I have a 737 classic on one of the older worlds.
This plane has a maintenance ratio of 116.9%.
There is every-day maintenance window of 3 hours 34 minutes, and in addition to that, 3x per week additional window of 5 hours 18 minutes.
This particular aircraft has been in service since Dec 1, so it's been 12 days, flying without incidents.
Today it was grounded because of "insufficient condition".
I really do not understand this, why?
Seems like that two days in a row with only 3h 34min of maintenance brought the condition down to below 50%...
Yes that is a possibility, but why didn't this happen before? It has been flying for 12 days no, so it passed through at least one week-long cycle... I wonder, that if this is the problem, why wasn't the plane grounded also last week on the same day? This is what has me confused....
It looks like with the 3h34min you will not get back to 100% so each time the maintanance will bring it back to 90% for example and then to 85% and so on ..... sometimes it takes a while untill it is not working anymore ... it also depends on the cycles..... maybe it is doing a lot of short sectors that will have a bigger impact on the maintenance that need to be done then if you do longer flights ..... for a 737 you normally need 4-4,5hrs each day.
Who is the contracted maintenance company? I made horrible experiences after a switch to a cheaper contractor because the new contractor took the money but they weren´t able to keep my hard-working aircraft airworthy. The condition deteriorated gradually.
Maintenance is the system default company.
@Benjamin… but shouldn’t the large maintenance window bring up the plane all the way to 100%? I mean, if the maintenance ratio is 117% isn’t there a moment (a time point) during the week’s schedule that the aircraft condition reaches 100%?
The default one is crap ...... the two once that are working best are Avia and Hellvetic ....... and it depands if it is bringing you back to 100% that you have to monitor. You can have a ratio of 120% but each time you have a slowly decrease in your maintenance by lets say 5% per week so your plane can be grounded after 10 weeks .... the best and easiest thing to do for me is simply plan for a 737 a single block with 4,5 hrs per day.
Benjamin, thanks for the information. I thought it was sufficient to have a maintenance ratio of over 100% (even 100.1%) and to have maintenance done at least every day. I guess it was not the case here ...
Yes that is a possibility, but why didn't this happen before? It has been flying for 12 days no, so it passed through at least one week-long cycle... I wonder, that if this is the problem, why wasn't the plane grounded also last week on the same day? This is what has me confused....
You say that you have three additional large windows of maint each week. There is the simple reason.
Having three of those large maint windows leaves you with four days each week without.
Looking at ONE week stand alone you're perfectly ok with your ratio of 117%, but you always have two days in a row without this maint window - say Sunday and Monday. Your airframe apparently wont recover after two days of only 3,56h maint.
Make it four slightly shorter maint windows instead of three long ones and all is good.
Just get a contractor with better quality This would eliminate the annoyance.