# How important is symmetry to plane engines? **URL:** \ **Category:** Factual Questions\ **Created:** [March 12, 2010, 11:28pm UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307 "2010-03-12T23:28:23Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [March 14, 2010, 11:57pm UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307/21 "2010-03-14T23:57:51Z")
> [@rockypg](#): > > If one engine in a two engine plane fails, the symmetry is lost, the thrust is generated on one side and the rest of the plane drags on the other side. What compensation is required to keep the plane flying in a straight line? banking? ailerons? Tail flaps? Rudder trim would be very important where the thrust is so dramatically asymmetric. Even small single-engine planes often have a trim tab on the rudder, but it’s fixed in place by an engineer and the pilot doesn’t touch it. But multi-engine planes have rudder trim that is adjustable in flight. I’m not sure if you’re joking about “tail flaps”, but those movable control surfaces at the back of the plane are the elevators. Flaps are extensions of the wing that increase lift and drag (they’ll allow you to climb and descend more steeply). Flaps and elevators are always symmetric if they are operating correctly. ---
**Author:** ![UncleBill](https://avatars.discourse-cdn.com/v4/letter/u/d26b3c/32.png) [@UncleBill](https://boards.straightdope.com/u/UncleBill)\ **Post date:** [March 15, 2010, 2:25am UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307/22 "2010-03-15T02:25:24Z")
> [@dracoi](#): > > Since the OP has been answered, I thought I’d comment that symmetry is not important just to the engines. > > The A-10 Warthog’s 30mm Gatling has such a kick that putting it even slightly off-center would throw the plane into a spin when it fired. Even more modest guns are generally centered or paired for this reason. The A-10 Thunderbolt’s main gun’s firing cylinder being centered has more to do with keeping the nose (and gun) on target than avoiding a spin, it would need to be quite a bit outboard of center to cause the aircraft to lose control. ---
**Author:** ![kdeus](https://avatars.discourse-cdn.com/v4/letter/k/b487fb/32.png) [@kdeus](https://boards.straightdope.com/u/kdeus)\ **Post date:** [April 27, 2010, 6:38pm UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307/23 "2010-04-27T18:38:21Z")
> [@lazybratsche](#): > > **kdeus** : What’s your first favorite line? (paraphrasing) “In the event of a fire in a wing fuel tank, structural failure may occur in as little as 45 seconds.”:eek: ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [April 27, 2010, 6:51pm UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307/24 "2010-04-27T18:51:50Z")
> [@Gorsnak](#): > > You’ll be thinking of some aircraft designs by [Blohm & Voss](http://en.wikipedia.org/wiki/Blohm_%26_Voss_BV_141), I think. Well, now I know where the got the idea for the goofy-looking [TIE bomber](http://en.wikipedia.org/wiki/TIE_bomber#Other_TIE_craft). ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [April 27, 2010, 6:57pm UTC](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307/25 "2010-04-27T18:57:23Z")
> [@garygnu](#): > > The reason behind Burt Rutan designing and building the [Boomerang](http://www.popularmechanics.com/technology/transportation/1289166.html?page=all) was to reduce the problems stemming from losing an engine in twin-engine craft. This post was a few weeks old, and that link now takes me to a generic page about sports technology. Is there a currently valid linky? [Previous page](https://boards.straightdope.com/t/how-important-is-symmetry-to-plane-engines/532307.md?page=1)