The JS1 Revelation

18m/21m flapped sailplane

The JS1 Revelation, high-performance FAI 18/21-metre Open Class sailplane.

The JS1, designed with incorporated aspects such as aerodynamics, structures, and pilot comfort, has rapidly gained world recognition with its great performance and handling characteristics.

The JS1 is available as either a pure sailplane or with the MD-TJ 42 jet sustainer system installed. Although production has been discontinued, immaculate previously owned JS1’s are available across the globe. 


Wingspan 18m 59ft
Wing Area
120 ft²
Aspect Ratio
Maximum Weight
600 kg
1323 lbs
Empty Weight
310 kg
683 lbs
Wingspan 21m 69ft
Wing Area
131.86 ft²
Aspect Ratio
Maximum Weight
720 kg
1587 lbs
Empty Weight
435 kg
959 lbs



The JS1 not only displays good gliding ratio at moderate speeds but also at high speeds and maintains its outstanding climbing performance.

A lightweight structure and a unique double-hole blowing/suction system on the wing enabling very low drag allow the JS1 to reach a top speed of 290km/h. Another gain for speed is water tanks in the wings, a small lift sacrifice for a big advantage.

With the combination of excellent performance, a wide range of available wing loadings and superlative handling, the JS1C-21m is extremely competitive at the highest level, without the disadvantages of older generation Open Class gliders.

The increased wing loading, combined with new tip aerofoils and third-generation winglets gives the JS1 its edge at high speeds.

Performance and Speed specifications

Wingspan 21m 69ft
Wing Area
131.86 ft²
Aspect Ratio
Maximum Weight
720 kg
1587 lbs
Empty Weight
435 kg
959 lbs

Standard Performance Features

  • Control surface gaps sealed with the Streifeneder Teflon/Mylar system
  • Cockpit airflow controlled with an air extractor
  • Integrated bug wiper garages
  • Integrated water ballast tanks in main wings – 180 l
  • Expendable tail ballast tank – 7.5 l
  • Non-expendable tail ballast tank – 5 l
  • JS Louvred Cockpit Air Extractor




A safety is not negotiable the JS1 is a clearly setting the standard. Flying a JS1 will give you a safe feeling with highly desirable flight characteristics.

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 limits SI IMP
Max Speed V NE
280 km/h
151 kts
Max rough air speed V A
208 km/h
112 kts
Max aerotow speed V T
180 km/h
97 kts
Max decent rate MAUW
40 m/s
7874 ft/min
Cockpit crash resistance

Standard Safety Features

  • Triple-panel upper-surface airbrakes
  • Automatically controls, including the water system
  • Flarm™ antenna in top of vertical stabiliser
  • 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
  • Removable nose ballast system

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



The handling characteristic of the JS1 is one of the features that made the JS1 stand out and gain rapid world recognisance.

The JS1 not only offers the serious competition pilot a performance advantage but also remains suitable for every pilot, owing to its excellent handling qualities.

The JS1C-18 EVO redefined handling in the 18 m class by offering improved roll rate and superb control at slow speeds.

Comfort Specifications

Comfort Features SI IMP
Max cockpit weight
115 kg
254 lbs
Maximum size pilot
1.92 m
6 ft 4"
Airbrake locking forces
-15 daN
-33.7 lbf
Cockpit shoulder width
525 mm
20.7 inch
Landing gear retracting forces
-15 daN
-31.5 lbf
Inner wing panel weights
<80 kg
176 lbs

Standard Features for your comfort

  • Elevator trim with sprung-loaded control/position indicator on sidewall
  • 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
  • Oxygen storage tube with cylinder retainer bracket for MH O2 cylinder



After years of hard work the Jonker dream became a reality on 12 December 2006 when the JS1 Revelation with 18m wingspan, flew its maiden flight.

To design the ultimate sailplane, JS’s design philosophy was to develop a glider with both incredible cruise ability, by glide angles at various speeds, as well as outstanding climbing ability, to be able to climb as fast as possible in thermals. The best low-speed laminar airflow in the world was accomplished with the birth of the JS1’s T12 Profile, a design that took five years to perfect.

A fuselage was designed using the latest CFD methods available. Wind-tunnel simulation was done with computers and structural designs were verified with FEMM analysis. Design method verification was done by comparing ANSYS results with measured results.

JS1 was a Revelation when it entered the contest scene in 2010. It immediately proved to be a highly competitive 18m class glider, with amazing handling, and many top contest pilots became part of the JS family. In 2012 Jonker Sailplanes penetrated the open class market with the introduction of the 21m version of the JS1. The outboard wing and wing-wingtip junction was redesigned to accommodate the higher wing loads and a higher maximum take-off mass of 720kg [1587 lb]. JS constantly made small product improvements and with the EVO conversion made in 2014, JS1 pilots felt their upper hand in the class. A Hand Control system, for pilots with reduced leg function, was also completed in 2014, offering disabled pilots access to a high performance glider.

But the JS1 will probably be best remembered as the glider that revived the Open Class – since 2016 more than half of the WGC Open Class entries were flying these “little agile” JS1-C 21’s. What an amazing glider … World Champion in both 18m and Open class in 2017 in Australia!

Currently the JS1 is the only type certified aircraft in South Africa.



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.

*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