Non-feathering multis
The Caldwell controllable non-feathering prop received the Collier Trophy for technical achievement in 1933. Boeing, Lockheed, Douglas etc. multis certificated before this all used this counter-weight actuated (i.e. non-feathering) prop. They were soon retrofitted with Hydromatics (Hamilton Standard design) within a year or two; it made a significant boost in OEI performance.
Last edited by barit1; 5th Mar 2017 at 17:54.