Lowering collective while running on

[TheFlyingSquirrel]

Does anyone teach or practice lowering the collective during an autorotative run on to slow the ground run, before the aircraft has come to a complete stop?

TFS

[overpitched]

I've run a 47 on at about 40kts (few mechanical problems) and couldn't work out why it wouldn't stop. Lowering the collective sorted that out quite quickly.
You wouldn't want to be too abrupt though or I think you might end up in a little ball.

[Aesir]

Yes sure it´s ok to lower the collective to create some friction to help slow down but don´t lower it all the way!

How much to lower the collective depends on the type of surface.

Sometimes it´s easier and less risky to tell new students not to lower it at all, less chance of mistakes.

[rotorque]

TFS,

I was actually taught to use the collective as a break in certain situations and still do to this day.

I just go by gut feel as to how much to use... on a good surface you can come to a 'grinding' halt pretty quick

It also works from altitude as well, just keep the collective down all the way to the ground in an auto and then crawl out of the wreckage to measure how far you travelled....:)

[KENNYR]

The use of collective as a "brake" depends on several factors, such as type of surface, forward speed, slope etc. etc.. In some helicopters the run-on speed is so high as a norm that you must lower the collective to stop (e.g. the Scout). Just be careful with how quickly you apply the collective braking force, only apply as much is as necessary to safely bring you to a stop without digging a ditch with the nose of the aircraft!!

[tommacklin]

Kennyr is quite right, it depends on the aircraft you are flying and the touchdown surface etc. In general, however, the normal drill would be to cushion the touchdown and leave the collective where it is. The decaying rrpm will allow the weight of the aircraft to transfer steadily onto the undercarriage, moving the collective at this point affects this transfer of weight and can turn a successful eol into a bumpy ride resulting in damage to the aircraft.

[rotornut]

Yes. When I got my CPL we practiced a lot of run on autos on a snow covered runway. It was a lot of fun and didn't hurt the skids. However, we didn't do it on tarmac or on grass runways very much. Machine was a Hughes 300C.

[Sailor Vee]

Don't any of you guys have WHEELS?:p

[Hueymeister]

Auto run on no snags other than the above....power on beware of bending the MGB mounting bolts/points. Easy does it every time.

[NickLappos]

In virtually every helo I have instructed in, the collective pitch should be lowered smoothly once ground contact is had on an autorotative landing, even while running on.

Excessively low rotor rpm while the craft is moving (exposed to lurching and varying winds) is a bad thing, and any movement of the cyclic while in that state could lead to blade-fuselage contact and a major problem.
This does not mean that you dump the collective, nor do you force strong ground contact, but you must not leave the lever up any longer than necessary.
I have no Robinson time, and certainly defer to those who do and advocate something else, but leaving the collective up is certainly not the norm for helicopter autos.

[SASless]

Just yesterday....doing some training here in the UK...in the Huey...lowering the collective much at all after touchdown on the sod brought you to an almost instant stop...thus much stress on the skid crosstubes and mounts...and a very real risk of poking the nose into the ground.

We found we had to carry a bit of collective to prevent that...but as Nick says....lowering the collective as soon and as much as possible is the desired technique. The amount and rate of reduction depends upon how "sticky" the surface is.

On a smooth hard surface...a smooth, gradual reduction of collective will bring you to a stop in a much shorter distance than merely holding what pitch setting you have at touch down. The key is to avoid causing the aircraft to pitch, buck, or stop abruptly.

[tommacklin]

Well, I am guessing that Nick and I fly quite different types, or use quite different techniques. On most of the types on which I have instructed, if the collective lever is lowered upon ground contact, the braking action becomes too fierce, therefore, as a general rule, once the touchdown is cushioned, the lever is left in that position, perhaps a slight reduction if any. Of course, the lever has to be gently lowered completely at some point to min-pitch, this would normally be carried out as soon as possible after touchdown, but not at the expense of ferocious braking.

I once did an eol at MW on a frosty morning, touched down in the eol area and just kept going. In that case, more braking was applied as required in order to stop before the Lynx parking area.

Most of the EOLs I have done have been to grass. I can see, however, that an eol to a runway would probably sustain more braking to be applied by lowering the lever sooner.

[NickLappos]

tommacklin,

I don't think we are far apart, the only thing we differ on is the concept of how much and when to lower the lever. I do not advocate leaving the lever up for an hour, and I'll bet you don't either, and I also do not advocate leaving it up while the Nr goes below 60%, and I will bet you don't either.

The idea of leaving the lever up and letting the rotor drop below the min range for autos as a directed training task is very bad, very very bad. The idea that the wear on the skids is controlled by bashing the head up is also very bad.

I know you don't advocate that, but by making the collective task controlled by the skids, and failing to even consider the other point, you leave all the above open to those who do not see the pitfalls.

Again, I suggest that you lower the collective when on the ground, lower it gently, and be aware of how it will change your ground friction. Do not let the rotor droop significantly below min demonstrated rotor speed, especially if there is much wind or wind gust. If you can't prevent rough stops, don't touch down at that spot.

Auto training is supposed to prevent accidents, not create them!

PS, with the rotor rpm at 65%, the peak thrust the rotor can develop is miniscule, and of little help in friction avoidance.

[tommacklin]

What an idiot! I just wrote a response to Nicks last, at my thought/typing speed it took a little while, then I went flying, finished off the response and pressed "submit reply", only to be informed that I had been logged off. Response lost....idiot! I'll get back to it shortly.

Nick,

I do not disagree with anything you say, however, I think that there are so many factors to take into account that I am reluctant to accept your suggested method without stressing the following:

1. Each type of helicopter has its own characteristics regarding autorotative touchdown...rate of Nr decay, normal touchdown speed immediately spring to mind. An EOL to the same touchdown point in eg. a Gazelle, would require a different collective response to eg, a Scout.

2. If a pilot is trained to lower the collective upon touchdown regardless, I believe he is put at an immediate disadvantage.

3. The aim of EOL training is to provide the pilot with the necessary skill to put the aircraft safely on the ground in the event of a power failure. Another essential aim of EOL training is to minimise the effect of the training regarding wear and tear on the aircraft. I would suggest there have been many more training incidents caused by rapid deceleration than by allowing the rrpm to decay too much with the lever still raised.

4. Very few pilots have the capacity to note max rrpm droop on an EOL touchdown, therefore, figures become less relevant than the drill.

Without labouring the point, I don\'t think we are far apart, however, based on the variety of views and affecting factors, it seems a very relevant question by TFS. I no longer believe there is a conclusive answer if the question is asked of helicopters in general. A more accurate answer may be forthcoming if asked of specific types and specific touchdown surfaces.

tm

[TheFlyingSquirrel]

Thanks for your replies all, as usual. Does anyone here use the lever as a brake on the R22?

Thanks again, TFS:)

[TiPwEiGhT]

Not normally, but I have before if the run on is going more than planned/estimated and i am heading towards tarmac.

TiP

[OVERTALK]

Mast-bumping during autos was claimed by BELL as having led to three mast ovulations found after UH-1B main rotor separations in my Sqn.

Analysis of our touchdown auto practises disclosed that the techniques being used to minimize ground-roll were very variable and that a lot of mast-bumping was occurring. The SENGO brought a mast into the Pilot's Crewroom to show us. Looking up the inside, the degree of ovularity was alarming - although looking at the outside of the mast, particularly around the stops, you just couldn't see it.

Beware the cumulative effect of touchdown mast-bumping.

[Oogle]

Squirrel

Only use it as a brake when you have to. ie. obstacle closing in real fast!

If in training, be nice a gentle (as Nick and Tom have already said).

[TheFlyingSquirrel]

Well the point I am making really, is that during my PPL and CPL training, I was always trained to let the machine run on until it stopped. It was never mentioned to me or discussed at any point during the 6 years I have been flying helos. I think it's a pretty important point don't you? - especially as forward speed is the killer. " Oh yeah, if you ever have to make a real EOL and a tree is coming up quick, you can lower the collective gently and you'll stop quicker. " I always ramble on about poor quality instruction. I don't know if i've received a whole barrel load of ****e instructors or I just have a far deeper interest than most. I suspect a fair quanity of both. Do any UK FI's out there even mention this when training students ?

TFS

[Oogle]

No, I don't think its a matter of having ****e instructors. They are just trying not to break the boss's aircraft. They (like me) have probably never had a real engine failure (in a single).

The same can be said when pilots first receive multi-engine training (OEI - one engine inoperative). The first few times you ask (and show) them to slow down gradually - much like at the end of an engine off landing albeit a bit more benign.

Most ME helicopters can't hover on one engine so you use the ground contact to slow you down. But if there is a tree/obstacle racing towards you - do what you have to do and push that collective down as fast as is needed.

[TheFlyingSquirrel]

When running on and lowering the collective, how will pedal input change to keep the aircraft straight?

[FixedRotaryWing]

... how will pedal input change to keep the aircraft straight?

What will you do, if you perform a running landing in case of stuck pedals?

[KENNYR]

FRW, use throttle to control heading during power run-on landing. In the event that you have one of the unluckiest days in your life and your pedals jam during a donkey stop then take all your forward speed off during the flare and accept the inevitable rotation during the "check" phase of the manoeuvre. Minimise effects by prudent use of the wind.

[tommacklin]

TFS

I am presuming that you are still talking about an autorotative landing rather than a run on landing with power.

Once the engine is no longer driving the rotor, there is no torque reaction. In fact, quite the opposite, there is a dragging effect of the main rotor trying to drag the fuselage around with it. This has the effect of changing the "power pedal". For example, in powered flight in lets say, a 206, the power pedal is the one on the left. Under power, if this pedal is pressed it will increase the power requirement. In an eol, if the right pedal is pressed, it will sap precious inertia(power) from the main rotor. Therefore, you could find yourself in an eol touchdown with an adverse wind, using the right pedal to keep the aircraft straight and end up running out of pedal as the rrpm decays to a level which no longer allows tail rotor authority.

Another factor to include whilst considering using the collective as a brake!!

[FixedRotaryWing]

A running landing is IMHO a touchdown with forward speed, powerd or not. Running landings are not only done in EOL. I was teached and am used to lower collective gradually to reduce speed.

[IFMU]

I've only ever done one of these, but I'll open my mouth anyway. I was doing touchdown autos as a student, and I blew it. Was going to end up in the pit at the north end of the runway on the wrong side of the fence. The instructor told me to flare over the pit, hold 60, and milk the collective to clear the fence and touch down at 60. As I touched down, I could see the sparks flying in the chin bubble windows. It sounded really bad. I had no desire to drop the collective and grind it out any worse. The last 5 feet were really ugly as it finally ground to a halt. I leaned out the door and looked back, amused to see two smoke trails rising from the runway like something out of a roadrunner cartoon. The aircraft was an Enstrom F28A.

-- IFMU

[Oogle]

You obviously walked away (or even flew away) after all this?!?!

Bugger the skids - job well done I say. :ok:

[tommacklin]

Oogle....

"Bugger the skids"

I'm glad you don't train in my aircraft!

[IFMU]

Flew away. Skids were fine. The carbides on them were a little thinner, though.

-- IFMU