Boeing Auto-throttle settings

[NWSRG]

Folks,

I undertstand that with an Airbus, you have a number of thrust gates, for IDLE, CLIMB, FLEX and TOGA. And the FLEX gate is variable thrust, depending on the settings the pilot enters into the flight computer.

How do you provide the same facilities on a modern Boeing? Is it all done through a different settings in the flight computer, or are there some magic buttons somewhere that give you the different settings?

[Shaka Zulu]

No gates on the throttles on the 737
You can let the FMC set the throttles, and you can choose settings on the N1 Limit page on the CDU or let the FMC choose for itself in Auto Mode. Changing is simply line selecting the required max thrust setting the FMC will signal through to the engines

[OPEN DES]

hi
the thrust levers in a boeing are ´conventional´. which means that the thrust lever angle is proportional to the thrust produced.(more or less). the thrust levers are servo coupled to the autothrottle and move with thrust change. you have no so-called detents as in the bus.
the thrust reference settings are controlled by the FMC through the N-1 limit/ thrust limit page, or in case of the 757/767 also through a dedicated panel. the autothrottle system automatically commands the selected thrust when needed, which can be either a thrust limit, idle/retard or as required to acquire/maintain a speed, depending on the active autopilot pitch mode. you can also always command the active thrust limit by pushing a button labeled N1, EPR or THR on the Mode Control Panel on the glareshield. hope this is not too unclear.
S

[conch]

Can anybody explain how this works on the B747-400?
For example after takeoff, when you change from TO thrust to Climb thrust. How is this done exactly? Or how is MCT set? I think there are no pushbuttons there or are there?

[OPEN DES]

hi there
in the 744 the thrust reduction is done automatically with reference to heights set on the take off reference page:
- the THR RED HT ; CLB will be the thrust lim (CLB-1 or CLB-2 when reduced climb power is preselected on the THRUST LIM page)
-or in case of N-1 (eng fail): the EO THR RED HT ; CONT will be the thrust lim (MCT)

during a go around the reduction will occur by pilot action by pushing the THR button on the MCP. in KLM the procedure if i recall correctly is to reduce after selecting flaps 5. note that selecting FLCH as pitch mode will NOT initiate the reduction.
hope this helps
S

FYI:
you can also push the THR button during normal climb to de-select a possible reduced climb with CLB-1 or CLB-2 and select full CLB

[NSEU]

"in the 744 the thrust reduction is done automatically with reference to heights set on the take off reference page:"

Or by setting Flaps 5 ;) It all depends on how the engineers program the defaults on the FMC Performance Factors page (or how the pilots override those settings).

Rgds.
Q.

[OPEN DES]

hi nseu
yep thats true! forgot about that one since its not used in most co.s.
regards
S