valve guide

I read an article in the recent edition of Loop, where Dennis Kenyon talks about the above. He says that this area is often referred to as the dead man's curve, avoid area or no go area and states that these are all wrong! He says it should be known as " the area of extra caution". He further states that in 13,700 flying hours and 30 years he has yet to experience an engine failure, I know many of us have, however, he goes on to state that he is not prepared to adopt non-standard takeoff and landing techniques just to avoid a few seconds when he is at risk.

I can remember making approaches into confined areas when learning and ending up in a 25ft hover from which I had to descend very slowly to the ground. On raising this question re the "avoid curve" with my instructor he laughed and said that this is what helicopters were designed for.

So whats the view guys and gals, a no go area or an area that you use with extreme caution but use all the same ??

Your views would be appreciated

MK10

any lifting/slinging pilot spends his/her day in the shaded area! what we gonna do, stop slinging? nah, avoid it WHEN you can.
mk10

HillerBee

I had 3 engine failures in one year (no bending), however never in the 'dead mans' curve. But they do happen. Whenever you're in the grey/shaded area of the curve you'll have a serious problem if you have an engine failure. The curve is determined by the best test pilots with new machines with max. performance. So as the previous poster says avoid them IF possible, our job is often in that area and that's why helicopter flying is dangerous. If you worry to much, it will be a very stressfull career. Practising autorotations from unusual entry points however is highly recommended during your career.

aspinwing

MK10 has it just about right. Use it when you must but do not make it your sand box.
Just like the 'flat-hatters' that must fly around below the tree tops; they will get caught out. Trust me. Three for me: including one one floats to glassy water and one 50' vertical EOL in a JetDanger.
I have had some crazy CPs who liked full on EOLs and I survived enough of them to retire -sort of gracefully but was pretty good at EOLs and never bent one.
Just treat the HV curve with respect.
Chimo

i4iq

Also depends where you are on the curve. For example, on the R22, at the top, the curve was produced to allow for a 1 second delay before taking appropriate action. Towards the bottom of the curve, no delay was used...

Matthew Parsons

I think the more common official terminology is "avoid area". It also makes the most sense.

Recovering from an engine failure in the avoid area is more difficult than doing so from outside the avoid area. That is why you should avoid it. It is not usually prohibited. You may be required to operate in the avoid area. It may even be safer to operate in the avoid area, depending on circumstances.

You should have a good understanding of what gets more difficult and how to adjust your technique prior to operating in the avoid area, perhaps even practice it. Also, don't get complacent with operation in the avoid area. Always be aware of it and the associated dangers. You should ensure you are alert and ready to respond to the dangers that may arise.

So in answer to the original question, I'd pick c. It's not a "no-go area", it's not an area I would "use all the same", but it is an area where additional caution must be exercised.

Matthew.

Lightning_Boy

thought it was called the money curve?

Gordy

You that right.

I agree with most here---it is a "use extra caution" curve, and operations with in the curve are subject to additional risk.

jeepys

Hillerbee,

if you had three failures in one year then perhaps a look at your maintenance man would be a good idea!!!
Either that or a change of career for life the preservation society.

HillerBee

Got another job after the third one.

valve guide

3 engine failures in a year? I would be interested to know which heli type these were on and did you ever find out why???? That has to be a record or is someone going to post something different, but 3 in a year. Think you made the right move changing career, someone was trying to tell you something!

HillerBee

It was all on the same Hiller 12. Yes, I thought someone was trying to tell me something. I didn't trust the mechanics at all after the third one.

It was in the States and I'm not implying all the maintenance is bad over there but the people I worked with had different standards. I'm very glad to be here in the UK.

Graviman

Post removed, for reasons of commercial sensitivity.

Mart

wg13_dummy

I certainly would not want a system that overrides or takes control at a critical time. It may also give a certain amount of reliance to a system and degrade awareness.


The only thing that would improve safety is good, regular training and the old helicopter pilot addage of 'always expect the worse, if it's not happened yet, it's about to'.

As for the avoid curve. The book version of what its all about says the chances of entering autorotation and carrying out a successful engine off landing reduce if you suffer an engine failure within it. Not just the low airspeed/height side but also the high airspeed/low height side too. Remember that next time you are wazzing and zooming at extreme low level. Factors A, B and C really do come into the equation.

I teach chaps to be aware of being inside the curve and the consequences should the donk stop but as has been said, it's all about risk assessment. If one can stay out of it, all the better but I would never preach that it's a 'no go' area.

AndyJB32

Graviman: I'd argue the cyclic is at least, if not more, important than the collective immediately following an engine failure (assuming you're in a single engine helicopter). Lower the collective without any cyclic input, and you're likely to have a large nose down attitude with rapidly decaying rrpm. Even if you don't move the collective, but flare hard with the cyclic, you'll maintain rrpm long enough to then lower the collective. An automatic collective lowering device sounds very dangerous to me.

wg13_dummy

I would take issue with your remark about 'don't move the collective but a hard flare will give you RRPM'.

Keep pitch on with nothing to drive the buggers round and you can flare all you like, there is only one thing the RPM will do! Flare effect will not overcome the drag produced by keeping pitch on. If the collective is not reduced immediatly after losing the engine, everything else is the worry of the board of inquiry and the crash recovery team. If you have the height, nose down is a good thing as airspeed will build up....again factors A, B and C.

Factor A= Disc tilt from a vertical auto, RoD increases
Factor B= Initial Forward speed, inflow angle reduces, RoD increases
Factor C= Clean air, forward speed, inflow angle increases, RoD reduces (hopefully this speed is approx 50-70kts).

How about a constant attitude EOL or a low airspeed auto? Almost vertical and not much cyclic input required.

Not lowering the coll sounds dangerous to me! Pitch = Drag = Sloooooow down rather quickly.

Shawn Coyle

wg13:
There is a large body of evidence that just lowering the collective is not all that's needed - at least in most helicopters. Adding aft cyclic is a very important part of maintaining rotor RPM. Lowering the nose to get airspeed is a relatively minor part of the whole equation and should only be done if the rotor RPM is in the proper range.

Matthew:
For Part 29 helicopters, with more than 9 passengers, the HV curve is a limitation. and must be avoided (except in the US when operating off oil rigs).

AndyJB32

maybe my point hasn't quite come across clearly. I'm not advising not lowering the collective, i'm trying to point out that in the first second of an engine failure merely lowering the collective without any cyclic input is not going to do much good. If i were in level flight, and (purely hypothetically) i had a choice of only moving one control in the immediate aftermath of an engine failure, i'd choose the cyclic. A cyclic flair would maintin or increase the rrpm for a second or so, by which time you would have had to have lowered the collective. Of course ideally the cyclic , collective and pedal input would happen simultaneously.The important initial reaction is to get the helicopter into autorotation, which can be done solely by a cyclic flare. If the collective is lowered, but the nose pitches down at the same time, the aircraft will not necessarily enter autorotation, thus dragging the rrpm down. You mention if you have height then nose down is a good thing as it builds airspeed...........that's ok when you're established in the auto, but try putting nose time as you enter the auto and you're likely to encounter some fairly serious problems. Airspeed doesn't matter whatsoever until you're appraoaching your flair height. If you've got the height it's perfectly safe going back to 0 KIAs or moving backwards in an auto. However rrrpm matters any time you're in the air.

Camp Freddie

to try and add to this, what I note is that no one has mentioned (might have missed it) that the H/V curve is calculated for take off, when typically you have a higher collective lever setting than for landing.

when landing the shaded area will still be present but smaller than the graph in the POH but it is not calculated or shown anywhere.

for commercial ops (at least in the UK), operation is not premitted in the shaded area, and for non commercial ops flight through the shaded area is happening everyday when you do an approach unless you keep your airspeed up until pretty close to the ground.

In fact when you teach approaches for the PPL (EX 10 in the UK), the way they are generally taught which emphasises keeping the "apparent rate of closure" constant, ensures that you fly through the shaded area, but as discussed above, you cannot say exactly when you are in in it, because you are landing and the data is not available.

overall it would seem sensible not to fly in the shaded area if you dont have to, and I see people flying in it who dont have to all the time!

my old instructor also warned of becoming to obsessed by the graph at the expense of safety by saying "fly into the avoid curve, not the trees !"

regards

CF

212man

CF, the statement:
"to try and add to this, what I note is that no one has mentioned (might have missed it) that the H/V curve is calculated for take off, when typically you have a higher collective lever setting than for landing"

is not true; the H/V curve is plotted for level flight, and the graph in the RFM will often state this. The published graph is only valid for one set of ambient and weight conditions whereas in reality it expands and contracts. It may even disappear given the right circumstances (how else can you do a vertial Cat A Take Off?)

Valve Guide, the subject of H/V curves has been discussed ad infinitum on an earlier thread and you may wish to search and find it.