Jammed yoke
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Jammed yoke
Hi everyone!
I have a question: let's say you are flying a small GA plane, for example, a Cessna 172, you make a left turn and when you reach the bank angle you realize you can't get the stick back to neutral, the stick is jammed there and the aircraft keeps rolling. Is there anything to do in this situation? Can you overcome the roll with full opposite rudder? Is there any way to release the stick, if you apply as much force as you can?
I know that jet airliners and even turboprops are designed to overcome this emergency by separating the control columns applying high force on them or using handles in the cockpit to disconnect the roll, but what about small planes?
Also, the same problem in pitch, can you overcome it with trim and power? Does trim have any effect using it the opposite way acting as a mini elevator if the yoke is jammed? Or if the elevator itself is jammed?
Thank you very much!
I have a question: let's say you are flying a small GA plane, for example, a Cessna 172, you make a left turn and when you reach the bank angle you realize you can't get the stick back to neutral, the stick is jammed there and the aircraft keeps rolling. Is there anything to do in this situation? Can you overcome the roll with full opposite rudder? Is there any way to release the stick, if you apply as much force as you can?
I know that jet airliners and even turboprops are designed to overcome this emergency by separating the control columns applying high force on them or using handles in the cockpit to disconnect the roll, but what about small planes?
Also, the same problem in pitch, can you overcome it with trim and power? Does trim have any effect using it the opposite way acting as a mini elevator if the yoke is jammed? Or if the elevator itself is jammed?
Thank you very much!
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? Can you overcome the roll with full opposite rudder? Is there any way to release the stick, if you apply as much force as you can?
For elevator, yes, you can use trin and power. Both are worth having a practice, as is jammed throttle.
Last edited by foxmoth; 14th Jun 2012 at 12:29.
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Good question Andrew. No, light aircraft certification standards do not require the redundancy or separation of primary flight controls as is required for airliners. Though rare in the extreme, a jammed hardover control in a light aircraft is probably unrecoverable. An example of the concern of this is the limitation placed on the operation of some Piper twins, where asymmetric flaps are a concern, and in the extreme not recoverable.
Some certification basis of light aircraft require a demonstration that the aircraft can be landed with a specified control disconnected, but not jammed in any given position. I have landed my C 150 without using the pitch control at all, using the technique specified in the flight manual, but it is not easy, and should be done with a safety pilot.
That said, if you have confirmed the proper operation of the flight controls prior to takeoff, and you're not doing negative G maneuvers, you're probably very safe from a jam. I have had wires behind the panel come loose, and snag controls, but yes, you can overpower those.
On the theme of control problems in flight, my worst was as follows. I have posted it here before, but I think it is worthy of consideration in this context:
So you’re going to do a maintenance test flight….
Part One - Which way is up?
A maintenance test flight was required, prior to the Transport Canada approved test flight for the evaluation of an external installation to the aircraft. I had flown this aircraft months earlier, for a very similar mod evaluation purpose, including spins and dives to 1.1 of Vne. Those flights were fine. It had not flown since, while it underwent inspection for a commercial C of A. This was the maintenance test flight following that inspection.
The aircraft is a Cessna U206F, with a Robertson STOL kit, and additional external equipment mounted. Following a review of the documents for the maintenance, a thorough preflight inspection, and normal start, I taxied out. Just before taking off, a final check of control freedom and direction, including the elevator trim tab – I have just read too many stories about flight control problems on test flights… Everything looked as it should from the pilot’s seat.
The aircraft was light weight at takeoff, and promptly leapt off the runway… Then immediately leapt more. A swift and large nose down control input seemed to help, but still it was heading for space! I confirmed that the pitch trim was set for takeoff (and it had been) then I rolled it all the way nose down. That helped a bit, but not really much.
By this point, landing back on the remaining runway was no longer an option. A circuit now lay ahead of me, which was going to be a muscle builder! I could lie on my back and hold my 30 pound daughter at arms length over me for a few minutes at a time. This flying was a lot more demanding than that! Flying with one hand so as retract flaps (very carefully) and adjust power, was manageable for only a few moments at a time. In downwind, I found that full flaps created the least uncomfortable configuration, probably simply because slower speed, less control force. I did not dare fly too slowly, being quite uncertain about how the aircraft would handle if stalled this way. During downwind, I was thinking about how I might jam my knee into the control wheel so as to relieve my tired arms – there really was no practical way..
Flaring for landing was an exercise in how to appropriately reduce the massive downforce I was applying to the controls. It worked. I taxied in, alternating thoughts of shock, and the old joke: I just flew in from – here! – and are my arms tired!” I also reminded myself how lucky I was there were no seats, occupants, or flight test ballast in the back for this first flight….
Knowing that I had had a serious pitch control problem, I asked for a check of the elevator and trim tab travels. The elevator was as it should be. The trim tab offered 3 degrees, where I would have expected to find five degrees according to the type certificate data sheet. I asked that the maximum travel in this direction be provided. I got 7 degrees. There was still a lack of certainty as to what the problem was, because I could not see how such a small travel limit error could produce such a dramatic effect. I invited the mechanic to join me in my next test flight. He reluctantly agreed, knowing that if he would not ride in it, why would I fly it. This time I was well prepared to abandon the takeoff, if things were not right. The takeoff was better, but the pitch control problem was still there. what had been a 40-50 pound push, was now 15-20. The mechanic now had no doubt that something had been very wrong on the first flight, as was still wrong now. I landed back.
After a rather puzzling review of the maintenance accomplished since my flight a few months earlier , the answer was found. The maintenance personnel had put a little too much thought into what they were doing…. The required maintenance had included the required overhaul of the trim actuator, thus it, and all the chain and cable, had been removed, and reinstalled. During the re-rigging, the technician had read the travel requirements for the tab in the maintenance manual. Instead of setting the tab for an up travel limit of 25 degrees, he set the travel to a “nose up” (tab down) limit of 25 degrees. This left the travel limit in the other direction of only 5 degrees, which I hereby attest is not anywhere close to the requirement!
By trying to “figure out” what the system required, the actual instruction was not followed as written. An unsafe condition was the result. The safety system further broke down, when the second signatory for the work accomplished did not detect the error. This was also a maintenance failing designed in by Cessna, as it was possible to mis-rig the system in the first place, and the manual did not give any warning to check for the mis-rigging.
Part Two – Is there enough?
With the trim error corrected, and many sets of eyes and minds making sure everything was just as it should be, I had the aircraft loaded so as to be at maximum gross weight, at the aft C of G limit. Off I went again. The elevator trim worked, well, though I was not completely sure of the indicator position. I was, though, satisfied that the aircraft was now conforming to its design.
I climbed the aircraft very high as I had done before, to do stalls and spins as required by the design approval test flight plan. The power off stall was very normal. While setting up for the maximum continuous power, full flap stall, things started to go wrong again…
With the power set, and the flaps selected to full, and passing 20 degrees deflection, I reached the forward control wheel travel stop. The nose was rising quite quickly now, with no ability to stop it, as the flaps continued to extend. The trim was set to full nose down, but that was really not a factor anymore. I had no more control! The only resolution I could think of was to retract the flaps as quickly as possible. Reducing power did not seem a good idea at such a nose high attitude. The stall warning was now screaming, and who knows what kind of stall recovery I would have if I could not lower the nose!
The flaps retracted back through 10 degrees just as the plane began to mush rather badly, settling downward quite nose high. I got it all sorted out, and resumed normal flight. Being up high, I decided to explore this situation, to try to fully understand it. Obviously another discussion with the maintenance crew would be in order, I’d better have something to tell them which was helpful…
I set up again for the power on stall, this time feeding in flap a little at a time. Sure enough, at 20 degrees flap the control wheel was at the forward stop again. I found that with lots of muscle, and the elevator trim set at full nose up (which caused a little more effectiveness of the elevator, because of the downward tab), I could get 30 degrees of flap down, and control aircraft pitch with slight flap setting changes. The strength required to fly this way prevented doing it for very long.
So I took the plane back to the mechanics, and reported that it still did not fly right. After a review of the loading for the flight, an error was found in the basic weight and balance. I had been 150 pounds too light! And 1 inch aft of the aft limit. Could this combination result in these poor flying characteristics? I thought not, but we reloaded, and I went again. Nope, it flew the same way. Back I went.
After a complete re-inspection of control travels, and the system, it was found that a previously undetected broken bearing in the elevator bellcrank was affecting the elevator travel. The cable tension made this not immediately apparent during a walk around control check. I would have thought, that such a defect would have been found during the recently completed commercial annual inspection. Oops!
It was also found that the horizontal stabilizer (which is not adjustable relative to the airframe) was more than one degree beyond its specified angle of incidence – but in the direction which would improve pushover control! There is no adjustment for the H stab on the tailboom. The bellcrank was removed, and the bearing replaced, with the expectation that the elevator travel would now be correct. It is noteworthy that this model year of the C206 specified a bushing, not a bearing, so it had been changed at some previous time, but no technical record entry could be found to describe this work.
I test flew again…
Part Three – Please sir, may I have more?
With the bellcrank reinstalled, and the elevator re-rigged, the problem was now worse! The elevator deflection with the maximum possible travel, and farthest stop setting, was even less than it had previously been. The broken bearing had been improving the elevator’s range of travel! I landed back.
All of the other elevator control system parts were checked and found to be correct applicability, and in good condition. There is no Cessna design provision to adjust out this problem. The only remaining possibility was a modification to the elevator control stops. It was possible to completely remove the Cessna installed elevator control stop block, leaving only the bolt as the stop. This did allow just enough elevator travel that the aircraft could be safely flown through all of the phases of flight. I tested very thoroughly, and found the aircraft to be acceptable.
It is sobering to realize that this aircraft had flown for years following the repair that had the horizontal stabilizer incorrectly installed, and the wrong parts put into the elevator system. In this configuration, had a pilot used full flap and high power at the same time, with an aft C of G, they would have run out of elevator effectivness instantly. Close to the ground, at could have been fatal. It is total luck that this never happened. In such a case, it is unlikely that the accident investigators could ever have determined that a bent airframe had not been correctly repaired years earlier. The cause might have been reported as “pilot failed to maintain control”, rather than the very different “pilot could not maintain control, due to airframe defect”. I also reminded myself that my month’s earlier test flight, which should have caught this defect, did not. I have to be more thorough, even though what I might find is not what I was up looking for.
I contacted a Transportation Safety Board friend of mine, to informally report that this had happened to me. After explaining the whole thing, he said “that happened to you too?”. Apparently this trim misrigging had also happed to Transport Canada’s own C 206, with the same scary, muscle building, yet accident free outcome.
It the subsequent times, I told everyone I met, who were associated with C 206’s about this, just as a word to the wise. Some time later, a fellow called me, and asked if I would come and fly his 206, it was doing the same thing ( though with less force), which he had remembered my describing. I went to the airport, and asked that the control and trim travel limits be measured in my presence. It was measured, and the trim was wrong (though not backward). I had the mechanics put it right, flew the plane, and all was fine!
Some certification basis of light aircraft require a demonstration that the aircraft can be landed with a specified control disconnected, but not jammed in any given position. I have landed my C 150 without using the pitch control at all, using the technique specified in the flight manual, but it is not easy, and should be done with a safety pilot.
That said, if you have confirmed the proper operation of the flight controls prior to takeoff, and you're not doing negative G maneuvers, you're probably very safe from a jam. I have had wires behind the panel come loose, and snag controls, but yes, you can overpower those.
On the theme of control problems in flight, my worst was as follows. I have posted it here before, but I think it is worthy of consideration in this context:
So you’re going to do a maintenance test flight….
Part One - Which way is up?
A maintenance test flight was required, prior to the Transport Canada approved test flight for the evaluation of an external installation to the aircraft. I had flown this aircraft months earlier, for a very similar mod evaluation purpose, including spins and dives to 1.1 of Vne. Those flights were fine. It had not flown since, while it underwent inspection for a commercial C of A. This was the maintenance test flight following that inspection.
The aircraft is a Cessna U206F, with a Robertson STOL kit, and additional external equipment mounted. Following a review of the documents for the maintenance, a thorough preflight inspection, and normal start, I taxied out. Just before taking off, a final check of control freedom and direction, including the elevator trim tab – I have just read too many stories about flight control problems on test flights… Everything looked as it should from the pilot’s seat.
The aircraft was light weight at takeoff, and promptly leapt off the runway… Then immediately leapt more. A swift and large nose down control input seemed to help, but still it was heading for space! I confirmed that the pitch trim was set for takeoff (and it had been) then I rolled it all the way nose down. That helped a bit, but not really much.
By this point, landing back on the remaining runway was no longer an option. A circuit now lay ahead of me, which was going to be a muscle builder! I could lie on my back and hold my 30 pound daughter at arms length over me for a few minutes at a time. This flying was a lot more demanding than that! Flying with one hand so as retract flaps (very carefully) and adjust power, was manageable for only a few moments at a time. In downwind, I found that full flaps created the least uncomfortable configuration, probably simply because slower speed, less control force. I did not dare fly too slowly, being quite uncertain about how the aircraft would handle if stalled this way. During downwind, I was thinking about how I might jam my knee into the control wheel so as to relieve my tired arms – there really was no practical way..
Flaring for landing was an exercise in how to appropriately reduce the massive downforce I was applying to the controls. It worked. I taxied in, alternating thoughts of shock, and the old joke: I just flew in from – here! – and are my arms tired!” I also reminded myself how lucky I was there were no seats, occupants, or flight test ballast in the back for this first flight….
Knowing that I had had a serious pitch control problem, I asked for a check of the elevator and trim tab travels. The elevator was as it should be. The trim tab offered 3 degrees, where I would have expected to find five degrees according to the type certificate data sheet. I asked that the maximum travel in this direction be provided. I got 7 degrees. There was still a lack of certainty as to what the problem was, because I could not see how such a small travel limit error could produce such a dramatic effect. I invited the mechanic to join me in my next test flight. He reluctantly agreed, knowing that if he would not ride in it, why would I fly it. This time I was well prepared to abandon the takeoff, if things were not right. The takeoff was better, but the pitch control problem was still there. what had been a 40-50 pound push, was now 15-20. The mechanic now had no doubt that something had been very wrong on the first flight, as was still wrong now. I landed back.
After a rather puzzling review of the maintenance accomplished since my flight a few months earlier , the answer was found. The maintenance personnel had put a little too much thought into what they were doing…. The required maintenance had included the required overhaul of the trim actuator, thus it, and all the chain and cable, had been removed, and reinstalled. During the re-rigging, the technician had read the travel requirements for the tab in the maintenance manual. Instead of setting the tab for an up travel limit of 25 degrees, he set the travel to a “nose up” (tab down) limit of 25 degrees. This left the travel limit in the other direction of only 5 degrees, which I hereby attest is not anywhere close to the requirement!
By trying to “figure out” what the system required, the actual instruction was not followed as written. An unsafe condition was the result. The safety system further broke down, when the second signatory for the work accomplished did not detect the error. This was also a maintenance failing designed in by Cessna, as it was possible to mis-rig the system in the first place, and the manual did not give any warning to check for the mis-rigging.
Part Two – Is there enough?
With the trim error corrected, and many sets of eyes and minds making sure everything was just as it should be, I had the aircraft loaded so as to be at maximum gross weight, at the aft C of G limit. Off I went again. The elevator trim worked, well, though I was not completely sure of the indicator position. I was, though, satisfied that the aircraft was now conforming to its design.
I climbed the aircraft very high as I had done before, to do stalls and spins as required by the design approval test flight plan. The power off stall was very normal. While setting up for the maximum continuous power, full flap stall, things started to go wrong again…
With the power set, and the flaps selected to full, and passing 20 degrees deflection, I reached the forward control wheel travel stop. The nose was rising quite quickly now, with no ability to stop it, as the flaps continued to extend. The trim was set to full nose down, but that was really not a factor anymore. I had no more control! The only resolution I could think of was to retract the flaps as quickly as possible. Reducing power did not seem a good idea at such a nose high attitude. The stall warning was now screaming, and who knows what kind of stall recovery I would have if I could not lower the nose!
The flaps retracted back through 10 degrees just as the plane began to mush rather badly, settling downward quite nose high. I got it all sorted out, and resumed normal flight. Being up high, I decided to explore this situation, to try to fully understand it. Obviously another discussion with the maintenance crew would be in order, I’d better have something to tell them which was helpful…
I set up again for the power on stall, this time feeding in flap a little at a time. Sure enough, at 20 degrees flap the control wheel was at the forward stop again. I found that with lots of muscle, and the elevator trim set at full nose up (which caused a little more effectiveness of the elevator, because of the downward tab), I could get 30 degrees of flap down, and control aircraft pitch with slight flap setting changes. The strength required to fly this way prevented doing it for very long.
So I took the plane back to the mechanics, and reported that it still did not fly right. After a review of the loading for the flight, an error was found in the basic weight and balance. I had been 150 pounds too light! And 1 inch aft of the aft limit. Could this combination result in these poor flying characteristics? I thought not, but we reloaded, and I went again. Nope, it flew the same way. Back I went.
After a complete re-inspection of control travels, and the system, it was found that a previously undetected broken bearing in the elevator bellcrank was affecting the elevator travel. The cable tension made this not immediately apparent during a walk around control check. I would have thought, that such a defect would have been found during the recently completed commercial annual inspection. Oops!
It was also found that the horizontal stabilizer (which is not adjustable relative to the airframe) was more than one degree beyond its specified angle of incidence – but in the direction which would improve pushover control! There is no adjustment for the H stab on the tailboom. The bellcrank was removed, and the bearing replaced, with the expectation that the elevator travel would now be correct. It is noteworthy that this model year of the C206 specified a bushing, not a bearing, so it had been changed at some previous time, but no technical record entry could be found to describe this work.
I test flew again…
Part Three – Please sir, may I have more?
With the bellcrank reinstalled, and the elevator re-rigged, the problem was now worse! The elevator deflection with the maximum possible travel, and farthest stop setting, was even less than it had previously been. The broken bearing had been improving the elevator’s range of travel! I landed back.
All of the other elevator control system parts were checked and found to be correct applicability, and in good condition. There is no Cessna design provision to adjust out this problem. The only remaining possibility was a modification to the elevator control stops. It was possible to completely remove the Cessna installed elevator control stop block, leaving only the bolt as the stop. This did allow just enough elevator travel that the aircraft could be safely flown through all of the phases of flight. I tested very thoroughly, and found the aircraft to be acceptable.
It is sobering to realize that this aircraft had flown for years following the repair that had the horizontal stabilizer incorrectly installed, and the wrong parts put into the elevator system. In this configuration, had a pilot used full flap and high power at the same time, with an aft C of G, they would have run out of elevator effectivness instantly. Close to the ground, at could have been fatal. It is total luck that this never happened. In such a case, it is unlikely that the accident investigators could ever have determined that a bent airframe had not been correctly repaired years earlier. The cause might have been reported as “pilot failed to maintain control”, rather than the very different “pilot could not maintain control, due to airframe defect”. I also reminded myself that my month’s earlier test flight, which should have caught this defect, did not. I have to be more thorough, even though what I might find is not what I was up looking for.
I contacted a Transportation Safety Board friend of mine, to informally report that this had happened to me. After explaining the whole thing, he said “that happened to you too?”. Apparently this trim misrigging had also happed to Transport Canada’s own C 206, with the same scary, muscle building, yet accident free outcome.
It the subsequent times, I told everyone I met, who were associated with C 206’s about this, just as a word to the wise. Some time later, a fellow called me, and asked if I would come and fly his 206, it was doing the same thing ( though with less force), which he had remembered my describing. I went to the airport, and asked that the control and trim travel limits be measured in my presence. It was measured, and the trim was wrong (though not backward). I had the mechanics put it right, flew the plane, and all was fine!
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Jammed controls have been the root cause of many accidents involving GA planes and gliders. If you're lucky and the control is either jammed in (roughly) the neutral position or you can overpower what is causing the jamming rather quickly than you can either use the remaining controls (+power) to substitute for the jammed control (in the former case) or turn it into a non event that you walk away from although with a good scare (in the latter).
Any control that is permanently jammed with a significant deflection will get the plane in an unrecoverable attitude pretty quickly and then there won't be much that you can do if you don't have a parachute (either ballistic or personal).
Ciao,
Dg800
Edit to add: I'm of course referring to the primary controls only, as by the thread title I assume that is what you are referring to. Stuck flaps (in any position) or even a stuck throttle will lead to an emergency but usually not an unrecoverable one, i.e. you can manage to get the plane on the ground in one piece.
Any control that is permanently jammed with a significant deflection will get the plane in an unrecoverable attitude pretty quickly and then there won't be much that you can do if you don't have a parachute (either ballistic or personal).
Ciao,
Dg800
Edit to add: I'm of course referring to the primary controls only, as by the thread title I assume that is what you are referring to. Stuck flaps (in any position) or even a stuck throttle will lead to an emergency but usually not an unrecoverable one, i.e. you can manage to get the plane on the ground in one piece.
Last edited by Dg800; 14th Jun 2012 at 13:01.
Positive control checks on powered aircraft?
On gliders, a part of the daily inspection is positive control checks in which all the flying surfaces and airbrakes are operated from the cockpit with someone holding the control surface to reist the movement. The regular assembly/disassembly of gliders that live in trailers must be part of the reason for this, but I wonder how common it is in power flying?
Having flown an R/C model on which I had disconnected the elevator clevis to make an adjustment; then having been distracted, flew the model with the clevis disconnected but pushing on the control horn, I know how easy it is for a visual-only control check to lead one to believe all is ok. Fortunately in the case of the model, pushing on the control horn gave up elevator and it stayed in alignment for the whole flight, so I was able to complete the undulating circuit and land without damage.
There are at least two cases in which pilots have parachuted from their gliders at the top of the winch lauch having discovered their elevators were not properly connected. One glider had had its daily inspection, then had its tailplane removed and refitted by a third party without a note in the logbook or mention to the pilot who was going to fly it.
Having flown an R/C model on which I had disconnected the elevator clevis to make an adjustment; then having been distracted, flew the model with the clevis disconnected but pushing on the control horn, I know how easy it is for a visual-only control check to lead one to believe all is ok. Fortunately in the case of the model, pushing on the control horn gave up elevator and it stayed in alignment for the whole flight, so I was able to complete the undulating circuit and land without damage.
There are at least two cases in which pilots have parachuted from their gliders at the top of the winch lauch having discovered their elevators were not properly connected. One glider had had its daily inspection, then had its tailplane removed and refitted by a third party without a note in the logbook or mention to the pilot who was going to fly it.
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I had an alarming insight into how the Piper Autocontrol III autopilot works on a recent flight converting over to an Arrow. While approaching base I needed to make a slight descending right turn to point in the right direction for down wind, forgetting the autopilot was engaged - I instantly thought the yoke was jammed!
Asking my instructor if it was normal for the controls to feel so heavy, he simply replied "yes, when the autopilot is turned on". The manual says it can be over powered if needed but I'm slightly skeptical over that one!
Asking my instructor if it was normal for the controls to feel so heavy, he simply replied "yes, when the autopilot is turned on". The manual says it can be over powered if needed but I'm slightly skeptical over that one!
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My concern is for normal roll rate, as we do in pattern turns for example. It's really scary to know that even for normal turns, for which the usual entry is using small ailerons deflection, you can do nothing with the opposite rudder if the yoke jams, but I hope that as you said here, in situation like that you can keep it fairly controllable. It's pretty clear that at full deflection or I guess even at half it's unrecoverable but that's for aerobatics, isn't it? And what about a personal parachute? It would be possible to escape from the aircraft if it's flying an uncontrollable roll?
I read somewhere that with a jammed yoke or elevator it is impossible to fly with the trim wheel because it has no effect being too small to act as an elevator. Can it be possible?
Sorry for being pushing, I don't want to be exaggerated, I'm a PPL student and I just want to be prepared for the unexpected.. In my opinion, it's ok thinking about all kind of possible failures while on ground and be ready to face them in the air, and doing that, I realised that this 2 problems regarding ailerons jammed deflected or elevator jammed seem to be unrecoverable in some circumstances, that's why I'm asking about them. I didn't find others come that close to a certain out of control situation, maybe you know more dark scenarios
Thank you!
I read somewhere that with a jammed yoke or elevator it is impossible to fly with the trim wheel because it has no effect being too small to act as an elevator. Can it be possible?
Sorry for being pushing, I don't want to be exaggerated, I'm a PPL student and I just want to be prepared for the unexpected.. In my opinion, it's ok thinking about all kind of possible failures while on ground and be ready to face them in the air, and doing that, I realised that this 2 problems regarding ailerons jammed deflected or elevator jammed seem to be unrecoverable in some circumstances, that's why I'm asking about them. I didn't find others come that close to a certain out of control situation, maybe you know more dark scenarios
Thank you!
Last edited by andrew172; 14th Jun 2012 at 17:24.
andrew 172:
"I know that jet airliners and even turboprops are designed to overcome this emergency by separating the control columns....."
Not true! The DC-10 had no such facility for all controls were hydraulic. The Bae 146 had a disconnect handle for the elevators and the ailerons (the rudder was hydraulic) but that was only because BAe designed those controls to be operated by old-fashioned bowden cables running to servo tabs.
Which other jet airliners do you know of that have this facility?
"I know that jet airliners and even turboprops are designed to overcome this emergency by separating the control columns....."
Not true! The DC-10 had no such facility for all controls were hydraulic. The Bae 146 had a disconnect handle for the elevators and the ailerons (the rudder was hydraulic) but that was only because BAe designed those controls to be operated by old-fashioned bowden cables running to servo tabs.
Which other jet airliners do you know of that have this facility?
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I read it from the 737 manual and it states that in case of control jamming you can separate the yokes by applying some force. Also, I heard that 767 (and the 777, I guess) has a split elevator system which in case of emergency can be used as a half from a yoke or the other. I didn't read a lot of details about these features because it was enough to know they are present to help the pilot in an emergency. My concern was for small single engine aircraft where you don't have that redundancy and you actually can't really deal with the problem.
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I read somewhere that with a jammed yoke or elevator it is impossible to fly with the trim wheel because it has no effect being too small to act as an elevator. Can it be possible?
Chute is the best option if you have one and is recommended for aeros.
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You can definitely control pitch pretty well by using the trim wheel, with a solidly jammed elevator, but the trim wheel then works in the opposite direction to normal.
I've tested it - it works on the TB20.
I've tested it - it works on the TB20.
Last edited by peterh337; 14th Jun 2012 at 18:47.
Surely that wouldn't work if the elevator was jammed up or down much? I would think it would only work if the elevator was jammed almost neutral.
(I've flown a Jode DR1050l on rudder-elevator trim-throttle, with the stick free.)
(I've flown a Jode DR1050l on rudder-elevator trim-throttle, with the stick free.)
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first off there seems to be some confusion about airliners and controls...I've flown the BAE146, B737, and the DC9 (the best of the lot).
all have some sort of break away on the control yokes or similiar device...that is if ONE part of the control yoke system doesn't function, you move the OTHER yoke hard enough and a clutch between the two yokes disengages and allows one yoke to move...but it only moves a portion of the flight controls...and whether or not they are hydraulically powered doesn't matter at this point in the control system.
having said that:
I flew a piper arrow some 30 years ago and the bicycle chain/sprocket system of aileron/yoke etc came loose..the actual chain jumped the sprocket ( I did find this out after landing).
so I made a long straight in to an airport NOT surounded by thousands of houses, using rudder and we made it.
the way to find out is go up, put the plane into a normal bank...don't move the yoke and press the rudder pedal...of course if you are too slow you might end up on your back in a spin or something, so don't get too slow...use plenty of altitude...I demonstrated stuff like this with my students...indeed I made them learn how to slop through a turn with wings level, just with rudder or in the case of a twin, with assymetric thrust.
maybe you hven't had good instruction so far...find a really old time instructor or designated examiner and get a lesson from him
chances are you don't ram the controls over hard to enter a normal turn, and the idea of all flyings is...if you do something and it don't feel right...stop it! get back to a normal situation.
and yes, if a plane is right out of MX...don't trust anything!!!!!!
----
ANDREW, your questions should be addressed by your instructor and if not by him, certainly the chief instructor ofyour school. I will relate this to you...during th early days of flying a CAA inspector (forerunner of the USA FAA) took off in a plane in which the ailerons had been hooked up backwards...he landed using just the rudder for roll/yaw...at that time it was required that the rudder be able to over come the aileron for just such an eventuality...
of course in the 737 there was a rudder hardover that could not be overcome by the crew causing a crash...additional training and procedure helped us overcome this problem.
so:
always check the flight controls prior to takeoff...and LOOK outside the plane and make sure they move in the correct way and return to neutral
rarely in any plane do you need full YOKE/CONTROL throw in normal flight...perhaps for crosswind landings is one possible exception, so you will probaably be able to handle the problems you describe
and if your instructor is very new, maybe he doe3sn't know the answers...find another instructor...and not one who just wants to take you up to scare you
you should not get scared into learning things.
all have some sort of break away on the control yokes or similiar device...that is if ONE part of the control yoke system doesn't function, you move the OTHER yoke hard enough and a clutch between the two yokes disengages and allows one yoke to move...but it only moves a portion of the flight controls...and whether or not they are hydraulically powered doesn't matter at this point in the control system.
having said that:
I flew a piper arrow some 30 years ago and the bicycle chain/sprocket system of aileron/yoke etc came loose..the actual chain jumped the sprocket ( I did find this out after landing).
so I made a long straight in to an airport NOT surounded by thousands of houses, using rudder and we made it.
the way to find out is go up, put the plane into a normal bank...don't move the yoke and press the rudder pedal...of course if you are too slow you might end up on your back in a spin or something, so don't get too slow...use plenty of altitude...I demonstrated stuff like this with my students...indeed I made them learn how to slop through a turn with wings level, just with rudder or in the case of a twin, with assymetric thrust.
maybe you hven't had good instruction so far...find a really old time instructor or designated examiner and get a lesson from him
chances are you don't ram the controls over hard to enter a normal turn, and the idea of all flyings is...if you do something and it don't feel right...stop it! get back to a normal situation.
and yes, if a plane is right out of MX...don't trust anything!!!!!!
----
ANDREW, your questions should be addressed by your instructor and if not by him, certainly the chief instructor ofyour school. I will relate this to you...during th early days of flying a CAA inspector (forerunner of the USA FAA) took off in a plane in which the ailerons had been hooked up backwards...he landed using just the rudder for roll/yaw...at that time it was required that the rudder be able to over come the aileron for just such an eventuality...
of course in the 737 there was a rudder hardover that could not be overcome by the crew causing a crash...additional training and procedure helped us overcome this problem.
so:
always check the flight controls prior to takeoff...and LOOK outside the plane and make sure they move in the correct way and return to neutral
rarely in any plane do you need full YOKE/CONTROL throw in normal flight...perhaps for crosswind landings is one possible exception, so you will probaably be able to handle the problems you describe
and if your instructor is very new, maybe he doe3sn't know the answers...find another instructor...and not one who just wants to take you up to scare you
you should not get scared into learning things.
Last edited by sevenstrokeroll; 14th Jun 2012 at 20:12.
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maybe you hven't had good instruction so far...find a really old time instructor or designated examiner and get a lesson from him
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foxmoth...if my student asked me an intelligent set of questions as andrew has, I would answer that set of questions at the earliest opportunity...if he has to worry about such things he will not get the full benefit of the basics.
ask the questions, get the answers
and I would certainly take the time to discuss what to do with control problems, throttle failure and the like PRIOR to first solo.
ask the questions, get the answers
and I would certainly take the time to discuss what to do with control problems, throttle failure and the like PRIOR to first solo.
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oh, by the way
if you have hydraulic operated controls, that DOES NOT MEAN you couldn't have YOKE malfunction and the cables, pulleys et all could still manipulate the hydraulic portion of the controls...and the instinctive yoke breakaway could hep you alot (instinctive means, in this cas3e...hey the yoke is jammed...I better put every ounce of force my arms can muster and BAM, ok my control yoke has unjammed and a PORTION of the flight controls can be controlled by me...and a safe landing just might be possible)
if you have hydraulic operated controls, that DOES NOT MEAN you couldn't have YOKE malfunction and the cables, pulleys et all could still manipulate the hydraulic portion of the controls...and the instinctive yoke breakaway could hep you alot (instinctive means, in this cas3e...hey the yoke is jammed...I better put every ounce of force my arms can muster and BAM, ok my control yoke has unjammed and a PORTION of the flight controls can be controlled by me...and a safe landing just might be possible)
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Surely that wouldn't work if the elevator was jammed up or down much? I would think it would only work if the elevator was jammed almost neutral.
I think the biggest danger is somebody leaving some object in the airframe, which jams the controls. This has happened; from vague memory a number of times. Control linkages coming off completely (without jamming the controls) are not uncommon too, but they should not cause a crash.
Concorde had an interesting system, whereby strain gauges were placed on the yoke(s) which drove a separate control system so that a totally (locally) jammed yoke would still work - again from vague memory.
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foxmoth...if my student asked me an intelligent set of questions as andrew has, I would answer that set of questions at the earliest opportunity...if he has to worry about such things he will not get the full benefit of the basics.
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foxmoth
when I was instructing some 30 years ago, I didn't have e mail...but I would certainly give my student my e mail address now and he could write me for an answer.
but back in prehistoric times, I would certainly have encouraged my students to TELEPHONE me with a question.
Now grant you, I would not give an hour lecture on the phone, but it would open the dialogue about such matters.
andrew, do you have your instructor's phone number?
andrew, how often do you take a lesson?
If you are learning to fly and flying less than one time a week, you might want to re evaluate your learning scheme.
when I was instructing some 30 years ago, I didn't have e mail...but I would certainly give my student my e mail address now and he could write me for an answer.
but back in prehistoric times, I would certainly have encouraged my students to TELEPHONE me with a question.
Now grant you, I would not give an hour lecture on the phone, but it would open the dialogue about such matters.
andrew, do you have your instructor's phone number?
andrew, how often do you take a lesson?
If you are learning to fly and flying less than one time a week, you might want to re evaluate your learning scheme.
Sorry for being pushing, I don't want to be exaggerated, I'm a PPL student and I just want to be prepared for the unexpected.. In my opinion, it's ok thinking about all kind of possible failures while on ground and be ready to face them in the air, and doing that, I realised that this 2 problems regarding ailerons jammed deflected or elevator jammed seem to be unrecoverable in some circumstances, that's why I'm asking about them. I didn't find others come that close to a certain out of control situation, maybe you know more dark scenarios
Thank you!
So for example getting too low and too slow on final approach will probably happen to you and the consequence of letting the aircraft stall and maybe spin will be very severe. Similarly not checking your fuel quantity before takeoff will, if done on a regular basis, lead to a high probability you will run out of gas which again obviously has going to be lead to a high level of severity in the outcome. So I will put a lot of emphasis on you managing your pitch attitude and power so that you fly a safe final approach profile and my preflight inspection training will emphasize the importance of checking the fuel. These actions are an example of you being trained to mitigate and manage dangers.
The hard part of risk management is how one deals with low probability but high consequence scenarios. A jammed control is a good example of one of those. It is a very low probability event especially for simple flying club powered aircraft (it is more of a concern for gliders however) and virtually all pilots will fly their whole career without ever having to deal with this emergency. There are many many emergencies which are much more likely for you to experience.
There are is a practical limit to how much you can specifically prepare for and the danger is to so worry about the extremely rare events you neglect to place a sufficient effort in learning to manage the more common emergencies.
However the chance of a jammed control is not zero and obviously it is a very serious emergency should it happen so If you were my student and asked this question here is what I would say.
A jammed control is an extremely rare occurrence and therefore it is important that before you worry about this kind of event you learn and understand how to deal with the much more common emergencies which I will be covering during the PPL course.
Your question is not a silly one however and we are already indirectly mitigating this risk in other ways.
The first is understanding what we are looking for in the preflight inspection so we are more likely to identify a problem which could lead to a control jam before we even takeoff. Remember last month when I pointed out the aircraft we were about to fly had just come out of a 100 hour inspection? You recall we spent extra time looking for tools left behind, loose carpet that could foul the controls, missing panels etc etc. This is an example of managing the increased risk that will inevitably exist when substantial work is done and heps mitigates not only the risk of jammed controls, but other things that could present an inflight problem
The second way we mitigate this risk is by having a complete understanding of the effects of the aircraft controls and so in the event of a jammed control we would use this knowledge to maximize the chance of retaining enough control to still fly the aircraft, so for instance, using roll yaw coupling to roll an aircraft with jammed ailerons. So while we are not going to specifically cover the jammed control scenario you will nevertheless have the kinds of skills which can be used to deal with this emergencies and other low probability events by the end of the PPL.
Oh and while we are talking emergencies tell me what you are going to do if we are cruising out to the practice area on our next flight and the engine suddenly starts to run rough........
Last edited by Big Pistons Forever; 15th Jun 2012 at 00:34.