Oh dear chopjock - that is really amusing even for you.

What exactly is a CAT A procedure for a single?

A twin with a failure on the back-up and with the second engine running struggles to get back to the pad. How on earth could a single do it with negative airspeed.

If you are taking off over a built-up area in a single, that's where you are going if the engine fails.

Jim

Obviously, but if you fly a Cat A departure profile in a single,assuming no engine failure and you don't back out beyond the perimeter, you will be departing the pad area with translational lift, much better than leaving the pad at below translational speed with a towering take off.

That's the rationale behind why I would do it anyway.

Is it any more dangerous to fly out this way?

I have no knowledge of the operating site or its obstacle environment but, if the NZ CAA requires it to be flown in PC1, we might make the assumption that it is contained within a congested hostile environment.

Flying out of any operating site in a congested hostile environment (in a single) puts the helicopter into the exposure area - there is no way to sweeten the pill.

A helicopter certificated in Category A may or may not have a helipad procedure; if it has, it could be vertical, back-up or sideways but it will be exclusively provided by that manufacturer for that helicopter along with the profile, obstacle clearance criteria and mass limitations - all of which have to meet the requirements specified in the certification or operational rules.

If there is any wind at all; flying backwards in a single would be the equivalent of a transition downwind (and backwards), followed by a further transition from downwind, through a zero-wind condition and eventually into wind - all undertaken inside the HV curve.

This would require more power than a normal transition or a towering take-off and might take the helicopter outside of its control envelope. On a risk assessment basis, there appear to be few gains but it does introduce number of unquantified (by the manufacturer) hazards - including an extended period within the HV curve.

Jim

JimL:
I recently had my helicopter education improved by an old-timer - the subject was departures from confined areas. Liked what he said so much that I wrote it up for Vertical magazine.
Basically, it involved backing up from the front of a confined area in order to keep the barrier in sight, and allow a known flight path back to the ground in the event of an engine failure (or lack power available).
Same logic might be used here - backing up will put you in the HV curve, but with a known landing spot in sight that's ahead of you. And evidently there is very little cyclic movement needed to get back to the spot - just lowering the collective will also move you forward towards the spot.
Interesting technique!

Not quite a single engine failure, but I know of a a freewheel unit failure in a popular twin type some years ago, which killed three.

Comments on the following Video, single engine doing joy rides ( flight every 5min over 4hr period), within a built-up area.

Not entirely uncommon in high wind conditions when translational lift can sometimes be achieved in the hover and when wishing to build height in order to transit terrain inhospitable to autos.

Its really about power. If its there, that's a good sign (ie: a/c not operating at MUAW) and the procedure would be to clear the h/v curve asap!

Earl

SEH
 

As a stiff-arsed Brit ... can I put in my two pennorth! When teaching the UK's CAA Ex 26, I teach as SOP the twin engine rearward lift technique, keeping the ELG nicely below til sufficient height is available to secure translational lift before climbing away ... so at least some manoeuvreability and choice of ELG becomes available in the event of an engine malfunction. I also never forget that when flying two engines, the chances of an engine malfunction are doubled!! Multi engines are fine and absolutely necessary for utility ops but we shouldn't forget that the power plant is just one component that keeps us airborne. We also really need two M/R hubs, two MRGBs, ditto T/R transmission & blades and swashplates ... but not likely to happen. PS. I'm still waiting for my first EOL after 1 year & 7 months in the air!

Festive good wishes to all Pruners. Dennis Kenyon.

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I sometimes wonder just how many incidents have ocurred where a twin has suffered the failure of one of its engines and subsequently gone on to perform a safe landing.

Twins certainly seem like the sensible/responsible thing to do and are now well established in the commercial domain but, like Dennis, I also wonder about ..

Thinking of North Sea incidents I seem to recall remarkably few directly attributed to powerplant failure whereas there were numerous involving 'other' component failures!

Sav

er - the point is they do have engine failures sometimes but the consequences are rarely terminal. The consequences need to be bad to justify 2 engines. Another piece of evidence in favor of singles.

"No one was hurt."

... unlike the other single engine related crash that has happened this month, recently posted about on rotor heads, where significant injuries were sustained and where everyone on board was injured to some degree! :ugh:

Shall we now pull out all the crashes with the S-92´s, the 332´s, the AW139´s and all the other multi-engine aircraft that went down in the past 2 years, killing everybody on board?

An aircraft is as good as the engineer that maintains it, and as good as the pilot that operates it in its limits-no matter how many engines it has...

I was only looking for a bite, wow! That worked.
In reply to AnFi, yep, no one injured this time. A twin would of course have just flown home.
To Hueyracer, were all those caused by single engine failure?
Thought not.

Exactly-that´s the point…

It's a helicopter, when they go wrong it can be exciting. However you should give yourself every chance you can.
In 7000 hours, I have had one crash and two engine failures, all in Pumas. The crash was mechanical drive shaft failure (not engine) into the jungle. The engine failures were both in truely appaling weather, one was in 65kt surface wind 20 miles out over the northern English Channel and one over NI with a 300' cloudbase and 45kt wind. That would have been splash and crash in a single. Nobody will EVER convince me that a single is just as safe....... EVER!!

You wouldn't be out there in those conditions in a single...:ugh:

You could have been in the second one. Delete Puma, insert Army Gazelle.

Wow this developed into a twins v singles real fast!


You are correct in thinking that this would not have happened if it had been a twin because low budget aviation units like Mesa PD would never, ever be able to afford a multi engine helicopter.

Let's get all the single engine helicopters and airplanes out of the sky then!! :ugh::ugh::ugh:

There is a place for everything, including singles, but operating in the police/ambulance role over urban/hostile territory is foolish. Cheap, but foolish. This is probably why Sid posted in the first place. Accidents will always happen, no matter how many engines, but try to reduce the risk as much as possible. I totally understand those who support the concept, especially if the alternative is nothing at all. My ONLY beef is people coming forward saying that it is just as safe. It isn't, the end.
If you come forward and say that the risk is higher, but acceptable to the authorities, then game on. In the minefield of litigation post accident, the lawyers would tear apart any such statement.
Let's call a shovel a shovel.