This document describes the MDM-1 "FOX" Glider, a two-seat performance aerobatic glider manufactured by Zakład Remontów i Produkcji Sprzętu Lotniczego Edward Margański in Bielsko-Biała, Poland. The Flight Manual, Issue III, October 1996, provides comprehensive information for safe and efficient operation.

Function Description:

The MDM-1 "FOX" is designed for aerobatic flight, classified in the Aerobatic ("A") Category. It features a mid-wing layout with a conventional tail-unit arrangement. The glider is intended for training and performance aerobatics, accommodating one or two persons. Solo flying is restricted to the front seat only. The glider is equipped with a control system for elevator, ailerons, and rudder, as well as an air brake system. It includes a fixed undercarriage with main and tail wheels, and a hydraulic disc brake on the main wheel coupled with the air brake actuation.

Important Technical Specifications:

Dimensions:
- Span: 14.00 m (45.93 ft)
- Length (up to rudder top edge): 7.38 m (24.21 ft)
- Height (in flight attitude): 2.25 m (7.38 ft)
- Wing area: 12.34 m² (132.8 ft²)
- Aspect ratio: 15.88
- Root chord: 1.308 m (4.291 ft)
- Mean Standard Chord (MSC): 0.971 m (3.186 ft)
- Tailplane span: 3.160 m (10.37 ft)
- Tailplane area: 1.873 m² (20.2 ft²)
- Fin and rudder area: 1.123 m² (12.09 ft²)
Weights:
- Nominal empty weight (without balancing weights): 350 kG (772 lb)
- Nominal empty weight (with balancing weights): 361 kG (796.3 lb)
- Max. weight of structural non-lifting parts (wing-less glider): 165 kG (364 lb)
- Max. in-flight weight: 530 kG (1168 lb)
- Maximum take-off & landing weight: 530 kG (1168 lb)
- Maximum take-off & landing weight for extended load factor (+9/-6 g) in solo flight: 450 kG (992 lb)
- Maximum weight in baggage compartment: 0 kG (0 lb)
Center of Gravity (C.G.) Position:
- C.G. position (empty glider): 620-645 mm (24.43-25.41 in) aft of Datum Plane
- C.G. range (in-flight): 213-379 mm (8.40-14.93 in) aft of Datum Plane (22-39% of MSC)
Load Factors:
- Limit manoeuvring load factors: +7/-5
- Limit manoeuvring load factors for solo flying (max. useful load 100 kG): +9/-6
Airspeeds (IAS):
- VNE (Never exceed speed): 282 km/h (152 kt)
- VRA (Rough air speed): 225 km/h (122 kt)
- VA (Manoeuvring speed): 214 km/h (116 kt)
- VW (Maximum winch-launching speed): 150 km/h (81 kt)
- VT (Maximum aerotowing speed): 150 km/h (81 kt)
- Stall speed in smooth configuration: 78 km/h (42 kt) (1 person), 84 km/h (45 kt) (2 persons)
- Stall speed with air brake extended: 87 km/h (47 kt) (1 person), 94 km/h (51 kt) (2 persons)
Wing Profile: NACA 641 412
Tailplane Profiles: NACA 631 012 ÷ 63006 mod.
Fin and Rudder Profiles: NACA 632 015 ÷ 631 012
Construction: Structure of glass/epoxy and carbon/epoxy composite.

Usage Features:

Cockpit Controls: All controls are operated conventionally. The wheel brake is coupled with the air brake, operated by a lever on the cockpit left-hand side. The elevator spring trimming device is operated by a grip on the left-hand side of the control stick base (front seat only). Rudder pedals at the front seat are adjustable on the ground. The front seat backrest is adjustable.
Canopy: Two-piece, side-hinged canopy opening sidewards to the right. Emergency jettison is activated by simultaneously pulling a red lever on the right-hand side and the canopy opening lever on the left-hand side. Both pieces of canopy cannot be jettisoned by one person.
Launching: Approved for aerotow and winch-launching. Autotow-launching is PROHIBITED. For aerotow, a nylon towing cable of 40-60 m (130-195 ft) with a safety link of 677 daN (1525 lb) ± 10% strength is required. The same cable specifications apply for winch-launching.
Aerobatics: Certified for aerobatic flight. Specific aerobatic manoeuvres and recommended entry airspeeds are detailed in the manual. Aerobatics in rough air are prohibited.
High Altitude Flight: Limited to 3000 m (9840 ft) pressure altitude due to the lack of oxygen equipment. VNE must be reduced with altitude to maintain a safe margin against flutter critical speed.
Stall Characteristics: The glider provides clear stall warning with perceptible vibrations. The nose gently drops, and aileron control remains efficient until the stall. Recovery is trouble-free by releasing the stick.
Spin Characteristics: Spinning is unstable, with oscillations in pitch and rotational speed. Recovery delay does not exceed one turn. Normal recovery involves deflecting the rudder opposite to autorotation, releasing the stick forwards, neutralizing the rudder, and recovering from the dive.
Minimum Equipment: For normal (soaring) flight, an airspeed indicator (300 km/h / 160 kts), altimeter, 5-point safety harness, and parachute/back cushion (8 cm / 3 in for front seat, 2 cm / 1 in for rear seat) are required. For aerobatic flight, an accelerometer (9/-6 g) is additionally required, with two accelerometers for dual instruction.

Maintenance Features:

Rigging and De-rigging: Requires four persons with basic technical skills. All participants must be informed of the procedures. Bolts and screws should not be placed on the ground. De-rigged assemblies should be stored on a trailer. All mating surfaces, main bolts, and sleeves should be dried and re-greased. Glider rigging should be supervised by a rigger.
Daily Inspection: Includes verifying documents, external inspection, checking control system securing and operation, towing hook operation, undercarriage condition, tire pressure, pilot's safety harness, static/total pressure ports, board instruments, battery, pedals, air-vent valve, canopy, locks, jettison system, and balancing weights.
Post-Rain Flight: After flying in rain, drain water from drainage units, disconnect and blow out pressure ducts, then reconnect and perform a leak-check. The glider should be de-rigged and fittings/bolts greased the next day.
Canopy Care: When leaving the glider in the airfield on a sunny day, the canopy perspex must be protected with a cover to prevent self-ignition of cockpit elements. For cleaning, use a special polishing agent for perspex.
Cleaning: Wing leading edge and external lacquer coats should be cleaned with a soft flannel cloth or shammy.
Alterations and Repairs: Any alterations must be approved by the Airworthiness Authority and agreed with the producer.
Markings: No color inscriptions or markings are allowed on the upper surfaces of the wings, tail unit, and fuselage.
Ground Handling: The glider should not be ground towed at speeds above 6 km/h (3 kt). Towing cable length should be at least 6 m (20 ft). It can be towed "nose first" or "tail first" using designated hooks. For hand transportation, push "tail first" on the wing leading edge at the semi-span. Make turns with the tail wheel lifted using the special handle on the fuselage aft part.
Transportation in Trailer: The producer offers a COBRA-FOX closed trailer with loading instructions. If using another trailer, fix wings at spar roots and leading edge, protect mating surfaces, fix tailplane in clamps, protect fittings/inspection holes/bearings from dust/dirt, immobilize control stick/surfaces, close canopy, and protect external surfaces with covers/foil.

MDM MDM-1 FOX - General

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