sovietjet
Posts: 2549
Joined: Sat Mar 15, 2003 12:32 am

Question About Mi-8/-17 Propeller

Fri Dec 09, 2005 2:41 pm

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..
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Question About Mi-8/-17 Propeller

Sat Dec 10, 2005 9:50 am

Counterweights?

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 :-)
 
Airgypsy
Posts: 130
Joined: Tue Nov 23, 1999 11:02 am

RE: Question About Mi-8/-17 Propeller

Sun Dec 11, 2005 9:40 am

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 avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Question About Mi-8/-17 Propeller

Sun Dec 11, 2005 7:10 pm

LINK
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
aeroweanie
Posts: 1577
Joined: Fri Dec 03, 2004 9:33 pm

RE: Question About Mi-8/-17 Propeller

Mon Dec 12, 2005 5:08 am

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

Who is online

Users browsing this forum: glen, thepinkmachine, WIederling and 11 guests