-1
$\begingroup$

What would a pilot do if none of the control surfaces are responding?

For example, a pilot flies a medium-sized plane and to make the situation a bit less hectic, they're the only one onboard. Then they make a subtle turn, but nothing moves. They try again, but the plane isn't turning. They then become quite worried and assess the situation, trying if any of the control surfaces are working. To a shocking realization, none of the control surfaces are responding. And luck isn't on their side: when the control surfaces stopped responding, the plane was at a slight descent of about 5 degrees. If they can't figure out what to do soon, they're going to collide with the ground. The pilot can't tell what is causing the problem but assumes that it is something wrong with the control surfaces themselves, not the control linkage between the control surfaces. The pilot can't tell if the control surfaces are frozen, stuck, or broken. And the final take is that the plane isn't going slow enough for the pilot to safely bail out of the plane. They guess that they have at most 8 minutes before they crash.

So what would the pilot do? And if it seems highly unlikely that such an event would ever happen under the given circumstances in the example provided, then imagine a significantly different scenario in which a pilot is in a P-51 Mustang and they've been shot all over (the plane, not the pilot) to the point where nothing is working, likely linkage failure or other damage. What would a Pilot do, especially if they're in a situation where bailing the plane just isn't an option?

$\endgroup$
8
  • 2
    $\begingroup$ Why are they descending? Is the engine out too? One engine or two? $\endgroup$
    – Ron Beyer
    May 25 '21 at 22:42
  • 2
    $\begingroup$ Even in a war, how could all surfaces fail at the same time? (This doesn't sound like airliner hydraulics or FBW with total electrical failure.) The pilot would surely notice the first one failing before the others failed. $\endgroup$ May 25 '21 at 23:02
  • 3
    $\begingroup$ United 232 springs to mind. But this feels like a very artificial, 'movie plot' scenario, and I'm not sure what sort of answer you expect. Are you asking what practical troubleshooting steps the pilot might take? $\endgroup$
    – Pondlife
    May 25 '21 at 23:22
  • 3
    $\begingroup$ Not that it changes anything, but I'd point out that 5° descent is not "slight": it's a lot. A "slight" descent, say 100-200 fpm, would be of the order 1:100, which is a fraction of a degree; perhaps just over a degree for a slower airplane. Landing (final approach) is conducted at about 3°. $\endgroup$
    – Zeus
    May 26 '21 at 2:20
  • 2
    $\begingroup$ The exact outcomes depend on too many factors for a meaningful answer, in my opinion. What exact systems have failed? How have they failed? What systems is the aircraft equipped with? This is like asking how you should deal with a broken steering wheel without specifying if you are in a golf cart, Formula 1 car or a Bagger 228. $\endgroup$
    – Sanchises
    May 26 '21 at 13:45
7
$\begingroup$

Hopefully while this is happening, the airplane is in trim and more or less wants to continue where it's headed.

Say the airplane was in trim at 150kt and you had power set for level flight at trim speed. If the trim system still works, you still have significant pitch control, because you can vary the speed that airplane wants to fly at and you have power that you can adjust to make it climb or descend. You also have flaps which change trim significantly and if there are people in the back, you can alter trim speed by getting them to move forward and aft. If the trim system doesn't work, all you have is flaps and C of G shifting if you can, and the effects of power changes to the extent they are there.

The big problem isn't pitch, it's roll control. If you're in a single engine plane and have no roll or yaw control, you are pretty much screwed. Once the airplane gets disturbed and starts to drift off into a spiral, you're done without some way to roll the wings level.

If you're in a twin, with engines on the wings, you might have a fighting chance because you can achieve some control over bank by using differential power to skid the plane, which makes it tend to bank toward the "slow" side, depending on how strong its roll-yaw couple is. Jets with swept wings achieve really high roll rates when skidding, so differential thrust can be used to control banked turns with reasonable precision, although the input/response loop is very slow and would require a lot of finesse to avoid getting into self-magnifying oscillations.

A straight wing twin with mild roll due to yaw would be pretty challenging and the change/result cycle would take forever. So hopefully the air is smooth while this is happening. If it's really bumpy, you're probably screwed.

So it that happened to me, and I was in a twin, I'd be experimenting with asymmetric power, trim, flaps etc., to see what I could do, and to the extent I was able to gain some control, I would spend as much time as I could practicing before I tried to descend. Then the main thing is to find a very large and long runway to land on, knowing the probable result is a hopefully survivable crash. If I auger straight into the ground, because all the slithering and sliding from power changes meant that I wasn't able to maintain control, well, at least I went down fighting.

$\endgroup$
3
  • 3
    $\begingroup$ Alternative roll control :) $\endgroup$
    – Sanchises
    May 26 '21 at 13:46
  • $\begingroup$ @Sanchises Exactly what I was thinking of. $\endgroup$ May 26 '21 at 19:51
  • $\begingroup$ I was thinking of that also and I'd probably try it myself out of desperation, but you'd have to be in something like a 172, and I don't think you'd have to body strength to shove and hold panels out sufficiently to get any control. I've you've ever tried to push a door on a 172 open while at any flying speed, it's pretty tough to get it out more than a few inches. $\endgroup$
    – John K
    May 26 '21 at 20:37
2
$\begingroup$

Most pilots would go through whatever procedures they could to free up the controls, including improvising or forcing things. After that the only thing left is to perhaps attempt some sort of spiritual reconciliation if they are moved to do so.

Pilots face death the same way other mortals do...

$\endgroup$
2
$\begingroup$

There have been cases like this. One of the most successful incidents occurred in Baghdad when DHL A300 was shot with a manpad.

Airbus has published a neat study of the case with analysis. Basically AC will enter a long, low frequency phugoid oscillating around trimmed speed. You forget the speed and fly the pitch with thrust.

https://www.smartcockpit.com/docs/Baghdad_A300_Incident.pdf

$\endgroup$
1
  • $\begingroup$ The OP mentioned engines out in the comments. $\endgroup$ May 27 '21 at 15:16

Not the answer you're looking for? Browse other questions tagged or ask your own question.