# Turbo Prop airplanes **URL:** \ **Category:** Factual Questions\ **Created:** [March 14, 2007, 4:32pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901 "2007-03-14T16:32:49Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [March 14, 2007, 4:32pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/1 "2007-03-14T16:32:49Z")
I was on one of these on Saturday. There is a spinning propeller on each wing. I was on the left side of the plane and noticed that the propeller spun clockwise (when looking forward). I couldn’t see the propeller on the right side. Does the right-side propeller spin in the same direction, or does it spin counter-clockwise (with a mirror image shape)? Whatever the answer, would the plane still fly if the alternate was true? ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [March 14, 2007, 4:38pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/2 "2007-03-14T16:38:43Z")
If the other propeller rotated in the opposite direction, it would only need a propeller that was pitched differently to provide the thrust in the right direction. In other words, the propeller would be a mirror image of the other one. They would be identical opposites, if that makes any sense. ---
**Author:** ![GusNSpot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gusnspot/32/436_2.png) [@GusNSpot](https://boards.straightdope.com/u/GusNSpot)\ **Post date:** [March 14, 2007, 4:57pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/3 "2007-03-14T16:57:20Z")
Depends on the plane. Some are both clockwise, some are both counter-clockwise, some are with the descending blade inboard and some are with the descending blade outboard. Applies to all propeller driven airplanes. All combinations work. From a pilots perspective, counter rotating props with the descending blades inboard is often considered best due to the better ability to fly with only one engine operating. (Big long discussion omitted.) Some bigger aircraft actually have 2 counter-rotating propellers on each engine. On 3 - 8 engine turbo-prop aircraft, they usually all turn the same way. On piston engines, the US built engines usually run clockwise viewed from the rear and Britt engines usually run counter-clockwise, Most regional carriers in the commercial fleet theses day have engines that turn the same way on a particular aircraft. (Depends on who built the engines that are used.) It is cheaper in the long run. One of the ‘Big Iron’ guys will come along and give a better account of what is actually being flown on the line in todays world. My information about current aircraft of the regional level is limited. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [March 14, 2007, 5:57pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/4 "2007-03-14T17:57:49Z")
As **GusNSpot** notes there is a handling advantage to counter-rotating engines/propellers. This is mitigated by the spares/maintainance issues that arise with having mirror image parts on the same aircraft. In the case of a turbine, it would be cost prohibative to make the internal parts of the turbine in two variations, so the reversal would be done in the gear reduction, requiring an extra shaft, and that gearbox variation would require it’s own certification process. A piston “engine” can be reversed with only a change of camshaft…if you exclude minor things like the oil pump, magnetos, fuel injection distributer, alternator, starter, etc. from the definition of engine. Overall, providing a reverse rotation power plant is such a collasal PITA that it is notable when it happens. The only examples I can think of are the WW-II vintage P-38 Lightning, and the 2 seater known as a [Derringer](http://www.kitcutters.com/RCM/RCMScale/RCMWing)The Derringer is so rare that I couldn’t find a photo of a full scale one on the web. The link is a model, and it probably does NOT have contra-rotating engines. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [March 14, 2007, 6:03pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/5 "2007-03-14T18:03:54Z")
Hamsters blew me out of the edit window. [Here](http://www.kitcutters.com/RCM/RCMScale/RCMWingDerringer.htm) is a working link. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [March 14, 2007, 6:11pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/6 "2007-03-14T18:11:50Z")
[QUOTE=Jackknifed Juggernaut] There is a spinning propeller on each wing. [/QUOTE] And to think there are people today who have never seen a prop-driven aircraft, let along flown aboard one. I bet they have never owned an analog watch, either. I feel sorry for them. ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 14, 2007, 6:12pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/7 "2007-03-14T18:12:21Z")
[QUOTE=Kevbo] The Derringer is so rare that I couldn’t find a photo of a full scale one on the web. [/QUOTE] [![](http://aerofiles.com/wing.jpg) ](http://aerofiles.com/wing.jpg) [![](http://www.skypark.org/images/WingDerringer.jpg) ](http://www.skypark.org/images/WingDerringer.jpg) [http://www.sti.nasa.gov/tto/spinoff2002/images/009.jpg](http://www.sti.nasa.gov/tto/spinoff2002/images/009.jpg) _Don’t give me a P-38, The props they counter-rotate, They’re scattered and smitten from Burma to Britain, Don’t give me a P-38…_ ---
**Author:** ![Johnny\_L.A](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/johnny_l.a/32/1084_2.png) [@Johnny\_L.A](https://boards.straightdope.com/u/Johnny_L.A)\ **Post date:** [March 14, 2007, 6:16pm UTC](https://boards.straightdope.com/t/turbo-prop-airplanes/395901/8 "2007-03-14T18:16:41Z")
[QUOTE=Duckster] And to think there are people today who have never seen a prop-driven aircraft… [/QUOTE] This reminds me of a Bob Stevens cartoon. A crusty old Colonel in a flight suit uses his hands to illustrate his position relative to an enemy (likely German, WWII) aircraft as he tells a story to a couple of Second Lieutenants. **Colonel:** There I was, hanging by my prop… **2nd Lt.:** What’s a prop, sir?