Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane sustained
Reexamination Certificate
1998-08-28
2001-01-09
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane sustained
C244S054000, C244S055000
Reexamination Certificate
active
06170780
ABSTRACT:
The present invention relates to an aircraft having an airframe configuration, engine orientation and engine mounting that precludes the ingestion of foreign objects, for example, birds, into the aircraft's engines yet maximizes the flow of air to the engine inlets of the aircraft.
BACKGROUND OF THE INVENTION
The propulsion system of an aircraft must be capable of ingesting foreign objects without engine damage. The problem of foreign object ingestion has been solved in the past by merely increasing the strength of the engine components exposed to impact damage. However, strength can be equated with weight, which, in turn, compromises performance of the aircraft. Reconciliation of such seemingly divergent performance and safety requirements requires careful integration of the aircraft's propulsion system with airframe aerodynamics.
The basic model of air flow past an aircraft fuselage assumes that air viscosity acts over a relatively thin region, inwardly of the free or external stream, termed the boundary layer. The boundary layer exists in several states, namely, laminar, turbulent, and wake. In the laminar state, flow is stratified. Farther aft, laminar flow transforms into a turbulent state which is eddying in character. Turbulent flow subsequently transforms into a wake wherein the direction of flow may actually reverse. While careful aerodynamic design can cause the boundary layer, whether laminar or turbulent, to remain attached to the aft fuselage to a point beyond the engine air inlets, orientation of the aircraft engine in a manner that precludes ingestion of relatively heavy foreign objects, for example, birds presents a more difficult problem.
SUMMARY OF THE INVENTION
The present invention is based on the premise that relatively heavy objects tend to flow rearwardly of the aircraft outside the cylindrical surface defined by the maximum cross section of the fuselage due to their large inertia forces. Accordingly, the engines of the jet aircraft of the present invention are mounted on pylons extending from the vertical stabilizer of the aircraft with the engine air inlets positioned within a rearward projection of the maximum lateral cross section of the center section of the fuselage so that ingestion of foreign objects into the engine air inlets is precluded. Air flow to the engines is maintained by orientating the engine inlets in the external stream between boundary layer air flow and said rearward fuselage projection.
More specifically, the jet aircraft of the present invention solves the problem of foreign object ingestion by utilizing a conical aft fuselage or tail cone that, in a lateral plane containing the engine inlets, is significantly smaller in radial cross section than the maximum cross section of the main fuselage section thereby permitting the engine air inlets to be positioned within a rearward projection of said maximum fuselage cross section. Engine inlet airflow is optimized by mounting the engines on pylons in spaced relation to the vertical stabilizer so as to permit boundary layer air to pass between the vertical stabilizer and the engine air inlets.
REFERENCES:
patent: 3113636 (1963-12-01), Brown et al.
patent: 3455523 (1969-07-01), Hertel
patent: 207347 (1966-09-01), None
Barefoot Galen L.
Lyon P.C.
Williams Sam Barlow
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