In article , Tony sayer wrote:
Pardon me sounding curious and perhaps not that knowledgeable re rotary
wing,

Well, I'm not a pilot either, I'm just going on what the pilots
were saying as they queued with us for the ****ter beside the helideck
afterwards.
I guess that the engines weren't at full throttle (either of them)
and when one was lost while decelerating towards a hover, they couldn't
throttle up the remaining one fast enough to replace the lost lift. Of
course, you can always trade the rotational energy in the rotor for some
lift by increasing the angle of attack of the rotors (I recall "dropping
the collective" being a phrase used) but that only works so far before
you reduce the rotor speed to it's stall speed. Then again, since the tip
has a higher air speed on one side of the flight vector, then you'll
stall and lose lift on one side, rolling you.
Complex things, paraffin budgies. I was trying to organise a blast
on one of Bristows *real* simulators for a friend's stag night earlier
this year. The phrase "not a hope in hell, sorry mate" sprang easily to
the Bristows mannie's lips.

why do they
have twins if you can't do that then or is it the one engine can make
the descent tolerable but isn't that what auto rotation is for?

Autogyring isn't to make the descent tolerable, it's to make the
crash into a "good landing" (on the 'can you walk away?' criterion). Of
course, we don't get the option of walking (mostly, see later), but given
the choice between getting the doors open and the liferafts properly
deployed as opposed to doing the full
punch-the-windows-out-while-hanging-upside-down-in-your-harness-with-5-ce
ntigrade-salt-water-running-up-your-nostrils-and-every-nerve-screaming-th
is-time-you're-really-going-to-die-you-stupid-****er-why-don't-you-get-a-
proper-job-like-you've-promised-to-for-years palaver ... well, I'd really
like to slow down the landing enough that we've a chance to swim away.
BTW, I believe that there's at least one airframe that's been
fished out of the North Sea, stripped down and returned to flight. Makes
me look at the tin-worm on my mate's cars and wonder ...

Concerning the option of walking home : snoozing away on a flight
out ; go over the coastline at sunrise ; Zzzzz ; something in the cabin
noises changes ; everyone is awake from their hung-over slumbers thinking
"Uh Oh" ; watch the sun patches start to move from the left wall of the
cabin, round the front, and stabilize on the right wall ; so ... we've
just done a 180degree turn ; then we descend into the cloud ; everyone is
tightening up their belts and pulling on the neoprene diving hoods ;
descended to cruise at about 200ft and heading back the way we came ; we
get to the shore line, along those long beaches from Newmachar down to
BoD ... and the pilots cruise back in parallelling the surf line about
100m out from the beach, so we'd just about had the choice of walking
back. Only THEN do the pilots remember to tell us that there was a
problem, like we hadn't guessed already. Made less than half-speed coming
back in ; had a 3-hour wait until another bird came available to fly us
out. Then straight onto a shift-change schedule to go onto nights.
Lovely.

--
Aidan
Aberdeen, Scotland
Written at Mon, 03 Sep 2007 22:56 +0100, but posted later.