Quote:
Originally Posted by winny
The weight was built into the elevator circuit, in simple terms it was used to counteract the effect of light elevators and high g forces. The weight was effected by the g forces so if there was a high load the elevators needed more force to move them.
It was fitted to spitfires to solve the problem of spitfires breaking up when pulling out of a high speed dive, which was a known, and big problem at the time.
Because the elevators were so light pilots were pulling out of the dives and over stressing the airframe. There were loads of examples of this happening.
So basically the more g that was pulled the harder the elevators became to move. As far as I know it had nothing to do with any instability.
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As I understand and from RAE papers the installations of bob weights to the elevator and longitudal instability were related. To my best understanding - and do correct me if I am wrong - instability means that if you pull the controls (in whatever direction), the aircraft will not only change its roll/pitch/yaw to the extent of control movement, but also keep increasing it on its own, as if there were some kind of inertia/acceleration going on. This was noted on Spitfire Vs by the British.
By adding the bob weights and making the controls progressively harder to move for greater deflections, it made this increased acceleration problem more difficult to encounter.. It did not cure the instability itself, which was an inherent aerodynamic feature of the design, but made it harder for the pilot to make it happen.