Yousef727 From Denmark, joined Apr 2004, 22 posts, RR: 0 Posted (11 years 9 months 1 week 4 days 4 hours ago) and read 3812 times:
A few times I've seen a single thin contrail coming from the most rear part of the A320, the same area as the APU exhaust in the tail. When I saw it the planes were on approach about 20 miles from the airport flying at aprox. 1500-2000 Ft.
SPREE34 From United States of America, joined Jun 2004, 2406 posts, RR: 8
Reply 1, posted (11 years 9 months 1 week 4 days 3 hours ago) and read 3754 times:
They were probably starting it (the APU) up. Some carriers do this on final so they can shut an engine off after landing for fuel conservation, yet still have full electrical and air conditioning during the taxi
I don't understand everything I don't know about this.
Yousef727 From Denmark, joined Apr 2004, 22 posts, RR: 0
Reply 5, posted (11 years 9 months 1 week 3 days 12 hours ago) and read 3522 times:
No it was not cold. It's summer here. Yesterday when I saw it, the temperature was 75F (+23C).
Probably it was not a contrail like the ones you see from planes flying at high altitude, but some kind of exhaust gas from APU startup. That's the explanation I'm thinking is the correct one.
Prebennorholm From Denmark, joined Mar 2000, 7111 posts, RR: 53
Reply 6, posted (11 years 9 months 1 week ago) and read 3323 times:
The contrail from the tail wasn't necessarily created by the APU. It might have been a vortex generated contrail like we often see them from wing tips in humid air.
Last Thursday, even if we had temperatures in the 70'es, the air was very humid. I watched a satellite photo of the country on the weather bureau web, and even if the cloud cover was scarce, then the whole country was practically covered with high altitude airliner contrails.
Often the contrails evaporate in minutes, but last Thursday they staid for hours and became thousands of feet wide.
Always keep your number of landings equal to your number of take-offs