X-15 Flight: 3-11-20
October 23, 1962
Pilot: Major R. A. Rushworth
2. Maintain 2g until q = 32°, maintain q = 32°.
3. Pushover to a = 2° (g = .2).
4. Shutdown engine, set yaw damper '"OFF," Roll damper "Fixed." Perform dv pulse.
5. Pullup to a = 15°, perform dv pulse.
6. Peak Altitude - pullup to a = 15° at pilot's discretion, perform dv pulse at pilot's discretion, set roll damper "OFF."
7. Extend speed brake, perform dv pulse. Use a Hold as desired.
8. Trim to a » 10°, perform dv pulse.
P.C.: The launch wasn't quite normal, I was released by the B-52.
B. Discuss the magnitude of roll at drop, and the control required to recover to wings level attitude.
P.C.: The roll off at launch didn't seem to be any worse than anything I have experienced. I was holding enough aileron deflection to keep it within reason.
C. Was a 2g rotation made?
P.C.: I didn't do the 2g rotation. I just pulled up to about 14°a and just settled back to 12°a. I got a pitch pulse in that first 20 seconds of flight and got that little vibration.
D. Discuss any unusual or distracting factors during drop and rotation.
P.C.: Nothing unusual on the drop, and on the rotation. When I got the attitude established and started up, I had to shield myself from the sun, and it was the glare of the sun on the face plate that made the visibility to the instrument panel less.
E. Rate pilot task during drop and rotation: q 1.5 , f 1.5 , y 1.5 .
F. Discuss and rate the task to achieve q = 32°. q 2.5 , f 1.5 , y 1.5 .
P.C.: I'm not sure what the sequence was, but I saw the pitch vernier coming down and in the airplane, it seems to be closer to the null attitude before it begins to move. It doesn't give you as much lead time, so when I saw it start to move, I just gave it a little jab on the stick, and it stopped right away. Then I let it come on down again. I was planning to hold it and trim. In the process, I went up to about 2 or 3° higher, perhaps to 35° and then got it back down to 32°. It is still a little more difficult for me to do this with the Minneapolis system than it is with a straight system
P.C.: The first cycle in q was ±4°, and the second cycle was ±1/2°. I got it down after the second cycle.
B. Rate the pilot task during climb; q 1.5 , f 1.5 , y 1.5 .
C. Discuss any difficulties in pushing over to a = 2°; did you overshoot a?
P.C.: I don't think I missed the 2° by more than ±1/2° all the time I was working with it.
D. Was g = 0.2 difficult to hold during pushover?
P.C.: The 0.2 g is kind of difficult to pick out since the g meter is blocked off between ±1g by the 3 lights and the bracket, for the hold mode lights.
E. Were any burnout transients noted?
P.C.: I didn't notice any burnout transients. As a matter of fact, I got back to 50% thrust and I'm pretty sure that I shut it down because I did get a definite deceleration.
Question: Did you notice any yaw during the climb with power on?
P.C.: No. No oscillation that I could see, and I couldn't feel anything.
F. Did the aircraft react when the damper settings were changed at burnout? If so, how?
P.C.: There was no reaction from the airplane when the dampers went to fixed gain. I don't think there was any reaction when the yaw damper went off, although I felt it go off. I could feel the system clank. There was a very definite change when I shut off the roll damper. I heard it, and then I felt it, and then when I flipped the roll damper back on, it was more powerful. One thing here, I'm almost positive as I was getting snaps and bangs from the airplane expanding and contracting, that one or two of these things did have some affect on the airplane. Now, where they came and when they came I don't know, but I'd hear bangs and I'd feel the airplane moving, and I had to react to it. One time it seemed to make the airplane move, kind of like a gust input or something like that. It may have been that I'd get a bang just about the same time I'd shut the dampers off. Now, whether or not this is true, I don't know, but it sure seemed like when I heard a bang one time the airplane reacted to it.
P.C.: The rudder pulse at 2°, 5,500 ft/sec., it was in that neighborhood probably 5,400 ft/sec and was pretty much as I expected from looking at the simulator. I didn't hit it too hard, and I didn't get very much reaction from it. The needle swung over and back, probably less than ±1/2°. It was about the same frequency that I got from the simulator with adaptive dampers on. How this would have been closer to 3° than the 2°, and it might have been 3-1/2°.
B. Was the pullup to a = 15° executed smoothly? If not, comment on the difficulties encountered.
P.C.: Okay, pullup to 15°. I think I did this in a couple of steps. I got up to about 10° and slowly got it up to 15° and no problems. The simulator had given me pretty good warning of the amount of damping that I would have there, and I could very easily overshoot. As a matter of fact, on the simulator 50% of the time I was going to 18° trying to stop it at 15°, but there wasn't any difficulty here. I think perhaps, it was because I came up real slow. I had started pulling it up with a rate of climb still at 200 ft./sec .
C. Describe the response of the airplane to the da pulse at 15°a.
P.C.: When I got there, I shut the yaw damper off and gave it a small pulse, and I don't think that the airplane responded as much as I expected it: to. This could have been that I didn't put in a strong enough input also. The roll damper was fixed and the yaw damper off . It didn't concern me at a11, and I figured it was at least as good as what I'd seen in worse cases on the simulator.
Question: You didn't try a rudder pulse at all?
P.C.: No. I wasn't going to get anything out of the rudder, unless I'd put it in and held it.
D. At a > 15° da pulses were to be done at the pilot's discretion. Discuss the results of these pulses, and rate the task to retrim the airplane.
P.C.: I didn't get anything above 15°.
E. If da pulses were done with the roll damper off, discuss the results in terms of airplane response and pilot's control task.
P.C.: Now, part E, with the roll damper off: we get into the out of trim condition. Both here and before I tried to get the pulse and get my hand off the stick. I think I got the pulse as I was bringing the airplane back to level flight with the dampers on adaptive, zero, zero. I saw the airplane rolling over so I stopped it and started back and tried to get a little pulse. I don't think it responded very much because as I took my hand off the stick, it came to a stop and started to drift back to the left again, so I put my hand back on the stick again just to hold it. I think at this point, I just left it in the turn and put the speed brakes out. No problem with bringing the speed brakes out.
F. Rate the pilot task to retrim the airplane following the da pulse with roll damper off; q 2 , f 2 , y 2 .
P.C.: Pitch didn't seem to be any problem because it wasn't being upset. Roll wasn't any problem mainly because I didn't have to do anything but hold a constant force against it, but it might have created a problem if I'd had to maneuver. The roll seemed to be as responsive as I'd seen it in the simulator, but the period seemed to be a little longer, and the damping seemed to be less. These ratings for F were pretty much from a static condition. I wasn't changing conditions at all there, so it was just a matter of holding what I had.
G. Compare the aforementioned maneuvers with the simulator and rate;
Flight q 2 , f 2 , y 2 .
Simulator q 2 , f 2 , y 2 .
P.C.: I'd say that the airplane and the simulator would probably rate about the same, and from the static conditions at this time over the top and around Mach 5. 2, 2, 2 would be about right. I had the impression that if I had upset the airplane as much as I upset the simulator, the airplane would have flown a little bit better because things wouldn't have reacted quite as quickly. This kind of led me to believe that both Cnb and Clb may be a little less than what we got on the simulator. The simulator has got a little higher frequency. It's kind of hard to say the airplane handles better and still say at the same time, that you think it handles better because Cnb and Clb are less, but it just seems to be that way. You don't get as rapid a motion out of it, so you don't have to work quite as hard. The simulator compares more favorably when you had these lower values of Cnb and Clb. I think if you reduced it to about 50%, that's what you'd see in the airplane.
H. Were any differences noted when da pulses were performed with the speed brakes extended?
P.C.: I didn't get that one.
Question: Was the reason you knocked it off here because you were too close in?
P.C.: I could have gotten something with the speed brakes open, but I think things would have changed so fast you wouldn't have been able to use it, plus I had elected to go with the dampers.
I. Rate the da pulses with the S.B. open;
J. Rate and discuss dv pulses at a » 10°, V » 4,000 fps.
I. Rate and discuss dv pulse at a » 5°, V » 3,000 fps. q 1.5 , f 3 , y 3 .
P.C.: I did get a yaw pulse on adaptive, zero, zero at about M =1.3 or 1.4 or 1,300 ft/sec or something like that, and the frequency seemed to be a little bit slower. Then I did one subsonic yaw pulse, and it seemed to be a little bit faster. In both cases it seemed to be a little bit better than the simulator. The one subsonic kind of confused me a little but because the first cycle rolled left and the second cycle came back and started off to the right.
Question: Is this around 5° or what would you guess?
P.C.: I seem to recall it was around 6°.
P.C.: I didn't use CSS.
B. Was glide to high key normal? Discuss the energy management situation.
P.C.: I just sat there and played with it for as long as I could. In fact, I forgot where the field was. I had to make a roll to find out where the runway was and realized that I had gotten home pretty high. I had to use a lot of speed brake coming down.
C. Was ground control required to locate the base?
P.C.: No. Ground control wasn't required.
D. Was a normal approach pattern used?
P.C.: Normal approach was used.
E.. Did you notice any buffet or unusual vibration during approach?
P.C.: No unusual vibrations or buffet.
F. Was a spot landing attempted?
P.C.: A spot landing was attempted. I think I overshot by 500 ft. and touchdown was a little bit fast.
G. Describe the airplane behavior after touchdown, (i.e., during roll-out).
P.C.: After touchdown, I'm almost sure the airplane was going to the left, and I used full right rudder and full right aileron just holding it and as it got down to about 100 knots, it started to respond a little bit, then it gave up.
H. Rate pilot task during approach to landing;
P.C.: I didn't feel any limit cycle at all.
B. At what point in the flight was ground control most helpful?
P.C.: Ground control was real helpful early in the profile to give me an indication of whether I was going high or not, then about midway through the profile as I started back down, he just kept reminding me. I think if he hadn't been saying anything, I'd gone by the base at Mach 3 at 60,000 ft., and had enough to turn around again. I would have continued on doing some task rather than get it slowed down.
C. Please summarize briefly your impressions of the stability levels, and controllability, for the ventral-off configuration with roll and yaw dampers off.
P.C.: The stability levels are low, but I don't think they would be extremely difficult to control. I think they could be controlled by the pilot without any problem, unless maybe the excursions get quite large. I can't see any reason why the excursions would get very large. There shouldn't be anything to upset it so you should be able to keep pitch, I'm guessing within ±5° at the worst condition, even if you did upset it. I don't think bank angle would change 20° and I don't think you would see more than -±2 or 3° sideslip. You could keep it at least under that kind of control. It doesn't move very fast, and I think the pilot can get to it real quick. Probably the worst thing that the pilot could do, would be to put in an input and hold it too long, so you would then get the greater excursions. I don't think I used as much control on this flight as I did on the last flight. It didn't seem to require it.
Question: You always felt you were ahead of the airplane?
P.C.: Yes. In fact, I'm a little disappointed that I didn't get more maneuvering out of the airplane for what flying I did get.
D. Discuss the adaptive flight control system.
P.C.: Apparently, the adaptive system in yaw is much better than the SAS system, because I recall having a steady-state oscillation on pushover with SAS, but I haven't seen it on either flight doing exactly the same thing. I would say roll is probably that much more effective too, although I don't recall how much rolling I did on that first flight with the SAS. I do recall that there was some, and I didn't see any problem with the adaptive today or the last flight.
In pitch, I think
it's just because it's different. And you get pitch rate rather than the
pitch attitude. My only complaint is that I don't really think I'm quite
used to it yet. I was more used to it this time than the last time, and
I think I did a better job it pitch. In fact, now I think it's easier to
fly than the simulator because it doesn't respond as quickly as the simulator
does. I don't know why I didn't get this limit cycle, unless there was
an awful lot of it coming from the lower ventral. I don't know why that
would be, but I don't feel any limit cycle. The wings aren't moving at
all. As far as seeing that center stick, it's not even there.