Aeronautics and astronautics – Aircraft propulsion and steering on land or water
Patent
1998-08-13
2000-02-29
Barefoot, Galen L.
Aeronautics and astronautics
Aircraft propulsion and steering on land or water
180140, 180152, 280 241, B64C 2550
Patent
active
060299312
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION 1. TECHNICAL FIELD
The invention relates to a truck-equipped landing gear element having mechanically swivelling axles for an aircraft.
The invention is more particularly directed at an element of a tail landing gear, which can equip a wide-body aircraft having a swivelling, nose gear, an underwing gear and a tail gear installed under the fuselage. 2. Prior Art
On most existing airliners, the landing gear comprises a swivelling, nose gear and a non-swivelling, underwing gear formed from two elements generally placed beneath the wings when the gear is extended. When an aircraft equipped with a landing gear of this type is on the ground, it turns about an instantaneous rotation center permanently located on the axis of the underwing gear.
On the largest aircraft, the very high load supported by the landing gear, particularly at the instant when the aircraft touches the ground, leads to an increase in the number of wheels by adding to the non-swivelling, underwing gear a tail gear formed by two elements installed beneath the fuselage. So as not to unduly increase the turning radius of the aircraft on the ground and so as to avoid accelerated wear to the tires, the trucks forming each of the elements of the tail gear are then rendered swivellable under certain conditions. These conditions impose that the aircraft is on the ground, that the speed of the wheels is low (e.g. below approximately 28 km/h), but not zero and that the turning angle of the nose gear exceeds a certain limit (e.g. approximately 20.degree.).
In this type of landing gear, which is in particular found on the Boeing 747, the orientation of the trucks forming the tail gear located beneath the fuselage, is hydraulically controlled by jacks or rams, in accordance with values proportional to the turning angle of the nose gear, so that the axes of each of the swivelling trucks, as well as the axis of the nose gear are concurrent at the same point, located on the axis of the underwing gear, said point forming the instantaneous rotation center.
As a result of this arrangement, the turning radius is reduced, which enables the aircraft to turn more efficiently. Moreover, the orientation of the trucks of the tail gear placed beneath the fuselage makes it possible to reduce skidding of the tires and consequently wear thereto.
However, this known procedure does not completely eliminate the skidding of the tires of the tail gear placed beneath the fuselage, particularly when each element of said train has more than two axles. The wear to the tires is reduced, but still persists.
DESCRIPTION OF THE INVENTION
The invention specifically relates to a swivelling landing gear element incorporating a mechanism, by means of which the orientation of the truck is accompanied by a simultaneous orientation of the front and rear axles of each of the elements of said gear, so that the aircraft can make a close turn and the skidding of the tires, leading to premature wear thereto, is avoided.
For this purpose, the present invention proposes an element of an aircraft landing gear, comprising a truck having at least two axles and means for pivoting said truck about a central axis, oriented substantially vertically when the aircraft is on the ground, characterized in that the truck has a front axle and a rear axle able to respectively pivot about a front axis and a rear axis, parallel to the central axis and positioned symmetrically on either side of said central axis, a pivoting control means acting mechanically on each of the front and rear axles, so that the pivoting of the truck about the central axis has as simultaneous effects a pivoting in the opposite direction of the front axle and a pivoting in said same direction of the rear axle, respectively about the front and rear axes.
Preferably, the pivoting control means is designed in such a way that the pivoting of the front and rear axles has the same amplitude, less than that of the pivoting of the truck about the central axis.
In a preferred embodiment of the invention, the pivoting control means is
REFERENCES:
patent: 2538388 (1951-01-01), Sievers
patent: 2630285 (1953-03-01), Geisse
patent: 3643898 (1972-02-01), Whitener et al.
patent: 5242131 (1993-09-01), Watts
patent: 5513821 (1996-05-01), Ralph
patent: 5947414 (1999-09-01), Ralph
Encarthe Philippe
Hemadou Benoit
Menel Claude
Aerospatiale - Societe Nationale Industrielle
Barefoot Galen L.
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