PPRuNe Forums - View Single Post - 12 Year Limitations on UK Piston Helicopters
Old 1st Aug 2016, 23:59
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Join Date: Feb 2006
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Cap 747 GRN24 which is page 346 on link below, is the book of words on the subject and the limitations etc. AND WE ARE TALKING UK REGISTERED HERE

CAP 747: Mandatory requirements for Airworthiness

Just to clarify Lowfat's comments, an overhauler cannot actually "zero time" an engine, only the manufacturer can do that, though an overhaul agency engine does come back in effect with nil hours and the full life cycle to run again.

You can get engines out of the factory that on the log book cert record the engine hours at as an example, 5000 hours plus, as they may have been overhauled twice and not zero timed, IE they have been overhauled to Overhaul engine limits and tolerances and not new build limits and tolerances.
Been there, seen it, and done it with the CAA, who were querying a factory overhauled Lycoming with 2780 hours on the release cert certificate and why was I fitting it!.
Even if an outside overhaul agency overhauls it to new build limits btw, he still cannot call it zero timed, but might sell it as say Diamond standard or gold standard etc and state that it is to zero timed limits.

There are three basic types of Factory engine,

New Build as it implies, new.
Zero timed as said to New specs.
Overhauled as said to overhauled limits

As for the 12 year rule on school aircraft, that is semi incorrect, the engine life as with the hours is also able to be extended in the UK under GRN24 up to a maximum of 20% subject to the engine performing and meeting certain inspection requirements.

hope that helps


Last edited by NutLoose; 2nd Aug 2016 at 00:42.
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