I'm hoping that someone will be able to help out with this question, or at least point me in the right direction.
We have a Robin DR400/180Remorqueur that was originally built in 1975, but fully rebuilt by Robin in 1996, when it was fitted with a Gomolzig silencer kit. This is now completely knackered, and needs to be replaced. We want to replace it with the standard stub exhaust of the type that came with the aircraft originally but we've been told that we need design approval and it would be classed as a major mod, with all the hassle and cost that that would entail. This seems odd, given that a stub exhaust was the original fit, and I would have thought that it'd just be a case of reverting to original spec with little formality. After all, there are loads of other Remos in the UK with standard exhausts but I can't seem to get a straight answer on the subject, and so does anyone know the answer to this and, if possible, can they point me to the official EASA or CAA words on the matter (if such a document exists)? Trying to find the definitive answer in all the EASA and CAA bumf has almost got me to the wrist slitting stage!