In a quiet corner of Bavaria, some 60 miles west of Munich, lies the picturesque airfield of Tussenhausen-Mattsies, home of Grob Aircraft since the company’s founding in 1971. MS&T’s Europe Editor Dim Jones recently paid a visit and learned more than expected.

An independent company until 2008, Grob Aircraft SE is now a 100% subsidiary of H3 Aerospace GmbH. The Tussenhausen-Mattsies site accommodates research, development, manufacturing and assembly facilities. The company has become known as one of the world’s foremost manufacturers of composite aircraft; more than 3,800 have been delivered, and they have flown more than seven million hours on five continents. Grob manufactures three main categories of aircraft: gliders and motor-gliders, basic trainers, and high-altitude research aircraft.

Many will be unaware – as I confess I was – that, in the early 90s, Grob built a prototype high-altitude research aircraft designated the G 850 Strato 2c. Commissioned as an ‘atmospheric, stratospheric and climatic’ research aircraft by the German Aerospace Centre (DLR), the Strato 2c had composite high-aspect-ratio wings with a 56m span, on which were mounted twin-turbocharged piston engines. It could accommodate two pilots plus two scientists and their mission equipment. The project was cancelled by the DLR in 1996, but not before the Strato 2c had set a new altitude record for manned piston-engined aircraft of 18,552m (60,897ft) on its 29th and final flight. It now sits outside the Grob Headquarters building at Mattsies.

G 120TP

More of high-altitude surveillance later, but Grob’s current reputation is built on light military training aircraft, and specifically the G 120TP. The 120’s genesis however, was in the G 109 self-launching motor glider, which first flew in 1980; the G 109 has a 17.4m wingspan, is powered by a 95HP Grob 2500 engine, and has side-by-side seating for instructor and student. Already an established aircraft in civilian use, the G 109B entered RAF Service in 1991 as the Vigilant T1, and was used until this year for air cadet training in the Volunteer Gliding Squadrons. From the 109, Grob developed the G 115, a general aviation trainer of glass-reinforced plastic (GRP) construction, fully aerobatic, with fixed tricycle undercarriage and a 180HP four-cylinder piston engine. The 115 is in military service with 10 air forces worldwide, notably the Egyptian Air Force, which has 74 aircraft; Australia, which uses it for screening; and the RAF, which uses its 89 115Es, known as the Tutor T1, for elementary training and for University Air Squadrons and Air Experience Flights. The G 120A is a further development of the G 115TA; powered by a Lycoming six-cylinder piston of 260HP, the GRP has given way to carbon-fibre-reinforced plastic, and the predominantly military usage is reflected in the ability to accommodate students wearing military flying equipment and helmets. The G120A has a Garmin avionics suite, and is in service with Canada, France, Israel and Kenya.

The G 120TP was born of a perceived market for a sophisticated low-maintenance training aircraft providing increased training capacity. It was developed from the 120A, but its turboprop engine with five-bladed propeller, retractable undercarriage, and full glass cockpit make it essentially a new aircraft. The G 120TP first flew in 2010, and EASA certification was completed in 2013. The fuselage is GRP, and the wings carbon fibre composites with winglets; the fuselage life cycle is 15000 hrs. The main gear is integral to the wings, which detach easily, being connected via the mainspars, the cores of which are, unusually but in keeping with traditional aeronautical engineering, made of wood. For destinations too distant for delivery by air, two disassembled aircraft fit neatly into a standard 40-ft container.

The Rolls Royce M250-B17F turboprop (formerly the Allison Model 250) is a proven engine which delivers a maximum of 456SHP, giving the aircraft an impressive power-to-weight ratio and a lively performance, with a cruise speed of just over 220KTAS, a range of over 700nm, an endurance of 5.4 hours and a maximum operating altitude of 25,000 ft (for which the oxygen system is required, the cabin is unpressurised). The G 120TP is fully aerobatic, stressed to +6/-4G, and can be operated VFR or IFR.

The avionics, fronted by four 6x8 full-colour MFDs, is a COTS Genesis Aerosystems IDU-680 EFIS, custom adapted for the 120TP. The student can sit in either left or right seat (usually on the right). The two pairs of MFDs are fully configurable, and a standby attitude indicator is positioned between them. The aircraft is also equipped with an autopilot and a radar altimeter, and the system is ‘terrain aware,’ displaying topography in the main flight instrument display. Two configurations of canopy are available, standard or – for added visibility – all-transparent; the latter thus far has only been requested by Jordan and in that climate will make the air conditioning system work for its living.

The G 120TP launch customer was Indonesia, and subsequent buyers include Argentina, Jordan, Mexico, and Myanmar. The US Army selected the 120TP and its ground-based training system for its academy at Dothan Regional Airport, Alabama, operated by CAE (see MS&T Issue 6-2017). Ascent Flight Training, on behalf of the UK RAF, has just taken delivery of 23 aircraft, designated the Prefect T1, as part of the Military Flight Training System (MFTS), superseding the 115 in the elementary flying training role. The Empire Test Pilots School (ETPS) at Boscombe Down, UK has also acquired two aircraft as part of their new training fleet, and the first two staff pilots were undergoing type conversion at Mattsies when I visited; since then, two more have been checked out. Grob generally provide training in Germany for instructor cadres (both aircrew and maintenance) from customer countries, although they would offer ‘power-by-the-hour’ support in-country if requested; post contract support in-country is typically two persons for 2-3 years.

Grob’s Tussenhausen-Mattsies facility.  The G 850 Strato 2c is in the foreground.

The company makes a full range of training devices to suit customer requirements, developed and supported by Grob Training Systems (GTS). The portfolio ranges from tablet-based computer-based training through classroom training, instructor-led if required, to a full-mission simulator, with a nine-channel visual giving a field of view of 300o horizontal by 165o vertical. The FMS is easy and quick to start up and align, requires only 30 minutes of maintenance per day, and has an availability of 95% or better. The Instructor Operating Station comprises two touch-screen and two flat-screen monitors, plus a remote control tablet that permits operation of the IOS from other locations, including the FMS cockpit itself. In advance of the formal pilot training process, the in-house-developed Pilot Selection & Evaluation System (PSES) utilises a combination of methods to test candidates on basic pilot skills, psychomotor abilities and operational competencies, all focused on reducing subsequent attrition rates and, therefore, reduction in pilot training costs.

The 120TP is clearly a sophisticated and capable aircraft of its type, and this means that the core customer base is likely to be exclusively military (although it would make an excellent general aviation aircraft for anyone with the necessary funds). The performance, avionics, glass cockpit and side-by-side seating make it the ideal elementary or basic trainer – indeed probably too capable for mere screening – and, when teamed with a follow-on tandem-seat trainer such as the PC-21 or T-6 Texan, could provide pilot training right through to Phase 4 LIFT and the front line; indeed, this is what is now planned in the Royal Jordanian Air Force.

The Grob G 520T high-altitude reconnaissance aircraft, forerunner of the G 520NG.
The Grob G 520T high-altitude reconnaissance aircraft, forerunner of the G 520NG.

High Altitude G 520NG

Returning to the ISR theme, in the late 80s/early 90s, and before the reunification of Germany, Grob, in partnership with E-Systems and Garrett, and in response to a joint German Air Force/USAF requirement, produced a single-turboprop high-altitude reconnaissance aircraft, designated the G 520 Egrett, designed to carry 1000kg of mission equipment to a loiter altitude of 52,000 feet, its job to patrol the IGB (Inner German Border) and survey the other side – U2 on the cheap. However, Eastern Europe soon ceased to be perceived as a threat and, in 1993, the programme was cancelled. Only five single-seat aircraft were produced, plus one two-seater, the G 520T. Four single-seaters remain, one at Mattsies and the other three operated by contract companies in the US. The two-seater was operated for some years by Airborne Research Australia in Adelaide but was flown back in 2014 by one of Grob’s test pilots, Tom Reinert, who showed me around the aircraft. The company now perceive that there is, once again, a market for the sort of low-cost ISR capabilities the G 520 can provide.

The aircraft is one of the world’s largest fully composite manned aircraft. It has a very-high-aspect-ratio wing with a 33m (108ft) span, and still holds four world time-to-height records for propeller aircraft. The original Garrett TPE 331-14F engine is a ‘straight turbine,’ maintaining a constant RPM from take-off to landing, varying only the torque through the variable-pitch Hartzell four-bladed propeller. A Pratt & Whitney PT6A-67, which would reduce the service ceiling to 45,000ft, would power future production aircraft. The fuel consumption halves between FL250 and FL450, although a balance has to be struck with oxygen consumption. Neither variant is equipped with ejection seats.

The controls are wholly manual and, according to Reinert, light and positive at high level but somewhat heavy in roll at low level. The return trip from Adelaide to Germany took 40 flying hours over seven days, the first leg all the way to Darwin because of the lack of an intermediate landing site that could support the aircraft starting system. The 520T is currently being modified to fit a total-authority autopilot, which would also allow the aircraft to be operated remotely. The instrumentation is still ‘steam-driven’ and analogue, but fitting the same Genesys Aerosystems EFIS as on the 120TP is an option and, indeed, the ‘glossy brochure’ shows a multi-screen rear cockpit operator’s station in the G 520NG, successor to the G 520T.

The G 120TP Full-Mission Simulator.
The G 120TP Full-Mission Simulator.

The majority of the equipment bays are in the ventral area and are not integral to the fuselage structure. There is provision for extension to both the ventral and dorsal areas, and for two low-drag wing pods, one of which currently houses a weather radar. The sensor and mission equipment options, provided by H3 Mission Systems, are almost limitless – EO/IR, retractable camera, Airborne Electronically Scanned Array Synthetic Aperture Radar (AES/SAR), ESM, Multi-link A/A and A/G connectivity, and Electronic Intelligence (ELINT) systems, to name but a few, and have utility across a wide spectrum of civilian and military ISR requirements.

So, my visit to this peaceful and scenic corner of Bavaria and its self-contained aircraft company, which was intended to concentrate exclusively on training aircraft and, in particular, the Grob G 120TP, turned out to be much more wide-ranging, and extremely interesting. I have no doubt that the G 120TP Training System, and whatever may spring from it, will continue to be a market-leader in its class of training aircraft; I will also be very interested to see whether the G 520NG programme ‘takes off.’  

Originally published in Issue 4, 2018 of MS&T Magazine.