Originally Posted by
Allan Lupton
We were always a bit puzzled that the One-Eleven was so much noisier than our Tridents. I think I recall a member of the Weybridge opposition (later colleagues) telling us that most of the One-Eleven's noise was from the air-driven CSDs in which case a hush kit would indeed make no difference.
Quite soon after One-Elevens entered service it was found that acoustic vibration was cracking the horizontal stabiliser structure. The nozzles were replaced to limit the problem. Noise was actually much increased and some power lost I recall. The One-Eleven CSD was actually a CSDS which incorporated an air driven starter. It was the running down of the air driven part which gave the characteristic “whoop, whoop” noise at the end of the engine start cycle. Whatever possessed them to install such a heavy, unreliable contraption will never be known. Nothing like it has been seen since as far as I know.
Trident-wise, I seem to recall early mornings hearing Tridents running engines post-maintenance at Hatton Cross from my house in Hersham. Maybe seven or eight miles away. The aircraft on the Cullum mufflers too!