REFLECTOR: How Fast-flutter

[Ron Brown]

Here's one reference (and another opinion):

Doing a Google search (control surface flutter) found this article
http://www.auf.asn.au/groundschool/flutter.html#limiting_airspeeds

which states that IAS should be reduced as altitude is increased to limit
the probability of flutter.

Ronnie


----- Original Message ----- 
From: "Chuck Harbert" <c.harbert at comcast.net>
To: <reflector at tvbf.org>
Cc: "Steve Murphree" <pi151 at aol.com>
Sent: Thursday, March 22, 2007 1:11 PM
Subject: REFLECTOR: How Fast-flutter


>I think we've covered this a couple times before, but as I recall, the gist
> of it was that the IAS is the thing you need to watch, but that TAS also
> affects what the actual forces that can induce flutter. IOW is really 
> both,
> but for practical purposes IAS is the one you need to watch. If the Vne
> (IAS) is 200 kts, you better be careful reaching or exceeding it, 
> especially
> at higher altitudes (at higher TAS), because the air load change is not
> linear. The IAS Vne reduces slightly (<5%) at higher altitudes as I
> understand it.
>
> I think the more important point is what part of the V is likely to 
> flutter.
> Flutter is basically an undamped resonant vibration of a movable flight
> control surface caused by air pressure loadings. From what I've read and 
> the
> responses I've seen on the Reflector, the rudders are the most likely (in 
> a
> turn), assuming you've properly balanced the elevators and ailerons. I
> believe that the rudder in a turn is the weak point because it is only
> positively controlled in one direction (spring loaded in the other
> direction) thus allowing high airloads to overcome the spring pressure 
> load.
>
> The big problem with flutter is that once it starts it can very rapidly 
> rip
> the control surface from the plane which can result in a loss of control. 
> I
> think "stabbing" the controls at high speed is intended to see if flutter
> shows up because it can be induced with a airfoil change. If you get a
> flutter indication at less than Vne, you need to "fix it" before you 
> attempt
> higher speeds.
>
>
>
>
>>  From: "Tom Martino" <tmartino at troubleshooter.com>
>> Date: 2007/03/18 Sun PM 11:22:24 EST
>> To: "Velocity List" <reflector at tvbf.org>
>> Subject: REFLECTOR: HOW FAST?
>>
>> OK, in speed tests this weekend, I was able to true out at 210 knots
>> pretty consistently.  I was at 23 inches and 2400 RPM.  I still had
>> throttle travel left.  Flight controls were solid and no sign of
>> flutter.  Should I push it even further?  At what point do I know I have
>> gone far enough?
>>
>> Tom Martino
>> 173 Elite RG - 300 HP (IO-540)
>>
>
>
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