Is a second or so enough?

[bugdevheli]

How many people could make a life or death decision in just over a second, if that decision had to be made without prior warning, and at a time of great stress or concentration. If the answer is "only a few" then does one assume that pilots of light helicopters are superhumans or are they convinced that the training they have received is enough to cover such an emergency. How does one train for the unexpected happening at the worst possible moment. This thought occured to me today whilst up a ladder swinging a sledgehammer. If i miss the bricks should I hang onto the hammer or grab the ladders.? As it happens I managed neither. Lost the hammer and fell on my ass. I am normally competent with both hammers and ladders, but had not received training on this particular emergency. I blamed the high inertia hammer.

[Thud_and_Blunder]

Sounds to me like you'd planned ahead - a nice comfortable landing on a handy donkey has to be preferable to landing on your arfe...

[chopperpilot47]

In another thread on this forum is the quoted statistic that 21% of all Robinson accidents result in a fatality. Makes you think!

Regards,

Chopperpilot47

[NickLappos]

It is a devilish question, one we make each time we develop and certify a helicopter, bugdevheli.

The training has to be automatic for power loss in a single engine helo, with an instinctive connection between the rotor rpm and the collective. There is no decision, no cogniton (thinking) involved if it is to be successful.

Back when I was very wet behind the ears, my instructor covered up the rotor tach and made me fly most of a training session, just to prove how the sound of the engine and the beat of the rotor become part of your subconscious control loop.

If you were to use the 1 second comparison when someone throws a rock at your head, you'd get pranged every time. Ditto with the flame of a hot stove. It not only can be learned, it is the entry point for allowing a solo flight, IMHO!

[Dave_Jackson]

Perhaps for recreational helicopters, which the pilot flies infrequently, the craft should be equipped with a rotor governor. This type of governor is a RRPM - Pitch coupling. As the rotor looses speed, the pitch of the rotor decreases. Its operates differently than the common engine governor, which is a RRPM - Torque coupling.
A rotor governor requires action by the pilot to STOP the craft from going into autorotation.


Incidentally, a rotor governor was included in the world's first production helicopter, the Flettner FL-282. In fact, the FL-282 was the first recorded helicopter to enter and exit autorotation.

One of two remaining helicopters was taken to the US after the war, for evaluation.
The Prewitt Aircraft Co's. technical report ATI #20283 on the flight tests of the FL-282 states that the rotor governor was found to be very effective. It used a fly-ball rotor pitch governor. There was 10 % of RRPM adjustment. There is a specific report on it ~ Prewitt Aircraft Report N0. 5-130-2

[chopperpilot47]

Nick is absolutely right. Until our students can properly enter autorotation when we unexpectely chop the throttle we don't send them solo. They also have to pull off a decent full touchdown auto. Of course, in the Bell 47 they have a reasonable amount of time to recognise and enter the auto.

Regards,

Chopperpilot47

[Whirlybird]

Yes, but....

An "unexpected" throttle chop in training is not actually unexpected. Students know it will happen, maybe not when, but sometime. It's very different from, say, flying along on a lovely sunny day, looking at the view, talking to a passenger, talking to ATC, and suddenly it all goes quiet, that horn goes off, and the helicopter yaws.

Or, I would think it is; I don't speak from experience. Because we no longer have throttle chops in R22s as part of the PPL course (although my gungho instructor did pull some on me). But I was given one on my FI course, with prior warning at the beginning of the lesson, but not close to it actually happening. I'd swear I got that lever down instantly, but the RRPM still went down to 90%. Now, 90% is recoverable, and I'm on the verge of being an old fart :{ and maybe my reactions aren't quite as fast as the wet-behind-the-ears daddy-paid-for-licence young PPLs, but...well, it makes you wonder. Or it makes me wonder. And I simply don't know the answer. :confused:

[CRAN]

IMHO,

One second is nowhere near enough.

If low inertia rotors were a good idea then:

(a) People would not continue to die following engine stoppages
(b) The R-22 wouldn't have more loss of main rotor control incidents than other teetering types
(c) We wouldn't require SFAR-73

And something else...that one second people talk about for the R22 is NOT one second for the typical high pitch settings used, thats significantly less.

Please Note:
I am not a Robinson basher, I fly both the R22 and R44 and think they are mechanically reliable helicopters. I don't quite believe what Frank Robinson says about never foreseeing the market for training helicopter but do accept it. However, knowing how little weight would have to be added to the R22 rotor system to make it a high inertia system, I am very dissappointed that Frank hasn't spend a few months over the past 25 years sorting out this fundamental design fault with his most popular product.

[ShyTorque]

The pre-conceived idea that a particular emergency is about to occur does alter a pilot's reaction. I've seen this many times whilst instructing in the simulator.

A couple of examples. Whilst giving students a series of double engine failures to teach entry to autorotation on a twin (Puma), I always gave them a SINGLE engine failure at some stage. Many pilots were surprised to be shown in the replay that they had shut down a perfectly serviceable turbine. The confusion occurs when autorotation is entered and the good engine backs off to idle. Made students think about checking T's and P's properly.

Similarly, recognition and successful recovery to autorotation from a tail rotor drive shaft failure was shown to be MUCH more difficult if the pilot didn't get a hint or a warning such as vibration. Once a student had the basic skills, I used to give them an unannounced one to deal with. It proved the point that the aircraft could be recovered from some "interesting" extreme situations. I think this is particularly important as diagnosis of this particular malfunction does take a short but finite time.

The video of a yellow Wessex that went into a Welsh reservoir a few years a go is a good example of how such an emergency might occur for real.

[Shawn Coyle]

Effective training appears to be the key.
If you don't know how your helicopter will react to an engine failure at any stage of flight, and what and how you are going to react, perhaps you should think about changing jobs.
I realize this can breed a bit of paranoia, but it's better to be paranoid than surprised the wrong way.
In one accident I looked into, I could visualize how surprised an Alouette pilot was when the engine sputtered and stopped - he had 7,000 hours on a type with an incredibly reliable engine, yet the engine quit and from all accounts he wasn't prepared for it in terms of the route of flight, etc.
I'm very surprised that there isn't some way to demonstrate effectively to R-22 students how they have to be ready for an engine failure at any time.
One second is enough if you're ready for it, but for the three engine failures I've had, I wasn't prepared for it - fortunately the cost so far has been only minimal airframe damage and wounded pride.

[S76Heavy]

One second is enough if you're ready for it, but for the three engine failures I've had, I wasn't prepared for it - fortunately the cost so far has been only minimal airframe damage and wounded pride.Doesn't this support the case for a technical solution to increase reaction times? We're all human and after years of flying without engine failures, we're no longer really ready for it (although we still think we are). Inevitably, some form of complacency will set in, I suppose.

[Shawn Coyle]

s76Heavy
It would be nice to be able to increase the reaction times. I don't see how it could be done unless you come up with some warning system that says - your engine is not healthy and is about to fail. Vibration sensors? Maybe. Carb icing happening? Bad ju-ju sensor? Hmmm.
Something should be possible - perhaps a rate of decay of engine RPM vs. collective position or throttle position or something. Someone somewhere has some engineering data on what the pre-cursors to engine failure in piston engines are - perhaps they can help.

[pa42]

Clearly the BadJuJu sensor would be paramount.

But even better: do there not exist in the test-pilot caverns some inexpensive forms of vibration monitors? Hi-medium-low frequency sensors for same? A scale precision calibrated in sophisticated units of "acceptable-normal" and "panic-bailout"?

After all, we do equivalent accuracy with G-meters on aerobatic airplanes . . . why not a helicopter shaking-apart measure?

Crowded for panel space? Usurp the IAS meter real estate below 50 knots, the 0-40 k range is useless anyway, as witness your own Bell 206 mast-top spinning sensor!

[Lu Zuckerman]

To: S76Heavy

Doesn't this support the case for a technical solution to increase reaction times? We're all human and after years of flying without engine failures, we're no longer really ready for it (although we still think we are). Inevitably, some form of complacency will set in, I suppose.

Many years ago the Hydraulics design group at Sikorsky undertook the design of a device that would provide that one-second reaction time without any input from the pilot.

The device was connected to the collective stick. It was cylindrical in shape and inside of the cylinder was a piston. One side of the piston was connected to the servo hydraulic system and the other side of the piston had a spring. The operating concept had the hydraulic system pressurize the piston compressing the spring. The spring was then in the cocked position and the trigger mechanism that released the spring was connected to the engine oil pressure system. The instant the oil pressure dropped the spring would be released forcing the collective stick down establishing autorotation.

There was one minor problem. In order to cock the piston (compressed spring) the hydraulic pressure had to raise the collective stick. The pressure would increase from zero to about 300 to 400 PSI raising the piston but the servo pump was driven from the transmission and at the same time the pressure rose to the point of cocking the cylinder the blades were rotating about 100 RPM. This significant increase in pitch would result in blade sailing and eventual stall out causing the blades to impact the tail cone.

And, another hare brained scheme bit the dust.


:E :E

[Helinut]

Practice and currency is a real must. I used to work as a training captain at a Jetbox outfit and at the same time also doing PPL training on the R22.

The AOC operator used a variety of freelance pilots. Most of the guys had oodles of experience : offshore and/or military. Most were current somewhere else : often on airliners or twin engine IFR big helos.

It wasn't my practice to do throttle chops, but "voice actuated" practice engine failures, with my hand following to deal with the twist grip. The difference between the two groups was ofetn noticeable. It was common for the experienced guys on the B206 to be slow to respond to the command and hesitant in execution. PPL students during training (who say had gone solo and were flying regularly) were fairly prompt. I guess I would not have sent them solo, if they were not.
[I should also say that everyone improved by the end of the practice which is what it is for].

The worst people were a group of PPL aircraft owners. This was before JAR-FCL, so once a PPL had his licence he never needed to fly with an instructor ever again - not possible now, and IMHO one of the (few) benefits of JAR FCL. Essentially some of this group could even be scared of doing a slow-time autorotation.

If my memory serves me, the AAIB did a study many years ago when an offshore hele crashed due to engine failure and subsequent low RRPM. They got a set of sim sessions to add an unannounced double engne failure and time the reaction time. I recall the times were pretty slow and most would not have responded in time.

These days I fly solely twin engine heles, and I can't instruct (sadly). I always used to feel sorry for line pilots struggling to keep REALLY current with just a 6 month base check and not much other oportunity to practice - now I am he!

I am contemplating doing some single engine flying in the near future, and I will be making sure that I get a very thorough workout before I am finished.

A bit of risk management is surely the practical solution (pending the arrival of the doom sensometer). In a single (and especially one with a low interia system) currency is key. At certain places I flew from, when I was hours building, autos were banned without an instructor. Clearly, this reduced the risk of problems during solo practice autos! However, I wasn't happy in that situation at all and avoided it. If any single engine pilot gets to the point where they are reluctant to do an auto, they need to get out there and in practce again with an instructor. A little game I was taught was to fly along and enter auto at the start of the next radio transmission.

When flying a single never ever let yourself be distracted (hand off the lever etc.) while in the climb or anywhere where MR pitch would give you a more rapid decline in RRPM if the donk stops. You then do the best that you can to manage the risk.

[Dave_Jackson]

In threads about entry into autorotation and the time available for the pilot to react, the subjects of low rotor inertia and the Robinson R-22 inevitably come up

Lu mentioned on an earlier thread; " It has been brought to my attention that on the R-44 the pitch horn extends beyond the cone hinge by approximately 28mm.". I believe that the design of the R-44 hub and the R-22 are basically the same. An exception to this similarity is that the pitch horn on the R-22 is inline with the cone hinge. This raises an interesting subject for consideration.

When the pitch horn is on the leading edge of the blade and it is beyond the coning hinge, the rotor has a Pitch-Cone coupling. This coupling causes the pitch angle to reduce as the coning angle increases. One cause for an increase in the coning angle is a reduction in rotor speed. This Pitch-Cone coupling characteristic serves as a type of rotor speed governor, since by removing pitch it reduces the rate at which the rotor looses speed.

The implication is that, all things being equal, the pilot should have more time to react in an R-44 than in a R-22. Might this be true?


Related info on the Groen gyroplane for anyone interested (http://www.synchrolite.com/B185.html#Groen)

[Groen added]

[NickLappos]

Dave,
That coupling (also called delta 3) is very much a ride quality and rotor thrust stability improvement. It basically flattens out the rotor's thrust changes as affected by gusts. This also makes the aircraft seem more dynamically stable in turbulence. It does cause rotor speed increases when the plot commands thrust changes with cyclic, as well. It would have a secondary effect of reducing collective as the rotor coned, but to cone the rpm would have to decay first. I'll bet the effect is secondary.

At the bottom of an auto, the delta 3 is a bit harmful, because it slightly reduces the thrust in the flare, making the pilot need to flare more quickly and to a higher nose angle to extract the energy to stop the descent. This effect is fairly small, however, so it should not dominate.

The rotor decay rate at auto entry is almost all due to the rotor inertia (stored energy) as compared to the power being drawn at the engine cut. The allowable rotor droop is almost entirely due to the stall margin of the rotor at the cut point (the aerodynamic blade loading margin). With low inertia the rotor rpm decays rapidly, because of low stored energy. It could be however that the rotor retains effective control at low rpm though, so that large rotor rpm droops are acceptable.

What is the min rotor rpm in the R-22 and R-44? What are the normal rpm's? What s the weight of the rotor blade? With this, I can try to estimate the residual energy (I am sure you can, too, Dave!)

[Lu Zuckerman]

To: Dave Jackson


This coupling causes the pitch angle to reduce as the coning angle increases.

If the pitch horn extends beyond the cone hinge when the blades cone pitch will be added to the blades not removed. This is not such a bad thing. However when the pilot enters into autorotation and he moves the collective to the full down position the blades are still coned and the pitch can not return to the full down basic pitch setting and this will effect the autorotation characteristics.

If the effect is great enough the pilot will report this to the mechanic and he in turn will adjust the pitch links taking the blades below the basic rigged neutral pitch setting.

This is my basic argument when Frank Robinson stated that he had considered incorporating a 90-degree pitch horn. If he had done so the helicopter would be uncontrollable. Extending the pitch horn 1” or so beyond the cone hinge will not make the helicopter uncontrollable but it will effect the autorotation characteristics.

The entire rigging procedure on the Robinson helicopters is contrary to the rigging procedure on every other helicopter and can lead to some very interesting problems for the mechanics.


:E :E

[NickLappos]

Lu,
Any delta 3 effects can be easily worked out when the engineers perform the rigging that then goes into the maintenance manual. Bottom pitch stop on most helos is determined by the auto rpm, in any case.

In other words, no problemo.

Regarding 90 degree pitch horns, the controls are mixed to account for the phase lag, if the horn geometry is changed, all you have to do is re-mix the mechanical controls to make the helo fly right. We have been thru this perhaps 50 times, the way the aircraft handles is NOT affected by the head geometry, as long as the controls are properly mixed. And the Robbie has properly mixed controls.

That 18 degree horse died a long time ago, Lu.

[Steve76]

They better rethink the Delta 3 application for the R44 if they think that it helps to make it more stable in turbulence...
Daewoo of the sky :rolleyes:

So, if we had a "automatic autorotation entry device" coupled to the RRPM, that would mean increased exposure to damage when the RRPM decays in a hovering auto. Generally you don't want to drop the collective too much when you are in a 6ft hover and the engine quits.
I would rather bleed off all the RRPM rolling to the right and fall down the hill, than settle into my passangers as they perform a hover exit from the left of the aircraft. RRPM use is the discretion of the pilot.

Surely there are other good reasons that manufacturers have not installed these. Myself, I was trained to respond to all problems by heading for the ground. Auto was the quickest and generally it puts you into a place where you can quickly access what is happening. I once met a small whirlwind in a B47 and the resultant was ...ummm.... interesting. Needless to say, when we were upright again, I had to roll on the throttle and recover from an induced autorotation. Instinct....
Happened much faster than 1 second and the training to drop pitch and then access the problem (height specific of course) was done without cognitive thought. Just one of a few occurances where the reactions are faster than the thinking.
Many would say that is not uncommon for me thou....hahaha :p

Still I am amazed, as Shawn was, with the experienced pilots that you go for a training flight with who have no preconcieved idea about what they are going to do in an emergency.
Every rig departure, of which there were 35 a day, required you to think about each stage of the next 20secs and what you would do if the engine quit here, there and down there. It took a lot of discipline to focus because the engine very rarely quit. But we did have a lot of other interesting caution lights which encouraged forethought about your immediate actions.

When your life span can be measured in seconds, you better have a plan.

...and having seen the number of wheelchair bound people who have fallen off ladders and got a free helo ride....
Budgie, take my advice and stay off the ladder.

[Pat Malone]

Interestingly, in recent times we've been putting some effort into stressing to R22 students the fact that autorotation should not be the automatic reaction to any suspected problem.

This is because we've had a number of fatal accidents in the UK involving pilots who entered autorotation because of a red light, or other perceived problem, and who then screwed up the auto one way or another - let the revs go to hell or ran into the side of a house. (This should also be taken into account when you consider why one in five R22 accidents is fatal. You're not dealing with high-time hotshots here).

The story now is - nose flicks left, engine failure, lever down. Nose flicks right, tail rotor failure, lever down. Anything else and you've got time to think about it before you commit.

As to R22 inertia, Tim Tucker waited an electronically-measured 2.4 seconds after throttle chop before beginning to lower the lever during one test, described to me as "in cruise flight." (Don't try this at home). The 1.1 seconds often quoted as the time you have available to rotor stall is if you seek to maintain height by raising the lever. The three main causes of low RPM rotor stalls are overpitching, rolling the throttle the wrong way (mostly in the pre-governor days) and gripping the throttle so hard that the governor was unable to turn it.

[Lu Zuckerman]

To: NickLappos

On a typical Sikorsky, Bell, Aerospatiale and most other helicopters they have a rigged phase angle of 90-degrees. On most if not al of these helicopters the actual phase angle is less than 90-degrees (Phase angle shift). On a Robinson the rigged phase angle is 72-degrees with the assumption there is no if not a minimal shift in this phase angle.

No amount of modification of control input can compensate for a 90-degree pitch horn on a Robinson helicopter. The control input on the Robinson is identical to a two-blade system on a Bell. With forward cyclic the swashplate tips down over the nose and with left cyclic the swashplate will tip down over the left lateral axis. The opposite is true for opposite control inputs. On the Bell the pitch horn leads the blade by 90-degrees. When setting the forward pitch range on the Bell the blades are disposed over the lateral axis. In setting the lateral pitch ranges the blades are disposed over the longitudinal axis.

On the Robinson when setting the forward cyclic pitch settings the blade is disposed 18-degrees ahead of the lateral axis. In setting the lateral range the blades are disposed 18-degrees ahead of the longitudinal axis.

Now let’s discuss flapping on the Robinson. Flapping in this case is coning about the cone hinge.
On the R-22 with no pitch in the blades the pitch horn connect point with the pitch link is on or about coincident with the cone hinge so if a blade is raised from this static point there is no pitch flap coupling. However when collective pitch is increased the pitch horn will rise above the cone hinge so if the blade is moved about the cone hinge there will be pitch flap coupling with a decrease in pitch with up flap and an increase in pitch with down flap. This is normal.

However if you have a pitch horn that extends beyond the cone hinge you will have control problems. Using the above example with a 90-degree pitch horn if you raise the blade about the cone hinge with no pitch in the blades you will get an increase in pitch (on the R-22 there is no change in pitch. When collective is added and the blades cone there would be a significant increase in pitch over that which was input by the pilot. The kinematics of the blades in flight are beyond me but I do believe that with any flapping of the blades about the cone hinges the rotor would respond in a way that either increases the pilot input or acts in opposition to the pilot input.

The R-44 does not have a 90-degree pitch horn but it does extend beyond the cone hinge. Although the problems would not be as severe I believe that under certain conditions (autorotation) there could be a problem.

On most helicopters blade pitch settings are made and then the adjustable stops are set to limit any movement beyond that point. On the Robinson they have fixed stops and the blades are set to that stop. All pitch settings are set with the cyclic in the neutral position and the collective full down. Since any movement from the neutral position to the forward stop would be equal to the same movement to the aft stop. From that you might assume that the pitch settings for forward and aft cyclic would be the same but, they are not.

Both blades are set with the cyclic against the forward stop. Then the cyclic is moved the aft stop and the blade pitch is set to the aft settings (which are different). In setting the aft pitch point it is necessary to adjust the pitch links which destroys the setting for forward cyclic. The mechanic is then told to recheck the forward pitch setting which are now changed. At or from this point the mechanic is left to ponder what he must do as the maintenance manual is moot from this point onward. The lateral settings are the same.

In some cases it is necessary to make adjustments on the pitch-input rods to the swashplate (after having neutralized the swashplate). These adjustments can cause a binding on the swashplate monoball. The tail rotor settings are just as confusing.

Nick, I have a question. Put yourself in Frank Robinson’s place. You design a rotorhead and then construct a helicopter around it. The rotorhead is different in that it can flap about a teeter bearing and it an also flap about cone hinges. Good design says that the pitch horn can't extend beyond the cone hinge so that the helicopter has a rig angle of 72-degrees. Now design a blade that will respond in 72-degrees where all other helicopters have a rigged phase angle of 90-degrees and their blades respond accordingly.


:E :E

[Thud_and_Blunder]

Hands up all those who saw that coming? One, 2, 3 - er, lots...:rolleyes:

[Eyesout]

Hi all

If one was to experiance engine failure in the R22 whilst flying at sensible speeds ( >60knts), would immediately flaring the aircraft help to reduce the rate of RRPM decay or even stop the decay untill the lever was down? I only ask because your hand may not be on the collective the moment the engine quits.

I'm about to take my PPL flight test, I'm a little worried about R22 safety in the event of power failure.

Regards Eyesout.

[Dave_Jackson]

Whoops!

Nick, what you say is informative and makes sense. Unfortunately, we have a problem. :uhoh:


Lu said, "You got it wrong. If the pitch horn extends beyond the cone hinge when the blades cone pitch will be added to the blades not removed.

"Lu, You got it right. I assumed (naughty, naughty) that your " It has been brought to my attention that on the R-44 the pitch horn extends beyond the cone hinge by approximately 28mm.". meant that the pitch link was outboard of the coning hinge. Burkhard Domke's picture (http://www.b-domke.de/AviationImages/Rotorhead.html ) confirms that the pitch link is actually inboard.

This means that on the R-44, upward coning adds pitch and upward teetering removes pitch. Therefore, much of what Lu says makes sense. In addition, Steve76's comment " They better rethink the Delta 3 application for the R44 if they think that it helps to make it more stable in turbulence..." also appears to support this position

Frank R. must have had his reasons for moving the pitch link inboard of the coning hinge but it appears to be counterintuitive to the thinking of those on this forum, and Chuck Beaty. This sure make Lu's concerns a lot more interesting.

:confused: :confused: :confused:

[Thomas coupling]

Eyesout: Flaring would conserve the rate of decay of Nr it might even increase the Nr if you're fast enough.
I never let go of the cyclic, mainly because my FLM tells me that if I have a SAS runaway and the cyclic is 'unattended' I could lose 400'+ within a couple of seconds!
I rarely let go of the collective - possibly because of my background as a mil instructor and protecting myself from a clumsy student pilot. Mainly though - there is a big fat steel rod attaching the Nr gauge/rotors and collective. Ask the engineers to point it out. You really should be ultra close to that collective most of the time.
What response time do they give R22 drivers for rotor recovery: 1.3 seconds, is it?:sad:

[pa42]

Eyesout: widespread standard doctrine, so far as I've heard, simultaneous dump-and-flare. Cheap insurance against being too slow with dumping collective.

This was the subject of a recent safety article in one of the mainline helicopter magazines, I'll look for the reference but probably somebody else will beat me to posting it.

[Pat Malone]

Eyesout:
Flare is absolutely vital.
I've had demonstrated in an R22 a throttle roll-off at 90kt followed by a steadily increasing flare which kept the RRPM from decaying for seven seconds before the lever had to be lowered.

[Hughes500]

Pat

Flaring for 7 seconds is all very well but you will be slowing down ! In my experience of students and low houred pilots they tend to over control, which means too harsh a flare and you could easily go below best auto speed and then you have an equaly big problem. Namely to recover speed you have to push the disc forward ( off load ) this will futher slow down the blades, until speed of ac will slowly pick rrpm back up. If you do not have enough height here you and mother earth will meet up. You seem to want to give the impression that the R22 is very good at this because Tim Tucker can do X Y and Z, he bloody well should be able to, the average 50 hour pilot cannot. Of all helicopters the R22 should be treated with the upmost caution by novice pilots, it never ceases to amaze me the number of pilots who pay scant disregard of keeping your hand on the lever.
Please do not give the impression that the R22 is very good in novice hands - it ain't !

[Shawn Coyle]

There is no problem going below best auto airspeed, especially if it means keeping the rotor RPM in the green range. Autorotations can be done at a great variety of airspeeds, including if necessary zero airspeed (not recommended, but far better to be at zero airspeed with lots of rotor RPM than to be at airspeed with no or low rotor RPM).
Pushing forward on the cyclic automatically following an engine failure was the subject of a superb article in one of the newer magazines recently - basically - don't do it.
There are people who do autorotations to holes in the jungle and then drop at zero airspeed into the hole and survive the landing at the bottom (they even train for this). So there are lots of ways to do this, but the key is that you have to have rotor RPM - not necessarily airspeed.

[Hughes500]

Shawn

I agree wholeheartly about rrpm, but in any helicopter you need airspeed so you have something to flare with at the bottom, espically an R22
A question to you if you owned a brand new helicopter would you sit at the duals and ask a low time pilot to do an engine off landing with 20 kt airspeed or 60 kts airspeed. If the answer is the former you are very brave and risk bending the ac and yourself if there is the slightest missjudgement.
My point is that yes rrpm is life down to close to the ground, but airspeed so you can flare will probably mean a less experienced pilot will walk away !

[Shawn Coyle]

I am becoming more and more convinced that one of the easiest autorotations to do is the 'constant attitude, no flare' autorotation.
This presupposes that you really don't care where it is you land - all you want to do is walk away from the crash, so we'll leave out the "have to get to a particular spot" aspect for this discussion.
The airspeed for this type of autorotation will depend on the helicopter - probably a slower speed than will be used here would be appropriate for a Bell 47 and a higher speed than used here for a Bell 407. For the Bell 206 series, I use 40 Knots plus half the windspeed.
After turning into the wind and setting the airspeed / attitude there is nothing to do until the ground starts to rush up, which is a pretty strong cue from below about 75' AGL in wide open territory. At this point, application of collective has to wait until about 20-25' above ground when it is applied smoothly and positively.
The helicopter is in a slightly nose-up attitude so applying collective will both slow / stop the rate of descent and slow the forward speed to something that would be survivable.
A couple of demonstrations and even very low time fixed wing pilots can fly it.
But the point is, you don't need to have airspeed to survive the landing - just a way to get the rate of descent and forward speed to something survivable.
I think there is a strong case to be made to teach this technique first and when the pilot has slightly more experience to teach the use airspeed and rotor RPM to get you to a desired spot and learn how to flare, etc.

[Pat Malone]

Hughes 500:

Preserving RRPM at the moment of failure is the primary concern, and unless you're down among the bushes you can flare until she's standing on her tail, and to hell with the airspeed. Usually you can get that back, but there's no way home from a rotor stall. And of course, you've got no problem with zero-G pushovers if there's no torque.
We teach students zero-speed autorotations in a 22, and as long as you start gaining airspeed around 500 feet you'll have plenty of time and inertia for the landing flare.
As to the seven seconds, as I say, it was a demonstration. I've had a number of impressive demonstrations in the 22, some of them very silly - like backwards autorotation in actual IMC. I wouldn't do it myself, or tell a student that it's work for a novice.

[NickLappos]

Shawn,

Those constant attitude autos are great in helos with a ton of rotor inertia, but not conducive to longevity in low inertia helos, and in high disk loading ones, too. I used to teach them in Cobras, and they work well, but I wouldn't try one in an S-76 or an H-60! I'd bet a Robbie wouldn't do so well either!

[Whirlybird]

No, I wouldn't want to do a constant attitude airspeed in a Robbie. On the other hand, when I was learning, I think too much was made of this keeping your airspeed up. Unless your low hours pilot is flying a lot lower than he/she should, get that lever down and flare, and never mind the airspeed. You then have time. And if you then use altering the airspeed rather than making turns to aim for your field/spot/flat bit, you have less need to make precise height/distance judgements. So long as you get back to 60 kts before the flare, you should be OK.

Now, how much difference does landing into wind make, is what I'm still wondering? Unless the wind is really strong, could your novice fairly safely forget about it?

[ShyTorque]

A few rambling thoughts.....

If a reasonable landing area is available, one of the two prime concerns is to reduce the ROD at touchdown to a safe, survivable level. If a low airspeed is recovered too late, it can only be done by lowering the nose, which will increase the ROD and decrease the Nr.... decreasing the chances of a good landing.

A minimum height for attempting to recover airspeed should be considered. My (military) training taught me that constant attitude autorotations were a good thing to consider at night, offering the pilot a better view ahead. Flaring the aircraft sends the landing light beam skywards of course, leaving the pilot with an unlit area ahead. We were taught minimum speed autorotations (IAS off the clock) as a manoeuvre to make a field almost directly below but to recover the IAS at 600' due to effects of lowering the nose to recover airspeed / Nr. In any event, we were taught to aim for wings level and a "recovered" airspeed by a minimum of 300' agl if possible.

Whirly asked:

Unless the wind is really strong, could your novice fairly safely forget about it?

In the real case of engine failure, the second prime concern is the likelihood of a gatepost between the legs :uhoh: . A 5 knot tailwind is 10 knots worse than a 5 kt headwind when it comes to considering the possibility of impending forward impact......

I think a mental picture of the wind direction is vital at all times when flying a single.

[The Rotordog]

Whirlybird asked:Now, how much difference does landing into wind make, is what I'm still wondering? Unless the wind is really strong, could your novice fairly safely forget about it?I guess the answer to that depends on two things: what kind of surface you have underneath you; and whether you don't care about damaging the aircraft.

Check this out: http://www.ntsb.gov/ntsb/brief.asp?ev_id=20001205X00168&key=1

The pilot was delivering a brand-new EC-120 from Grand Prairie to Alaska. He had just left the factory and was cruising along at 500 feet agl with the wind at his back (probably enjoying the high groundspeed) when he developed a power problem. I guess Eurocopter didn't focus much on 180 autos. He put the lever down and set up for a field right in front of him (it was Texas, after all). He got it down okay, but evidently during the ground run, a skid dug in and the ship rolled onto it's side. Ouch.

Some would say, "Good job!" and leave it at that. But somewhere there was a commercial helicopter operator without the use of a (needed?) aircraft until a replacement could be procured. Somewhere there was an insurance company executive writing a check for the repair costs (minus deductable) of a brand-new EC-120. And somewhere there was a pilot with a very red face who will always wonder, "What if I had flown at 700 agl so I would have had a chance to turn into the wind?" (Let us hope that the unspoken question which will forever run through his mind is not, "What if I had known which way the wind was coming from that day?")

Is landing into the wind important? Obviously. To get back to the original question of this thread: Is a second or so enough?

It's not good enough to be an "average" or an "okay" or "so-so" helicopter pilot. That might work in fixed-wing, which tolerate such foolishness. Sometimes helicopters do not abide anything but perfect technique. And if you find yourself in one of those situations where you have 1.1 second to do something, you better hope to God that you're not only as good as you think you are, but as good as the situatioin demands.

[Shawn Coyle]

Has anyone had any experience in constant attitude autorotations in the R-22?

[Pat Malone]

We were taught that a constant-attitude auto in an R22 should be done at 40kt, and you'd only do it at night, but it was an academic exercise - I never knew anyone who took one to the ground.
A word about forward speed versus rate of descent in the flare/landing phase. A 22 will autorotate in the 1800fpm area. That's less than 20kt, vertically. It you spear in bum-first without even trying to flare, you've got the skids to absorb energy, then the seat structure.
But you're going forwards at 60kt or so, and all you've got between you and the tree/pylon/house etc is a quarter inch of perspex. Yet people seem to consider the vertical before the horizontal, and prefer to accept some run-on even in a tight area.

[Hughes500]

Pat

What is the problem with 60 kts airspeed, you flare it off about 35 ft from the ground. This does 2 things, increases Nr - therefore more stored inertia, reduces ROD to near zero. leaving you alot of energy in the blades to cushion your touchdown. In reality if you stand the helicopter on its end in no wind at 30 ft you will hardly run on at all. An anology for you for your 20 mph rod, would you prefer to come off a motorcycle at 60 mph and slide along road, or come off at 20 mph and hit a brickwall. It is accleration / decleration that kills. How many GP 500 riders do you see killed when they take a slide at 100 mph plus - nil.
Shawn, you havent answered my question - if you owned a brand new R22 ! Or are you a secret politician ?

[bugdevheli]

Having worked on a prototype tandem machine it becomes apparent that weight distribution is a problem. To accomodate a variety of front pilot weights on what is to be a light helicopter would indicate that some form of sliding ballast is required, and we cant carry any excess weight!. Instruments and long control runs again push up the weight. Because of the increased body area necessary to cover the two pilots when sitting tandem the benifits, whatever they may be, seem to be cancelled out by the additional bodyweight. If the rear seat is to be situated directly beneath the mast in order that the rear pilot does not afect the c of g, the engine has to go that little further back which again compounds the balance problem. What are the advantages of a tandem seating arrangement?.

The above post should be under lets build a helicopter! can somebody move it please?

[The Nr Fairy]

I'll concur with Pat on this one - I had constant attitude autos at 40 knots demoed to about 15 - 20 feet at night (when the grass comes into view).

Logic was at night you didn't want a flare because you couldn't then judge the last bit to end up level.

During the day, I'll take a standard auto with flare to get RoD and speed to an absolute minimum. And if I'm honest, I'd rather be in a Jettie or R44 when it does happen . . .

[Pat Malone]

Hughes500
Read it again, mate - the bit about the tree.
The context was a blind autorotation at 40kt at night.

[Shawn Coyle]

Hughes 500
I have a total of about 5 hours in Frank's machines, and none of it instructional, so I'm not in any position to anwer your question. That's why I asked if anyone had any experience doing it.
My experience on the Bell 206 series has shown me that constant attitude autos are pretty straightforward, but most people think you're going to die if you even try.
Hence the question - has anyone tried them to the ground in an R-22? If we haven't then we may be condemning a perfectly good technique for no good reason.
And God help me if I ever become a politician....

[Hughes500]

Pat

I did read it, you are assuming that you would do a 60 kt forward touchdown. If you fare off the speed you can put it straight down with no forward speed and without breaking anything. Best of luck if you bang an R22 in and rely on the seat structure and skid gear at 20 mph to zero . Before you do check to make sure no one has left anything under the seat like fuel tank dipstick, unless you like being pulled through with one !!
Now at night like the rest of mil pilots we were taught constant attitude - follow the landing light down - see the blades of grass and pull lever. Works well in gazelle and 206. I think the chances of bending an R22 are high doing this !

[Spaced]

I have been shown a couple while on the controls, I know its not the same as doing them, but Ill give a breif run through.
It was a simulation type run, emergency landing to small area, the idea being you didnt want to loose sight of your landing area by doing S turns.
60knts, 1500ft, reducing speed to 35-40knts IAS. Maintaining RRPM top of green. You really come down very steeply. First time feels like youre droppng vertically.
I would like to say the alt that pitch was pulled, Im guessing that it came on at about 60-75ft AGL, but Im really not sure, it all happens pretty quick. Arresting ROD, with a extra pull at teh bottom to cusion.
The instructor showed me 2 to ground. I stayed on the controls for both, but I wouldnt like to try one myself, not yet anyway.
I must say the first one really scared the c**p out of me. It feels very different to a "standard auto", especially during the decent. Its at the bottom where it all starts to become very quick.
Probably what makes it so harrowing is seeing the sirspeed drop below 60knts. You have drilled into you that 60knts is life in the robbie, so doing something different can be pretty unnerving at first.
I think that the reason the 60knt flare auto is the recommended is that if a low time pilot has an engine failure, establishes autorotation, and performs some sort of flare at teh bottom, then more than likely he will walk away, even if the machine is destroyed. Im not so sure that low time pilot in a constant speed auto, screwing it up at the bottom would be so lucky.
However all that paled in comparison to the backwards auto. Im convinced that that is not a natural manouver.

[pa42]

No-flare autos are becoming more of an R22 possibility as we go along, thanks all. But I can't put together a complete lesson plan yet: Spaced, what happens with the 40k forward airspeed (assume zero wind if convenient). Is ALL the paltry MR inertia expended on arresting descent, with a high-speed run-on touchdown? Or does the pitch attitude increase along with collective so that some of the MR energy is expended to decelerate before impact with the pungee stakes?

For the theoreticians (you know who you are!): where does this exploration of the survival envelope fall in terms of minimum-power-required (?53k in R22 = Vy), OR best glide (perhaps irrelevant, but in the last few years R22's seem to be assigned 75k), OR optimum autorotation IAS (65k quoted by RHC, there seems to be no aerodynamic justification for this, just Tradition, the Force Majeur in rotary flight!).

Seems like the alert CFI/practical aerodynamicist ought to be able to cook up a coherent energy management scenario (Delta 3, Lu?). Us CFI's out here in the trenches need sensible explanations to pass on to students--something better than "it's always been done that way."

[NickLappos]

pa42,

The issue is one of energy management, and the problem is that you have barely enough when all is working right. Look at the Space Shuttle landing, and note that it floats for a solid 10 seconds dropping at about 2 ft/sec at impact. I wish my helos would float that long on residual energy!

The ability to coax a zero ROD/ zero forward speed landing out of your machine is best achieved at the recommended procedure in the manual. If you plotted the ROD and forward speed as the two contributors to the energy state, and valued each alike, you would find that most helos want to be descended in auto at the forward edge of their best rate of climb speed (Vy).

Try your helo and see. Just settle up in auto descent at the recommended auto speed, and note the ROD. Redo the trial but set 15 knots faster, and then again at 15 knots slower.

The idea of a constant attitude descent seems so cool, but is not the ideal way to dissipate the total kinetic energy of the machine. Holding some extra forward speed (while not increasing rate of descent) is a way to bank some cyclic flare that arrests rate of descent without relying on the rotor energy. Many helos I have flown can arrest the ROD without pulling collective pitch. This has distinct benefits in conserving the rotor rpm for the touchdown. For rotorcraft with low rotor inertia, I believe a flare type auto is the most desirable, by far, and the most likely to result in a successful auto.

Having done the S-76 autos for certification at the highest weights and at the highest altitudes, I strongly suggest that nobody try to invent their own procedure and ignore the flight manual. Strongly!

[diethelm]

As a crumb counter, I know little about engineering but all the formulae I remember in colludge always seemed to have V squared when calculating energy.

Therefore, I am a big fan of not being short on airspeed.

[Shawn Coyle]

Please don't misunderstand my reasons for advocating the 'constant attitude' autorotation.
I fully agree with Nick and diethelm that airspeed is great, and that the V squared aspect is not well understood.
What I was trying to get across is that if you're going to teach a beginner something that is easy to do and has a good chance of survival, why not start with the constant attitude auto? Once proficient enough at that to survive when the unexpected happens, then start with the variations.
It has the advantage that in nearly all forward flight situations it would involve the helicopter being flared as part of the immediate actions following engine failure, which helps to build / maintain rotor RPM.

[Pat Malone]

Regarding whether a second or so is enough following engine failure, I was at a CAA safety evening last night where they touched on helicopter fatal accidents in the UK over the last eight years.
There were about 20, only one of which involved engine failure, and that resulted from neglect of carb heat.
Most of the remainder were bad attitude/poor decision-making. Loss of control in IMC. "Ran into high ground in IMC at night." In an R22, yet.
A second may or may not be enough in case of engine failure, but we can make decisions on whether or not to fly at our leisure.

[NickLappos]

Thank you, Pat!

I have prattled on about this, and now you have joined the Side of Reason.

The Lord gave us engine controls, and we put them to good use to practice engine failures and autorotations. We practice them enough to declare them to be the Prime Safety Concern. Now we fill pages and pages of threads about how many engines is enough, and how much performance we must have after an engine fails, and how few seconds we have to save ourselves from The Dreaded Engine Failure. Great Long Windy Discussions ensue.

Meanwhile, we run into hills, fly into bad weather with inappropriate instrumentation and hit trees and wires and things, and nobody ever asks "How do we stop this from happening?" Indeed.

thanks, Pat!

[Hughes500]

Nick/Pat I would agree entirely, in 15 years of flying I have had one engine failure. In the UK the biggest problem is the double edged sword of satnav. Before it came about low time pilots would not go flying in bad / marginal weather as they were concerned about getting lost. Now I often hear weather is bad but we will go as we don't need to wory about getting lost. Yes the moving map is great, even better in bad weather when you have a topo one, but they succour you in to pushing the limits !