Just for interests sake, on the forces of 747 wingtip vortices. Many years ago as a young fighter pilot, I had the opportunity to escort a 747 SUD in a Mirage F1.
I am a bit rusty on the performance of a F1 now, but just to demonstrate the aileron power of the F1, if I remember correctly at 350kts, lowlevel in an airshow, it had a roll rate in excess of 600º/sec with full aileron application.
I don’t know what speed we were descending, as we were flying fairly close formation on the 747, so was referencing my speed to his, but I’m sure a 747 driver can give us the descent speed in a 747 SUD.
We were descending through about 25,000 ft, when I decided to go and find out what the “hype” was about 747 vortices. I was flying on the right wing, and I slid into the vortice from side. With full aileron application to the right, the vortice still rolled me to the left at the speed of a normal straight roll.
So if anyone still doubts that there is a mini tornado behind a 747 think again. This was at 1 “g” and a fairly high speed, say 250 kts +, and fairly light after a 10 hr flight, and minimal pax. Can you imagine the force after takeoff, heavy and slow. Frightening!
It might have been stupid at the time, but it gave me a healthy respect for vortices, and made me a very careful driver after that, whenever I was behind big birds.
Last edited by Flamgat; 17th Jun 2003 at 18:55.