Light Jets Yet Another Category

The GROB Aerospace (Tussenhausen-Mattsies, Germany) SPn Utility Jet made its maiden flight in July 2005. Marketed as a light business jet, rather than a Very Light Jet (VLJ), the nine-passenger, single-pilot aircraft is powered by two Williams FJ-44 jet engines, larger than the FJ-33s used by most VLJs, and weighs just under 8,000 lb (about 3,630 kg) empty. With a substantial range of 1,800 nm/2,070 miles (3,400 km), it requires only 3,000 ft (915m) of runway at gross weight (with fuel and passengers). Air taxi, air cargo, air ambulance and private aviation are all target applications for GROB, which got its start 30 years ago, with composite gliders.

The company's COO, Dr. Andreas Strohmayer, explains that the composite airframe is produced with dry carbon fiber woven cloth (0/90° and ±45°), unidirectional fabric tape and individual tows, wet out with epoxy in a wet layup process. Suppliers include Hexion Specialty Chemicals (formerly Bakelite, Duisburg-Meiderich, Germany) for epoxy resins; SGL Technic Ltd. (Meitingen, Germany) and Porcher Industries (Badinieres, France) for woven reinforcements; and Toho Tenax (Wuppertal, Germany) for carbon tows. Tows are placed longitudinally, e.g., along the wing spar caps, for additional strength and stiffness, says Strohmayer. Parts are layed up in composite molds and oven cured. All secondary structures, such as control flaps, landing gear doors, doors, etc., are made in similar fashion.

Strohmayer contends that in the Light Jet category, against competition such as Embraer and Cessna, the SPn Utility Jet provides the largest cabin in the class, yet offers the operational versatility of a turboprop. Static strength tests for the fuselage, wing and tail to ultimate load have been completed and static testing of control surfaces is in progress. European Aviation Safety Agency (EASA) certification is expected in first-quarter 2007, with U.S. Federal Aviation Admin. (FAA) approval shortly thereafter.