737 - A/T take-off procedure (Merged)
 

Hello everybody,

I wonder how you set take-off thrust during an auto-throttle take-off (B737-300/-400/-500)
Do you, after having the engines stabilized at 40% and having pushed the TO/GA button, wait until the A/T sts the thrust by itself or do you get impatiend about the slow performance of the A/T and "fiddle" the thrust levers to the desired value.

Thank you for your help!

Somewhere I had a Boeing brief which stresses that the setting of power is a 2 stage process, and you should NOT push them up unless the system does not work after the second stage. First stage is to about 80%ish and then the second fine-tuning. Throttle 'pushers' simply mask unserviceable throttle lever clutches and systems. I'll try to find it.

Thank you BOAC,
I would really appreciate to have this document.
I couldn't find any references in the FCOM or FCTM.

Moscho999

Lucky strike! Boeing Flt Ops Tech Bulletin 737-300/400/500 97-1 Dated April 29, 1997. ATA Number 22-31 Subject Autothrottle Operation. from Flt Crew Training PO Box 3707, Seattle.

Precised: First stage is to within 8% of target N1, then to target. THEN (and only then) pilots should adjust to +1% -0% of target. Avoid applying force to the levers unless manual intervention is intended. It also recommends NOT 'following' the levers such that you apply more than 1.5 lbs of force at the top or you may cause the clutch to malfunction. There is a 'caution' that more than 20kts of headwind may produce throttle hold before target is reached.

I always maintain the autothrottle should be allowed to TRY to set power or you may never know when it is malfunctioning.

40% to spool, then about 60% let the engine stabilize momentarily there and push TOGA. Don't try to push the the thrust levers up near the target N1 and then push the TOGA buttons, it doesn't like that.

Do it that way and it will be perfect every time.

60% was necessary to get it into the active range for the PMS (if I remember correctly).

This is Great
 

We should do online reviews of systems. This would be a great way to study the airplane.

Junior Man. 40% N1 then pushing to 60% N1 sounds like a company check captain favourite gimmick. It is best to stick to the manufacturer's procedure which is 40% then TOGA. On a non-auto throttle take off I have observed some pilots "walk" the thrust levers instead of pushing them smoothly together. "Walking" the thrust levers is another gimmick.

Procedure was given to us by Boeing as we were seeing some issues with the autothrust. Company was operating about 80 737 300/400s back then and it was standard procedure. Also solved the problem and the autothrust worked fine. Still the same procedure today.
About the worst thing you could do was to push the throttles up to almost the target N1 and then push the TOGA button. That was a leftover habit from 737 200.

jm - if it does not accelerate evenly from 40% snag it! BA had the Manchester fatal following long-term throttle stagger and, I believe, uneven acceleration.

Original procedure was to hit TOGA at 40% and stable, the second step produced much better results. Especially fewer exceedances. When I left we had been doing it for about 10 years with excellent results.
Different engine acceleration may be a variety of things. JT8Ds were bad for that as they always seemed to have different bleed configurations between the 2 engines.
The big difference with the second step was to get above the minimum RPM for the PMS to start doing it's thing.

@BOAC

Thank a lot. Found ref. doc on myboeingfleet.com.

@everybody

We changed from the 40% to the 60% procedure - but without intermittend step at 40%. Works fine for us!

Moscho999

"Stabilized" and "Thrust Set" call
 

Hi,

2 questions about jet ops:

What is the max N1 (or EPR) difference allowed before engines can be considered "stabilized" prior to application of takeoff power?

I'd also like to know when thrust is considered to be "set"? Say takeoff N1 is 100.0%, How close does the actual readout have to be before therust is considered "set"? For example, is 98.5% considered "set"?


Thanks for any help

As far as I know,on 737 you should set thrust at aprox 40 N1 (+- 5%) .Then increase power to be set by 60 kts.Thrust should be adjusted,if necessary,by the PM to -0% +1% target N1.
In your ex 100% to 101% N1. 98.5% is NOT good.

They are both a matter of technique and tools available.

On the 744, autothrottles are generally used for all takeoffs. The thrust levers are advanced to approximately 70% N1, but that may be anywhere from 65 to 72%. The TOGA button is then pushed, and the authrottles take over.

On the 747 Classic with digital engine gauges and FFRATS autothrottles, autothrottles are used some of the time, depending on the Captain's and FE's preferences. Thrust levers are brought to approx. 70% N1, but it is more important that the N1s are consistent between engines (+/- 1-2%) than exactly 70% (the thrust levers may be significantly staggered).

If autothrottles are used, the FE tries to equalize N1 again when the autothrottles reach the programmed position, because they stop when the "leading" engine gets to target N1. He then tweaks the others ("lagging" N1) to get them as close as possible.

If autothrottles are NOT used, the Captain advances the thrust levers close to target N1, using approximately the stagger attained at 70%; then the FE sets them as close as possible to target before 80 KIAS. In this case, a little ABOVE target is preferable to below.

In either case, it is not possible to eyeball much finer than +/- 0.5% at T/O thrust.

Again, individual techniques vary.

Basically, I was looking for the N1 tolerances for the different calls, am I right in understanding from the above posts that it essentially will vary from person to person?

CA.....each airline has its own SOP,s,......adhere to the the one thats paying you/...

Worked for several A-320 operators....completely different SOP,s completely different reasons....the settings are either within the operating parameters or they not....:confused:

Check - you may wish to glance at this thread? Boeing (in that 'oldish' - 19/5/1997 - document, for 737 3-500, and presumably 6-900?) say initially at least 40% and no need to reduce if greater; 'Acceptable' TOGA thrust setting by a/t at THR Hold is +/- 2%, and manual intervention ONLY after the 2 stage a/t action is complete should be made to adjust to +1%/- 0% of target.

My flying manual says that getting the thrust up is more important then setting them exactly the same. As far as I know there is no specific margin for that. However if the runway is slippery and a limiting crosswind I would like to make sure I'm a bit more accurate that day then normal to ensure a very even spool up time

thanks all for all the neat info

BOAC and Moscho 999. The Boeing Bulletin regards throttle stagger at 40% N1 during the initial spool up prior TOGA has been withdrawn as far as I know presumably because the AD's fixed the problem. Moscho - anything works fine -you just name it and it's been tried - but why not stick to the Boeing recommended procedure.?