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.

.
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.

At the end of the day, it is all an economic trade-off. In Maricopa County, where Mesa is located, the City of Mesa has 3 ships (now two going back to three by august), Phoenix has 12 (1 is a twin), Maricopa County Sheriff has 4, Arizona DPS has 4 and all the other cities are talking about getting their own.

So, you take 22 single engine ships in tight budgets and you covert them to twins in acquisition, training and operating costs.

If you look at the total number of accidents/incidents relating to engine failure in the last twenty years resulting in an autorotation, the grand total is one encounter. This one.

If you assume public safety money is fixed, you can cut the ships or hours in the air and do a cost/risk analysis of what happens without a ship in the air. Is an officer shot, do they lose a suspect, is the high speed chase worse? Or, do you cut the number of officers on the ground?

With respect to police air units, the American system has done that analysis and come to the conclusion that factoring in risk versus reward, singles are the way to go.

when the engine fails in a single you have to land, sometimes messy, very occassionally fatal.

when the engine fails in a twin, sometimes it is non-eventful, sometimes it is an accident and sometimes fatal.

BUT sometimes in a twin you also have a fatal accident that you would not have had in a single, from other causes. the critical components have to work harder to pay for for the occasional imunity. Less engine failure accidents paid for by more gearbox/tailrotor/freewheel units/fuel systems/ performance cost/ tail boom failures/ 'pilot error' (shut down wrong engine, confusion etc) etc

All things will happen in aviation to some extent.

PROPORTIONATE REGULATION does not call for twins.

the sums don't add up, gazelles just did not have an engine failure rate that justified twins FULL STOP

I'm hearing an argument that suggests that all air ambulance & police helicopters should be Robinsons. :eek:

Now, just where does that line get drawn?

AnFiLol, sometimes AnFI (really!) your posts are really quite laughable.

Trying to convince some exponents of the "single engine is best" theory is pointless. Even though they have little or nil experience of multi engined aircraft, (and probably little prospect of flying them which may explain their stance), they think they know better than folk with a far broader experience .... and better than the regulatory authorities.

Some obviously fail to realise, or choose to ignore, the fact that all pilots now flying twin engined helicopters began their careers flying singles.

GoodGrief, why would singles not be flying in those situations? Why the banging head symbol? I just don't understand that one.......

1. Self preservation.
2. Common sense.
3. 20NM out at 65kts wind. What happened to 'autorotation to shore'? And the sea state in that is ? Floats wouldn't really help now, would they?
4. 300ft cloud base at 45kts. You'd be buzzing around at 200ft or even at tree top level? What happened to the 500ft rule?

Maybe I'm too much of a coward and know to say 'NO'.

C'mon, you want to stir the pot ?

GoodGrief

500ft rule? what 500ft rule?

Common sense?? When you have to get a job done and it is within the aircraft limits, why not??
Auto to shore, I will accept that, so singles will limit how you operate if there are any areas of water??
Common Sense?? Matey, see above.
What 500ft rule??

Ok then, lets 'stir the pot' whatever that means.

Engine failures are debated as theoretical events and dismissed with statistics-except to those of us who have had an engine failure. It then becomes the primary consideration in whatever you do for the rest of your life.

Doesn't apply to the Military, which this was.

ss:

"AnFi Quote:
the sums don't add up, gazelles just did not have an engine failure rate that justified twins FULL STOP
Lol, sometimes AnFI (really!) your posts are really quite laughable."

Excuse me! Are you actually saying something or just trying to discredit? - the fact of the matter is Gazelle losses through engine failure were negligable - Lynx losses through engine failure have not been - the utility of the gazelle was huge and it's bang per buck for the tax payer was high.

I know of three (UK MIL) Lynx engine related accidents although i know of no (UK MIL) engine failure accidents (not that I'd be surprised if there had been).

Not to mention the extreme downside of performance for 30yrs for lynx caused by carrying spare engines, instead of useful payload.

Substance, not just rudeness. SS!



Huey Racer : "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?" good point , carrying two engines does not seem to have delivered anything like 100,000 times lower loss rate. Irritating when the facts get in the way of a determined ignorant theory.

Oh AnGi, there you go again!

Are you really suggesting that the Gazelle could have fulfilled the role that the Lynx was brought in for!

As I said before, your posts are laughable.

Instead of saying 'you know of ....' please post links
(Did you see what I did there!)

and what does;

... mean?

I'm not going to trawl through the relevant reports, but your argument is flawed when your side is looked at sensibly and not restricted within certain parameters to meet your needs;

http://aviation-safety.net/wikibase/wiki.php?id=46173

"Last edited by SilsoeSid; 29th Jun 2014 at 23:31. Reason: link to end silly irrelevant restrictive side of discussion"

Err too many sherbets?

Your example is of an obscure user, unlicesed to fly, NOT killing themselves!!
It is possible to find a Gazelle fatal due engine, but you have to go a long way back in time and far out in geography.

The reason to use the UK MIL is that the other circustances are controlled, avoiding side issues like whether the people had licenses.

It is not easy to provide a list of UK MIL engine related crashes in LYNX because it seems that the data is obscured. Your friend was killed in one, those nice chaps were killed in Afg, some other nice guys hit the water (both engines shut down, for some odd reason). Many ex-lynx drivers have told me of their accidents and close shaves. They don't appear to be documented:mad:.


SS; "Are you really suggesting that the Gazelle could have fulfilled the role that the Lynx was brought in for!"

Errr, No, obviously not.
The point was the engine related accident rate.
Not whether it could land on ships, or had a sliding door.

Imagine the high performance machine a Lynx could have been as a single.

AnFi

I thought that the double ditching, one fatal in the GM had shut you up for a while, evidently not.

The engine argument is one thing. Saying that components on a S-92 or EC225 are more stressed is garbage.

Twins tend to be better equipped and IFR capable. You can't really do that in a single if you actually want to carry anything.

AnGi;
As I say, laughable posts!

1.The outcome would have been worse if it was single engined.
"Crashed on emergency landing after cockpit had filled with smoke. Caught fire and burnt."

2. Cause not yet known.

3. The 'for some reason' the engines shut down was because they ran out of fuel having been misdirected on the way back to 'mother'.
"During Exercise Marstrike05 is was misdirected back to HMS Nottingham. It ran out of fuel 41 miles from the ship and made a controlled ditching alongside MV Wilhelm Schulte in Indian Ocean 120 miles off Oman. It sank in 2,800 meters of water but the crew were rescued safely"



Aviation Safety Network > ASN Aviation Safety WikiBase > Lynx


A long way back (2011 fgs!), but not as far back as your Lynx examples, and with you mentioning Lynx incidents in Afghanistan & the Indian Ocean, how does Geography affect this discussion?

ASN Aircraft accident 20-AUG-2011 Aérospatiale SA 342L1 Gazelle L611
ASN Aircraft accident 19-JAN-2010 Aérospatiale SA 342K Gazelle CN-AIP
Etc

Aviation Safety Network > ASN Aviation Safety WikiBase > Gazelle

AnGi;Wow, even more high performance than the Worlds fastest helicopter! :ok:

Well they took out all the spare seats and made it as light as possible I believe. Imagine how much lighter it would have been if they could have taken out the spare engine and all the fuel required to power it too.:}

In 25 years of flying around in helicopters, i've met numerous people (and i'm one of them myself) who have said "and if that had happened in a single we'd have been stuffed".

I've never met anyone who said "If i'd been in a twin we'd have been stuffed".

Will two engines always save you? No.
Are two engines more expensive? Yes.
Does having two engines increase the statistical likelihood of having one of them fail? Yes, of course.
If you have an engine failure in a twin do you have a chance of flying away from it? Yes
If you have an engine failure in a single can you fly away? No

I love the comment made about how fast the topic of conversation has changed to Singles Vs Twins.....and then you notice that the gap between posts 49 and 50 is.....4 years!!

Meanwhile back at the ranch....Most here are talking from an insiders perspective (obviously!) because we are all passionate players in some shape or form...but...remember this: two types of people run this world: Lawyers and accountants. It is they who make the final strategic decisions because they are able to stand outside the box and determine if the operation will succeed or collapse.
They have determined that on the whole, in the round, at the end of the day - singles beat twins hands down for cost effectiveness. SAFETY really does come second even though the opposite mantra is shouted from the roof tops (this is so that the industry can be seen to be PC).
Example:
15 years ago the FAA and the (now) NTSB came to the conclusion that the design flaw in the 737's rudder screwjack mechanism was cheaper to resolve by paying out to all the deceased familes of those who crashed or would crash in future; compared to grounding the entire global fleet and replacing said defect.
In the cold light of day, these two organisations determined that the final cost to insurance companies of the death of a US citizen was: (1999) $186.
They did the maths. looked at the probabilities and the dollar won - hands down.
Same goes for modern jets flying over the oceans of the world on ONE engine.
RISK = frequency x outcome.

And so it came to pass that on the whole it is better for the organisation to fly singles because the impact of losing one single and its entire crew is marginal/minimal.
UNLESS you are onboard at the time.
I had the inlet guide vanes on my SeaKing (S61) shut in the hover over a sea state 7.
I had a compressor blade go in my AS355 over the middle of a city.
I have had compressor stall in another AS355 incident.

In any or all of those - I suspect my chances of being here today would have been seriously curtailed if those incidents had been on singles. Thus I am biased but in the big picture, my subjective overview is lost in the noise that is corporate diligence and the bottom line: money.

Try responding to this thread thru the eyes of an accountant or lawyer?