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In the question Is the location of an aircraft spoiler really that vital? the accepted answer states "Surfaces behind the CoG act as stabilisers, keeping the nose pointing forward. An aeroplane has vertical and horizontal tail surfaces at the back just for this purpose."

I agree that this seems straightforward, to a layman (me). So why then were so many of the first aircraft built 'backwards'. Taking a look at the Wright Flyer

Image Copywrite Bay ImagesImage (C) Bay Images

as an example. There are many other examples from the earliest days of aviation. Why did many put the elevators up front, thereby destabilizing the whole thing?

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    $\begingroup$ Could you provide some of the many other examples? $\endgroup$ – zymhan Jun 25 at 18:48
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    $\begingroup$ @zymhan: 14bis by Santos-Dumont, Voisin - between 1903 and 1907 all successful motorised aircraft had the horizontal "tail" up front. $\endgroup$ – Peter Kämpf Jun 25 at 20:21
  • $\begingroup$ That's a huge horizontal stabiliser! $\endgroup$ – Koyovis Jun 26 at 1:47
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    $\begingroup$ Speaking of why, it's because the maker of this plane doesn't quite understand aerodynamics (not many people do at the time) $\endgroup$ – user3528438 Jun 27 at 15:23
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    $\begingroup$ I feel like there's something to be said for having the moving parts in front of the pilot where he can see that they're working reliably, at least when you're still in the experimental stages of design like that. Also, there's an analog to the most popular mode of transport of the time, that being the horse-drawn carriage. The things pulling and steering the vehicle (horses/elevators) were located at the front, under direct control of the driver/pilot). This would be the natural evolution of that idea. It took much experimentation to learn that other arrangements were superior. $\endgroup$ – Darrel Hoffman Jun 28 at 20:40
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"Backwards" is relative, there are modern aircraft that have forward placed elevator i.e. canard designs that fly quite successfully

military aircraft with canard, Saab 37 Viggen

(source)

As for why its not more popular you can read up more on that in why are there no production canard GA aircraft? and Why is the Tu-144 the only commercial airplane with canard configuration? as well as in the answers to lots of 'canard' questions on this site.

As for why the Wrights did it this way, NASA offers an explanation

The placement of the elevators at the front of aircraft is rather unique for the Wright flyer. Modern aircraft typically have the elevator at the rear, attached to the horizontal stabilizer. The Wright's placed their elevator at the front to provide protection to the pilot in the event of a crash. (The pilot of this aircraft lies next to the engine on the lower wing.) But there is also a static performance advantage when the elevator is placed forward. Lifting wings have a natural tendency to flip tail over nose because of the way the pressure is distributed.

So they were not necessarily backwards so much as different considerations were taken under advisement during the design.

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    $\begingroup$ Unique? And what about the 14bis by Alberto Santos-Dumont? In 1906, 100% of flying machines were canards - hardly unique if you ask me! $\endgroup$ – Peter Kämpf Jun 25 at 20:08
  • $\begingroup$ Lilienthal had a special "Prellbügel" (bumper bar) fixed to his gliders to absorb potential crash loads. That saved him several times. Unfortunately, on that fateful day in August 1896 he left it off … $\endgroup$ – Peter Kämpf Jun 25 at 20:29
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    $\begingroup$ Shockingly bad grammar from NASA there. $\endgroup$ – OrangeDog Jun 26 at 14:12
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I am not sure you are correct that most early planes placed the elevator at the front. For example, Otto Lilienthal's gliders had the tail at the rear.

The Wright brothers were strongly influenced by Lilienthal's work, but were also very anxious to avoid his fate, and believed they would obtain control he lacked by placing the elevator at the front (amongst other things).

It turned out that their Flyer was in fact very unstable, and difficult to control well - but controllable enough.

They also apparently felt that a tail at the rear would be more susceptible to landing damage.

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    $\begingroup$ Alphonse Penaud and Lilienthal had the tail in the back, correct. But Santos-Dumont in 1906 and Gabriel Voisin also put the horizontal tail in the front (the Voisin designs had two, one forward and one rear, to be doubly sure they can be stabilized). So in the short period from 1903 to 1907 all aircraft had the tail in front. $\endgroup$ – Peter Kämpf Jun 25 at 20:15
  • $\begingroup$ "One forward and one rear, to be doubly sure they can be stabilized" Yes, it was the early days. Unfortunately for aircraft pitch stability, the forward will cancel the rear and we're back to square 1. We must remember "tail" functionality regarding directional and pitch stability MUST be aft of the CG. The elevator (essentially a pitch destabilizer) can be placed fore or aft. $\endgroup$ – Robert DiGiovanni Jun 27 at 6:30
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It's not destabilizing to put the elevator or horizontal "tail" in front, as long as you place the CG sufficiently forward that a large portion of the wing itself is well behind the CG and effectively acting as a tail. The fact that the forward elevator or canard is trimmed to generate positive lift, is what allows you to place the CG well forward in this manner.

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  • $\begingroup$ Now, another related question-- why did the Wrights place vertical "curtains" in front of the CG (forward of the pilot) on some of their aircraft? It never made much sense to me. $\endgroup$ – quiet flyer Jun 25 at 17:11
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    $\begingroup$ Also, the answer could note that the Wrights configuration tended to avoid a bad nose-drop in a stall. $\endgroup$ – quiet flyer Jun 25 at 17:31
  • $\begingroup$ Also this answer could reference the Wrights' concerns over Lilienthal's experience as has been nicely pointed out in another answer. $\endgroup$ – quiet flyer Jun 25 at 17:40
  • $\begingroup$ "as long as you place the CG sufficiently forward" – yes, but the Wrights forgot about this part. $\endgroup$ – Peter Kämpf Jun 25 at 20:10
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    $\begingroup$ @quietflyer: Having an stalled aircraft assume an attitude where it can't gain airspeed is a guarantee that almost any stall will force an involuntary landing, but limit the speed at which the landing will occur. $\endgroup$ – supercat Jun 26 at 20:47
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Remember that the aviation pioneers were inventing the skills required to fly while refining their designs. It would be a great help to actually see the position of the elevator while trying to relate its movements to the results. We relate control pressures (which we sense in our hands and feet) to the aircraft movements to sense how we are doing and we learn that from instructors and through practice on well designed aircraft. The Wrights were trying to figure it all out as they went.

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    $\begingroup$ Its probably worth remembering that the majority of design work in those days was trial-and-error rather than mathematical analysis $\endgroup$ – Mike Brockington Jun 27 at 14:30
  • $\begingroup$ I was recently at the Smithsonian Air & Space museum and watched a video about this. They used a ribbon tied to the front of the aircraft as an early instrument. A sense of balance, like that required to ride a bicycle, was a large part of early flight! $\endgroup$ – Wayne Werner Jun 28 at 16:41
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They were not backwards, they had a huge horizontal stabiliser at the aft section!.

Angular accelerations are relative to the CoG. If there is only one aerodynamic surface, it must be behind the CoG in order to self stabilise. If there are two of them, like in the plane through the Y-axis, basically the same stipulation holds: that the total centre of lift is behind the CoG.

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