Why an aeroplane from ladders?
Aviation and piloting have been a passion since my childhood: pilot of gliders and aeroplanes, gliders instructor (1200 hours flying in 10 years), devoted to building to be able to fly since...a long time. I know amateur aircraft construction, I built a glider during my engineering studies. It took 2,080 hours. Too long. MUCH to long.
Build faster. I did that as a professional: 1200 hours for a sailplane (JP 1536). Amateur construction of an aeroplane takes at least 1,000 hours: still too long.
I remained immersed in Aeronautics with a big A and in advanced composite materials for years. Until inspired by an experience in a large discount store : I discovered a display of aluminum ladders 2.65 meters long for about $25.
Building on the ideas accumulated while flying, I arrived at the concept : a ultralight (ULM) from the ladders. The rupture calculations for the ladders was only 25 daN/mm2 rather than 40 (AU4G), but I didn't intend to build an Airbus.
The design began in 1997 with two major principles :
I applied for and received a patent in 1998, n°27760222. The calculations and construction plans are now finished.
After the manufacturer of the ladders raised insurance concerns, the design now uses rectangular aluminum tubes that are even easier to work with, cheaper and stronger.
Thus arrived the Pouchel. "Pou" for the Mignet formula Pou-du-Ciel (usually translated into English as the Flying Flea). "-chel" for "échelle", the French word for ladder. The "Ladder Flea".
Why an aeroplane using the Mignet Pou-du-ciel formula?
First of all in tribute to Henri Mignet who is the father of amateur aircraft construction, not only in France but worldwide. Further, simply because the ladders would not support a wider wing span.
Nowadays, in France, amateurs construct two times more aeroplanes than are produced commercially.
Several thousand aeroplanes following the Mignet formula have been constructed around the world. The Mignet formula aeroplanes have two off-set wings with no ailerons or flaps. The stall is very smooth and previsible because of the aerodynamical configuration of the wings.
So what are the problems?
Details... Piloting is not standard. Pitch control is accomplished by changing the incidence of the front wing by direct action of the stick. This allows for precise, immediate pitch control but pilots used to the standard configuration find it a bit disconcerting in the beginning. The rudder alone produces perfect turns. The stick controls both the incidence of the front wing and the rudder, no rudder pedals. Point the stick where you want to go and the Pou-du-Ciel goes there.
The first Mignet aeroplane, the HM-14 Pou-du-Ciel of 1934 only weighed 130 kg, a ULM already.
On page 108 of his classic book : Le Sport de l'Air (The Sport of the Air), Henri Mignet wrote :
" Amateur flying is a problem
A fundamental truth: anything that flies must be light : Light implies small. Small only requires low power. Low power implies: low cost.
Voilà, the Pouchel.
The test flights
The Pouchel made it's first jumps on the March 14th 1999 on the runway of Salon Eyguieres.
For the tests, I followed the method of the book : "Sport de l'air" by Henri Mignet, it means a lot of taxiing to get used to the machine.
The first jumps were more like the ClÃ©ment Ader's "Eole" than like a real ultralight !
A rev-counter was installed and surprise ! The FUJI 18hp engine wasn't exceeding 4500rpm, so around 12hp ! The propeller pitch was good, then we worked on the engine... New carburator, exhaust pipe checked, but the results weren't good enough and the take-off was always too "borderline"
Then the company HALTER lend a propeller, the engine was raising to 5200rpm.
The "Mondial de l'Air" came faster than expecter and the test flights can't be continued further. The Pouchel had a great success during the show and was always surrender by visitors. Nobody was uninterested by the Pouchel : admiration, smile, scepticism... After the show, we continued the tests with the new propeller, but the take off was still too hard....
Then a moment of thinking came afterwards... The 128cm prop is blowing under the wing and it can implies air circulation with a lose of bearing capacity on the central section of the front wing.
Two possible options :
- Increase the horsepower (change of engine and propeller) to be faster. The bearing capacity is increasing by the square of speed. But it's an expensive solution...
- Increase the wing span because it would implies a raise of surface and of course of bearing capacity
We choose this option because we just have to add some small pieces of aluminium ladder with their polystyrene rib and cover it with DIACOV (2 days of work).
Heading to Salon Eyguieres on June 26th 1999 at 6' AM.
After a few easy take-off, I decide to make a big flight with my Pouchel, so critisized - no dihedral, no tension coating, lack of resistance of the fuselage alone...
The Pouchel is climbing alone, I push the stick to the right, and it's turning immediately to the right. I push back the stick and the Pouchel is flying back to the horizontal (she's nice !). I make a big turn around the airfield and I come back in the runway axis, the flea is really obedient, high speed fly-by (around 100km/h); I slowly pull up while turning right and I'm flying an another pattern. I take a look to the wind sock. Well... there's some cross wind. No panic, there's two runways at Salon Eyguieres.
Face wind approch, perfect landing but I hear a little metallic noise in the engine. Taxi with the starter... The fixation of the starter command is broken, and the support of the air filter... and the air filter (!) are gone... But nothing really bad.
New start of the hot engine. I decide to work on the take-off and landings with the cross wind. The behaviour on the ground is perfect thanks to the tail wheel. The airborne behaviour is also excellent, level-flight speed is more that 95 km/h, minimum speed around 45 km/h, and the turns are like those of the HM-1000.
Even without any dihedral, the aircraft can turn (thanks to Jacques Langlois who encouraged me to make a wing without dihedral).
The engine at 5200 rpm only have 15hp, so with a span increase on the rear wing, the flight could be possible with a paraglider engine.
The POUCHEL is the first PULMA multiaxis which belongs to the new ULM reglementation (170 kg).