How long have you got if the engine(s) go quiet

[Wigglyamps]

Just wondering how quickly you have to react to the engine(s) going unexpectedly quiet and putting down the collective, do larger radius rotors provide a larger time margin. Had a first flight in a Schweisser(?) 300 the other day and the chap reckoned you have at most 2 seconds :bored:

[Farmer 1]

About half that.

[Robbo Jock]

As with everything aviation-ery, it depends on a lot of things:
The inertia in the rotor system (the more inertia, the longer it will take to slow)
The drag on the rotor (the more drag, the quicker the rotor will slow)
The amount of pitch you're pulling (related to the above. The more pitch, the greater the drag)
The phase of flight you're in (related to the above. In descent, you'll be pulling less pitch than in the cruise and in cruise less than in the climb, so your reaction time is less in each case)
Your speed (you can trade speed for rotor RPM)
The rotor RPM at the time of the failure (the higher the revs, the longer they'll take to decay to disastrous levels - though this won't make a huge difference given that rotor RPM should be kept within a fairly tight range anyway)

Larger radius rotors could take longer to slow (greater inertia) but they could be generating more drag so slow quicker.

I've mainly flown the Robinson R22 which has a low inertia rotor system and you only get a couple of seconds between the donkey conking and lowering the collective to catch the revs. I've also flown the Bell 47 and 206. They have rotor systems with far more inertia and (comparatively speaking) you seem to get about half an hour between it going quiet and needing to react.

[Teefor Gage]

Do you mean, how long have you got before you hit the ground?


Oh..............., reading on I see that you want to know how quickly you should put the lever down.

Bl##dy quickly if you have a low inertia rotor, and not so quickly, but still quite fast, if you have a high inertia rotor.

It's not so much the diameter of the rotor system, but the blade weight and diameter of the rotor - remember that famous equation E=MC2 (This site doesn't do superscript - that should be E = MC squared)

[Whirlygig]

....so in other words, you have to get the collective down at the speed of light?! :}

Cheers

Whirls

[Helipilot1982]

Wigglyamps

Its not as bad as it sounds because you should get some form of indication that the engine may quit, ie a different noise/abnormal vibration etc. You are therefore aware that it may happen and it is not a huge shock when it does and you are kind of prepared for it in a way.

[Teefor Gage]

you should get some form of indication that the engine may quit, ie a different noise/abnormal vibration etc. You are therefore aware that it may happen and it is not a huge shock when it does and you are kind of prepared for it in a way.


If that was always the case it would be wonderful. Engines can just quit cos their fed up etc. or more to the point, if their not fed and you run out of fuel.

[Teefor Gage]

No I couldn't, but it made you think

You could always try the other famous equation by Newton

E = 1/2 MV 2 or Energy = Mass x (Velocity squared) all divided by 2......

[Whirlygig]

E=Mc(squared) is true for the real world; just read it as energy=mass or kinetic energy = half mass times velocity squared.

Cheers

Whirls

[dangermouse]

E = M*R * (Omega squared) for a rotating mass>?

DM:)

[Whirlygig]

The point originally being made though was that it wasn't the diameter of the rotor blade disc but that mass that was the factor in how quickly one gets the collective down!

It is easy to make things complicated!

Cheers

Whirls





...another one with a degree in physics!!!!

[Teefor Gage]

Anyway ...... what was the original question???

PS: Bell 47's come in different shapes and sizes - for example, the G2 has a much lighter rotor system and is therefore low inertia = get lever down very quick.
The G4 model has a similar blade inertia to a 206, so you can take quite a lot more seconds lowering the lever. Some say it is possible to perform an engine off landing with the G4 (and no doubt other types too), lift into the hover (without re-instating the engine), perform a quick spot turn and then land again...... all without any noise from the engine!!

[SilsoeSid]

The formula is actually E = mc²/t

http://i52.photobucket.com/albums/g11/silsoesid/emc2.jpg

Typically 4x2²/2 = 8 seconds from when the donkey stops to when you lose control!

[Whirlygig]

'Ang on Sid, I don't eat Mars bars and never touch coffee which gives me a numerator of zero i.e. no reaction time at all. This concerns me somewhat!

Please can you let me know the additional constant factors to be applied to your formula for a consumption of Jordan's Crunchy Bars (fewer calories and no cocoa) and Tetley Tea (less caffeine).

Cheers

Whirls

[NickLappos]

The goodness of a rotor design for total power loss is determined fairly easily. It is a measure of the stored energy in the rotor as compared to the power the rotor is consuming at that instant. This term is important for auto entry, and also for the collective pitch pull at the bottom, both situations where the stored rotor energy is your life's blood. The energy ratio-ed to the power produces the time available for a given rotor rpm loss:

[Stored Energy] / [Power] = Time

[1/2 x I rotor x (omega) squared]/horsepower needed = seconds of rotor spin

Where "I rotor" is the polar moment of inertia for the rotor system (a term that is the resistance of the rotor to rotational acceleration, and which is mostly the weight, rotational rpm and radius of the blades.) Light short blades spinning slowly are bad, heavy long blades spinning fast are good.

For a "good" helicopter the calculation is about 2 seconds, for a poor rotor it is less than a second. Most Bell products have excellent numbers, the typical 206 is about 2.5 seconds, most Sikorsky's are moderate, about 1.7 seconds, and some of the very light composite systems are less than that, because the designers were told to make the blades very light, without considering this auto entry/landing as a design condition.

[212man]

Remember, also, when practising engine failures, that the fuel scheduling characteristics of both piston and turbine engines are such that simply rolling off the throttle quickly may NOT replicate a true failure! i.e. you are protected from a 'lean cut' or flame out, and so the engine RPM decays more slowly that it may in real life.

[SASless]

I just cannot resist this question.....

Nick,

Some folks suggest a slight application of aft cyclic immediately prior to...or at the same time one dumps the collective into the bargain basement priovides for much less loss of Main Rotor RPM by "loading" the rotor disc.

Have you in your idle time between creating power point presentations for the five sided wind tunnel....ever do any testing of that concept?

One has to assume a forward flight situation for this scenario I reckon.

[Matthew Parsons]

SASless, I'd say you're "unloading" the rotor, or reducing the power required to maintain rpm. If you then take that into the energy/power formula, with power reduced, time to decay will increase. So the technique does reduce the decay time.

Of course, like anything else it isn't that simple. You also want to control your speed, so once you've pitched back, you may have to pitch forward to regain speed. The pitch forward will have the opposite effect. Not a problem if you have a lot of altitude, but low level this can complicate things.

I'd just use the recommended technique for your type.

Matthew.

[ewe.lander]

.....in a Westland Scout AH 1.... 1.3 nano seconds.....:\

[NickLappos]

SASless,
Having done 1000's of engine cuts in critical flight conditions, I can say with great experience that the behavior with cyclic vastly controls the rotor decay.

A little back stick does help swap airspeed for rotor rpm, as well as help hold the nose up when the collective is rapidly dropped. If the aircraft rolls off to one side during the initial cut, it is far better to let it do so (within limits) than to use strong lateral cyclic, which consumes power and makes the rotor drop even faster.

BTW the back stick loads the rotor (increases thrust and g) but in this case that is ok, because it increases the autorotative flow a bit. The one case where it hurts is at very high speed near or at Vne while heavy and high altitude. If you are near stall, back stick makes the stall factor rise, and the rpm droop can be very big.

[bugdevheli]

Untill a rotor system is developed that gives your novice pilot about five seconds to recognise he is in deep trouble, then these light helicopters just aint safe. I do however have such a system. Bug

[Whirlygig]

Bug, does that mean you have developed an engine which coughs and splutters noisily first before it quits? :}

I have suffered an SEP engine failure (albeit a 1985 Ford Escort on the outside lane of the M25 of a Friday evening!) and can confirm that there were enough warning signs in order for me to get the indicators on and move over (relatively safely) to the hard shoulder!

It seems from previous posts that ~ 2 seconds is about right.

Cheers

Whirls

[212man]

Me too, however mine was an instantaneous failure! Overtaking at 85 mph on the M3, in a 1979 Golf diesel, when the cam belt 'slipped'. 22:1 compression ration and out of timing cam shaft made for an interesting few seconds. Of course, having managed to cross 3 lanes without power (but a large smoke screen to confuse followers) onto the hard shoulder, I was then reminded that the brake servo uses engine produced suction!

SAS, I would have replied with the bit about bunting causes Nr decay, but assumed a man of your Kaliber would have known :E

[Whirlygig]

Kaliber

Kaliber? Low-alcohol beer and SASsy-dahlin' in the same sentence? Jeez, never thought I'd see the day!

Cheers

Whirls

[outofwhack]

If I was going to have an engine failure in a helicopter I think I would be far more likely to know what was going on with an engine failure that happened quickly and preferably with a loud bang rather than one 'giving hints' as to its future demise. WHY - because its amazing how massive hints can get ignored.

True Story: I am in command of a high performance fixed wing aircraft at the threshold ready to take off on a 800m strip. Been flying these toys for 20 years or more. Power checks fine. Start roll at full power. 2 seconds later engine note changes and then recovers. Cant read any instruments due to severe vibrations. I somehow convince myself its OK and continue the take off. Result: clearing the trees by 100 feet instead of 800 feet.

My mind played tricks on me. It took me over 30 seconds to realise that something was definately wrong.
Landed without incident. Problem would not appear for engineer. Engine cleared for flight. Problem found 5 flying hours later. Fleck/flake of metal inside injector occasionally blanking off fuel flow to one cylinder = one draggy cylinder.Engine note recovery was the constant speed propellor reducing pitch to maintain revs. Realized if it had not been a severley overpowered little aeroplane in the first place [and capable of decent performance with one cylinder out] I might have hit the trees.

I wonder whether a partial engine failure like this happening in a helicopter could have similar effects on the pilot. I guess it would translate so... engine power reduces, vibrations, pilot or correlator reduces pitch to maintain revs - helicopter no doubt starts decending and wont thave enough power to hover - but are you going to realize that with the likely confusion.

Hence I just rather it go bang and I can get on with the auto.

[Fareastdriver]

Maybe Nick Lappos can clarify but I always understood that it was a certification requirement that any civilian aeroplane had to be able to cope with a two second reaction time by the pilot.

[bugdevheli]

Whirlygig. No not an engine that gives prior warning of failure. A rotor design for a VLH that will give you time to scratch your ear before lowering the lever. Bug

[kiwi chick]

Firstly, and never touch coffee a helo pilot that doesn't drink coffee? I don't understand? ;)

Secondly, A rotor design for a VLH that will give you time to scratch your ear before lowering the lever. Bug

Were this true, you will become a very rich man and save lots of lives, I am sure...

I have to concur with the 2 second average... but in other words:

long enough for your heart to skips three beats, your knickers to become very damp, and your cyclic hand to get the shakes. Oh, and possibly, if you're good enough, to blurt out F:mad:K.

[Teefor Gage]

What thoughts to start my day - at least its the start of the day here in the UK.

Firstly you talked about taking your flight tests naked on another thread (3 most important qualities.....) and now your references in the last para of your posting, above.......

Phew.... I'm off for a cold shower.......................

[NickLappos]

Fareastdriver,

The time delays after failure are varied depending on the flight regime. For the region where the sticks are continuously moving to pilot command (the hover, and the area of the HV curve below the "knee") the time delays are nil, and the only time interval after the engine cut is a 0.3 second pilot reaction time (before the collective can be lowered.)

For level flight, the delay is presumed to be 1.0 second, and the reaction time is imposed on top of that, giving 1.3 sec total from cut to collective down.

The calculation I gave below was in theoretical "seconds of total rotor stored energy" and does not precisely correlate with the figures above, except in a general way.

[SilsoeSid]

Whirlygig,

'Ang on Sid, I don't eat Mars bars and never touch coffee which gives me a numerator of zero i.e. no reaction time at all. This concerns me somewhat!
Please can you let me know the additional constant factors to be applied to your formula for a consumption of Jordan's Crunchy Bars (fewer calories and no cocoa) and Tetley Tea (less caffeine).
WG, you have no need for concern.

Simply start eating Mars Bars or in fact any chocolate bar beginning with the letter 'M'. Failing that, the formula is flexible enough to allow the 'm' to stand for mocca (coffee) and the 'c' to be Cadburys chocolate (my fave!)

Tea cannot come into the equation in itself (because it doesn't start with c or m), however because tea has generally the same caffeine content as coffee dependant on brew time, tea can replace the coffee.

As for the Jordans crunchy bars, you'll like this...

Jordans crunchy bar --- 464 Kcal/100g source (http://www.jordans-cereals.co.uk/page.asp?partid=37)
Mars Bar --------------- 452 Kcal/100g source (http://www.weightlossresources.co.uk/calories/calorie_counter/chocolate_sweets.htm)

So...if you drink strong tea and eat Jordans crunchy bars, you would in fact better off health wise with the mars bar and coffee as stated in the formula.
In conclusion, in your individual case, because of your extra caffeine and calorie intake, you are better off than most in the reaction time stakes.

:ok:
SS

[VfrpilotPB/2]

I was always taught to dump the lever PDQ or quicker, but then was shown by a very experienced and top flight instructor just how long you could take before things went to Rat Sh*t, to say the least the latter was very scary

Vfr
PR-B

[Graviman]

No not an engine that gives prior warning of failure. A rotor design for a VLH that will give you time to scratch your ear before lowering the lever.


Bug, get that to market and there may be many pilots who will be grateful. It needs to be absolutely reliable and give the pilot plenty of warning something is wrong. Near the ground hand will be on collective, so flare will be automatic.

[NickLappos]

Bug,

The drunk was searching for his keys around a light pole and a fellow stopped to help him. They crawled around for 15 minutes and then the Samaritan asked, "Precisely where did you lose the keys?" The drunk said, "about 100 yards over there." The Samaritan said, "Why are we looking over here?" The drunk said, "This is where the light is."

To build a rotor that has the inertia to allow you to sleep during the failure, you will leave one or two passengers home, and spend that payload on the rotor and rotor head. If protection from engine failure is what you seek, why specify a rotor solution? If you want engine safety, ask for safe engines!

[FayeDeck]

Sid,

I have just done a 10 hour duty and experimented by eating as much cereal and crunchy bars as possible; interspersed with about 18 gallons of tea and coffee and a load of dodgy looking things stolen from the fridge;

The deduction is that from the bog it is physically impossible to start up and thus negating the potential to require to enter auto by lowering the lever after a DEF.

Faeces sculpting aside......2 secs is a decent figure to dangle ones trilby on I recon. :E

[kiwi chick]

but then was shown by a very experienced and top flight instructor just how long you could take before things went to Rat Sh*t, to say the least the latter was very scary

:confused: :confused:

This alarms me just a little?? How did the instructor know "just how long you can take" before things got bad? :ooh:

It's not like you can push the limits until you go past the point of no return, then go "right, just a LITTLE bit quicker than THAT" - is it?

Or am i missing something? Granted I am very inexperienced so "NICE" feedback wud be welcomed!! :ok:

[VfrpilotPB/2]

K chick,

The reason for the demo was in answer to my question " how long do you actually have to dump the lever, is it really only milliseconds" as I was on a yearly check ride the FTi showed me just what was the problem at lower perscentages of rotorspeed, as already stated it was not a nice feeling.

Peter R-B

[manfromuncle]

There's no strict answer to that question, depends on lots of factors. The often-quoted 1.3 seconds for the R22 isn't strictly true, depends on airspeed/alt/power in use/weight/temp/rpm, it also depends on what else you do when you lower the lever, ie hauling the cyclic back and standing the R22 on it's tail (as long as you have at least 60kts) will restore the RPM in the green pretty sharpish.

[Graviman]

To build a rotor that has the inertia to allow you to sleep during the failure, you will leave one or two passengers home, and spend that payload on the rotor and rotor head. If protection from engine failure is what you seek, why specify a rotor solution? If you want engine safety, ask for safe engines!

Nick, rotor need not have high inertia if control system automatically does what pilot is expected to do. Not saying no more because Bug may have cash tied up in this development.

Bug, this post will self-delete if you PM me...

[bugdevheli]

OK NIck Lappos hitthe nail on the head ie massive inertia requires big hub lots of weight. which requires more power etc,etc, I have a one fifth scale working model of a rotor system that overcomes all of these problems. The question is where do i find the man that is going to make me rich and be sure he is not going to rip me off Bug

[NickLappos]

bug,
Keep thinking, it is good! Get a patent attorney, and if he likes your concept, he will take the job for a percentage of the "take".

[bugdevheli]

As my last reply seems to have dissapeared i try again. I have developed a rotor system that overcomes the problem of how to get high inertia without having to have a huge hub and heavy blades to carry the loads. Not only can i give scratch your ear time, but the rotor is far more efficient as far as tip losses are concerned. Having had a university do the becessary FDA which backs up my own data, the only unknowns are the effects in foreward flight. Now whilst the uni tell me they can give answers to this, unlike me they do not work for nothing. As they already have my one arm and a leg, i cannot hop or eat without the other. The rotor system is more efficient and yet lighter than a pair of 22 blades and hub. What i need is the man that is going to give the financial clout to make and develop a full size rotor system Bug

[Graviman]

This is the ring rotor then? Have you contacted OEMs?
I gather there is DTI government money for this type of project.

Also Sergei Sikorsky is retired, but amazingly approachable and enthusiastic. Frank Robinson would probably have similar interest, and a good starting point for this. If nothing else both will offer sound advice. In Europe it is more difficult because organisations a tend to be just that. The best you can hope for is an interesting PhD project, although this can have good long term commercial benefits.

I imagine your ring rotor will be more expensive to manufacture than a conventional system, so i would try to estimate performance benefits in terms of additional payload or range. This can be offset against the increased component cost and potentially maintenance costs.

You are talking cash, so i would present your idea as a business case. Even the most enthusiastic engineer understands it is return on investment which pays his mortgage etc...

[topendtorque]

Just wondering how quickly you have to react to the engine(s) going unexpectedly quiet and putting down the collective

Almost certainly, the answer is that if you are in doubt, you need an instructor who will remove the doubt:ok:

If it's not within a second it will be done,
there's nought else that will be fun
tet

[NickLappos]

The problem with approaching people is that you obligate them almost automatically. I suggest that you patent your invention, then enter serious talks with airframers after getting non-disclosure agreements with any that you reveal details to.

The problem airframers have is that every guy with a hot idea tells them something, then 5 years later the company develop something vaguely similar, and the guy sues. The cost to defend the technical merit and prior history of the company's work is horrendous, so company employees are schooled to return any unsolicited info unopened.

This is a common problem in Hollywood, with screenplay ideas.

If you cannot find someone to help fund patenting the concept, it is one measure of the idea's essential worth.

[purge98]

bugdevheli...is this your invention?

Does it matter if you don't drop the collective in this helicopter after an engine failure? Will it still fly?

http://www.clipaday.com/videos/how-can-this-helicopter-fly

[Perro Rojo]

If you don't know already, the slow turning tail rotor is the give away on this one. The film speed is obviously sync'd with the main rotor speed.

Great video though.

[Graviman]

Interesting to see how little rotors flex with different revolutions. You can actually see how each rotor takes on same shape as it passes through the same point in the azimuth.

Strobes are a good way to slow down rotor dynamics.

[thekite]

But so soon I digress.

In my days instructing in R22s, I never once kept the RRPM in the green range after chopping the throttle on a student, during the climb.

So the answer is gunslinger FAST! No matter what the heli. Quick pilots live. Slow ones have scary deaths-but when was it ever not so.

Which spurs me to remember a long-shelved project: develop a hydraulically- dumped collective link to cause the heli to immediately enter autorotation in the event of engine failure.

Hmmm. Perhaps I'll talk to my aeromodeler friends first.......

thekite

[ericferret]

Following the loss of the Bristow Wessex off Norfolk the AIB did a lot of work on the reaction time following a complete power loss for an aircraft of that size.

If someone has access to the accident report that should have some definitive figures.

[HeloCaptain]

"Some folks suggest a slight application of aft cyclic immediately prior to...or at the same time one dumps the collective...":hmm:


MD500D + E and EC350-B3 = absolutely true. The aft cyclic starts upward airflow through the rotor immediately and helps slow the helicopter to the best auto-rotational speed.:D

I have no R22 or R44 time, but from many of the chopped-off tail-booms in them (especially the 22) , I don't think I would be real inclined to move the cyclic aft rapidly in a Robinson.:ugh:

[Graviman]

thekite,

There are many manufacturers of reliable electric actuators now. R22 has an electric throttle govenor, so machine is almost asking for an electric collective actuator. It need only respond fast enough to keep Nr constant as aircraft alters autorotation descent (in all flight regimes). As long as servo is only strong enough to overcome friction, pilot can overpower it for flare or manouvre - in practice it could just turn off once collective has been auto auto'd.

Keep system simple to start with, so just have system drop collective when buzzer sounds then disconnect. Later incarnations could take a signal from rotor Nr needle (I imagine it is a tacho signal), to trim for a specific Nr thus accounting for any cyclic movement to convert airspeed into Nr.

Once you get this system to work a phone call to Uncle Frank might get you a licence agreement. Then you start talks about including auto cyclic control as part of R44 SAS system. ;)

BTW PM me if you want a resource in engineering community. I'm pretty busy, but interested.

[VeeAny]

EricFerret

Can't find the report but I did find this which mentions the wessex incident and a few others in the discussion about intervention delay times on page 4, the G-ASWI accident gets a mention on page 5.

http://www.flightsafety.org/hs/hs_mar_apr99.pdf#page=5

V.

[Graviman]

Folks routinely operating below HV curve will likely be grateful when Automatic Autorotation Entry Device is a standard fit...

Use RH mouse button to save or open linked PDF file:

http://www.systemstech.com/component/option,com_docman/task,doc_download/gid,15/Itemid,72/

[thekite]

Great feed back.

Stanley Hiller Igor Sikorsky and Larr Bell should have had this conversation about 1947!

The certain death of a slow pilot who does NOT get the collective down after engine failure in the climb, at gunslinger speed, is the equivalent of a Cherokee that suffers wing spar failure under the same circumstances.

Would the FAA or any other regulator certify such a deathtrap?

I was wrong of course to suggest a hydraulic linkage, much too slow. This came from an idea when I thought that Frank would fit a propeller - style governor to regulate RRPM.

The answer must be electronic, possibly a solenoid that collapses the linkage, along with a sharpish cyclic flare, maybe even an ignition cutout to resolve all doubt.

thekite

[500e]

If you are going to use electronics to lower \ collapse collective the same unit could a. be sampling eng rpm and rotor rpm,
b. After eng cut, rotor rpm could be kept in green by same govener allowing pilot to concentrate on landing site and flair.:E ahh well back to reality I suppose

[Graviman]

500e, the beauty is that all these sensors are already present in all helicopters. You really can design a retrofit system.

thekite, agreed it's nuts to put this extra workload on the pilot in an emergency. For training system could just be turned off, like throttle govenor. Best of all below HV curve system will put you into auto before you realise there was a problem. A good pilot would effectively follow through on the collective.

The assumption is that in cruise pilot will be concentrating on cyclic, and near ground will be concentrating on collective. This means that by having the system weakly try to maintain Nr then in cruise pilot can pull back on cyclic to maintain height, and near ground can override collective to flare.

Not conviced about engine cutout though. A better system would be that AAED only becomes active if engine fails to meet demand, so that Nr droop occurs. This means pilot may be able to tease another hundred metres out of a dying engine to make that forrest clearing. The on/off alarm could be supplimented by a "engine failing to meet demand" warning. AAED may then remain inactive by pilot lowering collective.

A good system keeps the options open. ;)

[topendtorque]

You had better have a radalt limit switch variably interconnected to the relative airspeed on it as well.

The very last thing that one needs when cruising at any speed anywhere below 300'AGL is have some gremlin slam the collective down for you.:{

[thekite]

Yes we have a good train of thought about keeping that sucker going for a few seconds longer to make the clearing...

With existing piston engines, there is no advantage. Lycoming engines will instantly shutdown and the overunning clutch will cut it loose.

But with turbines, there could be an advantage. Allison 250s, (sorry Rolls Royce...) are damn difficult to kill. I know of a geologist who used an axe to chop the fuel lines on a JetRanger after a crash, with all the geos out, but the pilot still unconscious in the churning wreckage. (all those years at university....!)

So then why cut the engine out. You just might make that clearing. Right now my shoulder aches, as a result of that day 12 years ago when I hit the top of the treeeeee But I digress.

Unlike a piston engine, a turbine will hang damn well in there, if the fuel is there. And even though we have gone into AutoDump ( what was that great acronim; AAED?), maybe we could just keep it delivering a few seconds longer. And it just might save your life.

Future piston engines? Frankly I doubt it. They are still going to quit when they quit.

But with turbines, even though we have just entered autodump or AAED, if we have the option of milking up a little collective, and even though the revs are so low we can't look the tacho in the eye.. (you guys take over. My shoulder hurts. You have control.)

thekite

[thekite]

You are right of course. But we would have to have a means of overiding all of this stuff. Principle 1. the pilot in command must remain the Pilot in Command must always remain the Pilot in Command!! ( thank you Mae West)

The new trick for we instructural types would be to teach when to
intervene with the machine and when to stay the **** away! And just fly the new regime.

(On another note, I believe that you and I may share a postcode. Show me yours and I'll show your mine)

thekite

[FlyGooseFly!]

How long have you got
Untill a rotor system is developed that gives your novice pilot about five seconds to recognise he is in deep trouble, then these light helicopters just aint safe. I do however have such a system. Bug

After about my first thirty minutes PIC in an R22, my instructor clicked off the auto throttle and said - land there - which we did some few seconds later. Now I'm not blowing my own trumpet to say that I'm the best student ever but it did seem so very easy to keep control ( given good weather and vis ) the instructor took control just on flare for a great grass runout. So. I said, full of glowing confidence - it must be difficult to actually crash one of these then ? Oh I wouldn't say that - he said - people are finding new ways every day!

[Graviman]

Hehehe, FGF. Good story. I wear a seat belt when i drive, but not because i am intending to crash. It only takes one saved life to justify AAED...

TET, failure modes are a good point. By using the Rotor Nr, once engine N1 has drooped, the collective will gently trim as required to maintain ~100% Nr. I suggest an "orange warning" for N1 dropping to say 95%, and a "red warning" for N1 dropping to 90%. Near ground at speed pilot should be on collective to quickly overide system. Cyclic can be pulled back as normal and collective will trim to maintain 100% Nr, so some height gain may be possible. It can always be turned off as a final measure.


thekite, it is also possible pilot attempts to restart piston engine after lining up. No need to force landing for a bubble in the fuel line.

Some thought needs to go into "orange" and "red" warnings. Orange could be an intermittent alarm, with red continous. This also quickly informs pilot whether there is anything left in the tap. Also a Failure Mode Effect Analysis will reveal whether system malfunction can cause unrequested autorotation entry. The trick is to keep the design simple, using two circuits which must agree before any action is taken. Ultimately servo is weak enough to be overpowered for flare, or system can be turned off.

[NickLappos]

I guess its time to wheel out my favorite rant:

We practice what we can, often, then we have accidents caused by entirely different things.

We perseverate about autorotations and engine failures, until we are blue in the face (I once saw a US Navy crew do 8 power recovery autos in a row in a 3 engined CH-53E!!), we chomp at the bit for a system to dump the collective, we ask for rotors so heavy they yawn once or twice after the engine quits before that start to lose rpm. We demand hard Cat A machines where one engine is a spare for the other, so that every normal maneuver can be done with either. We beg for helos that carry half the passenger load, and go half the distance, but that can survive our imagined worst nightmare.

We imagine that nightmare because we are so much like Pavlov's dogs that we actually salivate when someone mentions the several accident scenarios that we have been practicing since we were wet behind the ears. WE KNOW thats what causes accidents, because THAT's what we have been practicing all those years!! Would our trusty instructor lie to us? No! Could the flying handbooks be wrong? NO! Quick, get a bigger set of engines, get a heavier rotor, buy a collective with a big spring so it can drop itself when the engine quits.

Of course, if we invest in EVERY wet dream mentioned in this thread, our accident rate would not go down more than a few percent, perhaps not at all! Why?

Because, quietly, the REAL accident causes sit and laugh at the trained pilots who jump up and down for more autos and auto protection systems. The real accidents wait...

Answer THESE questions and THEN ask for improvements where they are needed:

1) When was the last time you and your instructor practiced preventing CFIT?

2) When was the last time you and your instructor practiced skud running and then inadvertent IFR recovery (to a full instrument landing?)

3) When was the last time you purposely flew into a pilot error situation to practice the recognition/recovery techniques?

4) When did your instructor last tell you, "Oops! You have 10 minutes of fuel left, what do you do?" and then watched as you solved the situation?

5) Can you list the exact accident causes for helicopters, from most prevalent to least, and tell how you KNOW you won't have each, because.....?

[[email protected]]

To add to that Nick - once all the sooper-dooper safety systems were installed in your pilot-proof helicopter, how many accidents would be caused by system failure (lever lowered at inappropriate moment due to slight Nr decrease following mild overpitching approaching a high hover for example).

In many accidents where failure to enter auto properly was the main factor, it is often a pilot's procedural error (running out of fuel/no carbheat etc) or pilot's lack of current practise. If you want to be a pilot get your chequebook out - if you want to be a good pilot stay current. Continuity of flying skills is vital, especially in the less experienced.

[Graviman]

Absolutely i would not pretend to be a real pilot, nor have i reviewed accident statistic data, but this system might just give a couple of extra seconds. There may only ever be one pilot in the future who benefits, but isn't that enough?

I'm not proposing a system which spring drives collective to the floor, forcing helicopter into a death dive. The system i am proposing does absolutely no more than the pilot would, by maintaining ~100% Nr while pilot takes stock. At the worst it would do absolutely nothing, which is where the state of the art is now.

Agreed that the ideal is a radioaltimeter input, with auto flaring, but that adds additional complexity. This is not Comanche style FBW.

[TopBunk]

Folks, reading through this thread as a mere 747 pilot scares me sh*tless and reminds me why I chose the route I did!

You are heroes for risking flying these lethal machines that patently should never have been certified in the first place .... maybe I'll change that to say it is you that should be certified.

No wonder they don't make a long haul helicopter, you'd be lucky to find a sub 10 second reaction time in the cruise after 6 hours:eek:

[Bravo73]

Blah blah blah

Yawn. Ignorance really is bliss, isn't it TopBunk? :rolleyes:

[topendtorque]

I sense and share your esaperation Nick and note that you have often exasperated about those who CFIT.

With respect, there is also a problem as highlighted by your comment (3) , where Uncontrolled Flight into Terrain (or something solid) is also quite a problem.

That at least should be rectified in part with adherence to some decent preventative training.

Re your quote below;

our accident rate would not go down more than a few percent


Small percentage rates, is what drives amongst other things, successful bank balances, good copy in accident reports and jet engines.

Attention to detail is what drives the difference in the percentages in the right direction.

Never give up on presenting the detail if we wish to strive for better equipped pilots in the community.
cheers tet

[diethelm]

The main cause of accidents is failure of the apparatus between the ears and if you want real improvement in statistics, improve the decision making process of that device.