Aerodynamic flutter can develop with great speed and quickly destroy your aircraft. Here’s why, and what you can do about it.
Beechcraft’s venerable V-tail Bonanza experienced a few flutter-related incidents and accidents before a series of Airworthiness Directives required inspections and strengthening of its empennage.
by Jeff Pardo
You’re descending at a relatively high speed in calm air and, since there was no forecast for and little chance of turbulence, you let the airspeed climb into the yellow arc. Then you hear a buzzing noise. You might think that one or more fasteners have come loose, perhaps on the cowling—or you might imagine a bee, wasp or some other stowaway insect as the source. One thing is for sure; the sound you hear probably isn’t a stuck microphone. So what’s going on? Well, you had better slow down, because that buzz you hear could be your ailerons about to go fully into “auto-flail mode.”
The V-tail Bonanza came under close scrutiny in the mid-1980s following a series of in-flight breakups. Several airworthiness directives were issued and a special study was done by the FAA and the Department of Transportation, which resulted in a stabilizer reinforcement kit at the root of the V-tail. After the installation of the kit, the in-flight breakups decreased dramatically.
It should be noted that the V-tail Bonanza's center-of-gravity envelope is relatively narrow, and loss of control with aft CG in IMC conditions could be contributing factors in several of these accidents. Additionally, the balancing of the tail control surfaces is critical to avoid aerodynamic flutter. Unbalanced control surfaces continue to cause problems, so it is essential, after the aircraft is painted or work done on the tail, to check that the surfaces are exactly in tolerance.
Edited by Belize-N-Us (06/18/08 12:45 PM)
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