Aircraft: X-15-3 #672 Date: 4-5-62

Flight: 3-3-7 Takeoff: 0923

Configuration: MH-96 Flt cont. system Launch: 1005

Pilot: Neil A. Armstrong Land: 1017

Launch Aircraft: B-52 #003 Total: :12

Crew: Allavie & Fulton

Launch Panel: S. P. Butchart

Some delay prior to cockpit entry may be attributed to difficulty in obtaining satisfactory electrocardiogram recordings in the physiological trailer. Physiological telemetry data was unsatisfactory, and when a skin temperature sensor started burning the skin, the physiological instrumentation was deenergized.

The MH-96 airborne analyzer check was completed with no malfunctions indicated. This was the most successful airborne sequence to date. The inertial velocity was predicted to be questionable inasmuch as doppler operation was erratic.

The launch was performed on the side stick with all axes engaged in the adaptive mode and the stabilizer trim position indicating 1° nose up (leading edge down) and 4° differential (left roll). Pump idle manifold pressures at 360 psi and 2nd stage igniter pressure at 155 psi were solid. At this time the throttle was moved from the cutoff position, igniter and manifold pressures dropped to zero. No engine malfunction lights were noted.

While descending without power the angle of attack reached 15° and light buffet was observed. Approximately 9000 feet had been lost at the time of a successful engine light at 75% throttle (Pc = 470 psi).

No prescribed method of obtaining the desired value of dynamic pressure (1200 psf) during the climb had been devised for a delayed engine light. Inertial velocity and altitude could not be used since the initial conditions would be unknown. Indicated airspeed is not presented in the simulator. In an attempt to achieve an acceptable value of dynamic pressure, the 75% throttle setting and a 10° angle of attack were maintained until a precomputed schedule of indicated airspeed versus burning time was intercepted. At 17 seconds (burning time) and 530 KIAS, the angle of attack was reduced to 7°. When the 24 second checkpoint indicated 600 KIAS (10 KIAS slow) the throttle was advanced to 100% thrust. Although subsequent data reduction indicated dynamic pressure to have reached a value of 1400 psf at M = 2.7, no limit cycles were observed with either the standard flight control mode or with the control stick steering energized to include normal acceleration feedback in the pitch loop.

Although roll hold was engaged without transient (wings level) at 17 seconds, some mild roll oscillations were in evidence at approximately 25 seconds. Pitch attitude hold was engaged at 35° q. As longitudinal acceleration increased, a sensation of increasing pitch attitude was noted. A cross check on the standby artificial horizon indicated the instrument to be unusable in this range after which a flight path angle confirmation was requested from NASA 1. This sensation is believed to be due to the rotation of the total acceleration vector due to an increase in Ax while maintaining a constant value of Az.

Speed brakes were extended at 50 seconds. Due to the previously described trajectory changes, the shutdown time of 68 seconds was abandoned in favor of the desired inertial velocity (4050 fps). An inadvertent delay resulted in an indicated inertial speed of 4200 fps at engine shutdown.

CSS was used to reduce the angle of attack to zero and angle of attack hold was engaged. Reaction control and damping was quite good although the reaction controls were automatically energized considerably earlier than had been anticipated. Altitude-vertical velocity cross checks indicated the peak altitude would be 180,000 ft. Roll and yaw overpowers indicated exceptionally good control and damping.

Pitch attitude hold was engaged at near the peak altitude. The APU/BCS H2O2 low light illuminated at this time and the H2O2 transfer system energized. NASA 1 recommended a 15° a, 30° q entry due to a slight westward deviation of the ground track.

A rudder step at approximately 10° a initiated a rolling oscillation of ±30° bank angle, apparently being maintained by roll reaction rockets. After being unable to trim angle of attack above 11°, it was decided to proceed with the entry at 11° a and wings level.

As the normal acceleration began to rise, several engine malfunction lights were observed. The throttle was cycled out of and into the détente to insure the cutoff position, and the lights were extinguished.

During the early part of the entry, a wings level yaw oscillation of ±3 degrees sideslip was noted. This oscillation was similar to that of a fixed gain, 23° a simulator entry. No structural feedback manifestations of limit cycle were noted. Occasional 2-3 cycle tremors were noted, as on previous flights. Speed brakes were retracted as the airplane neared level flight.

All axes were reduced to fixed gain during the space positioning turn and pulses and steps recorded in each. A wind up turn with control stick steering engaged was limited to 2-1/2 g due to low airspeed. Light buffet was observed, but limit cycles were not noted. Stabilized, full trim deflection (center stick) pitch maneuvers were recorded in each direction and appeared to be near the desired value of 2 °/sec. Similar maneuvers were performed on the side stick with full nose down trim and 5 units of nose up trim. The trim value for zero pitch rate was approximately 1 unit nose up.

The approach and landing were performed on the side stick with normal acceleration feedback. No difficulties were noted during the approach. Subsequent to the flare it became obvious that the gains applied to the Nz feedback were excessive for the final landing. Excessive stick motion was required for the small corrections required near the ground.
 
 
 
 

(Signed)

Neil A. Armstrong

Aeronautical Research Pilot

NAA:bjc