Frequently Asked Questions
 

Certification

Q: Will the JS1 be type certified?

A: The JS1-A and JS1-B are designed according to CS-22 specifications. The South African type certification has been issued and Jonker Sailplanes is currently working towards FAA and EASA type certification. For FAA certification, South Africa and the United States have a long-standing Bilateral Airworthiness Agreement (BAA). The South African Civil Aviation Authority (CAA) and the American FAA have established communication and are collaborating per the specifics of the BAA.

The South African CAA has also issued its "Aircraft Design Organisation Approval" to the Jonker Sailplanes factory. In many ways, this is considered to be a more significant milestone than the aircraft type certification.

Q: The JS1 is designed under CS-22 to a safety factor of 1.725. The static test on the website appears to be carried out at ambient temperature rather than the normal test at 54°C (129°F). Did you carry out a further static load test at 54°C?

A: The JS1 is designed according to the CS-22 standard. For the aircraft type certification Jonker Sailplanes had to prove that all aspects of the standard were complied with and the process for type certification took many months. Officially observed tasks did include destructive structural tests under specific environmental conditions.

Note that the static test referred to was required in order to obtain authorization to fly the prototype prior to the full certification tests. At the time, the South African CAA required a number of documents, including design documents, inspections, and partial tests. One of the tests was a structural test to the ultimate flying loads (at ambient temperatures and without the safety factor multiplier). This test did not override the type certification test - the certification tests were done officially under controlled conditions once the aircraft performance was verified and the formal certification plan was approved.

Q: What are the limit loads for the JS1?

A: The limit loads depend on glider weight. At 360 kg (793 lbs) the limit loads at V_A are +8.0g / -4.5g. At 600 kg (1322 lbs) the limit loads at V_A are +5.5g / -2.7g. For all glider weights the limit loads decrease linearly from their respective V_A values to +4.0g / -1.5g at V_D.

Weights

Q: What is the actual empty weight?

A: 313kg (690lbs) ready to fly.

Q: What are the max and minimum cockpit weights?

A: The min-max range is 70kg to 110kg (154lbs to 243lbs). The max cockpit weight can be increased easily to 130kg or 287lbs (without the self-launch installation). Extreme pilot weights can be accommodated by special weight & balance of the glider. The JS1 has dual tail ballast tanks and a brass tailwheel is available in place of the Vesconite^TM tailwheel.



Wings

Q: What is the weight of a 7.5 meter inner wing panel?

A: Approximately 80kg (176lbs).

Q: Why are the wing panels this heavy?

A: With the thinnest wings in its class, the JS1 wings require a lot of carbon fiber to meet the design strength and achieve a safety factor of 1.725. The design weight of the non-lifting parts is also set intentionally high to accommodate a self-launch system of 100kg (220lbs).

Q: Is it true that the airfoil is based on one of its competitors?

A: The T12 profile is specifically designed by Johan Bosman for the JS1, but as is the case with the airfoils on many modern sailplanes, similar design methods are often used in the industry.

The profiles were verified by Johan Bosman while at Delft University, and design assistance & confirmation were provided by Dr. Loek Boermans.

Q: I am sure you are aware of the shrinkage that other manufacturers have with their latest models. It is a real problem that they have yet to correct. Will you have the same problem?

A: Jonker Sailplanes has taken measures to avoid skin shrinkage, and hence expensive wing profiling within a few seasons. Specifically, the carbon spar caps are bonded wet-on-wet directly to the skins during the initial lay-up in the molds. This eliminates a thick structural filler (flox) bond between spar caps and the skins, considered to be the main source of shrinkage. The shear webs are bonded at a later stage to the sparcaps – so all flox bonds occur between the shearweb and spar caps. The bond area has a high safety factor and all are post-cure inspected with a borescope. There is also no reduction in the foam thickness near the spar - the bending strength is not affected as with other methods.

Q: Why does the JS1 have more wing area than some of its 18-meter competitors?

A: The JS1 Revelation's wing is optimized for the full range of conditions encountered in competition. Jonker Sailplanes believes it is a given that sailplanes must be able to run fast to hold a contest lead, but we also believe that contests are very often won on weaker days (as was recently demonstrated in the South African Nationals). The JS1 wing provides outstanding climb performance and, with its thin airfoil, also has exceptional high speed performance. We feel that the JS1 wing has the best balance between airfoil type, wing area, and both low and high speed characteristics.



Fuselage

Q: Is there a way for air to vent from the cockpit to the tailboom, and from the tailboom out through the tail?

A: The cockpit pressure releases through the tailboom and exits at the rudder control horn covers.

Q: Does the tail ballast water tank fill from the top or from the bottom?

A: The JS1 has two tail tanks, the standard ballast tank (which can be dumped in flight along with the main wing tank ballast) and an optional pilot c.g. tank to tune the weight and balance (which cannot be dumped in flight). Both tanks have special quick-connect fill ports flush-mounted with the skin of the vertical stabilizer. Unlike other gliders, this allows the standard tail tank to be filled even after filling the main wing tanks. The standard tail tank can also be filled via the dump outlet behind the tailwheel if filled prior to the wing tanks. The pilot c.g. tank can be filled or drained independently.

Q: Is the fuselage the same as some of its competitors?

A: As with any new design, the development of the JS1 included (1) thorough engineering review of all published technical literature pertaining to cockpit design for crashworthiness and (2) benchmarking of other competitive sailplanes representative of what today's contest pilots require and expect. Generally, the aerodynamic shapes of glider fuselages have converged to optimum and are mostly sorted out. The shape of the JS1 fuselage is understandably influenced by several proven gliders and the published literature.

The composite structure of the JS1 cockpit owes much to the pioneering cockpit design methods and research of several notable sailplane designers and academics. To build upon this and ensure the best crashworthiness, Attie Jonker and his engineering team performed extensive materials tests, finite element analyses, and loading to assure the structure of the JS1 fuselage meets airworthiness requirements and provides maximum protection to the pilot.

Q: Do you expect to have more clearance for the landing gear doors?

A: The photos of the prototype landing gear show the doors hinged open by about 90 degrees. The gear doors on the series production sailplanes open wider to further increase the ground clearance.

Q: What is the size of the standard storage tube for the oxygen cylinder?

A: The standard O₂ storage tube is located in the fuselage center section behind the pilot's right elbow. Gliders up to serial number 015 accept a Mountain High AL-180 cylinder or an Aerox AV54G cylinder. Gliders from serial number 016 accept a Mountain High AL-248 or Aerox CV54G in the standard storage tube. A regulator with "radial" (as opposed to "axial") outlet is recommended.

A complete MH system (EDS O2D1-180-1P-F or EDS O2D1-248-1P-F) with cylinder, regulator, flow controller, service line, cannula, and face mask is available directly from Mountain High, from Jonker Sailplanes, or from our regional JS agents. For long duration or very high altitude flights additional oxygen cylinder storage tubes are available on a custom basis (example: an additional Mountain-High AL-415 aft of the baggage area).



Trailer

Q: What trailer options are available?

A: Cobra trailers are available for the JS1 from Spindelberger. Contact JS for further information regarding shipping your JS1 Revelation from the factory in a Cobra.

Q: What is the difference between the trailer for the JS1-A and JS1-B?

A: The trailer for the JS1-A has a larger fin to accommodate the taller tail of the A model. The B version glider fits in the JS1-A trailer, but not vice-versa.



Engine

Q: When will the sustainer be available?

A: Development of the jet sustainer is ongoing with several refinements to the system such as spark ignition and direct kerosene start. Fuselages from serial number 013 onward have shipped (if customer requested) with the jet sustainer engine-bay pre-installed.

Q: When will the self-launcher be available?

A: Jonker Sailplanes is in the process of fitting the complete engine system into a JS1 self-launch prototype. The powerplant system is a based on the two-cylinder Solo 2645 as used in several other production sailplanes ensuring maximum pilot familiarity and serviceability.

Q: Any plans for electro version?

A: Not yet, but when this technology is matured, we will definitely consider it.



General

Q: Can I expect to see the JS1 at AERO 2011 in Friedrichshafen?

A: We will attend AERO 2011 in Friedrichshafen, Germany and the 2012 SSA Convention in Reno, Nevada.

Q: Is it possible to test fly the JS1?

A: Evaluation flights of the JS1 at our regional locations (Holland, UK, and USA) are absolutely available to pilots with sufficient qualifications. Interested parties are also welcome to visit Jonker Sailplanes' manufacturing facilities in Potchefstroom, South Africa for a factory visit and evaluation flight (temporary South African pilot certification required). Please feel free to contact us for details.

Purchasers of JS1 sailplanes are also encouraged to consider a Soaring Safari to visit the Jonker Sailplanes facilities, inspect their glider, and fly their sailplane in the southern hemisphere prior to ocean shipment. Jonker Sailplanes is able to organize temporary South African aircraft registration and CAA pilot certification based on foreign licenses.

Q: What address should be used when mailing or shipping items to the factory?

A: Please use the post office box address when sending by postal mail and the physical address when shipping by courier or freight carrier: