Why do jet planes with multiple engines have separate throttle levers for each engine?

Question

What are the reasons to not just use one throttle lever for all engines?

GdD · Accepted Answer · 2016-12-17 14:02:38Z

10

All multi-engine airplanes, whether jet or prop driven have separate throttle controls for each engine. There are good reasons for this:

If there is a problem with one engine you can separately control it for troubleshooting purposes
If one engine isn't developing the right amount of power you can independently increase the other engine(s) to compensate
If you have a control failure of some kind you can use differential thrust to steer the airplane, this has been done more than once, the example that comes immediately to mind is United 232

answered Dec 17, 2016 at 14:02

GdD

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$\begingroup$ Most modern engines use digital electronic FADEC control. It would be very easy to have one thrust lever and still accommodate separate control for all the reasons given above. I have to assume the really reason might be something else. ( like tradition) $\endgroup$
– Mike Sowsun
Dec 17, 2016 at 14:38
2

$\begingroup$ Differential thrust is also very helpful in taxi, not just in the event of control failure. I often use differential thrust as my primary directional control in taxi. $\endgroup$
– J W
Dec 17, 2016 at 17:02
4

$\begingroup$ @Mike Sowsun: Turn the question around, though, and ask whether there are any good reasons to have a single throttle control. I can't think of any, but then I'm used to just having one engine :-) $\endgroup$
– jamesqf
Dec 17, 2016 at 19:46
$\begingroup$ To extend the question considering this answer and comments: are there devices that can selectively 'gang' all thrust levers, to avoid unintended differential settings? Like when a pilot wants to move all to TOGA but lets one slip? $\endgroup$
– Rob Vermeulen
Dec 18, 2016 at 14:50
1

$\begingroup$ @RobVermeulen, the levers are always made such that you can grab them all at once and move them together. In many aircraft the significant settings (TO/GA, MCT, FLEX, CLB and IDLE) also have detents to assist in precise positioning of the levers. $\endgroup$
– Jan Hudec
Dec 19, 2016 at 19:25

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