Engine Systems

In 2013 the JET Engine developed by our European partners M&D Flugzeugbau was integrated in the JS1 as a sustainer package. For most pilots it is becoming important to have the reassurance that they will be able to land back home, especially after very long flights or a fierce competition day. The JS MD partnership boasts a modern solution for this, matching the performance of a jet engine with a high performance sailplane. This lightweight solution of only 17 kg (37.5 lbs) has no noticeable increase drag or decrease in the glide ratio, an extremely intuitive and user-friendly interface while giving great climb or straight line performance. With the turbine operational there are various operation modes of flight possible: Climbing at 2 meters per second (4 knots) at a 135 km/h (73 knots) or if you are late for an appointment, straight and level flight in excess of 200 km/h (108 knots) can be achieved. With the flick of a switch, you will become a jet pilot.
The Jet system can be installed in both the JS1 and the JS3 gliders.
Jet Engine MD-TJ42

In 2007 M&D identified the potential benefits of installing a small jet turbine sustainer in gliders but considered the range of jet turbines available for model aircraft had limitations. Such engines had not been designed from the outset to consider certification or in-flight starting. M&D decided that rather than convert a model aircraft jet turbine into a glider sustainer, it would be better to develop and certificate a new engine.

The key features of the MD-TJ42 engine are:

  • Single spool jet turbine
  • Two stage axial-centrifugal stator-less compressor with a compression ratio of 1:3.8
  • Cannular combustor with multiple fuel injectors and combustion zones contained within a single annulus casing
  • Glow-plug ignition system (used in start-up sequence only, ignites top combustion zone only)
  • Single stage axial turbine with stators
  • Convergent nozzle
  • Front-mounted, direct drive electric starter motor for initial spool up
Engine Technical Data  
Engine MD-TJ42
Maximum rotary speed 97000 RPM
Idle speed 30000 RPM
Thrust at max rotary speed 35 daN (at MSL and ISA)
Consumption at max rotary 60 kg/h
Thrust at idle speed 3 N
Consumption at idle speed 7.47 kg/h
Air consumption 0.5 m3 / s
Compression ratio 1:3.8
EGT at idle speed 500 °C
EGT at max RPM 790 °C (1472 °F)
System technical data  
Complete system weight - no fuel 17 kg

The maximum thrust is nominally 42 kgf at 100,000 rpm with an estimated fuel consumption of 66.4kg/hr at full thrust. At the idle speed of 30,000 rpm the thrust is less than 2 kgf. The weight is 3.3kg and overall dimensions 400 mm long and 150 mm diameter.

The TJ42 has a kerosene start-up (as opposed to gas start engines) which eliminates the need for separate gas canisters and long complex start-up procedures.

The engine and pylon are enclosed by cowlings manufactured from fiberglass and aluminium.

The performance of the MD TJ-42 matches that of the JS1 and JS3 perfectly. There is no increase in workload, only a single switch and throttle dial, and there is no noticeable performance loss with the jet extended.

The efficiency of the Turbo Jet increases with altitude. With a saw tooth flying profile at an altitude of 2000m (±6560ft) a range of 240 km (149 miles) can be obtained with the JS1 and 150 km (93 miles) with the JS3.

Maximum Power is achieved in less than 40 seconds from deployment of the system.

Follow link to view more performance data of the MD TJ-42:

Technical Data MD TJ-42

Saw-tooth flying profile

Thrust and fuel consumption versus RPM

Total System Side View

The JS-MD Turbo Jet System includes the retraction mechanism, fuel system, power supply and display unit (designed by LXNAV).The system is designed to minimise drag of the deployed engine and to allow easy access and good maintainability (allowing servicing and overhaul of the sailplane).

M&D was awarded Type Certification of the MDTJ-42 in December 2015 and six months after the EASA (European Aviation Safety Agency) approved the turbine, SACAA (South Africa Civil Aviation Authority) approved the amendment of the JS1 Type Certificate to include the Jet turbine. In 2017 EASA awarded Type certification to the JS-MD 1C with Jet Turbine included.

The engine and other mechanical parts are mounted within a monocoque carbon-fiber reinforced composite sustainer box. The monocoque box adds minimal weight and contributes to the overall strength of the fuselage.

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The engine bay is covered by two main doors that open and close during deployment and retraction with a third ‘finger door’ that folds away to make an opening into which the pylon fits flush with the surrounding fuselage. An electro-mechanical linear actuator is used to deploy the engine by rotating a tubular pylon structure.

The pilot controls the engine using the JDU (Jet Display Unit) which is positioned on the instrument panel according to the customer’s preference.  The throttle is controlled using the rotary control on the instrument while engine retract/extend/run is selected by a single toggle switch. The display shows engine speed, EGT, fuel quantity remaining, fuel consumption, endurance, thrust percentage, battery voltage and capacity, hours of running time. Lights on the display indicate whether the engine is fully extended (green), transition between extended or retracted, or fully retracted.

JS3 Fuel Tank Layout

Total System View

The system has two inter-connected fuel tanks giving a total capacity of 42 litres (11.1 gallons US) for the JS1 and two inter-connected fuel tanks giving a total capacity of 22 liters (5.8 gallons US) for the JS3.

The engine electrical system includes the ECU (Engine Control Unit), limit switches, engine display unit with engine master switch, engine control and throttle which are inter-connected via a wiring loom. The ECU is a digital electronic unit that controls receives inputs such as throttle setting, engine rpm and EGT (Exhaust Gas Temperature) and controls the fuel pump rate, fuel solenoids (open/closed/pulsing) and glow-plug ignition. The ECU includes a memory card that records a number of parameters such as throttle setting, engine speed and EGT, and also data points/records such as number of start-ups and error log information.

  • M&D TJ42 jet turbine generating 40daN [90 lbf] thrust at maximum speed of 97,000 rpm
  • Compatible with diesel fuel with added lubrication oil
  • Fully automated digital engine control (FADEC) system operated by a single switch and digital RPM throttle control including “Full auto start mode”
  • Single ø57 mm (2-¼ inch) colour Jet Display and control Unit (JDU) for system and throttle control, displaying RPM, EGT, fuel level & flow, and battery voltage & capacity
  • Engine and mechanical systems mounted in monocoque carbon fibre box, easily removable for maintenance
  • Fuselage mounted fuel tanks with integral fuel quantity sensors and filters
  • Engine extension and retraction using an electrical linear actuator with mechanical sequencing to close engine bay doors in the extended and retracted positions
  • 2 x 12V LiFePo 7Ah/10Ah main batteries with circuit breaker box and dual battery relay system
  • On board self-contained refueling system (battery driven) with fuel filler connector in engine bay for refueling and defueling
  • Lightweight earphones with small jack on instrument panel

Note: Staged pricing of the Jet Sustainer is available to allow the complete electromechanical and fuel system to be installed during aircraft manufacture and later installation of the jet engine.