Sponsor Message:
Aviation Technical / Operations Forum
My Starred Topics | Profile | New Topic | Forum Index | Help | Search 
Question About Mi-8/-17 Propeller  
User currently offlineSovietjet From Bulgaria, joined Mar 2003, 2732 posts, RR: 15
Posted (10 years 5 months 10 hours ago) and read 2212 times:
Support Airliners.net - become a First Class Member!

I have noticed something about this Mi-8 helicopter(as wel las a couple of others). This Mi-8 LZ-CAE has these sorta brown small round-looking things attached to the top of the propeller blades. There's five total following the pattern of the blades. However, in a previous picture it doesn't have them. What are they and why were they added? Some sort of balance weights or floating devices?

Pic from 1980: no things

View Large View Medium
Click here for bigger photo!

Photo © Tony Edlind

Pic from 2000: with things

View Large View Medium
Click here for bigger photo!

Photo © Harro Ranter

Thanks if anybody knows..

4 replies: All unread, jump to last
User currently offlineKELPkid From United States of America, joined Nov 2005, 6833 posts, RR: 3
Reply 1, posted (10 years 4 months 4 weeks 1 day 15 hours ago) and read 2159 times:


I don't know, I'm not much of a helicopter guy...

BTW, if you want the helicopter fanatics to take notice of this topic, change the word in the title from "Propeller" to "Rotor."

I don't know why helicopters have a different terminology for it, but they refer to the big propeller on top as the "Main Rotor" and the small one at the back as the "Tail Rotor."

Cheers!  Smile

Celebrating the birth of KELPkidJR on August 5, 2009 :-)
User currently offlineAirgypsy From United States of America, joined Nov 1999, 130 posts, RR: 2
Reply 2, posted (10 years 4 months 4 weeks 15 hours ago) and read 2125 times:

Those weights seem to be part of the rotor pitch change mechanism. Loss of a connection could be catastrophic but a flyweight could provide a very good safety by commanding the blade to a safe pitch. (Dassault Falcons have springs that neutralize control surfaces if they get disconnected from the control rod.) Could just provide some pitch input dampening to improve handling. If they have a website, don't be bashful.

User currently offlineHAWK21M From India, joined Jan 2001, 31875 posts, RR: 54
Reply 3, posted (10 years 4 months 4 weeks 6 hours ago) and read 2094 times:


Think of the brighter side!
User currently offlineAeroWeanie From United States of America, joined Dec 2004, 1612 posts, RR: 51
Reply 4, posted (10 years 4 months 3 weeks 6 days 20 hours ago) and read 2074 times:
Support Airliners.net - become a First Class Member!

The things you see are called bifilars. They are weights on short arms that are free to move in two axes. The weights move to cancel out vibrations emanating from the rotor system. Sikorsky pioneered the use of bifilars, but they actually date back to radial piston engines - they were used on crankshafts to dampen vibrations. One of the Sikorsky dynamicis engineers who was a key player in developing the concept was Bill Paul, who later served as President of Sikorsky for a short period in the 1980s.

Bifilars were retrofitted to some S-61s and were designed into the UH-60/SH-60, S-76 (the S-76 has a double stack) and S-92:

View Large View Medium
Click here for bigger photo!

Photo © Paul Kanagie

View Large View Medium
Click here for bigger photo!

Photo © Agustin Anaya

View Large View Medium
Click here for bigger photo!

Photo © Jason Hick

View Large View Medium
Click here for bigger photo!

Photo © Andrea Mugni - SpotIT

Top Of Page
Forum Index

Reply To This Topic Question About Mi-8/-17 Propeller
No username? Sign up now!

Forgot Password? Be reminded.
Remember me on this computer (uses cookies)
  • Tech/Ops related posts only!
  • Not Tech/Ops related? Use the other forums
  • No adverts of any kind. This includes web pages.
  • No hostile language or criticizing of others.
  • Do not post copyright protected material.
  • Use relevant and describing topics.
  • Check if your post already been discussed.
  • Check your spelling!
Add Images Add SmiliesPosting Help

Please check your spelling (press "Check Spelling" above)

Similar topics:More similar topics...
Question About The Propeller Contrails posted Wed Feb 7 2007 18:05:28 by Ariis
Question About Traveling This Holiday Week posted Tue Nov 22 2011 12:40:34 by gegtim
Question About LHR T5C Jetways posted Sat Nov 19 2011 07:00:19 by PC12Fan
Question About This Stormy Take-off posted Mon Oct 10 2011 13:26:03 by TheSonntag
Question About This AN-225 posted Sat Aug 13 2011 17:07:58 by c5load
Question About Car Licence Plates For ATCs posted Mon Jun 27 2011 06:42:36 by YokoTsuno
Question About Holding Patterns posted Sun Jun 12 2011 05:11:18 by YokoTsuno
Question About Avionic Technician posted Sat May 21 2011 11:19:04 by tuvoc
A Question About Diversions posted Sun May 1 2011 15:03:53 by ozark1
Question About UA Baggage Ops At PDX posted Tue Apr 26 2011 16:25:02 by AlnessW

Sponsor Message:
Printer friendly format