flight are given as follows:

(1) Climbout q 5 , f 5 , y 2.5 .

(2) Ballistic q 4 , f 4 , y 2.5 .

(3) Reentry q 2.5 , f 2.5 , y 2 .

(4) Landing q 2 , f 1.5 , y 1.5 .

The approach and landing maneuvers were completed with dampers "on", and no control difficulties were experienced by the pilot.

E. System Operation

The MH-96 adaptive control system disengaged approximately 10 sec after launch. The pilot reengaged the dampers after 107 sec of dampers "off" flight. After a period of 25 sec the dampers again malfunctioned. They were reengaged, by the pilot, 30.6 sec later. No other damper malfunctions were experienced during the flight.

A distracting glare in the cockpit, caused by the reflection of the sun, made some flight instruments extremely difficult to read. The pilot commented that if there had been smoke in the cockpit the instruments would have been virtually impossible to read.

F. Conclusions

This flight could be considered an excellent checkout, on the MH-96 system, for the pilot. During the course of the flight the pilot had two damper failures and an MH-96 power supply failure to contend with. He was also required to transfer BCS control from "auto" to "manual." This could certainly be considered a good exercise in the operation of the MH-96 adaptive control system.

The horizon scanner data is considered, by the pilot, to be valid from apogee to about 90,000 feet during the reentry phase. The aircraft was held within the tolerances for the experiment during the reentry.

The mission objectives were essentially realized.
 

Donald J. O'Mara

Aerospace Engineer