MEMORANDUM for Chief, Research Division
Subject: Preliminary evaluation of X-15 Flight No. 3-12-22

1. Flight 3-12-22 was flown on December 14, 1962, by Major Robert White for the purpose of:

2. Small pitch and roll mis-trims from null in the AFCS during the pre-launch analyzer check resulted in several indications of temporary malfunctions in the AFCS. These conditions were corrected by the pilot and subsequent operation of the AFCS was satisfactory. All other pre-launch operations were normal.

3. The launch was made in the vicinity of Mud Lake at an altitude of 45,000 feet and the entire flight was completed essentially as planned. The pilot noted a lateral-directional high-frequency, low-amplitude oscillation during both the exit and entry. This was observed to be the characteristic limit cycle oscillation of the AFCS which has a frequency of 1.6 to 2.0 cps with peak-to-peak roll rate amplitude of 4.0 to 5.0 °/second. Lateral pulses were made at angles of attack as low as 2° and as high as 23°. Lateral response was essentially dead beat. Directional excursions caused by lateral pulses were generally less than 2 to 3° of sideslip and were lightly damped. Directional pulses and pilot rudder manipulation at angles of attack greater than 15° were ineffective in producing a directional response. Lateral control manipulation at angles of attack between 23° and 13° and M 4.5 produced a slight divergence in sideslip for lateral control stabilizer deflections of about (?)°. This divergence was forced by the lateral control inputs to a maximum of 5° of sideslip which subsequently converged when lateral control inputs were small. All of the above maneuvers were made with the speed brakes extended approximately 17°. The pilot's impression of the handling qualities were highly favorable, higher than the simulator, and suitable for entry conditions. It is suggested that the next ventral-off flight be a moderate altitude flight with a 12° angle of attack entry from an altitude of 180,000 feet.

4. The new heading vernier indicator was checked out near the flight apogee and the pilot reported favorably on its operation.

5. The AFCS was modified prior to this flight to incorporate an automatic disengage switch for landing. This system operated as expected during the landing for this flight. Approximately 0.7 seconds after the L.H. skid touched the ground, the AFCS disengaged. The AFCS servos all centered and locked after another 0.7 seconds but this was before the nose gear had touched the ground. In addition to the AFCS disengagement, the pilot pushed the stick to the forward stop before the nose gear touched the ground. This procedure resulted in the lowest gear loads ever measured. The maximum negative stabilizer position was approximately 12° and the maximum positive was 13°. The rear skid shock strut rebound following nose gear touchdown and the lift resulting from the positive 15° of stabilizer caused the rear skids to leave the ground for 0.4 seconds beginning 0.5 seconds after nose gear touchdown. This was accompanied by a sideslip excursion of approximately 6° and was corrected by the pilot with a rudder input. It is suggested that on subsequent landings, the pilot should refrain from moving the stick after main gear touchdown, and that the AFCS disengage switch continue to be used.

6. The AFCS automatic reaction controls were used on this flight and functioned satisfactorily. Approximately 11 pounds of peroxide were used by the AFCS.

Elmor J. Adkins

Aerospace Engineer