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paradoxbox
9th Apr 2019, 22:40
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.

slacktide
12th Apr 2019, 22:09
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.

vilas
13th Apr 2019, 09:34
Don't do in an Airbus you may lose your vertical stabilizer.

Farmer106
13th Apr 2019, 16:31
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.

scifi
14th Apr 2019, 11:25
Quote.... 'you will descend'
That ain't necessarily so...
https://www.youtube.com/watch?v=4UZDaHdJBRs
.

Slatye
14th Apr 2019, 12:27
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.

gearlever
14th Apr 2019, 15:35
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?

Slatye
15th Apr 2019, 12:49
"with the elevator "


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

slacktide
15th Apr 2019, 21:54
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.

scifi
16th Apr 2019, 11:15
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..

hans brinker
3rd May 2019, 04:26
Yes, my apologies. Clearly wasn't thinking straight when I wrote that bit.

You were 90deg of from straight it would appear... :)

InSoMnIaC
3rd May 2019, 18:49
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.

gearlever
3rd May 2019, 20:07
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.

paradoxbox
5th May 2019, 17:54
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.
https://youtu.be/35Zy_rl8WuM?t=1615

Goldenrivett
5th May 2019, 19:18
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.

paradoxbox
5th May 2019, 19:45
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/questions/31440/does-slipping-in-turns-allow-higher-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.

A Squared
5th May 2019, 20:41
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.

vilas
7th May 2019, 17:02
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.

Check Airman
7th May 2019, 21:21
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.

gearlever
7th May 2019, 21:36
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....

KayPam
11th May 2019, 00:31
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.
Assuming that the trim and elevator controls are jammed, you would like to fly the aircraft in a bank and sideslip so that the rudder has pitch authority.
I'm also assuming that in this situation you would just point your aircraft to a runway and would like to know how to land with the least possible damage.

The problem is, the rudder will only increase fuselage lateral angle of attack (also known as sideslip). It will do nothing to the wings angle of attack (the more common one when looking at lift)
Fuselage lift will be a thing, if you're in a full deflection sideslip. However there is little chance you could do a flare by adding fuselage lift.
First of all, because adding fuselage lift means adding much drag, so speed loss and wing lift loss.
Second, most aircraft will have little bank (like 10° tops) even with full rudder deflection, so fuselage lift will be very limited : sin10° = 17%.
So you will get 17% of the lift effet but 100% of the drag effect.
It is not promising.

misd-agin
11th May 2019, 02:21
In general the rudder pedals are best left alone in all airliners. Except for engine out or crosswind landings or takeoffs.

Can you use them, with care, if you're in an extreme attitude? If that's the last option go ahead. But it's not the primary or first option to choose. How many of us will experience those attitudes in an airliner during our career? Almost none of us.

In the AA 587 A300 crash the rudder pedals were moved rapidly back and forth several times. Rudder movement by itself wasn't the problem. The rapid changing from one rudder input to the other increased the load. The tail failed above the design and certification limit after the 4th(?) rudder reversal.

From the NTSB -

"The Safety Board found that the first officer, who was the flying pilot, inappropriately manipulated the rudder back and forth several times after the airplane encountered the wake vortex of a preceding Boeing 747 for the second time. The aerodynamic loads placed on the vertical stabilizer due to the sideslip that resulted from the rudder movements were beyond the ultimate design strength of the vertical stabilizer. (Simply stated, sideslip is a measure of the "sideways" motion of the airplane through the air.)

The Board found that the composite material used in constructing the vertical stabilizer was not a factor in the accident because the tail failed well beyond its certificated and design limits."