GB2372975A

GB2372975A - Integrated fuel tank and chassis of a foot launched powered aircraft which cradles a pilots torso

Info

Publication number: GB2372975A
Application number: GB0130657A
Authority: GB
Inventors: Paul Anthony Taylor
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-11-25
Filing date: 2001-11-21
Publication date: 2002-09-11
Also published as: GB0130657D0; GB0028771D0

Abstract

A foot launched, powered aircraft for use with a canopy has a high strength pressurised tubular structure (fig 2), providing an integrated fuel tank and chassis, which assists in dampening engine vibration; provides additional fuel or oil reserves and minimises fluctuations in the centre of gravity, experienced when fuel is drained from a separate fuel container. The chassis cradles a pilots torso to correctly position the thrust line during take-off, on landing and in-flight, while the pressurised chassis assists in the pilots monitoring of the units structural integrity during pre-flight tests. Engine mountings are positioned to minimise tri-axial vibration to the pilot and the attachment of a propeller protective cage is linked directly to the engine mounting, rather than to the chassis, provides synchronicity of movement between the engine and the cage thereby reducing the risk of the propeller striking the cage when impacting the ground. A solar-trickle charging unit and in-flight recharging system is also attached (Fig 6).

Description

Foot Launched Powered Aircraft a) Background The applicant has designed the following devices for use as a"Foot Launched Powered Aircraft" ('FLPA'), and for the secondary use of inflation of hot air balloons Most available FLPA flying systems and hot air balloon inflators use a common basic format. Namely a tubular cage or moulded fibreglass chassis or carbon chassis as a means to join together an engine, carburettor, exhaust system, fuel tank, essential electrics, protective cage and propeller. (Plus harness and canopy when used for FLPA use). The system can be used without harness and canopy for inflation of hot air balloons.

The applicant has engineered a new design which reduces the component count and manufacturing time, reduces transmitted vibration, increases the structural integrity whilst reducing the weight of the unit, assists in countering adverse centre of gravity effects and actively assists the pilot in maintaining a correct thrust line both on the ground and in-flight.

FLPA machines are flown with a canopy and harness which is not illustrated in the diagrams Problems with current designs Existing design characteristics result in all or some of the following problems occurring: - Component count. As a result of the manufacturing materials and methods used, component weight and the number of individual components used for the engine, chassis, fuel tanks, exhaust system, propeller housing and harness attachments, the component count and manufacturing time is greater than necessary.

- Centre of Gravity (i). Up to 10 litres of fuel, is carried in plastic tanks or bottles attached to a chassis. As fuel is consumed in flight, the centre of gravity of the flying system changes. A rapid centre of gravity change may adversely affect flight characteristics when encountering turbulence or thermal activity.

- Centre of gravity (ii). Directional changes in flight move the fuel in the fuel tank (s).

Rapid changes of direction can cause "sloshing" rapidly changing the centre of gravity."Sloshing"can cause a pendulum effect if the fuel tank is located at the lowest point of the chassis, and reduce the stability during the running phase of take off.

- Metal fatigue (i). The fuel tank is commonly mounted below the engine and attached to the lowest point on the chassis. The pendulum effect of a full fuel tank attached to the chassis at the lower extent of the chassis can cause unacceptable loading in turns, which may produce metal fatigue and subsequent chassis fatigue.

- Metal fatigue (ii). Pre-flight checks require the pilot to visually inspect the unit prior to each flight. Because of the way the chassis, engine and other components are configured it may be difficult to thoroughly check all parts of the chassis. Failure to identify points that are beginning to develop fatigue or stress fractures will impact on the structural integrity of the unit.

- Propeller strike. Traditional designs attach the protective propeller cage to the chassis and use rubber mountings to attach the engine to the chassis. As the engine unit is independently mounted-any engine movement may cause a reduction in the amount of clearance between the propeller and the protective cage. In addition, as most rubber engine mountings are free to oscillate in all directions there is a possibility that they will allow the engine and propeller to collide with the protective cage.

Problems, or damage to the propeller and or cage, may occur in the following circumstances: o on take-off or landing ; when the cage touches the ground or the canopy lines. o following impact of the cage with the ground or other object, resulting in the propellers contacting the cage and being damaged or shattering. o if the engine mountings are fatigued or overloaded the engine unit may move resulting in the propellers impacting the chassis or protective cage. o when the engine moves under acceleration on the rubber mountings the force may move the propellers out of alignment resulting in impact with the cage or chassis.

Charging Systems. Electric starting is used on most systems, however no charging circuit is included. Batteries which are attached to the flying system and used in the electric start need to be removed and recharged, limiting the number of restarts and ultimately the amount of flying time. The pilot is required either to resort to manual pull-start, carry spare batteries or stop and recharge the batteries. (Fig. 6) The proposed design incorporates solar trickle charging in addition to in-flight recharging systems attached to the engine. c) How the new design addresses these problems The new designs have the following features to differentiate them from all others currently available on the market.

- Weight and component count. Use of lighter/stronger materials in manufacture.

The primary material used in the manufacture of the chassis is large bore aluminium tube with 1 mm walls. This may also be produced using a stamped aluminium chassis or hand laid fibreglass or carbon tank/chassis. The complete chassis/fuel tank assembly is in 2 to 4 parts. This method of manufacture provides high strength and reduces the number of individual components by including the fuel tank as an integral part of the chassis: The fuel tank is the chassis. Being an all welded or glued construction-there are no fasteners to fall off and strike the propeller in flight. (Fig 1) - Metal Fatigue The ability to pressurise the chassis and integral fuel tank provides an early and accurate indicator of potential stress fractures and metal fatigue enabling the pilot to take appropriate action to repair/strengthen the unit. As well as potentially minimising costs this also adds to the inherent safety of the unit (Fig 1) - Centre of gravity (I). Up to 10 litres of Fuel, is carried in the tubular chassis, this restricts lateral movement. In flight, the centre of gravity changes less as fuel is consumed. A gradual C of G change is encountered. As fuel is unable to slosh from side to side in the tubular fuel chambers. (Fig 2) - Centre of gravity (ii). The new design ensures correct positioning of the unit on the pilots body ensuring the ideal thrust angle and in-flight characteristics by contact with the pilots body at the shoulders, back and thighs. When the pilot is standing the lower thrust bar maintains the correct thrust angle for take off. In flight the lower thrust bar is located beneath the pilot and again serves to provide the correct thrust angle for flight. This negates the C of G changes, which occur during take off. (Fig. 3 & Fig) - Fuel Tank/Chassis fatigue. The large equally stressed fuel chamber prevents fuel

from rapidly"sloshing"or acting as a pendulum and prevents localised stresses in the chassis/fuel tank members. (Fig 4) - Chassis/Tank reduces vibration. The fuel in the fuel tanks/chassis acts as a vibration dampener and reduces the harmonic vibration in the chassis. The shape and strengthening sections of the chassis cancels out harmonic vibration in the frequency of 80-12000Hz - Propeller Strike. The protective cage is mounted directly to the engine plate and not to the isolated chassis. When the engine moves under load, the protective cage moves in synchronicity with the engine and propeller at all times maintaining appropriate clearance from the prop at all times. (Fig. 5) - Charging Systems. The new design incorporates solar trickle charging system (1.2A 12V solar panel with voltage regulator) in addition to an in flight recharging (induction coil, voltage regulator and rectifier) system. (Fig. 6) - Engine Mountings. The engine mountings are designed and placed to absorb tri-axial movement and vibration transfer to the chassis up to thrust levels of 35Kg. Beyond 35Kg, the engine mountings contact a secondary plate and become stiffer allowing single axis movement of the engine only, whilst still dampening combustion vibration transmitted to the pilot. The engine mountings in the single axis position ensure correct alignment of the thrust pattern on take off and prevention of the protective cage from movement under heavy loads as experienced during take off or turbulence. (Fig. 7) d) Essential Features of the Design - Weight and Component Count. The chassis is comprised of a pressurised large bore aluminium tube with 1 mm walls that incorporates an integral Fuel Tank. As the chassis is welded or glued it uses fewer components thereby reducing manufacturing time, weight and the risk of parts falling off and striking the propeller in flight. (Fig 1) - Centre of Gravity (i). By using tubular structure as the fuel container the liquid is unable to slosh from side to side as in traditional fuel tanks i. e. the tubular design restricts lateral movement of liquids. (Fig 1) - Centre of Gravity (ii). The new design ensures correct positioning of the equipment on the pilots body during take off, landing and in flight (Fig. 3 & 4) - Chassis/Tank Fatigue The large equally stressed fuel chamber prevents fuel from rapidly"sloshing"or acting as a pendulum and prevents localise stresses in the chassis/fuel tank members. (Fig. 1) - Monitoring for Metal Fatigue as the chassis is pressurised prior to each flight as part of the pre-flight checks, the pilot is able to quickly identify any weaknesses in the structure and take action to remedy any defects.

- Reduced Vibration The fuel in the fuel tank/chassis acts as a vibration dampener and reduces the harmonic vibration in the chassis. The shape and strengthening sections of the chassis cancels out harmonic vibration in the frequency of 80 12000Hz - Propeller Strike. The protective cage is mounted directly onto the engine plate and not the chassis enabling synchronicity in movement between the two components and maintaining clearance from the prop at all times. (Fig. 5) - Charging Systems. Solar panels are attached to provide additional power and assist with the charge of the auxiliary power outlets and the battery recharging.

Auxiliary outputs connect to onboard battery and a re-charger is attached to the Battery, GPS, Cell phone and Communications radio and any other electronic instruments to recharge continuously. Recharging system incorporates: induction coil, voltage regulator and rectifier. (Fig. 6) - Engine Mountings. The engine mountings and positioning allow flexibility until thrust of 35Kg is achieved. At this point the mountings lock against a secondary plate under full power maintaining the correct angle of thrust. The secondary plate allows single axis movement until the complete compression of the secondary damper (Fig 7).

Other Features - Cradle Design. The chassis is designed to cradle the pilot providing greater comfort in flight and additional protection for the lumber/lower back regions in the case of emergency landings. In addition, this design actively assists in the correct positioning of the engine to achieve the correct line of thrust (Fig 2) both in flight and during take-off and landing. e) Introduction to the drawings Figure 1 Weight & Component count. The illustration shows the pressurized tubular chassis structure and integrated fuel tank.

The design combines the chassis and fuel tank to reduce the weight and component count of the flying system. The pressure valve is shown at the top of the structure (12).

Figure 2 Shows the chassis with integrated fuel tank in profile.

Both Figs 1 & 2 illustrate the basic design without the harness, engine, propellers etc.

Figure 3 illustrates how the cradle shape of the chassis optimises 3 key contact points with pilot's body (1,2 & 3) thereby ensuring correct thrust angle (90 degrees to pilots body) for take off and landing. The harness, which is worn by the pilot and connects to the chassis and canopy, is not shown for purposes of clarity Figure 4 Shows contact point (1,2 & 3) with pilot's body. The shape forces the pilot into the seat and thus seated, ensures the correct thrust angle (90 degrees to pilots body) for cruising in flight.

Figure 5 Engine positioning with new design. Showing chassis/tank (4), engine position (5) propeller (6), protective cage (7) engine mounting plate (8) and mounts (8a)-protective cage mounting points (8b). The harness, which is worn by the pilot and connects to the chassis and canopy, is not shown for purposes of clarity Figure 6 Charging Systems. Showing solar power (9) and coil based charging systems in use on the FLPA device Figure 7 Engine Plate and Mountings showing unloaded positioning (10) Figure 8 Engine plate and Mountings showing how movement is restricted by the second plate and mountings under load (11).

Claims

The Claims 1. A lightweight elliptical structure made from large bore tubular components (capable of pressurisation as an option) which cradles the torso and onto which can be mounted, an engine, cage, propeller and a harness with a canopy, to create a Foot Launched Powered Aircraft (FLPA).
2. A tubular structure capable of pressurisation as in Claim 1 which is used as a fuel or oil reservoir
3. A tubular structure capable of pressurisation as in Claim 1 and 2 which when containing liquid is used to provide additional dampening of engine vibration
4. A tubular structure as claimed in Claim 1 which utilises the cradle shape to optimise the thrust line of the engine during take off, landing and in-flight
5. A tubular structure as claimed in Claim 1 and 2 whereby the elliptical shape and re-enforcing sections to the rear provide a mechanism to cancel out harmonic vibration in the frequency of 80-12000Hz
6. A tubular structure as described in Claim 1 and 2 which, when pressurised and the structure examined, will expose any structural faults prior to metal fatigue
7. A tubular structure as described in any preceding claim that incorporates a solar trickle charging system (1.2A 12V solar panel with voltage regulator) and in-flight recharging (induction coil, voltage regulator and rectifier) systems.
8. A tubular structure as described in the preceding claims onto which the engine is mounted by positioning the fixing points horizontally and vertically against the structure to restrict tri-axial movement and secondary vibrations to the Pilot and transfer the residual resonations to the liquid contained in the tubular structure
9. A tubular structure as claimed in Claim 1 to which plates are attached and onto which the engine is mounted limiting engine movement and optimising the thrust line
10. The attachment of the protective cage as claimed in Claim 1, directly to the engine plate to provide synchronicity between the cage and the engine (propellers)
11. A tubular structure as claimed in any proceeding claim which is made from metal, plastics or composites or any combination of these materials