To date, the Fox is the only two-seater-glider suitable for competition aerobatics. It was designed by Edward Margański, who also developed the Swift. (The abbreviation MDM stands for the production team Margański - Dunowski - Makula).
Work on the projekt began in 1990 in parallel to the development of the Swift and first flight was on 9 July 1993. One month later, Jerzy "Jurek" Makula won his fifth World Championship on the Fox prototype in Venlo, NL.
The prototype's wings were essentially still those of the Swift. Therefore, it was limited to a max. speed of 250 km/h and to +7 and -5 g, even when flown solo. Cockpit space was quite restricted, particularly in the rear seat. So the series version had strengthened wings and the front fuselage was lengthened, resulting in a considerably more roomy cockpit.
Soon, the Fox demonstrated its enormous value for aerobatic training. Even complex unlimited figures can be trained and practised safely flying dual with an instructor. But it also became obvious that the Fox is not a glider for novices. Its stalling characteristics can be quite vicious, compared to "normal" gliders. A number of fatal accidents were the result, when over-confident pilots exceeded the limits.
A fully aerobatic glider like the Fox can be stalled at nearly any speed by abrupt control inputs. At the wing loading of the Fox, some height is needed to recover to normal flight. If someone tries it too close to the ground, the likely result is obvious...
When the Fox is flicked with full elevator deflection, the angle of attack becomes very large and recovery is only possible after several rotations. This looks quite spectacular, but the loss of altitude is considerable. Any stalled manoeuvres (flicks or spins) and stopping manoeuvres (stall turns or tailslides) must be flown in the Fox at a safe height.
For solo flights in the Fox, SAGA requires a minimum flying experience of 150 hrs on gliders and a comprehensive instruction in flying at the limits.
In competitions, the Fox has a hard time against the Swift.
The two-seater is handicapped by its inferior aerodynamics (fixed wheel) and its slower roll rate. Furthermore the "optics" of the Fox are unfavourable compared to the Swift. Seen from the side, the fuselage is inclined downwards by several degrees against the zero-lift-axis. To the judges, vertical lines up will appear too shallow and down beyond vertical. Although, according to the rules, the judges should consider this, they nevertheless use to give lower marks for the figures.
In an attempt to improve the aerodynamics, the Fox prototype was rebuilt as a single-seater in 2001/2002, the retractable wheel occupying the space of the rear seat. The gliding performance of the "Solo-Fox" is clearly superior compared to the two-seater, but the other handicaps remain. Eventually, only one example of the Solo-Fox was produced.
In 2011 Makula won his seventh World Championship on the Solo-Fox in Toruń, PL.
In 2017 the Solo-Fox was severely damaged in an accident. In the meantime it was rebuilt, using the original wings and the modified fuselage of a standard Fox.
The original Solo-Fox (2012)
Dietmar Poll tried an entirely different approach to improve the Fox:
He lengthened the fuselage and installed the retractable main wheel of a DG-500 behind the c/g. This made it necessary to install also a small nosewheel. The modification increased the empty mass by approx. 20 kg. His "Pinocchio" is certified as an experimental at a flying mass of 555 kg with largely the same limits as a standard Fox.
For cost reasons, Poll does not intend to get a full certification for his design.
"Pinocchio" and standard Fox for comparison
|wing span||14,00 m|
|wing area||12,34 m²|
|wing section||NACA 641-412|
|height (in flight attitude)||2,25 m|
|maximum empty mass||361 kg|
|maximum flying mass||530 kg|
|safe load factors||+7 / -5|
|in solo flight at a flying mass of 450 kg max.||+9 / -6|
|maximum speed VNE||282 km/h|
|manoeuvre speed VA||214 km/h|
|best glide ratio||29 at 130 km/h|
|minimum speed Vs||84 km/h|
|in solo flight at a flying mass of 450 kg max.||78 km/h|