Medium behind medium separation!
 

Earlier on PP we have established that due to doc 4444, separation minima on an approach for two medium aircrafts behind each other on an ILS is 3 NM (unless other rules apply, London airports 2.5 NM)

But what about in departure?????

How many minutes shall a medium aircraft wait for a take off clearence when preceeding is also medium????

2 minutes minimum I believe the answer is.

I am not sure you are completely right on that, since i have experienced T/O clearences behind medium aircrafts after less than 1 min!! (obviously flying a medium myself)

Depending on cirumstances, there might be no time limit, it depends on local standards. In the UK using reduced separation you can have two B737s depart wheels up (ie when the first one leave the grounds the second one is cleared), this presuming the conditions allow it.

Heathrow do this routinely, but it is possible (and done) at other airports as well.

There is not normally any requirement for M-M departure separation for wake turbulence separation.

FAA pilot/controller basic training manual gives no requirement, FAA Recat and UK AIC P001/2015 also give no requirement, but they should be required reading. No odoubt someone has quick access to ICAO DOC.4444 for their version. You will see that the minima are different depending on the state, airport, (mode of operation at that airport), airline SOP, individual pilots etc.

Any stated separation is a minimum and can be increased should the pilot feel the necessity (but do tell the controller in advance if you feel the need for separation over their minima).