From: email@example.com (Ed Hahn) Organization: The MITRE Corporation, McLean, Va. Date: 16 Feb 96 04:33:31 References: 1
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firstname.lastname@example.org writes: > Just curious as specific differences between the different types of > checks done on commercial aircraft. Well, first off there are substantial (if not exactly major) differences between the various aircraft types as to what goes on during each of these checks, or what they are even called, for that matter. That said, at one airline that I worked at, the periodic maintenance services were (from most to least frequent) for narrowbodies: Preflight Check - before every flight First Flight of the Day Check - before the First Flight of the Day Periodic Service checks (PS Check) - about every 10 flight hours A Checks - about every 30-40 flight hours (e.g. 1 every 3 days or so) B Checks - about every 100-200 flight hours (e.g. 1 every 2-3 weeks) C Checks - about every 3000 flight hours (depending on type) (e.g. about 1 per year) Heavy C Checks - about every 15000 flight hours (e.g. about 1 every three to four years). The D Check was not a standard check at this airline. The frequent checks (i.e. everything before B Check on the above list) are "check the fluid levels"-"check the tire pressure"-"fill the potable water" kind of checks - i.e. nothing that couldn't be done at a majority of airports. B Checks had more inspections performed, and generally take the aircraft out of service for a day or so. These are generally done at a smaller number of airports. C Checks are where major items are inspected and replaced, and take the aircraft out of service for about 5 days or so. Overhaul and engineering modifications to aircraft are also performed here (i.e. approved changes to the aircraft configuration - not just topping off/replacing fluids or inspections). Depending on the aircraft, a flight test must occur after a "C" check, which performs specific routine and non-routine in-flight tests to ensure that systems operate (e.g. ensure cabin pressure relief valves work as operated, ensure that the emergency masks drop from overhead when the cabin pressure is decreased, fuel dumping, etc.) Aircraft painting may also happen here as needed. This check usually only occurs at one or maybe two places for a given airframe in an airline's system. Heavy Cs are where major overhaul work is performed, such as control surface refurbishing, major structural modifications. These can take from 4 to 6 weeks to accomplish. Now then, the above checks are only a skeleton. Many of the newer aircraft are coming out with different kinds of checks, such as Major Base Visits rather than C Checks. Also, certain aircraft (such as widebodies) may have more thorough C checks, without having Heavy Cs. Finally, each airline's maintenance program is individually approved by the FAA (based on the airframe manufacturers recommendations), so significant differences can and do occur between different airline's maintenance program layout (although they are all approved to meet a minimum level). This is all of my recollection from a couple of years ago, and only reflects one person at one airline's perspective (I was an avionics engineer, so some of the more structures / hydraulics kinds of things were not my area of specialty). Any errors in the above are mine. ed -------- Ed Hahn | email@example.com | (703) 883-5988 -------- The above comment reflects the opinions of the author, and does not constitute endorsement or implied warranty by the MITRE Corporation. Really, I wouldn't kid you about a thing like this.