Buzzing noise at high speed....
06-19-2003, 12:30 AM
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Buzzing noise at high speed....
You're descending at a relatively high speed in calm air, and since there was no forecast for nor little chance of turbulence, you let the airspeed climb into the yellow arc, but fail to keep your attention focused on the airspeed indicator. Then you hear this buzzing noise. What might that mean?
1. You probably had a bee, wasp, or other insect as a stowaway.
2. Your mike is stuck.
3. One or more Dzus fasteners have come loose, most likely on the cowling.
4. You'd better slow down!
Answer: Although aileron buzz usually exists in transonic airplanes, and is generally not an automatic precursor to flutter, it can precede structural failure in even an ultralight aircraft. True, the ailerons of certificated lightplanes are not supposed to exhibit aileron buzz even at never-exceed speed (red line), but it can--and has--happened. The reason can be an imbalance condition or problem in the control cables, for example. The "buzz" usually refers to a rapid oscillation of a control surface, most often an aileron, which doesn't usually attain a large amplitude or become dangerous, and is caused in most cases by shock-induced separation of the boundary layer at high transonic speeds. Nonetheless, you have just become a test pilot, and the only correct thing to do is to slow down (choice D). Again, such events have usually occurred with high speed operations and at high altitudes.
from iPilot Newsletter
1. You probably had a bee, wasp, or other insect as a stowaway.
2. Your mike is stuck.
3. One or more Dzus fasteners have come loose, most likely on the cowling.
4. You'd better slow down!
Answer: Although aileron buzz usually exists in transonic airplanes, and is generally not an automatic precursor to flutter, it can precede structural failure in even an ultralight aircraft. True, the ailerons of certificated lightplanes are not supposed to exhibit aileron buzz even at never-exceed speed (red line), but it can--and has--happened. The reason can be an imbalance condition or problem in the control cables, for example. The "buzz" usually refers to a rapid oscillation of a control surface, most often an aileron, which doesn't usually attain a large amplitude or become dangerous, and is caused in most cases by shock-induced separation of the boundary layer at high transonic speeds. Nonetheless, you have just become a test pilot, and the only correct thing to do is to slow down (choice D). Again, such events have usually occurred with high speed operations and at high altitudes.
from iPilot Newsletter
