Jump to content


Frasca VRForum468Helicopter AcademyTigerTugsVOLO_VRHome200
Photo
* * * * * 2 votes

Dangerous Oscillations on R44


  • Please log in to reply
32 replies to this topic

#21 MileHi480B

MileHi480B

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 198 posts
  • Gender:Male
  • Location:Denver, Colorado

Posted 14 August 2010 - 17:19

It is unbelievable to me that no one ever broached this subject when I was training. I often fly close to max weight.

And it is equally hard for me to believe that the master of "doom & gloom" (Frank, himself) would not include this in his morbid training syllabus. He seems to have a proclivity for telling us the worst that can happen!

This forum and this thread WILL save lives.

Now we need to have a standardized recovery method. CFIs, can you chime in?

Edited by MileHiR44, 14 August 2010 - 17:20.

  • PlatoNC and MileHi480B like this

#22 IFLY

IFLY

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 315 posts
  • Gender:Male
  • Location:Arizona
  • Company working for:Arizona Aero-Tech

Posted 16 August 2010 - 13:24

Does this only pertain to the R-44 near gross and forward CG or does the R-22 have a similar problem? The R-22 I fly is limited by forward CG not weight since it is setup for an instrument trainer.

Jerry
Jerry
Posted Image

#23 Goldy

Goldy

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 3,852 posts
  • Gender:Male
  • Location:La Crescenta-VNY, CA
  • Interests:uuuh? flying helicopers maybe?
  • Company working for:Hey I didn't know you could loop an R22 ???

Posted 16 August 2010 - 22:08

This forum and this thread WILL save lives.

Now we need to have a standardized recovery method. CFIs, can you chime in?


The NTSB says the manufacturer recommends the addition of power to counteract the oscillation. Good to know stuff!
  • PlatoNC likes this

Fly Safe !!

Goldy-CPL(H),R22A, HP, B, BII, R44 Astro, R1,RII,R44ClipperII, R66, B47G2, S300C, S333, B206B3, DG500, RV10, E480B, AS350BA, S-58T, what next?

FAA Aircraft Dealer
http://www.bestaerialphoto.com
http://www.phpa.org
http://www.rotorcraftpro.com
www.youtube.com/watch?v=SvN3GDEXPos
www.youtube.com/watch?v=vuX9SO5uCno


#24 crashed_05

crashed_05

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 335 posts
  • Gender:Male
  • Location:Bend, OR
  • Company working for:Leading Edge Aviation, Inc. ATP, Gold Seal CFII, MEI, IGI, AGI, & A&P

Posted 28 March 2011 - 13:59

This issue was addressed when I was at the Robinson Safety course last year. It only occurs in a certain range of serial numbers of the R-44. They found that the fore/aft oscillation was due to a certain type of rubber transmission mounts that were used and only happens at a certain rate of descent when flying over 100 knots. I can't remember all the details, but that's what it is.
  • PlatoNC likes this

#25 arotrhd

arotrhd

    VR Veteran Poster

  • VIP Member
  • PipPipPipPipPipPipPip
  • 370 posts
  • Gender:Male
  • Location:UPPER ECHELON OF MEDIOCRITY, Danger close to the Western gateway of the IE - a short launch North of the Orange Curtain
  • Interests:Everyone Home Safely. Always.

Posted 28 March 2011 - 18:09

This issue was addressed when I was at the Robinson Safety course last year. It only occurs in a certain range of serial numbers of the R-44. They found that the fore/aft oscillation was due to a certain type of rubber transmission mounts that were used and only happens at a certain rate of descent when flying over 100 knots. I can't remember all the details, but that's what it is.


dooly & Crashed - sincere thanks sharing the information.

If this is the case, it is disturbing that by the THIRD post this info wasn't published, especially given the population of VR peeps who fly Robbies and have attended the safety course and (gasp), post on other just-wouldn't-touch-it-with-a-10-foot-stick- helicoptersdotcom kinda sites and have something from there. :angry:

Should almost be a felony if Robinson isn't getting this info out post haste. And I like Frank and the crew a bunch, but this is beyond premeditated ridiculous.

-WATCH FOR THE PATTERNS, WATCH FOR THE WIRES-

Guinness (For Strength). Jameson (For Courage). Lex (For The Effort).
- Cap't Carrol 'Lex' LeFon, USN, 1960-2012


Fair seas and Headwinds over the deck, my Friend.

Commit to memory Checklist Items:

#1 ...Whiskey for my men, beer for my horses...
#2 No smoking 8 hours before the flight or drinking within 25 feet of the aircraft.
#3 If it can't be fixed with a hammer, it must be an electrical problem. Bend to fit, dent to match.
#4 I don't care about being right, as long as I prove you wrong.
#5 If you can't have a really good laugh, at least provide an entertaining cry.
#6 What the large print giveth, the fine print taketh away.
#7 Anyone who flies lower than me is a moron, anyone who flies higher is a maniac, any one who flies the same altitude is a threat.
#8 A boy makes his girl jealous of other women. A Gentleman makes other women jealous of a lady.
#9 The other vehicle is my crumple zone.
#10 One of the goals in my life is to be as good a person as my dog already thinks I am.
#11 America has a long history of dealing with those who stomp on rights. There’s the soap box, letter box, ballot box, jury box and the cartridge box for dealing with these sorts.
#12 Passion is what you do when it’s convenient, commitment is what you do when it is inconvenient.
#13 Never argue with an idiot; they bring you down to their level and beat you with their experience.

#14 It is customary caveman tradition to curse inanimate objects after making a mistake that causes injury to self.

#15 History doesn’t always repeat, but it usually rhymes. Tree. Politician. Rope. Some assembly required.

#16 Always plan for the mission as if you are the wetware that others are trying to liquidate somewhere between Destruction Bay and Explosionville.

#17 A goal too easily achieved is often a disappointment.

 

"I will not turn my clock back. I will be living one hour in the future. I greet you, The People of the Past. Your ways are quaint."

 

And sometimes, it just has to be said:

"I rode the short bus and I don't remember seeing you on my bus. But you should have been on it."


#26 iChris

iChris

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 937 posts
  • Gender:Male
  • Location:California

Posted 28 March 2011 - 21:52

The NTSB says the manufacturer recommends the addition of power to counteract the oscillation. Good to know stuff!



This issue was addressed when I was at the Robinson Safety course last year. It only occurs in a certain range of serial numbers of the R-44. They found that the fore/aft oscillation was due to a certain type of rubber transmission mounts that were used and only happens at a certain rate of descent when flying over 100 knots. I can't remember all the details, but that's what it is.


The 2009 report below issued some information. Transmission mounts as stated above:

NTSB Identification: ANC09GA040
14 CFR Public Use
Accident occurred Tuesday, May 12, 2009 in Iliamna, AK
Probable Cause Approval Date: 04/22/2010
Aircraft: ROBINSON HELICOPTER R44, registration: N7196H
Injuries: 3 Uninjured.

The National Transportation Safety Board determines the probable cause(s) of this ACC as follows:

The main rotor transmission mount design, which resulted in an in-flight vibration/oscillation, and damage to the helicopter during an emergency descent and hard landing. Contributing to the accident was the lack of information from the manufacturer regarding this known flight oscillation, and loading the helicopter beyond the forward center of gravity limit by the pilot.

The IIC contacted Robinson Helicopter, and asked if they were familiar with the term "chugging" as it related to Robinson helicopters, particularly the model R44.

During a telephone conversation with the manufacturer's accident investigator on May 27, the investigator said that he was familiar with the phenomenon known as "chugging," and that the manufacturer had conducted flight tests related to the phenomena. He said the tests determined that an oscillation may develop during operation of the helicopter at high gross weight, about 90-100 knots, and that the oscillation was more of a "bucking" motion due to the fore-and-aft movement of the rotor mast. He said that the tests showed the tendency to enter the oscillation regime was exacerbated by a forward CG (within the CG envelope) and a 30 degree banked turn to the left. He further indicated that the helicopter may also begin to oscillate in a right turn, but it entered the oscillation regime more easily in a left turn. According to the investigator, the tests also showed that chugging could occur within the normal CG range, and most typically at or near a gross weight condition. According to the manufacturer, it was determined that the oscillation is not divergent (destructive to the helicopter), and that the helicopter can be landed safely. He said that the oscillation can be mitigated by the application of power, and the condition flown out of. He said that the only damage he had seen to the test helicopter was on one occasion, when the pilot landed while the helicopter was still "bucking," and that the damage was manifested as dents/marks on the cabin-top, made by the fore-and-aft movement of the main rotor-shaft fairings.

The Robinson investigator said that the manufacturer attributes the oscillation to the firmness, or lack of firmness, of the transmission mounts, and that the manufacturer changes the mounts on helicopters that exhibit a tendency toward chugging during post manufacturing test flights. The investigator said he did not know the standard by which mount firmness was measured. He said he believed that approved helicopter service centers were aware of chugging, although currently there are no service alerts/bulletins referencing the phenomena. The investigator said to his knowledge there were no factory provided alerts/bulletins, pilot training, or Pilot Operating Handbook (POH) entries, pertaining to the chugging and the remedies to resolve it.

http://www3.ntsb.gov...513X60228&key=1

Edited by iChris, 29 March 2011 - 23:11.

  • MileHi480B likes this
Regards,

Chris

#27 Goldy

Goldy

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 3,852 posts
  • Gender:Male
  • Location:La Crescenta-VNY, CA
  • Interests:uuuh? flying helicopers maybe?
  • Company working for:Hey I didn't know you could loop an R22 ???

Posted 28 March 2011 - 23:36

WOW !

I guess I have just been lucky. Until this thread I have never heard a word about this, and was flying an R44 (or two). I was often at max gross, and due to my physique, usually leaning toward being front heavy. The R44 likes to fly around 100-105 knots, so I guess maybe I never made a left turn?

I'm glad they mentioned it at the safety course a year ago. Last I attended was about 5 years ago, so maybe when I go again it will come up.

Not knowing any of this, I think my instinct would have been to slow the ship down, which usually means a reduction of power..sounds like that may not have ended well.

Thanks again to the OP.

Fly Safe !!

Goldy-CPL(H),R22A, HP, B, BII, R44 Astro, R1,RII,R44ClipperII, R66, B47G2, S300C, S333, B206B3, DG500, RV10, E480B, AS350BA, S-58T, what next?

FAA Aircraft Dealer
http://www.bestaerialphoto.com
http://www.phpa.org
http://www.rotorcraftpro.com
www.youtube.com/watch?v=SvN3GDEXPos
www.youtube.com/watch?v=vuX9SO5uCno


#28 MileHi480B

MileHi480B

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 198 posts
  • Gender:Male
  • Location:Denver, Colorado

Posted 29 March 2011 - 02:37

Unbelievable. He builds em, requests a special FAR to fly em, requires a safety course to be in compliance with "purchase contract" and then makes new owners agree not to sell to anyone unless they also take the course, then sticks owners with all kinds of mandatory "upgrades" based on lawsuits filed against him, but somehow in all of this paranoia he manages NOT to inform owners of this potentially lethal "quirk".

Nice going Frank. Your company's inconstancies in the market place are only preceded by your arrogance.
  • MileHi480B likes this

#29 arotrhd

arotrhd

    VR Veteran Poster

  • VIP Member
  • PipPipPipPipPipPipPip
  • 370 posts
  • Gender:Male
  • Location:UPPER ECHELON OF MEDIOCRITY, Danger close to the Western gateway of the IE - a short launch North of the Orange Curtain
  • Interests:Everyone Home Safely. Always.

Posted 29 March 2011 - 12:52

Confirmed my suspicions this morning: current Safety Notice as published by Robinson on their web (for R-44 &-22) are SN-31 & SN-34; neither is regarding the "Chugging" or "Bucking".

WTF?

Might need to give Mr. Tucker a call.

-WATCH FOR THE PATTERNS, WATCH FOR THE WIRES-

Guinness (For Strength). Jameson (For Courage). Lex (For The Effort).
- Cap't Carrol 'Lex' LeFon, USN, 1960-2012


Fair seas and Headwinds over the deck, my Friend.

Commit to memory Checklist Items:

#1 ...Whiskey for my men, beer for my horses...
#2 No smoking 8 hours before the flight or drinking within 25 feet of the aircraft.
#3 If it can't be fixed with a hammer, it must be an electrical problem. Bend to fit, dent to match.
#4 I don't care about being right, as long as I prove you wrong.
#5 If you can't have a really good laugh, at least provide an entertaining cry.
#6 What the large print giveth, the fine print taketh away.
#7 Anyone who flies lower than me is a moron, anyone who flies higher is a maniac, any one who flies the same altitude is a threat.
#8 A boy makes his girl jealous of other women. A Gentleman makes other women jealous of a lady.
#9 The other vehicle is my crumple zone.
#10 One of the goals in my life is to be as good a person as my dog already thinks I am.
#11 America has a long history of dealing with those who stomp on rights. There’s the soap box, letter box, ballot box, jury box and the cartridge box for dealing with these sorts.
#12 Passion is what you do when it’s convenient, commitment is what you do when it is inconvenient.
#13 Never argue with an idiot; they bring you down to their level and beat you with their experience.

#14 It is customary caveman tradition to curse inanimate objects after making a mistake that causes injury to self.

#15 History doesn’t always repeat, but it usually rhymes. Tree. Politician. Rope. Some assembly required.

#16 Always plan for the mission as if you are the wetware that others are trying to liquidate somewhere between Destruction Bay and Explosionville.

#17 A goal too easily achieved is often a disappointment.

 

"I will not turn my clock back. I will be living one hour in the future. I greet you, The People of the Past. Your ways are quaint."

 

And sometimes, it just has to be said:

"I rode the short bus and I don't remember seeing you on my bus. But you should have been on it."


#30 nightsta1ker

nightsta1ker

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 781 posts
  • Gender:Male
  • Location:Vegas, Baby!

Posted 30 March 2012 - 14:55

Well, apparently the R44 is not alone in being susceptible to this condition. The B206 can also get into it although it was dubbed "pylon whirl" instead of "chugging". Basically, if you are flying a teetering system, which all have tall masts, then there is a possibility it can happen at high fwd cg and high cruise speeds.
  • MileHi480B likes this

#31 Pohi

Pohi

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 962 posts

Posted 31 March 2012 - 22:36

Does this happen during autos? As in if, for some reason, a person was doing a left hand 360 turn?


#32 nightsta1ker

nightsta1ker

    VR Veteran Poster

  • VR Member
  • PipPipPipPipPipPipPip
  • 781 posts
  • Gender:Male
  • Location:Vegas, Baby!

Posted 01 April 2012 - 11:04

Honestly, I don't know if we know enough about it to predict exact conditions upon which it can occur. It does not happen very often at all, but from what I have been able to find, it happens at high cruise speeds at or near max gross in the R44. I also know that it should absolutely be avoided in the B206 because when cruise speed is over 80 knots, you are limited to 85% torque (generally near max gross in a 206 you are around 80% anyway) or you will twist the mast, so if you start getting pylon whirl, the corrective action being to pull more power, you might go from one bad condition to a worse one.

Going back to the R44, I suppose there could be other scenarios that lead to chugging, considering it is usually due to dry-rotted transmission mount absorbers, my best guess would be that anything that gets the mast going in a pendular fashion might get you into it.

Some interesting links to check out regarding the subject:
http://www.pprune.or...a-chugging.html

http://www.ainonline...44-mast-rocking

http://www.robinsonh...53&topic=1053.0

http://aircrashed.co...NC09GA040.shtml

There's a lot more out there. Needless to say many many operators have never heard of this, or did not know what was going on if they experienced it. Reports started as isolated, but as the R44 community becomes more aware of the issue, more pilots are stepping forward and reporting incidents where this has happened. Robinson's reaction to this has been less than stellar in my opinion. I would think that this should be blasted at high volume so that pilot's can avoid it, and trained in recovery procedures. I think they are coming around now, but only after the FAA and many concerned operators have made a stink about it. They also just settled a huge lawsuit on a fatal crash that may have been related to this. In typical Robinson fashion, someone needs to die and they need to get sued before they address an issue. Maybe that's not completely fair to single out Robinson for this, as it seems to be the standard for most manufacturers these days, but they seem to have more issues than other manufacturers.

#33 paulrohricht

paulrohricht

    Newbie

  • Members
  • Pip
  • 1 posts

Posted 03 May 2015 - 21:41

I am running an independent investigation on R44 chugging phenomenon and would like to speak to any pilots who have experienced this.  Please feel free to contact me at paulrohricht@gmail.com, or +1 (704) 249-8342.






1 user(s) are reading this topic

0 members, 1 guests, 0 anonymous users



PrecisionVRForumHome200HeliHelmets-VR HomeMaunaLoaVRHome200NFCVRForum200HomeGenesys VR Forum 200Spectrum_VRHome200