ROTARY HISTORY 2
This column is Copyright 1997-2001 by Edwin Krampitz, Jr., unless indicated otherwise. Please ask for permission to reproduce.
*Reprinted on http://rotarywiki.com with consent of the author.
- Part 1:The Smallest Wankel Of Them All
- Part 2: The Smallest Production Aviation Wankel
- Part 3: Biggest of Them All
- Part 4: The Citroen Connection
- Part 5: Russian Rotaries
- Part 6: The Orphan Mazdas
- Part 7: The One that Won in '91
- Part 8: Chinese Experiments
ROTARY HISTORY 2: THE SMALLEST PRODUCTION AVIATION WANKEL
Not only have many companies and individuals converted Mazda rotaries for aviation use, but a few companies have offered their own. One of the first, surprisingly enough, was from Fichtel & Sachs (F&S) of Schweinfurt, Germany--a company known for small engines for industry and recreation. Though its engine was small, it was capable of providing auxiliary power for a sailplane.
In 1960, F&S became the second NSU/Wankel licensee and was selling production rotaries as early as 1965. It sold a variety of engines under different designations, and I'll cover them more fully another time. But F&S often used the same basic engine "head" in a variety of applications by simply using different external configurations. The complete sailplane engine, designated K 8 B, was one example.
The K 8 B was a F&S KM 48 engine modified with a shroud, a propeller, and a simple cylindrical pylon for mounting. The KM 48 was one of the first rotaries F&S offered in 1965, originally designed for stationary industrial uses. Its rotor radius (-prime) x eccentricity x width (R' x e x B) were 71.5 x 10.75 x 40 mm, giving a displacement of 160 cc (9.8 ci). In its original form it produced 8 hp at 4800 rpm and weighed 17 kg (37-1/2 lb) less fuel tank, but in the K 8 B application it was more powerful: 10 hp at 5000 rpm with a weight complete of 19 kg (42 lb). It's evident that this design was quite conservative: the engine redline was only 5000 rpm. The 900 mm (35-1/2") standard prop was made by Hoffman.
A picture of a prototype K 8 B appeared in a 1968 Society of Automotive Engineers (SAE) report; it flew on a single-seat Schleicher training sailplane. By the early 1970s, production units were apparently available, and during these years it was listed in the engine section of Jane's All the World's Aircraft. According to F&S's 1972 German specification sheet, it used a 50:1 gas-oil mixture, and its expected fuel consumption was in the range of 2.5 liters/hour, allowing about 2 hours of flight on one 5-liter tankful. Top speed in level flight was about 100 km/hr (60 mph).
Despite announcing a new 40 hp aircraft engine prototype in 1974, F&S generally stopped producing its rotary engines including the KM 48/K 8 B in 1975-1976--obviously because of the bad publicity the Wankel got after the 1973 oil crunch. How many of the K 8 B were sold and whether any made it to the US is anyone's guess. According to correspondence I received from F&S in 1996, production figures and other data are no longer available. As you might guess, neither are parts. We'll see in another segment of this column, though, that one of F&S's other rotaries took on a life of its own.