off topic barnfind

[petehoovie]

"His most fascinating assignment was flying the P-63 Kingcobra "Pinball." The aircraft had extra aluminum armor and was equipped with sensors that recorded the hits of special bullets ... fired by student gunners training in B-17's. A red light in the prop hub would also flash to indicate hits thus "Pinball."

 

[Karl]

Several different things can cause the difference in sound, the most common of which might be propeller blade style, number of blades, blade length, pitch setting, RPM, and even the aerodynamic load on the propeller at any given time. Also, the material the blades are made from (some Spit propellers have wooden core blades that special machinery pressed a hard metal mesh coating and cellulose sheet over the entire propeller) can have an effect on resonance of the blades at speed. Some earlier Spitfires had three-bladed propellers.



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The blades on the local restored Spitfire are made in Germany -apparrently the only source -Ironic . Like everything for it expensive ++ However most things are obtainable (at a price) the last I heard the only thing that they were really worried about finding replacements for if needed were the hydraulic bladders for the brakes .