Adour Mk106
I would like confirm or challenge the comments in the associated threads
The Mk106 was a maintenance spend to save programme - improved reliabilty. The engine was derated to meet this requirement, albeit the derated engine gave more thrust than the Mk104.
The Mk106 was a direct replacment for the Mk104 - minimum changes to aircraft to accommodate the engine
Regards weight and ballast. The ballast modification was necessary to address a number issues and not just the engine. During the life of the aircraft CofG had moved aft (changes in weapons fit and airframe modifications). I some configurtations the Mk104 aircraft was operating beyond the aft CofG limit. Hence, the opportunity was taken to address all the CofG issues concurrent with fitting the heavier Mk106 engine.
There were no turbine failures.
The core engine exceeded the reliability targets and the expected saving in engine maintenance was achieved. As far as I can recall no engines were ever changed for core engine problems (excluding FOD).
There were a few incidents of heat damage to components in the reheat module (Module 12). This problem was known and understood but there were no funds available to introduce a full length heat shield within the jet pipe.
The feedback I had from Pilots was excellent.
Even with the few reheat damage incidents, there was still a stepped improvement in reliability.