Stand 'em up.

[michaelknight]

Hi,

When standing the thrust levers up before T/O, what's the figure you aim for???

In my company there's no said figure cut in stone, however, it does say minimum 40% N1. I commonly see guys stand them to about 40 or like 39% afraid if they exceed this the engines are going to fall off! But seconds later TO/GA is pressed.

I did see one company use ballpark 60%.

Obviously as I stated 40% is the min, and I take it you're not supposed to set take off thrust when standing them up.

I am talking B737 here, and using N1s.

MK

[sjm]

SET 40% call stable, hit TOGA!
I believe that is boeing procedures as well as my company for 737-3/5

[Old Smokey]

I no longer fly B737s, but the situations described here are pretty-much uniform across most jet aircraft.

Whilst a particular engine parameter (N1, EPR etc.) should be achieved before advancing the Thrust Levers to the Takeoff position, what is arguably more important is that the acceleration of all engines is uniform, or at least near-uniform.

I've had a case of #4 taking it's time in spooling up whilst the other three were 'already there', which required some pretty assertive Nose Wheel Steering application to keep the aircraft on centre-line. Once in unison with the others, acceleration of all engines was quite uniform (which is typical).

Four important considerations arise from this requirement -

(1) Directional control (as alluded to in the preceding paragraph),

(2) Engine serviceability. If the initial AND final spool up is sluggish, the lagging engine has a problem, and a Reject is probably warranted,

(3) Performance. Field limitations are predicated upon all engines being set to Takeoff thrust within a specified time, distance, or speed. Sluggish engine acceleration invariably means sluggish aircraft acceleration, and Field performance may be compromised,

(4) Aircraft with "Engine Failure Detection" systems may be triggered by the disparity between engine readings at a too-high Thrust Lever Angle. This could lead to a spurious "Engine Failure" warning (necessitating an abort), or, for those aircraft fitted with APR, advancement of the 'better' engine to full 'Rated Overboost', making directional control problems even worse.

Just mt $0.02 worth!

Regards,

Old Smokey

[esreverlluf]

Just do as the ops manual says - for all of the reason above, but also, you won't get lambasted at the enquiry when something goes wrong.

Why must people invent their own procedures ! ! !

I'm sure that Mr Pratt, Mr Whitney, Mr GE, Mr RR or whomever had good reasons for recomending whatever N1 or EPR or whatever other parameter. It is quite unlikely that myself or any other dumb ass line pilot will have a reason good enough to do anything but what the ops manual says.