tandemwings Nenadovitch

Nenadovitch sounds like Russian. It is. But he lived in France. I found very little about this man. But he is definitely worth mentioning in the tandemwing pages. He inspired a few true tandemwing designers.

I need to thank Paul Deweer, Pierre Mignet and Christophe Meunier for the info I have.

Nenadovitch's G.A.L.C.A.
The only drawing I did find of Nenadovitchs work.
Look further to see "modern" variants.
(sorry, I can not recall who gave me this drawing)

First a short overview of the history to better understand the reason why Nenadovitch invented his "tandemwing".:

But, all designs had the same problem. The first wing affected the rear wing. This came to view when the airplane changed its angle of attack. In other words, when the pilot raised or lowered the airplanes nose. Flight behavior went from good to VERY bad. The prototypes were very dangerous airplanes to fly due to that problem. [Note: later I got a mail from Eric Cousin, who flew a large Peyret model. He wrote that he didn't encounter that problem]

Nenadovitch searched and found a solution to this problem. He raised the position of the front wing. It made that the interference of the front wing towards the rear wing changed. Instead of a bad interference it became a good interference. "Huh?", you think. To better understand I translated a part of the book of Henri Mignet "Le sport de l' Air".

PART OF BOOK "Le Sport de l' Air" by Henri Mignet.
I made it a bit my own version.

Normally the air sticks to the upper surface of the wing. Stall is that moment where the condition of the wing is such (low speed, high angle of attack and so) that the air cannot longer stick onto the upper surface of the wing. Normally a wing start to fall like a brick at this point. Not so healthy!

Question: What will happen if you place a wing near the end of the stalling wing? (Condition is that the second wing has not reached stall)
Answer: The second wing has a area of low pressure on its back. Place a area of high pressure nearby and the air will be sucked towards the low pressure area. (This happens too at the wingtips and there they create the "vortex")

Here you see two wings. The front one is having troubles.
It is in stall. The air no longer follows the upper side of the wing, it is in turbulence..
The second wing is in a normal condition.
Under the wing there is a area of high pressure, above it is a area of low pressure.

Ever opened a door inside a house when there is a door open at the front and the back? Well, what do you get? DRAFT! A strong air current. It is created by differences in air pressure. Yep, there can be a difference in air pressure between the frontdoor and the backdoor. Henri Mignet tells here a bit the same about wings. The air runs from high pressure to low pressure.
Now look at the drawing above. Each wing has a high pressure area and low pressure area. High pressure below, low pressure above. Watch closely. The area of the lower side of the front wing and the upper side of the rear wing are close to each other. What do you expect? Right ... draft! The air from the lower side of the front wing runs quickly towards the upper side of the rear wing.

"OK, but what now about that stall thing?", you ask. Just look at the drawing above. See the draft between both wings? Now, the current takes also part of the air from the upper side of the front wing with it. "Hey, was that air not in turbulence?", you ask. Yes, but now no longer. It starts to flow towards the rear of the second wing. To do this ... it has to follow the upper side of the front wing.
TATAAAA. Stall delayed!

The air over the rear wing is ... secondhand. Already used. It has run over and under the front wing and has slowed down a bit and changed a bit in direction (a bit more downwards). Due to these changes the rear wing is less effective. To increase efficiently, you need to put the wings further apart.

Henri Mignet made use of both ways. His moving front wing made the voluntary way possible. Nenadovitch only used the automatic way. Let's look at it more closely. Look the drawing below.

Both drawings have the same fixed wing combination. But the first one is pointing a bit downwards (small negative angle of attack) and the second one has a large positive angle of attack (=angle between wing and wind direction).
The first condition has a gap (gray area) which is smaller than when the airplane would be flying straight forward. The gap is smaller, so the efficiency of the rear wing is less. The tail of the airplane sinks. The airplane returns to its normal position.	The second condition has a larger gap (gray area) and a resulting more effective rear wing. It has more lift than normal and it pushes the tail of the airplane upwards. The airplane returns to its normal position.

I hope you now better understand the good stuff about this kind of tandemwing. Nenadovitch used his tandemwing with a classic horizontal tail. Maurice Delanne and Henri Mignet drove the idea further into a pure tandemwing. No more classic horizontal tail!

On this page I can show a few more airplanes, which flew, and who use the Nenadovitch concept with a horizontal tail like Nenadovitch did.

Christophe Meunier mailed me a quote of a article about later designs with a Nenadovitch wing configuration. Pity, it was not noted from which source it came. Anyway, I translate:

"Eliminating the risk of loss of speed, longitudinal autostability, easy steering and low costs. These advantages are part of a four-seater design by Jacques Lagarde. It was built by the atelier Bordeau. The designers inspiration came from the work of "Institut Aéronautique de Saint-Cyr" (Institute of aerodynamics of Saint-Cyr) about the brevet (=patent?) of Nenadovitch. The prototype (F-WEPK) (webmaster: probably the Milet-Lagarde ML10) was followed by the S.C.A.M. C50 "Milane" II (F-WEAI). Flight tests were done by Gérard Henry in Cormeilles-en-Vexin."

Millet - Lagarde ML. 10 (probably F-WEPK)
Span	10 m	Speed (maximum)	235 km/h
Length	8 m	Speed (cruise)	210 km/h
Height	2,70 m	Ceiling	6000 m
Wing area	30 m2	Range	2000 km
PT (Weight total??)	1600 kg