Aeronautics and astronautics – Landing gear
Reexamination Certificate
2000-05-25
2001-11-20
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Landing gear
C244S1020SS, C244S121000
Reexamination Certificate
active
06318669
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an aircraft equipped with a landing gear designed to be able to be detached in a controlled manner, in the event of an accident. The invention particularly makes it possible to prevent the extracted landing gear from striking a fuel tank placed behind it.
The invention particularly relates to a commercial type aircraft, such as an aircraft intended for passenger and/or freight transport.
STATE OF THE RELATED ART
In commercial aircraft, the fuel tanks are generally located in the wing unit and in the lower part of the fuselage section holding the wing unit, in front of the main landing gear. This central and symmetrical position of the tanks with reference to the median longitudinal plane of the aircraft makes it possible to manage its centring easily. In other words, the position of the centre of gravity of the aircraft is only slightly modified by the decrease in the weight of the fuel that occurs as it is burned in the engines.
In order to increase the capacity and flying range of an aircraft, it may be necessary to modify it and design a new version, without, however, modifying its essential characteristics. Indeed, this makes it possible to use the highest possible number of common parts on the different versions of the same aircraft.
Consequently, a new version of an existing aircraft, characterised by an increased capacity and flying range with reference to the basic version, may be defined without the wing unit and the section holding it in place being modified. Under these conditions, the fuel tanks contained in the wing unit and in this section are not modified either, so that their capacity remains unchanged. In order to enable the aircraft to complete its new task, which implies having an additional quantity of fuel so as to increase its flying range, an additional fuel tank must then be added. An appropriate position for this additional tank is located in the lower part of the fuselage, behind the main landing gear. Indeed, this position located in a central part of the aircraft enables good management of the longitudinal position of its centre of gravity.
However, this additional fuel tank position may prove to be critical under abnormal landing or takeoff conditions.
The applicable regulations stipulate that landing gear failure and its consequences under abnormal conditions must be taken into consideration. They also require a limitation of fuel leakages. Under these conditions, it is necessary to prevent any impact between the ruptured landing gear and the walls of the fuel tank, which could result in the perforation of said tank; this involves controlling the rupture of the landing gear and the trajectory of its parts that are detached.
On aircraft, there is a comparable risk near the reactors. Indeed, behind the combustion chamber of each of the reactors, there is a turbine, with blades that are heated to very high temperatures. In the event of the rupture of a blade, it is therefore essential it never encounters on its trajectory vital components for the control of the aircraft, such as flight controls, hydraulic circuits, etc., or fuel. For fuel, the solution currently used consists of limiting the quantity of fuel present in the probable ejection cone of a blade to the lowest possible value.
However, this solution cannot be transposed in the case of a fuel tank placed behind the main landing gear of the aircraft. Indeed, for the reasons mentioned above, this position offers essential advantages determining its choice, when an additional tank is to be fitted on the aircraft.
DISCLOSURE OF THE INVENTION
The invention relates to an aircraft equipped with a landing gear, the original design of which enables its detachment to be controlled, particularly in order to eliminate any risk of impact between the detached part of the landing gear and the structure of the aircraft, under abnormal landing or takeoff conditions.
According to the invention, this result is obtained by means of an aircraft, comprising a structure and at least one landing gear fitted under the structure, the landing gear comprising a frame, a bogie, a damper equipped with a slack limit stop and a rod system placed behind the damper, the damper and the rod system connecting the bogie to the frame separately, characterised in that the structure comprises a sliding rail with which the rod system can come into contact, in the event of accidental tilting of the landing gear to the rear, to induce a complete slackening of the damper, a rupture of the slack limit stop and a rupture of the rod system successively.
In this way, in the event of an incident resulting in the tilting of the landing gear to the rear, the slack limit stop of the damper and the rod system both connecting to the bogie the frame are ruptured automatically. The two part of the damper connected to the bogie and the frame, respectively, are then separated from each other under the combined effect of the movement of the aircraft and the residual pressure in the damper, by applying a reasonable level of force to the fuselage. Consequently, the bogie is extracted automatically with no risk of impact. If a fuel tank is placed in the aircraft structure, above the sliding rail, complete destruction of the aircraft due to an explosion of the fuel leaking from the tank is thus prevented.
Preferably, the rod system comprises two arms connected end to end by a joint capable of coming into contact with the sliding rail in the event of accidental tilting of the landing gear to the rear.
In a preferred embodiment of the invention, the joint comprises a rupture control stop, capable of controlling the rupture of a part of the rod system when an angle formed between the two arms reaches a predetermined maximum value.
Depending on the case, the part capable of being ruptured may then be either one of the arms of the rod system, for which a zone is dimensioned so as to enable rupture by bending, or the joint shaft, dimensioned so as to enable rupture by shearing.
Advantageously, one of the arms of the rod system, articulated on the bogie, comprises a stop capable of coming into contact with the damper, after the rupture of the rod system.
Moreover, the sliding rail is formed, preferably, on a reinforced structural part.
In a preferred embodiment of the invention, the sliding rail comprises a first part, capable of controlling successively the rupture of the slack limit stop of the damper and the rupture of the rod system, and a second part, capable of guiding a detached part of the landing gear away from said structural part of the aircraft.
REFERENCES:
patent: 4087062 (1978-05-01), Masclet
patent: 4155522 (1979-05-01), Sealey
patent: 4392622 (1983-07-01), McClaflin
patent: 4408736 (1983-10-01), Kirschbaum et al.
patent: 5333816 (1994-08-01), Del Monte
Dazet Francis
Maurin André
Aerospatiale Airbus
Barefoot Galen L.
Burns Doane , Swecker, Mathis LLP
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