Wing Tip Vortices and Winglets
Thread Starter
Wing Tip Vortices and Winglets
There is an old man and his pet dog who live across the road from me and he (the man not the dog) loves aeroplanes. So I drove them to the nearby international airport where there is a viewing area just outside the perimeter and half way between the Middle Marker aerial and the threshold. Aircraft coming down the ILS therefore pass about 100 ft above us.
The viewing area is below the level of the runway so you lose sight of the aircraft just before the flare takes place. There are couple of small trees 30 feet high in the small viewing area below runway level and lots of long grass and bushes.
I explained to the old chap that shortly after a large (B737/A330/B767 etc) would pass over us at 100 ft, he would hear a rushing wind noise and the trees would begin to wave wildly from the wing tip vortices. I had felt this phenomena when walking the streets of Kowloon and a 747 would pass over the buildingsat 100 ft after the IGS approach for runway 13.
For some reason or other, although the wind was calm, we could not detect any wing tip vortice effect even though the aircraft flew directly over us (old man, pet dog and second old man, namely me) at 100 ft. Lots of engine noise, but bugger all vortices.
My credibility shattered, I rang another old friend (retired 747 captain) on my mobile and asked why this was so?
He didn't know, but thought it might be because all the jets we saw landing (eight of them on five mile spacing in a few minutes) were winglet equipped types which he thought did not produce significant wing tip vortices.
Sounded reasonable to me - but what about the two B767's we saw. There were no discernable tree waving caused by their vortices, either.
Any theories on this please. Remember the surface wind was calm and we were directly under each aircraft.
The viewing area is below the level of the runway so you lose sight of the aircraft just before the flare takes place. There are couple of small trees 30 feet high in the small viewing area below runway level and lots of long grass and bushes.
I explained to the old chap that shortly after a large (B737/A330/B767 etc) would pass over us at 100 ft, he would hear a rushing wind noise and the trees would begin to wave wildly from the wing tip vortices. I had felt this phenomena when walking the streets of Kowloon and a 747 would pass over the buildingsat 100 ft after the IGS approach for runway 13.
For some reason or other, although the wind was calm, we could not detect any wing tip vortice effect even though the aircraft flew directly over us (old man, pet dog and second old man, namely me) at 100 ft. Lots of engine noise, but bugger all vortices.
My credibility shattered, I rang another old friend (retired 747 captain) on my mobile and asked why this was so?
He didn't know, but thought it might be because all the jets we saw landing (eight of them on five mile spacing in a few minutes) were winglet equipped types which he thought did not produce significant wing tip vortices.
Sounded reasonable to me - but what about the two B767's we saw. There were no discernable tree waving caused by their vortices, either.
Any theories on this please. Remember the surface wind was calm and we were directly under each aircraft.
Join Date: Jan 2002
Location: The front end and about 50ft up
Posts: 510
Likes: 0
Received 0 Likes
on
0 Posts
Trick question, right?
In still air, tip vortices descend and spread out away from the aircraft. In the situation you descibe, both vortices would have moved away from you.
If there is a crosswind, the vortex from the into wind wingtip will be blown back across the centreline and follow the vortex from the other wingtip downwind. Therefore, if you were standing on the centreline with a crosswind, you would feel one of the vortices pass directly over you, but in still air, no.
Easier to draw a diagram but I hope this helps.
Stout
Remember the surface wind was calm and we were directly under each aircraft
If there is a crosswind, the vortex from the into wind wingtip will be blown back across the centreline and follow the vortex from the other wingtip downwind. Therefore, if you were standing on the centreline with a crosswind, you would feel one of the vortices pass directly over you, but in still air, no.
Easier to draw a diagram but I hope this helps.
Stout
Last edited by Fg Off Max Stout; 20th Apr 2005 at 12:21.
