Quality of cabin air on the ground
I've just flown LHR - AMS on 737s. I was sitting at the rear on the way out and it was stuffy on the ground. I was sitting near the front on the way back and noticed that the air supply was much better. Other experiences:
BA 319/320/321 sitting in the rear - very comfortable whilst on the ground
BA 747 rear - uncomfortably stuffy (and thats when the APU is working) also the lack of adjustable air vents don't help
BA 777 rear - better than 747
KL F100 front - fine
DL all aircraft anywhere in cabin - also good (although I've not travelled in the summer)
Perhaps an engineer or pilot (or CC or SLF) could answer the following:
Is the rear of an aircraft generally worse than the front? Does it vary by type?
Presumably things are better with an external air supply?
Do some airlines put a higher priority on keeping the cabin comfortable on the ground than others?
What proportion of aircraft are flying with an unserviceable APU? Does this vary much by type or airline? Is it because APUs are inherently unreliable or airlines do not put a high priority of fixing failures?