bast0n:
why on earth did sensible pilots fly this uncontrollable beast........?
A very good question old chap. The ones at Boscombe Down refused to, unfortunately other Chinook Mk2 pilots were not made aware of that. These pilots didn't want to, requesting a MK1 for the task, they were turned down and told to fly this one.
As to your technical queries I can only say that the man to have asked then was Sqn Ldr Burke, RAF Odiham Test Pilot, who had more experience than he would have wished of FADEC malfunctions and the jamming of flying controls (in various combinations of axis), but the BoI declined to call him. Perhaps others better qualified than I might address them for you now.