Grob G103a Twin II

G103A Twin II
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Role	Two-Seater Class sailplane
National origin	Germany
Manufacturer	Grob Aircraft
Number built	549

The G103 Twin II (originally designated the G 118) is a high performance two-seater sailplane made by Grob Aircraft. The aircraft is of T-tail configuration, and is fitted with a non retractable undercarriage and upper surface airbrakes. Of glass fibre construction, it is designed for training, high performance, and simple aerobatic flying.

Design and development

The G103 Twin II (a.k.a. the Twin Astir II) is the successor of the original G103 Twin Astir with a nose wheel and a fixed six-inch main gear fitted behind the center of gravity - The main wheel is equipped with a hydraulic brake. Modified ailerons produce a substantially improved roll response compared to the previous model. Approach control is by top surface Schempp-Hirth type airbrakes. The G103A Twin II Acro variant features strengthened mainspar caps and steel control pushrods which permit greater aerobatic performance. The Royal Air Force acquired 100 Acros (known as the Viking TX.1) for its Air Cadet training program. The G103 also has a FAA approved modification kit for all-hand control for handicapped operation.

A total of 549 were produced, including 100 Viking TX.1s for the UK Armed Forces before it was succeeded in production by the G103C Twin III in 1989.

Operational history

Records

On 28 September 1981 the Twin II took the world Out & Return record for two-seat sailplanes (1000.88 km/ 621.92 miles).^[1] The aircraft (N424GL) was flown out of the Ridge Soaring Gliderport, Pennsylvania, USA, by pilot Thomas Knauff and crew, Rob Gannon.

On May 14, 1996 the Twin II G103A took the Pennsylvania State Open Multi place class; Distance around a Triangular Course/Speed over a Triangular Course of 100 km; Pilot David Bradley, Passenger Jim Vincent. and the Pennsylvania Sports Class; Distance around a Triangular Course of 100 km; Pilot David Bradley, Passenger Jim Vincent.^[2]

In-Flight Limitations

In 2003 Service Bulletin 315-64/2 reduced the maximum admissible airspeeds and prohibited aerobatic flight. This was due to reports that the design of the fuselage may not have been sufficient to sustain limit loads during certain maneuvers and during flight at certain speeds. Grob completed further investigations into the effects of certain flight conditions on the fuselage structure and the development of corrective procedures. Further static strength tests were conducted to verify the safety margin of the fuselage. The results of these tests restored the original flight speed limitations and maneuver operations for the Twin II and allowed the Twin II Acro only basic aerobatic maneuvers (spins, lazy eights, chandelles, stall turns, steep turns, and positive loops). An approved modification, when incorporated, restores full acrobatic status to these sailplanes.^[3]