First I'll deal with Airpolice / FortyOdd: I apologise, my comments related to "practicing".
I was not inferring "no-one has ever experienced a double engine failure ever, anywhere"?? The guys you talk of - experienced the real McCoy FFS. I am talking FOR PRACTICE - ready for the real McCoy. I thought you understood that?

Now onto someone with special needs:

Silsoe - what is it with you? Are you being purposefully obstinate, or what.
So for the benefit of SilSoe Sodding Sid, I will shout:

ALL YOUR SODDING EXAMPLES ARE EITHER SIMULATORS OR AUTO ROTATIONS. I MADE IT ABUNDANTLY CLEAR IN MY FIRST POST AND THEN RE-ITERATED IT IN MY SECOND POST THAT SIMULATORS AND AUTO ROTATIONS ARE NOT ENGINE OFF'S.
DO YOU UNDERSTAND THE DIFFERENCE BETWEEN SIMULATED EOL'S / AUTOROTATIONS TO THE DECK and ENGINES OFFLANDINGS?
If not - I suggest you go back to Argos where you got your PPL from and ask for your money back. :ugh::ugh::ugh::mad::mad:

Sorry TC, but as you told us, your words were quite specific and specially chosen.

"No-ONE - not the military , nor civvies teach double engine failure practice and this has been the case for ages."

Those words are just as specific as the words 'Double Engine Failure - Autorotation' as seen in the EC135 Type Rating video at 2:36, a point in the video when double engine failure is being practised. Maybe the words 'Simulator Double Engine Failure' aren't clear enough in the HeliFlight video. Maybe the autorotation of the BO105 wasn't clear enough to be recognised as Double Engine Failure Practise :ugh:

Is that all of the sodding examples ... apart from the S-92 and Viper videos? :rolleyes:;)

This one not count either?

TC, as you seem to agree with G0uli about there being no autorotation, I would put it to you both that given the final circumstances described in my post yesterday at 10:09, that an autorotative landing attempt cannot be ruled out, in fact the indications would suggest that there was indeed some form of 'controlled' flight, right until the end.

Here are my observations on his earlier post, the one where you think he's onto something;

There is no video.
How can a radar plot possibly tell if an ac was in autorotation or not?
Eye witnesses heard engine popping and the ac cartwheeling & spinning, how can it be then, as the transmission had stopped, that there is no damage to the blades and transmission system and the ac was in one piece?


Correct, so the ac was 'flyable'

Only if the instrumentation was displaying correctly and you assume that every warning, caution etc was ignored by everyone on board. (This of course does not get around the pilot/crew appreciation of the amount of time in the air with the take off fuel load)

Agreed, very strange given the length of time 'on tasking.'

Apart from every six month on OPC's, both previously and now.

Possibly, but given the experience level of the pilot, an autorotative profile wouldn't have been strange, however the location wouldn't be the most ideal for a favourable outcome either way.

I would suggest that if the transmission 'stalled' many hundreds of feet above the ground, there would have be a far greater mess than there was and there certainly would have been a lot more damage to the aircraft.


Because of that last paragraph, I would suggest that the ac was indeed under some form of control, right up to the point at which it was a few feet above the roof with the transmission stopped.

Simply out of interest, I for one would like to see a 135 tied down, pulling pitch and the engines chopped, seeing how the blades react to an ever increasing collective input, including through the collective pitch override stop, and to see how that transmission ends up stopping.



My only special need TC, is to understand :(

I have no dog in this unedifying fight between SS and TC, but the issue of overpitching and running out of Nr before the skids are on the ground happened to me. I pulled the collective so hard trying to arrest the RoD that I snapped it a couple of inches up from the pivot point.

Hard landing, ripped the roof off, but we survived. Had it been at night, trying to judge the height above the unknown landing area, then an early pull could have well ended in a similar fashion to this accident.

That's not specific to twins, that's the scenario for any helicopter pilot with a complete engine failure if they are not awake. I say that having had three engine failures in a 206/L with no damage to any machine, one at night.

You don't necessarily have to be into wind either and neither do you need lots of height. You can do a lovely vertical in a 206 from 400 feet (top of the H/V curve).

Phil

I haven't got time to read your diatribe SSS.
Paco - don't be a di*k. Doing EOL's from 400 feet pre warned during the day is NOTHING compared to what David experienced that evening.

I simply see the accident this way:

Two phases: Captions/fuel management phase moments before the final descent onto the roof...is one. I will leave this scenario and decision making process that went thru David's mind to the AAIB, David and his maker.

Second phase:

Radar last saw the cab @ 400'. Assuming the pilot was making for his base in a gradual descent on long finals, the captions must have either been on then or were coming on. This distracted him while continuing the descent. Shall we say passing thru 350 feet?
One engine flames out, check down very slightly on the lever - passing 300 feet. Will he continue with his final approach or turn into wind? Passing 275 feet...............second engine fails, passing 250 feet. Into wind??
Flare hard, check down on the collective....does he turn into wind...perhaps no time. Speed is now way back. Passing thru 175 feet, can't see the ground due to minimal visual clues. Speed now zero or minimal fwd speed. Anticipate the surface...passing 100 feet. Raise collective to cushion touchdown....no Nr....passing 75 feet.....................................................

Paco;

TC;
Well, I think that sums up the cut of TC's jib :=

TC, your second phase may be flawed.

According to the S2/2014 Special Report;

"The helicopter’s altitude as it approached the area of the accident was approximately 1,000 ft amsl and its average groundspeed was approximately 105 kt. The last radar return reported an altitude of approximately 400 ft amsl, when corrected for ambient air-pressure."

The crash site is 2.5 miles away from base, so for you to assume that they were at 400' descending with 3 miles to run when suddenly both engines stopped, is a little too much for me to accept. At that range, I would have thought the recorded height of 1000' more realistic and that last radar ping giving 400' was on the final fateful descent.

What you are saying is that the AC was flying over the city less than 200' above the buildings, with over three miles to run.
I don't believe that to be the case at all!

And now that autorotative action that you continue to scoff at seems more likely, doesn't it?

Guys, this point scoring is not helping anyone.

Can't you just accept that you have both been wrong in some of your statements?

We might never know what happened that night.

.... and please don't shout .... I hope that wasn't a new technique taught at CFS when TC went through. I do pity his poor RN students though.

In the main, flight students are not discussing this accident, seasoned pilots are. That may be the root of TC's frustration with elements of the discussion.

SS points out that "we are not quite sure" problem with the altitude at initiation of the event. Sid expressed my interest in this tragic accident perfectly, which is: I want to understand.

The point I agree with TC on (strongly) is the surprise and reaction time problem between a real loss of both engines, unexpected, and the practice exercises one does to prepare for "the real thing." I too have, a few decades ago, run crews through sim sessions and occasionally toss in an unscripted power loss or malfunction. It really shows the crews where they are "on" and where they are vulnerable. Valuable training, and a use of the sim that can't really be done in the aircraft.

The case of the forced landing cited above, in the snow, reads like the desired "gradual degradation" mode. The pilot saw that things were beginning to go wrong, and thus he was already mentally taking care of what to do if they kept going wrong. When they did, he was on top of it. :ok:

The big unknown for this accident is "how rapidly did things go wrong in sequence" and thus place the pilot (David) in a game of "catch up to the aircraft" over an urban area at night with precious seconds ticking away.

You get even less warning with your head out of the door ;) My second one was at around 200 feet, just hopping over the runway at Manchester. Compressor blade decided to give up.

The thing is with these beasts, you must be continually running through a checklist in your head ALL THE TIME and be VIGILANT (sorry for shouting, but I just want to make the point clear). That's why the Canada Labour Code equates longlining with hard labour.

Phil

A key point to note, I think, when comparing experience of real engine-off landings is the design of modern rotor systems. I was at a briefing by a couple of test pilots earlier this year, who were describing some of the flight testing they do in order to produce the rotorcraft flight manuals etc. All engine failure scenarios apparently assume a pilot reaction time of 1 sec. If you don't react within 1 sec, then all bets are off! With modern rotor systems, some of them can decay in Nr extremely rapidly (compared perhaps to B206 and similar). That is one reason why you will only ever practise double engine failures in a simulator. In the simulator, I often see Nr decaying below 80% with a non pre-briefed double engine failure, on an aircraft which has a minimum power-off Nr of 90%. The test pilots tell me that if the Nr goes below 80%, you are probably toast, as it will be irrecoverable!

When you refer to 'modern rotor systems', do you know what the key characteristics are that cause this behaviour?

Is this about the profiles that enable transmission of more power to the air under the aircraft that correspondingly produce more drag?

Hi all,
it really can be a problem, if you never experienced the differences between power recoverys and real engine offs.
We´ve trained with both engines in ground idle on Bo105 and BK117.
But it is still different, when an engine quits, giving you a lot of captions and sound
Seen the damages, which engines can have (i.e. a loose generator) you really should prepare for loosing the second engine within seconds - but if prepared, the 1 sec reaction time shouldn´t be really a problem.
I´m lucky, that I can spend some hours every year in a simulator (Helisim) and that there we´re not only practice the normal failures, we also do that in the working enviroment, i.e. low level, heavy, confined area and so on.
Seening the differences in chances of survival between flying "Jackie-Boy" or doing it along the manuals has effect in real life.
Still - double engine failure at night over a city is nothing I want to experiance.

Sid

I think that is a 205, single engine?

Actually its a 210 terminus; and you are correct, it's single engine (and it would count as a full EOL) ;)
http://www.pprune.org/rotorheads/192516-bell-210-a.html

Jim,
I'm not 100% sure - I was trying to research it on the net without much success. I am guessing its the combination of rotor profile and inertia which gives the characteristics of that transition from powered flight to autorotative state. I have certainly seen on all the more modern helicopters which I have flown that the Nr is much more sensitive in autorotation (engines on) than ii was in older cabs like the Gazelle or Sea King. It can be very difficult to keep the Nr from rising out of limits if you enter autorotation too abruptly. I would imagine it is the same characteristic which means the Nr will drop rapidly following a power failure if you do not reduce collective pitch or flare quickly enough.

My suggestion would be the increased disc loading in modern helicopters.

More powerful engines allow designers to have smaller diameter rotors that just have to work harder to shift enough air downwards - rotor rpms are higher than older helos and so Nr will tend to decay quicker due to the extra drag.

Add in cambered aerofoil sections - high lift usually incurs drag penalties - and the very responsive nature of semi-rigid rotor systems and you have a reasonable recipe for lively Nr characteristics.

Well if you compare say the R22 (relatively new design) with an older design, say a B47, you will see the newer design puts "engine on" performance above engine off performance.
A narrower, smaller,lighter blade is generally easier to turn under power and hence maximise performance. (Especially if you have a small engine).
Generally customers will want better performance figures when the machine is working normally, over good auto rotational performance when the machine goes wrong.
With two engines especially (where the machine is supposed to go wrong less often), carrying around all that extra fuel and the spare engine, a light inertia rotor system leads to better sales / performance figures.
Compare a B212 rotor with an EC135 and you will see what I mean.