Click on Picture to enlarge

Click on Picture to enlarge

X-15's first flight  ... A glide to a challenging landing

Scott Crossfield already had years of experience with the X-15 before piloting its first flight. He left NACA to join North American Aviation specifically to contribute a rare combination of skills to shaping the X-15.  He offered the perspective of an aeronautical engineer who already was one of the most experienced test pilots of rocket powered aircraft, as well as early jets.

One of the control effectiveness issues that he raised during design would unexpectedly show itself on the first flight, challenging his piloting skills and threatening to end the flight with a crash instead of a landing.  By June, 1959 the X-15 had completed several captive-carry flights under the wing of a B-52. Some were deliberate, testing system X-15 systems, B-52 systems, and aerodynamic characteristics of both aircraft. Others were aborts, intended to be the first free flight but terminated due to a variety of problems. They ranged from APUs (auxiliary power units) that incinerated themselves to a torn glove on Crossfield's pressure suit. The program was well behind its expected schedule,  everyone felt the need for a successful free flight.

On the morning of June 8, 1959 the B-52 and X-15 went aloft again.  The objective was to do a simple glide to a landing, checking the X-15's flying characteristics for the first time.  All systems looked good except that the pitch mode of the SAS (stability augmentation system) didn't work. On a hypersonic flight this would have been grounds for yet another abort, but this was to be an easy subsonic flight. The decision was to go ahead as planned.

After takeoff the B-52 flew a spiral pattern around Edwards Air Force Base, staying within X-15 glide range of a landing area in case of an early drop.  Rogers Dry Lake was the primary landing site, Rosamond Dry Lake was available as a backup for the western part of the climb pattern.

Click on Picture to enlarge

The first objective was to confirm that the X-15 would drop away from the B-52 cleanly at launch. On the B-52's pylon the X-15 rode in air flow disturbed by the carrier aircraft's wing and engine nacelles, as well as by the X-15 itself. Because the B-52 has swept wings, the X-15's left and right wings experienced different airflow before launch. There was very limited room to avoid damage to both aircraft if the X-15 would pitch up or down, yaw left or right, or roll left or right at the moment of release.

NASA movie clips of first launch: 160x120 15-fps QuickTime 1,352 KB 320x240 30-fps QuickTime 1,055 KB 320x240 30-fps MPEG-1    2,592 KB

Aerodynamic analysis and wind tunnel tests predicted that the X-15 would roll to the right after release but would drop away cleanly if its pitch trim was set correctly.  Crossfield set the trim to 1 degree nose-up in preparation for launch. The B-52 completed its turn onto heading 040 magnetic and quickly closed on the launch point over Rosamond Dry Lake at an altitude of 37,550 feet. With a short countdown, B-52 pilot Charlie Bock pulled the release -- A hydraulic ram in the pylon disengaged three shackles, dropping the X-15 for the first time at 8:38 a.m. and 40 seconds.

Click on Picture to enlarge

The X-15 pitched down and rolled to the right, more than Scott Crossfield expected but little enough to produce clean separation. Following the flight plan, he quickly checked out the new aircraft's handling qualities before re-trimming and slowing. Two more "getting the feel" phases followed -- first slowing to near-stall airspeed, then diving a bit more to accelerate to 190 knots. Here he dropped the flaps for a quick check of flying qualities as they would be on approach, shortly before touchdown. Raising the flaps, he accelerated again to perform the last planned handling tests and to enter the landing pattern. The pilot had to be a quick learner on this flight -- With a glide ratio of about 4:1, the X-15 had only about 5 minutes of flying time available.

Crossfield found that the X-15 handled nicely, though a bit sensitive in pitch due to the in-operational SAS mode. Rounding the turn to final approach, he jettisoned the ventral fin, which parachuted down for recovery.

Preparing for touchdown, he dropped the flaps. Unexpectedly, the nose rose. Trying to recover, Crossfield found sluggish and late response to his pitch inputs.  The X-15 entered a PIO (pilot-induced oscillation), porpoising through large pitch excursions. Crossfield's challenge was to learn in a matter of seconds how to arrest the instability or to time the motion well enough to set down without crashing. The solution had to be found before the X-15's airspeed bled off so far that it would stall, dropping abruptly into the lakebed. Crossfield tamed his bucking aircraft just in time, touching down on the lakebed at about 145 knots (160 m.p.h.). North American's design had anticipated a normal touchdown speed of about 200 knots.

 

 

Click on Picture to enlarge
Postflight analysis showed that the horizontal stabilizers couldn't move quickly enough to track the pilot's control inputs -- once the PIO started the pilot and the aircraft were out of synch with each other. The stabilizers were driven by hydraulic actuators with only enough power to move the control surfaces up to 25 degrees per second. Changing valving in the hydraulic systems raised this limit to 35 degrees per second, and the problem never recurred in the 198 X-15 flights that followed.

 

X-15 GLIDE FLIGHT NUMBER 1

 

Radio communications transcript X-15 #1 First Drop Flight June 8, 1959 Pilot -Crossfield.
Crossfield:	Looks pretty good here. I'm at 33,000, level, 250, oscillatory in pitch, very spongy in roll (Lost him for a few seconds)
Q.C:	Emergency battery off, Scott?
Crossfield:	(back on air) 190. Flaps coming down.
Chase:	Read 175, Scott
Crossfield:	Thank you Bob. Where am I sitting now?
Chase:	Right off Runway 4.
Crossfield:	I see it. I'm at 31,000 feet. 190 indicated. Flaps give very little buffet. Flaps coming up. Very soft pitch. 255-260, 21,000 feet. Roll control is....pitch control is very spongy. Right turn. Too much speed.
Chase:	270
Crossfield:	Buffet. Going to land a little long on the lake.
Chase:	Position here. Just passed 16,000 on my altimeter.
Crossfield:	Roger. I'm reading 15. My heading on that. intersection is 120.
Q.C:	Reminder on lower ventral Jettison.
Chase:	Don't forget to call it please.
Crossfield:	What's my position here? Looks like it might not be so bad.
Chase:	Think you're real good here at 13,000. Reading 240.
Crossfield:	Beginning the turn-in. APUs looking real good. Wish I had guts enough to do a barrel roll here. Feel like I'm back in the saddle again, Buddy.
Chase:	Don't forget your ventral.
Crossfield:	OK wait till I clear the edge of the lake here. Coming off now. She handles nice right along here.
Chase:	260
Crossfield:	Flaps. Trim change. Gear down
Chase:	Take it easy. The gear? About 30 ft. Just hold it steady and set it right there.
(End of transcription)

Click on Picture to enlarge

The flight summary form  from NASA flight log files:

 

Flight plan for X-15 pilot X-15 GLIDE FLIGHT NUMBER 1
TIME  No.	X-15 Pilot Station
1	Recovery
2	Emergency Bat OFF
3	Constant ALT Decel to 165 KIAS (153
4	Kn V min)
5	Handling qualities
6	Longitudinal trim change
7	Accelerate (dive) to 190 KIAS
8	Flaps DOWN (10 sec.)
9	Eval. handling qualities
10	Flaps UP (10 sec.)
11	Accelerate & Trim 250 KIAS
12	Pitch pulse            Limit 0-20
13	Roll pulse              Limit 30 Deg.
14	bank
15	Yaw pulse             Limit 3 Deg.
16	sideslip  Windup turn          Limit 2G
17	Call pattern turns
18	Jettison ventral fin south edge of base
19	Arm switch to ARM - punch jettison button Flaps DOWN Gear DOWN LAND

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Click on Picture to enlarge

Fight plan form for X-15 pilot  from NASA flight log files:

Planned flight path

Note by Milt Thompson on flight 1 (1-1-5)

 

 

 

 

Click on Picture to enlarge

Scott Crossfield, Bob White, and Neil Armstrong flew the X-15 for North American Aviation, USAF, and NASA.  On flight 1 (1-1-5) Crossfield flew the X-15, White flew the F-104 chase plane.

 

 

April 20, 1962

 
Neil Armstrong's reentry skip ...

To the edge of space and to the edge of Los Angeles

Flight statistics:
 

 

Click on Picture to enlarge

Neil Armstrong's first space flights were in the X-15, before he joined the astronaut corps.  His credits included first-flight of the #3 X-15, first flight using the ball nose ("q-ball" air data sensor), and initial checkout of the MH-96 flight controller.  Flight 51 was an MH-96 checkout.

The MH-96 was an experimental adaptive controller on the #3 X-15.  The first two X-15's gave the pilot a right-hand sidestick and a center stick for aerodynamic flight controls, a left-hand sidestick for reaction controls outside the atmosphere, and a separate stability augmentation system.  The MH-96 integrated all of these functions into one device, controlled by the right-hand sidestick.

The MH-96 noted how responsive the aircraft was to aerodynamic controls, using stabilator and rudder to control attitude, and adaptively changed control response to suit flight conditions.  In dense low-altitude air it used low gains:  A given stick movement produced a relatively small control surface deflection.  In the thin air of high altitudes it produced larger control surface deflection for the same stick input.  When the air was too thin for these controls to work it used the same sidestick to operate reaction controls, the small hydrogen peroxide thrusters located in the nose and the wings.  While leaving or reentering the atmosphere it automatically balanced and blended use of the two types of controls.

Flight 51, an MH-96 evaluation, was officially flight 3-4-8:  #3 aircraft, 4'th free flight, 8'th flight altogether, including captive carries and aborts.  The plan called for a step up in altitude to 205,000 feet following the preceding flight's top at 180,000 feet.  The air launch occurred over Mud Dry Lake, in Nevada.

Before launching at 45,000 feet the B-52 and the X-15 encountered unusual turbulence, "the most severe I have had to ride through in the B-52", said Armstrong in his post-flight pilot's comments.  Otherwise, preflight and launch went fairly smoothly.

After launch Armstrong pulled up into the initial climb, reaching 32 degrees nose-high pitch attitude after 35 seconds of flight.  The climb involved a 0 g pushover-over check with the MH-96 in alpha-hold mode (alpha is angle of attack), followed by a pitch-up to return to a 32-degree climb.  Just before the second pitch-up, the speed check at 50 seconds of flight time showed 3,100 feet per second,  2,113 m.p.h.

Climb angle was somewhat in doubt, with aircraft instruments showing 30 to 30.5 degrees while NASA's ground station showed a slightly higher angle.  Armstrong quickly decided quickly to fly the climb at 30.5 degrees as indicated by his instruments and held this angle until engine burnout at 82 seconds.

Precision piloting was essential in X-15 flights.  A deviation of a fraction of one degree in pitch, a fraction of one second in engine burn time, and ordinary variability in rocket engine performance could produce multi-mile overshoots or undershoots in altitude or substantial overshoots or undershoots in speed.  Flights gathering aerodynamic data usually needed both altitude and speed controlled very precisely in order to accomplish their test objectives.  This degree of control was challenging in an aircraft whose acceleration started at 2 g's full fuel at launch and built to over 4 g's as it consumed about 18,000 pounds of ammonia and liquid oxygen, more than its own empty weight.

The X-15 validated Armstrong's decision on pitch attitude by achieving a peak altitude of 207,500 feet at the top of its ballistic arc, a good match for the plan of 205,000 feet.  Speed was also precise, data reduction later showed a maximum of Mach 5.31 on a plan of 5.35.  Armstrong performed a number of stability and control checks to test the MH-96 in air so thin that for all practical purposes it's the vacuum of space.  Air pressure at this flight's peak altitude is about 0.01% (1/10,000) of sea-level pressure.

 

From engine burnout to mid-reentry radio contact was marginal to nonexistent.  NASA-1, the ground station, was inaudible from the X-15 and relays from the B-52 were weak.  Reaction controls worked well under direction from the MH-96, but the excellent attitude control apparently sent more hydrogen peroxide through the thrusters than expected.  As the X-15 descended through about 160,000 feet a warning light came on indicating low hydrogen peroxide supply for the #1 APU.  Armstrong initiated  transfer of residual hydrogen peroxide from the engine turbopump supply, and the warning light extinguished at about 115,000 feet.  At about 90,000 feet smoke poured into the cockpit from above the instrument panel as atmospheric reentry heating burned off paint.

Neil Armstrong did additional stability and control checks as the X-15 re-entered the atmosphere, testing roll maneuvers at high angles of attack (AOA).  He flew about 15 to 16 degrees AOA as forces built to 4 g's.  The MH-96 has a load limiting function that should trip in the range of 4 to 4 1/2 g's, commanding a reduction in pitch attitude to avoid excessive g forces.  In Armstrong's own words...

"I elected to leave the angle of attack in that mode [15-16 degrees] ... it wasn't obvious that we were having any g limiting so I left it at this 4 g level for quite a long time hoping that this g limiting might show up.  It did not and apparently this where we got into the ballooning situation."

Due to maintaining a high angle of attack the X-15 pulled up and essentially skipped off the top of the atmosphere, returning to space.  In this near-vacuum there was insufficient drag to slow it and the wings could not develop enough aerodynamic force to turn it.  Back to Neil Armstrong's description...

"At this point I heard the second transmission from NASA 1. ...I expected from my simulation work 'you're about 20 miles north,' but the transmission I got was "turn hard left."

"...With the left turn command which I followed with 60 degrees left bank angle and 15 degrees angle of attack, I did not properly appreciate the altitude I was at.  I was apparently at an altitude above that which I had expected to be and which caused me to go sailing merrily by the field."

X-15 approaches normally were from the north, with a 360-degree spiral to final approach starting from about 20,000 to 30,000 feet and ending with a touchdown on Rogers Dry Lake.  On this flight the X-15 cruised by with excess energy, too high and too fast to enter the approach spiral. Going south past the base at about 1 mile every 2 seconds, the flight path passed the Mojave Desert towns of Lancaster and Palmdale. Beyond Palmdale are the San Gabriel Mountains, and beyond them is the Los Angeles basin.

"As I saw Palmdale going by I was in a 90 degree bank angle and essentially full deflection on the stabilizers... We were having no heading change.  The proper thing to do at that point would have been to roll to a greater bank angle [than 90 degrees, rolling somewhat inverted] and try to get that thing down to a lower altitude so I could turn faster. However, my indicated airspeed said 190 knots and that seemed from my past simulation experience to be what should have been adequate to turn the heading but it really wasn't.  Finally I did allow the nose to drift down and picked up approximately 350 knots indicated airspeed and was able to get about 3 g at this point."

Click on Picture to enlarge

This point was roughly over Pasadena, La Canada, and the Rose  Bowl, 45 miles south of Edwards Air Force Base!  This is the northern edge of the Los Angeles Basin, on the south side of the San Gabriel Mountains. If not for that 3 g turn Armstrong's next radio contact might have needed to sound something like this:  "Los Angeles Approach, X-15 66672 needs immediate clearance for straight-in approach to runway 25 Right at LAX."

The X-15 was now far to the south of its intended landing site but was at least pointed back toward the Mojave Desert.  The X-15's lift to drag ratio is about 4:1, and glide ratio = L/D:  It will drop one mile for every four miles it travels when its speed is steady.  The normal landing area on Rogers Dry Lake was out of range, so the new challenge is to choose an alternate site that can support a high-speed landing and a long ground run.

Armstrong quickly considered and rejected the long runway at Palmdale, El Mirage Dry Lake to the east, and Rosamond Dry Lake to the West.  He settled on stretching his glide to the south lakebed at Edwards.  Two chase planes joined up as Armstrong was lining up for a straight-in approach, aiming for the middle of the south lakebed. The farther they went, the shorter it seemed the glide would be.  The X-15 finally landed successfully on the lakebed -- and when one of the chase pilots was asked how much clearance there was with the Joshua trees at the edge of the lakebed his answer was "Oh, at least 100 feet ... on either side".

The flight ended 12 minutes, 28.7 seconds after it started, the longest X-15 flight of the entire research program.
 

    Pre-launch checks were satisfactory with no discrepancies outstanding.  The MH-96 airborne analyzer check was completed without failure with the exception or a temporary failure indication on center stick, fixed gain, trim output. The analyzer performance was particularly commendable in view of the fact that the B-52/X-15 combination was encountering severe turbulence with significant roll and yaw excursions during the entire analyzer operation.  Inasmuch as normal Doppler operation was never achieved, NASA 1 predicted inertial velocity would include a small error.

    The launch was performed with 4° left roll differential stabilizer, the trim value with the MH-96 flight control system engaged.  Right roll at release was moderate with a total bank angle change of approximately 20°.  A 100% throttle start provided smooth engine ignition with no significant transients. The pullup was performed with 3 units of side stick, nose-up, rate trim. Angle or attack during the pullup varied between 7 and 10 degrees.  Roll hold was engaged at approximately 1500 fps without transient.  Pushover was accomplished with full nose down trim (side stick) at 35 seconds and approximately 31° pitch angle.  Angle or attack after the pushover had been stabilized varied from 0 to 2 degrees.

    Inertial velocity at 50 seconds indicated 3100 fps (about l00 fps over predicted).  Inasmuch as engine chamber pressure (570 psi) was below predicted (590 psi), engine thrust, acceleration, and total velocity should be slightly low.  It was therefore assumed that inertial velocity was in error as predicted and was indicating slightly high.  It was decided to perform engine shutdown at the planned time ( 81 sec. ) insuring no over velocity.

    The second pullup was performed with 5 units or nose-up trim at 55 seconds.  Trim was reduced to zero as the specified 32° pitch attitude was approached.  Pitch attitude hold was engaged without significant transient. Longitudinal damping at this flight condition (V=4500 rps, h=100,000 ft) was particularly good in opposition to the simulator predictions.  Reaction control energizing was selected in the automatic mode and was not detected; hence it is not known whether some of the damping can be attributed to reaction controls.

    Flight path angle was reported to be slightly steep at 75 seconds although pitch attitude was 1° low (31°).  Q was maintained at this value through shutdown at 81 seconds.  Indicated inertial velocity at shutdown was 57-5800 fps and was suspected to be indicating several hundred fps high.  Radio reception subsequent to this point throughout the high altitude part of the flight was intermittent. Voice relays through the B-52 were partially successful.

    Control stick steering was used to reduce the angle of attack to near zero at which time the angle of attack hold was engaged without transient. Cross checks of inertial altitude and inertial vertical velocity indicated the trajectory to be precisely as planned. Inertial altitude at the trajectory peak was indicated to be 210,000 ft.  The pitch attitude outer loop was reengaged at this point, and was accompanied by a slight shudder through the fuselage.  Yaw and roll overpowers were performed on both a and Q hold. The returns were at modest rate with little evidence of overshoot. Overpowers on the aircraft require considerably more stick or rudder deflection for a specified aircraft motion than on the simulator.

    Angle of attack hold was engaged at 175,000 feet and approximately 15° alpha, and was again accompanied with a slight shudder.  The angle of attack reference was increased to 21° with the venire.  Roll overpowers were performed with the airplane response again being more sluggish and accompanying sideslip excursions less than one half the magnitude of the simulator.

    In general, aircraft control and damping during ballistic flight and entry were outstanding, and considerably more smooth than had been expected. Unfortunately, this may be at the expense of excessive reaction control fuel consumption.  The #1 APU/BCS H2O2 low lite was illuminated at approximately 160,000 feet during the descent.  The H2O2 transfer system was immediately energized and the light was extinguished at approximately 115,000 feet.

    The control stick steering button was engaged at 120,000 feet to resynchronize the outer loop references.  Some attitude drifts were experienced during this period.  While normal acceleration was increasing to 4, angle of attack was reduced to 16°.  This value was maintained in an attempt to observe the "g" limiting function in operation.  Such limiting was not observed.

   Although speed brake extension and angle of attack reduction were thought to be performed as scheduled, it soon became obvious that some positive flight path angle had been achieved subsequent to the entry completion.  This flight condition (v=4,000 fps, h=85,000 ft, gamma= +), compounded by an entry completion 20 miles further down range than predicted, created a situation which precluded the completion of the flight path as planned.  A sizeable overshooting of the space positioning turn required a straight in approach to an alternate runway (35).

    Handling qualities during the flare were considered to be less desirable than on previous similar approaches.  Large stick motions were required and response in pitch was sluggish.  Flight data indicated the control system gains had been driven to low values.
 

       Flight: 3-4-8
  Pilot: Neil Armstrong

Takeoff -- during the prime, the cooling procedures didn't apparently. work quite as well as they had on our previous flights. The analyzer check and the flight control system was satisfactory.  I chose not to re-examine item 8, which had a temporary failure because of center stick trim. I really wasn't very concerned that it showed a temporary failure, it indicated that we were quite close to where we needed to be and there wasn't any use worrying about it. I was sure that the analyzer would never pass anything while in the turbulence we were encountering at the time, which was the most severe that I have had to ride through in the B-52 and it was an altitude of 45,000 feet. We had sizable gust loadings and side slips throughout as a result of these.

In the pressurization and jettison check I had every intention after the lesson of last flight of putting the peroxide jettison switch to stop at the completion of that check, and I neglected to do it. Pump idle was smooth with few oscillations. The size of the pressure was pretty sizable though about 390 or so manifold pressures and pump idle were solid. The light was good. I was surprised that the chamber pressure wasn't as high as we had seen on the ground run. I called it out somewhat later in the flight around 575 or something like that. It was about 20 pounds below what I had seen before.

I made the pullup on trim. 3 units of nose-up trim on the side stick. This seemed to be a little bit slower than it had been on the simulator. I got to the pitch attitude at 32° after 35 seconds of flight, if I remember correctly. I put the pitch rate trim to zero at  theta = 32°. and I was reading Joe fine at this time and pushed over at 35 seconds. At 50 seconds, which was our speed check point, we were indicating 3100 feet per second inertial and about 65,000 or 70,000 feet in altitude, which was very close to what we had expected at that point. I pulled up on Joe's count of 55 seconds with a pitch rate trim of 5 units. This was also somewhat slower than it had been on the simulator. I had engaged roll hold earlier at 15 seconds without transients. I engaged theta hold at approximately 70 seconds, without transients. The airplane flies 100% better than the simulator on this theta hold. The simulator had indicated that the airplane pitch damping at this condition would be poor but it was not. Damping on all axes was good. I had 81 seconds on my clock, maybe one second before when it was called on the ground. I shut down on my clock so I was in the cutoff position about the time that I got the call from the ground, 81 seconds. You indicated I was slightly steep on profile and my indications were that I was about 30 to 30-1/2° at this time. Since we had a difference of opinion on what our condition was I chose to leave it at 30 -1/2 ° for the burnout and that's the condition we were at instead of the 32° that we had planned. Rather than make a little correction downward when you said I was a little steep or upward from what I indicated, I took the happy medium. I engaged alpha hold and used CSS to reduce alpha and then alpha trim a little to reduce alpha to zero. That operation was all satisfactory.  I put in several pulses and control steps in the area of the peak altitude and noted that the airplane did not move as far in heading, side slip, or roll attitude for the same stick deflections as we had seen on the simulator. I was aware that the reaction controls were working satisfactorily although there was no apparent noise. The reaction control damping is exceptionally good. It flies as good as the airplane does on aerodynamic controls at low altitudes. But, obviously. at the expense of a considerable amount of peroxide.

I read about 5700 ft/sec at engine burnout. Since the velocities were predicted to be fairly good and we had indicated slightly fast on the 50 second point, it was assumed that this was about right or possibly reading a little fast. We have had performance to 5700 ft/sec on the simulator for 82 seconds of burning. The altitude rate on top and the inertial system was 210,000 feet and cross-checks of the inertial system indicated it was working satisfactorily.

During this time period, after 81 seconds, I didn't receive any transmissions from NASA 1 and didn't receive any transmissions from that point until the middle of the entry. I did receive a number of transmissions through relays. I'm not quite sure who it was but these transmissions were weak, about strength 2 and modulation 3 to 4. I might say that I did some specified roll maneuvers at about 20° angle of attack and the returns were satisfactory. The airplane returned to the wings level attitude with essentially no sideslip. At about 15° or 16° angle of attack and 4 g, I elected to leave the angle of attack in that mode and I was hoping that I would see the g limiting in action. We had seen g limiting on the simulator operation at levels approximately 4 g to 4-1/2 g and it wasn't obvious that we were having any g limiting so I left it at this 4 g level for quite a long time hoping that this g limiting might show up. It did not and apparently this is where we got into the ballooning situation.

At this point I heard the second transmission from NASA 1. The first one that I heard from NASA 1 was, I believe, when he called out some angle of attack which I correlated with and I think he mentioned a similar reduction but I'm not sure. The next transmission I expected from my simulation work was "you're about 20 miles north," but the transmission I got was "turn hard left."

We had planned on going down to 6° angle of attack in this area, and have a little time on the way in for the last 20 miles to build up the q, kill off a lot of altitude and get some pulses on the adaptive mode. With the left turn command which I followed with 60° left bank angle and 15° angle of attack, I did not properly appreciate the altitude I was at. I was apparently at an altitude above that which I had expected to be and which caused me to go sailing merrily by the field. As I saw Palmdale going by I was in a 90° bank angle and essentially full deflection on the stabilizers, between 25° and 35° on the stabilizer indicator. We were having no heading change. The proper thing to do at that point would have been to roll to a greater bank angle, greater that 90° bank angle and try to get that thing down to a lower altitude so I could turn faster. However, my indicated airspeed said 190 knots and that seemed from my past simulation experience, to be what should have been adequate to turn the heading but it really wasn't. Finally I did allow the nose to drift down and picked up approximately 350 knots indicated airspeed and was able to get about 3 gat this point. I began to turn back home and it looked at this point as though I would have no difficulty making Edwards. The only other alternative at that point would have been Palmdale and I didn't want to get into their traffic pattern. Mirage Lake was about as far away as Rogers and Rosamond wasn't much closer, so I decided to head for the south lake. It looked like we were in good shape. I jettisoned then and again it didn't occur to me to stop peroxide. I had promised myself that I was going to have peroxide in a stop position but I did not. We threw a lot of peroxide away that we would have had available for the transfer system.

The impression that I had as we approached the field was that the airplane wasn't making good the L/D that we had practiced in 104 approaches around Edwards. I was flying at approximately 270 knots and had I suspected that we would have been tight.  I would have jettisoned the ventral but it didn't even occur to me that we might be tight. As we approached the field however, I found out that my aiming point that I had selected would have to be moved back approximately 2 miles from where I had originally picked it up. In coming further out down here I lost approximately 2 miles in length from what I thought I would have. I may have had a control condition at this time which I did not know I had. When I was in the flare I found that I had to use large pitch motions on the stick and it was a real sloppy flaring touchdown. This leads me to believe that possibly I was overpowering pitch attitude hold or had normal acceleration feedback, or something in the system. We will have to check that. It was a pretty sloppy flare and a slow touchdown, probably 165 knots, something like that.

Q Do you recall turning off the alpha Hold after the entry?

P.C.: No, I don't remember. It points out the need for something that I thought might be a valuable addition to the flight control system. This would be an outer loop disengage switch. I think we should consider this, someplace where we could get at it from the stick.

Q How about on the ventral jettison switch?

P.C.: Well, that would be an idea certainly for landing. There might be other times when you would want to use it also. It's something to talk about.

Additional unrelated comments are as follows :

1. Smoke was observed emanating from above the instrument panel at 90 ,000 feet during the entry.
    
2. The newly installed FCS indicator lights operated satisfactorily but can be considered only a temporary 'fix'.
    
3. The stabilizer position indicator operated satisfactorily and was readable at all times. It is considered to be a valuable addition to the panel.
    
4. Radio reception at high altitudes was generally unsatisfactory.

NAA:bjc
JRV
.

Click on Picture to enlarge

Copy of final comments document

Click on Picture to enlarge
Flight summary form	Planned flight path	Flight 51 request form:   page 1:
Flight 51 request form:  page 2:	Flight 51 request form: page 3:	Neil Armstrong after landing on an earlier flight in the #1 X-15...

A note on significance of this flight, excreted from From Runway to Orbit, by Ken Iliff and Curtis Peebles.  Dr. Iliff served as Chief Scientist at NASA Dryden for many years before his retirement

 

The actual flight path mapped in red on this web page is reconstructed from information in the map of the planned flight path, the pilot's post flight notes, the radio communications transcript, and additional recent comments offered by the pilot, Neil Armstrong

This author derived the shape of the turn over the San Gabriel Mountains and the northern part of the Los Angeles Basin by graphically rotating and reflecting the ground track from the only surviving radar plot of an X-15 mission. That mission was Bob White's FAI altitude record flight, which also finished with an overshoot of the landing site. White passed Edwards AFB at about 60,000 feet and Mach 3, Armstrong passed at just over 100,000 feet and Mach 3. Both used similar control inputs and aircraft attitudes to produce a 3g turn for the return to Rogers Dry Lake. In both cases this was a windup turn, with radius decreasing as the X-15 descended and slowed.

Accuracy of this reconstructed plot of the flight path cannot be confirmed in the absence of actual radar data, and even the pilot is unable to provide precise visual information because downward visibility from the X-15 cockpit is quite limited. However, the combination of details in the flight log and constraints inherent in the physics of flight provide high confidence that the derived plot has fairly good accuracy.

Thanks for information used to produce this flight path reproduction go to Neil Armstrong, Major General Robert M. White, Ret., and the NASA Dryden History Office. General White also flew as a chase pilot on this mission.

 

Click on Picture to enlarge
X-15 flight envelope, charted from -3 G to +8 G at speeds up to Mach 3.5	A well-known benefactor of X-15 technology, Space Shuttle orbiter Discovery returns from orbit to NASA Dryden at Edwards AFB

The X-15 research program was the last major investigation of hypersonic and high altitude flight by a manned aircraft. Four decades later, engineers and researchers still use data gathered by the X-15 as a state-of-the-art reference for hypersonic aerodynamics.
 

The X-15 pioneered research leading directly to manned space flight. It explored

• New territory in aerodynamics, including validation of computational models for hypersonic research and design
   
• Hypersonic stability and control
   
• Severe aerodynamic heating and flight at record-high dynamic pressures
   
• Rocket propulsion, including the first man-rated throttleable rocket engine
   
• Novel systems engineering throughout its airframe
   
• Pilot life support systems for hypersonic flight and space flight, including the first true space suit
   
• Control systems and human interface technology for hypersonic flight and space flight
   
• Support systems, procedures, and organizations.  Many were essential for safety of flight. The High Range was a major project to provide tracking and telemetry reception in real time during X-15 flights.
   
• Other high-altitude scientific research, carrying instruments to the edge of space
   

Over time this web site will add separate pages with more detailed descriptions of these areas, with links to those pages to be added in the list above. A few additional links will lead to more detailed examples of particular technical challenges and innovations. The first such examples probably will be...

• Windshields: How to handle everything from frost to cracking from heat stress and ablative fogging
   
• Nose landing gear: How to handle complex requirements with a simple system and keep it from popping open at Mach 4
   
• Main landing gear: "Hitting the skids" and why control inputs at touchdown should be the opposite of what's appropriate in "normal" planes

USE YOUR BROWSER "BACK" BUTTON TO RETURN TO PERVIOUS PAGE