Entering autos: discussion split from Glasgow crash thread
this is the ONLY control movement that will lead to stopping and reversing the falling rotor rpm
With respect, that's not considered to be correct in UK (mil) teaching - which I believe still includes a demonstration of Nr decay caused by rolling the (only) throttle to idle in the cruise, and doing nothing with the controls. The recovery from the ensuing rapid Nr decay was always to lower the lever to prevent further decay, then flare to restore the Nr. Perhaps someone currently active at Shawbury can confirm?
TOTD
Pete: a few points from you explanation:
Depending on the situation you are in, a little turn while you are lowering the nose if you are adjusting airspeed can load the head a bit and keep the inertia from bleeding off ... but as that's situation dependent, in terms of where you are trying to land, a "hard and fast rule" on that might do as much harm as good.
I am beginning to appreciate a deeper side to your crusade: if your Nr is in the green and your airspeed ends up a bit low, you have some seconds where you can try to make an adjustment, whereas if you end up pushing down for airspeed, particularly in a low inertia head, the Nr decay from unloading the head may leave you where you are not able to make an adjustment since those wings aren't flying anymore.
As with a few more % Nr near the bottom ... in which direction would you rather be in error? In that light, your PoV and your emphasis on keeping the head loaded, with the cyclic, is a bit clearer.
Also: Thanks for your further explanation of the mishaps you investigated.
- The movement should be as instant as possible and done so there is no doubt that positive g's are being applied to the airframe.
The ONLY airspeed that matters at that moment is the airspeed over the wings, which, of course, means the rotor blades.- ... catch the rotor rpm before it drops to the critical point. NOW you have a flying machine and can then dial in whatever airspeed you'd like, but be careful when nosing over because the rotor rpm you've just saved will disappear in a heartbeat if you push over aggressively. Keep an eye on the rotor tach as you lower the nose to gain speed.
I am beginning to appreciate a deeper side to your crusade: if your Nr is in the green and your airspeed ends up a bit low, you have some seconds where you can try to make an adjustment, whereas if you end up pushing down for airspeed, particularly in a low inertia head, the Nr decay from unloading the head may leave you where you are not able to make an adjustment since those wings aren't flying anymore.
As with a few more % Nr near the bottom ... in which direction would you rather be in error? In that light, your PoV and your emphasis on keeping the head loaded, with the cyclic, is a bit clearer.
Also: Thanks for your further explanation of the mishaps you investigated.
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Lonewolf
I think there is an issue of context.
In my earlier post I was surmising as to those possibilities which exist which could have accounted for why an experienced pilot might delay in his response to controlling Nr. It was (and is) within this context that I am highlighting what I originally described as a mindset among multi-engine pilots which (for the right reasons) will seek clarification of an engine failure for the very purpose you stated "to help you do something other than fly that auto down to the bottom."
Nr control is what is required, most especially in the case of a double engine failure, but I am suggesting that on a "bad day" as you put it, it may be possible for a pilot to unintentionally delay their response to Nr control (for the reasons given), particularly if they have the hope/expectation that one engine remains operative and particularly if they do not want to sacrifice height.
I think there is an issue of context.
In my earlier post I was surmising as to those possibilities which exist which could have accounted for why an experienced pilot might delay in his response to controlling Nr. It was (and is) within this context that I am highlighting what I originally described as a mindset among multi-engine pilots which (for the right reasons) will seek clarification of an engine failure for the very purpose you stated "to help you do something other than fly that auto down to the bottom."
Nr control is what is required, most especially in the case of a double engine failure, but I am suggesting that on a "bad day" as you put it, it may be possible for a pilot to unintentionally delay their response to Nr control (for the reasons given), particularly if they have the hope/expectation that one engine remains operative and particularly if they do not want to sacrifice height.
Thank you, sir, for the clarification. If I read something into your initial points, the fault is mine.
Cheers.
If I read something into your initial points, the fault is mine. Cheers.
It's funny. Pete Gillies obviously "gets it" while some of you clearly don't.
Please let us all understand that Pete did not mean that we should emply "Cyclic Back" when the ship is in a hover. Puh-leeze. He obviously meant that it should be used during forward flight, which is what we're talking about here, right? I mean, no one was suggesting (and witnesses agree) that the Glasgow a/c was not in an OGE hover when that something bad happened.
And Pete is right.
TC says:
Wrong. Just plain wrong, at least as far as forward flight is concerned, "Aft cyclic first" works. "Collective first" can be deadly.
Say you were cruising along at 500' agl in your Astar or 206 or 500...or even your S-76. This is a not-uncommon scenario. Most helicopters cruise with the tip-path plane at a low-to-negative angle of attack vs. the relative wind. Now the engine quits unexpectedly. If you dump the collective first, before making an attitude adjustment the nose will drop and the helicopter will begin a descent. Now you start coming back with the cyclic; will you arrest the descent? Probably not. You've severely handicapped yourself.
In the same scenario, if you quickly bring the nose up first (even before doing anything with the collective), you're getting the relative wind under the disk (which you need) and at the same time loading the rotor to increase RPM. A happy result is that the helicopter might not even begin descending as it decelerates to best-auto speed. "HC" understands this. "H-500" understands this. They get it.
This is what Pete Gillies is trying to communicate to you. It is surprising-bordering-on-shocking that so many of you seem to not only not understand it, but some even disagree!
It would be nice if all helicopter pilots always had their hands on both controls so that the response to a complete power failure would be an immediate, coordinated reduction in collective pitch with a corresponding raising of the a/c pitch attitude. But that's not reality. We rest our cyclic hand on our knee. But you cannot "rest your hand" on the collective without eventually pushing it down unless there's sufficient friction applied to keep it from moving. Keeping your hand on the collective all the time is a fatiguing way to fly when there's no one else in the cockpit to take the controls and give you a break once in a while. So we rest our collective hand on our (left) knee too.
"Collective first" is fine if you're already back at best-auto speed, with the disk level. (But even so, "cyclic first" won't be harmful as long as you don't hold that attitude until all your speed goes away.) But in cruise, with the main rotor tilted forward...I dunno...you've got to get the angle of atack of the disk up.
I'm firmly with Pete: In forward flight, "cyclic-back-first" is never wrong. And I'm proud that he's got the guts to go against the conventional wisdom of the (self-appointed) so-called experts on this board.
Please let us all understand that Pete did not mean that we should emply "Cyclic Back" when the ship is in a hover. Puh-leeze. He obviously meant that it should be used during forward flight, which is what we're talking about here, right? I mean, no one was suggesting (and witnesses agree) that the Glasgow a/c was not in an OGE hover when that something bad happened.
And Pete is right.
TC says:
...one can NEVER ever make the statement: aft cyclic first and then collective. But one can ALWAYS say: collective first and then cyclic. Because of this - I stand fast with this ethos.
Say you were cruising along at 500' agl in your Astar or 206 or 500...or even your S-76. This is a not-uncommon scenario. Most helicopters cruise with the tip-path plane at a low-to-negative angle of attack vs. the relative wind. Now the engine quits unexpectedly. If you dump the collective first, before making an attitude adjustment the nose will drop and the helicopter will begin a descent. Now you start coming back with the cyclic; will you arrest the descent? Probably not. You've severely handicapped yourself.
In the same scenario, if you quickly bring the nose up first (even before doing anything with the collective), you're getting the relative wind under the disk (which you need) and at the same time loading the rotor to increase RPM. A happy result is that the helicopter might not even begin descending as it decelerates to best-auto speed. "HC" understands this. "H-500" understands this. They get it.
This is what Pete Gillies is trying to communicate to you. It is surprising-bordering-on-shocking that so many of you seem to not only not understand it, but some even disagree!
It would be nice if all helicopter pilots always had their hands on both controls so that the response to a complete power failure would be an immediate, coordinated reduction in collective pitch with a corresponding raising of the a/c pitch attitude. But that's not reality. We rest our cyclic hand on our knee. But you cannot "rest your hand" on the collective without eventually pushing it down unless there's sufficient friction applied to keep it from moving. Keeping your hand on the collective all the time is a fatiguing way to fly when there's no one else in the cockpit to take the controls and give you a break once in a while. So we rest our collective hand on our (left) knee too.
"Collective first" is fine if you're already back at best-auto speed, with the disk level. (But even so, "cyclic first" won't be harmful as long as you don't hold that attitude until all your speed goes away.) But in cruise, with the main rotor tilted forward...I dunno...you've got to get the angle of atack of the disk up.
I'm firmly with Pete: In forward flight, "cyclic-back-first" is never wrong. And I'm proud that he's got the guts to go against the conventional wisdom of the (self-appointed) so-called experts on this board.
GF and Lonewolf - I think there may be a disconnect here due to the cultural differences in how twins are operated. In the USA, as far as I am aware there is little concept of performance. If you go OEI you may or may not fall to earth, so you might as well just be in a single. Here in the UK we operate PC1 or 2, at least when we have passengers, and so the expectation when having an engine failure is that the flight will be continued. I am obviously on GF's side here, the multi pilot will not and should not react to an engine failure by dumping the collective, but as GF says that does create a probable longer reaction time to a simultaneous double engine failure. You would for example be considered a complete plonker if you went OEI coming off a rig in the N Sea, dumped the collective to enter auto and ended up in the water, when you could easily have flown away OEI. The correct response to an engine failure just on rotation from offshore (highly unlikely as that is) is to not move the collective for the couple of seconds it takes for the tail to clear the deck edge. Any significant lowering of the collective at that point is likely to wipe the tail of and result in fatalities.
You can argue until the cows come home about whether this is the right or wrong way to operate, but for the time being that is how it is over here.
You can argue until the cows come home about whether this is the right or wrong way to operate, but for the time being that is how it is over here.
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Lonewolf
HeliComparator understands very well my perspective and which I partly summarised in my original post when writing:
HeliComparator understands very well my perspective and which I partly summarised in my original post when writing:
However, on those rare occasions when a double engine failure occurs, it is possible to see how a multi-engine pilot may not instantly take the required action in the same way as a single engine pilot would, and for the right reasons, because the multi-engine pilot must assess the nature of the power failure, even if it is to determine that both engines have failed. In a single, any sort of interruption to powered flight is not only obvious but it is equally obvious that there is no recourse (ie. only one possible action to be taken). This is not the "normal" mindset of a multi-engine pilot who will be trained to recover from a power failure with partially powered flight from the remaining engine.
Just a thought... Regarding emergency auto entry from cruising flight, we seem to be stuck somewhere between dumping collective then thinking about the cyclic afterwards, dumping the collective and maintaining the attitude, simultaneously dumping the collective and moving the cyclic back, and leading with the aft cyclic prior to moving the collective. One of the problems with "maintaining the attitude" is that, with a large and rapid movement of the collective comes a significant attitude upset (more so in some types than others) and to apply the correct amount of cyclic to maintain the attitude is not that easy especially bearing in mind the rapidity of the effect of dumping the collective vs the relatively slow response in pitch attitude to cyclic being fought by a SAS, muddied by probable yaw and its own effect on pitch attitude.
Therefore my suggestion is that the pitch attitude is not the thing to go for. It is hard to judge accurately under dynamic conditions (think IMC), you have to be looking in the right place when really you want to be looking at the Nr gauge, and ultimately it is not an important parameter. What is important is the restoration of Nr and there is one primary parameter that affects this (other than collective pitch) and that is g loading.
G loading is also very easy to assess - the body is pretty good at it. So what we need to do is to aim for at least 1 g, maybe a little more, in the first moments after a double engine failure is recognised.
Therefore my recommendation in the event of a need for emergency auto entry, is to lower the collective whilst moving the cyclic back to maintain at least 1g. If 1g or more is maintained, there will be little or no height lost in the first moments which satisfies those flying fast near the ground. Since the responsiveness of the cyclic depends on current g, leading with the collective will instantly reduce g and make it harder to regain it with cyclic. Therefore it is necessary to lead with cyclic, so as to maintain 1g or more throughout the early stages of entry.
I'm sure this is what we actually do, but I'm not sure anyone has vocalised it yet?
To reiterate, all this from cruising flight. As you can tell, I remain in full agreement with PG!
Therefore my suggestion is that the pitch attitude is not the thing to go for. It is hard to judge accurately under dynamic conditions (think IMC), you have to be looking in the right place when really you want to be looking at the Nr gauge, and ultimately it is not an important parameter. What is important is the restoration of Nr and there is one primary parameter that affects this (other than collective pitch) and that is g loading.
G loading is also very easy to assess - the body is pretty good at it. So what we need to do is to aim for at least 1 g, maybe a little more, in the first moments after a double engine failure is recognised.
Therefore my recommendation in the event of a need for emergency auto entry, is to lower the collective whilst moving the cyclic back to maintain at least 1g. If 1g or more is maintained, there will be little or no height lost in the first moments which satisfies those flying fast near the ground. Since the responsiveness of the cyclic depends on current g, leading with the collective will instantly reduce g and make it harder to regain it with cyclic. Therefore it is necessary to lead with cyclic, so as to maintain 1g or more throughout the early stages of entry.
I'm sure this is what we actually do, but I'm not sure anyone has vocalised it yet?
To reiterate, all this from cruising flight. As you can tell, I remain in full agreement with PG!
In the USA, as far as I am aware there is little concept of performance.
Same company....same aircraft.....some kind of task....but different Standards?
Sometimes i wonder how we ever manage to survive in the USA....considering just how little we seem to know about helicopter flying as thought by some here.
HC....there is a huge difference between "Knowing" and "Doing"....and some Operators might ignore the EASA concepts of PC1 and all that....or as in the old days....Cat A.
But oddly, times do change even in the good ol' USA.
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Thank you, gentlemen. In reviewing the many posts I see several that claim lowering or bottoming the lever will stop the rotor rpm from decreasing. This is not true! This action does nothing more than reduce the rate at which the rotor rpm is falling. Period! It will continue to fall unless aft cyclic is applied in time to keep the rpm above the critical point.
Yes, with the rotor somewhere in the green, a turn during the descent will increase the rotor rpm, and this can be very handy when maneuvering to make a spot and will help keep the rotor rpm happy.
With the rotor rpm in the green, the helicopter can do any maneuver it can do with the engine(s) running except a sustained climb (from my initial post). As for picking a spot to land, I emphasize picking one that's too close. The pilot can handle too close, too high and too fast. Those are wonderful things to have. The opposites are not (too far away, etc.). And descending vertically works beautifully, especially if one has lots of altitude to get rid of. The high rate of descent is not a problem at all and the helicopter responds to all pedal and cyclic movements needed to keep the landing spot in full view of the pilot. A smooth forward movement of the cyclic quickly returns the descent to normal for the autorotation. I definitely prefer vertical descents to S turns or 360s. Keep the spot in view during the descent if at all possible. Ah, don't get me started on the mode of flight the helicopter prefers if given a choice... Think I'm kidding? Just ask your helicopter. It will answer that if you could fly all the time with the engine(s) not running, it would be wonderful!
My comments are directly aimed at the utility pilot doing field operations, not flying around the aerodrome or the practice area in a relatively sanitary training environment.
As for responding to falling rotor rpm in a twin, I think it is a huge mistake to do any troubleshooting before bringing the cyclic back and lowering the lever. Move the controls first, and THEN do the troubleshooting. The drive shaft failure in Twin-Pac powered machines is an example. Even if it is the failure of one engine, applying aft cyclic and lowering the lever a bit can help the remaining engine pick up the load.
It's time again for me to express my appreciation for the support of my efforts to make Cyclic Back a part of all training and publications everywhere.
Pete Gillies
Yes, with the rotor somewhere in the green, a turn during the descent will increase the rotor rpm, and this can be very handy when maneuvering to make a spot and will help keep the rotor rpm happy.
With the rotor rpm in the green, the helicopter can do any maneuver it can do with the engine(s) running except a sustained climb (from my initial post). As for picking a spot to land, I emphasize picking one that's too close. The pilot can handle too close, too high and too fast. Those are wonderful things to have. The opposites are not (too far away, etc.). And descending vertically works beautifully, especially if one has lots of altitude to get rid of. The high rate of descent is not a problem at all and the helicopter responds to all pedal and cyclic movements needed to keep the landing spot in full view of the pilot. A smooth forward movement of the cyclic quickly returns the descent to normal for the autorotation. I definitely prefer vertical descents to S turns or 360s. Keep the spot in view during the descent if at all possible. Ah, don't get me started on the mode of flight the helicopter prefers if given a choice... Think I'm kidding? Just ask your helicopter. It will answer that if you could fly all the time with the engine(s) not running, it would be wonderful!
My comments are directly aimed at the utility pilot doing field operations, not flying around the aerodrome or the practice area in a relatively sanitary training environment.
As for responding to falling rotor rpm in a twin, I think it is a huge mistake to do any troubleshooting before bringing the cyclic back and lowering the lever. Move the controls first, and THEN do the troubleshooting. The drive shaft failure in Twin-Pac powered machines is an example. Even if it is the failure of one engine, applying aft cyclic and lowering the lever a bit can help the remaining engine pick up the load.
It's time again for me to express my appreciation for the support of my efforts to make Cyclic Back a part of all training and publications everywhere.
Pete Gillies
In reviewing the many posts I see several that claim lowering or bottoming the lever will stop the rotor rpm from decreasing.
This is not true!
This action does nothing more than reduce the rate at which the rotor rpm is falling.
It will continue to fall unless aft cyclic is applied in time to keep the rpm above the critical point.
This is not true!
This action does nothing more than reduce the rate at which the rotor rpm is falling.
It will continue to fall unless aft cyclic is applied in time to keep the rpm above the critical point.
Pete,
Every time I am about to agree with you....making some allowance for wording.....you throw me another curve ball.
Are you saying a fully bottomed Collective, in fully established Autorotation (in a properly rigged helicopter), will not result in a safe Rotor RPM......and that the only way to achieve a safe Rotor RPM is by use of a decelerative maneuver using Cyclic?
You say the RPM will fall until it reaches the "Critical Point".....are you saying the "Critical Point" is where the Rotor can no longer be driven by air moving upward through the Rotor System and thus the Rotor will continue to decrease in RPM till it no longer facilitates an autorotative landing?
Answer a few other questions please.
Every Aircraft Type Maintenance Manual has a procedure for calculating and checking for Autorotational RPM.
As part of routine maintenance and checking for air worthiness....that Check is done using the approved procedure.
The Target RPM always falls within the authorized Power Off RPM Limits set forth by the Manufacturer of the Helicopter.
That Target RPM is not the "Critical" RPM that has been discussed here in the definition of the RPM at which loss of rotational drive in autorotation is lost.
As I read your post quoted above.....I interpret it to say a properly rigged Helicopter will never stabilize Main Rotor RPM in a steady state Autorotation.
Am I not understanding what you are trying to say?
SAS - Putting my merry quips in red into your post:
Company SOP's differ between the GOM and the North Sea do they?
Of course, you don't think we would want to fly crazy like you do over there?
Same company....same aircraft.....some kind of task....but different Standards?
Yup, and your point is?.... But of course in reality, not the same aircraft in general - you are happy to fly folk around over the ocean in singles!
Sometimes i wonder how we ever manage to survive in the USA....considering just how little we seem to know about helicopter flying as thought by some here.
Fortunately there are a lot of you to start with.
HC....there is a huge difference between "Knowing" and "Doing"....and some Operators might ignore the EASA concepts of PC1 and all that....or as in the old days....Cat A.
But oddly, times do change even in the good ol' USA.
Yes I think they are actually, but only in the last few years. Certainly when the "globalisation" of Bristow was going on, maybe 10 years ago max, S76 was being operated GoM without any concept of OEI performance. Not sure if LW has caught up with that concept - seems not from his postings.
Of course, you don't think we would want to fly crazy like you do over there?
Same company....same aircraft.....some kind of task....but different Standards?
Yup, and your point is?.... But of course in reality, not the same aircraft in general - you are happy to fly folk around over the ocean in singles!
Sometimes i wonder how we ever manage to survive in the USA....considering just how little we seem to know about helicopter flying as thought by some here.
Fortunately there are a lot of you to start with.
HC....there is a huge difference between "Knowing" and "Doing"....and some Operators might ignore the EASA concepts of PC1 and all that....or as in the old days....Cat A.
But oddly, times do change even in the good ol' USA.
Yes I think they are actually, but only in the last few years. Certainly when the "globalisation" of Bristow was going on, maybe 10 years ago max, S76 was being operated GoM without any concept of OEI performance. Not sure if LW has caught up with that concept - seems not from his postings.
...and again...
Are you saying a fully bottomed Collective, in fully established Autorotation (in a properly rigged helicopter), will not result in a safe Rotor RPM......and that the only way to achieve a safe Rotor RPM is by use of a decelerative maneuver using Cyclic?
...
Every Aircraft Type Maintenance Manual has a procedure for calculating and checking for Autorotational RPM.
Stabilised at 1 g
As part of routine maintenance and checking for air worthiness....that Check is done using the approved procedure.
Stabilised at 1g
The Target RPM always falls within the authorized Power Off RPM Limits set forth by the Manufacturer of the Helicopter.
When stabilised at 1g
As I read your post quoted above.....I interpret it to say a properly rigged Helicopter will never stabilize Main Rotor RPM in a steady state Autorotation.
It will, but entry into autorotation is not a steady state. It may be that by the time steady state is reached, rrpm has fallen too far and the steady state becomes one of a brick.
Am I not understanding what you are trying to say?
Obviously not!
Are you saying a fully bottomed Collective, in fully established Autorotation (in a properly rigged helicopter), will not result in a safe Rotor RPM......and that the only way to achieve a safe Rotor RPM is by use of a decelerative maneuver using Cyclic?
...
Every Aircraft Type Maintenance Manual has a procedure for calculating and checking for Autorotational RPM.
Stabilised at 1 g
As part of routine maintenance and checking for air worthiness....that Check is done using the approved procedure.
Stabilised at 1g
The Target RPM always falls within the authorized Power Off RPM Limits set forth by the Manufacturer of the Helicopter.
When stabilised at 1g
As I read your post quoted above.....I interpret it to say a properly rigged Helicopter will never stabilize Main Rotor RPM in a steady state Autorotation.
It will, but entry into autorotation is not a steady state. It may be that by the time steady state is reached, rrpm has fallen too far and the steady state becomes one of a brick.
Am I not understanding what you are trying to say?
Obviously not!
HC:
Well, if I had said "DUMP COLLECTIVE" we'd be having a different conversation. I did say "control Nr" which may mean lower the collective a little or a lot or to the bottom, whatever it takes (your eyes going to Nr in parallel, not in serial) and likely your cyclic probably giving slightly aft pressure, as you don't want to dump the nose ... anyhoo, let's not argue with what someone didn't say, alright?
Pete:
We are in violent agreement.
HC:
The core point on keeping the head loaded, versus unloading it, seems to be the core point of agrement, about which the disagreement seems to go round and round. If one delays lowering the collective (be it a little or a lot) and thus keeping pitch on the blades, the decay of Nr seems a foregone conclusion.
Pete:
Collective full down, with an Nr above the stalled Nr, I would expect to see Nr stabilize at the rigged Nr when descending at the usual autorotational airspeed (a range of values for any helicopter).
And as HC repeats what I raised earlier, we seem to actually be in violent agreement: you don't move the controls independently of one another, you tend to work them together ... and keep the lead loaded so it will perform as you more or less expect it to in re its autorotatoinal properties.
What Pete's short summary on those mishaps points to is people unloading the head in a hurry and perhaps not realizing that they are unloading the head ... and thus changing the nature of the airflow and AoA through the rotor system.
I note in your latest, Pete, that you have refined your point to a particular regime of flying where there is not a lot of stored energy in terms of arispeed to trade for Nr. With your crusade aimed at a particular flight regime, and given what else you have shared, it makes it clearer what informs your concerns in the first place.
Bombing along at max range airspeed (and with a lot of knots to trade for Nr) is a different case, though perhaps the Mosby crash serves as ample warning that one cannot be complacent.
HC
You lot were a couple of decades late to the show, seems to me.
As I don't fly, nor ever flew the S76, why was that crap tossed at me?
In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?) We also had to practice, over and over, single engine landings to a spot at constant descent angle. Gee, I wonder why we did that?
Started for me in about 1982.
Well, if I had said "DUMP COLLECTIVE" we'd be having a different conversation. I did say "control Nr" which may mean lower the collective a little or a lot or to the bottom, whatever it takes (your eyes going to Nr in parallel, not in serial) and likely your cyclic probably giving slightly aft pressure, as you don't want to dump the nose ... anyhoo, let's not argue with what someone didn't say, alright?
Pete:
Move the controls first, and THEN do the troubleshooting
HC:
The core point on keeping the head loaded, versus unloading it, seems to be the core point of agrement, about which the disagreement seems to go round and round. If one delays lowering the collective (be it a little or a lot) and thus keeping pitch on the blades, the decay of Nr seems a foregone conclusion.
Pete:
Collective full down, with an Nr above the stalled Nr, I would expect to see Nr stabilize at the rigged Nr when descending at the usual autorotational airspeed (a range of values for any helicopter).
And as HC repeats what I raised earlier, we seem to actually be in violent agreement: you don't move the controls independently of one another, you tend to work them together ... and keep the lead loaded so it will perform as you more or less expect it to in re its autorotatoinal properties.
What Pete's short summary on those mishaps points to is people unloading the head in a hurry and perhaps not realizing that they are unloading the head ... and thus changing the nature of the airflow and AoA through the rotor system.
I note in your latest, Pete, that you have refined your point to a particular regime of flying where there is not a lot of stored energy in terms of arispeed to trade for Nr. With your crusade aimed at a particular flight regime, and given what else you have shared, it makes it clearer what informs your concerns in the first place.
Bombing along at max range airspeed (and with a lot of knots to trade for Nr) is a different case, though perhaps the Mosby crash serves as ample warning that one cannot be complacent.
HC
maybe 10 years ago max, S76 was being operated GoM without
any concept of OEI performance. Not sure if LW has caught up with that concept - seems not from his postings.
You lot were a couple of decades late to the show, seems to me.
As I don't fly, nor ever flew the S76, why was that crap tossed at me?
In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?) We also had to practice, over and over, single engine landings to a spot at constant descent angle. Gee, I wonder why we did that?
Started for me in about 1982.
Last edited by Lonewolf_50; 17th Dec 2013 at 18:52.
HC....we live in a 1G world don't we.....anything over that is not a normal situation.....or is gravity more intense where you live?
Perhaps your control touch left you thinking a 1G+ feeling in your hind end was normal?
Care to offer a serious answer to the questions?
Perhaps your control touch left you thinking a 1G+ feeling in your hind end was normal?
Care to offer a serious answer to the questions?
HC:
As I don't fly, nor ever flew the S76, why was that crap tossed at me, HC? In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?)
Started for me in about 1982.
As I don't fly, nor ever flew the S76, why was that crap tossed at me, HC? In the twin engine helicopters I flew, we had separate performance charts for SE operations. SEAS was a critical T/O (reaching and passing) and Approach (going below) call out in the cockpit. Gee, I wonder why we did that, flying off of small deck ships. Care to share your pet theories? (Where is a sarcasm smiley when you need one?)
Started for me in about 1982.
Wading through a lot of waffle and bickering on this thread, I do think this point may be critically relevant to the original topic (135 accident, in case we have forgotten!)
Do you really not "get" that when you rapidly lower the collective in response to a complete loss of engine drive, without moving the cyclic, the g will fall to near zero or even below if you are in the cruise, and thus the Nr will continue to decay despite collective on the floor. Scary if so. I do hope you are just being obtuse!
Last edited by HeliComparator; 17th Dec 2013 at 19:11.
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Pete is 100% on the money, Aft cyclic in forward flight will delay RPM decay even with a delaied lowering of collective! Army/NASA tests on Rotor RPM on the low side with the Bell OH 5 found powered flight to 70% & no recovery without power posable. parachute required.
Bash & trash all you want that's pride messing with you.
(Still remember that 500 with the log stickin out the pilots floor.)
Bash & trash all you want that's pride messing with you.
(Still remember that 500 with the log stickin out the pilots floor.)