Flight 3-62-92 was flown on August 25, 1967, by Major Michael J. Adams for the purpose of obtaining data for:

Two significant malfunctions occurred during this flight. The engine did not start on the first attempt, thus requiring a restart. This malfunction was caused by a spurious vibration signal. Engine vibration pickups, amplifiers, and connecting cables have been replaced.

Approximately ten seconds before touchdown, the IFDS and the ball nose malfunctioned. Postflight examination revealed a tripped IFDS circuit breaker, which would cause a power loss to the ball nose and inertial system. Investigation as to the cause and correction of this malfunction is proceeding.

Flight Track and Profile

The radar track and profile for this flight are shown in figure 1. The ground track was essentially on the planned track.

The flight profile, as shown in figure 1, was approximately 3000 feet lower than planned. However, the pilot commented that the inertial presentation was indicating the planned altitude during the constant altitude portion of the flight after shutdown. An analysis of the flight data is proceeding to determine where the discrepancy exists.

Stability and Control

A time history of the significant stability and control parameters telemetered during the flight is shown in figure 2. The launch, from Hidden Hills Lake number 1, was normal with 15° of right roll and 3° of sideslip. A spurious vibration signal, occurring approximately simultaneous with launch, prevented the engine from igniting on the initial attempt. The pilot performed the normal restart sequence and engine light occurred 16 seconds after launch and reached 100 percent thrust in 1.1 seconds. Rotation after launch initially peaked at 20° angle of attack indicated (13.7° true) then lowered to approximately 9° average, as compared to the planned 10°. This was due to rotation being performed at a 2 "g" maximum normal acceleration. Limit cycle in the MH-96 system also occurred during rotation, but this was expected as the dynamic pressure had built up to 1500 to 1600 psf. The planned pitch attitude of 20° was attained 36.2 seconds after launch.

Based on experience acquired from simulator work, the pilot elected to initiate a pushover maneuver to 1° angle of attack at h = 800 fps rather than 57,000 feet altitude. This maneuver came at 53,500 feet, approximately 44 seconds after launch. The planned 1° angle of attack was attained and held until V = 3900 fps was reached. At V = 3900 fps a left roll maneuver of approximately 85° was initiated in preparation for a data point to be obtained just after engine shutdown.

Engine shutdown was initiated at 4500 fps as planned and occurred at 4600 fps after 71.3 seconds of powered time. During the glide back to Edwards four horizontal stabilizer loads maneuvers were performed and computed angle of attack and angle of sideslip were checked. During the final approach the ball nose apparently malfunctioned. The landing and roll-out were normal and the pilot executed an unassisted exit from the aircraft after completing post landing checks.

A time history of the airplane weight is shown in figure 3, and of the longitudinal center-of-gravity position is shown in figure 4 . The calculated landing weight was 15,150 pounds with a longitudinal center-of-gravity position 20.5 percent of the mean aerodynamic chord.

Boost Guidance

The Ames Research Center's Boost Guidance experiment was originally scheduled for this flight. However, problems developed in the ALERT computer during laboratory and programming checks of the computer which could not be resolved prior to the flight. Thus, the computer was not installed for this flight. The discrepancies are in the process of being corrected and the computer is scheduled to be on-board for the next flight.

Horizontal Stabilizer Loads - Phase II

A total of four maneuvers were performed in conjunction with this experiment. Only one of these was a scheduled horizontal stabilizer loads maneuver. The other maneuvers were to investigate buffet and angle of sideslip excursions experienced on two previous flights.

The horizontal stabilizer loads maneuver was initiated at engine shutdown at approximately 4.5 Mach number. The maneuver constituted a rapid pullup to 11° angle of attack and approximately 3.0 "g" normal acceleration, then a pushover to approximately 0.0 "g" and holding until peak altitude was obtained.

Three maneuvers to investigate buffet and beta excursions, experienced during the Phase I portion of the horizontal. stabilizer loads program, were performed at Mach numbers of 4.0, 3.7, and 2.5. A pullup to approximately 12° angle of attack was made at each Mach number. No buffet or beta excursions were experienced at the two higher Mach numbers, but at M = 2.5 results similar to those on the two previous flights were experienced. A beta excursion of about 3° was recorded but the pilot was not positive if buffet occurred during this maneuver. Buffet had been experienced at 10.5° on the previous flight. The only configuration change between flights was the replacement of the "Phase I" horizontal stabilizer with the "Phase II" horizontal stabilizer. The "Phase I" horizontal stabilizer will be installed for the next flight.

Data obtained on this flight is being analyzed and a complete analysis will be made before the "Phase II" horizontal stabilizer is flown again..

Boundary Layer Noise

Four l/2 inch Photocon microphones were installed on the side fairing at location 1 for this flight to obtain additional boundary layer noise investigation data. Acceptable data were obtained and are being analyzed. This experiment will be removed prior to the next flight.

Cold-Wall Heat Transfer Instrumentation Checkout

Difficulties in data acquisition experienced during the three cold-wall heat transfer flights resulted in an investigation of the cause of these discrepancies. This instrumentation checkout is a part of this investigation. An analysis of the data obtained is being made to determine its quality and acceptability. If required, checkout of this instrumentation will be conducted on future flights, however, these data will not be recorded during the next flight.

Data System Discrepancies

During the final approach portion of the flight, 8.2 seconds prior to touchdown, telemetered data indicates the ball nose malfunctioned. Postflight examination revealed a tripped IFDS circuit breaker, which would cause a power loss to the ball nose and inertial system.

The following discrepancies were noted on the PCM Sub-Commutator:

#4: Ch. 4-13 and 4-17 Shifted during flight.

Ch. 4-53 No movement.

Ch. 4-22, 4-23, 4-33, 4-34, 4-36, 4-46, 4-66, 4-67, 4-68, 4-69. Malfunctioned.

Channel 67 on the Prime Commutator: Non-functional. This channel was stowed for flight.

These problem areas are being investigated to determine their causes and the steps necessary to correct them.
 
 

Operations Discrepancies

The engine did not start on the initial attempt after launch, thus requiring a restart which was successful. Analysis of data indicated this malfunction was caused by a spurious vibration signal which occurred approximately at launch. Engine vibration pickups, amplifiers, and connecting cables have been replaced as corrective measures. A static engine run will be performed prior to next flight as a functional checkout of these changes.
 

E. J. Adkins, Chief

X-15 Research Project Office