Neukom Elfe

M.Hardy. Gliders & Sailplanes of the world

Neukom Standard EIfe S-3

  Just after World War 2 Albert Neukom of Switzerland began the creation of a line of sailplanes bearing the name EIfe; the first of these, the EIfe 1, had a wing span of only 9m (29ft 6 1/4 in), later increased to 11m (36ft 1in), and it was followed by the EIfe 2, designed by DrW. Pfenninger, with a span of 50ft 6 1/4 in and camber-changing flaps. Later came the EIfe PM3 of 1951 and this was succeeded by the EIfe M with laminar flow wings. The prototype Standard EIfe S-1 first flew on 1 May 1964 and had a V-tail; as its name implies, it was a Standard Class high performance single-seater, and was followed by the Standard EIfe S-2, which differed in having a conventional tail unit with the tailplane at the base of the fin. The production version was the Standard EIfe S-3, first flown in May 1966, with the tailplane mounted part-way up the fin and a total of 18 Standard Elfes were flying by April 1970, the year in which the developed S-4A EIfe 15 first flew. Flown by the Swiss plot Markus Ritzi, a Standard EIfe took 2nd place in its class at the 1965 World Gliding Championships held at South Cerney, and at the 1968 World Championships at Leszno in Poland a Standard EIfe S-3 flown by Andrew Smith of the USA came 1st out of 57 entries, with other Elfes placed 4th and 6th. The EIfe S-3 has a high cantilever wing built in three parts, and of plywood-balsa sandwich construction; it is fitted with trailing edge air brakes. The fuselage and tail unit are of glassfibre and plywood sandwich construction, while the landing gear consists of a retractable rubber-sprung monowheel with brake. The pilot sits upright under a removable transparent canopy.

Data: Standard EIfe S-3
Span: 49 ft 2 1/2 in
Length: 23 ft 11 1/2 in
Height: 4 ft 11 in
Wing area: 128.1 sqft
Aspect ratio: 19.0
Empty weight: 459 lb
Max weight: 705 lb
Max speed: 150 mph (in smooth air)
Min sinking speed: 2.07 ft/sec at 47 mph
Best glide ratio: 37.5:1 at 59 mph

Neukom S-4A EIfe 15 and 17

  A developed version of the Standard EIfe S-3, the S-4A EIfe 15 differs from it principally in having a new two-piece wing of the same 15m span, strengthened and fitted with Schempp-Hirth air brakes; the single spar is of aluminium alloy and the wing skin of plywood/foam sandwich. A roomier forward fuselage of improved aerodynamic shape is featured, with the slight step forward of the canopy on the Standard EIfe S-3 completely eliminated. The fuselage and tail unit are of glassfibre and plywood/foam sandwich construction, and the landing gear consists of a retractable rubber-sprung monowheel with brake. The prototype EIfe 15 made its first flight in 1970 and 10 had been built by early 1973; production continues, although at a rather slow rate. Both the EIfe 15 and EIfe 17 are available in kit form for amateur construction, the latter being a 17m span Open Class version of the S-4A EIfe 15, with the same fuselage but with a wider span two-piece wing, with provision for a tank in each leading edge to house a total of 132lb of water ballast. The EIfe 17 also has a braking parachute fitted, and a total of 10 of this version had been built by the spring of 1973, with production continuing at a relatively slow rate.
  The EIfe M17 is a single-seat motor glider version of the Open Class EIfe 17 and first flew in prototype form in mid-March 1978. It is powered by a 45hp Parodi HP 45 four-cylinder four-stroke engine driving a Hoffmann two-bladed propeller; this is pylon-mounted aft of the cockpit and retracts into the fuselage when not in use. Electric starting is provided and the fuel tank capacity is 10 Imp gallons (45 litres). Apart from the engine and its related modifications the EIfe M 17 is the same as the unpowered EIfe 17.

Data: EIfe 17
Span: 55 ft 9 1/4 in
Length: 23 ft 3 1/2 in
Height: 4 ft 11 in
Wing area: 142.1 sqft
Aspect ratio: 21.8
Empty weight: 562 lb
Max weight: 837 lb
Max speed: 130 mph
Max aero-tow speed: 87 mph
Min sinking speed: 1.84 ft/sec at 46.5 mph
Best glide ratio: 39:1 at 56 mph

Neukom AN-66 Super-EIfe

  The Neukom AN-66 high performance single-seater first flew in prototype form in 1966, and was followed by two others, designated AN-66-2, which featured a modified fuselage. These versions have cantilever shoulder-mounted wings of 18m (59ft 0 1/2 in) span and of Eppler 441 aerofoil section, which are of sandwich construction with a metal spar and have plain flaps. The forward fuselage is a glassfibre sandwich structure, while the rear portion is a wooden plywood and balsa sandwich semi-monocoque, and a 'butterfly'-type V-tail is fitted. The landing gear is a rectractable monowheel and the pilot sits under a long flush-fitting transparent canopy. The AN-66C Super Elfe is a development of the AN-66-2 with the same fuselage but with an entirely new variable-geometry wing with a special aerofoil flap that can be extended to increase the wing area by about 20%; a conventional tail unit with a low-set tailplane, similar to that of the Standard Elfe S-3, replaces the AN-66-2's V-tail. Flight tests of the prototype AN-66C began at Butzweilerhof in Germany on 11 September 1973. The new wing has a longer span of 23m (75ft 5 1/2 in) and the aerofoil flaps are chain-operated by a crank in the cockpit and can either be fully extended or fully retracted, no intermediate position being possible; when fully extended or retracted the wing profile is changed so as to result in a continuous Eppler aerofoil section. A tank to contain 132lb of water ballast is situated in the leading edge of each wing centre section, the latter being 21ft 4in in length and the two outer panels 27ft 0 3/4 in each. The single-spar wings have riveted duralumin double-T spars, and plywood/balsa/plywood sandwich outer skins formed by vacuum pressing; Schempp-Hirth air brakes are fitted. Landing gear consists, as it did on the AN-66-2, of a retractable monowheel and tailskid. The wing area is increased from 172.2sq ft with the flaps in, to 206.7sq ft with flaps extended, when the aspect ratio is 27.6 compared to 33.1 with the flaps in. The AN-660 prototype, produced in 1974, has a four-piece wing of 21m (68ft 11 in) span.

Data: AN-66C Super-EIfe
Span: 75 ft 5 1/2 in
Length: 26 ft 6 3/4 in
Height: 6 ft 0 3/4 in
Wing area: 172.2 sq ft (flaps in)
Aspect ratio: 33.1 (flaps in)
Empty weight: 926 lb
Max weight: 1,433 lb
Max speed: 168 mph (in smooth air)
Min sinking speed: 1.64 ft/sec at 46.5mph (flaps out)
Best glide ratio: 48:1 at 56 mph (flaps in)

Mahrer HB-1340 Delphin

  This single-seater sailplane is an experimental variable-geometry version of the Swiss Neukom S-4A Elfe 15, and was first flown by Herr Fritz Mahrer on 6 May 1977. It is basically a modified Neukom S-4A with new 15m span wings; these have Eppler wing sections similar to those on the Neukom AN-66C Super-EIfe, and are fitted with area-increasing Fowler-type flaps actuated electrically. When extended these flaps increase the wing area from 107.6sq ft to 121.6sq ft, and the aspect ratio of 22.5 with flaps in becomes 19.9 when they are extended. The Delphin also has a T-tail unit similar to that of the Schempp-Hirth Cirrus replacing the Neukom S-4A's low-set tailplane, thus avoiding tailplane buffeting when the flaps are extended. Construction of the Delphin is mainly of plastics materials.

Span: 49 ft 2 1/2 in
Wing area: 107.6 sq ft (flaps in)
   121.6 sq ft (flaps out)
Aspect ratio: 22.5 (flaps in)
   19.9 (flaps out)
Empty weight: 617 lb