Flight No.: 7 Launch: 0848
Plane: X-15 No. 1 Land: 0859
Number: 670 Total: :11
Pilot: J. A. Walker Date: May 12, 1960
Chases: Capt. Rushworth
John B. McKay
Subject: Performance Buildup and Stability and Control Buildup
This flight marked our first attempt at a launch at a location other than one which could reach Rogers Lake in the event of no engine start. The launch lake location was at Silver Lake near Baker.
B-52 takeoff was made to the east on the base runway 04 and a circling climb pattern established in the vicinity of Rogers Lake until reaching 38,000 ft. at which time course was set in a manner that carried us near dry lakes enroute to Silver Lake. Upon arrival in the vicinity of Silver Lake and reaching the designated 5 minute check point, a 180° turn was made and launch accomplished at the scheduled time. The B-52 climb from 38,000 to 45,000 was also accomplished during the straight flight towards Silver Lake. The whole operation proceeded very smoothly and expeditiously. Prior to the flight it was ascertained that the stable platform was inoperative so this whole flight was made by reference to the standby attitude indicator.
Launch was made with SAS gain 4-4-8 and with stabilizer set at 0 degrees incidence and with the stick displaced about 1 1/2 inches to the left of center to counteract the right roll tendency at launch. This again worked out quite well. The aircraft was established at about 10° angle of attack while the rocket cylinders were being started. All 8 chambers were started and the the roundout and initiation of climb occurred at minimum altitude of 38,000 ft. Nominal 8° angle of attack wads maintained during the climb until the velocity was observed to have decreased to 300 kts. indicated at which time the angle of attack was reduced to about 6°. After the speed ceased to decrease (260 kn) the angle of attack was brought back to 8° angle of attack and this was flown more or less continuously as required to maintain velocity at or above 260 kts. during the climb. The aircraft handled very smoothly during the climb. Altitude and Mach number were called out each 10,000 ft. from 40,000. However, it was noted that the damping in roll decreased somewhat as altitude increased. Actually, this turned out to be of benefit inasmuch as the residual lateral oscillation was not as much of a problem. One could also make some definite lateral input without overcontrolling near neutral. Upon reaching M = 2 in the climb a right lateral pulse was accomplished at standard gain settings. The aircraft appeared to be almost dead-beat in that the roll motion stopped when the stick motion stopped. This was followed by a repeat pulse type roll back to level with the same observed results. Incidentally, the climb became very slow between 60,000 and 70,000 ft. and then had picked back up again.
On reaching 75,000 ft. pushover to 0g was initiated to round out from the climb. It was observed that the crosspointer angle of attack needle was functioning properly so the pushover was made by reference to null position of this angle of attack indication. The maximum altitude was approximately 78,000 ft. As soon as the climb was observed to be arrested the normal acceleration was increased to 1/2 g at a speed of 2.6 Mach number. What with jiggling with the 1/2 g and then instituting pullup to 1 g because the downhill slide appeared to be steepening up, a delay was encountered in checking the Mach meter. As a result shortly after the acceleration was checked, a recheck on the Mach meter showed an indicated number of 3.2. With considerable shock it was realized that the intended program of reducing to half power at the same time as pulling out level had been delayed too long.
Three chambers were immediately turned off. The abrupt deceleration resulting from this caused a complete engine shutdown. The intended directional pulse subsequent to engine shutdown was performed at approximately 3.1 Mach number and indicated that the airplane was stable. Yar and yaw SAS were turned off instead of roll and yaw. However, not realizing that the roll damper was still on for this pulse, it was indicated to the pilot that a more noticeable yawing oscillation resulted from the pulse as compared to previous ones where a yaw roll oscillation was taking place. Angle of attack was in the vicinity of approximately 4° alpha for this pulse.
Subsequent to the directional pulse straight ahead the dampers were turned back on and an attempt to stabilize in a turn at 10° angle of attack was made. Once the pitch attitude was steadied out, roll and yaw dampers were turned on and a lateral pulse was accomplished. However, this appeared to trigger an oscillation which was divergent and the inoperative SAS channels were turned back on which immediately damped the oscillation. This turn had been to the left and immediately after turning the dampers back on, a roll to the right to turn back to the north of Rogers Lake was established at which time the yaw SAS channel was observed to trip off as indicated by the flashing warning light. It was switched to standby and then back on and functioned normally for the rest of the flight.
The intention to utilize the side aerodynamic stick for some evaluation during the glide back to base was abandoned after being initiated as a result of very strained arm position required in order to grasp the hand grip of the control stick and it was thought that any evaluation of its capabilities would be clouded by this aspect.
From Silver Lake launch point to Edwards is approximately 100 nautical miles. This flight was made, as mentioned before, with the stable platform inoperative and this particular condition resulted in no heading information being available for the flight. In addition, the homing .indicator needle was also not functioning correctly and so, its indication of whether we were off course to the left or the right was also missing. The climb, of necessity a steep nose high condition, blots out any visual reference for heading or pitch information. A more or less straight track was accomplished by verbal callout of what the course line was on the initial portion of the powered flight before attaining the final climb angle and maintaining as near wings level condition from then on as was possible. This worked out pretty well on this flight in that when the aircraft was rounded out at altitude, it was observed that Rogers Lake was ahead and just slightly to the the left side of course, more or less in the location desired.
The aircraft itself operated quite well. It was thought that on this particular flight that the stability augmentation system was working better than it had on previous flights in that there appeared to be a smaller residual oscillation or better damping and the over all response of the aircraft is satisfactory. Considerable amount of control was required to establish the intended 10° angle of attack turn after burnout. Including the early shutdown on the engine, a left turn, then a right turn back, we arrived north of north base in the vicinity of 50,000 ft. A lazy left turn from this point on brought us around to the desired downwind leg altitude and the pattern was flown at 300 kts. The exact touchdown speed was not noted but subsequent workup of data shows that this landing touchdown was accomplished at 193 kts. at an angle of attack of 5.6° and a vertical velocity of less than 2 ft. per second.
Having established that the power plant can be started dependably and that the systems function adequately in the aircraft, it is felt that the remote lake launching yields the desired benefits of performance and resulting expansion of the envelope at rather small cost of operational complications.
Joseph A. Walker
Aeronautical Research Pilot