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Sailplane · JS4

JS4 Rengeti

The most modern Standard Class sailplane: 15 metres without flaps, optionally with 18-metre wingtips and the MD-TJ-42 jet sustainer — built to make world champions.

The JS4 shares the low-drag fuselage and large cockpit of the JS3, combined with newly optimised airfoils and fifth-generation winglets. As the official JS partner in Switzerland we configure it personally.

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Why the JS4

The JS4 is designed for all pilots — from the club fleet to competition. Without flaps it stays simple in the cockpit and on the ground, and its carefully selected standard equipment makes it the best value-for-money new glider on the market.

The cockpit carried over from the JS3 offers exceptional forward visibility — 12-o'clock traffic stays visible even slightly below the horizon. Available as a pure glider or with a jet sustainer for the security to get home, and with optional 18-metre wingtips it is at home outside the Standard Class too.

46.5 : 1
Best glide ratio
15 m
Standard Class
18 m
Optional wingtips
JET
Optional sustainer
Studio side view of the JS4 Rengeti sailplane

Technical data

15-metre Standard Class configuration. The optional 18-metre wingtips change wing area, aspect ratio and performance accordingly.

Best glide ratio (L/D)46.5 : 1
Wingspan15 m (18 m option)
FlapsNone (Standard Class)
Wing area10.0 m²
Aspect ratio22.6
Empty weight280 kg
Max. take-off weight525 kg
Water ballast174.7 l
Minimum sink0.64 m/s
Wing loading36.0–52.5 kg/m²
Never-exceed speed (VNE)280 km/h
Manoeuvring speed (VA)208 km/h
Max. aerotow speed180 km/h
Max. pilot height1.95 m
Max. cockpit load115 kg
Cockpit crash resistance9 G

Cockpit & comfort

  • Cockpit carried over from the JS3 with exceptional forward visibility
  • Electrically in-flight adjustable pedals, adjustable seatback with headrest
  • Forward-opening canopy, green-tinted for extra UV protection
  • Leather interior with storage pockets, 525 mm shoulder width

Performance & safety

  • Safety cockpit in carbon and aramid fibre with integrated crumple zones
  • Airfoils optimised by PSO algorithm, fifth-generation winglets
  • Optional 18-metre outer wings for extra performance outside the Standard Class
  • Teflon/Mylar control-surface gap sealing, integrated bug-wiper garages
  • Dynafoam seat cushion, Flarm antenna and hydraulic disc brake

Propulsion options

Pure glider

The JS4 is available as a pure sailplane — light, simple and uncompromisingly focused on Standard Class performance.

MD-TJ-42 jet sustainer

Optionally with the MD-TJ-42 jet sustainer for climb support and the security to get home. Operation is as simple as it gets: one switch, one throttle dial. Not self-launch; no RES or combustion variant planned.

Class, clubs & certification

A Standard Class single-seater with a 15-metre span and no flaps — simple to fly, simple to instruct on and simple to look after. That is exactly what makes it an ideal club aircraft and a Standard Class competition machine at the same time; with the optional 18-metre wingtips it also flies outside the class. The JS4 will be certified under EASA CS-22; first flight is planned for December 2026.

Complete technical data, manuals and brochures from the manufacturer Jonker Sailplanes.

Full specifications & downloads

Request an Offer

Interested in this aircraft? Request a no-obligation offer — we will get back to you personally.

Wingspan
Propulsion