He got his inspiration after seeing the Westland P12 "Duo-Mono". This plane, which was a conventional airplane with a large tail, have the possibility to place the center of gravity (CG) more backwards. It wasn't a tandem, but that idea began to get shaped in Miles' brain. Persons who now think "Hey, it was a Frenchman who made the first tandem" need to read further. Mignet is also included in this page.

Miles' proposal for a Fleet fighter in 1942

I found in Air Enthusiast / number five (a magazine) the following list of advantages Miles thought to create with his tandem.

1. By locating the engine amidships to drive a pusher propeller, the pilot could be positioned in the nose and thus provided with the perfect, unobstructed view for deck operations.

2. The division of lift between two wings and the prospect of achieving an increased overall Cl (lift coefficient) made it possible to restrict the wing span to the size of the carrier lift and thus elimination the weight and complexity of wing folding.

3. The elimination of the conventional tail and the concentration of power plant weight near the CG would result in considerable reductions in both length and structural weight, which, in combination with (2), should also result in increased maneuverability.

4. Both foreplane and aftplane would contribute to total lift and consequently the parasite drag associated with a conventional tailplane would be eliminated - this often amounting to as much as 10 per cent of the total drag of a clean aircraft.

5. With the conventional wing-tailplane arrangement, the nosedown pitching moment associated with the center of pressure movement due to increased incidence calls for maximum negative lift from the tailplane at the very moment when the greatest overall lift is desired, but with the true tandem-wing arrangement the lift of the two planes would be additive and backward movement of the CP would call for increased lift from the leading plane to maintain trim.

This may sound like Chinese to some. So, let us review the lines.

1. Placing the engine behind the pilot would really improve the view of a pilot during landings. So see the W.W.II Corsair. If that engine didn't block the pilots view...

2. Hmm. Increase of total lift coefficient (C_l). I thought it would increase as well, because there no longer is a downwards lifting tail. But I don't have the numbers to justify or kill this thought.

3. This one puzzles me. I can understand that less weight leads to better maneuverability. Just imagine two bikes. One is a ordinary bike, the other is a bike with your sister on the back and your brother on the front. Which bike would perform best when riding a path in the form of a 8. The first of course! But I can not understand how a better total C_l can improve maneuverability.

Q: Can anyone clear this one out for me? A: (from J.T. Wenting / jwenting@hornet.demon.nl / www.hornet.demon.nl) As I see it, increased lift (Ci) will mean not so much increased agility, but the ability to maneouver at lower speeds, thus reducing landing speed, which is vitally important aboard carriers. In WWII aircraft, the high landing speeds were being seen as a problem, especially for carrier operations. Reducing landing speed would make the aircraft easier to handle during approach to a carrier landing. At the same time, the aircraft would become more agile during a dogfight, as those normally take place at relatively low speed (or if they start at high speed, that speed bleeds of as energy is consumed in turning.
An aircraft that can still maneouver at low speeds while it's opponent cannot, may well win out in a turning fight). As to landings, increased Ci can also decrease the nose-up attitude during landings, making the runway/carrier deck more easily visible to the pilot.
The US Navy made a hybrid out of this concept in the F-8 Crusader, by tilting the wing several degrees during landing to allow the pilot to remain almost level during the approach, thus allowing him a better view of the carrier deck then would have been possible otherwise given the high stalling
speed of the aircraft.

I got another remark about maneuverability by Evan L. Mayerle. It is not Cl related, but interesting to know anyhow. A: "Well, first of all, concentrating all your heavy items, like the engine, near the cg is going to reduce your moments of inertia so that a given input will get more output. By the same token, splitting the lift between two wings, especially if the split can be controlled or varied, can also enhancemaeuvarability. I don't think that an increased Cl can, of itself, increase maneuverability; however, it's been decades since I took any Aero. classes and my work has been mostly detail design, not overall configuration." The time when I did receive this mail the text above was not yet placed. So he could not have known about the relation J.T. Wenting mentioned.

4. I can understand that many would react "But the plane still has two surfaces?! ". OK, lets make a little experiment. Imagine that we choose a airfoil with a 10 % height / length ratio. Now, choose a certain wingarea (make it a round number to keep the calculations simple). Start drawing this wing in several shapes and calculate the frontal area. After a few drawings you will see that there is no change in frontal area. Even dividing the wing in 2 of more wings does not change the frontal area. Miles did divide the wing into 2. These two wings have their own compensation of the natural pitching moment of a wing. So they don't need to have a downwards pushing tail. No tail means less frontal area and that means less drag. But watch out with the experiment. There is a catch. If you change the chord length, you also change the lift a wing can generate. Shorter airfoils have lower lift/drag ratio. The maximum C_l becomes less. So drawing a wing the same wingarea but using a shorter chord will give less lift. To get the same lift as before you need to have more wingarea. More wingarea means more frontal area, more frontal area means more drag. Still Chinese? Give me a sign. I will insert more info on this item.

5. Translated to human language this means that if the angle of attack (AoA)( = the angle between the roll axis of the plane and a horizontal) increases the place of the lift force shifts more backwards. Really... it does! Conventional airplanes need to compensate this moment (generated by the lift force being more backward from the CG) with a increasing downward force at the tail. Because higher AoA are being used at landings, this is not ideal. At landings you need to get as much lift out of your airplane as it can get at those lower speeds. Tandems also get this extra moment, but they can compensate it by creating more LIFT on the front wing. Just as I like it.

Here two situations can be seen. First the cruising condition, second the tandem during landing while using a higher angle of attack. The lift forces have shifted backwards. The rear wing lift force is further away from the CG and generates a larger moment than while cruising. The first wing lift force is closer to the CG and has to be larger to compensate the moments. But anyway, here with tandems we use LIFT. Conventional airplanes have to use more downwards pushing force at the tail.

George Miles was very, very enthusiast about this tandem idea. Seeing his advantages, who wouldn't be? But would the plane be stable? He still had to prove. Miles knew this and made a proof-of-concept airplane to get support for his Fleet fighter proposal. He made the M 35 in 1942 as a private venture without the knowledge of the Ministry of Aircraft Production. Roll-out was at the end of April 1942 after only 6 weeks from the start of the build up. This was possible due to the extensive use of existing parts (NASA today uses this strategy as much as possible when making their X-planes).

Miles M 35. A proof of concept airplane. Build in six weeks.

Miles flew the plane himself on its flight flight. It nearly ended in disaster. It was very unstable around its pitch axis. Even after ballasting, which improved stability, the overall result was still not so good. But Miles thought it had proven his idea. Windtunnel tests would have showed this instability, but I guess Miles was in a hurry.
He didn't get official support for his Fleet fighter. But that didn't stop Miles. He proposed a tandem design, M 39, for the specification B.11/41. This was suggested by the Ministry who wanted a high speed, high altitude bomber possessing a range of 2414 km (1500 miles) at an altitude of 9145 m (30 000 ft) and a bomb load of 1814 kg (4000 lb.). Miles didn't get official support again. But Miles wouldn't be Miles if he didn't make a scale model as a private venture. This scaled-down (5/8) airplane, the M39B, was a twin-engined airplane with its engines mounted on the rear wing. A unusual thing to do at those days.
The wings were changed from position when related to the M35. The front wing was now placed lower and the rear wing was placed higher. This was simply because the prop needed ground clearance.
The ratio between the wingareas changed also. The M35 had a ratio of 1:2, the M39B had a ratio of 1:3. This change was done after the first evaluations of the M35.

Miles M 39 B with its unusual engine configuration.
It has a higher wing area ratio between both wings as the M 35.

After viewing the M39B the Ministry got interested in the tandem design and bought the plane to test it.

Now let us see the situation. We have two wings. How would you position the control surfaces? ... Miles did it as following: flaps on both wings, elevators on the front wing, ailerons on the rear wing and rudders at the wingtips and there also was a non-moving tail at the end of the fuselage. Elevators and ailerons were positioned next to the flaps, which were placed next to the fuselage.
How did this influence the flight characteristics? Well, on the ground all was well, thanks to the threecycle landinggear with steerable nosewheel and rudders, which were placed not in the propwash. Conventional airplanes have a tendency to swing because their tail is placed in the propwash (see drawing in the asymmetric section). The M39B did not swing.
The double flaps were something complex. The front flap made nose-ups, the rear flap made nose-downs. They had to be used together. Positive news was that if they were positioned correctly take-off occurred without moving the stick at 109 km/h (68 mph) and this flapsetting could be used during the climb. Sounds rather easy to me.

But the thing that interested the Ministry was its stall behavior. You couldn't stall the M39B if the flaps were placed in its neutral position. The Ministry asked more tests to explore this non-stall behavior. Pilots founds out that it got lost when flaps were being used. It was even so that if the M39B stalled, it happened without warning! So it was good news and bad news. Later more about the good news (when talking about the design of Henri Mignet).
Tests were also done with one engine stopped. The loss of the port (left) engine could just be controlled, but the loss of the starboard (right) engine caused problems. Loss of a engine could lead to a very steep "graveyard" spiral, especially with the loss of the right engine.
Flying the M39B in turbulence was not a pleasure. But a landingapproach was a delight due to the good view (just as Miles waned). But the not so good rudder response made it hard to keep the plane in line with the airstrip during crosswinds. You had to use much rudder. Knowing that the steerable nosewheel was linked with the ruddercontrol, you can imagine the smack the pilot got in his leg when that (not in center) wheel hit the ground.

The M39B was a scaled down version of the bomber proposal of Miles. So it wasn't stressed for acrobatics. On one of the flight a pilot encountered some turbulence. He later said it felt like the cockpit wanted to break off.

It will not be a surprise if I tell you that there were no orders for the M39. In fact, the whole specification B.11/41 lapsed.

This story of a "new" (see later) concept, which didn't get orders but was build twice without official support, shows that a designer can sometimes be so enthusiast about his proposal, that he is blinded from the fact that there is still a lot of work on the design.
Just to mention: Miles' firm went into liquidation in 1948. Was it his stubborn behavior or the fact that after the war there were no more demands for airplanes. I don't know. All info on that item is welcome.

You might think now that the tandem concept isn't worth a penny. Well, you are wrong. There are some successful tandems out there. One of them is the "Pou de Ciel" (Flying Flea) of Henri Mignet.

The Mignet HM 1000 Balerit, a later development of the first "Pou de Ciel"

To my knowledge the first tandem was the "Pou de Ciel" (1933) of the Frenchman Henri Mignet. It was his fortheenth design. That's why it did received the designation HM-14. Compared to the design of Miles you can see the following differrences. The HM 14's front wing is larger than the rear wing. The horizontal distance between both wings is smaller. The single vertical is placed on the fuselages end. The pilot is positioned between the wings. A classic landinggear is used. The front wing does not have elevators, but the whole wing rotates. The engine was placed in the front.

Using this configuration it made Mignet possible to create a compact, light, cheap, easy to build airplane. At the same time Henri Mignet wrote his book "Le sport de L' Air". This book also contained the plans to build a HM-14. The English translation sold over 6000 copies! Soon there was a real Flea fever. Abouot 600 FLying Fleas were built. All went well.. but then came the crashes. Several HM-14 fell out of the sky. The accidents were caused by a design mistake. Mignet placed the pilot behind the center of gravity (CG) and if a lighter pilot flew the airplane the nose couldn't be kept up. Several pilots dove to their death. Mignet quickly redsigned the HM-14 by adding a flap to the rear wing. Mignet created a nose-up with this flap, just like the flaps on the rear wing of the Libellula. But allready many countries grounded the Flying Fleas. And quickly the Flea fever died. But this didn't stop Mignet. He kept designing tandems.

I found some info about the HM 1000 "Balerit", a very popular ultra light two seater (empty weight 174 kg (383 lbs). I am not sure that this one is designed by Henri, it could be done by a son. Kruhmin Nikolas did confirm this thought.

Sure is a eye-catcher this HM 1000 Balerit.
You can see the propeller, which is placed in between the two wings.

Like most Mignet designs it has two controlled axis (no ailerons). And I noticed that there is no longer a flap on the rear wing. So I guess that the designer placed the pilots (seated next to each other) on top of the CG.

After this bit of history, let's look at the design of the HM 1000. It doesn't stall either. We sure need to look deeper into this item. Here the elevators are placed in the wing, which stalls first. When stall occures, the elevator can not longer keep the nose up. So, the nose drops lightly. As soon as the elevator gets lift again, the elevator works again and the nose rises again. This doesn't lead to a stall with a severe heightloss, but to a controllable (but steeper than normal) descent in a wave shape. And that sounds rather safe to me for a beginner pilot ( and all the others).

Marske uses this system as well on his flying wings. Go see his designs at www.continuo.com/marske. His flying wings stall first at the section next to the fuselage. Now guess what is located in that section. Right,... the elevators!

Now let's see the other design features on the HM 1000. Miles choose for a larger rear wing, Mignet for a larger front wing. What is the advantage of Mignets choice? Well, here I have no books or articles about. So, let's use logic. Miles designs had a CG, which was placed nearer to the rear. Mignets CG is placed more to the front. This fact influences the placement of the rudder. Miles couldn't place his moving rudder on the end of the fuselage. It wouldn't be effective enough. He had to place the rudders at the wingtips (the rudder on the end of the fuselage wasn't a moving one). Mignet placed his rudder a bit after the rear wing. The distance between rudder and CG is larger and will be mor effective. I guess it does take less extra weight than the reinforcement needed to place the rudders on the wingtips. Anyhow, the distance between rudder and CG will be smaller on a tandem than on a conventional airplane. So, a tandem will always have a larger tail. The Quicky is a exception. The designer did make the fuselage longer and placed a normal tail.

Here you can see the basic differences between a tandem with a larger first wing and a tandem with a larger rear wing. The place of the CG is different and the distance between the CG and the tail is different.
Both compensate the turningmoments of both wings by having extra lift in front of the CG. "Extra lift" means here that the lift forces generate a turning moment (in opposite direction as the turning moment of the wings) around the CG. Normally one would expect that these forces would be neutral around the CG.

The distance between both wings is smaller in Mignets design in relation to the Libellula. The conciquences of this decision are positive and negetive. Positive news is that the design is very compact and very light. Like a testpilot mentioned before, Miles had problems with the fuselage of the Libellula. His fuselage should be made heavier to hold the high lift forces, which are placed further away of eachother. If a tandem would be made with a looong and light fuselage and a large distance between both wings, it could snap in two on the first turbulence. Negative news is that, if the distance between the wings is short, the distance between CG and the elevator is also short. So you would need more deflection of the elevator to steer the airplane around its pitch-axis. Trim drag becomes high. High performance will not be possible in this configuration. But it makes a good configuration for a cheap, light, compact airplane. The sales of Mignets prove it!

Oh yes, I nearly forgot. The HM 1000 has a very unusual place for its signle propeller. It is placed between both wings. It makes a centered weight position (by placing the engine near the center) possible.

The HM 1000 Balerit did prove his value in several events.

By some luck I ran into the official site of the Mignet-plant. It is http://avions.mignet.free.fr/ . I did see for the first time that there is a more advanced version of the Balerit, the Cordouan. It has a enclosed cockpit now, which also was a option on the Balerit, but here there is no longer a main tube frame. You could call it a fully "tranditional" version of a tandem.

The Mignet Cordouan, the advanced version of the Balerit.
Also is visible the folding system which is also used on the Balerit.
It takes very short time to get it folded or unfolded.

If you like to know more about the Mignet, please contact the Mignet-plant at avions.mignet@free.fr

Want to see more Flying Fleas? Go see www.valkyrie.net/~flyingflea/. Here is a picture gallery of finished home-builded Flying Fleas.