Tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 1, posted (5 years 10 months 2 weeks 5 days 2 hours ago) and read 6215 times:
Quoting N62NA (Thread starter): When the 777 first came out, I remember reading an article in Airliners magazine that stated that in it's first year, the 777 had a 99%+ dispatch reliability record.
Was I just unlucky, or are the AA 777s, heaven forbid, sinking to the level of the AA A300 reliability?
AA has 47 777's, so they're flying about 100 flights per day with their fleet. That means they should have about 1 maintenance delay per day on their 777's (with 99% dispatch reliability). So I think you're just unlucky, absent other info.
TristarSteve From Sweden, joined Nov 2005, 4069 posts, RR: 33
Reply 7, posted (5 years 10 months 2 weeks 2 days 17 hours ago) and read 5725 times:
Quoting LAXintl (Reply 2): Well for the 12months ending 9/08, AA's annual 777 fleet reliabilty stood at 98.25% with an average daily utilization of 11.25hrs.
This is somewhat on the lower end of user experiences, and utilization. Industry average for the 12mos on the -200ER was 99.06%.
You have to be careful with these figures, the word reliability can mean different things to different folks.
We measure delays for technical reasons. This includes all aircraft that are late (And one minute late is late) due maint. Some of these are just that the technician was busy somewhere else and arrived late to sign off the aircraft! It does not include aircraft that are damaged. Bird strikes and lightning inspections don't count. For main base the figure is around 98.5pc, and on the line about 99.2pc(operated on time). Main base is lower because the MEL is more restrictive, and more work is carried out that can delay the aircraft.
i.e. a major IFE failure would be worked at main base, and a delay taken to fix it., while a line stn with no spares would not work it.
Also weather can affect the numbers! A lot of systems, antice, pitot heat, windscreen heat etc are allowable in the MEL in warm climates but not in the cold.
Reliability can mean number of flights operated, i.e. 99pc reliability means that 1 flight in 100 is canx.
The industry standard for delay reporting is flights that are over 15mins late.
It is very difficult to compare if you don't know the exact criteria used.
If you've never looked at one before, you should read the intro that explains what the columns and codes mean. Basically, the first column identifies the item by ATA code, the second column shows how many items are installed, the third shows how many need to be working, and the fourth provides notes.
Quoting Doug_or (Reply 9): so does 99% mean it goes out on time 99% of the time or it completes the flight 99% of the time?
It means it leaves on time (within 15 minutes) 99% of the time. Completion percentage is a different measurement. Many airlines are shifting from dispatch reliability to availability, since that's a better measure of airplane reliability.