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A, B, C, D Checks? Explain?

Sat Feb 07, 2009 10:11 pm


Can somebody please explain the difference between A, B, C, D Checks and how often each of the checks has to take place?


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Joined: Wed Dec 06, 2006 2:28 pm

RE: A, B, C, D Checks? Explain?

Sat Feb 07, 2009 11:49 pm

Each airline sets up the criteria for each one of those checks in conjunction with the manufacturers recomendations, and their operational needs, the criteria is not set in stone. Some airlines do not use the A-D check system anymore.

For instance the airline that I worked for when they were using that system would accomplish an A check (overnight) at least once every 5 days. The B check every 3 months they usually took 1 or 2 days. The C check on a wide body every 4,000 flt hours, in anywhere from 20 to 30 days, and incorporate a 1/4 D check with each C. The C checks were accomplished every 14 months, on average, that way there was never the need for a D check. The D checks were supposidly to be done every 5 years on average.
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RE: A, B, C, D Checks? Explain?

Sun Feb 08, 2009 11:02 am

The aircraft manufacturer produces a Maintenance Planning Document. This will detail the maint required for each part.
Like Engine oil level...check each transit
Main undercarriage overhaul....Every 20000 landings.
And everything else in between.
The manufacturer will package these checks into groups which run from Transit check to D check.
The airline will either accept the packages and use them, or construct its own. This really depends on how it operates. If your aircraft nightstops at base every night, why not do the maint in small 6 hour packages.
We once did overnight maint only, with a hangar input every 3 years.
The problem then is some jobs take longer than 6 hours. So you need a day long input for these jobs. The advantage of using the manufacturers packages, is when you sell the aircraft it is already aligned to the norm.
An airline that flies summer charters, will ensure that all maint is done in the winter, even packaging A checks so they can be done on long turnrounds in the summer so the aircraft can fly day and night for 8 months.

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