Subject: Preliminary evaluation of Flight No. 3-10-19

1. Flight 3-10-19 was flown on October 4, 1962, by Major Robert Rushworth for the purpose of pilot check out and ventral-off handling qualities evaluation in the angle of attack range of 2░ to 18░ at Mach numbers below 5.0. A preliminary review of the flight data indicates that the objectives were accomplished. There were no malfunctions or component failures in the MH-96 FCS during this flight. However, the loss of the No. 1 APU during flight, which supplies hydraulic power for the "ball nose" and the yaw damper servo, caused the latter part of the flight to be made without a yaw damper and without angle of attack and angle of sideslip data or pilot presentation.

2. Prior to this flight, the MH-96 FCS was modified to remove the yaw rate to roll axis interconnect and the lateral acceleration loop in the yaw axis. These modifications were necessary to provide the most suitable system for the ventral-off configuration flown. Also prior to this flight, a yellow flashing enunciator light that gives warning to the pilot that one or more damper channels are disengaged was installed on the instrument panel; the auto pilot status lights (green) were relocated to the instrument panel; and open-channel switch guards for each damper engage-disengage switch were installed on the MH-96 FCS control panel.

3. Pre-launch operations were normal for this flight, and the MH-96 FCS Airborne Analyzer check was completed without any malfunctions.

4. The launch was accomplished in the vicinity of Delamar at an altitude of 45,000 feet. The flight, from launch through the first 5 minutes, was accomplished according to plan. A list of yaw pulses and approximate conditions for each is shown in Table I. The data is difficult to analyze because lateral control was used almost continuously following each pulse. The data does indicate a very low static directional stability at approximately Mach 3.0, and a low value for rudder effectiveness. This was expected at angles of attack greater than 10░ since wind tunnel data shows similar trends. At comparable conditions, the X-15 simulator appears to yield similar results.

5. Approximately 5.5 minutes after launch, the No. 1 APU failed and could not be restarted. As a result of the APU failure and about 30 seconds after the failure, the "ball nose" and the yaw damper servo ceased to function. The pilot had no indication that the "ball nose" had failed since it remained essentially at one fixed position and he did not consciously observe the indicators. The pilot also had no indication of a yaw damper malfunction because the MH-96 FCS yaw channel remained engaged electrically, even though the servo was locked automatically at center because of the loss of hydraulic power. This operation is normal and fail-safe. A failure would have been indicated only if the servo had gone hard over or had moved in the direction opposite to the command.

7. The remainder of the flight and the landing were uneventful and satisfactory.

Elmor J. Adkins

Aerospace Engineer

TABLE I