Flight No.: 3 Launch: 1551
Plane: X-15 No. 1 Land: 1542
Number: 670 Total: :09
Pilot: J. A. Walker
Chase: S. Crossfield
Major R. White
John B. McKay
This flight was the initial flight with the X-15 aircraft by an NASA pilot. Numerous mechanical difficulties were experienced in the course of attempting to get this particular flight launched. In the morning the flex section of the liquid oxygen topoff pipe in the B-52 pylon was found to be cracked and leaking which necessitated replacement so that the intended 8:00 A.M. takeoff of the B-52 and the X-15 was delayed until approximately 2:40 in the afternoon. Some of the things that developed as a result of the late takeoff were mostly due to sun beating down on the X-15. It was discovered that the cockpit was extremely warm, hence the maximum ventilation flow was barely adequate with the pressure suit. However, the warmer temperature also alleviated the hydraulic cold temperature problem.
The cockpit check and taxi and takeoff and climb portions of the flight proceeded without any undue difficulty or unusual unknowns arising. There is no question but that the pylon arrangement and B-52 for mother ship is of several orders of magnitude improvement over the bomb bay B-29 system used for previous research aircraft. In the course of the final parts of the climb the electrical power supplied by the B=52 failed and this is believed to have been caused by a separation of the umbilical plug at the pylon fitting. This problem necessitated starting up No. ! APU in order to furnish electrical power to the X-15. Communications were not lost due to the B-52 power failure inasmuch as the interphone arrangement functioned as intended.
The stable platform was not used as a warning light in the B-52 launch panel control mechanism for the stable platform indicated that it was not feasible to go ahead and erect the platform, so the flight was made using the standby attitude indicator. After the left turn to base and the power off deceleration the standby attitude indicator showed 45° left bank when aircraft was level. The original approach to a launch position went as planned, however, the pilot in the course of reading some pressures missed some of the final time checks and was not ready for launch when the time came. This difficulty was aggravated by intermittent loss of communications which were not detected at the time it was occurring inasmuch as some transmissions would come through normally. So we made another pattern and came on in and launched. This apparently probably established a minimum operational launch condition for the nitrogen gas supply for the engine control and bleed and the engine peroxide supply. This was about 1800 lbs. source pressure at launch.
On launch the aircraft snapped abruptly to the right approximately 30° and was righted immediately by the pilot who proceeded to start up the rocket engines. The lower engine lit off OK and we got all four chambers lit immediately on that engine. However, the upper engine on the initial starting attempt went out in overspeed. Upon reset and attempted restart it again went out in overspeed, the third attempt was successful and the flight continued on 8 chambers.
We knew before launch that we had no roll damping. This made the aircraft somewhat sensitive laterally and there was some continuous small lateral oscillation which was not objectionable and could be avoided by some detailed attention.
The roundout to climbout was made at 9° angle of attack and the climb continued at about 7 1/2° angle of attack. Level off for acceleration altitude was started at 45,000 feet and completed early at about 48,500. Pushover minimum normal acceleration was 0-2g. Noticeable increase of airplane nose up control was required M 1.3 to 1.45. Due to the delay in getting the second engine started we were approaching our must-turn location so that the turn was started at about 1.45 M and 48,000 feet. Some altitude was lost in the turn but the heading for the next leg was picked up at about 47,000 feet and approximately 1.55 M. Full deflection left rudder was applied and abruptly released. The airplane oscillated laterally, it damped fairly well directionally, but the lateral oscillation was very lightly damped. The aircraft was observed to be approaching M 2.0 and the yaw gain was cut down to one by gain rheostat and the directional pulse was made. This was still well damped even without yaw, yar, or roll damper, in the directional mode. The gain was turned back up to 8 on yaw. At about this time the power was cut back to 5/8 thrust and we had achieved M 2.00 at about 47,000 feet. A left turn was made and in the midst of this the pitch gain cut to one and a pitch pulse made, on top of the acceleration for the turn. I don't believe this was too good a pulse inasmuch as I was somewhat busy in the cockpit keeping track of the position of the airplane as well attempting to hold a steady condition during the pulse. Burnout occurred during turn at pitch SAS gain at one. After burnout the aircraft was straightened out in a heading back to base. Pitch gain was returned to 4. At 280 kts. which was about .9 M the flaps were lowered in order to evaluate some small control inputs with the flaps down from 280 kts. down to about 190 kts. indicated. No unusual characteristics were noted handling, wise. Increasing stick deflection for same aircraft response was noted as speed decreased. It was observed that the flap deflection necessitated; forward motion of the stick in order to maintain aircraft longitudinal attitude. Flaps were retracted and glide set up in order to position the aircraft for a landing on the south lakebed. We wound up about 30 000 feet over the base so speed brakes were extended in order to kill off some altitude. However, to be conservative, this was not continued beyond about 25,000 feet and the rest of the pattern was set up for the landing. As a result of being high all around the pattern the speed was increased to about 340 kts. on the last part of the final turn and the straight in approach. No apparent benefit of increased drag was observed. L/D is higher than expected. The tail fin was jettisoned over the south lake and the rest of the approach flown utilizing a pullout initiation at 3800 feet MSL for establishment of final glide angle and lowering of flaps as soon as the glide angle had been established after the initial flare. After reaching the vicinity of about 200 feet to 300 feet above the ground the gear was lowered and the landing continued to touchdown. Touchdown was no problem and occurred about the 5 1/2 mile mark on south lakebed runway 35. Wind of approximately 15 kts. from the south-southwest was blowing at the time and introduced no particularly noticeable problem to the airplane at touchdown.
After observing that the glide speed was well in hand attention was concentrated on keeping track of height above the ground and hence the exact touchdown speed was not observed but should have been in the vicinity of approximately 200 kts. judging by the apparent ground angle. Initial skid contact is barely noticeable. However, the crash when the nose gear hits the ground leaves no doubt that you are on the ground. After all gear was on the ground left stick was used as the aircraft was observed to be drifting slightly to the right and this for a while tended to reduce the amount of right turn during the ground slide. This soon lost its effectiveness and some left rudder was introduced which immediately was observed to be incorrect, and was taken out. Speed brakes were extended during the slide in order to cut down some on the distance.
All the systems worked very well except the roll augmentation and the stable platform. In fact, having gone through several ground runs on APU and the engines, it was quite pleasing to observe prior to launch and during the flight that the systems pressures and operation was coming out identical in flight to what we had experienced on the ground. The upper engine overspeeds were caused by long pressurization and short prime.
This aircraft has good handling qualities especially in those axes which were augmented. Not as much sideslip was generated as had been expected during the sideslip. The roll axis was not as sensitive without damping as had been expected from previous simulator experience. The longitudinal stick force, which was the original bungee, not the 30% stiffer bungee which is in the No. 2 aircraft, was considered to be OK except when attempting to use large excursions of the stick from the trim position when it becomes noticeably high on stick force. Therefore I do not believe it necessary to increase the stick force. During the flare for the landing the pitch trim change associated with the extension of the flap was encountered but this was counteracted easily by forward motion of the stick and once the initial input was made the longitudinal control was again straightforward.
I think we have a real good airplane here and we should be able to prosecute the research program without undue drawback.
Joseph A. Walker
Aeronautical Research Engineer