Longranger thought

[Chairmanofthebored]

When the aircraft is shut-down the blades slow down to stop directly fore and aft - more often than not...
Why???
...is it cause I am that good. Thought so...

[Arm out the window]

If you land and shut down into wind mostly, then they tend to align themselves that way.
I've definitely noticed that with the Jet Rangers in a strong wind - you end up with a blade pointing into wind.

[GLSNightPilot]

Especially if you're experienced with the rotor brake.

[B Sousa]

GLS ....your too good...........

[Gordy]

Originally Posted by GLSNightPilot

Especially if you're experienced with the rotor brake.

Gotta agree with you there----I can always get mine to stop at "10" o clock and "2" o clock........

[Arm out the window]

Rotor brake ... I dream of having a rotor brake!
Would have been very handy the other day when shutting down on a pad, if you could call it that, right on the edge of a coastal ridge with 30 kt blowing in off the sea - rotor wasn't going to stop, ever.
Eventually with some judicious pitch-pulling, gnashing of teeth and rocking around on the skids as the transmission bounced around, it finally stopped - not very pretty at all.
The takeoff was a bit nicer though, hardly any power needed to hover or climb away.

[John Eacott]

AOTW,

Good luck with the next head overhaul, if it makes it that far

It sounds as if you're lucky that the blade tips didn't hit the tail boom, apart from the no-no of pulling pitch to slow down the blades

[FlightOops]

John Eacott... for the benefit of the inexperienced, could you explain why pulling picth to stop the rotors is a no-no ?

I have been with a pilot with a squillion hours doing that as well as applying full left pedal in a 206 that had no rotor brake.

As the RPM was well below any value sufficient for lift, and owing to my inexperience I assumed this was a safe practice.

Your comments would be very welcome.

Thanks in advance,
FO

[Arm out the window]

John, I've exaggerated somewhat with the bouncing around part, but certainly did use some pitch to slow the rotor down, as little as I could get away with. If the rocking on the skids had been any worse than it was, I would have just started up again and departed.
Having said that, it was common practice for all on 205s at one place I worked - shut down, and pull a bunch of pitch to slow the blades more quickly than if they ran down themselves.
Everyone did it - not saying it was right, and there was some talk of it being bad for the TT straps, but the maintainers never voiced any concern about it.

[Semi Rigid]

jump out & climb upstairs & grab hold of the mast with ya paws.sheez.pussies.

[Ascend Charlie]

In a Huey in the 70s, the blades didn't want to stop. Groundie says "I'll fix it, sir!" and before I realised what he was doing, he scrambled up the side steps and reached for the blade above him. Well, grabbing it at 1/3 of the blade's length wasn't ever going to give him much of a moment to stop it, and I gasped as I saw his legs disappear past the right door and past the right overhead window. This turned to laughter when i saw his face looking down with horror through the left overhead window. He was smart enough to let go the blade before it pulled him off the roof.

Also watched a new bograt standing out the front with the tie-down, waiting for the right time to reach up and grab the almost-stopped blade - there is a certain amount of momentum in a Huey blade. As the blade spun down, I called out (jokingly - it was way too fast!!) "This one, Marron!" and he leapt off the ground and grabbed it.... Well, I have never laughed so hard, tears running down my face. He grabbed the blade, feet off the ground, and he turned a beautiful cartwheel in mid-air and landed on his @rse in the dust. Wonderful to watch, I think he is a Qantas captain now.

[GLSNightPilot]

Once, long ago, we had rotor brakes in the 206 that were part of the aircraft hydraulics. You got one chance to stop the blades, and then there was no brake left. I shut down on an offshore platform with a wooden deck, stopped the blades, got out, got the tiedown stick out of the baggage compartment, and saw that the blades had started turning because of the wind. I walked to the left front quadrant and casually jumped up to catch the blade as it lazily swung around. The next thing I knew I was on the deck near the tailboom, almost on the fence, with splinters in my backside and back, and pain throughout my torso. I wasn't sure I could get up, but I finally did, and now the blades were turning at a pretty good rate. I crawled back into the cockpit, started the engine to regain hydraulics, stopped the blades, got out, and the blades started turning again. I finally kept hitting the leading edges with the tiedown stick as they passed overhead, and eventually succeeded in stopping the blades and getting them tied down. I was in no shape to fly back to the beach right then, and didn't want to lose the aircraft because of the windmilling blades, which can turn at a good rpm with a strong lifting wind. After a few hours, my passenger was ready to go and I sort of felt up to flying, and we got back to the beach, but that's the last time I ever tried to stop any blades manually. A rotor brake is an essential investment. If you don't have one, you will eventually learn that.

[Chairmanofthebored]

So apart from all the other useless info here, nobody can supply a decent reason why they would orientate to fore and aft? I was considering that it might be something like a worn G/Box bearing, sun gear tooth...
??

[imabell]

cotb,

just coincidence, no secret, happens a lot.

pulling pitch to slow the main rotor, especially at low rpm can and does damage the straps in the head. ask an engineer. (didn't know there where straps in the head???) i think that's what john is referring to.

that is why you should never raise the collective and at the same time move the cyclic through full travel when the blades are static.

it can be very expensive.

[kjw57]

Having flown a whack of hours in the Long Dog I can only remember the blades alining themselves fore and aft when finally stopped just a couple of times. As for pulling pitch to slow them down a good question for the Bell Techies I suspect.

Mind you all that bothersome inertia comes in handy at the bottom end of a silent descent...

[Arm out the window]

Does anyone know what kind of damage is done to the TT straps by pulling pitch on shutdown, or the kind of movements imabell described, and why it isn't a factor when you pull pitch with power on?
The greater coning angle of the blades with pitch at low rpm would be one thing that comes to mind.

This is one of those things where some people say it's a no-no, others don't, so some tech info, an AD or a maintenance manual note, something along those lines would be good if anyone knows.

[John Eacott]

AOTW,

Since I can only find the reference by omission, I called Nelson H (Bell Customer Support Rep) this morning who agrees, and confirmed what I thought: but agrees that it is only referred to in the FM by what is not said, rather than what is said! There is a reference to the flight controls being locked prior to shut down, and an allowance for the cyclic to be used to minimise static stop contact, but not to allow collective movement.

He is asking Bell for a firm reference, and I will post the reply when it arrives.

[Sandy Toad]

In the mists of time I seem to recall it was to do with Grip Seals and extra flexing allowed oil to seep out; then when oil changed to grease the restriction didn't apply. But could be wrong.
Do remember flying BO105 with the old and learned who designed the magnificent rotor system and being told not to use full pedal to slow Nr as they had never done the stress sums for it.
Guess we'll always find something to do the designers never thought of!

[Arm out the window]

Thanks, John, much appreciated.

Sandy, the reference to grip oil leaks brings back memories from the 205, I think that's one of the things that was bandied around as to the cons of pulling pitch to slow the blade, when we still had the blade grip reservoirs - was said to make them leak, or maybe my brain cells are dieing out quicker than I thought.

[Phnix]

Originally Posted by imabell

that is why you should never raise the collective and at the same time move the cyclic through full travel when the blades are static.
it can be very expensive.

so how do you check for full and free movement on your pre start check?
or should the movement be only limited to a few inches,
I have put some hours on the same Jet Rangers in the last few years, and my pre start check has always been full and free, and I know that the straps have been replaced, but only when there time was up.