- Flying the Fauvel flying wings, by Christian Ravel. Translated by Jon
G. Beeker (firstname.lastname@example.org)
The following two accounts are based on flight experiences in recently built flying wings. They give a good picture of the flight characteristics of these machines.
Christian Ravel founded the GPPA. The purpose of the organization is the preservation of antique gliders and aircraft. It operates an air museum and maintains several machines in flying condition including an AV-22 and an AV-36. The following text affords a better understanding of the flight characteristics of these flying wings.
An Air Force officer, record-breaking pilot, and test pilot, Charles Fauvel (1904-1979) was one of the founding fathers of French sail plane flying. He is responsible, among other things, for the discovery the Beynes and National Center of la Banne d'Ordanche airfields. However, in spite of his intense activity as a pilot, inventor and engineer, he is better known for his accomplishments with flying wing gliders.
Throughout his life, Charles Fauvel was fascinated by tailless aircraft, more commonly called "flying wings." In the area of sailplanes, four machines remain: the AV-3 of 1931 and the AV-17 of 1938, both are the only example of their type ; the AV-36 single-place of 1951 and the AV-22, a two-place 1946 design although it was not constructed until 12 years later. The last two machines were produced in number, several hundred for the single-place and only six for the two-place.
While the machines are based on the same idea, the approach to building them is very different: the two-place AV-22 was originally intended to be a glider with a built-in launching mechanism and was built in a factory while the single-place, commonly called "la godasse" (the "shoe") on the flying fields, was primarily a light machine intended for amateur construction. Its success was certainly due to the fact that almost 300 sets of plans were sent to more than 16 countries and it is reasonable to imagine that about 150 machines have flown.
If the philosophy behind them is different, the same can be said of their appearance and the method of flying them. They cannot be confused under any circumstances. They are more like cousins than directly related like the Bréguet 904 which was directly inspired by the 901. The single-place "godasse" is quite small, sits low on its skid and twin fin while the two-place is enormous in all dimensions: a large fuselage and wings, a wheel (retractable, if you please) and a large single fin. These differences in scale and conception are naturally felt in the flying and use of the glider. I propose a flight with you to see what these little-known machines have in them. The simplest thing would be to proceed chronologically in the order that I experienced them and to fly the single-place, indicating the differences as necessary.
Getting the AV-36 out of the hangar cannot be accomplished without the little carriage, that is the B.O. (1) equipped with a handle which provides for excellent maneuverability and with two people it can be accomplished very easily, aided by the light empty weight of the engine, about 130 kg. The two-place has a wheel which makes moving it easier but it requires three people, two at the tail and one at a wing. The maneuver must be visualized in advance because the high fuselage prevents those carrying the tail from seeing the other side and it is easy to damage an aileron.
Taking the glider out onto the field is accomplished and now it is at the side of the runway. Whether it is the single- or two-place, the craft is a point of interest and jokes about old garbage cans that still fly are to be expected as well as a falsely casual interest in them. A number of our champions who swear by machines with L/D over 50 come to see what this strange wood and fabric (of course!) thing is that doesn't have a tail but which is supposed to fly. It is also at this time that we hear statements such as "You know, one day, if there wasn't something faster to fly... maybe, if I didn't have anything else to do, I might go around the patch in it."
Let's forget about our champions and their plastic planes and get into our curiosity. For the single-place it is a simple process like with the old Nord 1300 and the "Emouchet" (sparrow hawk). You fall into it and are surprised to discover that for a normal size man (1.85 m and 100 kg), there is ample space. It is well known that sailplanes are always larger inside than outside. For the two-place, while entry into the front seat is normal, a little like in the Bijave, it is not at all the same in the back seat where first of all you have to sit elegantly on the leading edge of the wing then slip into the large bucket seat which receives you easily. There, big surprise, the rudder bar doesn't move horizontally like they do in a real aircraft but move vertically like organ pedals. (This is really going to be exciting when it is flying in a minute!) Except for this strange situation, you are definitely in a Fauvel: the controls are accessible, the visibility seems excellent and, as long as you don't look in back, you would believe you were in a normal machine.
Originally, the single-place had two hooks on the leading edge to the right of the tail fins; a piece of in cable ran through a ring on the main cable forming a V (2). This solution was abandoned on most machines for reasons of ease of flying and functioning (you can imagine how funny it gets when one of the hooks lets go or when the V cable shifts in turbulence!). Consequently, in most of the Fauvel mono- and two-place planes, the simple solution of a single hook in the nose was used as with ordinary gliders.
Settled in, the cable stretches and take-off is imminent. Now it is important to remember the differences in behavior between the two gliders. The single-place has a tendancy to porpoise longitudinally on take-off. It is important to get it off the ground as soon as possible by holding a little backpressure on the stick, releasing it delicately as soon as you are in the air. For the two-place it's the other side of the coin. Because of the large wheel, the wing has a large angle of attack and requires that the stick be pushed forward to prevent premature liftoff (as in the Piper J-3 or Jodel 112).
Once you are in the air, the tow couldn't be more classic for the two machines. Of course the AV-36, being much lighter, will porpoise a little in turbulence but that's all. Casting off is quite normal and since we dropped the tow in a rapid ascent we begin to circle. There too the behavior of the two machines is very similar. They are very normal in climbs and descents and directional control with just a little adverse yaw in the Fauvel 22 but not too much. As with all the gliders of this period, coordinated rudder pressure in the direction of the turn is necessary and sometimes it is necessary to aid the turn with a little opposite stick to avoid overbanking. It can be said, for those who knew this period, that the Fauvel 22 flies like a C-800 and the 36 flies like an "Emouchet". On the other hand, the glide ratio of the flying wings is 3 to 5 times greater than these machines. For the two-place it is reasonable to expect an L/D of 23 and 20 for the single-place. Of course all that happens at low airspeeds (about 80 km/h) as compared to modern gliders.
What is it like to be in a flying wing? Actually, it is a glider just like all the others, with all the strong points and shortcomings of the machines of that period. Yes, but the flying wing? Well, in the single-place it is easy to turn around and see ... nothing in back except for the two fins that have a charm all their own. In the two-place it is different: from the front seat the thickness of the wing prevents you from seeing the absence of a fuselage and you would think you were in a good old Bijave. The back seat is much more fun. First of all, you can easily see the plane's trailing edge and therefore the lack of a fuselage but what is more, for reasons of space, Fauvel installed a rudder bar that moves vertically like organ pedals. The first turns are surprising but you get used to them quickly and soon forget about this peculiarity. On the other hand you gain extraordinary visibility, except for the instrument panel which is characteristic of two-place machines and is naturally located in front. With a little experience, you can manage to look at the instruments by coordinating your head movements with those of your companion or student. This is made easier by the fact that the back seat is about 30 cm higher than the front.
What else can I tell you about how this machine flies? It spirals well, climbs well, it has relatively high L/D but if the flight is not coordinated you know it right away; low frequency vibrations appear and are amplified sonically by the extension of the tail fin of the AV-22 that acts as a large sound board. And since we are talking about details, it should be remembered that the vibrations are greatest at the wing's trailing edge in a turbulent zone, especially at low airspeed and therefore at high angles of attack. That explains the longitudinal shaking of the stick. Some people have managed to reduce them, especially in the single-place, by improving the air flow around the canopy, but to my knowledge, nobody has ever been able to eliminate them. In practical terms, on the inside it is still a glider like all the others of its time. It is outside that it is more surprising.
One beautiful afternoon in July two years ago, I was circling peacefully over Angers in the two-place with a friend. In our ascent we passed a plastic glider from another club that must have been making a cross-country flight. The pilot must have thought he was having hallucinations. It was a young man who didn't imagine that such an odd looking orange and white thing without a tail could be in the air beside him. He flew close formation with us and his amazement was visible on his face. There were no little green men in this machine but two laughing glider pilots who were waving at him. He headed for home twice then came back to be sure that he hadn't made a mistake about what he had seen. Yes, ...well, it... how can I explain it, this thing that was flying beside him, I'm not sure that he would be brave enough to tell his chief pilot what he had seen for fear of being locked up. Well, yes, my friend, the Fauvel AV-22 exists. There are still three in the world, one in Angers, one in Pont-Saint-Vincent and one in England, bought in Poitiers by an English enthusiast several years ago (You said "maintain the French heritage"? No, well, I thought you had!). There must be five or six AV-36 in France today. Generally speaking, the Fauvels aren't numerous and are all the more admired as their peculiar silhouette becomes more rare.
But enough philosophy. We are flying and have to find out what these little beasts can do. For exploring their handling nothing is better than a good lazy-8 (3). There the behavior of the two machines is identical. Taking on a little speed, about 120 km/h, and it starts, putting the nose in the sky and starting the turn simultaneously. A lot of rudder pressure is needed but it is very normal and you have a comatose airspeed indicator with a very nose-high attitude, then the nose drops and the maneuver is started over at high speed very gently on the other side. With airspeeds from 50 to 180 km/h it's real treat and some angles at the top pass the vertical to become a little inverted. It is marvelous and you have to think that Charles Fauvel made the gliders just for that reason. It must be said also that he provided a broad safety margin. (4)
At the other end of the scale let's see how the machines do at low airspeeds. The procedures and the results are the same for both machines. As soon as the airspeed diminishes, the shaking of the stick appears and grows stronger, then with the stick pulled back, we arrive at a sort of parachute-like descent with small repeating downward movements of the nose. If you really want to stall the machine, you have to gain some airspeed and raise the nose abruptly. Then it will stall but it will come out of it right away.
All of these maneuvers have shown us that the machine is very safe in spite of its strange appearance. They also caused us to lose quite a lot of altitude and it's time to think about landing. In the landing we find the same characteristics that we found on takeoff and for both machines you have to remember the lack of effectiveness of pitch control at low airspeed. The airspeed must be increased on final, especially with a forward center of gravity. On the other hand, distinct differences appear on final and at the flare. The spoilers of the single-place, which are on the underside of the wing, aren't very effective and act more like a high lift airfoil with flaps. As they are extended they initially cause a slight lifting and the nose rises, airspeed reduces and there is no more pitch control. Frame no. 2 of the fuselage needs to be changed. It is a well known fault of these machines. On the other hand, if you planned correctly and extended the spoilers at a reasonable altitude while keeping your airspeed under control, final is easy and the flare is accomplished with the stick in your stomach and a delicate crunching of the skid on the grass. In the two-place, the spoilers, which extend from the bottom and top of the wing, induce such a nose-up movement that Fauvel had to add an automatic trim to the elevator that was coupled to them in order to counteract their effect. In practice, the maneuver is not totally neutralized and you have to remember to push firmly on the stick when you actuate the spoilers. There too a drop in airspeed on final can have devastating effects. On the other hand, if the approach is good the flare is easy but you have to aware of the difference in visualizing it depending on whether you are in the front or back seat (remember, you are 30 cm higher in back). You also have to take into account the height of the wheel. After landing everything is normal for a glider but you have to hold the tail up with the stick to avoid having it drop at relatively high speed and causing the glider to lift off again. Slips are easy in these two machines and especially spectacular in the two-place. Spoilers plus a slip produces an impressive rate of descent that will finish a demonstration at a rally in an elegant manner and makes the touch-down more precise.
There, it's done. We are on the ground and all that is left is to pull the machine on the runway for a new departure. We have just flown the two most spectacular French gliders and also the most disparaged, especially by those who have never flown in them. As for the others, those who know them, they ask for more. What conclusion can be drawn from this? Their silhouette is surprising and leaves no one indifferent. They perform more than honorably for machines of that time and when all is said and done they handle very normally. The only thing is that it is important to check the C.G. Since there is no tail the range available for the C.G. is very small and it is imperative that it be checked. There is a real danger in getting out of the C.G. range. Finally, in the two-place if you forget to extend the wheel on final, as the manual for the glider says, on an unprepared surface it is preferable to land on the skid. This has happened to very experienced people (5) and it takes two people on the tail to get the wheel out. There are always a lot more people available for the libation that follows.
(1) The B.O. is a small two-wheeled carriage that is used to move gliders. The origin of this term is generally associated with the Bourget-Opera tram that pilots used before the war.
(2) Instead of having a single tow cable, the cable between the glider and the tow plane is divided into two parts, connected to two tow hooks under the wings.
(3) For the layman, it is a maneuver that ressembles an eight made on the interior of a bowl and that provides testing the coordination of controls at all ranges of airspeed.
(4) The AV-36 was stressed to more than 10 G.
(5) This happened several years ago to two well-known afficionados of old aircraft who had between them a total of 35,000 hours of flight time, 3,000 of which was in gliders!
Jack Lambie flew one of the first AV-36 in California during many years.
In the fall of 1960, I bought Fred Jukich's Fauvel AV-36 flying wing sailplane with some of the money I received for a TV commercial I had made that spring. The following day it was entered in the Elsinore soaring contest and I made my first flight around an 89-mile triangle placing third.
As a result of more than 2000 miles of cross-country soaring plus many other flying hours during the years I owned the ship, I can make the following conclusions about its handling and performance : in the air its pitch stability was outstanding; the trim tab was simply set for what-ever angle of attack you desired and that's all you had to worry about. Circling or straight ahead, the speed stayed constant with no movement of the stick. In fact you could let go of the stick to stabilize the speed in a turbulent turn. In a straight glide I could lean forward to speed up and lean back to slow down without moving the stick.
The roll was very good, although I discovered, after a few dozen hours, that full deflection of the rudders greatly increased the rate of banking. It could perform wingovers, loops, inverted stalls, and full-stall, reversed-control, half-turn spins effortlessly and safely. Several times I pulled back on the stick and went straight up, in an attempt to do a "tailless" tail-slide. The nose snapped down at the top each time and the ship would fall in a brick-like level attitude for a second and then recover normally. I never could get it to slide backwards.
Never any problems in the air. Well, once, when doing full rudder deflection wingovers the wood block that holds the bell-cranks to move them popped off. By using just the ailerons I landed with no problem.
The steel dolly was a car leaf spring with wheels. It was usually set just ahead of the C.G. in order to get started, and it was to slid off before flying speed. More about that :
Because the tow attachment was a loop going behind the c.g., the wing man had to be sure to keep things going straight until reaching control speed. But one ground loop on takeoff occurred on an aero tow start at Torrey Pines due to the wing man letting go too soon. Winch tows were easy and always successful.
Another time, at Elsinore, CA, the dolly was placed too far forward and the glider had a lot of speed before it was lifted. The dolly flipped and tumbled, bouncing up into the elevator at the back of the wing, breaking it in two. On the fast aero tow I didn't notice anything because the elevator is held down. After release and I slowed the stick kept moving fore and aft on its own and the ship shuddered rhythmically. I looked back out the rear window I had installed, and saw wood and fabric trailing and flapping.
What to do? This was the first time I had ever flown the little flying wing without my parachute. I didn't wear it this flight because I wanted to move the balance back a little to see if it reduced the sink. It did, but that's another story. There was no choice except land. I flew very slowly and brought the shaking glider down to a nice slide and stop in the middle of the field. Whew! I scarfed and glued the elevator spar together and had it flying the following weekend.
Landing was no problem unless the wing tip hit something-such as a blade of grass, a flower, or a butterfly... I had three of the most twirling, high-flying ground loops ever experienced on cross-country landings. It invariably broke off the sub-rudders and scratched and messed up other corners of the ship. Once started, it was split-second fast and totally uncontrollable. I put small wheels at the bottom of the sub-rudders to keep the tips off the ground, but the only real technique was to land straight ahead and pray nothing touched a wing tip until the ship was almost stopped.
The skid was good in that it stopped the ship so fast that it made the dangerous part of the flight quickly over, but I think it may have contributed to the ground-loop problem because the deceleration shifted the weight up on the nose of the skid, making for unstable directional control. If the glider were landed at any speed over stall, there was a tendency for it to leap back into the air again when the skid touched and bounced the nose into a lifting position. I never had any problem with this, as I usually make full-stall, one-point landings, but I heard Fred Jukich and others had difficulty with this 'bobbling" characteristic.
The obvious comparison to the Fauvel is the Schweizer 1-26. Each has a 40-foot span and is designed to fill the same performance range. The Fauvel could easily beat the 1-26 at any speed over 55 mph and it was so stable and easy to fly in the air that it made a 1-26 feel like flying a unicycle. At slow speed the 1-26 is better because the tail easily holds the wing into a high-lift position, whereas the flying wing elevator is along the center section of the trailing edge of the wing, thus greatly reducing the lift. At slow speed, pulling back the stick actually pushed the plane down.
Looking back I would say the nice handling and good speed performance of the wing was its biggest asset. I would build a wing with a wheel aft of the e.g. for ground handling ease, a single large fin in the center to eliminate yaw, and a method of sliding the seat back and forth for optimum speed control with less elevator deflection. I would also have it able to be disassembled, instead of being one piece (as in the original). Storage convenience would easily make up for a few extra minutes of assembly at the field. I was always fascinated by flying wings and to actually own and soar the Fauvel for many years was a delightful experience. I flew it in several air shows and made lots of low altitude tight loops to the amazement of the spectators.
Pierre Plane gives us his impressions of his first flights in the AV-36.
No, I wasn't looking forward to flying this machine but was rather reticent. This flying plank, not very attractive in flight, inspired only marginal confidence in me. Then someone said "Watch out for porpoising on takeoff, you have to land with the nose up or you will wind up on your back, balance is delicate..." In short, nothing to get enthusiastic about.
Then at Keilheuvel, at the 18th gathering of old gliders, I saw the AV-36 brought from Pont-St. Vincent by Dominique Haguenauer and Christian Mathieu. The yellow wings, the orange stabilizers and embryonic fuselage, and the long narrow canopy made it look like a large scale model. On the inside: the varnished wood instrument panel, old Navy style brass instrument frames, a rosewood seat, a real jewel of workmanship. Walking around it in the course of having several drinks under the pine trees (light beer 1.5%), J.P. Robin, who has one the gliders in Gap, let himself go in a veritable mental intoxication of enthousiasm: "This thing flies itself, in the tow I let go of the stick... when it is pulled back the wing gets into an undulating mode of flight... it climbs better than anything..." etc. Dominique and Christian Ravel, a little calmer, told me it was easy.
I was obliged to give it a try. The results are there: the first flight of 57 minutes, the second for 2 hours, 45 minutes. I was seduced by the AV-36. Yes, it's true. You can't be large and get into it. Yes, I had to put a little 0.5 kg weight in back of the skid. Yes, on takeoff, in the cloud of dust behind the tow plane, I "porpoised" but that ceased as soon as I let the machine have its way. Yes, the cable hooked onto the wing, and here and there on the fuselage, isn't troublesome and helps in steering. Once you are cut loose it flies all by itself and it takes an effort to convince yourself that that there is no empennage back there. You would think you were flying a modern plastic glider . On downwind at 300 meters, I were rather be long rather than too short, the airbrakes, that aren't very effective and create high lift, shouldn't be retracted more than 2 meters over the ground, it lands itself, a little nose up, 3 points, almost like a standard plane, as long as you don't touch down on the tail skid first.
Interested, I went back to try it the next day. There is little cross wind, the thermals are turbulent. There the machine feels very light. It's like a little impetuous horse that doesn't want to turn left (the obligatory turning direction) when you ask it to; you have to insist on it. Coming back into the thermal is signaled by a big kick in the rear; if your flight is not coordinated you hear a mix of whistles and vibrating groans. It really seems like a small animal that you have to talk to to get calmed down and I surprise myself by doing it: "Good, calm down now, not so fast, 80 is too much; good, would you like to turn left now? That's where it's rising..." In fact, it climbs very well. Again a rough pass, 2 to 3 m/s. You feel like you are sitting in an arm chair, because you are very comfortable, and suddenly the chair is pulled up tossing you out of it. Flying in a straight line, as J.P. Robin said, I let go of the controls and, actually controlling it with the trim, the wing flies all by itself in a sort of slow undulating motion: at 80, slightly nose down, at 70 slightly nose high and so on. I didn't try to get it to accelerate by leaning my head forward and to slow down by leaning back but it seems it would work. They were 2 hours and 45 minutes of fun but just the same I am a little tired: the flight, the congestion of the other gliders around. I land.
Thanks to Dominique for having loaned me this machine. I'm definitely going to the next gathering of flying wings in Pont-St-Vincent with Christian Ravel's AV-36. The AV-36 flying wing? It's a jewel to be discovered.
The Choucas is a two-place motorglider designed by Claude Noin and inspired by the AV-22. Philippe Tisserand, editor-in-chief of the review "Vol Moteur", had the opportunity to test this machine.
Let me say right away that I enjoyed myself for two days. Four hours of flying, more than half of which was without power, re-immersed me in gliding in spite of unfavorable weather conditions. I made my first acquaintance with the machine in the company of Charly Baum who was then still an associate of Claude for the manufacture and sale of the Choucas. Charly is fanatic about flying. A highly experienced sky diver, he sat up a transport company and a maintenance shop specializing in the parachuting at Gap-Tallard airport.
Starting the motor doesn't require any special skill. Boost pump on to assist the original Mikuni and to pull the fuel from the structural tank beneath the seats, 1 cm of throttle, mixture, and hit the starter. The motor starts right away and you let it warm up while leaning the mixture in small increments as soon as the motor begins to run smoothly. In the Choucas the idea is not to give it full throttle until the cylinders have reached 180°C. Apparently this is an effective procedure since the motor is just as strong as it was originally.
We take to the runway after a Robin and a Twin Otter while an ASK 13 is towed onto the grass strip. The harmony that reigns on this field must be mentioned. Full throttle, you push a little on the stick to get the Choucas up on its main gear and all you have to do then is wait for the lift off which comes after 10 seconds at 55 km/h indicated airspeed. It's important not to force the takeoff because in a flying wing of this type an elevator deflection is the same at first as putting on the brakes and the Choucas sets back down. You let the airspeed climb to 85 before trying to get into the climb. The vertical speed indicator shows 2 m/s which is unexpected for me considering the motor and the large mass of this prototype. While we are climbing Charly calls his friend, Jacques Noël who teaches in the ASK 13 Pierre Bouilloux. He is a guru of paragliding. We are at the foot of Cëuze mountain, in a little 0.5 m/s climb. Alas, as we approach the lift disappears and Noël recommends going towards Blailleul mountain to the Southeast.
We set up for 135 km/h and 5,400 rpm, best economy cruise, and in 10 minutes we are there. Actually, that puts us into the upslope winds. However, it is late in the day and the dominant current from the North is counteracting the upslope wind. In a half hour of doing figure 8's back and forth along the slope almost in the rocks with the motor shut off I discover the fine points of the Choucas. The ailerons are stiff but effective enough under these conditions. The rudder allows you to maintain coordination without too much control input. As for the elevator, it's better to use as little as possible, just enough to maintain the optimum airspeed of 85 km/h.
Since you can get tired of anything, Charly suggests we set down in off airport in a field five miles away at the end of the ridge. No problem. With the motor shut off the Choucas takes us there with a comfortable margin of safety. Taking off again, we let our back sides warm up a little and then pass over Digne at 1,000 meters. Then, returning towards Hongrie mountain above Vauhmeil. We climbed up to 2,600 meters using the motor. In the distance I see the ridge of Monsérieux blocking the way to Tallard. Then nothing happens. It is almost 6 o'clock and Charly wants to demonstrate for me the glide ratio of the Choucas. We cut the motor again. Without believing we could do it I aim for Tallard setting up for maximum lift at 90 km/h. In spite of the slight headwind component, little by little I see the crest pass below our angle of descent. Arriving at the south base, we are still 500 meters above the ground. The advertised L/D of 22 is not far away! After a little solo flight at dusk, I go back to the Choucas the next day for a more detailed test.
In solo flight the performance is noticeably better. Liftoff takes only 7 seconds. The rate of climb is better at 2.5 m/s at 80 km/h indicated. It takes 500 rpm less on the motor to reach full power. Unfortunately, the weather was even worse than before. I have a devil of a time finding a useable thermal. In spite of everything I finally find a fully developed cumulus which allows me to climb without the engine from 1,200 to 2,200 meters. It is easy to keep the Choucas in the thermal. The feelings I had yesterday about the plane are confirmed: you have to avoid touching the elevator. Claude explained his technique to me. All you have to do is look out to the side to see if the elevator is aligned with the wing. In this situation the drag is at minimum. Sitting back a little in the seat you can manage to hold the airspeed to 80 in a turn and all you have to do is just touch the stick to follow the thermal. If the wind and the gusts are weak the transition to unpowered flight can be made at 85 km/h when you are solo. Actually, in a flying wing the speeds for minimum rate of descent and maximum lift are very close. After coming back under my cumulus two times, I decide to go back home. To the Northwest a layer of cirrus is slowly eating up the blue of the sky and when I arrive over the field it is in their shadow and convection has been almost completely cut off. I take advantage of this to climb back up to 1,500 meters for my little tests. The roll rate at 80 km/h reaches 3.1 seconds for 90° which is very good for a motorized Ultra Light of this wing span. Longitudinal stability with hands off the stick is neutral. The Choucas will maintain a non-divergent pilot-induced oscillation with a period of 31 seconds. This is completely acceptable for this type of machine and is very common in modern gliders. It is neutral as well in a bank which is an advantage for a glider that is called upon to constantly to turn at an almost constant bank angle. The rudder assures perfect yaw control, unusual in a motorized Ultra Light. Maximum speed is impressive for a machine with such a surface and as underpowered as it is. With an rpm of 6,800, full open for maximum power, I measured 160 km/h on the GPS while the airspeed indicator showed 152. That is truly fast and there are hardly any two-place motorized Ultra Lights that can reach this speed with a simple Rotax 503.
Let's turn now to the minimum rate of descent, an important parameter for this sort of machine. At an indicated airspeed of 80 km/h, the rate of descent is measured at 1.05 m/s. That is a good value for a motorized glider but, when thermal activity is weak, you have to pay close attention to your pilotage and positioning to stay over the plain. This value could certainly drop below 1 meter if a propellor brake is used or, better yet, feathered. Actually, even at 80 km/h the prop turns slowly, about one turn in 10 seconds, and its drag noticeable disturbs the flow over the wing especially when it is approaching the horizontal. This is seen on the vertical velocity indicator which goes to a minus 1.2 m/s each time.
The stall is very interesting. Full trim bring the speed to 55 km/h indicated. At that point the stick is held back but you can still control the roll and yaw of the Choucas perfectly. It just keeps its nose up without any oscillation. The vertical velocity indicator shows 1.8 m/s, a very low value that makes it possible to land in this attitude. On the other hand, when you release the stick a strong buffeting of the elevator appears and goes away only when the Choucas reaches 80 km/h, a speed at which the rate of descent goes back up to 1 m/s. It seems that a local stall where the wing and fuselage join is responsible for the phenomenon. A turning stall presents exactly the same characteristics except that the vertical velocity indicator shows 2.5 m/s.
The approach is controlled easily by the airbrakes which have two positions. Pay attention though because extending them creates a nose up movement that has to be counteracted with the elevator. You should avoid using them lower than 20 meters above the ground. The best thing to do is to execute the approach in one or two steps depending on how much altitude you have left and, when you are sure of making it, go to the second step and then don't touch anything. Then there is nothing to do but wait for the ground to come up and make the flare which might be too high. The peculiarities of the stall and the low rate of descent with the stick back lets you make a 3 point landing without bouncing if you don't let go of the stick. I tried a flare at 1 meter but Charly, who is little wild, tried it at 10 meters and didn't break anything! Actually, as long as you don't land first on the main wheels it is difficult to mess up a landing. If unfortunately you happen to do that, the Choucas will bounce. Hold the stick back and wait. It will be surprising if it bounces a second time. The rollout, 150 meters, is rather long considering the mass of the machine. The airbrakes reduce this distance noticeably.
The Choucas motorglider concept is a success. The machine has sufficient gliding ability to take advantage of good thermal conditions, a rate of climb with the motor running that keeps you from having to spend too much time near the ground and a cruise speed high enough to fly cross-country efficiently. It needs a propellor brake to perform according to the initial specifications. The major handicaps are the price and the unusual appearance of the machine. The kit allows you to keep the former low and it should be noted that the nearest competitor is the SF-25 motorglider which is quite a bit more expensive. For the later, a flight in the Choucas will easily convince you that it performs at least as well as its contemporaries.
This text is extracted from an e-mail sent by one of the first pilots who flew the Genesis, to the sailplane designer Jim Marske, and to other members of the "Group Genesis". It shows clearly the characteristics of a sailplane fitted with a reflex airfoil, flown here in severe conditions.
After flying the Gennie (as Jim calls her) for 60 hours, I must say that I am really enyoying its gentle and very interesting flight characteristics. I find it more stable in flight than any conventional glass ship I have ever flown. The absence of a tail gives it the agility of a swallow, allowing unusual tactics for capturing thermals. With the stabilizer part of the wing and with its low inertia in pitch, the Gennie immediately responds to the varying vertcal wind currents, aligning itself with the airflow to give its pilot a more gentle, less tiring ride, than any production aircraft.
I have experienced mountain rotor as well as very strong thermal cores, which would have given pilots, of conventional gliders, violent vertical surges. In the White Mountains of New Hampshire, I unexpectedly encountered rotor that would have raised my feet off the rudder pedals and thrown any loose objects in the cockpit against the canopy, if I were flying anything other than the Gennie. Instead, the ship immediately pitched up into the down part of the rotor, reducing the negative G force as it entered, and then pitched down to relieve positive loads as it entered the up part of the rotor. Upon leaving the rotor, it immediately leveled, barely changing air speed trhoughout the encounter. The only startling part to me was the viewing angles I experienced; one moment, I was looking skyward, maybe 30 or 40 degrees up; the next moment, I was looking at the ground, at the same angle only down; and then straight ahead at the horizon. Everything stayed put in the cockpit, and my feet remained on the pedals throughout. Like I said, it's a more gentle Gennie.
While flying at New Castle, VA, I flew into the core of a thermal that had to be going up at a rate of 2 to 3 thousand feet per minute, because the ship pitched down for a split moment to align itself with the flow of the core. In that short moment in time, I thought I saw leaves and trash coming up at me. (This was later confirmed on the ground, when I found bugs plastered around the nose of the Gennie.) The sensations felt when entering and leaving a thermal are opposite to what I am accustomed to. The Gennie pitches down when entering and up when leaving, giving me new aspects to key in on when circling in thermals. After flying conventional glass ships for 30 years (2600 hours; 14 years in an H301, and 16 years in a LS4), I find the flight characteristics of the Genesis to be refreshing and challenging, in a gentle way. I am very pleased with the way it flies.