|Quoting Glom (Thread starter):
When we landed at LHR last night, as we taxiied, I watched the line of incoming aircraft and noticed how closely spaced they were. I timed the delay between two landings, the first an ERJ and the second an A319. It was probably only about a minute. According to my air law book, the wake turbulence space for medium on medium is 2 minutes.
Are LHR breaking the law?
At Heathrow we do not use time based spacings for arrivals. Director clears aircraft onto the ILS at the correct distance based spacings. These spacings are theoretically those written in the book - which are -
- Heavy / UM
- Upper Medium / LM
- Lower Medium / SS
- Small / LL
R - Radar Separation 3Nm / Reduced final approach spacing = 2.5Nm
1Nm = 1852m
Anything marked R will be 3Nm or given the right conditions during the day 2.5Nm.
Also important is aircraft have to maintain 160kt until 4DME to keep the approach spacing constant, afterwhich they can reduce to final approach speed. But having said that each aircraft type has a different speed profile. So some maybe able to do 160kt but some like the B773 (usually the stretched aircraft) will be a bit faster and some will be a bit slower. The final approach spacing will be adjusted slightly to account for the slight speed differentials.
If you time it again and measure that against the appraoch spacing chart, each Nm equates to approximately 23-25sec.
[Edited 2006-08-21 17:19:43]
[Edited 2006-08-21 17:21:33]
[Edited 2006-08-21 17:22:25]