Medium behind a heavy on take off wake seperation?

[I WAS Birddog]

I noticed that the cleared for take off nod is given at about the 1:30 minute behind a heavy from the same initial take off point.

I am under the understanding that a full 2 minutes must be allotted before we are cleared to blast off. Is it under the understanding that by the time we spool up and start rolling forward that it's close to the 2 minute mark for traffic flow efficiency?

Not being 'that guy' that gets all prudish about 30 seconds. Lord knows my wife is constantly reminding me that 30 seconds isn't anywhere near........satisfactory.

[blue thunder]

[quote="
Not being 'that guy' that gets all prudish about 30 seconds. Lord knows my wife is constantly reminding me that 30 seconds isn't anywhere near........satisfactory. [/quote]


My wife told me that "size matters". Out went the R44 and in came the 407............I think that's what she meant!

[Driving Comet]

Time based wake seperation is measured nose wheel up (rotation) to nose wheel up, not take off clearance to take off clearance. I will start aircraft before the time expires because I know the time will expire by the time the aircraft rotates.

Another reason may be that at larger airports, the tower controllers are certified to provide radar seperation between departures, therefore in your case the preceding heavy will be at least 5 miles away by the time you rotate. Might be around the 1:30 mark.

[Braun]

If the tower is certified to use radar separation they can use mileage instead of time for wake turbulence separation on successive departures.

EDIT: Except behind an A380, then it is always time based separation