The JS4 Rengeti

15/18m Standard Class Sailplane

The JS4 Rengeti , the most modern standard class glider, available from 2022/23.

Pilots can select the JS4 as a pure glider, or have a choice of propulsion systems :

  • The MD-TJ 42 jet sustainer system , or
  • The Solo electric sustainer/self-launch system

Standard options on the JS4 have been carefully selected, making the JS4 the best value-for-money new glider on the market – designed for all pilots… making world champions…

Optional 18m outboard wingtips transform the JS4 into a real performer, adding that extra bit performance to compete in other classes.


Wingspan18m59 ft
Wing area11.25m²121 ft²
Aspect Ratio28.828.8
Maximum Weight600 kg1323 lbs
Empty Weight291 kg644 lbs
Wingspan15m49.2 ft
Wing area10.0m²108 ft²
Aspect Ratio22.622.6
Maximum Weight525 kg1157 lbs
Empty Weight280 kg617 lbs



The JS4 Rengeti is designed to set the new performance standard with an
optimised low drag fuselage, a high wing configuration for improved climb
performance, and new wing airfoils with a 5th generation winglet design.

The JS4 has a fuselage similar to the JS3 with extremely low drag properties over a
large range of velocities and angles-of-attack. It’s a small fuselage designed with
high-tech software to provide comfort even to our well-built customers

Performance and Speed specifications

Wingspan18m59 ft
Best L/D52:152:1
Minimum sink0.58 m/s114 ft/min
Sink rate & 200 km/h1.71 m/s337 ft/min
Max wing loading53.4 kg/m²10.94 lb/ft²
Min wing loading32.0 kg/m²6.55 lb/ft²
Wingspan15m42.9 ft
Best L/D46.5:146.5:1
Minimum sink0.64 m/s126 ft/min
Sink rate & 200 km/h1.85 m/s364 ft/min
Max wing loading52.5 kg/m²10.75 lb/ft²
Min wing loading36.0 kg/m²7.37 lb/ft²

Standard Performance Features

  • Control surface gaps sealed with the Streifeneder Teflon/Mylar
  •  Cockpit airflow controlled with an air extractor
  •  Integrated bug wiper garages
  •  Integrated water ballast tanks in main wings – 160 l
  •  Expendable tail ballast tank – 5.8 l
  •  Non-expendable tail ballast tank – 8.9 l

Optional Performance Features

  • JS bug wipers operated by the On-Track programmable automatic
    winding system
  • Retractable tail wheel
  • Total energy and Pitot-static probes by Airsense fitted to the
    extremities of the tailplane




Safety is not negotiable and the JS4 is a clearly setting the standard. Flying a JS4 will give
you a safe feeling with highly desirable flight characteristics.

The forward vision in flight from the JS4 cockpit is impeccable, designed that 12 o’clock
traffic is visible, even those slightly lower than the horizon.

Flying fast in turbulent conditions? A high maximum rough air speed allows you to cruise
safely and legally on those strong days.

Should you need to deploy your airbrakes at VNE , a unique damper system limits the
extension rate, reducing the sharp stress impact on the wings and preventing your head
slamming through the canopy.

Our safety cockpit made from carbon and aramid fibre with integral crumple zones will
stay intact even with an impact of 9Gs preventing serious injuries that may arise from
that unfortunate situation.

Safety Specifications

Safety limitsSIIMP
Max speed Vne280 km/h151 kts
Max rough air speed Va208 km/h112 kts
Max aerotow speed Vt180 km/h97 kts
Max decent rate MAUW>50 m/s9843 ft/min
Cockpit crash resistance9G9G

Standard Safety Features

  • Automatically controls, including the water system
  •  Flarm™ collision-avoidance antenna in fin
  •  Warning limit switches for landing gear & airbrakes
  • Water dump sensor
  • Hydraulic disc brake activated by a dedicated brake lever on control stick
  • Powerful airbrakes, lockable in different settings
  • Dynafoam™ energy-absorbing seat cushion
  • MH AL-248 O2 cylinder holder with quick release 

Optional Safety Features

  • Dolba transponder antenna in the vertical fin
  • Flarm™ collision-avoidance antenna in front of vertical fin for maximum view
    angle and range
  • Emergency Bail-out System



Performance in comfort is accessible to pilots of all sizes:  the JS4 combines a low drag
fuselage with the amazing ability to accommodate our flying giants. 

But the JS4 is not designed just to be a contest winning racer. It has been designed to have
the ultimate feeling of the air, light on the controls and stable in thermalling. Similar to the JS1, the JS4 can even be thermalled hands-off while bank and speed is maintained.

Low time pilots instantly feel at home and are able to perform exceptionally well without much time in the cockpit.

Our pilots with less arm strength can easily operate and lock the airbrakes and landing gear even at speeds up to 200 km/h.

Comfort Specifications

Comfort FeaturesSIIMP
Max Cockpit weight115 kg254 lbs
Maximum size pilot2.03 m6ft 8"
Airbrake locking forces-15 daN-33.7 lbf
Cockpit shoulder width525 mm20.7 inch
Landing gear retracting forces-14 daN-31.5 lbf
Inner wing panel weights<65 kg143 lbs

Standard Features for your comfort

  • In-flight electrically adjustable rudder pedals
  • Ground adjustable seatback with headrest
  • Canopy side window with air scoop
  • Green tinted canopy for increased UV protection
  • Forward opening canopy for comfort
  • Cockpit side vent with ventilation control
  • Leather cockpit interior upholstery with storage pockets
  • Tool bag with assembly grease and rigging tools
  • Canopy cover, tail dolly



The standard class glider has been neglected by the manufactures for nearly 20 years, but not anymore.

Wing optimization was accomplished by incorporating a simple lifting-line code with an Xfoil add-on to accurately predict the sailplane performance polar.

Thermaling performance was calculated with different thermal models incorporated into the numerical performance model. A simple Quast weather model for initial optimization was included in order to maximize average cross-country speeds. A particle swarm optimization (PSO) algorithm was applied to change airfoil geometries and the wing planform shape in order to maximize the cross-country average speeds.

All design iterations which showed high cross-country speeds on the Quast weather model were selected and verified with another cross-country simulator using real flight data compiled from actual competition flights.

This model could then calculate the average cross-country speeds for that configuration. To our surprise, the airfoil type giving the best results was quite different to the airfoil which usually would have been chosen based on performance polar only. As a result, a new wing was designed having improved climb and high-speed performance, with mid-range speed performance slightly better than today’s standard.



The performance of the MD TJ-42 matches that of JS Products 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 retractable electrical propulsion (RES) system, developed by well-known aircraft engine producer, SOLO Aircraft Engines, with the EMRAX 188 air-cooled high-voltage electric motor, is not only a sustainer but also a limited self-launcher.

*Performance, masses and figures are estimations based on theoretical data only and may change without prior notification.

Contact Us

If you have any questions, would like a quotation or just more information about our product,
do not hesitate to contact JS Sales by completing the form below