Tail Rotor Problems
Guest
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Shytorque: Yeah - agreed .......I misunderstood where you were coming from.
CONCUR: TR failure - forget throttle playing!
Nr variation with a CONTROL problem can make all the difference and is something to be practised and thought about. Again ONLY - with someone who knows how.
Thanks for the reply - I too saw the same video it is very scary stuff.
I assume you were on PUMA sim?
CONCUR: TR failure - forget throttle playing!
Nr variation with a CONTROL problem can make all the difference and is something to be practised and thought about. Again ONLY - with someone who knows how.
Thanks for the reply - I too saw the same video it is very scary stuff.
I assume you were on PUMA sim?
Guest
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Shytorque - good post.
To have access to a sim would be a god send to us all, I could only dream of getting my hands on one.
Just to clarify - the tail rotor auto thingy was just a scenario. A thought provoking question really. There was no intention of trying to use it to help in a T/R problem. I know for a fact that I would instictively try to boot in opposite peddal if I lost the T/R drive - that alone would be the end of the conversation of T/R auto.
I did throw in a comment on whether you could overspeed a tail rotor by having it in the 'auto' pitch setting (zero pitch) with a drive failure. Could there be a risk of exacerbating the problem if you threw off a T/R blade without even knowing it was going to happen?. Once again just a tongue in cheek thought. No need to do the tests.
I am going to have to back peddal a little now cos' on a previous post I talked about using a small amount of engine power on descent and landing when confronted with a T/R drive failure. As mentioned previously it is very important to know how each aircraft responds to various problems. I wrote the response with the B47 in mind. It was not my intention to use it as a generic answer to tail rotor problems although I guess it was centred on collective mounted, throttled helicopters. I was 'lucky' enough to work with a bloke who had a short shaft failure in a B47 whilst mustering. To this day he does not know how he flew away but I presume he had just enough residual forward speed and a hell of a lot of crossed controls. Anyway he was able to fly back to the station which had a gravel strip. When he rolled off the throttle completely to enter auto he found that the aircraft yawed to the left by a considerable amount. In the end he had the engine ever so slightly past the idle all the way to the ground and as he leveled he wound the throttle off completely and landed. All of this to the benefit of us young blokes.
To this date I have taken the example as gospel but always wondered whether the tail rotor had some residual thrust or if the position of the free wheel unit in the transmission played a part in the outcome. I don't know.
Reading the posts I have come to the conclusion that I could be in varying degrees of trouble if I use the same thought process for different aircraft. I am therefore following the thread with renewed interest and an open mind.
Shytorque's experience in the sim may be invaluable. Please note, as mentioned earlier there really does need to be a distinction between collective mounted throttles and power levers. The rules do change.
keep it coming.
To have access to a sim would be a god send to us all, I could only dream of getting my hands on one.
Just to clarify - the tail rotor auto thingy was just a scenario. A thought provoking question really. There was no intention of trying to use it to help in a T/R problem. I know for a fact that I would instictively try to boot in opposite peddal if I lost the T/R drive - that alone would be the end of the conversation of T/R auto.
I did throw in a comment on whether you could overspeed a tail rotor by having it in the 'auto' pitch setting (zero pitch) with a drive failure. Could there be a risk of exacerbating the problem if you threw off a T/R blade without even knowing it was going to happen?. Once again just a tongue in cheek thought. No need to do the tests.
I am going to have to back peddal a little now cos' on a previous post I talked about using a small amount of engine power on descent and landing when confronted with a T/R drive failure. As mentioned previously it is very important to know how each aircraft responds to various problems. I wrote the response with the B47 in mind. It was not my intention to use it as a generic answer to tail rotor problems although I guess it was centred on collective mounted, throttled helicopters. I was 'lucky' enough to work with a bloke who had a short shaft failure in a B47 whilst mustering. To this day he does not know how he flew away but I presume he had just enough residual forward speed and a hell of a lot of crossed controls. Anyway he was able to fly back to the station which had a gravel strip. When he rolled off the throttle completely to enter auto he found that the aircraft yawed to the left by a considerable amount. In the end he had the engine ever so slightly past the idle all the way to the ground and as he leveled he wound the throttle off completely and landed. All of this to the benefit of us young blokes.
To this date I have taken the example as gospel but always wondered whether the tail rotor had some residual thrust or if the position of the free wheel unit in the transmission played a part in the outcome. I don't know.
Reading the posts I have come to the conclusion that I could be in varying degrees of trouble if I use the same thought process for different aircraft. I am therefore following the thread with renewed interest and an open mind.
Shytorque's experience in the sim may be invaluable. Please note, as mentioned earlier there really does need to be a distinction between collective mounted throttles and power levers. The rules do change.
keep it coming.
Guest
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I have been holding back as I thought this may have been mentioned before but so far I haven't seen mention of this so I thought I might add my 2 cents. I have been shown a recovery from a low speed high power JAMMED pedal event. As the aircraft starts to rapidly rotate cyclic can be aplied toward a constant heading ie "stir" the cyclic in the opposite direction of aircraft rotation. It allows you to gain airspeed in a constant direction and lower power post translation to a point where the aircraft will once again fly in something close to balance.
Interestingly enough the instructor who demonstrated this tecnique subsequently experienced a loss of tail rotor and tail rotor gearbox in the hover and landed without rolling into a ball.
Interestingly enough the instructor who demonstrated this tecnique subsequently experienced a loss of tail rotor and tail rotor gearbox in the hover and landed without rolling into a ball.
Guest
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I agree that simulator training is a very valuable way to experiment with handling TR problems but would add the proviso that the simulation may be innacurate.
Having flown the FSI 212 sim at DFW several times it is easy to come away with the impression that a TR drive failure can be controlled fairly well. In an extreme example which was basically a bit of 'wazzing' I took off from the simulated aircraft carrier, had a loss of TR drive at about 65 KTS, flew the thing horribly cross controlled to about 1000' abeam the ship then autorotated back down to the deck and survived. I don't believe that to be a true representation of the a/c's behaviour. The SAS sim at Stockholm, on the other hand, is a newer generation. TR drive failures can be truly aerobatic events, generally resulting in the sim freezing with the 'world' inverted, to protect itself.
Having spoken to pilots that have had TR drive failures in two separate AS332 accidents, one happened in a relatively high power setting in level flight and even entering autorotation did not stop the rolling/pitching/yawing; the PNF had to retard the speed select levers before things settled down. The handling pilot compared the manouver to a lomcevak! (negative flick roll going vertical, in an aeroplane). They executed a text book ditching and were all saved. The other one happened in a descent at 70 kts after the pilot had diagnosed the probability of impending TR drive failure and was a far less dramatic event, again resulting in a perfect ditching with no casualties.
Yet another accident with a 330J in the cruise resulted in the a/c tumbling all the way down to the sea.
So, being aware of the variables and trying it out in a sim is great, but come the day there is a very good chance things may not go to plan.
I suppose that is one thing in favour of fenestron a/c; they should fly happily in a straight line at about 100 kts with no drive.
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Another day in paradise
Having flown the FSI 212 sim at DFW several times it is easy to come away with the impression that a TR drive failure can be controlled fairly well. In an extreme example which was basically a bit of 'wazzing' I took off from the simulated aircraft carrier, had a loss of TR drive at about 65 KTS, flew the thing horribly cross controlled to about 1000' abeam the ship then autorotated back down to the deck and survived. I don't believe that to be a true representation of the a/c's behaviour. The SAS sim at Stockholm, on the other hand, is a newer generation. TR drive failures can be truly aerobatic events, generally resulting in the sim freezing with the 'world' inverted, to protect itself.
Having spoken to pilots that have had TR drive failures in two separate AS332 accidents, one happened in a relatively high power setting in level flight and even entering autorotation did not stop the rolling/pitching/yawing; the PNF had to retard the speed select levers before things settled down. The handling pilot compared the manouver to a lomcevak! (negative flick roll going vertical, in an aeroplane). They executed a text book ditching and were all saved. The other one happened in a descent at 70 kts after the pilot had diagnosed the probability of impending TR drive failure and was a far less dramatic event, again resulting in a perfect ditching with no casualties.
Yet another accident with a 330J in the cruise resulted in the a/c tumbling all the way down to the sea.
So, being aware of the variables and trying it out in a sim is great, but come the day there is a very good chance things may not go to plan.
I suppose that is one thing in favour of fenestron a/c; they should fly happily in a straight line at about 100 kts with no drive.
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Another day in paradise
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Having experienced a tail rotor failure in a rather large Wastelands product from a 40ft hover over the sea, I can assure you all that the previous theory lessons, good though they are, go straight out of the window!!.
In my case there was no warning, the helo just started to turn. Both myself and the other pilot automatically applied full opposite boot, thus we were both aware that tail rotor control had been lost before the end of the first 360 degrees. The rate of turn was rapid and disorienting but lowering the collective immediately significantly reduced the rate of turn - albeit in mid plummet.
We hit hard and bounced out of the sea into hover No2 where the a/c started to turn again before droppping into the 'oggin and rolling over. All escaped with no injuries.
Two lessons learnt from this. 1.In a hover you must lower the lever quickly, hack the engine if you can and cushion the touchdown with collective. 2.If you dont have your shoulder harness locked in every hover you are a prat!
In my case there was no warning, the helo just started to turn. Both myself and the other pilot automatically applied full opposite boot, thus we were both aware that tail rotor control had been lost before the end of the first 360 degrees. The rate of turn was rapid and disorienting but lowering the collective immediately significantly reduced the rate of turn - albeit in mid plummet.
We hit hard and bounced out of the sea into hover No2 where the a/c started to turn again before droppping into the 'oggin and rolling over. All escaped with no injuries.
Two lessons learnt from this. 1.In a hover you must lower the lever quickly, hack the engine if you can and cushion the touchdown with collective. 2.If you dont have your shoulder harness locked in every hover you are a prat!
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212 Man and Flypro,
Glad we all agree then, on the simulator thing about possible inaccuracies. (Please read my post of 13th Feb, 22:43 hrs if you haven't already; where I mentioned "off model" programming by the sim manufacturer). My experiences on the 332 sim carrying out T/R failures of all types were interesting to say the least.
Some (very experienced) pilots were quite alarmed by the response of the "aircraft" (sim). However, they unanimously agreed that they had a far better chance of a survivable outcome following their sim training. If nothing else, a discussion of the possible different scenarios is extremely useful. The proof of the pudding came a few years after we began training RAF pilots; a military 330J (no floats!)was successfully ditched following a tail rotor spider failure. The pilot said afterwards that had he not done his sim training he knew the outcome would have been different.
Personally, I would rather have a total drive failure than a runaway to FULL maximum or minimum tail rotor pitch, at least on the Super Puma. Either of those was in our experience, uncontrollable in most flight regimes. If the tail rotor ran away to maximum positive pitch on that type we found that even pulling the collective up as far as it would physically go (clunk) would not stop the right yaw caused by this failure. You then end up in a rapid spiral climb at full power and rapidly run out of ideas (throw baggage into the tail rotor to fail tha drive? It was suggested by one pilot!).
Similarly, if the pitch ran to fully "negative", even shutting down the engines did not stop the left yaw. This results in a spiral descent, very nasty too.
This may well be so on many other types, which is probably why many are fitted with some sort of centering device for the hydraulic servo for the cable break / malfunction situation.
One thing is for certain these days. I always check the tail rotor components very thoroughly when it is my turn for the check 'A'! I have already discovered one newly re-conditioned (!) and faulty tail rotor control spider.
ShyT.
Glad we all agree then, on the simulator thing about possible inaccuracies. (Please read my post of 13th Feb, 22:43 hrs if you haven't already; where I mentioned "off model" programming by the sim manufacturer). My experiences on the 332 sim carrying out T/R failures of all types were interesting to say the least.
Some (very experienced) pilots were quite alarmed by the response of the "aircraft" (sim). However, they unanimously agreed that they had a far better chance of a survivable outcome following their sim training. If nothing else, a discussion of the possible different scenarios is extremely useful. The proof of the pudding came a few years after we began training RAF pilots; a military 330J (no floats!)was successfully ditched following a tail rotor spider failure. The pilot said afterwards that had he not done his sim training he knew the outcome would have been different.
Personally, I would rather have a total drive failure than a runaway to FULL maximum or minimum tail rotor pitch, at least on the Super Puma. Either of those was in our experience, uncontrollable in most flight regimes. If the tail rotor ran away to maximum positive pitch on that type we found that even pulling the collective up as far as it would physically go (clunk) would not stop the right yaw caused by this failure. You then end up in a rapid spiral climb at full power and rapidly run out of ideas (throw baggage into the tail rotor to fail tha drive? It was suggested by one pilot!).
Similarly, if the pitch ran to fully "negative", even shutting down the engines did not stop the left yaw. This results in a spiral descent, very nasty too.
This may well be so on many other types, which is probably why many are fitted with some sort of centering device for the hydraulic servo for the cable break / malfunction situation.
One thing is for certain these days. I always check the tail rotor components very thoroughly when it is my turn for the check 'A'! I have already discovered one newly re-conditioned (!) and faulty tail rotor control spider.
ShyT.
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Eden.
Sorry, I aint he. Not a clue what you are talking about,and I certainly did not transfer to light blue - there is a code you know!!
Shytorque (now where have I seen a bar with a very similar name?)
The RN and RAF SeaKing Simulators are both very good for practising tail rotor problems and certainly in the case of tail rotors stuck at high or low pitch they fly very much as the real aircraft does. For a tail rotor failure at height they rely on data supplied by Wastelands as nobody has had one for real yet (I think).
In the Sim, to retain any control whatsoever the a/c must first be dropped into autorotation (and quickly at that). Once established, if possible go for an engine off landing, if not you can try to reapply power and sometimes manage to arrest the rate of descent for long enough to position the a/c over more suitable terrain for the subsequent engine off.
Another unofficial technique for tail rotor failure that works well in theory and in the Sim is to shut one engine down and set the other one at low torque, just enough to counter friction within the transmission. The a/c then handles almost exactly as it would in a normal auto.
I think the large keel area of a SeaKing prevents it from immediately spinning after losing the tail rotor in forward flight and give one time to lower the lever.
Hope this helps!
Finge Et fuge (Bodge it and Scarper)
[This message has been edited by Flypro (edited 23 February 2001).]
Sorry, I aint he. Not a clue what you are talking about,and I certainly did not transfer to light blue - there is a code you know!!
Shytorque (now where have I seen a bar with a very similar name?)
The RN and RAF SeaKing Simulators are both very good for practising tail rotor problems and certainly in the case of tail rotors stuck at high or low pitch they fly very much as the real aircraft does. For a tail rotor failure at height they rely on data supplied by Wastelands as nobody has had one for real yet (I think).
In the Sim, to retain any control whatsoever the a/c must first be dropped into autorotation (and quickly at that). Once established, if possible go for an engine off landing, if not you can try to reapply power and sometimes manage to arrest the rate of descent for long enough to position the a/c over more suitable terrain for the subsequent engine off.
Another unofficial technique for tail rotor failure that works well in theory and in the Sim is to shut one engine down and set the other one at low torque, just enough to counter friction within the transmission. The a/c then handles almost exactly as it would in a normal auto.
I think the large keel area of a SeaKing prevents it from immediately spinning after losing the tail rotor in forward flight and give one time to lower the lever.
Hope this helps!
Finge Et fuge (Bodge it and Scarper)
[This message has been edited by Flypro (edited 23 February 2001).]
Guest
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Eden,
Intrigued but I don't know where your bar is.
I thought of my user name after spending a few years dodging large hawks that circle eastern parts looking for - Shyte! Torque is appropriate for someone in our line of work. I also now circle looking for - Shyte!
Someone else on this forum has copied it but he's not as subtle as me!
Intrigued but I don't know where your bar is.
I thought of my user name after spending a few years dodging large hawks that circle eastern parts looking for - Shyte! Torque is appropriate for someone in our line of work. I also now circle looking for - Shyte!
Someone else on this forum has copied it but he's not as subtle as me!
Guest
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it seems that a full right or left stuck pedal would be a highly improbable situation - simply because they aren't used to the extremes all that often - unless there's some reason why the pitch would continue to increase or decrease to its full stop position, I guess.... seems that most "stuck" pedal situations would occur during flight regimes where the amount of stuck pitch was appropriate....any thoughts?
Guest
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The RAF Puma flew for 20 years plus in a condition likely to give a hardover in yaw due to the lack of a centre-ing device in / on the servo mechanism. It would happen if you lost one of the 2 pull cables to the tail rotor hydraulic servo valve. On this type there is no manual reversion and no way of isolating the hydraulics.
We looked at this type of failure in the sim, and discovered it was probably irrecoverable, as I intimated earlier. I did some personal research in the mid 1980's and discovered that the Norwegian aircraft had a centre-ing device fitted. Myself and other QHIs afterwards bleated long and hard about this and I think we eventually got through to the powers-that-were, as all the RAF aircraft are, I believe now modded with a centre-ing device. If not, they Bl**dy should be!
Even with such a device fitted, a broken pitch control spider can still give a hardover. Check the UK AAIB site for the report on the S.Wales police helicopter that landed on the roof of a house last year.
It's worth all heli pilots training for this in a sim. It doesn't matter which type as long as the main blades go round in the same direction as your helicopter (otherwise the yaw directions can get a bit confusing). Many heli pilots believe that closing down the engines is the answer to all tail rotor malfunctions. It ain't!
ShyT.
[This message has been edited by ShyTorque (edited 24 February 2001).]
We looked at this type of failure in the sim, and discovered it was probably irrecoverable, as I intimated earlier. I did some personal research in the mid 1980's and discovered that the Norwegian aircraft had a centre-ing device fitted. Myself and other QHIs afterwards bleated long and hard about this and I think we eventually got through to the powers-that-were, as all the RAF aircraft are, I believe now modded with a centre-ing device. If not, they Bl**dy should be!
Even with such a device fitted, a broken pitch control spider can still give a hardover. Check the UK AAIB site for the report on the S.Wales police helicopter that landed on the roof of a house last year.
It's worth all heli pilots training for this in a sim. It doesn't matter which type as long as the main blades go round in the same direction as your helicopter (otherwise the yaw directions can get a bit confusing). Many heli pilots believe that closing down the engines is the answer to all tail rotor malfunctions. It ain't!
ShyT.
[This message has been edited by ShyTorque (edited 24 February 2001).]
Guest
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ShyTorque,
If the centering device you refer to is the tail rotor spring bias unit, then I think we are still waiting for it to be fitted (along with a torque meter/anticipators/Makila engines!). As you have said, the simulator is an invaluable tool to get you thinking about tail rotor malfunctions. I'm pretty sure that if it happens for real however, the 'What the f...' factor will precede the 'THROTTLES!' call by some distance!
If the centering device you refer to is the tail rotor spring bias unit, then I think we are still waiting for it to be fitted (along with a torque meter/anticipators/Makila engines!). As you have said, the simulator is an invaluable tool to get you thinking about tail rotor malfunctions. I'm pretty sure that if it happens for real however, the 'What the f...' factor will precede the 'THROTTLES!' call by some distance!
Guest
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Been following this thread with some interest. A couple of points/questions. I had a TR drive failure in a 204 over trees during longline ops (just powering up for a lift). I found the most surprising element of the failure was the severe nose tuck almost immediately drive to the TR was lost. It required almost full aft left cyclic input to maintain a wings level attitude during the early part of the rotation. I was lucky in that I identified the failure early and shut the throttle after 180 degrees of rotation which immediately stopped the rotation and levelled the aircraft. The trip down thru the trees was "intersting" but both myself and my co are here to tell the story today.
I have never done any sim time but I am intereted to know whether the 212 sim replicates similar tendencies to what I experienced. Also over a number of years of flying I have never heard any instructor discuss this point when briefing for TR failure. Any thoughts?
PS
Loss of drive to the TR was caused by the failure of the grease coupling on the TR driveshaft immediately aft of the TR output quill on the Trans. As a point of note never trust the Zinc chromate paint lines on the couplings to indicate high coupling temps. The Bell temp indicating strips (like they use on the R22) are the only way to go!
I have never done any sim time but I am intereted to know whether the 212 sim replicates similar tendencies to what I experienced. Also over a number of years of flying I have never heard any instructor discuss this point when briefing for TR failure. Any thoughts?
PS
Loss of drive to the TR was caused by the failure of the grease coupling on the TR driveshaft immediately aft of the TR output quill on the Trans. As a point of note never trust the Zinc chromate paint lines on the couplings to indicate high coupling temps. The Bell temp indicating strips (like they use on the R22) are the only way to go!
Guest
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This will probably be common knowledge to most of you, however, it was certainly news to me at the time.
Flying the 412 sim at DFW I was given a tail rotor drive shaft failure in forward flight. The drill is to enter autorotation immediately but my instructor suggested that I continue flying (80kts) and see what happend.
Horrible right yaw and nose tuck ensued, but it was certainly controllable, so we decided to return to the airfield for an autorotation. As the airfield was in our 4 0'clock position I began a gentle turn to the right (into the yaw). Bad move. We very quickly lost all airspeed and began to lose control of the beast.
If you need to turn, then turn away from the yaw as it is much easier to maintain airspeed.
Flying the 412 sim at DFW I was given a tail rotor drive shaft failure in forward flight. The drill is to enter autorotation immediately but my instructor suggested that I continue flying (80kts) and see what happend.
Horrible right yaw and nose tuck ensued, but it was certainly controllable, so we decided to return to the airfield for an autorotation. As the airfield was in our 4 0'clock position I began a gentle turn to the right (into the yaw). Bad move. We very quickly lost all airspeed and began to lose control of the beast.
If you need to turn, then turn away from the yaw as it is much easier to maintain airspeed.
Guest
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To:212 Man
“Does it not depend where the centre of pressure acts relative to the feathering axis and hence how the centripetal turning moment moves the pitch”?
Hopefully this does not start another international incident due to semantics but I believe you are talking about “Centrifugal twisting moment”. The centrifugal twisting moment coupled with the aerodynamic forces are what you feel when you move the pedals during flight, or in other words, you experience the associated feed back. Propellers on aircraft have the same condition. If say on a Hydromatic propeller you lose oil pressure the centrifugal twisting moment will return the blades to low pitch and if you don’t catch it quick enough you can have a runaway engine.
To: Imlanphere
“I believe I read somewhere that if the pitch control mechanism were to be severed somehow the tail rotor blades would work themselves back to zero pitch automatically, but maybe that’s type dependent.”
You are correct in stating that the return to low pitch is type dependent. Some helicopters that do not incorporate compensating weight would return to flat pitch if the control were severed. Many helicopters incorporate dynamic or static counterweights. The static weights are incorporated as a part of the blade on the Bell 407. Helicopters like the Sikorsky S-58 incorporate dynamic counter weights that move when the tail rotor pitch is changed. The purpose of these weights is to counter the centrifugal twisting moment so that the pilot only experiences the aerodynamic forces if he has to fly with the tail rotor boost shut off. On this type of tail rotor the dynamic or static weights will under ideal conditions maintain the blade pitch in the last commanded position when control is severed.
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The Cat
“Does it not depend where the centre of pressure acts relative to the feathering axis and hence how the centripetal turning moment moves the pitch”?
Hopefully this does not start another international incident due to semantics but I believe you are talking about “Centrifugal twisting moment”. The centrifugal twisting moment coupled with the aerodynamic forces are what you feel when you move the pedals during flight, or in other words, you experience the associated feed back. Propellers on aircraft have the same condition. If say on a Hydromatic propeller you lose oil pressure the centrifugal twisting moment will return the blades to low pitch and if you don’t catch it quick enough you can have a runaway engine.
To: Imlanphere
“I believe I read somewhere that if the pitch control mechanism were to be severed somehow the tail rotor blades would work themselves back to zero pitch automatically, but maybe that’s type dependent.”
You are correct in stating that the return to low pitch is type dependent. Some helicopters that do not incorporate compensating weight would return to flat pitch if the control were severed. Many helicopters incorporate dynamic or static counterweights. The static weights are incorporated as a part of the blade on the Bell 407. Helicopters like the Sikorsky S-58 incorporate dynamic counter weights that move when the tail rotor pitch is changed. The purpose of these weights is to counter the centrifugal twisting moment so that the pilot only experiences the aerodynamic forces if he has to fly with the tail rotor boost shut off. On this type of tail rotor the dynamic or static weights will under ideal conditions maintain the blade pitch in the last commanded position when control is severed.
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The Cat
