Thrust Levers for Multiple Engine Civil Jet Aircraft

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Bowing
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Thrust Levers for Multiple Engine Civil Jet Aircraft

#1 Post by Bowing » Fri Feb 05, 2016 9:34 pm

I've been going forum to forum to ask a technical question, and if this is not the right thread I apologize. Let me start by saying I am not a pilot, but I have a question about anyone who is. Jet aircraft with more than one engine have a thrust lever for every engine. I have seen videos of pilots simultaneously pushing all 4 levers at once. But they must also be able to use the levers individually.

My question is what mechanism is used to "lock" all the levers at once, and push them forward simultaneously, and how would the pilot then be able to control the thrust levers individually in case of an engine failure? Do the thrust levers move individually and the pilots just make it seem as if though they are locked together in unison? Or is there a mechanism by which the pilot can CHOOSE whether to move the levers in unison, or by themselves?

If different aircraft use different methods, I would really appreciate it if someone (preferably pilots) could describe the different methods.
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ahramin
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Re: Thrust Levers for Multiple Engine Civil Jet Aircraft

#2 Post by ahramin » Sat Feb 06, 2016 1:40 am

I have never seen a mechanism to lock the throttles together or move them together except for your hand. All airliners and most business jets nowadays have autothrottles though so at the start of the flight you click a button and they all move to takeoff power together, then the computer keeps them even while maintaining the desired speed. Airbus is a little different as with autothrust on the thrust lever are set to the limit, not the actual thrust, and don't move.
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robertw
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Re: Thrust Levers for Multiple Engine Civil Jet Aircraft

#3 Post by robertw » Thu Mar 03, 2016 8:40 am

I've never seen a mechanism to "lock" throttles together in any aircraft. That would actually be a pretty dangerous thing if you had an engine failure. I'm an AME and have worked on rotary wing and fixed wing from business jets to C-152's to S-92's to Bell 47. Can't speak to airliners though. Engines very rarely will output the same power at the same power lever settings so they have to be adjusted by hand until the engine thrust is pretty close to being matched. On the more complicated aircraft there are engine / propeller synch systems that will (by computer) adjust the engine / prop rpm once you've adjusted them by hand relatively close to one another. There are devices for adding / removing friction between the throttle levers in most aircraft though. basically, you have a screw type knob at the pivot point of your throttles. As you screw the knob in, it squeezes the levers together, creating more friction between them. This keeps the levers from moving around in flight due to in flight aircraft vibrations.
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Nark
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Re: Thrust Levers for Multiple Engine Civil Jet Aircraft

#4 Post by Nark » Fri Mar 04, 2016 8:23 pm

I have a few years experience between the Airbus and Embraer jets...
Like what the other gents are saying, they are individually moved, but there there is a small mechanical connection between the two that allows for the thrust levers to be moved in unison. Think of it like a cap to a pen. You apply a little pressure (i.e. Picking up the pen) you pick up both the cap and the pen. Now on the same note, apply a little force to the cap, and it will come off. (~5lbs or so)

When I single engine taxi the Airbus I apply enough pressure to the #1 thrust lever, as to not move both. (The right hand engine isn't started yet. We save a lot of fuel that way).

None of the multi Pistons or King Air's had the same interconnect. Nor does the multi engine helicopter I also fly.
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