Originally Posted by
Peter47
Are they inherently unreliable or maintained to a lower standard than jet engines (maintenance costs money and they are less safety critical than engines)?
Quite a high proportion of the BA747s I've been have had faulty APUs and judging by the number of air start units I;ve seen around its not just a BA problem.
I was delayed for over 30 mins at Toronto a couple of years ago as the ground start unit couldn't get the RB211 going on its own and they had to get a second. I've seen calculations for the cost of delays, though I'm not entirely sure I believe them.
As a matter of interest could some techie tell me:
- What is the main problems, presumably like the engines its the things that hang on the APU rather than the turbine itself?
- if the APU were on the MEL (I knows its not) and despatch critical could you complete a typical repair in a 2 hr turnaround?
- are there spares pools around the world for APU components?
for large turbofan engines such an RB211 or even a JT8 on a MD80/DC9 or CFM56 on a 737/A320 if the APU is U/S one needs both a GPU for electrical power, plus an air start unit as well to start the engines by providing air to turn the fan & engine before the fuel is put in then ignition