TECHNICAL FIELD

[0001] The present invention relates generally to aerospace and aircraft, and in particular to amphibious landing gear.

BACKGROUND

[0002] Aircraft are generally provided with landing gear, which provide means for the aircraft to land, take off and taxi. Different types of landing gear have been adapted for operations on ground, mud, snow or water, and even amphibious landing gear capable of operating on both land and water.

[0003] Commercially available amphibious landing gear, such as the products offered by Aerocet Inc. or Zenair Ltd., generally comprise a set of pontoons with a wheel located at the fore of each pontoon and another wheel located further aft on each pontoon. For land operations the wheels would generally be extended to allow the aircraft to roll around, while for water operations the wheels would generally be retracted to minimize any hydrodynamic effects. Safe operation of an amphibious aircraft relies on the pilot correctly operating the landing gear and ensuring it is in the appropriate position attempting to land on a given surface. Attempting a water landing with the wheels extended is a common, often fatal, accident with amphibious aircraft, as the extended nose wheels dig into the water surface and create a strong pitch-down moment, often inverting the aircraft. Another disadvantage of this type of landing gear is that the mechanisms for extending and retracting the wheels add significant complexity and weight to the landing gear.

[0004] Alternate landing gear arrangements have been proposed with varying degrees of success. Carden (US1866451 ) teaches an aircraft having fixed-wheel landing gear, retractable outboard inflatable pontoons, as well as central inflatable pontoons located on the fore and aft of the fuselage. As with the designs described above, this type of landing gear can be fatal if the pilot fails to ensure the gear is correctly configured for a water landing, as landing with the pontoons up would result in the nose wheels digging into the water surface, potentially inverting the aircraft. This type of design also creates significant complexity and weight with the mechanisms for extending and retracting the pontoons.

[0005] Other landing gear arrangements, such as that taught by Boyle (US2621874), use inflatable members attached to the wheeled landing gear which can be inflated or deflated depending on the surface to be landed on. While this type of design is not as complex or heavy as those previously discussed, it is still susceptible to pilot error in that the pilot must ensure the landing gear is properly configured prior to landing on water. [0006] McCarty (US2642238) teaches an aircraft with a pneumatic cushion disposed on the underside of the fuselage, with recesses to house the wheels of a retractable landing gear. The hydrodynamic performance of this type of design is suboptimal because the wheels do not completely retract and the pneumatic cushion does not provide a hydrodynamic surface. This type of design also requires the complexity of mechanically retractable wheels.

[0007] It is an object of the present invention to provide an amphibious aircraft landing gear which can be operated safely without requiring the pilot to retract the wheels. It is another object of the present invention to provide a simple, lightweight amphibious landing gear. It is another object of the present invention to provide a hydrodynamic surface for water-based operations.

SUMMARY

[0008] The present invention comprises an inflatable, amphibious landing gear. The upper portion of the landing gear comprises an inflated pontoon. One or more wheels are attached to this inflated pontoon to provide for land operations. Below the inflatable pontoon are one or more air bladders which do not extend below the lower surface of the wheels when in a deflated state, but extend below the lower surface of the wheels when fully inflated in order to provide for water operations. A hull may be attached to the lower surface of the air bladders to improve performance on water. [0009] Other aspects of the present invention are described below in relation to the accompanying drawings.

[0010] It should be noted that in the description of the present invention, the term "inflated pontoon" is intended to refer to the upper section of the landing gear in accordance with the present invention, which is usually in an inflated state, the term serving as a distinction from the term "air bladder" which is used to refer to the lower section, which alternates between an inflated and deflated state during normal operations.

BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 is a side view of the inflatable amphibious landing gear, showing the air bladders in the deflated position, according to an embodiment of the present invention.

[0012] FIG. 2 is a side view of the inflatable amphibious landing gear, showing the air bladders in the inflated position, according to an embodiment of the present invention.

[0013] FIG. 3 is a side view of an aircraft according to an embodiment of the present invention.

[0014] FIG. 4 is an isometric view of an aircraft according to an embodiment of the present invention. DETAILED DESCRIPTION

[0015] In the embodiment depicted in FIG. 1 , an inflatable amphibious landing gear

(10) comprises inflatable pontoon (1 1 ), below which is a series of deflated air bladders (20), below which in turn is a hydrodynamic hull (30). Attached to the inflatable pontoon

(1 1 ) is a set of wheels (12). FIG. 2 depicts the same inflatable amphibious landing gear, this time showing the air bladders (20) in their inflated position. [0016] In the embodiment depicted in FIG. 3 and FIG. 4, an aircraft (40) comprises an inflated wing (41 ) and two inflatable pontoons (1 1 ) according to a preferred embodiment of the present invention. The inflatable pontoons (1 1 ) may be constructed using similar materials and methods to those of the inflated wing (41 ). The inflation gas in the pontoons (1 1 ) may be in fluid communication with the inflation gas of the inflated wing (41 ), and may also share a common pressure management system. In alternate embodiments, a conventional aircraft having a non-inflated wing may be outfitted with the inflatable amphibious landing gear of the present invention.

[0017] The inflatable pontoon (1 1 ) is preferably constructed of lightweight fabric, with polymer coatings to render the fabric substantially impervious to gas and water, as well as provide protection from environmental factors like ultraviolet radiation or salt water. The inflation gas used is preferably hydrogen in order to provide a cheap source of buoyancy; helium may be used as an alternate source of buoyancy. Operations involving large changes in altitude or temperature necessitate a pressure management system to ensure the inflated pontoon (1 1 ) does not deform under low pressure, or burst under high pressure. When combined with an inflated wing (41 ), the inflated pontoon may share a common pressure management system with the wing (41 ), or may contain its own pressure management system, the design of which will be readily apparent to those skilled in the art. [0018] When landing the aircraft (40), the large, flexible, inflated pontoon (1 1 ) acts as a shock absorber. For heavy landings, the inflated pontoon (1 1 ) may be outfitted with a pressure relief valve to avoid damaging the structure, said valve being configured to vent gas from the inflated pontoon (1 1 ) either to the outside environment or to the inflated wing (41 ) of the aircraft (40), according to one embodiment of the present invention.

[0019] Attached to the inflated pontoon (1 1 ) are one or more wheels (12) for operations on land. The wheels (12) may be attached using lacing strips, which are preferably attached to load patches or double panels on the fabric of the inflated pontoon (1 1 ) in order to distribute the load better. Additional structure may be provided to secure the wheels (12) as needed for the anticipated loads. The wheels (12) may be configured in a fixed or castoring arrangement, or may be provided with steering means. The leading wheel is preferably located aft of the leading edge of the pontoon (1 1 ), for example 5% of the length of the inflated pontoon (1 1 ), so that in the event of an attempted water landing with the air bladders (20) deflated, the inflated pontoon (1 1 ) will provide sufficient buoyancy fore of the leading wheel to prevent inversion of the aircraft (40), thus providing a fail-safe in the event of pilot error.

[0020] Attached to the underside of the inflated pontoon (1 1 ) are one or more air bladders (20). In a preferred embodiment a series of smaller bladders are provided, but an alternate embodiment could provide a single, long bladder. The inflatable air bladders (20) are preferably constructed of lightweight fabric, with polymer coatings to render the fabric substantially impervious to gas and water, as well as provide protection from environmental factors like ultraviolet radiation or salt water. These air bladders (20) can be inflated or deflated by the pilot as desired in order to position their lower edges below the lower surfaces of the wheels (12). In a preferred embodiment, any power required to inflate, extend, deflate or retract the air bladders (20) is provided by solar power collected from the top of the aircraft (40), although various other power sources may be employed as will be apparent to those skilled in the art.

[0021] In the deflated position, the aircraft (40) can operate on its wheels (12) without any other part of the landing gear (1 0) contacting the ground. Furthermore, in the deflated position the lower surface of the air bladders (20) is still below the top surface of the wheels (12), which significantly reduces the adverse effects should the pilot fail to ensure the landing gear is configured for a water landing before attempting to land on water. Furthermore, the lead wheel is preferably located away from the leading edge of the inflated pontoon (1 1 ), which further prevents the likelihood of tipping the aircraft (40) when landing on water in the incorrect configuration.

[0022] A hydrodynamic hull (30) may be disposed along the underside of the air bladders (20) to improve performance on water. This hull (30) may be constructed from rigid or semi-rigid material in accordance with standard materials and methods known to those skilled in the art. Attachment of the hull (30) may be directly to the air bladders (20) using lacing strips, welding, fasteners or other means. In addition to providing a hydrodynamic surface for water operations, the flat surface provided by the hull allows for operation on snow, sand or other surfaces where wheels are not appropriate. [0023] The inflatable amphibious landing gear (10) is equipped with means for retracting the deflated air bladders (20) and the hull (30). This preferably comprises elastic members or similar means attached to either the lower surface of the air bladders (20) or directly to the hull (30), but could alternatively comprise an actuated system of rods and levers. Alternatively, a fan, blower or compressor may be used to apply a vacuum to the air bladders (20), and the air bladders (20) may be constructed so as to fold up against the inflated pontoon (1 1 ) when deflated in order to provide an aerodynamic surface.

[0024] In one embodiment of the present invention, air bladders (20) may be in fluid connection with the inflated pontoons (1 1 ) via a valve which may be controlled by the pilot. In such an embodiment, inflation may be achieved by simply opening the valve and allowing gas to flow from the inflated pontoon (1 1 ) into the air bladders (20). In another embodiment, the air bladders (20) may be provided with fans, blowers, compressors or similar means for inflating the air bladders (20) with air from the outside environment; such an embodiment has the advantage of allowing the air bladders (20) to operate at higher pressure than the inflated pontoons (1 1 ).

[0025] It is to be understood that the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a device" includes reference to one or more of such devices, i.e. that there is at least one device. The terms "comprising", "having", "including" and "containing" are to be construed as open-ended terms (i.e. , meaning "including, but not limited to,") unless otherwise noted. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of examples or exemplary language (e.g. "such as") is intended merely to better illustrate or describe embodiments of the invention and is not intended to limit the scope of the invention unless otherwise claimed.

[0026] While different embodiments have been provided in the present disclosure, it should be understood that the disclosed invention might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. Various changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.