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ACRO E-mail Archive Thread: [Acro] RE: Aileron Flutter Question

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ACRO E-mail Archive Thread: [Acro] RE: Aileron Flutter Question


Thread: [Acro] RE: Aileron Flutter Question

Message: [Acro] RE: Aileron Flutter Question

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From: Klusmanp at

Date: Fri, 01 Nov 2002 02:25:36 UTC


  I've got an old IAC "Technical Tips Manual, Vol II" that has a good article 
on flutter (see page 112). The article shows a ground vibration test to 
determine flutter characteristics of a "Stephens-Type Monoplane" after a 
flutter induced crash/fatality of another of the same type airplane.

The testing revealed that a counterbalance horn at the tip of the aileron 
would actually be making the flutter situation worse! The article goes on to 
advise a very specific placement of a COMBINATION of counterweights to avoid 
the possibility of flutter for these airplanes.

I've been invloved in flutter issues in my work at Cessna. I'm a structures 
engineer and I've learned just enough about flutter to know that I don't know 
anything about flutter. 

Bottom line: Follow the advice of Peter's last paragraph below.

Paul Klusman
Pitts S-1S

In a message dated 10/31/02 10:21:18 AM EST, petera at writes:

<< You  make both flutter resistant with proper static balance. Normally you
 would put weight in the leading edge ahead of the hinge point in a Friese to
 obtain the proper static balance. If the hinge point is not aft of the
 leading edge, you would add a counter balance in the form of a horn (i.e the
 surface is L shaped). Alternatively you can add mass under and ahead of the
 surface hinge line with a streamlined tube of some kind angled 45 degrees or
 more forward, this is often combined with a spade.
 Other tricks that can reduce flutter are reduced hinge gap. With an offset
 hinge you can make a beautifully tight hinge gap. I.e. the cross section of
 the trailing edge '(', leading edge of the aileron '(' and hinge axis 'o'
 look like this: "((  o ". 
 Anyway you don't want to be mucking with this stuff unless you know what you
 are doing because flutter can rip a plane apart in milliseconds.


© Dr. Günther Eichhorn
Email Guenther Eichhorn