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Rising collective...


Justin DBC
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We have an R-22 BII at our school which, aside from a quite severely rising collective, is an awsome bird with a lot of power. My question is, is it a no-go to throw on some collective friction after I take off to arrest the rise? I wouldn't want to have it on during taxiing, takeoff, or landing, but I also don't like having to constantly mess with my collective in straight and level flight.

 

Thanks!

J-

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I've done that before on ships with rising, or sinking, collectives. As you said, I wouldn't do it during take off, landing or taxiing etc. I also wouldn't apply full friction, just enough to stop it creeping. I like it to stay where I leave it, but I wouldn't want to be fighting much friction if I had to dump collective in a hurry.

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Thanks. That's pretty much what I was thinking, but I wanted to get some other opinions before I did it. Our pilots use collective friction religiously in the hawks, but there is a lot of stuff you can do with a UH-60 that you cant do with a Robbie ;)

 

J-

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just be sure if you are in level cruise and take your hand off the collective to adjust radio's GPS, etc; lower your power/MP out of the yellow arch to give you extra time to lower collective and maintain RRPM in case of engine failure. They really drove that issue home at the factory course I attended.

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On the newer spring assemblies it's basicly just a matter of rotating the spring assembly on the collective to decrease upward force. The older ones aren't much more difficult. I'm going to bring it up to maintenance again... I would do it myself, but I don't have a civilian A&P rating.

 

J-

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I dunno. I get nervous about anything that makes it harder to get that collective down fast in an R22 if there's an emergency.

 

HVG

 

(That being said, I hate it when helicopters try to lift off on me without permission. Shouldn't be that difficult to get the trim adjusted.)

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Yeah, put a little friction on. Shouldn't be a big deal. I once had a simulated engine failure on a xc flight with friction almost all the way on. Well, I slammed it down, tried to adjust for the climbing RRPM, reached back to take off the friction and my seatbelt came off. Did I mention it was summer in Louisiana and the doors were off? So now I'm trying to auto, my instructor is bugging me about this or that, trying to put my seatbelt back on and trying not to fall out of an aircraft.

 

Just use a little friction. :D

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On the R22/R44, a collective that rises on its own can also be an indication that the rotor may have been oversped at some point, and/or the spindle bearings need replacing. Not a mechanic either, but our R44 had the same symptom last year until we replaced those bearings. Also, apparently this may not be something you can check with the blades still attached to the hub - it's too hard to feel the bearings bind up unless you turn them by hand (at the boot). Might wanna look into that as well.

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I remember training in a R22 with a rising collective just like you described. First solo in that ship. Many months later, I learned that a bolt connecting the Collective to the Control arms had begun to shear. Only found it during a major repair or Inspection. Be careful out there.

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I fly with a little friction all the time, on both the collective and cyclic. It doesn't slow anything down, it just keeps the controls from moving if I'm not making any inputs. It's a matter of personal preference - I know pilots who don't want any friction ever, but being used to larger aircraft with AFCS/SAS/etc, I don't like sloppy controls, and never have, even before I flew larger aircraft. I've always liked a little friction, giving a little feel to the controls.

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On the R22/R44, a collective that rises on its own can also be an indication that the rotor may have been oversped at some point, and/or the spindle bearings need replacing.

 

 

BINGO- My thought exactly. Often if this is the case, the cyclic will want to stir, the main rotor may have additional vibration that didnt use to be there, track and balance wont help, or wont last...these are all possible indications of something much more serious going on. A rising collective can also be very dangerous when your goal is to maintain rotor RPM...

 

Personally, I would have it checked by a really qualified mechanic. I have flown 20 different R22's, on 2 of them, I could tell somthing was wrong even though the mechanic couldnt find it until many hours later. Both times were blades cracked, and/or bad spindle bearings from overspeeds.

 

The ship talks to you, just have to listen to it now and then

 

Goldy

Edited by Goldy
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Robinson does not want you to use friction to stop the collective from moving.

There are 3 different strength trim springs available for the collective, and the collective "must never creep in flight" (RHC quote).

If it does, a different spring should be installed, or the MR needs to be checked as mentioned before.

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Have seen a 500 with new blades that leap into the air on initial wind up, was OK on flight idle, Had to have seat surgically removed from pilot.

A lot of 500s suffer from either very light (will creep up) or real heavy collective, there is a adjuster to compensate for this but you should check rigging and blade set up first, we changed blades neutral collective, New blades needed Mr Mussel this was a combination of tabs & different blades Boeing to HTC.

We use a little friction, if you are scared enough!! you will overcome it.

 

Get it checked better safe than splat.

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Question for other than Robbie pilots on this.....

Are the frictions the same as on a Robbie? Being that it is a screw that rides in a slot next to and attached to the collective and tightening it down pinches the metal plate it rides in?

As far as I'm concerned using a friction for more than a few seconds in flights to read a map etc is not advisable. After all screws can tighten up from up and down movement, and it seems to me if memory serves the lower end of the slot of the metal plate seemed thicker and could possibly prevent full down collective if the screw tightened a bit, either way, I'm not one to advise its use yet until I know more.

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One particular R-22 I used to fly had an issue with the collective creeping up. When I would apply a little friction to stop it from creeping, I found that any subsequent movement I made to the collective seemed to remove the friction. I would climb out and get to the straight and level phase of my flight, apply a little friction at say 20 inches, then find that I really wanted about 20.5 inches, so nudge it up a little. Then I would find that it was creeping again, and that the friction was off, so I would set the friction again. This happened several times on that particular flight, enough that I know I wasn't imagining it! It was quite a long time ago now, and not a ship that I flew much at all. It left me wondering if the friction was designed in such a way that it released if the collective were forced. Has anyone else experienced this or have any more information on this?

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Question for other than Robbie pilots on this.....

Are the frictions the same as on a Robbie?

 

Edit: Sorry, misread your question. You were asking OTHER than Robinsons. Most of the frictions are similar, a little more complex and not as easy to adjust. The ones on a Bell are similar to the RHC cyclic frictions, and they are very easy to strip knob if you're not careful.

 

It's very similar to what you describe--for the collective. The collective is attached to a slotted arm. In the track of the slotted arm, there's a hex head screw attached to a lever on one side of the arm; a Belleville (spring/conincal) washer on the other side with a nut. Moving the lever increases or decreases the amount of torque on that spring washer setting the friction.

 

The cyclic friction is a stack of washer. Half of the washers are fixed to the frame; then every other one has an arm coming off the side attached to the cyclic. So when the friction is off, every other washer (then ones attached to the cyclic) are allow to float. Tightening it down causes friction between the fixed and floating ones.

 

Both should be adjusted no matter how hard you crank them down, you can always overpower them. The collective has a counterbalance spring in the left baggage comp directly underneath the fuel valve. It has a limited amount of adjustment by means of a turnbuckle, but in some cases, the spring needs to be switched out. Three springs, color coated (gray, gold, and ???). RHC makes a special tool to compress the spring, but it's worthless. I would just compress it, then safety wire it. Once you get it installed, cut the wire. Adjust the collective spring for whatever you do more (duals in or duals out.)

 

I always fly with some collective friction on. I never let the thing loose enough that my elbow, turbulence, etc. could move it. On the 206Ls I fly, we've had a few problems with pilot reaching underneath the collective, then getting their watch or sleeve caught on the big switch box on the end--overtorque. I can always overpower the friction in an emergency. I just grip the cyclic with my legs; I never use friction there.

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UPDATE:

 

I tried adding a small bit of friction yesterday and it completely fixed the problem. Coincidently, I found myself in a situation where I was forced to slam the collective down (suicidal flock of birds) and had no trouble getting it down.

 

I'll bring up what you guys said to the mechanics next time I'm in. Thanks for the advice!

 

J-

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Justin- a "little" friction never hurts, but the ship should not want to aggressively climb when hands off...could just be a spring adjustment, could be much more.

 

BTW- went up today, lil windy at 26 knots, but wow....75 miles vis out there...

 

Goldy

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The vis has been great all week. Took my girlfriend for her first helicopter ride a few days ago out to Catalina and another one of our Crewchief's up yesterday. It did seem like the winds were a bit higher than reported for the flight yesterday, but the view was amazing. Looks like it's starting to cloud back up a little today though. Not all good things can last unfortunately.

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Dunno anything about Robinsons, but in the 300 HMI, in the rigging / flight testing section it states that the collective in flite, with hands off, must either stay put OR lower. If it rises the spring tension must be adjusted. I had a set of blades once that no matter how much spring tension I put on it, collective still rose in flite--the cordwise CG was all out of whack on that set & i sent them back.

 

I'de recommend checking in the maintenance manual for the Robbie.

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i haven't been able to find inspection criteria for it. there is a section that describes how to adjust the spring tension, but not about limitations. i don't think there is enough inspection stuff in the r-22 maintenance manual in general.....

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