landing clearances
Thirty seconds is a long time. Let's say the inbound aircraft are flying 2.5 miles a minute on final with 5 mile gaps between. Each landing aircraft is taking 45 seconds to roll out and vacate the runway. If the departing B757 takes 45 seconds to take off, then you're left with that wasted 30 seconds. It only needs a slower than expected take-off, a missed exit on landing, or a faster than expected final approach speed to eat into that wasted time.
On a nice day with a dry runway, ATC can use conditional clearances in order to avoid clearing an aircraft to land while it's floating at 2ft over the TDZ. It also makes us look like we're planning ahead, which of course, we are.
The "land after the departing" procedure makes provision for two aircraft to use the runway simultaneously. It can be employed when the controller anticipates that the departure will be at least 2500m along the runway when the arrival crosses the threshold. On runway 23 at EGSS, this is somewhere between links L and K.
The procedure can also be used when the controller anticipates that the departure will be airborne by the time it reaches 2000m. The distance reduces further for smaller types.
Responsibility for separation rests with the controller in the above instance. (S)he knows that the distances and speeds involved will ensure that the departing aircraft WILL clear the runway one way or the other.
Conditional landing clearances can also be issued to aircraft following another lander. In this case, responsibility for separation from the vacating aircraft ahead rests with the pilot, as only he knows how good his brakes are.
Is the fact that one of the aircraft was a B757 of any relevance? Obviously, the wing tip vortices of a departing aircraft take effect too far along the runway to affect arrivals, except in the case of a missed approach. However pilots occasionally complain that they have felt the jet blast of a recently departed heavy aircraft, particularly tail-engined MD11-type types.
It's interesting to note just how many different interpretations of such a common occurrence there seem to be. I wonder if this confusion exists in any other areas?
And for the record, I'd rather be at Emmerdale than Eastenders any day!
Last edited by magicarpet; 8th Jul 2004 at 13:11.