Warped Factor:-thanks for the information regarding the Boeing 757. I recall the survey being carried out about the wake vortices that are generated by the B757. I can’t lay my hands on the magazine at the moment but I seem to recall the Boeing “Airliner” magazine published an article about their findings. If I remember correctly it was something called a “Tangential Vortex” that was out of proportion to the weight of the aircraft, and this is what causes the problem. The statistics you have are fairly conclusive, my own experience of following B757’s around the UK and Europe are that they are really no better or worse than anything else. Once you hit vortices you just deal with them. I couldn’t quantifily say one type produces a stronger vortex than another. As you also point out the problem largely solves itself at LHR as BA dispose of their 757 fleet.
09L:- thanks for the information regarding the X-wind limits and R/W 23. I take your point about the loading of Director on 120.4. But (at risk of oversimplifying their job) once they have you spaced correctly, and doing 160kts to 4DME, they can hand you over to the Tower. The point about more, or better sited, RET,s is that time spent on the runway itself would be reduced. For instance, your namesake 09L. The constant dilemma is whether or not to keep the speed on and roll to block 16 or 17 where we can leave at 20+kts, or whether to brake harder for a block 14 or 15 which, both being 90degree turn-offs, require the speed to back to less than 10kts. Now if there was a high speed turn off around about block 14/15 I believe that it would be a great help especially for aircraft who will be continuing Eastabout, in that they get off the runway at a higher speed leaving it free for you to land another one. I accept that in this example it’s not so convenient for aircraft who will need to taxi Westabout for their stand, but I hope you see my point.
Do you have any statistics for Go-Arounds that are caused by aircraft failing to clear the runway in time? It may be of course something along the lines “…if it ain’t broke…..” and more high speed turn offs are, statistically, not required.
Lew Ton. Thanks for the information about grip testers, mu-Meters, and wet runways. I believe the B757 is still classified as a medium for determining it’s required spacing when following traffic, but when you are following a B757 then it becomes an Upper medium.
Finally can I express my thanks for all the people who work in the ATC, particularly at LHR. Their professionalism, patience, humour and understanding are much appreciated.