# airplane transmissions
**URL:** https://boards.straightdope.com/t/airplane-transmissions/184261
**Category:** Factual Questions
**Created:** [June 25, 2003, 9:18am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261 "2003-06-25T09:18:38Z")
**Posts on this page:** 13
**Page:** 1
### Author:  [@SlickRoenick](https://boards.straightdope.com/u/SlickRoenick)
#### Post date: [June 25, 2003, 9:18am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/1 "2003-06-25T09:18:38Z")
I checked [howstuffworks.com](http://howstuffworks.com), [boeing.com](http://boeing.com), [google.com](http://google.com), and even searched these boards but so far haven’t found the answer. What are the mechanics behind moving airplanes around on tarmacs? Are the wheels gear-driven or belt driven or what?
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### Author:  [@Doc\_Nickel](https://boards.straightdope.com/u/Doc_Nickel)
#### Post date: [June 25, 2003, 9:32am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/2 "2003-06-25T09:32:25Z")
They are not driven at all. Airplanes move entirely via engine thrust. Barring that, those little lowboy trucks (or “tugs”) hook up to the nosegear and literally tow the airplane around. (Which saves a considerable amount of fuel.)
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### Author:  [@hibernicus](https://boards.straightdope.com/u/hibernicus)
#### Post date: [June 25, 2003, 10:47pm UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/3 "2003-06-25T22:47:17Z")
It’s worth noting also that if you’re sitting in a passenger aircraft, and it starts to reverse away from the gate, it is being pushed.
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### Author:  [@Berkut](https://boards.straightdope.com/u/Berkut)
#### Post date: [June 25, 2003, 10:55pm UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/4 "2003-06-25T22:55:43Z")
> [@](#):
>
> \*Originally posted by hibernicus \*
> \*\*It’s worth noting also that if you’re sitting in a passenger aircraft, and it starts to reverse away from the gate, it is being pushed. \*\*
Not all the time. Sometimes they “powerback”, which means they use the engines power to back the airplane away from the gate. Most aircraft of the passenger carrying variety have a means for thrust reversing (not all, though).
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### Author:  [@Padeye](https://boards.straightdope.com/u/Padeye)
#### Post date: [June 25, 2003, 11:10pm UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/5 "2003-06-25T23:10:41Z")
A few propellor driven plans are capable of reverse thrust by changing the pitch of the propellor blades. The only ones I can recall doing this are E-2 Hawkeye radar planes which are able to neatly back into the six pack area on a carrier under their own power.
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [June 25, 2003, 11:43pm UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/6 "2003-06-25T23:43:34Z")
For the most part, airlines prefer to “push back” from the gate with a tug than to “power back” with engine thrust.
Why?
A power back gobbles a lot of fuel. Jet engines may make a lot of thrust, but not so much torque to move the plane from a dead stop. Also, it makes a lot of noise just outside the door that’s not appreciated in the terminal. The tugs on the other hand, are comparatively silent and have gearboxes that yield great gobs of torque. No speed, but a whole lot of push. Also, a push back is that much less wear on the engines and thrust reverser components.
When you’re on the plane and start moving back, it’s easy to tell if it’s by push or power. With a pushback, it’s like “Oh! We’re moving.” If the engines are running at full scream and you start moving, it’s a push back.
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### Author:  [@bernse](https://boards.straightdope.com/u/bernse)
#### Post date: [June 25, 2003, 11:56pm UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/7 "2003-06-25T23:56:06Z")
> [@](#):
>
> \*Originally posted by Padeye \*
> \*\*A few propellor driven plans are capable of reverse thrust by changing the pitch of the propellor blades. The only ones I can recall doing this are E-2 Hawkeye radar planes which are able to neatly back into the six pack area on a carrier under their own power. \*\*
IIRC, many turboprops are capable of this. I’ve seen a Dash 8 passanger aircraft do it too.
> [@](#):
>
> A power back gobbles a lot of fuel.
Not only that, I think there are regs prohibiting it now, too.
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### Author:  [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)
#### Post date: [June 26, 2003, 12:56am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/8 "2003-06-26T00:56:54Z")
> [@](#):
>
> \*Originally posted by gotpasswords \*
> **Jet engines may make a lot of thrust, but not so much torque to move the plane from a dead stop. \ The tugs on the other hand, are comparatively silent and have gearboxes that yield great gobs of torque. No speed, but a whole lot of push.**
“Torque” isn’t something that’s relevant to a reaction engine. Force is. Saying that jet engines “make a lot of thrust” is another way of saying “yield great gobs of force”.
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### Author:  [@GaryM](https://boards.straightdope.com/u/GaryM)
#### Post date: [June 26, 2003, 1:18am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/9 "2003-06-26T01:18:44Z")
Boeing C17 can back up using engine thrust. They can land on a runway, cut to the left. or right, then back up, then pull forward and roll back up the runway. A neat three point turn! No expanded turn around area required. They can even back up a slope. Don’t remember the maximum angle though, but it’s respectable.
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### Author:  [@av8rmike](https://boards.straightdope.com/u/av8rmike)
#### Post date: [June 26, 2003, 1:58am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/10 "2003-06-26T01:58:08Z")
Also, there is an increased risk of [foreign object debris](http://www.aviationpics.de/fod/fod.html) ingestion when powering back. That’s generally why the practice is discouraged at crowded airports.
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### Author:  [@Xema](https://boards.straightdope.com/u/Xema)
#### Post date: [June 26, 2003, 3:48am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/11 "2003-06-26T03:48:17Z")
I heard a story a few years ago about an interesting pushback incident, supposedly involving a China Airlines Airbus at Narita airport.
A tug was not available so they decided to do it with engine power. They got moving a bit too fast and then hit the brakes a bit too hard. The engine-management computer interpreted the attitude and acceleration as a possible stall, and responded by closing the thrust reversers and firewalling the throttles. The aircraft slammed into the terminal building and suffered considerable damage.
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### Author:  [@bernse](https://boards.straightdope.com/u/bernse)
#### Post date: [June 26, 2003, 4:22am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/12 "2003-06-26T04:22:59Z")
Sounds pretty fishy to me. I can’t imagine why the autothrottle would be engaged on the ground. And even then, why it wouldn’t have engaged earlier if it was.
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### Author:  [@Robot\_Arm](https://boards.straightdope.com/u/Robot_Arm)
#### Post date: [June 26, 2003, 4:59am UTC](https://boards.straightdope.com/t/airplane-transmissions/184261/13 "2003-06-26T04:59:03Z")
Slightly off topic.
I did a college internship at a company that makes aircraft floats (the pontoons that you see on on the bottom of some airplanes that let them land on water). When you’re on the water, there are no brakes. If the engine is running, you can’t help but move forward. It makes the run-up checklist very interesting.
Most of the floats they built had wheels that would retract into the float (they call those “amphibious”, since you can use them on land or water). And there’s no way to run a steering linkage, so the front wheels swivel freely like a shopping cart. The only way to steer on land is to use the brakes on one side or the other.