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Start-up clearance

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At some airports that have a specific Delivery frequency, I've heard it common to just request the IFR clearance to you destination. And in that case, ATC might sometimes answer with start-up approved, and as far as I'm aware that only means that they have opened the flightplane, and not actually that you can start the Engines?

But at some smaller Airports with no DLV frequency, it seems common to just request start-up and the clearance in the same call - and as a respone to that ATC will give you the start-up clearance, but in this case does it mean that you can start the Engines since you started of by asking for start-up?

If that is the case what is the difference, and why does some Airport prefer if you directly ask for start-up clearance, instead of start by just requesting the clearance, or is it the same thing?

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I'm a pilot and no expert in ATC procedures but from what I can gather...


In Europe, startup clearance is ATC's way of telling you that the airways system is ready for you, in many cases it does mean you can start up but this is academic for airliners that normally start on the push (so they'll need push clearance as well which is dependant on a whole load of other things). In some places where you don't push, clearance to start is exactly that, Milan Linate springs to mind. When I was training we'd ask an airways controller for start, start the engines then talk to the airport for taxi and take off and then talk to the airways guy again in the air for clearance into controlled airspace, I've never done this commercially though.


Practically, most places most of the time don't have much restriction in the airways system so when requesting the clearance you're given start at the same time (just meaning, no restrictions into the airways system). In a lot of airports around Europe you can be given clearance to start a long time before your actual push time.


Where I've experienced it most is at LHR, delivery will give you your clearance (by ACARS) but won't give you start until the airways system is ready for you and there's not too many people at the holding point. When he's happy he'll give you start clearance and send you to ground who'll have a whole load of other delays for you. Finally he'll give you push (so now you have a clearance, push and start) and off you go. These days they have a new acronym (which escapes me at the moment) so you need to worry about your EOBT, TSAT and TTOT, fundamentally the same system but there's a computer in the middle that comes up with new and innovative reasons why you can't go.


At smaller airports start up and clearance are often requested at the same time as the clearance is often not ready for you until quite close to departure, there's less likely to be delays as well (so no start delay). These days you can get your departure clearance via ACARS or CPDLC thus negating the request but you will usually get start clearance with the push. 


For the aircraft to push you need 3 things from ATC :

1) Clearance, sometimes departure clearance or airways clearance - this is confirmation of your flightplan and SID. This must be checked as it's perfectly acceptable for ATC to give you a new route (partial or complete) at this point. It will also include departure instructions (SID, initial stop alt and Xpdr code).

2) Start clearance - Everybody's ready for your flight...

3) Push clearance - The airport has room for you to actually move.


You can ask for these things in any order you like but you can't release the park brake until you have all of them. Some places give you the whole lot at the same time (most confusing), some spread them out over a period of time (of indeterminate length) and the nice places give you a clearance, let you digest it and when you're ready, give you push and start.


Hope this makes sense and hopefully there'll be someone who can explain the US system to you and correct my interpretation of the EU system.



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