HV Curve engine failure question

[paco]

Yes, it would, the disc will behave the same way, except that, of course you've got to be an awful lot quicker dumping the pole!

But your question is not as hypothetical as you think - some people going into hotel car parks in Robbies may well be in just that position one day - which is not, BTW, an invitation to go and practice it! Discussions like these are simply meant to give you some ammunition in case you ever face the situation - but I'm sure you knew that already!

Phil

[170']

...

100 - 200’ hovering auto.

Straight down is the only way to go. The guys in various mountain flying schools will train you for it as part of the mountain course. I did mine in Penticton and couldn’t ask for better training…With a couple of periods devoted to this topic alone, practical not theory.

In fact it was the only thing we did that didn’t have a long theory component attached.

I did several with various inputs from the IP and then another 20 or so unaided. Currency is key in this type of training event and unfortunately most of us don’t get to keep the currency going once back on the job. What we do get from it is the basic training and the confidence that we know the correct procedure, not just a stab in the dark and hope for the best.

But… There are critical issues regarding checking the sink rate and rpm control for various types, these don’t belong in a forum…This is not something to practice alone or with a cocky local instructor…The guys that teach this level of instruction are some of the best pilots around and have huge backgrounds in just about everything.

This training was expensive over 20 years ago (paid by company) and I would hate to pay for it myself. But if you plan a lifetime in utility ops, maybe it'd be worth thinking about...

…170’

[nigelh]

A few years ago i asked the same question and my instructor ( well known so no names ) said we could practice one or two . First one from 400ft was no real problem but you learn straightaway that forward on the cyclic is NOT the done thing as it turns you into a javelin and you will be vertical nose down . So we then did one from 300 ft , roll off throttle , down collective , immediate cyclic back a bit and flare and then on ground . This time it seemed to be all very quick indeed ...it is then that i point out the altimeter is still at around 70ft !! I think in the right hands you can get a 206 down from any speed/hight .

[Thomas coupling]

I've just been reading up on confirmation bias - a phrase used by psychologists to describe someone who wants to believe in what they think is true, even though it isn't.
A Height velocity curve has been devised to indicate the aircrafts flight characteristics when it is 'low' and 'slow'. Some are generous in their dimensions whilst others not nearly so.
The bottom line Nige, is that FOR AN AVERAGE PILOT, his/her reaction times will not prevent the cab from recovering in time to make a safe landing. It doesn't mean a terminal conclusion, but it almost certainly means the a/c will be damaged - severely.
There's a reason why it's colloquially named the "dead man's curve"

If people persist in thinking this is a challenge - something that can be beaten....they are delluding themselves and all those they teach!

[Shawn Coyle]

Those who think they can 'beat' the HV curve because they've demonstrated it are not paying attention to the reality of the 'surprise' factor that real engine failures have.
Everyone I've spoken to who's had a real engine failure (including me) was initially very surprised and took much longer to react to the failure than they anticipated.
So- what you can do in training is not always what you'll see in the real world.

[n5296s]

Just wanted to say that as a low-time heli pilot I'm finding this thread very interesting and instructive. Of course I know that you *should* stay out of the HV curve - and in my case do - but if for whatever reason you can't it's jolly nice to have some idea what you could do to try and save your life!

In particular I would have thought - until reading this - that it would make sense to put in forward cyclic and try to get some forward airspeed. Useful to know this is a bad idea!

I do have one question... if you find yourself in this situation, at what height would you start to pull collective? 20 feet-ish would seem about right but it would seem best to get this right!

n5296s (or n9888s)

[Scrawny]

Has anyone here actually had a 0 airspeed engine failure that they can comment on or does anyone know someone who has? Would be really interesting to here what happened and what there thoughts were.

[newfieboy]

Scrawny,

Yes and yes. I have and know quite a few guys that have. Nature of the beast in this part of the world, as lots of single engine longline ops.They all say the same.... um didn't see that coming, and most were banged up with varying wounds, some even did walk away. Again, the guys I know admit purely by luck as opposed to "I beat the curve because I went right, punched the load and put er down". that they walked or crawled out the wreck.In the real operational world, movng drills, pinning towers, hydro etc, at 200ft AGL zero airspeed concentrating on pinning a tower, head out the window, your hopefully going to be able to catch it at the bottom and pull for all your worth, thats about it, in my one and hopefully the last real experience.

I am with Thomas and Shawn on this, and we do practice regularly due to the nature of our work, not because we want to, but as a requirement to keep it as current as we can. We can all put the nose down or aft cyclic, whatever it takes, while training and ready for it (I hope). Anyone playing in there to see if "they can beat the curve", are asking for a nasty suprise one day. For real, the suprise and initial denial, is to say the least, suprising in itself. I for one am now always expecting it, but catching it before taking the fast elevator ride down is another thing.It is survivable, even walkaway doable, as is testament to the guys I know.Not because we are super pilots and practice, practice.We just were lucky to do something right at the time/luck was on our side.....whatever. I get paid good coin to be in the curve all day, for a reason... it can be bloody dangerous. But I minimise the risk, situational awareness at all times subconciously it just may save your life, even if you didn't realise it.

Happy flying Longline Brothers, be safe.Newfie.

[EBCAU]

Newfieboy: " I get paid good coin to be in the curve all day, for a reason... it can be bloody dangerous. "

I hope you do get paid good coin too!
The very nature of this thread illustrates why you should. But I wonder if it is really enough, in comparison to say....ummm..... an IFR helicopter pilot for instance? Would you be in their league pay scale wise? What do others have to say on this? After all, if you've got the money and inclination most could go out and get an instrument rating, co-pilot position to lift the skills, and Bob's your uncle, you can now watch your nice shiny helicopter fly itself from A to B on autopilot. (couldn't find an emoticon for tongue in cheek)

You, on the other hand, probably roughed it through some pretty harsh environments and taught yourself some pretty special skills along the way. If you get plenty of work in your specialist field it is probably because you excel in it. Now your working day involves sitting in the dangerous zone being discussed here. Here you are reciting useful of ways to perhaps save lives if your very lucky, and accepting that you could be banged up a bit if you are just lucky.
Unless you are paid far more than I think you are you are probably not paid enough sir.

And before all the IFR boys wade into me on this, I didn't say you were overpaid.

[Thomas coupling]

N5296s (whatever that alludes to?)
Might I suggest that if you have to think about what to do in the event of a donk stop in the curve, it's too late
I use a well honed, well practiced technical procedure called: survival instinct (been with me all my life now).
Donk stops, brain winds up, "fly" the terminal flight path into minimum obstruction path...cushion touchdown.
IF time permits...shut engine(s) down, fuel off. But the chances of being that cool and collected are infinitesimally small.
PS: Did you know that twin engine helo's have dead man's curves too

[Epiphany]

I would guess TC that it alludes to his aircraft registration. They have a different numbering system over there. Besides you didn't answer his question.

N5696s - the height at which you would pull collective depends on a variety of factors including your aircraft type - high inertia types are more forgiving and as a previous poster says it is actually possible to become airborne again with the rrpm left after an EOL. With a low intertia type your rrpm would be very low on touch down.

Apart from training I have never been in this situation (and never want to) but as previous very knowledgeable pilots here have indicated it will come as a surprise and the only defence you have (apart from avoiding the HV curve) is your reaction time. When you see the ground rushing up at you - you will pull the collective!

[rick1128]

TC,

Not only do twins have a HV curve, the chart is in the limitations section not the performance section like singles. Plus, since most long line operations are heavier than Cat A weights, about all the other engine will do is help cushion the landing. If it is still running. Since in most twins the engines sit side by side and feed off the same fuel tanks, if you have a fuel issue, you will most likely lose them both. And if one engine comes apart it WILL throw pieces into the other engine.

[KqQNr]

Very interesting thread. To add to TC's observation, three-engine helicopters have HV curves as well (one engine, two engines, and three engines out). To expound on the original question, I believe it is critically important to know and understand the basis of the HV diagram. In other words:

1) What was the recovery delay?
2) What indications are there of an engine failure and how is this factored into the initiation of a recovery?
3) To what type of surface was the recovery demonstrated?
4) At what speed was the landing accomplished that resulted in certification?
5) What is the basis for the HV curve development (for the military guys, look in the flight manual. If the data basis reads "flight test," then someone did it. If it reads "estimated," then Bill Gates did it (or whatever computer modeling system is employed by the OEM)?

WRT the Bell 206 family, the collective-to-pitch coupling does result in a decent amount of nose down attitude (assuming you are in forward flight and you lower the collective!). In my experience doing HV demos, some students would add forward cyclic while lowering the collective, sometimes resulting in an undesirable nose down attitude (I've seen in excess of 50 degrees nose down on way more than one occasion). The resultant desire to make the Earth look smaller can be an issue if the cyclic is applied aft too rapidly while at low g (i.e., mast bump - I know of two instances where this happened - no torque on the mast in these cases was a good thing).

As Shawn stated, the collective must come down. There is a point at which the rotor will stall at low RPM (probably at a higher RPM than you think) and no amount of altitude or speed will allow you to recover.

Having spent a fair amount of time tied to the water, there comes a point where one may decide that sacrificing the structure to save the occupants may be a more desirable (or perhaps the only) alternative when compared to trying to fly the aircraft away from an unrecoverable, power-limited situation. This is the essence of the question that has been brought up before: "Where am I in the HV diagram, what does it mean, and what should I do?"

[n5296s]

I would guess TC that it alludes to his aircraft registration

Indeed. I thought it was a bit too obvious actually. Sometimes on this forum I sign as "n5296s/n9888s", that shouldn't be too hard to decode either. Google is very helpful.

When you see the ground rushing up at you - you will pull the collective!

That's what worries me! Pull it too soon and you will be just as dead! I know from landing the Pitts that getting the timing right is absolutely critical, as in, you have to be right to within a couple of feet to make a good landing and within ten feet to not break things - and coming down at 2500 ft/min that is not very long. (Power off - my normal landing technique - the Pitts comes down faster than the R44 in autorotation. Plus you can't see anything. I found autos quite tame...)

[newfieboy]

Originally Posted by n5296s

the Pitts comes down faster than the R44 in autorotation. Plus you can't see anything. I found autos quite tame...

Mmmm....

Guess you need to get with the real world, on ops with a 2000-4000lb load on a 100/200ft line, with your head doing the vertical ref while holding the load as riggers/drillers apply their subtllty (normally with a big F###off hammer)to pin it in place. When the donk goes quite, maybe you might show some interest then, I can assure you, it ain;t tame...it'll be the fastest elevator ride you ever took, and if you even got time to reflect on the way down, I hope it will be the wise words, and wisdom of Shawn and the boys. Stay out of there, unless you getting the big bucks and understand the inherant dangers. If you work in the curve with the attitude, that you find autos pretty tame in the 44, you ain;t comng to work with my crew. And believe me as another poster on this fine thread said, Epiphany I think, when its time to pull, you will, just remember a sound bit of advice I got from an old salt many years ago. "on the way down ya wanna pull, wait, pause count to two, then give err, worked for me. There isn;t any room for guys that don't understand the risks, or don;t take it seriously working in the curve.You really do have to be on top of the game to minimize the risks involved.........Just my two cents worth with aprox 10,000hrs doing it, and again tommorrow.....de-ja vu.

[Thomas coupling]

Epiphany; I think you'll find I did answer his Q. Like newfieboy said - it's no good looking for numbers or settings at a time like that. You just know when it's right because you know your a/c and its characteristics. 20' in an R44 is absolutely useless in a MiL 26
At the moment critique you need to feel that helo onto the deck not be looking in at rad alts or height measuring devices.
I suspect N5296 has yet to experience a juicy malfunction......
Rick1128: are you suggesting that dead mans curves exist for twin engine helos only when both their engines stop?
I think you'll find the curve is for one engine stopping on a two engined helo.

[n5296s]

I suspect N5296 has yet to experience a juicy malfunction

Dead right. Long may it stay that way - fixed or rotary (touches wood).

Newfie... look, I have the greatest respect for working heli pilots and everything you do and the skill it takes to do it safely or even at all. (Not that I wouldn't mind having a chance to try it myself...)

When I said "I found autos tame" I was talking about normal practice autos from 800-1000', not for-real engine failures in a hover at 200'! And I just meant the sensation. I'd guess that for most people, the visuals of their first few autos are fairly terrifying as you plummet earthwards at 2000 ft/min or so. But the Pitts plummets if anything even faster. And still the last 50' are anything but tame.

I practice autos all the time - and love doing it. But 100% agree that all the practice in the world is absolutely not the real thing.

[rick1128]

TC, I realize the HV chart for a twin is only for one engine out. My statement was that the chart was in the Limitations Section rather than the performance section.

Jim, Thanks for your notes. As for containment rings, I have mixed feeling about them. I have a good friend that had an engine come apart on a S76A. It had the containment ring and the other engine failed soon after. Pieces from the 1st engine FOD'd the 2nd engine. What I heard about the investigation was that at least one piece of first engine entered the second engine and was fed further into the engine causing more damage and the failure of the second engine.

Many years ago, an acquaintance of mine was flying a Beech 99 for a commuter airline. One of the engines came apart and one of the turbine blades entered the cockpit and cut his leg off. The blade was hot enough to cauterize the wound. The aircraft did not have a containment ring. While this sounds bad, it could have been worst. There were discussions between the FAA, NTSB, Beechcraft, PWC and the operator that indicated that if the containment ring was in place, the situation could very possibly been worst. What I was told by my acquaintance was that the piece could have very possibly entered his head or chest cavity. It would have been deflected and reshaped in some manner. Even if it hit his leg at the same spot, the change in velocity and angle could have caused a larger wound and he could have bled to death rather quickly.

And Jim I agree with your comment about engine capacity being a reason for twin engine helicopters. But keep in mind the 214B, it has one BIG engine. Two smaller engines are most likely much less expensive than one BIG engine.

[newfieboy]

n5269s

Dude, Hey no worries.A tad bit of advice if I may, take it as you will, you gotta stop comparing engine failures in the curve, and I take it a stude pilot, no offence but I would say a little short on knowledge of operational, make money stuff , no comparision a landing with a Pitts sounds a little iffy to me. Think 'll take the dead mans curve anyday.As a kid in the 60/70 era I seem to remember Rothmans making it look a doddle ( sorry I degress, tobacco advertising and all) We train often, and ya know what,ooh engine failure transitioning off the pad with a 2000lb load 100ft below. Blimey, Im gonna punch the load and put her in reverse, Mmm pad right below me now, better than those soddin big poplars, still going to hurt though Ochh....Can you do that in ya Pitts, didn;t think planks had a reverse gear. Sorry matey couldn;t resist. If its any relevance,longline ops in Northern Ontario suberb today, what a beautiful fall day, trees all colours,wildlife active wind 10ktsW unlimited vis and ceilings, I love fall/autumn in Canada.Oh and the floatplanes just kicked 40 drums jet A off, and two drills ready to turn in the field, hrs and scenery, Mmmm life goodSod it, Ill worry bout the engine failure if/when it happens in the curve, you can't make plans for that kinda ****....enjoy the view....Newfie.

[paco]

trees all colours, wildlife active wind 10ktsW unlimited vis and ceilings, I love fall/autumn in Canada

Yeah, miss that. And the Timmy's

Phil