Would the front rudder of the Wright brothers really have helped in recovering the glider from a stall?

Question

I have found a paragraph in the 1904 British patent of the Wright brothers (see the citation below) and it seems, from what they explain, that the two inventors believed the front rudder could have recovered the plane from a stall in any situation.

The question is, why were they so sure that after a stall the plane would have started to fall nose down, would have accelerated and the front rudder would have been able again to control the pitch of the flying machine?

If the main wings (and also the front rudder) had stalled their glider/airplane could have started to fall sideways or tail first.

"Contrary to the usual custom, we place the horizontal rudder in front of the main surfaces or “wings” at a negative angle, and use no horizontal tail at all. By this arrangement we obtain a forward surface which is almost free from pressure under ordinary conditions of flight, but which, even if not moved at all, becomes an efficient lifting surface whenever the speed of the machine is accidentally reduced very much below the normal, and thus largely counteracts that backward travel of the centre of pressure on the main surfaces or wings which has frequently been productive of serious injuries by causing the machine to turn downward and strike the ground head on." Wright brothers, “British Patent No. 6732, A.D. 1904 – Improvements in Aeronautical Machines”, Date of Application: 19th Mar., 1904, Accepted: 12th May, 1904. Wright glider

Answer 1

No, it would not have helped by itself.

What could prevent a stall or recover the aircraft from an incipient stall would be a counteracting movement of that canard surface, but that would need to be commanded by the pilot. It makes little difference if that control surface is ahead or behind the wing as long as it has enough lift potential left to produce the desired pitch down moment.

The way we understand stability today is that the aircraft will correct a deviation from the desired pitch attitude without pilot intervention. Using this definition, the Wright Flyers were unstable. Only by active and permanent corrections could straight flight be maintained. This is rather stressful and makes longer flights very tiring. Flying faster also can be ruled out because the speed of deviations goes up with flight speed, such that the human reaction time delays corrections too much and can even make them counterproductive.

The Wrights were correct that an unloaded surface gives them the highest control authority and, when moved in a correct and timely manner, helps to prevent a stall. However, placing that surface ahead of the wing comes with several disadvantages, loss of stability being only one of several. On the other hand, placing that lightly loaded surface at the rear results in a stable aircraft with better performance.

Answer 2

They are describing the Flyer's canard configuration. The canard surface is the "horizontal rudder". The wing airfoils they and others were using at the time had very strong pitching moments at stall AOA (due to the constant curvature or arc of the profile as you can see in the sketch), that would overpower the downforce of a horizontal tail, or even cause the tail itself to stall, and pitch the plane over violently.

The Wrights found that an up lifting surface at the front could deal with this (that is, resist the pitching moment of the main wing) better than a down lifting surface at the tail. It was a solution to a problem they faced caused by the airfoil they were using.

The price of this was a very twitchy craft to fly in pitch because the canard had little in the way restorative forces itself due to the way it was mounted, so it had to be consciously held at a desired position, which they lived with and got used to. Like with wing warping, they had little stability, but lots of control (too much in the pitch mode, you could say, as as result of making the canard big enough to resist the wing's pitching moment), which is what wowed observers, who were impressed with the control while unaware of the pilot's struggle with pitch stability when it was flying.

Later development of airfoils with better managed pitching moments (by moving most of the camber forward) made aft tails less problematic and the advantages of the aft down-lifting tail won out. The canard faded from the scene, only to reappear occasionally, with mixed success.

Answer 3

What they had was a further called canard configuration with the horizontal stabilizer ahead of the wing. They stated that the stabilizer is angled negatively and not loaded in normal conditions.

The center or pressure is located 1:3 of the wing cord towards the leading edge. For this reason in flight the wing has a tendency to tilt up, pitching the nose of the craft towards the sky. If left uncompensated by the horizontal stabilizer, the wing will fly at high angle of attack, will loose speed and stall.

To avert that situation, they devised the forward stabilizer meant to forcibly keep the nose down. Situation in which the wing gains speed, lift increase, the wing pitches (the nose) up, the drag increases, the wing slows down, the lift decreases, the nose pitches down. They must have optimized the design to the point where these nose oscillations were canceled at least in normal flight.

About horizontal stabilizers

The positive angle of the aft stabilizer contributes to maintaining the nose down after the wing stalled. This must have been known by Wright brothers.

The negative angle of the forward stabilizer used by Wright brothers maintains the nose down before the wing stalled, practically inviting the wing to speed up. However the wing would pitch up while speeding, which in the event of overcoming the forward stabilizer, will lead to higher drag and slow down.

As long as the wing was not able to change speeds too fast, the self control of the pitch worked way better with the forward stabilizer.

Answer 4

NO, the Wright British Patent No. 6732 appears to deal with post stall control of the aircraft.

Though 1904 A.D. is a long time ago, a modern wings center of lift still shifts backwards to the center of the wing after it stalls. Even their curiously proto laminar/Davis design thin undercambered wings had a center of lift further forward at lower AOA "unstalled".

Notice you don't see an airspeed indicator on that aircraft. At this early stage, stalling was a frequent occurrence, and, at low altitudes, would result in a ground impact.

The design only had value in perhaps softening the blow from a nose in to a belly flop post stall impact, but actually hindered stall recovery.

As designers began to better understand proper relationships of center of pressure to center of gravity, then they came to realize that this post stall pitching down behavior actually helped unstall the wing faster, helped even more by placing the horizontal stabilizer in the back of the aircraft, as the Wrights did on their successful Model B.

This lead to the modern solution to deal with stalling: avoid it at low altitudes with airspeed and AOA instruments, and pitch down to unstall your aircraft, which works at altitude. Simply do not accept even controlled crashing as part of your flight envelope.