Use of extension periods

[212man]

I'm interested to know what the standard practices are for the use of the 10% tolerance in relation to maintenance checks hours is. e.g a 500 hour check having a 50 hour extension available in the AMP/AMM. Do you treat this buffer as yours to use as a rightm, or do you have to gain an approval through a formal QA/QC sign off process? Thanks!

[QA1]

In my organisation in the UK, conditions and permitted periods that can be applied using a variation to a maintenance task are laid down in the AMP.

Maintenance Planning apply for a variation for consideration by Quality, if it meets the AMP criteria, unforeseen circumstances, non-mandatory, not ultimate life etc. it is approved.

Once granted, all variations are notified to the national authority.

[wrench1]

On my side of the pond, if operating under a Part 135 (Air Taxi) certificate the use of extensions will/should be spelled out in the submitted ops specs or 135 maintenance manual. For example, in the EC135 AMM it offers a plus/minus variance in numerous inspections that do not penalize the operator if complied with X hrs before or X hrs after the standard schedule of say 400hrs. However, in order to use that program it must be indicated in the ops specs/manual of record. It is normally not a field function to use it or not unless your a private operator which is another entirely different scenario.


On a side note, some generic extensions found in AD's or in a regulatory format are usually for "scheduling" said aircraft remaining flight time to get to a facility to comply with said maintenance--but not to be used for revenue flights. But this example is a big gray area.


W1

[Kinger]

NZ allows extension unless specifically prohibited. (ADs, ELT, S mode, 24month avionic checks etc.)
My old Part 43 boss ran his whole life on the 10%, pretty pointless with the reforecast date.