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Fournier RF4D

The Fournier RF4D Motorglider

Information and content of this article is the collaborative work of Fournier enthusiasts worldwide. Special thanks to René Fournier and his team for creating a fun and exciting aircraft. Article composed by Ray Buhr, RF4D owner, N1771, jb92563@yahoo.com

Fournier RF4D
Introducing the Fournier RF4D motorglider

The Fournier RF4 is a single-seat wood and fabric motorglider designed by René Fournier in 1966 utilizing a Volkswagen aeroconversion engine built by Rectimo in France. The RF4 is the improved aerobatic version of the RF3 model.

Approximately 155 aircraft of this type were manufactured under license by Sportavia, a company created by Alfons Pützer in Dahlem, Germany, which became part of the VFW-Fokker Group. These aircraft were designated RF4D (“D” for Deutschland).
 
Since the early 1960s, Fournier aircraft have been known under the RF name throughout all countries where recreational aviation is enjoyed. Their exemplary flying characteristics, low operating and maintenance costs, and long life cycle are universally recognized and are the basis for a well-deserved reputation. It’s perhaps the versatility of the Fournier, however, that makes it so special. Economical tourer, glider, or aerobatic mount, the RF4D does all these things and does them well.
 
Fournier aircraft have always been characterized by their high-aspect ratio wing and single-wheel undercarriage used for gliders. Hence, the name of “avions-planeurs” (airplane-glider) given by their designer. Since its creation in 1960, this new formula has been largely exploited by the competition under the name of “motorglider.” The Volkswagen engine was used by most of these motorgliders and first certified for aircraft in Europe after a demonstration, by Fournier, of the engine’s high reliability in his aircraft.

Fournier RF4D
A sleek RF4D coined by some (who have had the pleasure of flying one) as a "poor mans Spitfire.”

It wasn’t common practice to certify an aircraft with only a single ignition system, but the European airworthiness authorities were persuaded that those long elegant wings provided a suitable backup! If the engine were to fail, what does it matter? It's a glider! In the United States, the Fournier is registered as an experimental exhibition glider, and as such requires a private pilot-glider certificate with self-launch endorsement.
 
The reliability achieved can be gauged by the crossing of the North Atlantic from West Germany to California in an RF4D in 1968 and return flight in 1969 by Mira Slovak. This RF4D, with a 39-hp, 1200-cc Rectimo 4AR 1200 VW engine installed, is still the smallest aircraft to have flown across the North Atlantic. It’s now part of the Museum of Flight's collection in Seattle, Washington. Mira is currently restoring it to flying condition and plans to fly it again soon.
 
Although initially conceived as a motorized glider, this ultimate development of the line is aerobatic with delightful handling, and strong, stressed to 13g and tested to destruction at no less than 13.8g.

Fournier RF4D
The former Skyhawks aerobatic team from the United Kingdom have done amazing graceful exhibitions with RF4D’sas seen in this video.

Fournier RF4D
Other aerobatic teams have used the RF4D for exhibition flying as well.

You may ask, if this aircraft was so good, where are they all? They’re out there, but theyre rare and prized by their owners.

More than 40 years after its creation, of the 155 originally made (plus 89 earlier RF3s and 225 more RF5 two-seaters), more than half are still flying all around the world, including more than a dozen here in the United States. The trouble was, when new, they were comparatively expensive.
 
In 1968 an RF4 cost $5,500. By 1972 this had risen to $8,500 – when a brand-new, two-place, Bellanca-built Aeronca Champ sold for just $4,995. Recently, the RF4Ds have been selling in the neighborhood of $25,000. Adding to the aircraft’s low numbers, the FAA refused to issue a certificate of airworthiness, despite its acceptance throughout Europe, citing the fact that the Volkswagen engine only had single ignition. Despite the fact that the Europeans accepted that the airplane’s 20:1 glide ratio gave it equivalent safety, and there were already single-ignition motorgliders flying in the United States, the FAA was intransigent and would only grant experimental exhibition status.

Fournier RF4D
Bob Grimstead doing what he enjoys so very much with the RF4D. Inspiring and mesmerizing show guests with his graceful aerobatics.

A Disadvantage Becomes an Advantage
Today these experimentals aren’t only used as self-launched gliders, but as aerobatic machines and fuel-efficient personal transports, as well as for pure fun flying.
 
Coincidentally the RF4D also fits into the light-sport aircraft category for flights by a sport pilot, because retractable landing gear is allowed on gliders, even further enhancing its appeal. In addition, every flight of this unique aircraft is truly an exhibition of design, art, and efficiency and is duly swarmed by curious spectators wherever it goes; it's truly hard to get a preflight done without at least someone wandering up to ask some questions that rarely fail to generate a smile.
 
Currently there are about 15 RF4Ds in the United States that have been imported and registered under the experimental exhibition category. However, with permission from Fournier, there’s a homebuilt RF4D under construction currently in France utilizing the factory drawings. Hopefully this is the beginning of a trend to revive the versatile RF4D.
 
Pre-/Post-RF4D History
French aeronautical engineer René Fournier wanted an ultra-efficient, single-seat lightplane. He handbuilt his first design (the RF1) over three years in an abandoned laundry building in Cannes, the plane taking to air in 1960 powered by a 25-hp Volkswagen engine. In 1962, the French government provided financing for Pierre Robin to build two production prototypes of the developed RF2 at his factory in Dijon. This was powered by the aforementioned Rectimo 4AR 1200. Further improvement led to the RF3, which was certified in 1963. With Comte Antoine d’Assche, Fournier formed Société Alpavia at Gap-Tallard, and they built 89 production RF3s.
 
The pair felt the RF3’s handling and strength could be improved, so a complete redesign produced the RF4, stressed to an ultimate +13g/-6g. Alpavia could no longer undertake mass production, so an alliance was formed with the German company Alfons Pützer KG to incorporate Sportavia-Pützer GmbH at Dahlemer Binz and build the RF4D. One hundred and fifty-five were completed.

René Fournier and Alfred Scherer
René Fournier (right) with pilot Alfred Scherer in front of an RF4D.

To improve its soaring performance, an RF4 fuselage was later mated to the 15-meter wings of a Scheibe SF-27M sailplane to make the SFS-31 (4 plus 27) Milan, of which twelve were made. The RF4 became so popular for aerobatics that another version was produced, with a bigger, 1,700-cc engine and clipped wings. Sadly, only two of these RF7s were ever built.
 
Fournier simultaneously developed a tandem two-seat derivative, the RF5, powered by a Limbach SL 1700 VW conversion, and 126 were made.

RF5
The RF5, a two-seat folding wing, development of the RF4.
Video: http://www.youtube.com/watch?v=HTd8OWSVoPE

Later, 99 more of an improved version called the RF5B Sperber were completed, with longer wings and a slimmer aft section of the fuselage.
 
Subsequently, Fournier went on to design the RF6, which developed into the composite Slingsby T67 and military T-3A Firefly trainer, which until recently was used by the U.S. Air Force (USAF) for primary training. Over 260 of these have been sold worldwide. Fournier followed these with the four-seat RS-180 Sportsman, the all-metal tandem RF8 (also derived from the RF4), the side-by-side RF47 and RF9, and the composite development, the RF10. This went into production in Brazil as the Limbach 2000-powered Ximango (50 sold) and Rotax 912-powered Super Ximango (80 sold), which replaced the Fournier-derived T-3A Firefly as the USAF’s primary trainer. How remarkable that Fournier designs today train U.S. military pilots.

Instrumentation

Instrumentation

All the instrumentation one would need or can fit in the RF4D. After 40-plus years, someone is liable to make improvements along the way so no two look alike.

Common Modifications/Maintenance
A common engine upgrade to the 1,192-cc Rectimo engine is installing the 83-mm VW piston and cylinders, increasing displacement to 1,385 cc. Larger VW engines, up to 1,800 cc, seem practical without compromising the handling and performance qualities. The electrical system is usually upgraded to include an alternator, a battery, and a starter.

Rectimo VW aeroconversion
The simple Rectimo VW aeroconversion upgraded from 1,200cc to 1,400cc by adding 83-mm cylinder/pistons and a doghouse oil cooler, resulting in a nice clean 42-hp powerplant. Note the lack of an electrical system.

Additional common modifications include upgrading the outriggers to nylon or fiberglass for increased ridigity, and as previously mentioned, a plethora of instrument panel designs, from the basic, standard, and nonelectrical to the over-the-top load of bells and whistles.
 
Construction
The construction of the RF4D is fairly straightforward, being composed almost entirely of wood. Fournier has made his design as efficient as possible by making all parts exactly the right size and strength for what it’s designed for, thereby saving maximum weight and waste.

Fournier

Instrumentation
The retractable landing gear is light and simple, yet robust enough to support all of the plane’s gross weight.

Until recently, the RF4D had only been built at the Sportavia factory which ceased production in the late ’60s. Since then, the RFs have been exchanging owners and rebuilt and overhauled from time to time, including rebuilds from occasional crashes through hedgerows. It seems that a wood aircraft can be restored an infinite number of times and may therefore last...indefinitely.
 
As previously mentioned, a homebuilder from France has undertaken a scratch-build of the RF4D but is including the generation of automated wood and metal-cutting template CNC files so that reproduction of the parts can be expedited and simplified. Perhaps this is the precursor to a revival of the RF4D in some form for homebuilders. Only time will tell, but since the 50th anniversary celebration is this year, June 14-20, which is being celebrated in Cannes, France, perhaps there are plans underfoot to revive an aircraft that now seems more appropriate than ever.
 
But until plans or a kit is offered commercially, those interested in homebuilding an RF4D will have to consider the restoration route, as a few U.S. owners are doing, by either recovering or rebuilding.

Retractable landing gear

Fournier

One owner from Oregon has recently stripped the aircraft down to the bare wood and has recovered the fuselage with thin fiberglass cloth and epoxy to form a very moisture-resistant barrier, one of wood’s primary enemies, especially in the more humid regions of the Pacific Northwest where he’s located. His endeavor is a testament to the support he has received from the Fournier community of owners, both here in the United States and abroad.
 
The Fournier “club,” as with most type clubs, is loaded with a great bunch of folks that are enthusiastic and helpful, never hesitating to lend a hand to a fellow “Fournierteer” needing any kind of advice or assistance. The support and dedication to the design runs from the current owners back through the former owners and comprises a great body of knowledge which is freely exchanged on the Fournier Forums and websites.
 
Club Fournier International (CFI) America Fournier Forums
http://sbeaver.com/cgi-bin/fournier/cutecast.pl

Instrumentation

 

RF4D Specifications

Wingspan

36 feet, 11.25 inches

Airfoil

NACA 23012 wing tip, 23015 root section

Wing area

121.5 feet/2

Mean aerodynamic chord (MAC)

3.52 feet

Aspect ratio

11.2:1

Dihedral

4 degrees

Twist

4 degrees

Spoilers

4.07-inch span, 0.32-inch height

Empty weight

600 pounds

Gross weight

804 pounds aerobatic,
860 pounds utility

Pilot and chute

110 pounds min. – 240 pounds max.

Baggage

20 pounds max.

Max. cruise speed

112 mph

Economy cruise

100 mph

Velocity not to exceed

155 mph

Maneuvering speed (Va) 

125 mph

Stall

45 mph

g-load limits

+6, -3;
tested to 13g static without failure

Best glide ratio (lift over drag) L/D

20:1 @ 62 mph

Min. sink

4.25 feet/s (255 fpm) @ 56 mph

Climb rate

600 fpm

Service ceiling

19,700 feet

Range max. fuel

(10 U.S. gallons) 415 miles

Takeoff distance

425 feet,
885 feet over 50-foot obstacle

Landing

330 feet

Engine

39-hp Rectimo 4AR-1200,
1200-cc Type-1 VW conversion

Time between overhauls

1,500 hours

Max. continuous power

3,600 rpm @ 115 mph, 3.1 gph, 2.7 hours

Cruise fuel consumption

3200 rpm @ 105 mph, 2.4 gph, 4 hours

Max. endurance fuel consumption

2200 rpm @ 56 mph, 1.1 gph, 8 hours

Fuel

Regular 80+ octane auto gasoline

Ignition

Single, Bendix magneto

Starter

Hand prop on ground, inflight pull start handle

Gear

Glider-style retractable main belly wheel with
drum brake (Vespa scooter)
Parking brake
Steerable tailwheel
Outrigger wheels midspan

Adventures

 
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