PPRuNe Forums - View Single Post - Positive static spiral stability???
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Old 20th November 2001 | 23:18
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Genghis the Engineer
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Yes.

Spiral stability is the tendency of an aircraft to increase or reduce bank angle once disturbed.

So, an aircraft with positive spiral stability tends to roll wings level from, say, a 30° bank. If negative, it increases the angle of bank, and if neutral it stays where you put it.

In training aircraft positive spiral stability is generally regarded as a good thing. In an Airbus, I'd suggest it's probably not too important so long as it's not actually negative. In something like a Pitts, you'd want it neutral or negative.

The standard flight test technique is to roll about 15° with the rudder (keep the ailerons central), release the controls and start a stopwatch. The time to half or double bank angle is recorded in the FTR - if it takes more than 10 seconds to do either, consider it neutral.

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