Originally Posted by
FlightDetent
I'd let the metallurgists take care of that. Or better yet, delay the APU start by those 3 minutes if you don't need the bleed yet and save the planet a little. 1 min = how much, 3 USD worth? People starting APU early to 'give more time to stabilize' fleetwide sounds like not overly bright SOHabit.
The EGT increase by introducing bleed demand is marked but whether or not it is real-life damaging is very debatable. Keep the EXT PWR to connect to mitigate that, why not. 'Over the lifetime' is academical truth because the supposed savings only arrive with the overhauls.
No dispute with the other reasons, your honour.
Simple rule on which hairs to split: Does this improve anyting for the given day/sector?
such as
- fuel burn
- noise
- workload
- complexity
- customer experience
- ontime performance
in my opinion having used the first procedure in my first post (which is even more complicated than airbus 3 mins wait rule) and the new airline one with no delay rule.
3 mins procedure/ avail 1 min, bleed on packs off 1 min, then packs on
fuel burn: more as inevitable apu is started earlier compared than before seconds before closing doors. Even when required on hot days is started even earlier than just seconds before 1st customer on board
noise: probably same as above
workload: higher for most compex procedure
complexity: same as above
otp: needs time so you need to anticipate apu start