ROLL STABILITY
•Sweep forward*, as in the K7 and K13 leads to instability
–therefore it is counteracted with exaggerated dihedral
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•‘Pendulum’ stability exists with very high wing aircraft (e.g. T21)
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•Anhedral, as in the Harrier (which we used to have!), leads to instability
–and is counteracted with lots of sweep back
•But what the heck !!!
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•Sweepback may lead to Dutch Roll
–which again is countered with anhedral
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•Gliders -generally speaking-are UNSTABLE in roll
–i.e. they diverge into a spiral dive
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•Use of Airbrakes tends to increase roll stability
•(see Part 1 of these lectures)
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•     *Sweep forward in K13, Bocian etc is a design feature to get the back seat pilot close to the C of G so that their weight doesn’t have much effect (and the machine can be flown solo from the front) – but still give the back seat pilot a view.
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