Is the Start-up clearance concerning the ATC FPLN or the engines start ?
 

During my pilot training a while ago i learnt that when you request the Start-up clearance it is basically asking to validate your filled flight plan.

Today we discussed it with other colleagues because according to some of them it only concerns the actual engines start and has nothing to do with the flight plan.

I looked in various references like the regulation in force, the Lido General manual and miscellaneous documents and what i found is :
- For an IFR flight you need to fill an ATC FPLN at least 60 minutes before start-up or taxi request
- Some countries like Germany request the crews to start the engines within 5 minutes of start-up aproval
- Some others like Turkey Start-up request shoulb be 15 minutes up to 30 minutes PRIOR to departure (so i don't think that's related to the engines)
- Some airport always issue the Start-up clearance with the departure and enroute clearance (CDM)

What do you think ? Please quote references

Validating your FPL happens when you call for your clearance. Usually at that point ATC will tell you if your FPL is still valid or if there are any issues. Engine start is permission to start the engines.

noticed question threads don't get as much attention as tech log threads,
this is a great question and i thing many pilots are confused about this.
my understanding is the start up clearance means your IFR flight progress strip is in the system, nothing to do with engines.
I hope some one can quote references, possibly controllers.

Call me old-fashioned, but when I call for start-up clearance and ATC say "clear to start", I reckon that's clearance to start the engines.
Whether it has any effect on my Flight Plan, I've no idea.

If you call for start for an IFR flight and ATC or AFIS have no flight plan, they will ask you to pass more details.

IMHO the request and cleared for engine startup has nothing to do with FPL, except that you as a pilot have to coordinate the two things.

A "ready to copy clearance" is the sign that ATC did feed the FPL information and you get information on your approved route. FPL has to do with what happens once airborne and is the domain of ATC.
A "startup approved" is the domain of the airfield and relates to ground operations and noise abatement procedures of the airfield operator on the ground. If you are cleared for startup, it only means the airport is ready and willing to take your noise on the ground, not more. It also may mean they are expecting to be able to get you off and on the FPL, but that vastly depends upon the airport.

Yes, the two are dependent as you have to taxi before able to takeoff, but nobody at the tower will ever know your time you need before ready to taxi. If on a busy airport, ops will force you into their procedures and timeframes, but that is assistance.

Procedures vary from country to country and airport to airport, so there is no single answer.

At most airports in the US, ATC clearance or PDC is gotten well before start (~25-30 minutes), from a "Clearance Delivery" frequency or ACARS. Pushback and Start clearance is gotten from a Ramp, Metering, or Ground Control frequency immediately before start.