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Old 15th Sep 2017, 09:31
  #25 (permalink)  
Thomas coupling
Join Date: Aug 2000
Location: UK
Posts: 3,682
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.


Next Gaff please Nigel?

Last edited by Thomas coupling; 15th Sep 2017 at 09:47.
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