HUNGARIAN GLIDERS
1933-2000
Type designation: KM-400
Name: KM-400
Designer: Mihály KESSELYÁK
Class: Experimental
General arrangement: Cantilever, shoulder wing, T tail section, no elevator, retractable wheel, mixed light-metal and glass-fibre structure
Crew: 1
First flight: June, 1983
Manufacturer: Workshop of the Airplane Service of the Hungarian Agricultural Ministry, Nyiregyháza
Number of built: 1



Short history:
The tender for aircraft design invited by the Pest Area Machine Factory (PGE) in 1965 was won by an interesting glider design, which had been submitted by Mihály KESSELYÁK. The designation of the design was KM-200, and the interesting feature was the glider's unusual pitch control. The glider had no elevator, only a fixed horizontal stabilizer on the tail unit. Pitch control was entirely done by flaps on the wings. When the pilot pushes or pulls the control stick the flaps moves upward or downward respectively. Moving the stick sideways the flaps move asymmetrically. Applying pitch and aileron control inputs simultaneously, the resulted movements accumulate. Depending on the angle of attack great momentum is resulted from the aerodynamic forces generated on the wing due to the special form of the airfoil used. The purpose of the horizontal stabilizer is to counterbalance this momentum. This method of pitch control does not changes the angle of attack when control stick input is applied, but changes the camber of the wing. The result is lesser drag and the attitude of the fuselage is not changing.
The winner design was not built by the factory. The designer had obtained a patent for the control system and later found sponsors in the Airplane Service of the Hungarian Agricultural Ministry (MÉM RSZ), the Hungarian Agricultural Ministry and the Agricultural College of Nyiregyháza. The redesigned glider got the designation of KM-400 and was built at the workshop of the MÉM RSZ located in Nyiregyháza. The glider first flew at Jun, 1983, however with a temporarily fitted elevator. At December, 1983 the glider finally flew in her originally intended configuration. The test flights were successful. However the sponsors did not supported the experiments past the tests. Today the glider is a valued item of the Permanent Aircraft Exhibition of the Museum of Transportation at Budapest.
The glider was certified for cloud flying and spins.

Structure:  Mixed light-metal and glass-fibre
   Wing:
The wing has tapered planform. On its trailing edge there are seven control surfaces on both sides. The Schemp-Hirth type airbrakes work only on the upper surface of the wing. The wing's structure is a monocoque structure similar to that of the EV.1.K Fecske, however four webs had been used at the central part of the wing, which has been covered by glued-riveted layer-structured thin light-metal plates, the number of the layers is gradually decreasing towards the wingtip. All the light-metal joints had been glued and riveted. The light metal skin has got a thin glass-fibre coat. Local stiffness has been assisted by polyurethan foam and thin balsa fills.
   Fuselage:
The fuselage's front part has circular cross section flattened a bit on the sides. Its structure consists of two light-metal longitudinal beams and longerons, and a steel rod above the head of the pilot. The fuselage behind the wings is a light-metal tube of 200 mm diameter. The front and the rear parts of the fuselage are connected by a steel-rod structure. The attachment of the half wings and the fuselage is similar that of the EV.1.K Fecske, that is the half-wings were attached to a central part integrated into the structure of the fuselage. This central part had a similar structure than that of the wing.
The large bubble canopy opens sideways and is jettisonable. The upper part of the fuselage behind the canopy to the wing's trailing edge has plexiglass cover. The landing gear consists of a retractable wheel, which turns 90 degrees on the side when retracted, and a small fixed tail-wheel. Two hooks are fitted: one in the nose for aero-tows and one at the fuselage's bottom for high winch launchings. The controls in the cabin have traditional arrangements and usage.
   Tail unit:
The tail unit has T arrangement. No elevator is connected to the horizontal stabilizer.



Larger picture


Dimensions:
   Wing:
     Span, m: 15
     Area, m2: 11,62
     Aspect ratio: 19,35
     Chord (root), m: 1,13
     Chord (tip), m: 0,4
     Airfoil (root), m: FX 67K-170 mod.
     Airfoil (mid-span), m: FX 67K-170 mod.
     Airfoil (tip), m: FX 67K-150 mod.
     Dihedral, degree: 0
     Sweep, degree: 0
     Washout: Aerodynamic
   Aileron:
     Span, m: 7,06 (combined with flaps)
     Mean chord, m: 0,208
     Total area, m2: 2,61
     Balancing: Aerodynamic
   Flap:
     Type: Combined with aileron
     Area, m2: 2,61
     Relative length, %: 0,942
   Airbrakes:
     Type: Schempp-Hirth
     Position (upside/downside): u
     Total area, m2: 0,4
     Position, % of chord: 0,6
   Horizontal stabilizer:
     Span, m: 4,0
     Area, m2: 1,6
   Elevator: None
     Trim: Yes
   Vertical stabilizer and rudder:
     Total area, m2: 1,208
     Rudder area, m2: ?
     Balancing: None
   Fuselage:
     Length, m: 6,75
     Width, m: 0,6
     Height: 0,82
     Cross section, m2: ?
   Landing gear:
     Type: Retractable
     Wheel diameter, m: 0,35
Masses:
   Wing, kg: ?
   Fuselage, kg: ?
   Tail unit, kg: ?
   Empty glider, kg: 260
   Gross, kg: 370/470
   Ballast, kg: 100
   Wing loading, kg/m2: 31,8/40,4
Speeds:
   VNE, km/h: 330
   Max. speed with open airbrakes, km/h: 330
   Max. aerotow speed, km/h: 180
   Max. winch speed, km/h: 115
   Max. speed in rough air, km/h: 190
   Stall speed, km/h: ?
Performance:
   Min. sink, m/s (at gliding speed, km/h): -0,68/79
   Best L/D (at gliding speed, km/h): 41,6/103
Start methods: Winch, Aerotow



Origin of data and 3-view drawing:
Jereb Gábor: Magyar vitorlázó repülőgépek, Műszaki Könyvkiadó, 1988, Budapest
(Gábor JEREB: Hungarian Gliders, Technical Publishing House, 1988, Budapest)

Gábor FEKECS E-mail: fekecs.gabor@t-online.hu