Aeronautics and astronautics – Aircraft structure – Fuselage and body construction
Reexamination Certificate
1999-02-08
2001-04-10
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Aircraft structure
Fuselage and body construction
C244S1020SS
Reexamination Certificate
active
06213428
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aircraft fore-structure that is particularly suitable for wide- and very-wide body freight aircraft.
BACKGROUND ART
At present, and as shown very schematically in
FIGS. 1 and 2
, the fore-structure of a wide body freight aircraft comprises a pressurized compartment
1
that is extended forward by a radome
2
that contains a radar chamber
3
. Inside pressurized compartment
1
a plane floor
4
supports the cockpit and the freight accommodation. One or more access doors
5
can be provided under the fuselage in the pressurized zone behind radar chamber
3
to enable ground staff to enter the section of pressurized compartment
1
located under floor
4
, in order to carry out standard maintenance operations.
In pressurized zone
5
, an unpressurized landing gear compartment
6
is provided in the fuselage to receive the fore landing gear
7
in the retracted position. The landing gear compartment
6
is separated from pressurized compartment
1
by a certain number of partitions. The partitions include two lateral partitions that are more or less vertical, a fore partition, a rear partition as well as a ceiling that is often sloped towards the bottom working from the fore to the rear when the wheels are in front of the anchoring fittings of the strut of the undercarriage in the retracted position.
Depending on the aircraft, it may be noted that designers generally aim to reduce the size of the landing gear compartment by using shapes that are more or less complex or elaborate in order to increase, among other aims, the available space in the pressurized zone. However, in all these designs the layout of the fore structure remains standard and the other problems still exist.
The standard layout of the fore structure of freight aircraft is described in FIGS. 11.4.3 and 11.4.4 (page 400) of Chun Yung Nui's “Airframe Structural Design”, which is the standard authority in the field of aeronautical structural design.
The standard layout does, however, present a certain number of drawbacks.
For instance, access to radar chamber
3
is only possible from the outside by dismantling radome
2
. This operation, that is indispensable for any maintenance, repair or test work on the radar antenna, always requires the use of screws and/or hinges to fasten radome
2
to the aircraft. In order to carry out this operation, the system for fastening the radome requires a permanent degree of play. Consequently, there are inevitable projections between the edges of radome
2
and the aircraft structure. The projections, which are significant, or at least cannot be discounted, are located in a crucial zone. This results in aerodynamic drag interference and may disturb the anemometric air vents located near the raydome.
Moreover, the access doors
5
that are used by the ground staff in order to enter the lower section of pressurized compartment
1
, give onto the exterior of the aircraft. The projections that are inevitably present between the door and the aircraft structure also cause aerodynamic drag that reduces aircraft performance.
Another drawback of the standard layout of the fore structure of aircraft is due to the shape of landing gear compartment
6
. The spaces between the surfaces of the aircraft and the lateral surfaces of the landing gear compartment are often limited and, consequently, almost unusable. However, these spaces are pressurized and require structural reinforcement parts in order to readjust to pressurization.
Finally, the standard design of landing gear compartment
6
limits the volume available, especially for the wheels and the tires of the fore landing gear
7
, and may prevent larger wheels from being mounted in the event of the aircraft being upgraded. In a very wide-body aircraft, the maximum mass of which may exceed 500 tonnes at take off, the load to which the fore landing gear is subject requires wheels and tires of measurements that are no longer compatible with a standard design landing gear compartment.
DISCLOSURE OF THE INVENTION
The aim of the invention is an aircraft fore structure, the totally original design of which enables all the problems caused by the standard design of fore structures to be resolved.
The aircraft fore structure according to the invention enables the access door that gives onto the exterior to be eliminated and also enables the number of times the raydome is dismantled to be significantly reduced, thereby limiting the dismantling operations to maintenance work required on the actual radome itself or on its surrounding structure. This leads to a marked improvement in the aerodynamic qualities of the aircraft.
The fore structure according to the invention also enables the volume available in the landing gear compartment to be adapted without difficulty to the measurements of the wheels and the tires of the fore landing gear in the event of an increase in the mass of the aircraft at takeoff.
According to the invention, these various results are achieved by means of an aircraft fore structure that comprises a pressurized compartment and a unpressurized landing gear compartment that is suitable for housing the fore landing gear in a retracted position, characterized by the fact that the unpressurized landing gear compartment constitutes a lower fore end section of said fore structure.
In other words, the landing gear compartment extends under the cockpit up to the fore point of the aircraft. The landing gear compartment is thus only separated from the pressurized compartment by a ceiling and a rear partition.
In a preferred embodiment of the invention, the landing gear compartment comprises an extension towards the rear beyond the rear partition. The fore landing gear is then hinged in said extension towards the rear such that it extends towards the front in the landing gear compartment when it is in the retracted position.
The extension towards the rear of the landing gear compartment is formed by lateral partitions that can either be more or less vertical or preferably sloped such that they meet near the top of the compartment.
The ceiling of the landing gear compartment is preferably domed downwards. This characteristic enables the ceiling to bear the difference in pressure that exists between the two surfaces without it being necessary to increase the mass of the ceiling to an unrealistic degree.
In order to provide access to the pressurized section of the compartment located behind the landing gear compartment without affecting the aerodynamic behavior of the aircraft, at least one access door is advantageously provided in the rear partition of the landing gear compartment. The access door may be more or less oval-shaped, with its main axis vertical to provide the assembly with greater structural resistance.
Improved structural resistance is also achieved by equipping the ceiling and the rear partition with stiffeners.
In order to avoid the radome being removed too often, which would lead to the problems of projection that are known in the technology of movable radomes and consequently an increase in aerodynamic drag, at least one opening to the radar chamber is advantageously projected in a fore partition that separates said chamber from the landing gear compartment.
The fore landing gear wheel or wheels are then located near the fore partition when the gear is in the retracted position.
Finally, in order to improve the safety level for ground staff operating in the landing gear compartment, a hand rail and/or anti-shatter net is advantageously provided inside said landing gear compartment.
REFERENCES:
patent: 2685420 (1954-08-01), Burnelli et al.
patent: 3335981 (1967-08-01), Pauli et al.
patent: 3653615 (1972-04-01), Spence
patent: 4228975 (1980-10-01), Sealey
Chaumel Pascal
Dazet Francis
Aerospatiale - Societe Nationale Industrielle
Burns Doane , Swecker, Mathis LLP
Swiatek Robert P.
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