Folks,
The following remarks apply to FAA definitions, and to the operation of US certified aircraft in conformity with the aircraft MMEL, and whatever portion of it individual carriers use. That means almost everybody outside 'Europe".
I do my best to avoid JAA, so far I have been successful, finding an N registered seat even in the JAA "sphere if effluence"
You need to know the FAA definition of dispatch. It's nothing to do with the Flight Despatch department,although both the dispatcher and the PIC have to sign the dispatch release certificate,commercial dispatch as in departure, doors closed, pushback, engine start etc.
Those who understand an FAA Operational Control 'Dispatch Release Time' know that is a takeoff time. For the purposes of Operational Control, and the application of the MEL, the aircraft is dispatched at the start of the takeoff, all checks and clearances received, aircraftc is airworthy etc. ( Same same CAR 233 release for an international flight in Oz)
Those flying B767/757 will remember/understand that STATUS messages, messages that can determine the "pre flight airworthiness", messages that might prevent dispatch,are valid up to takeoff, thereafter they are advisory, or they will escalate to a higher level message.
On the 747-400, any status level message that is a potential stopper becomes a higher level message after engine start, and the MEL has to be consulted for "dispatch relief". At least that's the theory, there have been continual fun and games over the years, quite a few software/data mods and "temporary procedures". Be smart, don't be concerned with definitions, regulations etc., consider any message and decide up to 80kts, if you are still flying something that doesn't suppress most messages from thrust set until aorborne plus time/height.
For pilots who were not originally trained in the US system, this has been a area of mystery for years, why I don't know because all the Boeing manuals I have ever used spell it out in language even a pilot should be able to understand.
Likewise FAA definitions/rules ---- "A pilot shall not take off an airplane unless ---- " last time I looked it was somewhere around Part 121.630 plus.
I long ago came to the conclusion what, for does of uz what spic English as de mudder tongue" it is a matter of "divided by a common language", there is dispatch, and there is dispatch.
Tootle pip,