Rotary Wing Forum  

Go Back   Rotary Wing Forum > Rotorcraft > General Discussion

Reply
 
Thread Tools Rate Thread Display Modes
  #1  
Old 02-11-2017, 05:42 AM
Mike G's Avatar
Mike G Mike G is offline
Platinum Member
 
Join Date: Jun 2005
Location: Lillebonne France
Posts: 1,351
Default Question for Brian Cobb

Bryan
Where does this:
"3.0 IPS vibration (unairworthy by FAA standards) and a 0.5 IPS vibration (well within acceptable standards of airworthiness)."
come from?

If it's an FAA document I'd like to understand the context.
Mike G
Reply With Quote
  #2  
Old 02-11-2017, 06:39 AM
bryancobb's Avatar
bryancobb bryancobb is offline
Platinum Member
 
Join Date: Aug 2010
Location: Cartersville, GA
Posts: 4,852
Default Vibes

Quote:
Originally Posted by Mike G View Post
Bryan
Where does this:
"3.0 IPS vibration (unairworthy by FAA standards) and a 0.5 IPS vibration (well within acceptable standards of airworthiness)."
come from?

If it's an FAA document I'd like to understand the context.
Mike G
I have been diligently searching for that elusive document for us

I remember reading and seeing it SOMEWHERE...AND...It agrees with
manufacturer's limits in the Maintenance Manuals for helicopters I am familiar with.

I will post every tidbit of supporting data I can find to support my statements. Thanks.

Bryan
__________________
Bryan Cobb, Helicopter Enthusiast
Mfg.Engineer., Composites, Meggitt Aerospace, Rockmart, GA
Reply With Quote
  #3  
Old 02-11-2017, 12:35 PM
Jincamty's Avatar
Jincamty Jincamty is offline
Magic free zone
 
Join Date: Apr 2010
Location: Te Kauwhata, New Zealand
Posts: 315
Send a message via Skype™ to Jincamty
Default

I had >3 IPS @ 2/rev up at the mast on a homebuilt helicopter and it's bloody scary.
Much like a car that is about to loose a tire at 100 mph.
I can see why there would be an upper limit from the authorities.

Cheers Cam
Reply With Quote
  #4  
Old 02-11-2017, 12:57 PM
hillberg's Avatar
hillberg hillberg is offline
Platinum Member
 
Join Date: May 2010
Location: Low Earth Orbit
Posts: 2,483
Default

The manufacture will determine the ips required in helicopter operations after maintenance - The Helicopter Directorate in Fort Worth will adopt general limits as a reference in Advisory Circulars ...AC 27-1A AC 29 2C ????
Reply With Quote
  #5  
Old 02-11-2017, 05:56 PM
bryancobb's Avatar
bryancobb bryancobb is offline
Platinum Member
 
Join Date: Aug 2010
Location: Cartersville, GA
Posts: 4,852
Default

I didn`t have time to post the pics today but I looked up 8 different helicopters` Approved Maintenance Manuals and every one of them listed 0.2 IPS as the maximum to be accepted. All the instructions said something like keep at it until the maximum vibrations are under 0.2 IPS.

All polar charts had their outer (worst vibes) ring at 1.0 IPS.

Everything from the MD-600N to Bell 47 to Robinson R-66 and Enstrom. Haven`t yet found the UH-1 stuff but still looking.
__________________
Bryan Cobb, Helicopter Enthusiast
Mfg.Engineer., Composites, Meggitt Aerospace, Rockmart, GA
Reply With Quote
  #6  
Old 02-11-2017, 07:23 PM
HobbyCAD HobbyCAD is offline
Homebuilt Heli Enthusiast
 
Join Date: Jul 2008
Location: Hervey Bay, QLD, Australia
Posts: 1,560
Default

What's the expected IPS of the CH-47 rear rotor?
__________________
If you don't know where you're going, any road will get you there
Reply With Quote
  #7  
Old 02-11-2017, 08:29 PM
Jincamty's Avatar
Jincamty Jincamty is offline
Magic free zone
 
Join Date: Apr 2010
Location: Te Kauwhata, New Zealand
Posts: 315
Send a message via Skype™ to Jincamty
Default

This one got up to 400 IPS before destroying the transducer :-)

https://www.youtube.com/watch?v=roN2jvu-Jis
Reply With Quote
  #8  
Old 02-12-2017, 10:32 AM
brett s's Avatar
brett s brett s is offline
Gold Supporter
 
Join Date: May 2004
Location: Ball Ground, GA
Posts: 2,385
Default

Every helicopter I've worked on had the acceptable limit set at 0.2 IPS, including CH-47's.

The older metal blades were a lot easier to track & balance on Chinooks than the composite ones they rolled out in the 80's. They also weren't nearly as tough & made less lift though.
__________________
Brett Sumpter
Roswell, GA
Reply With Quote
  #9  
Old 02-12-2017, 12:23 PM
HobbyCAD HobbyCAD is offline
Homebuilt Heli Enthusiast
 
Join Date: Jul 2008
Location: Hervey Bay, QLD, Australia
Posts: 1,560
Default

Quote:
Originally Posted by brett s View Post
Every helicopter I've worked on had the acceptable limit set at 0.2 IPS, including CH-47's.

The older metal blades were a lot easier to track & balance on Chinooks than the composite ones they rolled out in the 80's. They also weren't nearly as tough & made less lift though.
My experience in Chinooks has been to sit as far forward possible, for the rear was always teeth chattering.
__________________
If you don't know where you're going, any road will get you there
Reply With Quote
  #10  
Old 02-13-2017, 01:54 AM
Jean Claude Jean Claude is offline
Platinum Member
 
Join Date: Jan 2009
Location: Centre FRANCE
Posts: 1,584
Default

Bryan,
Just observing the maintenance manual of the Robinson R22, it appears to me that the IPS requirement is only for 1/rev, since in hover. I see no IPS requirement in forward flight (2/rev).



http://rotorcorp.com/wp-content/uplo...ck_balance.pdf

Last edited by Jean Claude; 02-13-2017 at 02:20 AM.
Reply With Quote
  #11  
Old 02-13-2017, 03:12 AM
bryancobb's Avatar
bryancobb bryancobb is offline
Platinum Member
 
Join Date: Aug 2010
Location: Cartersville, GA
Posts: 4,852
Default

Quote:
Originally Posted by Jean Claude View Post
Bryan,
Just observing the maintenance manual of the Robinson R22, it appears to me that the IPS requirement is only for 1/rev, since in hover. I see no IPS requirement in forward flight (2/rev).
Usually JC, the very next procedure in the Maintenance Manual is the forward flight T&B. Then after that you make one more fine adjustment in a hover to conclude.
__________________
Bryan Cobb, Helicopter Enthusiast
Mfg.Engineer., Composites, Meggitt Aerospace, Rockmart, GA
Reply With Quote
  #12  
Old 02-13-2017, 03:31 AM
bryancobb's Avatar
bryancobb bryancobb is offline
Platinum Member
 
Join Date: Aug 2010
Location: Cartersville, GA
Posts: 4,852
Default

__________________
Bryan Cobb, Helicopter Enthusiast
Mfg.Engineer., Composites, Meggitt Aerospace, Rockmart, GA
Reply With Quote
  #13  
Old 02-13-2017, 04:09 AM
Jean Claude Jean Claude is offline
Platinum Member
 
Join Date: Jan 2009
Location: Centre FRANCE
Posts: 1,584
Default

Bryan, How much IPS max are required during the forward flight, here?
Reply With Quote
  #14  
Old 02-13-2017, 05:24 AM
brett s's Avatar
brett s brett s is offline
Gold Supporter
 
Join Date: May 2004
Location: Ball Ground, GA
Posts: 2,385
Default

Quote:
Originally Posted by HobbyCAD View Post
My experience in Chinooks has been to sit as far forward possible, for the rear was always teeth chattering.
I don't remember any difference in vibration, but the noise level was worse in the back. Ever fly in one with all the soundproofing removed? It definitely makes a big difference!

I've got a fair amount of hearing loss + tinnitus as a reminder of my crewmember days...

As far as vibration in hover vs fwd flight goes - it can be a compromise for sure.
__________________
Brett Sumpter
Roswell, GA
Reply With Quote
  #15  
Old 02-13-2017, 07:55 AM
bryancobb's Avatar
bryancobb bryancobb is offline
Platinum Member
 
Join Date: Aug 2010
Location: Cartersville, GA
Posts: 4,852
Default

Quote:
Originally Posted by Jean Claude View Post
Bryan, How much IPS max are required during the forward flight, here?
In THIS case of the R-22, they are not specifying. They only say that as long as hover vibration is less than 0.2 IPS AND the forward flight tracking AT EVERY SPEED, is within 3/8", you are good to go.

On my Mini-500, I have hover IPS at 0.10 to o.18 IPS. Forward flight tracking has not been fine tuned but The DSS MicroBalancer shows it bouncing around from 0 to 0.25.
__________________
Bryan Cobb, Helicopter Enthusiast
Mfg.Engineer., Composites, Meggitt Aerospace, Rockmart, GA

Last edited by bryancobb; 02-13-2017 at 07:58 AM.
Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -8. The time now is 07:56 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Ad Management plugin by RedTyger