Flight 3-52-78 was flown essentially as planned by William Dana on July 18, 1966. The flight was flown for the purpose of: a. pilot familiarization, b. checkout of the Honeywell inertial system, c. evaluation of the Lear cockpit display, d. horizontal tail loads determination, e. checkout of the stick kicker, and f. checkout of the third skid.

The inertial system functioned normally during the flight, however, a 5,000-foot difference between inertial height and radar height was indicated during the flight and is being investigated.

Tape instruments of the Lear display functioned normally except for the velocity instrument which displayed a 100 to 200-foot per second oscillation on occasion during the flight. The pilot was satisfied with the tape display. He preferred using the standard clock rather than the Lear clock because of its location on the instrument panel.

Data on horizontal tail loading were obtained at four points during the flight and these data are being analyzed. Two tail load strain gages may have been damaged at touchdown and these are being checked to determine the degree of damage.

The stick kicker appears to have functioned normally, however the pilot indicated he was not aware of stick kicker actuation at touchdown and pushed forward on the stick. The horizontal stabilizers were driven to +15 degrees about 1.1 seconds from main gear touchdown.

The pilot utilized the window shade during the flight and reported that glare was not a problem during the flight. The shade used during the flight did obscure the pilot's outside visibility. A less opaque material for this shade is being obtained.

The third skid was activated for the landing and appears to have functioned normally. The skid did not come in contact with the lakebed at main gear touchdown, however, as the aircraft settled on the main gear during the latter part of the slideout, the skid did come in contact and functioned in a normal manner.

Profile

This was the pilot's second flight in an X-15 and the first flight in X-15-3. The profile was flown essentially as planned with only minor deviations. The launch was normal with about 20 degrees right roll and 4 degrees of sideslip occurring. Engine light occurred at 1.7 seconds after launch. Maximum thrust was attained about 3 seconds after launch.

The angle of attack was increased to 13.5 degrees, dropped to 10.5 degrees, and averaged about 11 degrees during the rotation as planned. Maximum normal acceleration during rotation was 2.1 "g". The desired 30° pitch attitude was reached as planned. Pushover to zero "g" was accomplished as planned.

Shutdown occurred at a velocity of 4,600 feet per second at an altitude of 86,000 feet, and at 95 seconds after launch. Shutdown had been expected to occur at 4,500 feet per second, 80,000 feet, and 98 seconds.

The pilot performed an 11-degree angle of attack pullup, for tail load data shortly after engine shutdown. The yaw damper was switched to fixed gain and a rudder pulse was performed. At about 89,000 feet, the pilot performed a second tail load maneuver. The pilot then rolled to a 95-degree left bank, rotated to an angle of attack of 17 degrees for the third tail load point, and performed a rudder pulse. The pilot pushed over to 1 degree angle of attack, rolled to 57 degrees right roll and rotated to 15 degrees angle of attack for the final tail load point. After passing Cuddeback, the pilot disengaged the yaw damper and performed a rudder pulse as planned. The radar track and profile for this flight are shown in figure 1.

Inertial System Checkout

The inertial system appears to have functioned in a normal manner during the flight. A discrepancy of 5,000 feet between inertial altitude and radar altitude was reported. A study to determine which system is in error is being conducted.

Lear Cockpit Display

The Lear display system functioned normally. The pilot reported a 120 to 200-foot per second oscillation in the velocity tape at shutdown. The pilot had no adverse comments to make in regards to the tape display. The pilot indicated he preferred to use the standard clock rather than the Lear clock because of the attendant with the position of the Lear clock on the panel. The pilot noted the normal acceleration tape and mechanical instruments were identical readings at zero "g". The pilot could not use the 2-inch pressure altimeter.

Horizontal Tail Loads

Four tail load maneuvers were performed during the flight. Data for the tail load program were obtained on angle of attack between M » 3.8 and M » 4.4. A low dynamic pressure pullup of 11 degrees angle of attack was performed at shutdown. The second point was at 89,000 feet. A third and fourth point were obtained during turns with angles of attack of 17 and 15 degrees. The data are being analyzed to determine the effect dynamic pressure will have on the quality. A cursory view of the data indicates that the data will be satisfactory. Two of the strain gages malfunctioned at main gear touchdown. The instrumentation is being checked to determine the cause of the malfunction.

Stick Kicker

The stick kicker was serviced at 850 psi for this flight. The kicker appears to have functioned normally. The pilot indicated he was unaware of kicker actuation and pushed forward on the stick at main gear touchdown. The pitch horizontal stabilizer deflection was approximately -2 degrees at main gear touchdown. At 1.1 seconds after main gear touchdown, the surfaces had been driven to the full up position (+15°). System pressure was observed to be 600 psi after slideout.

Window Shade

The pilot used the window shade during the flight. Glare was reported to present no problem during the flight. The pilot was unable to see through the window shade while trying to observe out the left windshield. He reported this did not hamper his performance but was annoying. The material used in the window shade was more opaque than used in the other aircraft. An attempt is being made to obtain a less opaque material for this window shade.

Third Skid

The third skid was activated for the landing and appears to have functioned in a normal manner. The third skid did not contact the ground during touchdown, however, it did contact the lakebed prior to the time the aircraft stopped. This resulted from the normal spread of the main gear as the aircraft settles on the gear.

Instrumentation Discrepancies

The altitude reference trace on 0-23-36C is off scale from launch +56 to launch +95 seconds.

The MH-95 sample switch recording on 0-21-36C was inoperative during the flight.

The left hand main gear accelerometer on 0-7-36C was noisy during the flight.

The uplock hook (nose gear) strain gage was off scale and will be shunted for flight 3-53-79.

Elmor J. Adkins, Head

X-15 Research Project Office