Turbomeca Astafan

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The Turboméca Astafan is a single-spool, variable-pitch turbofan engine developed from the Turboméca Astazou.[ 1]:553[ 1]:932 Despite successful flight-testing, an efficient, quiet and clean design (compared to turbojets and conventional turbofans)[ 1]:554–555[ 1]:1648[ 1]:1872 and some commercial interest,[ 1]:1683 the Astafan never entered series production.[ 1]:125 The engines were only flown on the Fouga 90 prototype[ 1]:1648 and Turboméca's two test aircraft.[ 1]:33

Design

The engine combines an Astazou-derived centrifugal compressor with up to three axial compressor stages (depending on the version of the engine), driven by a common driveshaft.[ 1]:554 The fan section is composed of a unique variable-pitch fan and fixed stator blades mounted at the front of the engine.[ 1]:554 Blade pitch is varied by a hydraulic piston mounted in the fan hub, while the fan itself is powered via a reduction gear from the main driveshaft.[ 1]:554

The engine is designed to operate at a constant speed, no matter the thrust output—a characteristic permitted by the Astafan's use of precise fuel metering and fan blade pitch adjustment.[ 1]:555 To control the engine, the pilot first sets the speed lever, which adjusts fuel flow in proportion to the selected engine speed.[ 1]:554 Then the pilot moves the thrust lever (analogous to a throttle), actuating the fan pitch piston by way of a mechanical linkage and hydraulic valve, and varying the blade pitch.[ 1]:554–555 In response, the speed governor holds engine speed steady by adjusting fuel delivery to the combustor.[ 1]:555 The control system also monitors turbine temperature and adjusts blade pitch (and therefore engine load) to maintain it within the preferred range of 350 °C to 450 °C.[ 1]:1683 Additionally, the system automatically protects against excessive fuel delivery or unusual changes in blade pitch.[ 1]:555 Using the thrust lever, pilots can start an Astafan in fine pitch (for minimal resistive torque), select takeoff (coarse) pitch, feather the fan, or even reverse the fan pitch in flight (with the fan providing reverse thrust in lieu of conventional reversers).[ 1]:555

Development

Flying testbeds

Turbomeca owned two Rockwell Turbo Commander aircraft, and arranged for Miles Aircraft to modify each of them to accept two podded Astafan engines inboard of the nacelles.[ 1]:1680 The nacelles were stripped of their turboshaft engines, and converted to carry extra fuel.[ 1]:17 One of the Turbo Commanders, a model 680V-TU, originally bore the experimental registry F-WSTM, and was later redesignated F-BSTM.[ 1]:1680[ 1] The other Turbo Commander, F-BXAS, was either a 690A or B model.[ 1]:17[ 1]

Variants

Astafan I

First run as a prototype in 1969, and first flown in 1971[ 1]:25, the Astafan I was derived from the core of the Astazou XIV turboshaft.[ 1]:553 It was capable of outputting 6.072 kN (1365 lbf) of dry thrust at takeoff power, or 6.517 kN (1465 lbf) of thrust with water-methanol injection.[ 1]:553–554

Astafan II

The Astafan II line was based on the Astazou XVI turboshaft engine core with a cooled turbine, and was governed to operate at 43000 rev/min.[ 1]:554–555

Astafan II

The basic Astafan II received its French certification in August 1972.[ 1]:26 Early Astafan IIs were rated for approximately 6.984 kN (1570 lbf) dry thrust at takeoff power, or 7.495 kN (1685 lbf) with water-methanol injection.[ 1]:554

Astafan IIA

The Astafan IIA was certified in 1972.[ 1]:66 It differed from the earlier Astafan II by incorporating a new, larger-diameter fan with blades that had a greater range of motion (improving upon the marginal reverse thrust capability that existed in prior versions).[ 1]:26 Thrust output of the IIA was 6.850 kN (1540 lbf).[ 1]:66

Astafan IIB4

Two IIB4s were installed on F-BSTM (c. 1978) and used for testing and demonstration flights.[ 1]:1680 This version was rated at 7.561 kN (1700 lbf) of thrust.[ 1]:1680

Astafan IIG

The IIG was installed on the prototype of Aérospatiale's Fouga 90 jet trainer (a development of the Fouga Magister).[ 1]:1872 Using this medium-bypass version of the Astafan instead of the Turbomeca Marboré, the 90 had twice the range of the Magister (with a similar fuel load).[ 1]:1872 Installed in the Fouga 90, and operating at its maximum thrust of 6.864 kN (1543 lbf), the IIG's specific fuel consumption was 11 g/(s·kN) (0.38 lbm/(h·lbf)).[ 1]:1872 At 6000 m (20000 ft) altitude and Mach 0.5, specific fuel consumption was 20 g/(s·kN) (0.7 lbm/(h·lbf)).[ 1]:1648

The IIG included the Astafan's characteristic variable-pitch fan, installed in front of an Astazou XVI core (comprising two axial compressor stages preceding a centrifugal compressor on a common shaft).[ 1]:66 The design also included an annular reverse-flow combustor and a three-stage turbine section.[ 1]:66 The resulting configuration yielded a bypass ratio of 8.8 and a pressure ratio of 9.1.[ 1]:66

Astafan III

The Astafan III used the Astazou XVI core and a cooled turbine.[ 1]:554 The dry thrust rating at takeoff was 7.829 kN (1760 lbf), and with water-methanol injection, thrust rose to 8.429 kN (1895 lbf).[ 1]:554

Astafan IV

The Astafan IV was based upon the Astazou XX turboshaft's core, and used three axial compressor stages before the Astazou-derived centrifugal compressor.[ 1]:554 Like the Astafan II, the IV was governed at 43000 rev/min.[ 1]:555 The Astafan IV was considered for installation in the Fouga 90, as a more powerful alternative to the IIG.[ 1]:1872

Astafan IVF6

The IVF6 was tested on F-BXAS, and the engines were retained c. 1987 during that aircraft's time as a company transport.[ 1]:17 This version of the engine output 10.490 kN (2359 lbf) of thrust at takeoff power.[ 1]:17

Applications

Constructed

The Astafan was flown as a developmental engine on two aircraft types:

  • Rockwell Turbo Commander testbeds (several configurations)[ 1]:33
  • Fouga 90 (Astafan IIG; prototype built and flown)[ 1]:1648[ 1]:1872

Proposed

Despite its many developmental variants, the Astafan was never produced in commercial quantities.[ 1]:125 Proposed installations included:

Specifications (Astafan)

General characteristics

  • Type: High-bypass turbofan
  • Length:
  • Diameter:
  • Dry weight:

Components

  • Compressor: Single stage centrifugal plus three stage axial
  • Combustors: Annular chamber

Performance

See also

Related lists

References

  1. ↑ "Air-Britain : Aero Commander 680V-TU", Air-Britain Photographic Images Collection (West Sussex, UK: Air-Britain (Historians) Ltd), 2006–2009, retrieved 2009-07-19, "Aero Commander 680V-TU, F-BSTM" 
  2. ↑ Lasserre, Michel, ed. (2005-04-11), Un demi-siècle d'aéronautique en France : Les moteurs (PDF) (in French) (2005 ed.), France: Comité pour l'histoire de l'aéronautique, retrieved 2009-07-19, "En 1969, l’Astafan, formule originale, comportant une soufflante à pas variable, qui ne réussit pas à percer (échec du Fouga 90 ) et se limita à équiper deux avions bimoteurs de liaison de la société." 
  3. ↑ Stevens, James Hay (1972-04-20), "Turboméca's Astafan" (PDF), Flight International (London, UK: IPC Business Press) 101 (3293): 553–555, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-17, "The Astafan, which began bench runs in the autumn of 1969, is a completely indigenous Turboméca powerplant." 
  4. ↑ "Diamond Jubilee Salon" (PDF), Flight International (London, UK: lliffe Transport Publications) 95 (3143), 1969-06-05: 923–938, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-17, "A surprising newcomer is a 1,570 lb thrust Turbomeca Astafan made by attaching a shrouded front fan to an Astazou turboprop and changing the gearing." 
  5. ↑ "World Aero Engines" (PDF), Flight International (London, UK: IPC Business Press) 101 (3278), 1972-01-06: 16a–31, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-19 
  6. ↑ Fulton, Ken (1978-01-07), "International turbine engine directory" (PDF), Flight International (London, UK: IPC Business Press) 113 (3590): 29–70, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-19, "The 1,540 lb Astafan IIA was certificated in 1972, and the 2,350 lb Astafan IV (with Astazou XX core engine) in 1976." 
  7. ↑ Lambert, Mark (1978-11-04), "France's aerospace industry" (PDF), Flight International (London, UK: IPC Business Press) 114 (3633): 1643–1688, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-17, "Powerplant is two Turbomeca Astafan IIG giving 1,555lb take-off thrust each at a remarkable 0.364 s.f.c. At 20,000ft and Mach 0.5, s.f.c. is 0.7." 
  8. ↑ Field, Hugh (1978-11-04), "France's aerospace industry: Astafan: power for the Fouga 90" (PDF), Flight International (London, UK: IPC Business Press) 114 (3633): 1680, 1683, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-17, "Astafan is very much the personal project of "Le Patron"—M Szydlowski, co-founder in 1938, and now president, of Turboméca." 
  9. ↑ Warwick, Graham (1978-11-18), "Which jet trainer?" (PDF), Flight International (London, UK: IPC Business Press) 114 (3635): 1871–1886, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-19, "With training costs assuming ever greater importance to air forces, the Fouga 90 has a trump card in the form of the Turbomeca Astafan IIG medium-bypass turbofan. Based on the Astazou turboprop, the engine offers low noise, low emission levels and, above all, low fuel consumption." 
  10. ↑ "Fanned Commander" (PDF), Flight International (London, UK: Reed Business Publishing) 131 (4061), 1987-05-09: 17, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-19, "Heads turned at London's Gatwick Airport on April 27 with the arrival of Rockwell Commander 690B F-BXAS, Turbomeca's testbed, equipped with the manufacturer's Astafan IVF6 engines, developing 2,359 lb take-off thrust." 
  11. ↑ Fulton, Ken (1973-01-04), "Turbine Engines of the World" (PDF), Flight International (London, UK: IPC Business Press) 103 (3330): 20–37, ISSN 0015-3710, OCLC 6674288, retrieved 2009-07-28, "Geared single-shaft turbofan. A private-venture development of the Astazou with a geared v-p fan, the 1,565 lb Astafan II flew in a modified North American Rockwell Aero Commander, which received French certification in August last year." 
  12. ↑ Faber, Manfred (1983), "Photo Private Rockwell 690A Turbo Commander F-BXAS", Planepictures.net website (Gelsenkirchen, Germany: Planepictures.net), retrieved 2009-07-19, "F-BXAS c/n 11240. Built in 1975. With jet engines!" 
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