Rolls-Royce Pegasus

Rolls-Royce Pegasus à poussée "vectorielle" raconté sur Wikipedia de langue anglaise. Merci

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The Rolls-Royce Pegasus is a [Vous devez être inscrit et connecté pour voir ce lien] engine originally designed by [Vous devez être inscrit et connecté pour voir ce lien], and now manufactured by [Vous devez être inscrit et connecté pour voir ce lien].

This engine is able to direct [Vous devez être inscrit et connecté pour voir ce lien] downwards which can then be swivelled to power a [Vous devez être inscrit et connecté pour voir ce lien] forward.

Lightly loaded, it can also manoeuvre like a [Vous devez être inscrit et connecté pour voir ce lien], vertically for takeoff and landings.

In US service, the engine is designated F402.

The unique Pegasus engine powers all versions of the [Vous devez être inscrit et connecté pour voir ce lien] of multi-role [Vous devez être inscrit et connecté pour voir ce lien].

Rolls-Royce licensed [Vous devez être inscrit et connecté pour voir ce lien] to build the Pegasus for US built versions.

However Pratt & Whitney never completed any engines, with all new build being manufactured by Rolls-Royce in Bristol, England.

The Pegasus has also been the planned engine for a number of aircraft projects, among which were the prototypes of the German [Vous devez être inscrit et connecté pour voir ce lien] VSTOL military transport project.

Background


[Vous devez être inscrit et connecté pour voir ce lien], the French aircraft designer, had the idea much earlier to use vectored thrust for vertical take-off aircraft.

This thrust came from four centrifugal compressors driven by a [Vous devez être inscrit et connecté pour voir ce lien], the exhaust from each could be directed by rotating the outlets.


[Vous devez être inscrit et connecté pour voir ce lien] planned an engine with two thrust vectors, driven by the compressor, with forward thrust from a conventional rear exhaust in his initial BE.52 design.

The BE.52 design was built around a [Vous devez être inscrit et connecté pour voir ce lien] which through a shaft drove the first three stages of a [Vous devez être inscrit et connecté pour voir ce lien] engine which had inlet and outlets separate of those of the Orpheus.

Work was overseen by Bristol Siddeley's Technical Director [Vous devez être inscrit et connecté pour voir ce lien].

The [Vous devez être inscrit et connecté pour voir ce lien] began work on the BE.53 Pegasus in 1957.


While the BE.52 was a self contained powerplant and lighter compared to Wibault's concept, the BE.52 was still complicated and heavy.

In the BE.53 the Olympus stages were fitted close to the Orpheus stage; this simplified the inlet ducting and the Olympus stages now supercharged the Orpheus improving the compression ratio.

The engine was designed in isolation for a year, then it was helped greatly by understanding what type of aircraft it was designed for.

The team received a supportive letter from [Vous devez être inscrit et connecté pour voir ce lien] of Hawker in May 1957.

Hawker were looking for a Hawker Hunter replacement. The aircraft designer, [Vous devez être inscrit et connecté pour voir ce lien], suggested having the four thrust vectors, with hot gases from the rear two.

Two thrust vectors did not provide enough lift.

The [Vous devez être inscrit et connecté pour voir ce lien], which focussed on missiles, and not aircraft, also was not good news.

The further development of the engine then proceeded in tandem with the airframe the [Vous devez être inscrit et connecté pour voir ce lien], which first flew in 1960.

The next stage of design and development was then flown in the Kestrel, of which nine were built.

This then became the Harrier combat aircraft.

The engine was partially supported financially from the [Vous devez être inscrit et connecté pour voir ce lien].

Testing and production

The flight testing and engine development received no government funding; the plane's funding came entirely from Hawker.

There was only enough thrust in the first engines to barely lift the plane off the ground.

Flight tests were conducted when the aircraft was tethered.

The first hover was achieved on 19 November 1960.

The first, and difficult, transition from static hover to conventional flight was achieved on 8 September 1961.

The RAF was not much of a convert to the VTOL idea, and described the whole project as a toy and a crowd pleaser.

The first prototype P1127 crashed at the Paris Air Show (on landing) in 1963.

Series Manufacture and Design and Development improvement to ever higher thrusts of the Pegasus was continued by Bristol engines beyond 1966, which was when Rolls Royce Ltd bought the Company.

A related engine design, the 39,500 lbf (with [Vous devez être inscrit et connecté pour voir ce lien]) [Vous devez être inscrit et connecté pour voir ce lien] for a supersonic VTOL fighter (the [Vous devez être inscrit et connecté pour voir ce lien]) was not developed to production as the aircraft project was cancelled in 1965.

To date, more than 1,200 engines have been produced and almost two million operating hours have been logged with the Harriers of the [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] and the navies of [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien], [Vous devez être inscrit et connecté pour voir ce lien] and [Vous devez être inscrit et connecté pour voir ce lien].

Design

The Pegasus vectored-thrust turbofan is a two-shaft design featuring three low pressure (LP) and eight high pressure (HP) compressor stages driven by two LP and two HP [Vous devez être inscrit et connecté pour voir ce lien] stages respectively.

Unusually the LP and HP spools rotate in opposite directions to greatly reduce the gyroscopic effects which would
otherwise hamper low speed handling.

The engine employs a simple [Vous devez être inscrit et connecté pour voir ce lien] system that uses four swivelling nozzles, giving the Harrier thrust both for lift and forward propulsion, allowing for [Vous devez être inscrit et connecté pour voir ce lien] flight.


Nozzles

The front two nozzles are fed with air from the LP compressor, the rear with hot (650 °C) jet exhaust.

The airflow split is about 60/40 front back.

It was critical that the nozzles rotate together. This was achieved by using a pair of air motors fed from the HP (high pressure) compressor, in a fail over configuration, pairs of nozzles connected with, surprisingly, motor-cycle chains.

The Pegasus was also the first turbofan engine to have the initial compressor fan, the zeroth stage, ahead of the front bearing.

This eliminated radial struts and the icing hazard they represent.


Position of the engine

The engine is mounted in the centre of the Harrier and as such it is necessary to remove the wing to change the powerplant having already sat the fuselage on trestles; the whole change took a minimum of eight hours.


Water Injection

The maximum take-off thrust available from the Pegasus engine is limited, particularly at the higher ambient temperatures, by the turbine blade temperature.

As this temperature cannot reliably be measured, the operating limits are determined by jet pipe temperature.

To enable the engine speed and hence thrust to be increased for take-off, water is sprayed into the combustion chamber and turbine to keep the blade temperature down to an acceptable level.

Water for the injection system is contained in a tank located between the bifurcated section of the rear (hot) exhaust duct.

The tank contains up to 500lb (227kg, 50 imperial gallons) of distilled water.

Water flow rate for the required turbine temperature reduction is approximately 35gpm (imperial gallons per minute) for a maximum duration of approximately 90seconds.

The quantity of water carried is sufficient for and appropriate to the particular operational role of the aircraft.

Selection of water injection engine ratings (Lift Wet/Short Lift Wet) results in a increase in the engine speed and jet pipe temperature limits beyond the respective dry (non-injected) ratings (Lift Dry/Short Lift Dry).

Upon exhausting the available water supply in the tank, the limits are reset to the 'dry' levels. A warning light in the cockpit provides advance warning of water depletion to the pilot.

Variants

Pegasus 2

Otherwise known as the BE53-3, used in the P.1127, 11,500 lbf (51 kN)


Pegasus 3

Used on the P.1127 prototypes, 13,500 lbf (60 kN)


Pegasus 5

Or BS.53-5 (Bristol-Siddeley 53-3). Used for the Hawker Siddeley Kestrel evaluation aircraft. 15,000 lbf (67 kN)


Pegasus 6 (Mark 101)

For first Harriers. 19,000 lbf (85 kN), first flown in 1966 and entered service 1969


Pegasus 10 (Mark 102)

For updating first Harriers with more power and used for the AV-8A, 20,500 lbf (91 kN), entering service in 1971.


Pegasus 11 (Mark 103)

The Pegasus 11 powered the first generation Harriers, the [Vous devez être inscrit et connecté pour voir ce lien] GR.3, the [Vous devez être inscrit et connecté pour voir ce lien] AV-8A and later the [Vous devez être inscrit et connecté pour voir ce lien].
The Pegasus 11 produced 21,000 lbf (93 kN) and entered service in 1974.


Pegasus 14 (Mark 104)

Navalised version of the Pegasus 11 for the Sea Harrier, same as the 11 but some engine components and castings made from corrosion-resistant materials.


Pegasus 11-21/Mk.105/Mk.106

The 11-21 was developed for the second generation Harriers, the USMC [Vous devez être inscrit et connecté pour voir ce lien] and the [Vous devez être inscrit et connecté pour voir ce lien].

The original model provided an extra 450 lbf (2.0 kN). The RAF Harriers entered service with the 11-21 Mk.105, the AV-8Bs with F402-RR-406.
Depending on time constraints and [Vous devez être inscrit et connecté pour voir ce lien], between 14,450 lbf (64.3 kN) (max. continuous at 91% RPM) and
21,550 lbf (95.9 kN) (15 s wet at 107% RPM) of lift is available at sea level (including splay loss at 90°).

The Mk.106 development was produced for the [Vous devez être inscrit et connecté pour voir ce lien] upgrade and generates 21,750 lbf (96.7 kN).


Pegasus 11-61/Mk.107

The 11-61 (aka -408) is the latest and most powerful version of the Pegasus, providing 23,800 lbf (106 kN).

This equates to up to 15 percent more thrust at high [Vous devez être inscrit et connecté pour voir ce lien], allowing upgraded Harriers to return to an [Vous devez être inscrit et connecté pour voir ce lien] without having to dump any unused weapons which along with the reduced maintenance reduces total cost of engine use.

This latest Pegasus has also enabled a highly effective radar equipped AV-8B+.

This version combines the proven advantages of day and night STOVL operations with an advanced [Vous devez être inscrit et connecté pour voir ce lien] system and beyond-visual-range [Vous devez être inscrit et connecté pour voir ce lien].

The RAF/RN is in the process of upgrading its GR7 fleet to GR9 standard, initially through the Joint Upgrade and Maintenance Programme (JUMP) and now through the Harrier Platform Availability Contract (HPAC).

All GR7 aircraft are expected to have been upgraded by April 2010.

Part of this process is the upgrade of the Mk.105 engines to Mk.107 standard.

These aircraft will be known as GR7As and GR9As.

Applications

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Intended application

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Engines on display


Pegasus engines are on public display at the following museums:

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