Ex52tech From United States of America, joined Dec 2006, 559 posts, RR: 1 Reply 2, posted (4 years 3 weeks 2 days 10 hours ago) and read 3693 times:
It really depends on how the airline sets up it's maintenance program. Lettered checks such as A-D checks, the heavy checks C's and D's. C checks are roughly every 4,000 hours, which is close to one year or more. D checks at the airline where I worked were about every 4 years, so around 16,000 to 20,000 hours. But every airline is different.
If you are operating on a segmented check system......Light, Heavy, Transition, or Major checks, then the intervals are different. Lights were similar to a B check, and were scheduled for 7-11 days in hangar, less time for the smaller airplanes. A segment of the airplane was inspected, these were accomplished every few months, with a heavy check being accomplished every other year. Transitions were only used when an aircraft was leaving the A-D check schedule going into the segmented check schedule. The major checks were very much like a D check but the interval for these checks was out farther than a D check.
The theory behind the segmented check was to have the airplane in service longer, with less extended hangar visits. My personal opinion of this system is that it works well with airplanes that are accumulating hours with less cycles ( long haulers).
I worked both systems and feel that if you are cycling an airplane more, the A-D check system works better. After we switched over to the segmented schedule we had more unscheduled events on the high cycle airplanes, to the point where we had to develop an intermediate maintenance crew, who handled those problems that were too involved for the line crews, and would take to many people away from the heavy maintenance crews for to long.
"Saddest thing I ever witnessed....an airplane being scrapped"
RoseFlyer From United States of America, joined Feb 2004, 8737 posts, RR: 52 Reply 4, posted (4 years 3 weeks 2 days 1 hour ago) and read 3552 times:
A 737 can go 6 years before its first check that requires more than overnight service. Yes that means that a 737 can fly every day for 6 years straight, and some famous low cost carriers do that.
The 787 is designed to be able to go 10 years before the first major overhaul that requires taking it out of service for more than overnight. The 787 maintenance plans have eliminated the traditional A, B, C and D checks and replaced them with a different form of scheduled maintenance.
If you have never designed an airplane part before, let the real designers do the work!
TristarSteve From Sweden, joined Nov 2005, 3687 posts, RR: 34 Reply 5, posted (4 years 3 weeks 1 day 18 hours ago) and read 3447 times:
Quoting RoseFlyer (Reply 4): A 737 can go 6 years before its first check that requires more than overnight service. Yes that means that a 737 can fly every day for 6 years straight, and some famous low cost carriers do that.
Sounds good, but has anyone ever done that?
The British CAA requires that A checks are performed in a hangar. This happens about every 4 months. We schedule our A checks to be in the hangar for 24hrs, so that other maintenance that takes longer than overnight can be cleared up as well.
I once worked for a charter airline with B757 that tried to schedule them 0600-2400 every day. After a week we had to change an engine bleed valve. We refused to guarantee to do it overnight,( it is very difficult to change with limited access) so it was deferred for ages until they could get the aircraft off service one day.
The next summer they scheduled some maint time into the system.
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 6, posted (4 years 3 weeks 1 day 14 hours ago) and read 3409 times:
Quoting RoseFlyer (Reply 4): The 787 maintenance plans have eliminated the traditional A, B, C and D checks and replaced them with a different form of scheduled maintenance.
Quoting RoseFlyer (Reply 4):
A 737 can go 6 years before its first check that requires more than overnight service. Yes that means that a 737 can fly every day for 6 years straight, and some famous low cost carriers do that.
Sounds good, but has anyone ever done that?
The British CAA requires that A checks are performed in a hangar. This happens about every 4 months. We schedule our A checks to be in the hangar for 24hrs, so that other maintenance that takes longer than overnight can be cleared up as well.
I know at DL we opted to do a PSV progressive check system on the 737NG. It gets a hangar visit about every 18 months I think. They vary in length from 3/4 days up to 3 weeks I think. I don't do heavy check so my numbers may be a little off. We also do Service Checks ( A check) at line stations. I think they fall every 500 hrs. We do not have to do them in a hangar. Ours are set up to be done on a regular overnight time frame.
Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 8, posted (4 years 3 weeks 1 day 2 hours ago) and read 3300 times:
Quoting HAWK21M (Reply 6):
Quoting RoseFlyer (Reply 4):
The 787 maintenance plans have eliminated the traditional A, B, C and D checks and replaced them with a different form of scheduled maintenance.
What Mx schedules are these?
I think it's a phased check like the 737NG uses. Basically, all the tasks just have defined intervals but they're independant of all the other tasks. The airline can choose to do them all at once (major hanger visit) or do little bits and pieces every night and never take it out of service until they have to do something that takes a long time.
Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 11, posted (4 years 2 weeks 6 days 20 hours ago) and read 3131 times:
Quoting HAWK21m (Reply 10):
Quoting Tdscanuck (Reply 8):
I think it's a phased check like the 737NG uses.
Are you talking MSG-3 here?
Sort of...MSG-3 is a method of identifying what maintenance checks need to be done (and what interval). If you have a pre-MSG-3 airplane, it's probably certified with letter checks and it would be a lot of work to do anything else. A post-MSG-3 airplane should have intervals on each check and phased check is a way of sequencing your tasks to support different maintenance schedules.
For example, an MSG-2 (or earlier) or MSG-3 maintenance plan based on letter checks might say (completely at random):
A check: every 300 hours
B check: every 600 hours
C check: every 2000 hours
D check: every 5000 hours
And then, for each check, it would list all the tasks in that check. So, if the A check had 24 hours of tasks, you'd have to put the plane out of service for 24 hours to do the A check.
An MSG-3 maintenance plan wouldn't typically reference letter checks, it would just list a bunch of tasks with intervals (some might be 300 hours, some might be 600, some might be 900, some might be 2000).
An operator could schedule those tasks into classic letter checks, do an A check every 300 hours, and do all the 300 hour tasks at that time (plus any 600 or 900 hours tasks that were due at the same time). But they could also stagger all of those tasks so that, say, you did 2 hours of work each night. Each task would be getting done at its appropriate interval, but it wouldn't be connected to the performance of any other task. This latter version is typically what is meant by a "phased check." Over the course of a couple of weeks of short overnight work, you'd accomplish all the work that would previously be done in one intensive check.
For operators whose airplanes go "home" every night, phased checks are nice because the airplane is in revenue service for more days and they've got the resources available to do all the different tasks. For operators who operate out of a lot of remote bases, more classical checks may be nice because they can send the plane out of the hanger and mostly ignore it except for daily service until the checks come due again.
Avt007 From Canada, joined Jul 2000, 2131 posts, RR: 5 Reply 12, posted (4 years 2 weeks 6 days 2 hours ago) and read 3042 times:
Some of these "cool" systems suck from an AMEs point of view. For a while at one carrier I worked at, we went to an alternate check system designed to reduce heavy maintenance visits. It may have reduced heavy time, but it definitely increased line maintenance workload significantly. Efficiency was way down too. For example, one night we'd pull all the seats out of the RH side of the cabin, do underfloor and sidewall inspections, and put them back. The next night would be the LH side. Often the task would have to repeated, because if you found a problem, it went back together while you waited for parts, and on the 3rd night, you'd yank it all apart again. That system didn't last long. That carrier is now back to a traditional heavy check system.
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 13, posted (4 years 2 weeks 5 days 17 hours ago) and read 2994 times:
Quoting Tdscanuck (Reply 11): If you have a pre-MSG-3 airplane, it's probably certified with letter checks and it would be a lot of work to do anything else
There is an interm check that can be done while transitting from Non MSG3 to MSG3 schedule.This ensures no item is unchecked while adapting the new schedule.
regds
MEL
Ex52tech From United States of America, joined Dec 2006, 559 posts, RR: 1 Reply 14, posted (4 years 2 weeks 3 days 22 hours ago) and read 2880 times:
Quoting HAWK21M (Reply 13): There is an interm check that can be done while transitting from Non MSG3 to MSG3 schedule.This ensures no item is unchecked while adapting the new schedule.
We did the same thing with our DC-10s, and some of the other aircraft in the fleet. We used an interim, or transition check exactly as you are stating, when entering the MSG-3 program.
"Saddest thing I ever witnessed....an airplane being scrapped"
HAWK21M From India, joined Jan 2001, 31201 posts, RR: 58 Reply 15, posted (4 years 2 weeks 3 days 18 hours ago) and read 2850 times:
Quoting Ex52tech (Reply 14): We did the same thing with our DC-10s, and some of the other aircraft in the fleet. We used an interim, or transition check exactly as you are stating, when entering the MSG-3 program.
A nice article for those interested in knowning about MSG-3.
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