Jim From United States of America, joined Jul 1999, 455 posts, RR: 1 Reply 1, posted (13 years 7 months 4 days 5 hours ago) and read 601 times:
Well, let me try and explain how it is at Delta...
Maintenance is scheduled based on cycles and / or hours, depending on the unit involved. When a Delta aircraft overnights at a 'maintenance station' (Delta or contract mechanincs available; no more than 3 days apart), a 'Layover check' is performed. Fuids, cabin gripes, minor daily maintenance are targeted.
After so many layovers (usually about 30ish depending on type) the aircraft requires a 'Service check', which is a bit more indepth.
After so many service checks, the aircraft is scheduled into the hangar for a Mid-Visit (MV). This is heavy maintenance requiring up to 14 days, again depending on type, and what type problems are found. This is about 3 1/2 to 4 years SMOH.
After another 3 1/2 to 4 years, the aircraft returns to the hangar for a Heavy Maintenance Visit (HMV). This is equivalent to a 'zero time', and can take up to 30 days depending on type. Everything that can be disassembled and is required to be is removed, reworked, and reinstalled.
Breaking up this routine are visits to the hangar for Engineering Orders (EOs) which the line cannot complete due to time / manpower, or paint shop visits, and of course repairs of a non-routine nature which either require engineering input or in-depth troubleshooting, as well as ageing-aircraft Corrosion Visits on the 727, 737-200, and L1011 fleets. There are 4 CVs per HMV cycle, and they are scheduled to be performed concurrent with service checks / MVs.
As you can see, there is a lot of room for overlapping of maintenance. For example, during an HMV, there may be four or five card decks issued to open up the vertical fin, due to the fact that a HMV, MV, CV, and service check are all being done at the same time. We open the same panels (mostly), and have to sign off each card independantly.
The real fun is when we are 10 days into a twenty day HMV, and scheduling 'discovers' that a MV is also due. We either have to open up panels already closed or show the inspector where the work was previously accomplished. I have spent hours literally proving that everything has been accomplished!
I hope this isn't too much information, but in a nutshell, transport category aircraft are ALMOST ALWAYS being inspected, so there isn't a need for a dedicated 100hr,
Purdue Cadet From , joined Dec 1969, posts, RR: Reply 6, posted (13 years 7 months 2 days 11 hours ago) and read 566 times:
Look at it this way, Neil... Airlines do just like Purdue, only a lot more in depth. You probably don't know Purdue's maintenance system since you're in admin., but we do progressive maintenance here, too. We do a routine inspection every 50 hours, which is basically an oil change. Every 100 hours, we do an event, which is a more indepth inspection of a particular part of the plane. Four events cover the entire aircraft, and every set of four events is called a cycle, which is the equivalent of an annual inspection. This system is in place of 100 hr. and annual inspections, and was approved by the FAA as a progressive maintenance system. In the same way, each airline must have its specific system of progressive maintenance approved by the FAA.