Originally Posted by
Feather44
Good day all,
I have a doubt. There are basically two procedures
- RADAR separation
- TIME based separation
Let's assume we're departing from an airport where separation is based on radar.
Are we supposed to respect the time constraint as well??
Ex: cleared for T/O by Tower (I can see on the ND that the preceding ac is at least 5Nm ahead). However, the time constraint (2 or 3min) is not elapsed yet.
Can we take off??
(I presume that's a NO, but I can't find any explicit document)
The answer is YES. ATC will have applied the applicable standards between you and the preceding aircraft. A pilot in command is ultimately responsible for the safety of the operation, but hesitating on the runway is not generally a good contributor to safety a a busy airport.
Wake separation between successive departures, either time or distance, is based on rotation point, not wheels up or other things as suggested. ATC will apply the most efficient standard available, cognisant of wake turbulence and physical separation minima and take into account other factors such as aircraft performance relative to the preceding aircraft and clearance (such as are they following the same SID or are the turns after airborne different). Remember that the tower controller can usually see at least the aircraft on the ground out the window and will use the situation display to confirm the position of the airborne aircraft. Timers are used where required.
As an aside, let's get away from the old fashioned concept of radar, too. Position information is frequently derived from other technologies such as MLAT and plain ADS-B as well (both of which are more accurate than radar) and data is from various sources is fused by software to display the most accurate position to the controller.