What is aircraft D-check?

Answer 1

This is by far the most comprehensive and demanding check for an airplane. It is also known as a Heavy Maintenance Visit (HMV). This check occurs approximately every 5 years. It is a check that, more or less, takes the entire airplane apart for inspection and overhaul. Also, if required, the paint may need to be completely removed for further inspection on the fuselage metal skin. Such a check will usually demand around 40,000 man-hours and it can generally take up to 2 months to complete, depending on the aircraft and the number of technicians involved. It also requires the most space of all maintenance checks, and as such must be performed at a suitable maintenance base. Given the requirements of this check and the tremendous effort involved in it, it is also the most expensive maintenance check of all, with total costs for a single visit being well within the million-dollar range.

Because of the nature and the cost of such a check, most airlines especially those with a large fleet have to plan D Checks for their aircraft years in advance. Ofttimes, older aircraft being phased out of a particular airline's fleet are either stored or scrapped upon reaching their next D Check, due to the high costs involved in it in comparison to the aircraft's value. On average, a commercial aircraft undergoes 2--3 D Checks before it is retired. Many Maintenance, Repair and Overhaul (MRO) shops state that it is virtually impossible to perform a D Check profitably at a shop located within the United States. As such, only few of these shops offer D checks.