Scheibe Falke

The Scheibe SF 25 Hawk is a two-seat, made ​​of mixed fiber motor glider, which was developed in 1963 and manufactured by the disk -Flugzeugbau GmbH. He developed into one of the most built motor sailors in the world. Main features for this success were the " side-by- side" seating arrangement which facilitated the training, the simple and sturdy composite construction and the extremely good-natured flight behavior. The pattern is very prevalent, so many German motor glider pilots began their training on a falcon. Also at the Falcon family counts the SF 28 " Tandem Falke " in which the seating arrangement in favor of better aerodynamics was changed. The pilots are now sitting behind each other, which allows for a slimmer body and thus better flight performance.

• 3.2.1 Specifications

• 3.3.1 Specifications
• 3.3.2 engine variants ( currently in production only Rotax; factory specifications 2010 for 690 kg)

History

The hawk was designed from the outset as easy to fly and to-maintain aircraft, a low-cost alternative in the training and for the winter flight operations to offer in the gliding clubs. The Mixed construction method used was therefore ideal, as most clubs of that time were familiar with it by DIY and maintenance of the existing own glider parks and also had the necessary tools available. In the development of the Hawk Egon disc could on experience with motorized variants of its Mü 13 and the single-seater motor glider SF fall back 24 "Motor Spatz". The first flight of the A - hawks was 1963. Nevertheless, the interpretation as a shoulder Decker could not quite convince as the agility and maneuverability in the air to be desired on the ground were left. In addition, the A- Falke required an additional person as a helper to the wing to halt at startup. Many A- hawks were therefore modified the chassis to allow a start without assistance. With the SF 25 B these deficiencies have been rectified. From 1967, the B- Hawk was developed as a low-wing aircraft and was awarded in 1968, the type certification of the Civil Aviation Authority. How well Egon disc had understood the wishes of the glider and motor glider pilots is the fact that the B- Hawks already 373 copies were built. After using the SF 25 B a convincing concept was found essentially followed improvements such as a simplified entry and powerful engine at SF 25 C. Other practical features such as a folding wing mechanism for space saving sub- sites or the use of performance-enhancing variable-pitch propeller, were realized. The genius of the design is confirmed by a still ongoing production. With the available today stronger and more reliable engines is from the hawks also a popular and economical towing aircraft become that meets still the basic idea of ​​simple, inexpensive flying. A special document the performance and robustness of the Hawk provided the journalist Wolf Heckmann, who flew with the SF 25 C D - KOEO in around 230 hours flight from Germany to Australia.

Construction

In the construction of the Hawk Egon disc pursued a pragmatic approach; as few parts so you should be redesigned. Therefore, the wings of the Bergfalke II were also unchanged as the horizontal tail of the hawk. The elevator is still used as it is currently produced at SF 25 C. The hull consists of a horse-drawn steel tube frame, while the wings are made of plywood construction and is also covered. The chassis was originally realized by a central main wheel with drum brake. With the SF 25 B small supporting wheels under the wings and a steerable tail wheel were added, the improved maneuverability on the ground decisively. Later, the C- Hawk was also available with a bipod or tricycle landing gear. The entry requires some sportsmanship, because first the high side wall must be exceeded. The plastic cover opens forward, and is then held by a belt in place. Since 2005, initially optional, now standard, a new hood design in which the no longer divided hood is raised to open the front and then swing back. The Hawks have brakes on the wing surface, which are only moderately effective. Due to the large fuselage cross-section but also steep approaches by sideslip are possible. The drum brake of the main landing gear is actuated by pulling the airbrake lever until it stops.

Variants

SF 25 A

The SF 25 A was designed as a high-wing monoplane. The chassis consists of a main gear and a tail wheel at the rear, on the wingtips received the "A hawk" grinding bracket, the holder also some sided with small wheels. By design, the SF 25 A is inherently stable and therefore difficult to draw. In particular, the strong V- position of the wings ensures extreme lateral stability; However, this problem was solved. Originally Posted by Louis Castel:

" A horrific plane that is bringing with extreme effort and coaxing by a curve. This Stahlrohr-/Sperrholzkiste is inherently stable, that she just wants to fly straight, and then does foolproof! "

The handling of the then often built four-cylinder two-stroke boxer engine " Hirth F10", originally designed to operate on snowmobiles, put a high level of technical knowledge ahead because it required a significantly different way of dealing compared to four-stroke engines used in general aviation. The event handler called for by a manual recoil starter in the cramped cabin a certain sportiness of the pilot. Was in flight mode the gasoline -air mixture set too lean, this inevitably led to blown piston crowns and zerschmolzenen spark plugs, what the engine unjustly earned the reputation of unreliability in conjunction with the unusual start operation within minutes. The noise was quite disturbing even after that time scales: volume and frequency applied to the A - hawks known as the " lawn mower " one. As an alternative, the Hercules W2000 Wankel engine from the motorcycle and later the Rotax 447 were used.

During flight operations hence the soaring performance of the Hawk were at the forefront. Although the A- Falke not one of the most versatile aircraft and the cranks in thermals is thus probably been exhausting haul flights of 300 km and pure gliding times of over 5 hours were occupied. These are the weighing about 75 kg lower curb weight and good low speed characteristics of the A - hawks favored compared to the later versions, which allow a better utilization of even weaker updrafts.

Although the A - version of the Hawk was far from perfect, 56 copies of the A- hawks have already been manufactured.

Specifications

SF 25 B

The SF 25 B "B Falcon " has been revised over the A version in basic details: also made a major overhaul of the chassis next to the modified wing design. Thus, the B- Hawk has won both the central main wheel with drum brake now little support wheels under the wings and a steerable tail wheel to improve the maneuverability on the ground. The change to the VW -based Stamo engines provided the necessary reliability for safe continuous operation. This development was completed towards the touring motor glider, during the A Hawk had rather the character of a self-launching sailplane. Thus, the falcon had become interesting as a cost- school machine away from the glider operation. In the UK, a total of 76 B- hawks were built in different variants at Slingsby Aviation as T 61 with different engines under license. For the junior training the British Air Cadets came in 45 copies of the versions T 61E and F T Mk2 venture of Rollason RS MK2 engine ( 1.6 liter, 48 hp). Similarly, some B- hawks were built by the company Sportavia Pützer ( Dahlem Binz ) and Aeronautica Umbra (Italy ) under license. In the early B- hawks, the engine was still, started using the hand recoil from the cockpit as the A- hawks. Later electric starters were used, which could also be retrofitted. The installation of the starter and the necessary lead-acid batteries, however, reduced the possible additional load significantly. The now obsolete Stamo engine was in many B- hawks replaced by a 54 hp payable Sauer -1800 engine, which also improved the flight performance.

Specifications

SF 25 C

The SF 25 C "C- Hawk " is the most common variant of the falcon family and is still being built today. The original C- Hawk has the 60 hp payable Limbach -SL -1700 -EA - engine and was also produced by Sportavia Pützer on the Dahlem Binz under license. The later SF 25 C 2000 received the 80 PS payable Limbach L 2000 EA. Mid -1970s, the hull shape has been slightly changed to today's "bump cap " at the same time the previously centrally mounted on a rocker sticks were replaced by parallel run and the aileron mass balance. A first optional deep hood cutout facilitated the entry and is currently under construction at the opening to the rear cover as standard. Currently available is the engine with the Rotax 912S or 912A, the 59 kW ( 80 hp ) and 73 kW ( 100 hp ) is guaranteed. Since the beginning of 2009, the 85 kW ( 115 hp) Rotax 914F payable in the SF 25C is offered along with an increased to 690 kg take-off mass. With the Rotax engines of its hawk has sufficient power reserves for the cost of towing gliders, with the Rotax 914F are up to 800 kg trailer load permitted.

Regardless of the disc company Loravia offered in France at the end of the 1990s, the modification of SF 25C and D as a glider tug at, equipped with the 64 kW ( 87 PS) payable Limbach L- 2400. This version was approved in France in 1997 and called SFL 25R.

The design is essentially similar to the previous type SF 25 B. The chassis is available in three variants:

• Central wheel version (central nose wheel, tail wheel and castor wheels under the wings, can also be equipped with CG hook for winch launch )
• 2- leg version ( two main landing gear forward of the center of gravity tailwheel ( no training wheels ). )
• 3- leg version ( two main landing gears behind the center of gravity and a nose wheel. )

The flight manual for the SF 25 C indicates a narrowest pitch diameter of 15 m at the 2- leg version and from 5 m at the Bugradversion.

Specifications

Engine variants ( currently in production only Rotax; factory specifications 2010 for 690 kg)

SF 25 D

After the new, more powerful engine had proven itself in the C- Hawks came with pilots of the significantly less powerful B- falcons the desire to, the more powerful 1700 cc Limbach engine (L 1700 E0) with 44 kW (60 hp) also can use them. The company, therefore, a retooling disc was developed. To accommodate the heavier engine, the hull had to be structurally reinforced. The wings were in turn reduced to a span of 14.68 m order not to exceed the maximum take-off weight of 590 kg. Due to the necessary changes to cell structure and these conversions were only done in the factory; so upgraded falcons were then referred to as SF 25 D or short "D- hawk".

SF 25 E

The SF 25 E " Super Hawk " is an 18 m wingspan and has a 64 hp payable Limbach engine. The increased span and the use of a three-position propeller (start, cruise and feathering ) increased the glide ratio of 22 to 28, to space-saving slope Aryans, the outer wings can be folded onto the inner wing in many instances, the separation point with single-lever was similar to the RF -5B " hawk " is executed.

SF 25 K

This variant has a 49 -horsepower engine and Spornradlenkung.

The special feature was the folding wings, which took up much less space in the Hall slope Aryans.