Plane: X-15 No. 1 #670 Date: April 10, 1960

Flight: #5 T.O.: 08:52

Pilot: J. A. Walker Land: 09:02

Chases: Capt. Rushworth Total: :10

Capt. Knight

J. B. McKay

Subject:. Performance and stability and control build-up

Launch conditions were slightly modified from intended due to necessity to shut down one engine on the B-52 and launch was accomplished at 43,000 feet at Mach .82 near Waldrip north of Lancaster on a magnetic heading of 65°. At launch, about 1-1/2" displacement to the left at the top of the stick was utilized. As a result very little roll to the right was apparent to the pilot. After falling away from the B-52, a moderate left roll started until the stick was returned for recovery to level. This made a very smooth drop away from the B-52. The stability augmentation system gain settings were 4-4-8 for launch and all during the flight except as noted.

All 8 chambers were started. Airplane was established level at 8° alpha after launch. For this flight, the stable platform was operating and the attitude of the aircraft was maintained by reference to the 5~ attitude indicator. Also the heading was monitored by the direction function of the 3 axis ball. 8° angle of attack was maintained until the indicated airspeed was observed to be decreasing towards 300 knots at which time angle of attack was decreased to about 6° angle of attack. We were obtaining better performance in flight than we had anticipated on simulator preparation for this flight, hence the minimum indicated airspeed was observed to be 290 knots indicated at which time the angle of attack was returned to 8° alpha and the climb to 60,000 feet continued.

Upon reaching almost 59,000 feet round out to level at 60,000 feet was accomplished and acceleration to 1.5 Mach number instituted. At this speed a left turn to 15° angle of attack was established. At a steady 15° angle of attack the roll and yaw SAS channels were turned off and a left rudder pulse was performed. The aircraft appeared to be positively damped in the motions following the pulse. Roll and yaw were turned back on and the turn continued until the heading towards Saltdale was obtained.

After rolling out level with the SAS at 4-4-8, a full deflection left rudder input for right sideslip was accomplished. A small amount of aileron was required to maintain straight ahead steady sideslip condition. It looked like maybe about 4° to 5° sideslip was accomplished by full rudder. I had been under the impression that I had obtained full rudder input on the previous flight but observed on this flight that when I really did get full rudder in there was a lot more travel on the rudder pedal and apparently I had hooked my right heel in the junction between the seat foot rest and the floor-board thus blocking the rudder and giving the spurious indication of reaching the rudder travel limits. This time I consciously lifted my right foot as the left pedal was depressed to full throw.

Upon completion of the sideslip, controls were neutralized and the airplane steadied out then roll and yaw SAS turned off with intention of doing a rudder pulse in level flight. However, a residual oscillation was present of sufficient lateral amplitude to cause the pilot to undertake to damp this oscillation prior to making the rudder pulse. The period of the oscillation is such that without reference to roll rate attempts to damp by attitude and roll visual evaluation results in amplification of the normally minimal rolling oscillation into a divergent oscillation. It was concluded therefore that the best policy would be to turn the roll yaw dampers back on and proceed.

It was anticipated that burnout would occur at approximately Mach 2.5 however the burning time was extended somewhat and an indicated Mach 2.6 was achieved at burnout. The burnout point occurred at 56,000 feet indicated.

Immediately upon burnout a left turn to angle of attack of 10° was instituted. After establishing 10° alpha in the turn, roll and yaw SAS were turned off and the oscillation started. This was brought under moderate control and a mild rudder input made, however the oscillation became of such amplitude that roll and yaw SAS were turned back on. Having done this, and steadied the airplane at 10° alpha again the pitch SAS was turned off and the pitch pulse accomplished.

SAS was then returned to 4-4-8 and the airplane rolled out, lined up north of Rogers Dry Lake in good position for approach for a landing. All SAS were turned off then and some mild lateral and pitch motions made to ascertain the handling characteristics during glide.

Upon approaching the base, the SAS was returned to 4-4-8 and the glide speed established at 270 knots. With a wind blowing from southwest at 20 with gusts it had been decided we would land on south lakebed runway 25. Altitude over the base was 27,000 and permitted of a left hand 270° overhead approach to this runway. The glide speed was increased to 300 knots while maneuvering to line up with the runway. The flare was initiated at 3000 feet msl from a glide speed of 300 knots with the flaps being lowered after initial flare and the gear delayed until flattened out close to the runway. It was estimated that touchdown was on the order of 190 knots. During the glide-out after touchdown, it was observed that a small amount of left rudder caused the rear end of the aircraft to start skidding to the right slightly. On reversal of the rudder, the skid stopped and then it slid somewhat to the left. It is apparent then that while pointed into the breeze on the ground, the rudder control action of this aircraft is the same as in flight. It is right rudder that turns the aircraft to the right by sliding the rear end to the left and vice versa.

Successful reference was made to the 3 axis ball throughout the flight for attitude control. Although the altitude indicator was correct at launch, no opportunity presented itself for any continued check or the operation of the altitude presentation during the flight.

Joseph A. Walker

Aeronautical Research Pilot