Indeed...half arse GA is not clever.
In the 767 you hit the GA toggle under the thrust lever and then immediately hit FLCH (Flight Level CHange) which calms things down a lot. The thrust levers won't have got even close to TOGA power (on a 'planned' GA in VMC you wouldn't necesarily 'help' the thrust levers) and will move to an intermediate setting designed to reach the target altitude in the ALT SEL window in 2 minutes. Generally a GA alt will only be 2000-3500' and if you are at 300-1000 that's only a gentle 500-1000'/min climb. You can then alter the ALT SEL up or down as required by ATC, HDG bug left or right as required...or stay in LNAV if following the published majenta line.
You could use VS also but it has traps...the main one being if you are a bit quick you may still be descending when you hit VS and that is the direction and rate it will capture...if you hit GA and VS really quick and the aeroplane is still descending at say 100-200'/min at 135KIAS when VS activates that's what it will keep doing
if only at a 100' it doesn't take much in the way of a distraction before it gets dangerous
Especially in Low Vis Ops with no visual cues.
VS can drive you away from selected altitude where FLCH wont
Hitting GA gets you going in the right direction pronto...but there is no reason, usually, to stay in that mode...the windshear escape manouver being an exception as is hard warning on the EGPWS
A single engined GA is another...on a ILS all three A/Ps control the aircraft...well actually two with one being a tie breaker...and they control the rudder...so you'd stay in GA for a LOT longer before selecting another mode to get settled and ready to hold the rudder in and trim out the assy forces....as soon as you select any other mode from GA you revert to single A/P operation and, if not ready for it, the aircraft is perfectly capable of rolling inverted real quick....in GA mode the 'speed' window opens and you can, if you so desire, wind the speed up and accelerate the aircraft while maintaining the IRS track over the ground and stay in GA mode/3 A/P operation as long as you like.
Well hope someone found that interesting
