NASA FRC

 
  May 7, 1963

To: Chief, Research Division

From: Aerospace Engineer, Vehicle and Systems Dynamics Branch

Subject: Preliminary evaluation of X-15 Flight 3-16-26

Flight 3-16-26 was flown on May 2, 1963, by Joseph A. Walker for the purposes of:

a. APU altitude checkout.

b. I.R. and U.V. Experiment.

c. High angle-of-attack aerodynamic flow investigation.

d. AFCS Roll Attitude Hold Evaluation.

 A preliminary review of the data from this flight indicates that the objectives were accomplished as planned. There were no malfunctions during this flight, however, there was a deterioration in the operation of the right horizontal surface actuator which may require replacement prior to the next flight. The maximum velocity was about 5,100 fps and altitude 212,000 feet.

The launch was made in the vicinity of Mud Lake with the AFCS Roll Attitude Hold Mode "on." The hold mode references were; zero bank angle and a heading of 175°. At launch, the airplane rolled right about 12° then left to 14° as compared to right 11° then left to 8° for the previous flight using normal launch techniques. Yaw attitude for both this and the previous flight launch were about the same, less than 2° change. The roll rate for this launch was less than 28°/sec compared to 31°/sec on the previous flight. The above comparisons indicate that the Roll Hold Mode has no significant effect on the launch characteristics of the X-15.

Engine shutdown occurred after about 79 seconds of 100% power, at an indicated velocity of 5,000 fps. Shortly after shutdown the maximum unintentional deviations from the Roll Hold references occurred; heading error was less than 4° and roll attitude error was less than 3°. Generally, these errors were both less than 2° for both aerodynamic and reaction controls.

Near the maximum altitude, the pilot rolled into a 31° right bank and allowed the roll attitude hold to return the airplane to straight and level flight. The system required about 7 seconds to accomplish the maneuver including one 6° overshoot. Heading deviated 3° during this maneuver. Following this maneuver, the hold mode was disengaged.

Automatic reaction controls were used during this flight and required only about 9 pounds of peroxide. Aerodynamic directional stability was quite good at the minimum dynamic pressure (about 5 psf) as evidenced by the fact that only one yaw reaction control pulse occurred during the flight. The pilot rated the controllability on reaction controls as excellent.

The entry was made with speed brakes approximately 17° extended, at an average angle-of-attack of 20° without incident and the pilot rated the entry task and stability as excellent. About 20° of stabilizer was required to hold the entry angle of attack.

A normal landing approach was made with 190 to 200 knots indicated at touchdown. The AFCS was automatically disengaged within 0.1 seconds of main gear contact with -3.5° of stabilizer. During the rotation to nose gear contact, the pilot increased the stabilizer deflection to -9° maximum. The slide out was about 7,900 feet. The gear tread was 10.4 feet at about 400 feet from initial touch down. At the end of the slide out the skid tread was 10.5 feet, compared to 10.46 feet on the previous flight.

Elmor J. Adkins