R44 Down on Melbourne Beach
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If this is not already in the Robinson safety course - it should be.
Is LTE recovery (by the book) any different from LTR recovery?
Not in this situation! Lowering pitch: yes, but rolling off throttle would have depressed the RRPM still further.
The RRPM values sound somewhere near complete stall in the video: roll ON and lower! It's the action the pilot clearly didn't take (insufficient drill?) and the situation deteriorated very rapidly from there.
They were incredibly lucky to survive. At the point where the aircraft moves horizontally over the water, the alarm stops: probably got an RRPM gain through increasing translational lift at that point: then the alarm goes off again! My guess would would be gripping the throttle due to stress and impeding the governor.
TT
The RRPM values sound somewhere near complete stall in the video: roll ON and lower! It's the action the pilot clearly didn't take (insufficient drill?) and the situation deteriorated very rapidly from there.
They were incredibly lucky to survive. At the point where the aircraft moves horizontally over the water, the alarm stops: probably got an RRPM gain through increasing translational lift at that point: then the alarm goes off again! My guess would would be gripping the throttle due to stress and impeding the governor.
TT
Last edited by Torquetalk; 15th Sep 2009 at 14:10. Reason: Error edit
The Robinson safety notice says it all - the pilot was unaware of the increase in power required as the IAS fell and ETL was lost - subconsciously probably raising the lever to maintain height and slowly decaying the Nr (thus further reducing the TR effectiveness).
Then, when it starts to spin, a reluctance to lower the lever sets off the Nr warner, the Nr droops further, increasing the RoD and the yaw because the TR isn't spinning fast enough. It takes him nearly 2000' to do what he should have done in the first place - lower the lever!
Then, when it starts to spin, a reluctance to lower the lever sets off the Nr warner, the Nr droops further, increasing the RoD and the yaw because the TR isn't spinning fast enough. It takes him nearly 2000' to do what he should have done in the first place - lower the lever!
N5296s
This page may help Helicopter Safety | Loss of Tail Rotor Effectiveness [LTE] there are a couple of documents part way down the page which detail LTE recovery actions.
In essence and without trying to give flying instruction over the internet the recovery actions for LTE can be summarised as
1. Full power pedal (to the stop)
2. Forward cyclic to gain airspeed (if space permits)
3. Lower lever to reduce torque (if height permits)
Obviously speak to your instructor for an in depth look at LTE.
This page may help Helicopter Safety | Loss of Tail Rotor Effectiveness [LTE] there are a couple of documents part way down the page which detail LTE recovery actions.
In essence and without trying to give flying instruction over the internet the recovery actions for LTE can be summarised as
1. Full power pedal (to the stop)
2. Forward cyclic to gain airspeed (if space permits)
3. Lower lever to reduce torque (if height permits)
Obviously speak to your instructor for an in depth look at LTE.
VeeAny
I think the first recommended action for recovery from LTE (full pedal deflection) may have tipped RRPM below the critical stall value in this situation (assuming she hadn't already done just that).
The question is whether this was just LTE (caused, for example, by an unfavourable wind vector), or LTE and low RRPM and an uncommanded sink rate due to running out of power. The aircraft is clearly over-pitched. LTE seems to be a symptom and not the cause of the trouble the aircaft got into. And in itself LTE would not have posed an immediate risk: a spinning aircraft is better than a falling one.
TT
I think the first recommended action for recovery from LTE (full pedal deflection) may have tipped RRPM below the critical stall value in this situation (assuming she hadn't already done just that).
The question is whether this was just LTE (caused, for example, by an unfavourable wind vector), or LTE and low RRPM and an uncommanded sink rate due to running out of power. The aircraft is clearly over-pitched. LTE seems to be a symptom and not the cause of the trouble the aircaft got into. And in itself LTE would not have posed an immediate risk: a spinning aircraft is better than a falling one.
TT
torquetalk - I agree, in the normal situation you might expect the rate of yaw to reduce or stop as you weathercock into wind - however, if you are inadvertantly moving at the same speed as the wind that won't happen and you will keep going round. I think overpitching is the root cause here which drives everything else.
Gents
You may well be correct about the root cause of the video.
My LTE comment is in response to
Not a comment on the VH-WYS case.
GS
You may well be correct about the root cause of the video.
My LTE comment is in response to
Is LTE recovery (by the book) any different from LTR recovery? I.e. (assuming enough altitude) enter auto-rotation (at least, that is what I have been taught, before anyone jumps in and tell me that they presume that from now on I'll do something completely different)?
GS
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Lowering pitch: yes, but rolling off throttle would have depressed the RRPM still further.
Reverse Flight
I think this goes back to which problem is identified as primary. And that has to be low RRPM. The recommended procedure for recovery for the Robinson is rolling on throttle and lowering the collective. LTE wasn't the thing that nearly killed them.
The correlation between collective and throttle you refer to is likely to drive RRPM disproportionately lower than the given movement of the throttle, as it "overreacts" (closing the butterfly valve more than desired) at lower power settings (circa < 20") and this is exactly where you're heading even if you roll off only a little.
You may be right about the margin between horn and complete stall, but manipulating these values in training in is one thing; being behind the curve in an emergency is another. The values clearly reached a critical value on two occassions before recovery.
It will take the aircraft 2-300 feet to establish in autorotation, so the RRPM recovery from entering autorotation during this period is solely from reduction of pitch, especially if descending vertically with the wind as the aircraft appeared to be. Entering auto is not the way to get RRPM back in the first instance because of the lag as the aicraft accelerates.
The correlation is not Robinson-specific btw: The Schweizer also has the same system, as do some models of the Enstrom. It isn't even piston-specific: A similar correlation between pitch and fuel demand is used in Turbine helicopters.
Apologies if this is all a bit pedantic, but it seems to me that the focus on LTE recovery leads the discussion in the wrong direction.
TT
I think this goes back to which problem is identified as primary. And that has to be low RRPM. The recommended procedure for recovery for the Robinson is rolling on throttle and lowering the collective. LTE wasn't the thing that nearly killed them.
The correlation between collective and throttle you refer to is likely to drive RRPM disproportionately lower than the given movement of the throttle, as it "overreacts" (closing the butterfly valve more than desired) at lower power settings (circa < 20") and this is exactly where you're heading even if you roll off only a little.
You may be right about the margin between horn and complete stall, but manipulating these values in training in is one thing; being behind the curve in an emergency is another. The values clearly reached a critical value on two occassions before recovery.
It will take the aircraft 2-300 feet to establish in autorotation, so the RRPM recovery from entering autorotation during this period is solely from reduction of pitch, especially if descending vertically with the wind as the aircraft appeared to be. Entering auto is not the way to get RRPM back in the first instance because of the lag as the aicraft accelerates.
The correlation is not Robinson-specific btw: The Schweizer also has the same system, as do some models of the Enstrom. It isn't even piston-specific: A similar correlation between pitch and fuel demand is used in Turbine helicopters.
Apologies if this is all a bit pedantic, but it seems to me that the focus on LTE recovery leads the discussion in the wrong direction.
TT
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Hi Torquetalk, I'm just glad that you are taking it as seriously and professionally as I am.
If the primary problem is low rrpm, I fully agree with you that rolling on (plus reducing collective, height permitting) is the corrective action. I can vouch for that - I have used this exact technique several times to save low rrpm in an R44 when it was hot, high, humid and heavy. From experience, I cannot trust the governor in an R44 to do its job properly when the job demands it.
If the LTE spin were the primary problem, then you must rid the spin before you fix rrpm, as the spin is very overpowering (it is in control, not you). I have only known two other pilots (apart from myself) who has experienced full-blown LTE and lived to fly another day (they were both instructors at my old FTO) and they couldn't stress enough the importance of rolling off throttle first. I have also practised LTE recoveries with them and you'd be surprised at how effectively the roll-off retards the spin.
Flying with the horn on is not for the faint-hearted in a Robbie. That's why Tim Tucker regularly flies with students at the RHC safety course deliberately at low rrpm with the horn blaring to instill in them that it's not a must-die situation and it is perfectly flyable for prolonged periods in that configuration.
Actually getting back rrpm back in a low-inertia MR is not as difficult as it sounds. It only takes 75-125 feet (Oz syllabus) or 100 feet (FAA syllabus) to establish autorotation with collective full down. Unfortunately because throttle had to be closed to stop the spin, we can't roll it back on until we gain some forward airspeed to keep our tail aft in flight. Once that happens, rolling on will no longer pose an LTE threat.
I apologise if I confused you with the auto. In lowering collective and rolling off you are going to loose some height and that is going to push air up the MR blades as in an auto, giving additional rotational force to the MR. However, while I agree the main method of restoring rrpm is the rolling back on of throttle, that is the last action in the entire sequence. The lady in the video had 2000' above the waters of Port Melbourne but of course the technique would be different at low levels (separate discussion warranted).
I did not say only Robbies have correlated throttles ; I just meant that due to the specific setup in a Robbie, the corrective action is type-specific and should not be used in another make of helicopter without further consulting the POH/maintenance manual.
But I totally agree that if low rrpm is the primary problem, we should not be discussing LTE at all !
If the primary problem is low rrpm, I fully agree with you that rolling on (plus reducing collective, height permitting) is the corrective action. I can vouch for that - I have used this exact technique several times to save low rrpm in an R44 when it was hot, high, humid and heavy. From experience, I cannot trust the governor in an R44 to do its job properly when the job demands it.
If the LTE spin were the primary problem, then you must rid the spin before you fix rrpm, as the spin is very overpowering (it is in control, not you). I have only known two other pilots (apart from myself) who has experienced full-blown LTE and lived to fly another day (they were both instructors at my old FTO) and they couldn't stress enough the importance of rolling off throttle first. I have also practised LTE recoveries with them and you'd be surprised at how effectively the roll-off retards the spin.
Flying with the horn on is not for the faint-hearted in a Robbie. That's why Tim Tucker regularly flies with students at the RHC safety course deliberately at low rrpm with the horn blaring to instill in them that it's not a must-die situation and it is perfectly flyable for prolonged periods in that configuration.
Actually getting back rrpm back in a low-inertia MR is not as difficult as it sounds. It only takes 75-125 feet (Oz syllabus) or 100 feet (FAA syllabus) to establish autorotation with collective full down. Unfortunately because throttle had to be closed to stop the spin, we can't roll it back on until we gain some forward airspeed to keep our tail aft in flight. Once that happens, rolling on will no longer pose an LTE threat.
I apologise if I confused you with the auto. In lowering collective and rolling off you are going to loose some height and that is going to push air up the MR blades as in an auto, giving additional rotational force to the MR. However, while I agree the main method of restoring rrpm is the rolling back on of throttle, that is the last action in the entire sequence. The lady in the video had 2000' above the waters of Port Melbourne but of course the technique would be different at low levels (separate discussion warranted).
I did not say only Robbies have correlated throttles ; I just meant that due to the specific setup in a Robbie, the corrective action is type-specific and should not be used in another make of helicopter without further consulting the POH/maintenance manual.
But I totally agree that if low rrpm is the primary problem, we should not be discussing LTE at all !
Hi Reverse Flight
I think it’s such good and rare footage that Robinson are sure to incorporate it in their safety course. It’s great to show to students and get them to discuss as a group what went wrong and what action should have been taken.
When teaching, I demonstrate loss of tail rotor in the hover/at low air speed, and rolling off certainly kills the spin. And I also try to teach that the horn is a warning rather than a command. Still, if it goes off unexpectedly and you’re somewhere between 97 and 80? %, you have to fall back to drill. You don’t have time to analyse, interpret and react: roll on and lower: Robinson tells us to lead with the throttle during the recovery action.
The values you mention for establishing autorotation are a bit lower than I would have expected: are they perhaps for an R22 which needs to move less air to get the RRPM back?
Regards
TT
I think it’s such good and rare footage that Robinson are sure to incorporate it in their safety course. It’s great to show to students and get them to discuss as a group what went wrong and what action should have been taken.
When teaching, I demonstrate loss of tail rotor in the hover/at low air speed, and rolling off certainly kills the spin. And I also try to teach that the horn is a warning rather than a command. Still, if it goes off unexpectedly and you’re somewhere between 97 and 80? %, you have to fall back to drill. You don’t have time to analyse, interpret and react: roll on and lower: Robinson tells us to lead with the throttle during the recovery action.
The values you mention for establishing autorotation are a bit lower than I would have expected: are they perhaps for an R22 which needs to move less air to get the RRPM back?
Regards
TT
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Hi there again, Torquetalk. The definition of commencement of autorotation in my theory notes is when the MR rpm stops decaying and starts to increase due to the windmilling effect from below. If you're talking about fully-restored rrpm in the auto, then I agree that the height lost must be more than what I quoted.
Are we sure it was a lady pilot? I know the heavy breathing is clearly female but you can hear the distress call being put out in the background by a male voice. Since the audio comes from the camera footage, isn't it more likely that she is the photographer or assistant?
Back to the recovery - accepting the effect of the correlator as a side issue, lowering the lever as a single action will stop the Nr decaying any further and, by reducing the power demand and therefore torque reaction, reduce or stop the spin as well.
Back to the recovery - accepting the effect of the correlator as a side issue, lowering the lever as a single action will stop the Nr decaying any further and, by reducing the power demand and therefore torque reaction, reduce or stop the spin as well.
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During a training session a very good instructor wanted to demonstrate how to recover from a very similar situation.
Up to about 3500 AGL and into a OGE hover. He starts a spin to the right rolls down the throttle, RPM starts rapidly going away and asks me to recover
Fortunately he has me do it with him the first time. Down goes the collective, gentle on the pedals to prevent bouncing off the stops. RPM comes up, spinning slows to a stop, push forward and off you go in less than 500 feet. Next exercise, demonstrate that you can autorotate straight down and do pedal turns. The main point of his instruction is to relax and not to over do control inputs.
Young instructors can clearly get you through. They can even explain things on paper and watch videos of accidents. Older experienced instructors can show you simple things in difficult environments, combine them and then throw in a curve or two so that when these things happen, you as calmly as possible can deal with them. This guy was a master at this and every chance I could get I would have him take me out and make me sweat.
Up to about 3500 AGL and into a OGE hover. He starts a spin to the right rolls down the throttle, RPM starts rapidly going away and asks me to recover
Fortunately he has me do it with him the first time. Down goes the collective, gentle on the pedals to prevent bouncing off the stops. RPM comes up, spinning slows to a stop, push forward and off you go in less than 500 feet. Next exercise, demonstrate that you can autorotate straight down and do pedal turns. The main point of his instruction is to relax and not to over do control inputs.
Young instructors can clearly get you through. They can even explain things on paper and watch videos of accidents. Older experienced instructors can show you simple things in difficult environments, combine them and then throw in a curve or two so that when these things happen, you as calmly as possible can deal with them. This guy was a master at this and every chance I could get I would have him take me out and make me sweat.
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Not having the time to go over all this thread again, but didn't someone in an earlier post state that it was a female pilot and that she hadn't at the time of his post, flown again?
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Originally Posted by IntheTin
Not having the time to go over all this thread again, but didn't someone in an earlier post state that it was a female pilot and that she hadn't at the time of his post, flown again?
The pilot was a female, and following the incident she was given further training and flying. She has since decided to return to FW flying.
The video and soundtrack is from a tape off a stabilised camera, the soundtrack is of the female camera operator. Hers is the heavy breathing, and later the query to the pilot if she is OK.
The left front seat was occupied by a male who hired the helicopter and made the banner, who is also a PPL(H) and was taking photographs of the banner. He gave out a distress call on 123.45, being used for inter-helicopter calls during the filming task.
