Gaps between Departures
Hope you don't mind a humble pax asking what might seem a silly question.
Why do the departure gaps vary so much at busy airports?
I understand the need to avoid wake turbulence and gaps between big planes and small planes are always greater but that's about as far as my knowledge goes.
Take LHR and MAN as two examples that I have watched over the years (and sat at the holding points of both for what seems like years). Both have dedicated departure runways so no need to leave gaps for landing aircraft.
Observing the runway at LHR, an aircraft seems to roll as soon as the previous a/c has become airborne. This is probably as good as it gets, and ever can get.
MAN on the other hand, despite being less busy, seems to generate huge queues of a/c at the holding points at times. Look at the runway ops there and a/c seem to wait for ages after the previous departure. Both examples make allowances for different a/c size etc.
Could anyone explain why this happens to an often late passenger?
Thanks in advance.