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Helicopter crashes at Lumberton airport

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Helicopter crashes at Lumberton airport

Old 15th Sep 2017, 07:47
  #21 (permalink)  
 
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Nigel

Will have to disagree here. I have had one engine stop while doing an EOL for a PC in a 300 as it happens ( customers aircraft ). Throttle was rolled back into detent and engine stopped. I can assure you that the ac descended considerably quicker than a normal auto followed by EOL. Having done thousands of EOL's to the ground I speak with total assurance. Quite why, that is is interesting, as you say there is a freewheel disconnect !
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Old 15th Sep 2017, 08:42
  #22 (permalink)  
 
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But there will be drag through that freewheel and it is much less with the engine running that with it completely stopped - it might say freewheel on the box but it is not frictionless.

It also depends on where in the transmission chain the freewheel is.
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Old 15th Sep 2017, 08:57
  #23 (permalink)  
 
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Good point . I have done both and don't think the difference is that much ...but there will be a little less friction maybe if engine is still in idle I agree . It doesn't change the point about EOL and Autos .
Out of interest what would happen if you slowly pulled the fuel shut off ?
Could it reduce fuel flow so you could keep engine on during auto and maybe gain some benefit .... or does it just stop the fuel instantly?
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Old 15th Sep 2017, 09:02
  #24 (permalink)  
 
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Originally Posted by Hughes500 View Post
I can assure you that the ac descended considerably quicker than a normal auto followed by EOL.
The 300 drops like a rock in any case, so are you sure it is actually possible?
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Old 15th Sep 2017, 09:31
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Nihelh - there you go again egg on face in public talking rubbish, transmitting and then thinking about it afterwards.

You'll never learn will you (well not in all the years you persistently continue to make these silly naiive remarks on a public forum).
Each to their own I guess.

Now back to fact:
As Hughes 500 quite rightly said (you know - the guy who flies the same a/c as yours?).
If you committ to an EOL at the top of the slope, you physically switch the engine off. In an Auto - you don't.
The next few seconds dictate your initial descent speed because one rotor wants to stop as fast as possible on you (EOL) and the other doesn't because of the residual engine drive thru the box (Auto). For heavy helos this RoD is markedly different.
Now this concept might be a little difficult for you to grip: The safe operating range of the rotor during an EOL descent is narrower than that of the Auto because you have the engine acting as a goalkeeper if you droop the Nr too low (some a/c monitor the Nr at this low range and arrest it automatically), so an ab initio or someone who has not rehearsed EOL's much lately, will 'tend' to rely on this safety net whilst manouvering with Nr (for a PFL for instance). With an EOL, the a/c will sink faster - because you haven't got that permanent safety net propping up the low end of your Nr band.
[In an EOL, if you DO go too low in the Nr department - you have no choice but to flare the a/c a little to recover it, but this option is of course limited for obvious reasons).
At the bottom of course, Nr is your best friend and in an EOL situation - your only friend!
Unlike an auto recovery - where you have lots of friends sitting in the engine compartment waiting to come to the rescue if you cock up.

So, sadly Nigel - you're quite wrong and Hughes500 and many other technically aware pilots are too.

As I am - after approximately 2500+ EOL's (and god only knows how many auto's)to date with only one minor incident where I cracked the bottom of the fenestron during a rather enthusiastic flare prior to the level.

And then you further dig a big hole by asking everyone what will happen if you pull the fuel shut off back slowly?
Are you sure now, that you have done several EOL's and auto's because if that was the case, you would be perfectly aware what would happen because you would have either been shown it or tried it yourself (knowing you).
Never mind - I'll just have to explain this to you, also:
Odds are - the fuel shut off is electric upon which once the lever leaves the ON detent, the motor will activate and close the HP valve ASAP probably even before you complete the motion all the way back to OFF.
If the valve is 'steam driven' then the engine will gradually be deprived of fuel and the Nr will decay quickly or slowly dependent on your collective lever position.
Sadly in the case of this tragic accident, it 'appears' the the fuel management system had asked for full fuel supply (I don't know the engine set up in this helo).
Maybe - just maybe, the pilot/ATC/FI agreed the best option was to shut the engine down using the HP valve and adopt an EOL profile.
It was during this phase, something got out of hand and the helo was seen to rapidly increase its RoD and plummet vertically to the ground.

My take (for what it's worth): He dipped below the minimum Nr band and couldn't recover it.

RiP.

Next Gaff please Nigel?

Last edited by Thomas coupling; 15th Sep 2017 at 09:47.
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Old 15th Sep 2017, 10:04
  #26 (permalink)  
 
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I agree with the friction part but wasn't expecting an increased ROD of about 300 ft a min or 15% mind you only done 2 in anger of about 5000 so mind wasn't really on the rpm's !
Nubian, they don't drop like a brick in a normal auto with engine running but at idle they come down at 1800ft per min hardly like a brick, if you want some real excitement ask Crab to do one in a Scout, that will be more like 3000 ft a minute
Pulling the fuel shut off valve would just shut it off instantaneously as you are pulling a lever. could try the mixture but initially the rpm would go up as you wind it out then would slowly starve the engine of fuel.
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Old 15th Sep 2017, 10:32
  #27 (permalink)  
 
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TC . You are full of it old boy and getting confused in your old age !!
1) EOL does not refer to ,if or if not , the auto is done with or without the engine . It is specifically the LANDING . You can do an auto with engine then elect to shut down to do your EOL . This is the preference of most of my instructors over the years .. ( secret is in the word LANDING ) .
2). It appears even you are not sure what type of fuel shut off is used either ? But you do acknowledge that it could reduce fuel flow and then Nr . So my question was would it be possible , with the old valve , to reduce flow to stop over speed .
Your rampant ego and aggressive nature may frighten some people off from asking questions , which is not helpful !! This is not your show and it shouldn't be used as the TC soap box telling us what a God you ( used ) to be ...... !!!
Ps ... it was rather pleasant and good humoured while you were away . Your not going on holiday again soon by any chance ??!!
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Old 15th Sep 2017, 11:14
  #28 (permalink)  
 
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TC said 'Odds are - the fuel shut off is electric upon which once the lever leaves the ON detent, the motor will activate and close the HP valve ASAP'. I have to question whether TC has ever seen a HU269? It's one of the most rudimentary helicopters out there, and it certainly doesn't have an electric fuel cock! It's a simple cable operated device (tap/faucet) via the instrument panel and yes, there could be varying degrees of off or on. So fuel flow could be adjusted by careful adjustment of the fuel shut off control. However, I suspect that being a piston engine, it would quickly mess up the mixture and stop the engine anyway. If it was a turbine, like the HU369, then, in theory at least, the rpm could be controlled with the fuel shut off valve. Not such a stupid question after all Nige.
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Old 15th Sep 2017, 11:42
  #29 (permalink)  
 
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I had a partially blocked fuel filter on my H369 and the fuel flow was restricted, only allowing 50% torque, just enough to sustain straight and level at 40 kts. So I should imagine careful manipulation of the manual shut off fuel valve might work in an emergency situation...
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Old 15th Sep 2017, 12:41
  #30 (permalink)  
 
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Phew...!! Maybe not so much egg on my face after all . I am not sure I would want try this without testing the theory on the ground pulling some pitch and see if a gentle pull back would reduce torque. Well , at least I now have some support from two pilots ....... and vitriol from one old ex pilot !!!!
Happy with that 😎👍

Ps . Before another attack ... I am not advocating this approach to stuck ( high) throttle . Just wondering if it may work in some cases where the shut off is a manual valve ?
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Old 15th Sep 2017, 15:02
  #31 (permalink)  
 
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Originally Posted by Hughes500 View Post
Nigel

Will have to disagree here. I have had one engine stop while doing an EOL for a PC in a 300 as it happens ( customers aircraft ). Throttle was rolled back into detent and engine stopped. I can assure you that the ac descended considerably quicker than a normal auto followed by EOL. Having done thousands of EOL's to the ground I speak with total assurance. Quite why, that is is interesting, as you say there is a freewheel disconnect !
I need some clarification here.

An "auto" is what? Engine running at healtly rpms followed by pitch down?
W/o reducing throttle to "high idle" it will be hard to demonstrate power off green arc control by pitching, as slightly raising the pitch (in a 300) will remove the needle split due to the throttle correlator.

An "EOL" is an Engne Off Landing. Off as in 0 rpms? If yes, I think almost nobody has down that deliberately.
Is an EOL what I described as "auto" above? Being aerodynamically in auto rotation with noticeable needle split due to engine idling?

I only know EOLs in 300s with needle split, where nothing is guarding my low rrpm marging, except my FI yelling at me.

I would not expect any difference in mechanical(!) drag (or ROD) between demonstrating an EOL with needle split (possibly with recovery at 20ft) and doing a "true EOL" where the engine actually has stopped turning.
Is that view wrong, if yes, pls elaborate why.

Last edited by Reely340; 15th Sep 2017 at 16:49.
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Old 15th Sep 2017, 15:33
  #32 (permalink)  
 
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I see your point . Where I think TC is wrong is that EOL is engine off landing . If you do an auto , it is an auto regardless of the engine state . You can just dump the lever with full engine and it is still in autorotation in my view ( aerodynamic ) .
I also agree that v few people demonstrate actual engine off landings partly I expect due to cooling off period but mainly I guess as it would be an added risk for v little gain !!
No doubt God will tell us otherwise.... a bit like USA v UK with settling / LTE etc etc I think we have got used to calling engine in idle an EOL .
Is it worth arguing about ?!! I rather foolishly tried to tell God that EOL is not relevant to the autorotation on the way down , where you have the option to keep the engine if you wish ( if it is still producing some power ) . An auto is an auto regardless!! End of !
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Old 15th Sep 2017, 15:37
  #33 (permalink)  
 
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Reply

I have done thousands of EOL's to the ground with the engine at idle and with the throttle wound hard in against the stop if you don't as you pull full pitch the corrector gets the engine back to about 2000 rpm form 1500 ! I was saying I have had 2 engine failures in my 8000 hours of flying. First time it was while doing a PC with a customer, he wound the throttle off as we went into auto. I wound the throttle in hard against the stop and the engine stopped, height about 700 ft ( Before anyone asks I did this check on the ground and it didn't stop the engine ! ) I was surprised at the rate of descent, normally around 1600 to 1800 rpm depending on where the auto revs are set. We were comfortably over 2000 ft a minute
Although the engine in a normal auto is running there is an element of friction that keeps things turning. I was surprised in a genuine power off landing what a difference there was as I said about 200 to 300 ft a minute .
Hope that answers your questions
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Old 15th Sep 2017, 17:19
  #34 (permalink)  
 
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Hallo all,

My question would be - if you have an engine with the throttle stuck full open, can you even enter an "autorotation" without shutting off the motor or would the engine with screaming rpm keep driving the gearbox regardless the freewheel and your pitch down?
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Old 15th Sep 2017, 18:06
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Evil

Depends where the throttle is stuck, what I mean is which side of the correlator linkages. As you may know the correlater on a 300 will try and open / close the throttle in relation to where the collective is. So if stuck at the hand grip then the correlator will look after rpm. More likely for the linkages to go at the injector itself.
I would suggest that if the throttle is stuck at full open as opposed to the setting for whatever pitch the blades / Map you are flying at then you have a major problem. The throttle is going to want to accelerate the rotor system, it maybe that lowering the lever may activate the correlator to close the throttle, if not then the rrpm is going to go off the roof as you decrease MR drag.
To contain NR you would have to lift the lever, bear in mind you can't enter autorotation as the engine speed is higher than the rrpm so freewheel won't come into play. Your only real option is to pull the mixture which is easier to do then the fuel shut off valve. By gradually pulling the mixture the fuel will go lean increasing engine rpm until the lack of fuel starves the engine. Now can you restrict the fuel flow to slow the engine, I doubt it as if you follow the last check of the day on shutdown in a 300, as you pull the mixture at about an inch out the mixture goes lean, hence the 25 to 100 rpm rise, pull out another fraction and the engine will die ! I would imagine pulling the fuel shut off valve will have the same effect.
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Old 15th Sep 2017, 18:25
  #36 (permalink)  
 
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Hughes ...why not ask TC . He will know the answer as he is our resident 300 expert !!
Presumably you didnt realize that it has an electronic fuel cut off as well did you ?!!
As you still actually fly helicopters and fly the 300 ( so did i instructing but that was 1000 years ago ) it is interesting to hear your take on the possibility of reducing the engine rpm by either careful use of cut off or mixture . I can only guess that if it can be done someone will have done it !!
ps TC is also wrong about us flying the same machine unless you also run an old Agusta Mk2 !!!
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Old 15th Sep 2017, 20:10
  #37 (permalink)  
 
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Has anyone considered the possibility of a freewheeling unit malfunction.
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Old 15th Sep 2017, 22:24
  #38 (permalink)  
 
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Two major failures within minutes would be unlikely. If so , what terrible luck . Hopefully we shall find out soon . The 300 is a great little machine with a good safety record as far as I am aware . V sad .
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Old 16th Sep 2017, 03:39
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Originally Posted by Hughes500 View Post
Reply

I have done thousands of EOL's to the ground with the engine at idle and with the throttle wound hard in against the stop if you don't as you pull full pitch the corrector gets the engine back to about 2000 rpm form 1500 ! I was saying I have had 2 engine failures in my 8000 hours of flying. First time it was while doing a PC with a customer, he wound the throttle off as we went into auto. I wound the throttle in hard against the stop and the engine stopped, height about 700 ft ( Before anyone asks I did this check on the ground and it didn't stop the engine ! ) I was surprised at the rate of descent, normally around 1600 to 1800 rpm depending on where the auto revs are set. We were comfortably over 2000 ft a minute
Although the engine in a normal auto is running there is an element of friction that keeps things turning. I was surprised in a genuine power off landing what a difference there was as I said about 200 to 300 ft a minute .
Hope that answers your questions
I've had the engine stop at the bottom of a practice auto. I can't remember the exact reason why, but it had to do with keeping some RPM on the way down after the needles split. I went to roll on throttle at the level off and there was nothing there. Just continued to the ground.

Is Dennis Kenyon on this forum?
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Old 16th Sep 2017, 06:00
  #40 (permalink)  
 
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Hmm, I am now too ancient to fly anymore, but I just wonder how some people with correlators, electric fuel shutoff valves, hydraulic controls etc.,
would have managed with older piston machines that had none of them!

Cannot remember which way the H300 engine is mounted, but I do remember that my old Hiller was vertical. As an engineer I cannot agree about "friction" being the cause of a difference in ROD. But there will certainly be some differences in forces because of the gyro effect of an engine between running or stopped. May not be the cause, but it should be considered.
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