Aeronautics and astronautics – Aircraft power plants – Mounting
Patent
1994-10-24
1997-03-11
Barefoot, Galen L.
Aeronautics and astronautics
Aircraft power plants
Mounting
B64D 2900
Patent
active
056093136
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to propulsive power units for aircraft and is particularly although not exclusively concerned with a power unit comprising a ducted fan turbine (turbofan) engine and a nacelle which houses the engine.
The function of the nacelle for a turbofan engine is generally twofold. Firstly, the nacelle must provide an air intake flow to the fan of minimal disturbance for a variety of flight conditions which include high incidence, gusts and the like. Secondly, the exterior profile of the nacelle should be such as to minimise aerodynamic drag, subject to constraints imposed by major engine components such as the accessories gearbox.
Considering the exterior profile, the skin friction component of the overall profile drag is directly affected by the discontinuities on the outer surface. While the ideal would be for a smooth, uninterrupted outer surface, this ideal is compromised in nacelles hitherto proposed by the various breaks in the outer skin which arise due to the doors and panels required to gain access to the equipment housed within.
A typical conventional nacelle is shown in FIG. 1 of the drawings, which is a schematic perspective view of an underwing pylon mounted turbofan power unit. The main structural components of the nacelle are the inlet cowl 11, the fan cowl doors 12, the thrust reverser unit 13 and the nozzle 14. The inlet cowl 11 is a single unit, comprising a leading edge lipskin structure 15, an outer main skin 16, an air intake acoustic barrel 17 which serves to attenuate engine noise, and various internal stiffening members and bulkheads. The inlet cowl 11 generally attaches, via a flange at the rear of the acoustic barrel 17, to a front flange of the engine fan case. The fan cowl doors 12 are generally hinged at the pylon 18, and are latched together at the bottom centre line. The thrust reverser unit 13 may take a variety of forms but is typically mounted on the pylon 18. The nozzle 14 may be attached in a variety of ways depending upon the exhaust philosophy adopted, i.e., mixed or separate fan stream exhaust and core exhaust. The forms which the thrust reverser and nozzle take only marginally affect the benefits derived from a propulsive power unit according to the present invention and as hereinafter to be described, as will become apparent.
Aerodynamic research has demonstrated that on such conventional nacelle structures as illustrated in FIG. 1 the gap between the inlet cowl and the fan cowl doors is a source of nacelle drag.
In addition to the fan cowl doors, various other inspection doors and removable panels (not shown) are provided in the exterior skin 16 of the inlet cowl 11 of the nacelle shown in FIG. 1 in order to gain access to equipment housed within the cowl 11. The presence of joints occurring between the main exterior cowl skin and such inspection doors and removable panels still further reduces the aerodynamic efficiency of the exterior surface of the nacelle.
It is an object of the present invention to provide an aircraft propulsion power unit in which access to equipment housed within the nacelle can be gained without the use of access panels and doors as provided in nacelles hitherto proposed.
According to the present invention there is provided an aircraft propulsive power unit comprising an engine, a nacelle structure housing the engine and having a forward nacelle portion and a rearward nacelle portion, the rearward end of the forward nacelle portion in an operational position of the forward nacelle portion adjoining the forward end of the rearward nacelle portion and the forward end of the forward nacelle portion including an intake opening leading to an intake barrel upstream of the engine for the supply of intake air to the engine characterised in that the unit includes support means to support the forward nacelle portion while permitting it to be moved on the support means from the operational position to a forward position in which it is supported by the support means forwardly of the operational position to provide access to compone
REFERENCES:
patent: 4206893 (1980-06-01), Howard
patent: 4361296 (1982-11-01), Hall et al.
PCT Search Report (copy filed w/original application) Search Report, UK App. GB 9401269.7..
"Aircraft Gas Turbine Engine Technology", 1979, McGraw-Hill Book Company Publication by Irwin E. Treager, P. 340, Fig. 18-14.
Blair Alan J.
Cole Derek
Sherry Philip D.
Barefoot Galen L.
Short Brothers PLC
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