For aircraft with retractable landing gear, such as commercial passenger aircraft, it is generally considered desirable to protect the various elements of the landing gear from damage caused by impact from foreign bodies. Such impacts may occur when the landing gear is deployed, or extended, during take-off and landing and whilst the aircraft is on the ground. Typically, the foreign body is either debris thrown from the ground or, in the event of a tyre failure, debris from the tyre itself by the wheels during take-off or landing, or is another airborne object, such as a bird.

Whilst it is known to provide fairings to protect some elements of the landing gear, such as illustrated in European Patent EP2509863B1, such fairings are relatively bulky and generally require additional space in the landing gear bay to accommodate the fairings when the landing gear is stowed. This is undesirable from the aircraft manufacturers perspective, who wish to minimise the size and/or space envelope of the landing gear bay to maximise cargo and/or passenger capacity of the aircraft, or minimise aircraft weight.

According to a first aspect there is described an aircraft landing gear including an impact shield for protecting a desired area from debris impact, the shield being pivotably connected to a first element of the landing gear and configured to be moveable between first and second positions, wherein in the first position the impact shield is configured to deflect incident debris away from the desired area, the impact shield being arranged to be in the first position when the landing gear is deployed/extended irrespective of the loading on the landing gear, and wherein the impact shield is arranged to be in the second position when the landing gear is stowed/retracted within the landing gear bay.

By providing a moveable impact shield the shield can be configured to provide the desired impact protection when the landing gear is deployed, yet also minimise the space required in the landing gear bay when the landing gear is stowed. The shield is arranged to be in the first (protective) position whenever the gear is deployed and independently of whether the gear is loaded or not, i.e. irrespective of whether the aircraft is on the ground or not, thereby ensuring that the shield provides protection during both ground manoeuvres and whilst the aircraft is in the air during take-off and landing manoeuvres.

The impact shield may include a first surface arranged to be in contact with a portion of the first element of the landing gear when the impact shield is in the first position, the first surface having a profile configured to match the profile of the portion of the first element of the landing gear. In this manner the majority of the energy imparted to the impact shield if it is struck by some debris is reacted directly into the first element of the landing gear rather than the shield itself, thereby reducing the necessary size and/or mass of the shield.

The impact shield may comprise a material configured to have a first stiffness in a first direction and a second stiffness lower than the first stiffness in a second direction. This arrangement allows sufficient stiffness to withstand impact from debris (first direction), whilst providing reduced stiffness in a second direction that will allow the shield to deform in the event of a malfunction causing the shield to impact with the landing gear bay on gear retraction.

The material may comprise a honeycombed material arranged to have a honeycomb pattern normal to the first direction or may comprise machined aluminium. The material may also comprise a composite structure.

The first element of the landing gear may be pivotably connected to a second element of the landing gear (such that the two elements may move relative to each other as the landing gear is stowed/ retracted), in which case the landing gear may further comprise a linkage mechanism connected between the second and third elements of the landing gear, the linkage mechanism being arranged to pivot the impact shield between the first position and the second position as the landing gear is stowed/ retracted. This provides a mechanical mechanism for moving the impact shield between the first and second positions as the landing gear is retracted/stowed.

Alternatively, the aircraft landing gear may include an actuator coupled to the impact shield and arranged to pivot the impact shield between the first position and the second position. This provides an alternative means for moving the impact shield between the first and second positions as the landing gear is retracted/stowed. Alternatively, the impact shield may be biased towards to first position and the impact shield includes a ramp/roller element arranged to contact with a corresponding statically located ramp/roller element as the landing gear is retracted and to urge the impact shield towards the second position. For example, the corresponding ramp/roller element may be located in a fixed position with the landing gear bay. This provides a further alternative mechanism having no moving parts for moving the impact shield between the first and second positions as the landing gear is retracted/stowed.

The first element of the landing gear may comprise a lower side stay.

According to a second aspect there is described an aircraft including a landing gear according to the first aspect.

According to another aspect there is described an aircraft landing gear including an impact shield for protecting a first element of the landing gear from debris impact, the shield being pivotably connected to a second element of the landing gear different from the first element and configured to be moveable between first and second positions, wherein in the first position the impact shield is configured to deflect incident debris away from the first element of the landing gear, the impact shield being arranged to be in the first position when the landing gear is deployed, and wherein the impact shield is arranged to be in the second position when the landing gear is stowed.

Brief Description of the Drawings

Figure 1 illustrates a typical passenger aircraft;

Figure 2 illustrates an example arrangement of elements for a main landing gear;

Figure 3 illustrates an impact shield in a first position when the landing gear is deployed; and

Figure 4 illustrates the impact shield shown in Figure 3 in a second position when the landing gear is stowed.

Detailed Description

Figure 1 schematically illustrates a typical passenger aircraft 2. The aircraft is illustrated with the landing gear in the extended, or deployed, position as it would be during landing and take-off and whilst the aircraft is on the ground. The landing gear includes a nose landing gear 4 and pair of wing mounted main landing gears 6. When the landing gear is deployed there is a risk of it or other areas of the aircraft being struck by flying objects, such as birds, other objects thrown up from the ground by the wheels of the landing gear, or in the case of a tyre failure parts of the tyre itself. Throughout this document such flying objects will simply be referred to as 'debris'. The impact of such debris on the various elements of the landing gear or aircraft can cause damage to those elements and it is therefore desirable to provide some protection against such debris impact to at least the most vulnerable and/or critical elements of the landing gear or areas of the aircraft.

Figure 2 schematically illustrates an example of the particular arrangement of elements for a main landing gear. In figure 2 the left-hand main landing gear is illustrated as viewed looking from the front of the aircraft towards the rear. The main landing gear 6 includes a telescopic support strut 8 that is pivotably coupled at its upper end to the wing of the aircraft. An axle is located at the lower end of the support strut 8 on which a pair of wheels 10 are mounted. Coupled between the wing and the upper end of the support strut 8 is a retraction actuator 12 that is used to pivot the support strut so as to move the entire landing gear 6 between the deployed and stowed (fully retracted) positions. A side stay 14 is connected between the support strut 8 and the aircraft wing. The side stay 14 comprises an upper side stay element 16 and a lower side stay element 18 that are pivotable coupled together. The upper side stay element 16 is pivotably coupled to the aircraft wing and the lower side stay element 18 is pivotably coupled to a lower portion of the support strut 8. By virtue of this arrangement the side stay 14 is able to fold when the landing gear is retracted. When the landing gear is deployed the side stay 14 provides additional support to the telescopic support strut 8 to react and/or absorb some of the forces incurred during landing and take-off and to help ensure the support strut remains fully deployed. To ensure the side stay 14 remains in position when the landing gear is deployed a pair of lock links 20 are pivotably coupled between the side stay 14 and an upper portion of the support strut 8. The lock links ensure that that the side stay 14 is locked into position when the landing gear is deployed. The lock links 20 are pivotably coupled to one another to allow the lock links to fold when the landing gear is stowed. An unlock actuator 22 is coupled to the lock links to unlock the lock links to allow them to fold during retraction of the landing gear. The unlock actuator 22 and the lock links 20, and in particular the joint coupling the lock links together, are vulnerable to being damaged by debris impact. By virtue of the function of the lock links, any such damage can result in the lock links and therefore the landing gear as a whole being placed in an unsafe configuration.

One possible approach to mitigating the risk of debris impact on the lock links and/or unlock actuator is to attach an impact shield to another element of the landing gear, such as the lower side stay 18, such that the shield is located in the likely trajectory of any debris thrown off from the wheels. The shield functions to deflect the debris away from the lock link assembly or absorb some of the debris' energy. However, such a shield of the requisite size and shape may not fit within the space envelope of the aircraft landing gear bay when the landing gear is stowed. To enlarge the landing gear bay simply to accommodate the impact shield is undesirable from the aircraft manufacturer's perspective. Equally, an impact shield designed to fit within the landing gear bay when the gear is stowed may not provide the desired impact protection.

Figures 3 and 4 illustrates an impact shield arrangement that aims to mitigate the above space constraint issues. In figure 3 only the lower side stay 18 and a portion of the support strut 8 are shown for the purposes of clarity. Attached to the lower side stay is an impact shield 24 that is shaped and sized to provide impact protection to the lock links and/or unlock actuator. The impact shield 24 is attached to the lower side stay 18 by a pair of hinge lugs 26 such that the impact shield can hinge, or pivot, about an axis extending between the hinge lugs 26. In figure 3 the impact shield is illustrated in a first position in which the shield provides impact protection to the lock links and/or unlock actuator, the landing gear being configured such that the impact shield is in the first position when the landing gear is deployed (regardless of the aircraft being on the ground or not). Figure 4 illustrates the impact shield in a second position in which the shield has been pivoted about the axis between the hinge lugs 26. The landing gear is configured such that the impact shield is moved between the first and second positions as the landing gear is retracted and stowed away, the impact shield being in the second position, as illustrated in figure 4, when the gear is fully retracted and stowed in the landing gear bay. In figure 4 only the lower side stay 18 and upper side stayl6 in their folded positions are illustrated for clarity. In the particular arrangement shown in figures 3 and 4 a mechanical linkage mechanism 28 is provided to move the impact shield between the first and second positions as the landing gear is stowed and deployed. The linkage mechanism includes a first elongate crank arm 30 that at one end is pivotably attached to a cardan joint 31 that couples the lower side stay 18 to the support strut 8. The other end of the first crank arm 30 is pivotably attached to a second crank arm 32, which in turn is pivotably attached to the lower side stay 18. A third crank arm 34 is pivotably attached at one end to the second crank arm and at an opposite end is pivotably attached to the impact shield 24. In the transition of the landing gear between the deployed state and the stowed state the lower side stay 18 rotates relative to the cardan joint 31. Consequently, the first crank arm 30 of the linkage mechanism 28 is linearly translated relative to the side stay. The linear translation of the first crank arm is converted by the arrangement of the second and third crank arms to a rotation of the impact shield 24 about the axis defined by the hinge lugs 26. The length of one or more of the crank arms may be adjustable, for example via turnbuckles, to allow the kinematics of the linkage to be set and/or adjusted.

It will of course be understood that the particular linkage mechanism illustrated in figures 3 and 4 is only one example of many possible linkage mechanisms and that the number and arrangement of elements within the linkage mechanism will vary depending on the particular landing gear arrangement and the location of the impact shield on the landing gear. The primary required functionality of the linkage mechanism is simply to move the impact shield between the first and second positions as the landing gear is moved between the deployed and stowed positions.

In alternative arrangements one or more actuators can be used to move the impact shield between the first and second positions, the actuators' operation being controlled by one or more sensors and/or micro-switches. Possible actuators include hydraulic actuators, electro-mechanical actuators (EMA), or electro-hydraulic actuators (EHA).

In a further alternative arrangement the impact shield may be biased into the first position (as illustrated in Figure 3), for example by means of one or more hinge springs. With such an arrangement a roller is provided at a suitable location within the landing gear bay and a cam profile (ramp) formed on the impact shield such that as the landing gear is retracted the cam profile on the impact shield comes into contact with the roller and causes the shield to be pushed into the second position. When the gear is deployed the biasing means causes the shield to return to the first position. Depending on the landing gear arrangement and geometry the roller may be located on an element of the landing gear itself rather than in the landing gear bay. The roller and cam profile may also be interchangeable.

In some arrangements it may be desirable for the impact shield to be configured such that, in the event of a failure of the mechanism used to move the impact shield between the first and second positions as the landing gear is stowed, the impact shield can deform or be crushed against the interior of the landing gear bay rather than the impact shield causing significant damage to the landing gear bay or landing gear itself. This may be achieved by forming the impact shield from a structure that is stiff in the main direction defined by the likely debris trajectory and less stiff in the direction that would be created by the impact of the shield in the bay in case of a mechanism failure, such that the shield would be crushed against the bay structure and equipment without generating a hazardous or catastrophic event. For example, the shield may be formed from a honeycombed structure, with the honeycomb pattern being substantially normal to the debris impact direction. If the impact in the bay in the event of failure is in the range of approximately 30-45° or more from the debris impact direction, the honeycomb structure will not be very resistant and is likely to deform and/or be crushed.

In the event of some debris striking the impact shield it is highly likely that the debris will have high energy and the impact shield should therefore be able to react (redirect) and/or absorb some of this energy. Whilst one possibility is to react the impact energy from the impact shield to the remainder of the landing gear through the linkage mechanism, or actuator, used to move the shield between its two defined positions this is not desirable as it requires the linkage mechanism, or actuator, to be larger and heavier than otherwise required. A more preferable solution, as illustrated in Figures 3 and 4, is to react the impact load into the lower side stay profile and through the hinge lugs 26. In this way the linkage mechanism, or actuator, would only see air loads during retraction of the landing gear. To achieve this the surface of the impact shield that is in contact with the lower side stay has a profile that matches that of the portion of the lower side stay where the contact occurs. Furthermore, the impact shield should preferably be 'pushed' against the contact area on the side stay. This can be accomplished by configuring the linkage mechanism (or actuator) to provide the desired level of preload to the impact shield when the shield is in the first position, i.e. in contact with the side stay. To ensure that structural integrity of the side stay is not affected by the preload a protective pad may be used. This is helps to avoid any gaps between the shield and the side stay which would direct more loading to the mechanism and create some free-play and unwanted vibrations.

The impact shield may additionally have one or more noise reduction features. Such features may include portions of the shield having a geometry designed to reduce the tendency for the shield to cause turbulence in the incident airflow. The noise reduction features may also include portions of the shield that are perforated to allow some airflow through the shield, thereby also reducing turbulence on the incident airflow.

The above description and accompanying figures illustrate particular embodiments of the invention. However, in other embodiments the impact shield may be provided to protect different elements of the landing gear or protect different parts of the aircraft to which the landing gear is fitted. For example, it may be desirable to provide protection for certain structures or fittings located within the landing gear bay. In general, the impact shield is provided to protect any desired area of the aircraft. In other embodiments the impact shield may therefore be attached to elements of the landing gear other than the lower side stay.

The arrangements of an impact shield described above therefore provide possible solutions to the problem of providing the desired impact protection when the landing gear is deployed, yet also minimising the space required in the landing gear bay when the landing gear is stowed.