Pedal/collective to slow the rotors
 

Hello to all,
Disclaimer : I'm a PPL, so only little experience, and I wouldn't try what I'm about to describe, merely wondering if it is ever used to save time/reduce the risks for the immediate environment (people, animals) of a spinning rotor.

Is it feasible/wrong/stupid/bad to add pedal input after shutdown (as much as terrain will allow without spinning the machine around) to slow the rotors faster ?

Moreover, is it feasible/wrong/stupid/bad to gradually add collective for the same purpose ?

Thanks for your replies, again, I'm a PPL, never in a hurry when flying, and don't envisage to use these techniques, so feel free to say its ridiculously stupid :=

collective is a no no,
I have no problem with left pedal (in a 300 becasuse there's no brake:ugh:)

Never heard of dynamic rollover being an issue, but raising the collective at low rpm can cause excessive flapping which can damage the rotorhead and cause M/R to contact the tailboom.

Collective is a no-no (my main concern would be flapping / and sailing)

Pedal can be fine (and quite effective), depending on what the flight manual says.

Always read the flight manual and speak to an experience pilot on type

OH

Collective - no

Pedal - I would be v. careful. Living in N Europe, very easy to get into a routine which - in icy conditions - you may apply without thought and end up frightening yourself / others (or worse).

I would not go there. Particularly as a low-hour pilot.

Bell 47 / Hughes 269
 

I stand to be corrected but if memory serves me right I thought the Bell 47 manual stated that some collective pitch could be applied once the RRPM had dropped below a certain figure. (Perhaps a third)
I also think the H269C could have been approved to apply left pedal once the RRPM had dropped below a certain figure to assist with RRPM slowdown.

I have parked several times on top of a cliff. The blades would be just over the edge. The wind would keep the blades turning. So I did add some collective to get them to stop. It was a UH1H and it worked HOWEVER I can see flapping would be a consideration. I see no problem being gentle, left peddle and pay attention to the operators manual.

Jerry

If you are talking about the helicopters yawing on the ground (Or on the water with floats etc) with application of the collective then I would say I do not think so. The engine (I am assuming here) is off therefore there is no torque. That being said if you were using a rotor brake the helicopter will tend to turn in the direction of blade rotation upon brake application.

Good question by the Frenchrotorhead.

I need to do some research on the dynamic rollover thing.....

The main reason I see adding a little collective as being a bad idea is the risk of ground resonance (rigid multi bladed rotors), excessive flapping (hinged two bladed rotors) and blade sailing in both.

But then again, isn't it the case (pitch with RRPM going down) at the end of a full, engine off auto ?

BLCL

Try it on an icy pad. No engine to supply torque, use pedal to apply counter-torque, round you go!

On an icy pad there is almost zero fricional resistance to any input force.

Like so many things in helicopter aviation (e.g. hot refueling, getting out with the engine running, scud-running), using the collective and/or pedals to slow the rotor after shutdown should be accompanied by the caveat: DON'T BE AN IDIOT! USE SOME COMMON SENSE!

The Bell 47 indeed once allowed for up to 1/3 of the collective travel to be used for slowing the rotor. Even if a 47 had a rotor brake, it would barely stop a Schwinn bicycle much less a set of high-inertia metal blades. Once the 206 was invented (and with it a better rotor brake) that procedure disappeared from the flight manual.

Then later on Bell got all antsy about people using left pedal to slow the rotors, because the tail rotor could bang against the flap stops. But banging against the flap stops can happen even when shutting down in strong crosswinds and stuff. So the wise, old 206 pilot trims the pedals to minimize this during shutdown. Sometimes it takes left pedal; sometimes it takes right. You have to find that "sweet spot."

If you've flown a Hughes 500 you know that there's a spring that pulls the left pedal forward as the rotor slows. Sort of an "automatic" rotor brake.

In my non-rotor brake-equipped Bell 206B, I sometimes use a bit of collective and pedal to slow the blades, depending on how badly I have to pee. I said a "bit" of collective. The forces are certainly no stronger than those imparted by a hovering auto (or powered flight in the case of the t/r), and I'm careful to not let either of the rotors get flapping too wildly. I do not just yank full-up on the collective and jab full left pedal in and then exit the a/c in a big hurry no matter how urgently I have to do the aforementioned deed.

Use the brain God gave you, and don't be an idiot. Apply a bit of common sense and be smart about these things. If we all did that, perhaps we wouldn't have flight manuals that are as thick as the Manhattan Yellow Pages, with all sorts of admonishments to the stupidest among us.

I remember learning to fly helicopters in Jet Ranger (206). There were cautions against using the T/R and collective to slow down the rotor when we shut down after a sortie at Whiting Field. (Can't recall if it was in the NATOPS or the squadron SOP, been nearly thirty years).

Of course, my instructor nearly always, when he was doing the shut down, added a bit of rudder and a bit of a colective ... but woe unto the student who did that. :cool:

FH1100: agree with most of your post.

the flight manual for the machine you are operating should describe the limitations regarding this. as a CPL or PPL, any pilot should be familiar with what they say and act accordingly as i can not imagine the manufacturers putting limitations in there for sh!ts and giggles ;)
fp

We often use pedal / collective to slow the blades, however generally only in a wind as the damn things won't stop themselves (no rotor brakes). If you do it gently you will actually reduce the beating that they get by leaving everything centered... 206 and 204's, and only start playing with when less than about 30% or so, no slippery surfaces, so not much chance of going round.

A worse habit I have seen, is standing outside the machine, leaning in and shutting it off.:eek: with that quick whack of the throttle, if you do it the wrong way you are in for some fun.... Have even seen guys lean over the left seat, on right hand drive, and whack it off. Surely an opportunity to get it wrong. Before you go off about getting out of a helicopter with blades turning, let's forget that as it is well covered, and outside Europe seems to be a well accepted practise, main reason it goes wrong is when they leave it at flight idle! :ugh:

MD 500 and 269/300 are similar in this regard. I have been taught that it is poor form in these machines to allow the pedals to sit hard over in either direction for any length of time. As the tail rotor blades are retained by blade straps, which are slightly streched at their edges during full deflection, full defection is to me kept to a minimum.

I have seen many techniques demonstrated after touchdown. I have always been most comfortable with the "attend the controls, and hold them in their sweet spot, until it stops" approach myself.

Im not a huge fan of adding a lot of pedal while shutting down only because your putting stress on the tail boom and attachment bolts(yaw thrust being applied at the end of the boom but skids not allowing the turn) i just dont imagine that being too good for the mounting bolts... and with the wrong crosswind/pedal input your can actually make the T/R blades "auto-rotate". if the manual allows for either then its obviously ok, but i prefer gentle application of collective and watching the tip path to avoid stop contacts. in general these techniques wont save much time, but with a strong wind and a weak battery, shutting down on a pinnacle... you gotta do whats needed to get them stopped and get the electricity offline. no jump starts on mountains. just follow the Manual and be smart!

perhaps I should have added left pedal after engine has stopped so in the 300 the main rotors speed will be down around the 150 rpm mark, cant see this putting much stress on anything, ( I could be wrong I frequently am:\)

I always thought that this is exactly what the tailboom was designed for? What do you do if you want to climb - just let the machine yaw right, because left pedal would put too much stress on the tailboom?