Coarse G 850

Coarse G 850 Strato 2C
Type:	High-altitude research aircraft
Design country:	BR Germany
Manufacturer:	Gross Aircraft
First flight:	March 31, 1995
Number of pieces:	1

Detail: Strato 2C by Grob

The Grob G 850 Strato 2C was a high-altitude research aircraft that Grob Aircraft AG built on behalf of DLR with funds from BMFT to explore the stratosphere. It is the largest aircraft in the world made entirely of CFRP .

history

The Strato 2C or Grob G 850 was the successor to the Grob G 520 Egrett or Strato 1 , which had also been financed with funds from the BMFT and had the same purpose. This was particularly the study of the ozone layer and the climate. The development costs were originally estimated at roughly 60 million marks. The aircraft was to be stationed at the DLR airfield in Oberpfaffenhofen from 1995 .

After two and a half years of development, the first flight in Mindelheim took place on March 31, 1995 with the former NASA test pilot Einar Enevoldson and Hans-Ludwig Meyer - chief test pilot of the DLR, and landed at Memmingen airfield due to unfavorable weather . During the last flight on August 4, 1995, a new altitude record for an airplane powered by piston engines was set with an altitude of 60,891  ft (18,561 m), surpassing the 17,083 m altitude achieved in 1938 with a Caproni Ca.161bis .

technology

Initially, the aircraft was designed for one pilot. Due to safety considerations, a second pilot was added and the emergency facilities were revised. For emergency descents from great heights, the use of a braking parachute in the stern was considered, which would have allowed a rate of descent of 35.56 m / s (7000 ft / min).

The aircraft was largely made of carbon fiber reinforced plastic . According to flight performance calculations, pressure propellers were favored, as this configuration ensures an undisturbed flow of air to the wings and more space is available for the large propellers. Two charged Teledyne Continental engines were to be used as engines .

The choice fell on gasoline engines , as these have the lowest specific air consumption compared to diesel engines and jet engines . In contrast to diesel and jet propulsion, gasoline engines consume all of the supplied oxygen with their combustion air ratio λ (lambda) equal to 1. Diesel and turbine drives work with excess air, with turbine drives usually not being able to use around 70% of the supplied oxygen, as otherwise the turbine blades would be damaged by excessively high temperatures. For a diesel engine with a comparable altitude output, the compressor, the charger and the intercooler would have had to be made significantly larger due to the higher air requirement (λ ≈ 1.4) . In addition, there is the additional weight of diesel engines due to the design. A turbine drive for the projected flight altitude would have had to be greatly reduced at lower altitudes, which would have meant the use of oversized engines and a loss in efficiency.

In order to ensure the air supply to the engines at high altitudes of up to 24 kilometers, the air was compressed both with turbochargers and with one low and one medium pressure compressor from a Pratt & Whitney PW127 turboprop engine . These compressors with their own drive turbine are used in the turboprop drives as gas generators for the free- running power turbine, which, however, is not installed in the Strato 2C, as the gas flow generated is diverted and fed to the compressors of the turbochargers, which function as the third charging stage (high-pressure compressor). The drive turbine of the low and medium pressure compressors is driven by the exhaust gases from the piston engines, which are fed into the turbine section of the PW127 after passing through the turbocharger. The compressor output is regulated by means of a bypass valve. The exhaust gas is then led out of the engine nacelle through an exhaust pipe, whereby an additional thrust of 12% of the propeller thrust can be generated by expansion at a height of 24 km. Because of the low air density at the maximum operating altitude and because of the high compression ratio of the charge air of up to 1 || 45, in addition to the drive and compressor components, the large engine nacelles also contain voluminous heat exchangers for water, oil and charge air cooling. All of these measures should enable a full pressure altitude of 24 km and a service ceiling of 26 km.

With a wing span of 56.5 meters and a very high aspect ratio , it is still the largest aircraft made entirely of CFRP. Although the machine was able to meet the required performance data in both ground and flight tests, development costs also rose rapidly, which is why the federal government finally withdrew from funding and Grob put the project on hold.

Technical specifications

Parameter	Data
crew	up to 4 people
span	56.5 m
payload	1 t
Empty mass	6.65 t
Takeoff mass	13.35 t
Max. Bet height	26 km
Service ceiling	24 km
Flight duration	48 hours at a height of 18 km, 8 hours at a height of 24 km
Range	18,000 km at an altitude of 18 km, 7,000 km at an altitude of 24 km
Engines	2 × Teledyne Continental TSIO-550 piston engines with the gas generator (compressor and turbine) of the PW127 engine, each with 300 kW (402 PS)

See also

D-CDLR

• List of aircraft types

Web links

• Homepage of GROB Aircraft SE
• Description at the flight review ( Memento from November 22, 2008 in the Internet Archive ) (en)
• At Spyfly

Individual evidence

1. ↑ Schumann, U. (1995) STRATO 2C - A New Stratospheric Research Aircraft under Development. Physics and Chemistry of the Earth, 20, pp. 103-107.
2. ↑ Record flyer should explore the atmosphere, DIE WELT, June 28, 1991
3. ↑ ^{a b c d e} Volker K. Thomalla , Strato 2C: Höhenflieger im Jumbo-Format, Flugrevue January / 1993, Vereinigte Motorverlage GmbH & Co KG, pp. 11-15
4. ↑ Largest plastic aircraft being tested . In: aerokurier . No. 6 , 1995, pp. 11 .
5. ↑ PD Stemp: Kites, Birds & Stuff - Aircraft of Germany - E to H lulu.com, 2014 ISBN 978-1-291-29268-8 , p. 332
6. ↑ ^{a b c d} Gersdorf / Grasmann / Schubert, Flugmotoren und Strahltriebwerke, Bernard & Graefe Verlag, Bonn, 3rd edition 1995 ISBN 3-7637-6107-1 , pp. 227-230

Coordinates: 48 ° 6 ′ 34.46 "  N , 10 ° 31 ′ 29.05"  E