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Question about crossing controls in your aircraft

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Question about crossing controls in your aircraft

Old 9th Apr 2019, 21:40
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Question about crossing controls in your aircraft

I'll try to keep this short and sweet, I'd appreciate short and sweet answers too, and any additional relevant information if you have it.
I would appreciate it a lot if you could include the type of aircraft you're talking about. Sim experiences also welcome.

I'd like to know if putting in full rudder and opposite aileron in your aircraft is enough to provide reasonable pitch control in the case that you've lost control of your elevator or trim.

Can the nose be kept above the horizon in this condition using the rudder? If so, is there enough aileron to prevent the nose from coming up too high without having to start banking in the opposite direction, or do you let up on the rudder? Any important speeds to know about to do this? How does having the boards full out on one wing affect the pitch and speed on your aircraft?

This is just a personal curiosity of mine.

Thanks.
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Old 12th Apr 2019, 21:09
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A full-pedal forward slip is an excellent way to quickly loose a lot of altitude without increasing airspeed. If you transition from trimmed level flight to a forward slip with constant power, you will descend, regardless of aircraft type.
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Old 13th Apr 2019, 08:34
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Don't do in an Airbus you may lose your vertical stabilizer.

Last edited by vilas; 13th Apr 2019 at 11:09.
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Old 13th Apr 2019, 15:31
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I dont't think anyone will have a valid answer to that. No one will try it in real live, and I am not shure the SIM will be very realistic.
For the Airbus, I would think you will be OK as long as you dont't use opposite rudder inputs. From right to left, and so on.
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Old 14th Apr 2019, 10:25
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Quote.... 'you will descend'
That ain't necessarily so...
.
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Old 14th Apr 2019, 11:27
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Originally Posted by scifi
Quote.... 'you will descend'
That ain't necessarily so...
Yes. If you've got a massive thrust-to-weight ratio then it's quite manageable. We used to do it with radio controlled planes all the time; most of the electric ones can easily fly with a 90 degree bank angle.

For "normal" aircraft, I suspect that you might be able to keep the nose above the horizon (as specified in the original question) with the elevator - but that's not going to translate into a climb. It'll be essentially a conventional stall, as the airflow over the lifting surface (side of the fuselage in this case) is insufficient to support the weight of the aircraft.
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Old 14th Apr 2019, 14:35
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Originally Posted by Slatye
Yes. If you've got a massive thrust-to-weight ratio then it's quite manageable. We used to do it with radio controlled planes all the time; most of the electric ones can easily fly with a 90 degree bank angle.

For "normal" aircraft, I suspect that you might be able to keep the nose above the horizon (as specified in the original question) with the elevator - but that's not going to translate into a climb. It'll be essentially a conventional stall, as the airflow over the lifting surface (side of the fuselage in this case) is insufficient to support the weight of the aircraft.
"with the elevator "


Rudder you mean, don't you?
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Old 15th Apr 2019, 11:49
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Originally Posted by gearlever
"with the elevator "


Rudder you mean, don't you?
Yes, my apologies. Clearly wasn't thinking straight when I wrote that bit.

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Old 15th Apr 2019, 20:54
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Originally Posted by scifi
Quote.... 'you will descend'
That ain't necessarily so...
https://www.youtube.com/watch?v=4UZDaHdJBRs
.
That aircraft did not simply transition from straight and level flight to a forward slip. It also added power and used the elevator to pitch up. Since question that was asked was whether a slip can be used to maintain positive pitch control in the event of elevator failure, the video is a non-sequitur. But it does have pretty balloons.
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Old 16th Apr 2019, 10:15
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Well, once you have rolled over 45 degrees, the elevator becomes the rudder and the rudder becomes the elevator. Most semi-aerobatic GA aircraft and gliders can achieve over 45 degrees of roll, and obviously the higher powered fully-aerobatic aircraft can achieve 90 degrees of roll. The closest I have ever got to 90 degrees was in a Salsbury T76M, at about 80 degrees, which looks Ok from a distance..
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Old 3rd May 2019, 03:26
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Originally Posted by Slatye
Yes, my apologies. Clearly wasn't thinking straight when I wrote that bit.
You were 90deg of from straight it would appear...
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Old 3rd May 2019, 17:49
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You’ll probably have more luck using the pitching moment of the engines to control pitch. The EAT (DHL express) A300 incident over baghdad comes to mind where after the loss of all flight controls, the crew managed to fly, carry out an approach, go around, reposition for another approach and land safely with only the use of thrust.
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Old 3rd May 2019, 19:07
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Originally Posted by InSoMnIaC
You’ll probably have more luck using the pitching moment of the engines to control pitch. The EAT (DHL express) A300 incident over baghdad comes to mind where after the loss of all flight controls, the crew managed to fly, carry out an approach, go around, reposition for another approach and land safely with only the use of thrust.
Yep, a masterpiece of CRM and pilot skills.
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Old 5th May 2019, 16:54
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This is what got me thinking about the issue. As someone mentioned earlier in the thread, many aerobatic aircraft have enough rudder authority to maintain altitude in (or near) a 90 degree bank. But it turns out that the MD-11 can also achieve, or nearly achieve this as well.
That's why I'm asking about particular aircraft types. The video talks about a different situation, I'm just speculating as to whether the rudder could be used like this in different scenarios.
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Old 5th May 2019, 18:18
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But it turns out that the MD-11 can also achieve, or nearly achieve this as well.
What makes you think that?

All the recovery actions involve co-ordinated use of rudder (never use opposite rudder. See time 20 mins into video.)
The use of bank is to help lower the nose in a nose high situation.
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Old 5th May 2019, 18:45
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He states it in the video.

I'm aware he's talking about coordinated rudder, that's why I mentioned in my post, I'm talking about different scenarios in which the rudder may be helpful. It's just a thought experiment.

(Edit: He states attitude, not altitude, my mistake.) But if the issue is that you can't get the nose up because of loss of pitch control, getting it up using the rudder before leveling the wings may be one way to stop altitude from creeping down, hence my original question. What I am envisioning is a shallow bank with the nose being kept very high with the rudder. In aerobatic aircraft there is a point where even if you are in a slip you will start gaining altitude like this with crossed controls. It sounds to me like the MD-11 may be capable of doing this, I'd like to know what else can do it.

There's an interesting glider discussion here:
https://aviation.stackexchange.com/q...er-climb-rates

Keeping in mind I'm specifically talking about trying to do this when you don't have control of elevator or trim and thus have few if any other options. I'm not brave enough to try this in anything other than aerobatic planes. I suppose it depends on how much power you've got available to keep the vertical speed pegged. If you can get the thrust pointed in the right direction it becomes a kind of poor man's thrust vectoring.

Here's an interesting article about a cowboy test flight done with no elevator or aileron, just trim.
http://www.barryschiff.com/sam_pp1.htm

Another technique mentioned in both the AA videos and around the internet was actually shifting the passengers in the cabin to get the CG in the right spot.

Just trying to see what options are out there for this nightmare scenario.

Last edited by paradoxbox; 5th May 2019 at 20:38.
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Old 5th May 2019, 19:41
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Originally Posted by vilas
Don't do in an Airbus you may lose your vertical stabilizer.
What caused the loss of AA587's vertical stabilizer was not a full scale rudder deflection, but an abrupt reversal of the rudder from near full scale one direction, changing rapidly to near full scale deflection the opposite direction. That is completely different scenario whcih imposes higher loads than a single full scale deflection, and is beyond the transport category certification standards. The vertical stabilizer in the A300, like all transport category aircraft, was designed to withstand the loads imposed by a *single* full scale rudder deflection, and there is no evidence whcih suggests that would have caused failure of the vertical stabilizer.

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Old 7th May 2019, 16:02
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Originally Posted by A Squared
What caused the loss of AA587's vertical stabilizer was not a full scale rudder deflection, but an abrupt reversal of the rudder from near full scale one direction, changing rapidly to near full scale deflection the opposite direction. That is completely different scenario whcih imposes higher loads than a single full scale deflection, and is beyond the transport category certification standards. The vertical stabilizer in the A300, like all transport category aircraft, was designed to withstand the loads imposed by a *single* full scale rudder deflection, and there is no evidence whcih suggests that would have caused failure of the vertical stabilizer.
Yes I have read the report. But you don't apply full rudder deflection in commercial jets. Especially Airbus it is recommended only to keep it straight during takeoff and landing or during engine failures. You don't do any fancy side slips.
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Old 7th May 2019, 20:21
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Originally Posted by vilas
Yes I have read the report. But you don't apply full rudder deflection in commercial jets. Especially Airbus it is recommended only to keep it straight during takeoff and landing or during engine failures. You don't do any fancy side slips.
Vilas is right (of course). I learned the hard way that the rudder pedals are best left alone in an Airbus. Thankfully, only my ego was bruised.

Repeated rudder reversals is a no-no anyway. That accident taught a lot of us a bit more about Va than we thought we knew.
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Old 7th May 2019, 20:36
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Originally Posted by Check Airman
Vilas is right (of course). I learned the hard way that the rudder pedals are best left alone in an Airbus. Thankfully, only my ego was bruised.

Repeated rudder reversals is a no-no anyway. That accident taught a lot of us a bit more about Va than we thought we knew.
Yeah, the outcome of AA587 was a real surprise for most A300 operators.
Well, not only A300 in the aftermath....
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