Regulations for the operations in dead man's curve

[Lander]

Hello,

Is there any explanation about the operations in dead man's curve? I am interested in a special case:

* A helicopter with loss of mechanical power from both engines

This case is not considered as catastrophic in functional hazard asssesments since autorotative landing is possible.

Here is my question: Is the red area in H/V curves (dead man's curve) considered for these kind of analysis? If yes, should not it be considered as catastropic since autorotation is not possible in these region?

I already checked CS-29 but could not find an answer.

Any help will be greatly appreciated.

[coning angel]

I thought that Dead man's curve was just a shaded part of the Height-Velocity diagram which, in the event of failure of a power unit, a successful autorotative landing was not 'guaranteed'. That's not to say it isn't possible.

No regulations? I didn't think it was regulated?


Weren't these just the figures/speeds etc that the test pilots found when conducting flight testings?

[detgnome]

Would it not be classed as perf class 2 or 3 operations? (2 I guess as I believe 3 relates mainly to single engine ac)

[JimL]

Not quite detgnome; PC2 and PC3 with exposure (not the normal case) and, for CAT, requires additional approvals.

PC3 is not just for singles; it is for any aircraft which cannot sustain an engine-failure and maintain its projected flight path (i.e drift down is permitted in both PC1 and 2). It is limited to 9 or less passengers.

This is outside the design requirements, a double engine failure in a twin is not considered (autorotation is but under a separate rule). As I have said in the past, a double engine failure from independent causes has a probability of 1 x 10**-10 - i.e. it is not really your day.

Auto-rotation is not the only issue (usually dealt with as a requirement for a safe-forced-landing), hence the requirement for PC1/2 for flight over a hostile environment (safe-forced-landing not probable).

Jim

[[email protected]]

Lander - you just operate in it and hope that JimL's maths are right:)

And if they are wrong you hope you are as good as Chesney L Sullenberger:ok:

[Geoffersincornwall]

No-one has yet mentioned that your twin engine helicopter RFM should provide data on the 'Single Engine Avoid Curve' (SEAC).

This describes those height/speed/weight combinations at which it is possible to continue safe flight in the event of a OEI situation.

If your task requires you to operate inside this area - for example low speed low level search - then you are advised to talk to your regulator. You want to avoid a situation where a post-incident situation leads to an embarassing lack of insurance as you have been ruled to be operating outside the RFM limits.

To make pilots aware of the need to stay clear of the SEAC some special training may be useful. When we were in that situation with the Bo105 (which was not exactly a 'star' in the OEI stakes) we would include a practice OEI from the hover just above the SE Avoid Curve. It required quite a seriously extreme manoeuvre - instant 20 deg nose down - and was a good way to convince our pilots that languishing in that regime was not to be recommended.

Nonetheless inclusion of this in our OPC helped to convince the regulator that we were competent to carry out such manoeuvres. That said we were operating as a CAT Police operation not PAOC so wonder how things are today under that regime?

G

[JimL]

Touche Crab - I did, once again, specify 'from independent causes'.

Jim

[212man]

Personally, I think it is not particularly helpful putting the H/V curve in the RFM section 1: Limitations! It is further complicated by the fact that most manufacturers pay lip service the issue and simply publish a single graph for a 'worst case' situation of a high DA and mass. I say 'most' because (as Geoffers will know) some manufacturers - such as AW - publish very detailed information.

The fundamental point is the curve is not fixed - it is completely amorphous depending on a number of variables, and in some situations if may completely vanish (clearly when talking about ME aircraft!)

[ilter79]

Thank you all! But I still need to find some FAA or EASA documents to convince some people about the safety issues...

[GoodGrief]

This Video leads me to believe, there is no such thing as an H/V curve...

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[Shawn Coyle]

For Part 29 Helicopters with more than 9 seats, the HV curve is a limitation. Not performance, not something 'nice to avoid' - it's a limitation.
Pure and simple. You must not fly there - doesn't matter if you don't have all the seats filled - if you have a configuration with more than 9 seats, you must avoid the HV curve. Unless you have Category A.

[JimL]

...except if using the exemptions contained in 'PART 91.9(d)' or 'Appendix 1 to JAR-OPS 3.005(c)' or, in the proposed EASA regulations, 'OPS.SPA.035.SFL'.

Be warned all of you Aerial Work and GA pilots out there.

Of course, if certificated for Category A, the take-off/landing procedures specified in the RFM (if flown as specified) will keep you out of any HV diagram. Hoever, even if certificated in Category A, you still have to stay out of the (modified) HV diagram (unless using the exemptions shown above).

Jim

[chopjock]

"Dead man's curve" is completely the wrong term to be used. People that use this term are most likely ignorant of the RFM. The correct term should be "Height Velocity Diagram" and is sometimes referred to as an "avoid curve" and can be found in the performance section of the flight manual.

It is just an "Avoid curve" though. You do not become a dead man just by entering it.:rolleyes:

[alouette3]

Agree with you, chopjock. However, Dead Man's Curve has quite a zing to it and it gets your attention. Compare that to 'Height Velocity Diagram' :bored: . It makes the war stories so much more interesting: "there I was in the dead man's curve at O dark thirty----" as opposed to "there I was in the avoid area of the height velocity diagram----" You get the picture.:)

Alt3.

[chopjock]

Talking about wrong terms and war stories, on films they always have the pilot say for example,"ETA 15 minutes", again completely wrong, a professional pilot in the real world would never say that, as we all know that is just for the viewer who does not know any better. :)

[Benjamin James]

GoodGreif, that video is done as part of autorotation training and does nothing to prove the H/V curve doesn't exist.

For one thing they use their altitude to create forward speed, speed that could not be found without it.

Second, the H/V curve is based on a max performance scenario. Why do you think that it's perfectly acceptable to approach a landing at 50 feet at less than 25 knot's or so.

[Darkhorse30]

HV diagrams are determined by flight test after some empirical analysis. An interesting read is the applicable portions of the FAA Advisory Circulars 27 and 29 which tell one how to get the data. Also, the military has somewhat different criteria. One of the things that jumps out is that its determination is highly dependent on the test pilot's method/talent/experience. If you have the manuals available, compare the HV diagrams published in the Bell 205A1 RFM with the one in the Bell UH-1H. The aircraft are physically the same and you would expect the HV's to overlay each other pretty closely. They don't.
I have a personal problem with HV diagrams anyway. It is a sterile test done over a smooth flat runway. How many times do you hover over a smooth flat surface, OGE. If you spend much time in helicopters in the real world, it's a rare occurance.

[Upland Goose]

It's a young man's game!

When we used to carry out Check Rides (Base Checks) at Dollar and then PDG we used to say we earned our living in the "Avoid Curve" - let's explore!

We did and it was hairy, but good value. Thankfully we learned a lot and bent nothing.

I'm more a pipe and slippers man now!

UG:8

[nigelh]

After a hundred or so of those bumpy running eol,s i bet your all just gagging to go and fly that little beauty arent you .....NOT !!! A pointless exercise which will statistically almost certainly end in a prang followed by yet another robbo insurance claim.

ps the 206 can actually be landed safely from any height / speed and i cant recall ever having a problem in the 47 either ...hence they are both ideal training ships .

[Shawn Coyle]

Darkhorse 30:
The reason for the difference in size of the HV diagrams is the different methods used by the civil world and the military. The civil world requires a one second intervention between failure and moving the collective - the other controls can be moved immediately the engine fails. The military requires two seconds between failure and moving any control. A huge difference.
In the military OH-58, two seconds intervention in the high hover results in a yaw of at least 90°. Yet surprisingly, the original HV curve using this method was only slightly bigger than the civil Bell 206 curve. The high hover point on the HV curve in the military manual was raised 200' because most of the Army instructors could not handle a failure at the original height. I have the original reports.

Nigelh:
Using the techniques and methods described in the relevant advisory circulars, the Bell 206 cannot be landed safely from any condition. Try an engine failure from 50' in the hover at 7,000ft DA with no wind with one second between failing the engine and reacting to it. Not only will you hurt, but the aircraft will be significantly damaged. The curves are conservative to a degree, but they take into account things that are not considered when you're doing a training trip where you know an engine failure is coming.

[topendtorque]

I think the statistical, 'accidents per number of hours' is a bit of humbug. It is far more relevant to quote the number of emergencies per the number of pilots.
I.E. We all know someone who has had a problem, and many of us have had many problems, not just with silence out back, but also any of the mryiad reasons why a 'controlled' silence is far better for continued good times. T'R drive failure or, etc, etc.

The 206 may be a prob at 7000'da, but by crikey the '47 is a gem at that, and higher.

Lander,
we operate near there all the time, but we teach safety mechanisms. Thirty knots when turning downwind or at least translation please most all the time, or, when at low height having just zoomed up a bit and there is no airspeed then at least position the aircraft with airspeed potential. I.E. Leave the disk tilted downwards I mean while you have a good look about, then just follow downward tilt side of the disk.

With two engines I would assume that you personally check the single tank full of fuel on the refuelling tender? maybe plenty of twin supply from the same tank??

Giving a person the gift of practised accomplishment from a difficult area of the HV curve is one thing, to loiter unnecessarily in there is totally another of foolhardiness.

Shawn
we have spoken before about this absurd practice of the military, of two seconds delay. why is this? They will never get to see the limits potential of any aircraft by putting such blinkers on their insular thinking.

For sure, certification authorities need to insure that they have an aircraft that the normally slightly slower person can land. One second is more than enough.
cheers tet

[Shawn Coyle]

Ttopendtorque:
We could debate the 1 vs 2 second rule for a long time. There is evidence (and experience) that 1 second isn't long enough - it's hardly time for the 'this can't be happening to me' to flit through your mind. 2 seconds with no reaction on any controls is too long and unrealistic on the other hand.
From my experience, if you use the same criteria as was used to develop the HV curve (no matter which intervention time), the HV curve is a valid indication of the area to avoid. Sadly, a lot of hot-shot instructors think they can demonstrate that they can 'beat' the HV curve - but they do this without understanding what the curve actually represents.

[[email protected]]

Shawn, is the 2 seconds not a measure of the possible workload in the military cockpit where not only is the aircraft being flown but also weapons targeted, tactical decisions being considered, multiple comms in use etc etc.

If 2 seconds had been applied to certification of civil aicraft, maybe we wouldn't have lost so many lives in the R22.

[Darkhorse30]

Shawn,
I have little experience in OH-58's, but I do know that there is a difference in rotor rpm in the OH-58A and 206B. Also, if you compare Bell 205 and UH-1H HV's you will see that the 205 HV is set at a higher OGE height (for a 1 second delay) as opposed to the UH-1H (for a 2 second delay). To me this indicates a technique difference, because in a sterile world they should be the same curve.
I still question the validity of the test and the need for the curve. It hasn't stopped loggers, fire fighters or anyone else from operating much of their time square in the middle of the "avoid" areas.

[SASless]

Crab,

More likely it is designed to fit the speed of thinking by the military mind.

[Shawn Coyle]

If the HV curve did nothing but warn people that they are operating in an area where they need to be absolutely spring loaded to reacting to an engine failure, then it has succeeded. Spring loaded means - knowing all the various symptoms of the failure, knowing what you're going to do ahead of time - i.e. where you're going to go, how you're going to try to do it, and so on.
if it does that, then it's succeeded.
For those flying helicopters with more than 9 seats, it also means that the authority is expecting a higher level of safety from these helicopters, and that it's a limitation. You simply must not fly there to put all those bodies in danger.

Darkhorse - not that familiar with the 205/UH-1 charts. I'm surprised the military one is slightly smaller however!