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Hello,

Can somebody please advise me on this:

In determining a maintenance schedule, as airraft build up flight hours, they must be scheduled for their appropriate A, C, D checks etc...

If an aircraft is scheduled to undergo a "C" check at every 3000 flight hours, does this check have to be done BEFORE reaching 3000 FH or can it be done a bit after? What is the flexibility with this in terms of regulatory bodies?

Is it +10%, so must be done before 3,300 hours? Please reference where this information is stated. I'm doing my own maintenance schedule for a virtual airline and this information is crucial.

Thank you!

VikingA346

Yes. The plan is that it must be done before 3000hrs.
However getting a 5pc extension is easy, but must be applied for.

It can get complicated.
When I did a bit of planning, I looked after the Nordic East Tristars at ARN.
We had a maint opportunity for one aircraft a week.
The A check was 300 hrs, then a 2A check at 600 hrs, then an A check at 900 hrs. then a C segment at 1200hrs.
We did the A and 2A at ARN, but the C at LHR.
The trick is to use up all the hours, but not go over. If you did the A checks 50 hrs early, then you would lose 150hrs of the C check. But the aircraft could fly over 60 hrs a week. So it involved close cooperation with OPS to get the aircraft to accumulate the right hours to the next A check window.
Then one broke down, and the wrong one accumulated hours and we had to do an A check on the wrong day, which meant we had to hire loads of mechanics to get it done quicker than normal.
Not only that, we had to fly out a test set and an engineer from LHR for each 2A check.
Now try that with 40 aircraft.

If I recall correctly you are allowed to run over 10%. You don't gain the 10%. The next check limit is measured from when the runover was due. I think you also need to get FAA permission. If you do it too much they can deny the request.

Quoting VikingA346 (Thread starter): In determining a maintenance schedule, as airraft build up flight hours, they must be scheduled for their appropriate A, C, D checks etc...

That's only for airplanes that are on letter-check maintenance plans. Everything since about the mid-90's is done on the MSG3 maintenance model, which proscribes individual hours/cycles for each task. Airlines can group these into the conventional A/B/C/D checks, or do phased checks where they do a periodic visit (nightly, each weekend, whatever) with different tasks on each visit.

Quoting VikingA346 (Thread starter): If an aircraft is scheduled to undergo a "C" check at every 3000 flight hours, does this check have to be done BEFORE reaching 3000 FH or can it be done a bit after?

Depends on the maintenance plan in the airline's operation specification.

Quoting VikingA346 (Thread starter): What is the flexibility with this in terms of regulatory bodies?

Depends on the plan, the ops spec, and which regulatory body we're talking about.

Quoting VikingA346 (Thread starter): Is it +10%, so must be done before 3,300 hours?

In places that do the 10%, it's generally a hard limit.

Quoting VikingA346 (Thread starter): Please reference where this information is stated.

The OEM recommendation comes from the MPD (Maintenance Planning Document) for each model. Each airline uses this as the basis for their individual maintenance plan, which is certified as part of their operations specification. The ops spec is the official document for any particular airline. Some airlines will just say "Use the OEM maintenance plan", some will completely redo it essentially from scratch.

Quoting DALMD88 (Reply 2): If I recall correctly you are allowed to run over 10%. You don't gain the 10%. The next check limit is measured from when the runover was due.

That is my experience as well.

Tom.

At my carrier, it's a hard limit. That said, you can contact the FAA and request an extension until a certain point in time, and they're generally very cooperative, so long as you're asking something reasonable!