Originally Posted by
Rigga
Its a bit before my time but I believe early Chinook actuators were prone to jamming, the reasons for which I don’t know. However, from the D model onwards, “Dual Actuators” were fitted where if one half jammed the other would continue without loss of control. These actuators were also fitted with “Jam Simulator” buttons with which to periodically test that capability.
Rigga, aren’t you thinking of the Lower Control Actuators, as opposed to the Upper Boost Actuators on the Chinook? The BOI for ZA721 suggested a form of jam in the UBA might have contributed to the subsequent crash.
https://webarchive.nationalarchives....21_27feb87.pdf