Hungary’s leading postwar sailplane designer is Erno Rubik, a number of whose designs in the R series went into production at Esztergom during the 1940s and 1950s. The metal and fabric R-25 Standard had its origins in the all-metal single-seater R-23 Gebics experimental sailplane which first flew in 1957 and was designed at the Alagi Kozponti Kiserleti Uzem Dunakeszi, where Erno Rubik was head of the design office. This organisation’s development of the Gebics and the services of Rubik as chief designer were taken over that year by MME / Miizseripari MCivek Esztergom, and a Standard Class derivative of the Gebics with a laminar flow wing, the R-24 Bibic, was completed in 1958. This was further developed by Rubik into the R-25 Standard single-seater, the prototype of which first flew on 29 September 1960; as its name implies, this is a Standard Class sailplane and is fully aerobatic, as well as being suitable for cloud flying. This design has a pod-and-boom all-metal monocoque fuselage and a ‘butterfly’-type V-tail, with an included angle of 90° between the tail surfaces. The cantilever high wings are all-metal single-spar structures with a leading edge torsion box and fabric covering aft of the spars. Slotted Frise ailerons are fitted and an unusual feature is the use of fan-type air brakes on each side of the fuselage instead of the more usual wing type. The all-moving tail surfaces are of fabric covered metal construction, with a geared tab in each trailing edge. Landing gear consists of a non-retractable monowheel with torsion rubber spring and a brake, and the pilot sits under a removable one-piece blown plastic canopy.
R-25-4 (E-31) Esztergom
Span: 49 ft 2.5 in
Length: 23 ft 11.5 in
Wing area: 120.6 sqft
Aspect ratio: 20.09
Empty weight: 408 lb
Max weight: 683 lb
Max speed: 137 mph (in smooth air)
Max aero-tow speed: 84 mph
Min sinking speed: 2.23 ft/sec at 47 mph
Best glide ratio: 31.2:1 at 51 mph
All Aero 