Auto-throttle lethal potential -Boeing NG checklist.
The revised checklist procedures recently published for the Boeing 737 NG series, has the autothrottle switch armed as part of the after start procedure. This procedure was adopted by United Airlines some years ago. I believe a United Airlines aircraft came close to entering the airport terminal when someone accidently touched the TOGA button after the engines had been started before push back.
For years Boeing recommended that the autothrottle arming should not take place until the aircraft was approaching the departure runway. Presumably there was a sound reason for this at the time. One can only speculate that reason was in respect of Murphy's Law.
With the autothrottle switch armed, and the 737NG TOGA switches hidden from direct view under the thrust lever hand grips, it takes just one momentary lapse of concentration for just one finger to inadvertently activate the TOGA button after engine start, to cause a major disaster - especially after the wheel chocks have been removed and parking brake set off. I have seen it happen in the simulator where the crew were so shocked that neither pilot reacted fast enough to stop the aircraft moving under full power.
Why on earth would Boeing want to change to such a potentially dangerous checklist procedure?
Common sense would suggest that this is a dangerous procedure. Our SOP is not to arm autothrottle until cleared for takeoff- also has the advantage of being a cross check as to whether we have obtained that clearance or not.
The TOGA activation on most aircraft also has effects on other systems on the ground and when airborne. Even when using manual thrust, ATS not armed, it is normal to pull the triggers for take off or go around to ensure that the other systema are activated / de-activated or modified.
Greaser, Why do you think that this is a dangerous procedure. Some of the other Boeings keep the authothrottle armed permanently. I haven't heard of too many major incidents regarding this. If an individual manages to press the TOGA button on the ground and then not resolve the problem, then I believe that is the least of your worries!
"If the airplane is on the ground but has been below five feet radio altitude for less than two seconds when the GA switch is pushed, the autopilot go-around pitch mode will engage but the autothrottle mode will remain IDLE."
Also, isn't there something about the flaps not up or be on an ILS GS, and have been above 5 feet RA for more than 2 seconds for the GA autothrottle setting to arm?
This out of the Vol 2 for the 757/767. I'm guessing that for the 757/767 the A/T will stay at idle.
>>>I don´t have any experience in other Boeing aircraft, but in the 767 we only disconnect the autothrottle arm switch during Non-Normal Checklists...for normal operation the switch is always armed.
Excellent point about the accidental TOGA activation!!! Never crossed my mind!
On the 767, where the auto throttle arm switch lives in the on position, there are other conditions that must be met before pushing the GA bottons will cause GA power to be applied.
On the 767 the two conditions which must be met are glide slope capture or wing flap extension...therefore as we don't extend takeoff flap until after the tug is disconnected and the after start checklist is complete I guess there is no chance we'll end up inside the terminal building.
Why do you think that this is a dangerous procedure. Some of the other Boeings keep the authothrottle armed permanently. I haven't heard of too many major incidents regarding this. If an individual manages to press the TOGA button on the ground and then not resolve the problem, then I believe that is the least of your worries!
I offer the following thoughts not as a pilot but a simple air traffic controller so I hope that you'll forgive me if I have misunderstood the issue.
In ATC we now do safety management. If there is something that can go wrong we try to stop it happening - if a piece of equipment can have the hazard engineered out then it can never happen, if it can't be engineered out then procedures will be written to that the chances of it happening are reduced as far as possible.
If there are certain Boeing types or series where there are no engineering solutions to prevent TOGA power being applied when, say, on stand, surely the procedures should be arranged to minimise the risk of it being done inadvertantly. Not arming the A/T seems the common sense solution from other comments on this thread. Not to do this - particularly simply for the sake of having common operating procedures....on equipment which is different is asking for trouble! One day it will happen.
The macho "only an idiot would do that" or "it's never happened so what's the problem" approach is disappearing from ATC and I would have hoped the same was true of aircraft crew.
Just to contribute, I fly the 737NG aswell and indeed there is no protection. We're using the same policy as a crosscheck for having recieved T/O clearance to arm the A/T only after it. It flows nicely and there is no confusion about what level of engagement the automatics are in. It would be quite a rumble if I'm behind an A/C that by accident starts putting on TO/GA power. Remember that spool up on a 737 is not that long anyway, by far not as long as some of the bigger engines that are out there. So i find the procedure for fleet communality bollocks because it's not safe!