What is this?

jonesey2k · Post by **jonesey2k** » 15 Jul 2006, 13:40

Took a pic of a Virgin 747 going over and I just noticed a 5th contrail comming from the tail. I dont think Ive seen that happen before. I allways thought the APU was shutdown after takeoff?

Post by **Garry Russell** » 15 Jul 2006, 13:49

I've seen 737 doing that even without engine trails many times at fairly low level.

I think its just the moisture being squeezed out as the airflow leaves the rear fuse in the same way streamers form on the corners of flaps.

I don't think it's the APU but of course it might be if it is running still.

I am sure someone will have the real answer..but it is not that rare.

Sometimes I have seen 747's trail from the whole wing instead of just the engines (at altitude)

Garry

VEGAS · Post by **VEGAS** » 15 Jul 2006, 14:21

Perhaps they are filming a Bond movie up there!

http://www.airliners.net/open.file/1070481/M/

Charlie Bravo · Post by **Charlie Bravo** » 15 Jul 2006, 14:46

Something on the aircraft was probably u/s and so the APU is left on. We had this at work the other day but I can't remember what the problem was exactly.
It was a tech generator or air pack I think.

DispatchDragon · Post by **DispatchDragon** » 15 Jul 2006, 18:00

Usually its a generator folks but I think the 400s APU (like the Airbus) produces enough air to drive a pack. Of course the 747 could go transatlantic with an Engine gen. mel'd (its not subjects to ETOPS). It actually
happens alot more often than you (John Q Public) would know -Its fine for a four engined aircraft but its a losing propostion for twin engined because you
cant operate ETOPS thataway - and should your APU go pop from all that work your going to one place and one place only - The nearest available and suitable airport - flying on one generator ETOPS or NOT is a total nono

I'll wait for VC10 or Motormouse to give a read on UK law

Leif