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

sounds like a track and balance issue

It’s only normal for a voice to tremble out of fear in a robbie. Does sound like bad tracking or rigging.

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.

At 4000' and minus 8 degrees, what was your chart Vne?

130kn, or 120 over 2200lb. He was GTG.

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....

Wasn't there a thing called "chugging" or "mast rocking" in some 44s in the past? :confused: 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

so cruise speed in a r44 under 2200 lbs is 130 knots ? At 4000 ft

The question was about Vne

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.

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".
:eek:

I'd deeply inspect those new rotor blades for signs of delaminating.

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.

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).

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.

Just explain who pays for the helicopter you fly, Rotten John?

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.

A true apples vs. oranges comparison.

it’s the goto fantasy.
Dispense with the type of operation (recreational in one, HEMS/fire/utility etc in the other), the relative numbers of hours flown (historically pistons have a small percentage of overall rotary flight hours), then you can convince yourself that statistics removed from any and all context, have meaning.

Will take a Bell deathtrap any time.
its also a damnside easier to read a Bell FM. None of those supplemental safety notices telling you how not to fly it and how slow it should go when things get bumpy.

Yeah, I love the 22, and I'd take it over anything to just fly around for fun, but given the choice between a 44 and a 206, I'd pick the 206 (even if it is slower and the tail rotor isn't as good).

It just seems like the bigger the Robby design gets, the more issues it has. Plus, just putting a bandaid over that "chugging" thing while never finding its cause still makes me feel a bit uneasy getting into one of those. I'd still take a job giving rides in one over the Summer, but it'd always be on the back if my mind,..which kinda sucks.

And here once again is the chart that shows the REAL facts.The Robinson R44 led all major models with the highest fatal accident rate from 2006 to 2016.

Death rate (Fatal accidents per 100,000 flight hours)
https://www.latimes.com/projects/la-...DT.png?foo=bar Lorena Iñiguez Elebee Sources: National Transportation Safety Board, Federal Aviation Administration, Times analysis

Having taught in 22s since the mid 80s, and 44s since 2006, I'd say the 44 has had less issues than the 22. Which makes sense, because Robinson was able to fix a bunch of the shortcomings of the 22. And of course it has a ton more power than the 22, especially with two or three people on board.

Did I just imagine being told chugging was caused when a supplier changed the composition of the rubber transmission mounts without telling Robinson, and that chugging was encountered when you had a mix of old and new mounts on one aircraft? I could have sworn I heard that at the factory... Certainly glad I never encountered it, sounded scary as hell.


It's kind of a wash for me. Like you said, 44 tail rotor is night and day better than the 206 ( I've never flown with the Van Horn dunno how much that helps ). 44 is, as you say, substantially faster than the 206. And of course substantially cheaper to operate although as the pilot I don't care THAT much... Although I've been flying with the T Bar cyclic for 35 years, I still hate it. And yeah, low gee. But the 206 has the dynamic tail boom mode. The 44 has instant torque when you need it, and no hot starts. The list goes on and on... The truth is they each have some advantages and some disadvantages.

If I'm giving a tour, I strongly prefer the 44 with the open cabin. Other than that? Meh. Whatever.

I've never heard of that explanation for the chugging but it makes sense, and it does explain why the problem seems to have gone away a decade ago. I've never heard of recent reports about it, nor ever experienced it myself (though I did fly some 2006 models).

No, those are the numbers that the LA Times purport to be "real facts". You should not trust the US media := Unless their conclusions are the ones you want, of course ;).

They did get the total number of accidents correct as they matched with the NTSB database. But the fleet hour data is suspect. Those of us in the US know what a crappy job owners and operators do with the annual FAA operations survey. Many, perhaps most, simply get thrown right in the trash. I've spoken to several people at the FAA. Nobody has been able to give me a breakdown, by aircraft model number, yearly operating hours, of the data they do have. And they do have data, but it's currently only available (to me, anyway) broken down by type of operation or industry sector, not by helicopter type or model number. Short of a formal FOIA request, I've thrown in the towel on ever getting good fleet hour data. However, I would love to be hooked up with the right person at the FAA who could supply those numbers. If anyone's got a contact there please PM me.

Nevertheless: let's assume that the data is correct. And let's further assume that the R44 is more dangerous because of its design, not because of the type of operations it experiences (low time, low currency piloting, etc.) Even if you believe all that is true, it is still near to becoming the most produced helicopter of all time, rapidly gaining on the current champion, the 206. Clearly the risk/reward trade-off in the community sides with the R44. And because of this it may be that the economics of the R44 are not only an enabler of its successes, but also its failures.

Personally I think it's a very good design that had some unfortunate teething pains. I'm lucky in that I came to the community after most of those teething pains had been mitigated. As an owner I didn't quite miss the last mandatory MRB AD, but even that worked in my favor in terms of acquisition cost, believe it or not.

Fly it. Don't fly it. Everyone needs to work out their own salvation. For many it's what they can afford, so it's going to get flown unless and until the FAA (or whoever) says it can't be.

I've only flown the 22 in the 21st century, so I never got to experience its gowing pains.

As for my design remark, it was more about the tall mast and top mounted swash plate. I don't know if that design makes any difference, but it just seems like as the helicopter gets bigger that taller mast might cause more issues? Anyway, it was just a though?

Now with tours, I'd definitely go with the 206,...gotta have that separation between me and them!

,...you know if you take off the cfi grip on the 44's cyclic, its just a "J" Bar. :8

I'm curious, how would the FAA have fleet hours ("...by aircraft model number, yearly operating hours")?

They send a survey letter out to every N number registrant every year, requesting how many hours that N number flew, and for what purpose. As you might imagine, not everyone goes through the exercise of meticulously reporting that data, or reporting at all. The process is completely voluntary.

not sure what that has to do with anything, but if it’s important to you, clients.

I think you're talking about the FAA Annual General Aviation (GA) and Part 135 Activity Survey. A strictly voluntary survey distributed by mail to a representative sample of GA and on-demand Part 135 aircraft owners and operators. How could that be used to determine hours by tail number or type? The survey is designed to estimate the size, primary use, and flight hours of the entire GA fleet.

Thank you, Jim. Exactly! You are making my case for me. There is NO WAY that the FAA or anyone else has any sort of reliable and complete data on how many hours each type of helicopter flies. Thus the famous LA Times "Danger Spins From the Sky" article is predicated on data that could not possibly exist in any sort of accurate form.

If I'm wrong about this I'd gladly accept correction, because I'd really love to have the data to look at myself. Alas, the only hard data that appears to exist is the NTSB aviation accident database, which does not track operational hours. There is also the FAA aircraft registration database, so the number of aircraft of each type can be also be accurately known. I've done that dance, and published it on PPRuNe, and when scaled for fleet size Robinson compares well to Bell. But, again, no operational hour data.

I once had a similar problem in sub freezing weather due to the pitch change boots becoming stiff at cold temperatures. The solution was changing the boots to a more pliable rubber formulation. I would think current production would incorporate the more pliable formulation.

You still have to choose between regular boots and so-called "winter" boots. I've had problems with the regular boots leaking in the winter. I run the winter boots.

Not trying to prove anyone’s point. Just saying you are making an apple vs. oranges comparison, akin to arguing who’s the best baseball player of all time. The type of flying enters heavily into the equation (i.e. instructional, offshore, tour, air ambulance, fire-fighting, personal, etc.) along with the number of people on the aircraft (more/less chance of fatality).