Quarry Excursion
 

Interesting little incident:

https://assets.publishing.service.go...PKR__01-20.pdf

‘The pilot reported that he pushed the cyclic forward to increase the rotor speed’. Hopefully there is a mistake in the writing of that sentence rather than what the pilot actually thought/did.

Also, he’s making an approach into a 10 knot headwind ( points at least for not making a downwind approach ) and he doesn't just go around when he realises he's screwed up the approach? With that wind, I don't care how steep or confined the approach was, he could have just gone around. Unfortunately, he has a lot of company... People are amazingly reluctant to go around...

I also love that he's getting both high RPM warnings and low RPM warnings. Most of my Enstrom time is in the "A" model... No RPM warnings at all to distract you! Probably just as well it didn't have any warning systems, the low RPM warning system would have been going off all time ( it was seriously underpowered ).

But the wind was 260/10, so his poor approach would be compounded by being downwind. Don't like his thought processes at all.

Under Discussion heading.

I’m going out on a limb here but I don’t like the way the second and third paragraph are written in that report under the ‘Discussion’ heading. I think they are slightly incorrect in their explanation. Surprising from an AAIB report. Or is it just me reading it wrong? Surely large blade ‘pitch’ angles prevent available engine power from increasing rotor rpm.? Not large blade coning angles?

The third paragraph :- yes reducing collective reduces pitch angle and then the rotor rpm can recover (not engine power recover. surely the available engine power is already trying to recover the Nr but is unable to) Once drag reduces due to decreased pitch angle, then the available engine power can return Nr to within normal operating parameters. Surely not “spin at full speed”?

Looking at google earth, I assume he was approaching the property on Rhiwbina Hill - if so that some overshoot!

Helmut,

I'm having a little problem understanding your point about engine power, but for those that haven't flown pistons in a while I'll remind you that unlike turbine helicopters, in a piston helicopter available engine horsepower is directly related to RPM. If you have let your Nr decay by 10%, you have lost 10% of your available horsepower. It's a double whammy, that at the very time the rotor system is demanding more power, you have less available from the engine.

So, the original statement is correct: if you find yourself in a low RPM situation in a piston helicopter, you are also in a low horsepower situation. Lowering collective will recover both Nr and available horsepower ( let's ignore any talk of derated piston for now ).

Apologies if I just didn't understand what you were getting at.

BTW, the high inertia Enstrom rotor system makes things much worse here. For all of our complaints of the low inertia R22 rotor, recovery from low rotor RPM is quick and easy in that aircraft. The Enstrom, while a magnificent machine for autorotation, can be very time consuming to recover rotor RPM, and it's not that difficult to get yourself into the corner of the envelope where you are going to hit the ground before you can get flying RPM back... As in, if you lower the collective you will descend and hit the ground before the engine can get that heavy rotor system back up to speed, and if you don't lower collective it will stop flying and hit the ground. Nothing unique to the Enstrom, but especially in the "A" model Enstrom an interesting combination of low horsepower and high inertia.

Not a lot of room for any overshoot, ​​​if I've managed to find the right place.

https://cimg1.ibsrv.net/gimg/pprune....341e813237.jpg

he was heading from the East into a 260 wind
https://cimg3.ibsrv.net/gimg/pprune....29f813a15.jpeg

No mention,discussion about prior weight v performance check for OGE hover to go into, then out of the pad ; no mention of recce,check for wind,or previous talk to anyone at the site; had he been there before or doing it `on the fly`...?
Would have been better approaching from North,so you don`t end up going down a hillside....
Seems people are not `attuned` to be totally aware of RRPM ,and act accordingly without waiting for `high/low` warnings,as it`s usually too little too late then....

I'm not seeing any relevant fences in the quarry you've pictured, which is to the south and slightly west of the quarry I've pictured.

Does anyone know exactly where this occurred?

Enstrom power curve(or lack of it!)
 

As pointed out by Paul, once you overpitch the 280FX, you suffer a greater power loss than you think, plus the lack inertia in the rotor system it's not just the blades.
The whole thing started far earlier as pointed out and making another approach from a different direction could have all the difference.
From experience a slow orbit over the site to suss out the wind direction would of helped, at least he is safe and here to tell the tale.
Lets hope others benefit from his mistake, fly safe.:ok:

aa7778888, if you look at the tip of the `arrow`,theres a JCB and a fence behind it,as in the AAIB photo....

Having had another wider look at the area, I see to the west there's a huge great quarry the other side of the village/town! https://goo.gl/maps/vPf3ezJDAVhcMrMp7 The one I found was my first search.......

Minor point of pedantry - shouldn't the title be "Quarry INCURSION"?

Well yes, of course there is. If you had bothered to read the post above it you would note that the photo with the big arrow and fence was posted by me. I.e. that's probably the place. But then 212man posted another photo of a different nearby quarry and mentioned the easterly approach direction in response to my post, seemingly questioning it.

Going back to my photo, the pilot's story seems unlikely. If he "overshot" into the quarry at the location I identified it would seem much more likely he was traveling in the direction of the arrow.

And since then I think I identified the more likely location

Nope, I chose the title deliberately. A little playful humour based upon no-one being hurt (physically at least - pride maybe dented!).

OK, I'll bite: where? What coord's?

On a point of pedantry .....
As the accident occurred upon exiting the quarry then 'excursion' is absolutely correct.

I'll get my coat...

https://cimg2.ibsrv.net/gimg/pprune....992f1a15c.jpeg
Couple of miles west. Looks like fence on western edge.