Grob Strato 2C
| Strato 2C | |
|---|---|
 Grob G 850 Strato 2C based in Mindelheim-Mattsies | |
| General information | |
| Type | High Altitude Research Aircraft |
| Manufacturer | Grob Aircraft |
| Status | Prototype only |
| Number built | 1 |
| History | |
| First flight | 31 March 1995 |
| Last flight | 4 August 1995 |
The Grob Strato 2C is a German experimental high-altitude research aircraft. Powered by two turbocharged piston engines and featuring an extremely long-span wing of composite construction, the sole example was built in the 1990s. Although the development program was abandoned, the aircraft set a world altitude record for piston-engined aircraft on its final flight.
Design and development
[edit source]In April 1992, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt e.V - DLR) commenced a programme to develop an aircraft to carry out atmospheric, stratospheric and climatic research.[1] It chose Grob Aerospace to design and build an aircraft to meet these requirements, based both on its experience in use of composite material in aircraft structures together with its successful development of the Egrett surveillance aircraft, with the aircraft expected to be operational by 1996.[2]
To meet the requirement to operate at an altitude of 24,000 m (78,700 ft) for 48 hours,[3] Grob designed a twin-engined aircraft with a straight, very high aspect ratio wing of 56.5 m (185 ft 4½ in) span.[4] The wings featured winglets, and were mounted across the top of the fuselage which terminated in a T-tail configuration. The aircraft was designed to be crewed by two pilots, and could accommodate two scientists and associated mission equipment in a pressurised cabin. A galley, rest facilities and a toilet were provided.[1]
Unlike the Egrett, which was powered by a single turboprop engine, the Strato was powered by two wing-mounted pusher compound engines consisting of a turbocharged piston engine supplied by the low- and intermediate-pressure compressors and associated turbine machinery derived from a PW127 turboprop engine. Together with the piston engine's own turbocharger, this formed a three-stage turbocharging system that provided pressurised intake air at high altitude.[5] This had the advantage of maintaining power at high altitudes.[4] Each engine drove a 6 m (19 ft 8 in) diameter five-bladed propeller.[1]
The propulsion system was developed under a programme of less than three years and a total development cost of less than DM30 million. To reduce cost and development risk, existing components were used wherever possible. The two-spool gas generator of the PW127 was selected for the low-pressure charger because it was a proven component incorporating advanced compressor and turbine technology, although its adaptation resulted in penalties in weight and efficiency and required a separate oil-supply and scavenge system.[6]
The PW127-derived unit formed a two-spool low-pressure turbocharger incorporating low- and intermediate-pressure compressor stages and their associated turbine machinery. Exhaust leaving the piston engine's high-pressure turbocharger was supplied to the unit through a hot-gas distributor and twelve supply tubes. A new compressor-inlet case without the original accessory gearbox was fitted, while the low-pressure charger used its own lubrication and control systems. It could be disconnected at lower altitudes by an electrically operated hot-gas bypass valve, with intake air continuing to pass through the slowly windmilling compressors.[6]
After each of the three compressor stages, the charge air was cooled to about 0 °C (32 °F) by air-to-air coolers. Cooling airflow was regulated by a movable inlet flap in the forward part of the nacelle according to altitude, ambient temperature and engine power. A digital control system matched the compressor stages during steady and transient operation, operated the low-pressure-charger bypass and bleed valves, regulated cooling airflow and limited rotor speed and manifold pressure.[6]
Construction of the airframe moulds started mid-November 1992, with airframe construction beginning in April the following year, starting with the tailplane. The airframe was completed in 1994, and engine installation commenced.[1]
Operational history
[edit source]The prototype first flew on 31 March 1995.[7] Costs overran, however, and the prototype, which was intended as a proof-of-concept aircraft with off-the-shelf equipment and a heavier wing structure than planned for the production aircraft,[8] was late and did not deliver the expected performance.[9]
On 4 August 1995, during its 29th and ultimately final flight, the aircraft set a world altitude record for a crewed piston-engined aircraft of 18,552 m (60,867 ft).[10][11] The DLR cancelled the programme in 1996.[12]
The sole prototype is on static display outside Grob Aircraft's headquarters at Mindelheim-Mattsies Airport.[13]
Specifications (Strato 2C)
[edit source]
Data from Brassey's World Aircraft & Systems Directory 1999/2000[14], except where noted
General characteristics
- Crew: 4
- Length: 23.98 m (78 ft 8 in)
- Wingspan: 56.5 m (185 ft 4 in)
- Height: 7.76 m (25 ft 6 in)
- Wing area: 150 m2 (1,600 sq ft)
- Aspect ratio: 21.3[15]
- Airfoil: DLR LH37[16]
- Empty weight: 6,650 kg (14,661 lb)
- Max takeoff weight: 13,350 kg (29,432 lb)
- Powerplant: 2 × Teledyne Continental TSIOL-550-A liquid-cooled six-cylinder horizontally opposed piston engine, 300 kW (400 hp) each with three-stage turbocharging comprising a high-pressure turbocharger and a PW127-derived two-spool low-pressure turbocharger, with charge-air cooling after each compressor stage[6]
- Propellers: 5-bladed MT-Propeller MTV-8-H-F constant-speed, feathering pusher propeller[16], 6 m (19 ft 8 in) diameter driven through a 4.87:1 two-stage reduction gearbox[6]
Performance
See also
[edit source]Related development
References
[edit source]- a Estimated performance.
- 1 2 3 4 Taylor, 1996, p.173.
- ↑ Jeziorski Flight International 31 January - 6 February 1996, p.66.
- ↑ Galleithner 2004, p.552.
- 1 2 Bents et al. 1998, p.4.
- ↑ von Gersdorff, Kyrill; Grasmann, Kurt; Schubert, Helmut (1995). Flugmotoren und Strahltriebwerke (in German) (3rd ed.). Bonn: Bernard & Graefe Verlag. pp. 227–230. ISBN 3-7637-6107-1.
- 1 2 3 4 5 Tönskötter, H.; Scheithauer, D. (25–29 September 1995). The STRATO 2C Propulsion System—A New Compound Engine and Control Concept for High Altitude Flying. AGARD Propulsion and Energetics Panel 86th Symposium on Advanced Aero-Engine Concepts and Controls. Seattle, Washington: Advisory Group for Aerospace Research and Development. pp. 6-1 – 6-13. AGARD-CP-572.
- ↑ Jeziorski, Flight International, 12–18 April 1995, p. 16.
- ↑ Taylor, 1999, p. 152.
- ↑ Jeziorski, Flight International, 31 January–6 February 1996, p. 67.
- ↑ Taylor, 1999, p. 151.
- ↑ "Strato 2C sets altitude record for piston-engined aircraft". Aviation Week & Space Technology. 21 August 1995. Retrieved 25 July 2026.
- ↑ Jeziorski, Flight International, 10–16 July 1996, p. 4.
- ↑ "Grob Aircraft". MST Magazine. 2018. Retrieved 25 July 2026.
- ↑ Taylor, 1999, pp. 151–152.
- ↑ Kießling, F.; Rippl, M. (26–28 June 1995). Aeroelastic Investigations on High-Altitude Research Aircraft Strato 2C. International Forum on Aeroelasticity and Structural Dynamics. Manchester, United Kingdom. Retrieved 25 July 2026.
- 1 2 3 Schawe, Dirk; Rohardt, Claas-Hinrik; Wichmann, Georg (January 2002). "Aerodynamic design assessment of Strato 2C and its potential for unmanned high altitude airborne platforms". Aerospace Science and Technology. 6 (1): 46. doi:10.1016/S1270-9638(01)01127-0.
Bibliography
[edit source]- Bents David J., Mockler, Ted, Maldonado, Jaime, Harp, James L.Jr., King, Joseph F. and Schmitz. Paul C. Propulsion System for Very High Altitude Subsonic Unmanned Aircraft . NASA/TM—1998-206636. Cleveland, Ohio: NASA Lewis Research Centre, April 1998
- Galleithner, Hans. "High Altitude Research Aircraft as Further Examples of the Application of the Fibre Composite Technology". Aeronautical Research in Germany: From Lilienthal Until Today . Ernst-Heinrich Hirschel, Horst Prem, Gero Madelung. New York: Springer-Verlag, 2004. ISBN 3-540-40645-X.
- Jeziorski, Andrzej. "Strato 2C takes flight but funds stay low". Flight International. 12–18 April 1995.
- Jeziorski, Andrzej. "High and Dry". Flight International. 31 January - 6 February 1996. pp. 66–67.
- Jeziorski, Andrzej. "DLR cancels Strato 2C contract". Flight International. 10–16 July 1996, p. 4.
- Taylor, M.J.H. Brassey's World Aircraft & Systems Directory: 1995/1997 Edition. London: Brassey's, 1996. ISBN 1-85753-198-1.
- Taylor, M.J.H. Brassey's World Aircraft & Systems Directory: 1999/2000 Edition. London: Brassey's, 1999. ISBN 1-85753-245-7.
External links
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