Last update 28 November 2015
TST-14 BonusJet Frequently asked questions:
Q: Who manufactures the BonusJet?
A: The BonusJet is based on the TST-14 'Bonus' sailplane produced by TeST (a division of Comp_Let) in the Czech Republic. The Bonus was originally produced as an unpowered sailplane, or with the option of a Rotax piston engine and propeller. The BonusJet has been modified by the addition of a PBS TJ-100 engine (also produced in the Czech Republic) in place of the original Rotax. The jet engine retract hardware was designed by Desert Aerospace, LLC, and the jet conversion was done in the US by Desert Aerospace, LLC.
Q: Is the BonusJet available as an LSA?
A: The original TST-14 'Bonus' sailplane was produced as an LSA. As of this writing, turbine (jet) engines are not allowed on LSA aircraft. It may be possible to get a waiver.
Q: What is the cruise range of the BonusJet?
A: The BonusJet was designed as a self-launching sailplane. It has a much higher cruise speed than most other motorgliders, allowing it to reach good soaring conditions a fair distance from the takeoff point. We routinely cruise 20 miles upwind of our airport to contact wave. While it is possible to cruise more than 150 miles, the relatively high fuel burn rate makes the BonusJet somewhat impractical for "airplane-style" cross country cruising.
Q: What is the climb performance of the BonusJet?
A: With two people on board, the BonusJet has consistently demonstrated climb performance better than 1000 ft/ min (1200' MSL, 80F). To date, most flights have been from our home airport located in Moriarty, New Mexico. The elevation at Moriarty is 6200' MSL, and the density altitude often exceeds 10,000'. Climb performance at these conditions is still exceptional at approximately 700 ft/min. The BonusJet's climb far exceeds any other motorglider we have compared with (Stemme, DG-505, ASH-26E). We anticipate conducting a complete flight test program later this year at lower elevation to establish true climb performance numbers.
Q: What is the takeoff distance of the BonusJet?
A: We estimate a sea level takeoff distance of approximately 500'. To date, most flights have been from our home airport located in Moriarty, New Mexico. The elevation at Moriarty is 6200' MSL, and the density altitude often exceeds 10,000'. Takeoff distance performance at these conditions is still exceptional, at approximately 700'. We routinely launch mid-field with two persons while some other motorgliders are waiting for a tow, unable to self-launch in the hot & high conditions. The BonusJet's takeoff requirements are considerably better than any other motorglider we have compared with (Stemme, DG-505, ASH-26E). We anticipate conducting a complete flight test program later this year at lower elevation to establish true takeoff performance numbers.
Q: How much fuel can be carried in the BonusJet?
A: With 24 gallons fuel, the BonsuJet can fly for approximately 1.5 hours, depending on climb duration and cruising speed. Typical cruise speed at 10,000 MSL is around 100 knots, giving it a range of up to 150 nautical miles. The BonusJet was designed primarily as a self-launching soaring motorglider, not a cross country cruiser. However, it is good to know you have some range and speed available for reaching good soaring conditions or a quick dash return home if bad weather is looming. Fuel capacity may be reduced when carrying a passenger.
Q: What is the cost of the BonusJet?
A: As of this writing, the cost is approximately $195,000 (USD), including jet engine, engine installation, basic instruments and trailer. The cost will vary somewhat depending upon exchange rate, instruments and accessories.
Q: What is the engine extend/retract procedure?
A: Two switches control all engine extend/retract/start functions. They are simply 'Pylon' (up/down - momentary) and 'Engine' (run/stop). Door actuation is handled automatically by a door/pylon sequencer when pylon commands are given.
Q: What is the L/D of the BonusJet?
A: Factory specifications show a max L/D of 39:1.
Q: What are the advantages of a jet motorglider over more conventional piston/prop motorgliders?
A: The advantages of jet power over conventional piston/prop are numerous. The jet engine is extremely simple, and at 42 pounds, it is only about 1/3 the weight of equivalent piston engines. It does not require any belt drives, speed reducers or massive pylons. It reqiuires very little input from the pilot for starting, and does not require any prop positioning or 'bumping' for retraction. When extended, the jet engine has about the same drag as a single Cessna 172 wheel pant. The jet engine also produces almost no vibration, eliminating the most significant cause of cracking and fatigue failures in all aircraft systems, including the structure and avionics. Also looming on the horizon is the elimination of 100LL (leaded) avgas. The BonusJet uses jet fuel, which does not contain lead.
Q: How much fuel is used for a typical self-launch?
A: At Moriarty, NM on a summer day (10,000' density altitude), a typical launch to 2000' with some loiter time to make sure the first thermal is centered uses about two gallons of fuel.
Q: How loud is the BonusJet on takeoff?
A: More testing needs to be conducted, but our initial test shows the following noise levels, measured 200 feet directly aft for Callair towplane and BonusJet (other aircraft shown for comparison):
Callair towplane: 74.2 Db
BonusJet at 90% RPM: 77.4 Db
BonusJet at 98% RPM: 82.6 Db
Small homebuilt airplane (takeoff - type unknown): 84.2 Db
Cessna Citation B (taxiing): 86.1 Db
Cessna Citation B (takeoff): 95.1 Db
Noise level of the jet engine dissipates quickly with distance, and doesn't seem to carry as far as the 'growl' of a towplane propeller.