View Full Version : thrust not set (737NG)

29th Feb 2008, 04:57
Hey guys and gals,

If thrust is not set after hitting the TO/GA button and you push the thrust levers forward to set TO thrust, will the motors wind back the thrust levers to the previous position if THR HOLD has not annunciated??

This is probably a silly question but please forgive me i'm not an airline pilot

29th Feb 2008, 09:32
When TO/GA is pressed and the levers advance to the requested N1 position,they can then be adjusted as they are then essentialy are in the ARM mode until throttle HOLD at 80kts.the ARM mode can also be seen in a VNAV descent for example,with VNAV PATH annunciated in the FMA the autothrottle will show ARM in white,you can then move the thrust levers to adjust aircraft speed (within +-15kts of requested speed.otherwise it reverts to FMC SPEED).

As far as i can recall this is what happens,but dont quote me on that!


29th Feb 2008, 09:49
If you hit TOGA at T/O, and nothing happens, then the TOGA function doesn't work, right. In your case you're simply operating the thrust levers manually. No A/T, no TOGA and no RETARD.
More importantly;
after hitting TOGA the A/T+FMC will command T/O N1, but if you reach 84 kts before T/O N1 is set, A/T will command THR HOLD at whatever N1 that has been reached. You'll then have to increase thrust manually.

sudden Winds
29th Feb 2008, 19:48
ok 2 diff scenarios here.
U press the TOGA switches, thrust levers advance automatically, u push them forward before THR HOLD annunciation, they will wind back, now, once THR HOLD (84 kts) announces the servos are inhibited and thrust can be manually repositioned. This is to prevent an A/T malfunction from retarding one or both levers during takeoff roll. Now some 17.5 seconds after takeoff this THR HOLD mode will change to ARM till u press N1 when they´ll go to CLB or if 150 seconds pass and you press FL CH.
Now if you press the TOGA switches and nothing happens with the thrust levers the A/T is probably inop. If you are dispatched with an inop A/T you still hit the TOGA switches because that gives you FD guidance and this causes the FMC to update its position to departure rwy.
Hope it helps...

29th Feb 2008, 19:58

this causes the FMC to update its position to departure rwy

Ooo, errr....

29th Feb 2008, 23:17
thanks so much everyone! Here in Australia i think alot of airlines just allow for auto thrust reduction, do your airlines make you set climb thrust by pressing N1 or allowing for autothrust reduction to occur?

1st Mar 2008, 11:14
My airline lets the auto thrust reduction do the job. Set at 1500' in the FMC.