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R44 shaking at high speed (But within green arc)

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R44 shaking at high speed (But within green arc)

Old 20th Sep 2020, 21:25
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R44 shaking at high speed (But within green arc)

I am new to the helicopter world and the ship I am flying is a new R44 Raven I with only 60 hours on hobbs.
Yesterday early morning we were flying cross country over Northern Pennsylvania skies at 4000 Ft. Once we established cruise speed of around100-110 KTs I realized that helicopter is shaking quite a bit. It was not that bad that one has to consider precautionary landing but it sure was uncomfortable and our voice was trembling when we tried to talk. According to the guy sitting next to me who has lot more time in Robinsons than me , this was quite normal /common in R44 and mentioned that it was because of cold and dense air we are moving through. once we descended and flew at lower speeds for approach etc it was all normal.
A cold front has moved through the night before and surface temp was 0 degree C . OAT with calm winds , at 4000 ft was - 8 d c with north winds at 10 Kts.
Please share your experiences and thoughts here
Thanks

Last edited by kansarasc; 20th Sep 2020 at 21:41.
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Old 20th Sep 2020, 21:48
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sounds like a track and balance issue
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Old 20th Sep 2020, 21:52
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Itís only normal for a voice to tremble out of fear in a robbie. Does sound like bad tracking or rigging.
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Old 21st Sep 2020, 00:26
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Even with main rotor track and balance within spec it is still only a 2 blade main rotor. You are going to experience a bit of vibration, more than in a 3 or 4 bladed machine.

Nevertheless, go visit your local Robinson service center, have them fly with you, and see if they think it needs a fresh track and balance. With 60 hours on brand new components there is a bit of initial wearing in going on and that can affect the original track and balance.
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Old 21st Sep 2020, 01:18
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At 4000' and minus 8 degrees, what was your chart Vne?
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Old 21st Sep 2020, 01:28
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130kn, or 120 over 2200lb. He was GTG.
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Old 21st Sep 2020, 09:06
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There should be no reason why you couldn't get an R44 smooth at cruise speed. Sounds like it needs the track and balance gear put back on and the trim tabs sound like they need a tweak. 2 bladed systems are some of the smoothest I have ever flown....
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Old 21st Sep 2020, 15:14
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Wasn't there a thing called "chugging" or "mast rocking" in some 44s in the past? I overheard Tim Tucker talk about it during the safety course but I was under the impression that it was solved and didn't happen anymore.

https://www.ainonline.com/aviation-n...4-mast-rocking

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Old 21st Sep 2020, 15:16
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Originally Posted by aa777888 View Post
130kn, or 120 over 2200lb. He was GTG.
so cruise speed in a r44 under 2200 lbs is 130 knots ? At 4000 ft
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Old 21st Sep 2020, 15:18
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Originally Posted by md 600 driver View Post
so cruise speed in a r44 under 2200 lbs is 130 knots ? At 4000 ft
The question was about Vne
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Old 21st Sep 2020, 15:54
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Worst vibration I have ever encountered was a five bladed rotor with a stuck/sticky dragging hinge and a jammed battery balance tray!

Made my nose itch like buggery! Not really an issue in a Robbo though.

Certainly sounds like a tracking issue. Sometimes you can hear a slight whistling noise from the blades flying out of track.
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Old 21st Sep 2020, 16:37
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Worst vibration I've ever felt was in an Enstrom, felt like a 7.0 earthquake!

,...he just said, "hmm guess it needs a track and balance".
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Old 21st Sep 2020, 16:38
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I'd deeply inspect those new rotor blades for signs of delaminating.
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Old 21st Sep 2020, 21:06
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Given the damage an untreated vibration can do - look at the Australia crash on another thread - you should have this checked out thoroughly before you fly it again.
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Old 22nd Sep 2020, 00:21
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Not normal, I've flown R44s at 120 knots and it was perfectly smooth. This was not in freezing air but that shouldn't matter. I agree that the helicopter should not be flown until the issue is resolved (aside from minimal test flights; the mechanic will add monitoring equipment and then have you fly with them to gather measurements).
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Old 22nd Sep 2020, 01:18
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https://www.atsb.gov.au/publications...r/ao-2020-049/
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Old 24th Sep 2020, 08:42
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In 10000 hours of helicopter time the biggest fright I’ve had is in one of those bloody things, descending right hand turn and it started the chugging thing, seriously thought it was going to destroy itself. Didn’t they start usiing stiffer transmission mount rubber blocks in an effort to fix that issue?
Is there any other aircraft built in mass numbers which have had so many tragic results from not totally explained reasons?
I will never get in another.
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Old 24th Sep 2020, 15:20
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Just explain who pays for the helicopter you fly, Rotten John?
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Old 24th Sep 2020, 15:28
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While it is a bit disturbing that the root cause of the "mast rocking" (that's what the NTSB calls it) problem has never been found (or Robinson isn't talking if it has), nevertheless Robinson seems to have gotten a usable handle on the issue back in the 2007 time frame, whereby they developed a pre-delivery test for the problem and tuned the transmission mounts to eliminate the issue. Theoretically no ship has left the factory with the problem since, however there is no guarantee that it can't occur later in a ship's lifetime. I haven't read of any problems since 2011 or thereabouts, and all those were pre-2007 builds. As a Robinson owner and pilot I'd be interested in any evidence of this problem in aircraft delivered in 2008 or later.

Meanwhile, it seems much more likely this is a garden variety T&B issue, not some zebra of a mast rocking problem.

As for "mass numbers", a simple check of the NTSB database shows 619 fatal accidents for Bell helicopters (all types) vs. 380 for Robinson helicopters (all types), using a search start date equal to the first NTSB recorded Robinson fatality on 3 May 1980. Leave the ground in any machine at your peril.

I would not be a helicopter pilot were it not for the economics of Robinson helicopters, and I certainly would not be an owner if it were not for the economics of the R44 specifically. To me whatever risk you wish to assign to that is more than worth it.


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Old 24th Sep 2020, 15:49
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Originally Posted by aa777888 View Post
...
As for "mass numbers", a simple check of the NTSB database shows 619 fatal accidents for Bell helicopters (all types) vs. 380 for Robinson helicopters (all types), using a search start date equal to the first NTSB recorded Robinson fatality on 3 May 1980. Leave the ground in any machine at your peril.
...
A true apples vs. oranges comparison.
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