AIRCRAFT AND SYSTEMS THEREFOR

Abstract

A non-rigid airship or hybrid air vehicle has a pressure-stabilised envelope (100) that includes at least one ballonet (102, 103). A system is provided for measuring the geometry of the lifting gas enclosure (101) within the pressure-stabilised envelope (100). The system comprises a plurality of sensors (104, 109) located outside the ballonet(s) but inside the envelope, for measuring the geometry of the enclosure. Some of the sensors (104) are arranged to measure an internal surface of the pressure-stabilised envelope (100), and others of the sensors (109) are arranged to measure an external surface of the at least one ballonet (102, 103).

Claims

1. A system for measuring the geometry of a lifting gas enclosure within a pressure-stabilised envelope of an aircraft, namely a non-rigid airship or hybrid air vehicle, that includes at least one ballonet, the system comprising: a plurality of sensors located outside the ballonet but inside the envelope, for measuring the geometry of the enclosure, wherein some of the sensors are arranged to measure an internal surface of the pressure-stabilised envelope, and others of the sensors are arranged to measure an external surface of the at least one ballonet.

2. A system according to claim 1, wherein the sensors are located at different positions along both longitudinal and transverse axes of the envelope.

3. A system according to claim 1, wherein said others of the sensors are located above the at least one ballonet.

4. A system according to claim 1, including a module arranged to automatically compute, from the geometry of the enclosure and pilot input data, aircraft heaviness and centre of gravity position.

5. A system according to claim 4, arranged to provide the computed aircraft heaviness and centre of gravity position to aircraft crew.

6. A system according to claim 5, arranged to use the computed aircraft heaviness and centre of gravity position to automatically operate at least one of an aircraft flight control system, an envelope pressurisation system or an undercarriage system.

7. A system according to claim 6, arranged to cease automatic operation of the aircraft flight control system, envelope pressurisation system or undercarriage system in the event that values of one or more calculation parameters cannot be determined with sufficient accuracy or reliability.

8. A system according to claim 1, wherein at least one of the sensors is arranged to quantify a 1-dimensional distance to a single point on the envelope or ballonet.

9. A system according to claim 1, wherein at least one of the sensors is arranged to quantify a 2-dimensional variation in distance along a surface curve.

10. A system according to claim 1, wherein at least one of the sensors is arranged to quantify a 3-dimensional variation in distance over a surface area.

11. A system according to claim 1, wherein the sensors are immersed in lifting gas.

12. A system according to claim 1, wherein the sensors are located inside at least one separate sealed compartment, and are arranged to operate through an aperture or window in said compartment.

13. A system according to claim 1, including a plurality of additional measurement sensors, provided to survey the shape of the envelope, including the bottom surfaces of the ballonet(s), by means of distributed contact across a surface.

14. A system according to claim 13, wherein the additional measurement sensors conform to an internal side of the aircraft's pressure-stabilised envelope.

15. A system according to claim 13, wherein the additional measurement sensors conform to an external side of the aircraft's pressure-stabilised envelope.

16. A system according to claim 1, including one or more further sensors, provided to measure at least one of purity of the envelope's lifting gas contents, inflation pressure, temperature or humidity of the envelope's lifting gas contents or ballonet air contents, ambient atmospheric pressure, aircraft air speed, aircraft attitude, aircraft acceleration, quantity and location(s) of fuel or ballast weight carried by the aircraft, ground contact forces and ground contact locations reacted by an undercarriage of the aircraft, or thrust loads imparted by the aircraft's propulsion system.

17. A system according to claim 1, arranged to utilise payload, ballast or other discrete weight data that is input by the aircraft's crew prior to aircraft take off and updated as applicable during flight.

18. A system according to claim 1, arranged to compute instantaneous data readings from the sensors.

19. A system according to claim 1, arranged to average a series of instantaneous data readings over a period of time, as provided by one or more of the sensors.

20. A system according to claim 1, wherein input data to the system is derived by taking simultaneous readings from two or more independent ones of the sensors and calculating an average value for trim computation.

21. A system according to claim 1 wherein input data to the system is derived by taking the readings from two or more independent ones of the sensors and using an algorithm to select an optimal subset of readings for trim computation.

22. A system according to claim 4, arranged to indicate, for the computed aircraft heaviness and centre of gravity information, at least one of: time history over a duration of interest, magnitude of any short term dynamic variation, accuracy or reliability.

23. (canceled)

24. (canceled)

25. A system according to claim 1, arranged to provide a warning to aircraft crew concerning at least one of: any malfunction of primary components of the hull pressure control system such as ballonet inflation fans, pressure relief valves, or sensors; any significant reduction in the quantity of lifting gas contained inside the aircraft's envelope; any significant change in ballonet air volume that is not consistent with commanded operation of the hull pressure control system in prevailing atmospheric conditions.

26. A system according to claim 1, arranged to create a record of at least one system parameter over an extended duration and to make the record available to support diagnostic or scheduled maintenance operations.

27. An airship or hybrid air vehicle including: a lifting gas enclosure defined by a pressure-stabilised envelope; at least one ballonet within the pressure-stabilised envelope; and a system comprising a plurality of sensors located outside the at least one ballonet but inside the envelope, for measuring the geometry of the enclosure, wherein some of the sensors are arranged to measure an internal surface of the pressure-stabilised envelope, and others of the sensors are arranged to measure an external surface of the at least one ballonet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the invention will now be described solely by way of example and with reference to the accompanying drawings, in which:

[0043] FIGS. 1A and 1B are schematic longitudinal and transverse sections respectively through the pressure-stabilised envelope of an aircraft according to the invention, showing a first subset of the sensors;

[0044] FIGS. 2A and 2B are further schematic longitudinal and transverse sections respectively through the envelope of FIGS. 1A and 1B, showing a second subset of the sensors;

[0045] FIG. 3A schematically shows a sensor disposed on the surface of the pressure-sensitive envelope;

[0046] FIG. 3B schematically shows a sensor located inside a sealed compartment; and

[0047] FIGS. 4A and 4B are further schematic longitudinal and transverse sections respectively through the envelope of FIGS. 1A and 1B, showing additional optional sensors.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0048] FIGS. 1A and 1B show a typical non-rigid airship or hybrid air vehicle envelope 100 of flexible material that contains a volume of buoyant lifting gas 101 and a number of air ballonets 102, 103. The volume of air inside the ballonets can be adjusted to regulate the pressure of the buoyant lifting gas, to form the flexible envelope 100 into a pressure stabilised structure.

[0049] Measurement sensors, e.g. laser, radiofrequency or sonic sensors, are installed inside the envelope, to enable the volume and geometric distribution of the lifting gas to be determined. A first subset of the measurement sensors 104 is in this example arranged around the periphery of the envelope. The areas surveyed by these sensors may exclude some regions of the envelope surface 105, or include overlapping areas 106 covered by more than one sensor.

[0050] Individual measurement sensors may determine distance to a single point in one dimension (not shown), or distance variations across a planar profile 107 in two dimensions, or distance variations over a surface 108 in three dimensions.

[0051] FIGS. 2A and 2B show a second subset of the measurement sensors 109, arranged to survey the exterior surfaces of the air ballonets, sensing through the lifting gas volume from one or more surrounding locations. These locations are advantageous in that the measurements are not subject to interference from internal folds of fabric 110 that typically form when a ballonet is operating in a partially filled state. Furthermore, this arrangement enables a single measurement sensor to encompass a ballonet's entire upper surface with any ballonet fill state, from completely full 111 to completely empty 112 (shown in phantom lines). Putting the sensors above the ballonets in the gas space results in the sensors looking down on the flat upper surface of the ballonet (with the folds of fabric effectively on the face away from the sensor) allowing a much cleaner view of the ballonet shape and hence volume.

[0052] FIG. 3A shows how one of the sensors 113 may be immersed in the lifting gas 114. FIG. 3B shows an alternative installation of a sensor, inside a separate sealed compartment 115 that incorporates an aperture or window 116 for the sensor to operate through.

[0053] FIG. 4 shows further optional subsets of the measurement sensors, arranged to survey the shape of the envelope, including the bottom surfaces of the ballonets, by means of distributed contact across a surface. Sensors 117 may be arranged in a ring as shown, and sensors may conform to the internal side 118, or the external side 119 of the aircraft's pressure-stabilised envelope at the locations of the ballonets.

[0054] The system may include any of the additional sensors, trim calculation features and warning modes described above.

[0055] The geometric measurements of the envelope surface(s) and the ballonet exterior surface(s) are used by the aircraft trim calculation system of the invention to compute the volume and centre-of-gravity position of the lifting gas contained inside the aircraft's envelope, typically to an accuracy of 1.0%, or better.

[0056] This direct measurement of lifting gas geometry improves the accuracy of the computed lifting gas mass properties by taking into account distortions in envelope shape resulting from different aircraft loading configurations, ballonet fill states and flight conditions. The invention therefore removes the potential error that is inherent in the known indirect method of measurement of hull geometry via ballonet contents.

[0057] By using both longitudinal and lateral arrays of sensors, the system of the invention establishes the cross section of the gas space at several points along the length of the hull. Whilst it might be assumed that the hull would always be circular, it should be noted that, in actual fact, the hull cross section varies depending on (a) forces imparted by aircraft structural features, (b) the weight of its gas contents and (c) external aerodynamic forces. All these have an effect on the cross sectional shape of the hull and, hence, its volume and location of the centre of helium lift. This knowledge is captured according to the invention by the sensors within the helium space.