GROB STRATO1 / G 520 EGRETT / G850 STRATO 2C
In 1988 GROB were awarded a contract by the German Federal Ministry for Research and Technology to develop an advanced high altitude research aircraft, the G520 Strato 1. GROB stated that the aircraft was intended to undertake communications monitoring, geophysical research, pollution and weather monitoring. Whether a market actually existed for this type of aircraft, particularly as many of these functions can now be easily be undertaken by commercial satellites, remains a matter of debate.
To test their plan to construct an all-composite aircraft, GROB decided to build a proof of concept aircraft known as the Strato 1 /E. Powered by a single 750 shp Garrett TPE 331-14 engine driving a four blade composite propeller of 3.4m diameter, this aircraft had a pressurised cockpit for the pilot and a wingspan of 33m. Capable of carrying a payload of 1,000kg, the aircraft had a range of 4,000km, an endurance of 13hrs and could operate up to 50,000ft.
GROB then pressed ahead and within 11 months a second design, the G 520 Strato 2C, took to the air. Built entirely of composite material and with a 108ft wing span, the aircraft was the world’s largest all composite fully-certified manned aircraft. During flight tests the aircraft quickly demonstrated its potential by climbing to an altitude of 53,574ft and capturing five FAI records for altitude, time to climb and flight endurance.
Building on the success of the G520 Strato 1, GROB then designed and built the even larger G850 Strato 2C, again using fibre composite materials. Powered by two turbocharged Teledyne TSIOL-550 pusher engines, with a five blade propeller of 6 meters diameter, the G850 Strato 2C soon demonstrated the ability to remain airborne for up to 50hrs and could in theory fly approximately half way around the world. During a typical surveillance / research mission the aircraft would carry a crew of two pilots and two operators / scientists in a reasonably roomy pressure cabin over a 3,500km radius of action, lingering around for over 8hrs between 50,000 and 75,000ft as the fuel burnt off.
These unusual, but highly capable, aircraft were used for a number of research projects when they first entered service, however, their current use and whereabouts is unknown.