Engine start order in 744 versus 742 -why different?

[Byrna 0]

Hello everyone,I recently noticed that the engine start sequence for the Boeing 747-400 is engine 4, then 3,2,1 in that order. However, in the 742 Ready for Pushback which I use, it is 4,1,2,3 which to me makes more sense. The way I understand it, starting two engines in symmetrical positions on the wings will distribute the sudden backlash of thrust force evenly on the airframe and gears, thereby reducing any tendency for the plane to suddenly move sideways (or any chance of it in any case). Can anyone with a type rating on the 744/742 comment on this difference in the engine startup order?Thank-you in advance,John

[JayBirdski 1]

Sorry i don't have T/R but I think start procedures are largely airline specific. The one example I can think of that doesn't follow either of your procedures is DLH. Saw a video of them going through a start on http://www.a340.net/ and they do 4&3 together and then 2&1 the same way. I wouldn't think that any start order would have a tendency to move or stress anything on a 74x. Jay EklundCAT VI Senior Captain KDENhttp://online.vatsimindicators.net/812321/764.png

[AWACS 12]

And in our E-3, the engine start order is 3,4,2,1.Jeff

[CF104 0]

On the 747, hydraulic system #4 is the supply for normal brakes. This is why #4 is started first and the remainder of the start sequence is airline specific.As for the starting of 2 engines at a time, there's no limitation. The airframe can more than handle 2 engines on one side at idle power. Think of it this way, the 744 can sustain flight and land with 2 engines out on one side without adverse effects to the airframe.Cheers,JohnBoeing 727/737 & Lockheed C-130/L-100 Mechanichttp://www.sstsim.com/images/team/JR.jpg

[Guest]

well, if the bleed air system can't provide enough to start two engines at once that would be a limitation :)Would be equipment specific of course.