WO1993001977A1

WO1993001977A1 - In-flight aircraft monitoring system

Info

Publication number: WO1993001977A1
Application number: PCT/GB1992/001308
Authority: WO
Inventors: James Bertram King
Original assignee: James Bertram King
Priority date: 1991-07-16
Filing date: 1992-07-16
Publication date: 1993-02-04

Abstract

Method for the monitoring and assessment of an aircraft using one or more sensors (1) mounted on the aircraft structure and viewing selected external locations (2) of the aircraft, in which method: the sensors break down the external view of the aircraft structure into a series of discrete areas forming pixels, radiation of wavelength greater than visible light being detected by the or each sensor for each said area, the sensor or sensor output signals being processed to provide data relating to a parameter defined by radiation detected within each said area.

Description

TITLE

In-flight Aircraft Monitoring System

This invention relates to an in-flight aircraft monitoring system and is primarily concerned with a system for monitoring the function and operation of an aircraft externally.

Various systems have been proposed wherein a television camera or like optical device is positioned at one or more locations outside an aircraft with a view to providing the pilot with a visual means of assessing damage, failure or malfunction of aircraft systems and in particular, engines. Critical aircraft systems, and in particular engines, are more likely to fail during flight phases involving high stresses such as during take off, climb out and possibly following a descent phase. It is during these phases of flight that the pilot is most occupied with operating the aircraft and therefore systems which purport to provide for flight safety by providing a television monitor are of little use because the pilot just simply does not have the time or mental capacity to review a television monitor in an attempt to ascertain or verify a failure. A further psychological factor occurs in that if the pilot is convinced a certain failure has occurred, he will read into any secondary failure monitoring system the information he wishes to see to confirm the failure. Thus, in most cases, it is highly probably that any television display would not be accepted by a pilot as countermanding his assessment of an emergency situation based upon standard instrumentation observation.

U.S. Patent 4816828 describes and claims a flight damage assessment surveillance system comprising little more than the positioning of television cameras to view the external surfaces of an aircraft. This disclosure does not address itself to the problem of surveillance from the aircraft commander's point of view and in real life, the pilot will wish to direct his attention to matters other than "watching television". The disclosure does little more than provide a means for assisting post-crash investigators.

In any event, any form of optical system is probably more subject to failure than aircraft systems themselves and in particular ice, water vapour and smoke may seriously obscure the view obtained from a television camera. In addition, television cameras suffer from "burning-in" and after prolonged periods at high altitude camera tubes are likely to rapidly acquire a ghost image. One of the objects of this invention is to provide a monitoring system to be mounted externally on an aircraft which is of simple construction and which is specifically set up to monitor radiation or other parameters from critical areas of the aircraft only.

Broadly, and in accordance with this invention, there is provided an in-flight monitoring and assessment system for an aircraft comprising a sensor means positioned in or on an aircraft and viewing one or more discrete locations externally of the aircraft structure, the sensor means providing a signal relating to a parameter within the discrete location and a comparator means serving to generate an output warning signal when the parameter deviates from a preset value.

In a preferred embodiment of this invention there is provided an infra-red detector means which is adapted to view an external area of the aircraft and covering said area in a number of discrete elements or pixels. With each said pixel there is associated a predetermined value of the relevant parameter and any deviation from this value feeds an output signal providing a warning. In a particular example, the sensor is arranged to determine radiation temperature with an assigned normal operation value being associated with each pixel. Thus, those pixels which include the area of the engines will be assigned values relating to normal operation, whereas those areas associated with other parts of the aircraft structure will be assigned different values relating to expected ambient temperature conditions.

In a further development of the invention, the infra-red sensors may be combined with a laser range finder or motion detecting means whereby changes or relative displacement of parts of the aircraft structure can be detected. Thus in a particular constructional embodiment the sensor breaks down the external view into a plurality of pixels which may be scanned sequentially or parallel with information relating to temperature or movement or position being derived digitally and thereafter fed to a suitable processing means. By means of a memory, with each pixel there may be associated a range of digital values which are acceptable and these values may change according to the particular flight phase or conditions at any instant.

Thus, at take-off, the exhaust gas temperature sensed for each engine should normally be similar, but where a failure occurs, sensed temperature will be different in the relevant pixel and can be used or called up by the pilot to confirm that he has correctly identified a failed engine using the normal aircraft warning system. In a similar manner, sensors capable of detecting displacement may be used to provide a rapid indication of asymmetric deployment of high lift devices for example or operation of only one aileron or elevator.

By making use of pyro-electric sensor devices operating in the infra-red wave band, it is possible to obtain suitable indication even when there is substantial smoke or vapour obscuring the visual view. Similarly it is possible to differentiate between kerosene vapour which may be present following a simple flameout of an engine, such vapour being at low temperature, and smoke produced by burning material within the engine, which will be at a higher temperature. Thus, the principal disadvantage of using a video monitoring system will be overcome by the present invention.

In a further development of the invention, data corresponding to normal operation is held in a memory store for each discrete pixel. This data is preferably updated according to the flight phase of the aircraft, for example the position of the thrust levers, flying control surfaces, altitude, temperature and the like, so that monitoring of a relatively narrow range for the data sensed in each pixel can be set up. In the event of any deviance from the stored values, an appropriate digital message can be conveyed to the pilot which is readily assimilated even under emergency conditions with the written message being less likely to be misinterpreted.

In an alternative system, the monitoring system will remain dumb unless the aircraft commander wishes to access information, whereupon it can be displayed. The advantage of a system operating in this way is that the arrangement need not form part of the aircraft certification process and is merely available at the commander's discretion if he should need confirmation of a problem.

The number of pixels into which the external aircraft surfaces are broken down need not be large, although each engine area should, for obvious reasons, have its own pixel.

The motion or displacement sensing pixels may incorporate laser range finder devices of miniature form such as those customarily used in missiles and other weapons systems. Such devices are capable of an extremely rapid response time and could therefore detect detachment of any structure from the aircraft and record this, which is impossible with a video system. Data relating to any detachment could be stored and subsequently accessed by the pilot. Thus any detachment of engine cowlings, wing panels, pieces of tread from tyres and the like could be made to provide an early warning of a possible in-flight problem.

The temperature sensing may be applied to tyres and brakes, and movement sensors can be used to determine propeller or turbine fan rotation and reverse thrust.

A further advantage of using a number of pixels, each associated with its own detector, is that interference from extraneous sources of radiation can be minimised with the pixels essentially directed to be wholly occupied by the structure of the aircraft.

An embodiment and preferred features of this invention are now described by way of example and in conjunction with the accompanying drawings.

Referring to the drawings. Figures 1 , 2 and 3 show schematically a transport aircraft in side view, plan view and forward looking cross sectional view on A-A of Figure 2.

According to this invention a sensor means 1 is positioned near the tail end of the aircraft on the underside of the fuselage F. Conveniently, two such sensor means may be provided, each positioned to a respective side of the centre line affording a direct line of sight view of at least the power units PU. The sensor means may comprise two different units and in a first version a sensor is arranged so that it scans a limited field of view such as over the area referenced 2 in Figure 3. The scanning may be effected electronically or mechanically. The field of view scanned is arranged to be relatively small whereby the influence of background radiation can be minimised and the scanning may be continuous or discontinuous whereby the sensor only looks at chosen regions sequentially. In a second version, the sensor comprises a plurality of individual sensing units which are scanned sequentially with each unit being directed towards a particular location. The outputs from each scanned unit or pixel may be processed in parallel fashion or serially.

Scanning arrangements of this kind are known in the art and in particular are utilised in weather satellites, earth resources observation satellites and in the military field, particularly for detecting vehicles and the like to be attacked by land mines.

The area scanned may be increased over a second scanning line as indicated by 3 in Figure 3. The scanner means itself will be housed in a suitable nacelle or possibly within an existing rotating beacon or anti-collision light assembly already positioned on the fuselage. The nacelle may be constructed as a multi-faceted lens system enabling the sensor itself to mounted inboard and in a more controlled environment.

The sensor preferably operates over a range whereby temperatures may be sensed through emission of appropriate infra-red wavelengths. Thus, the sensor over the total field of view, breaks up the field into a number of discrete locations or pixels of which the average temperature of a pixel is assessed. It will be apparent that a knowledge of a temperature at discrete locations on and in the aircraft structure can provide a very valuable early warning of impending failure. For example, hot spots occurring on engine housings can be detected even though one area of the housing may differ from another by only a few degrees centigrade. As well as detecting failures, the sensor is also able to verify correct operation and in particular to determine balance between engines in terms of temperature of the exhaust flow.

In a preferred embodiment, as well as sensing radiation to determine temperature of various parts of the aircraft structure, it is also possible to integrate into the sensor a laser range finding device which is capable of measuring movement and displacement.

In a simplified system the sensors, through the individual pixels, will be monitored only for changes in signals which exceed a particular value or a particular rate. The rate of change which is detected can be adapted so that changes produced when the aircraft carries out a normal turn, which may result in the sensors being temporaril _.blinded by transits of solar radiation, can be ignored.

Processing and presentation of the sensor signals can be effected in a number of ways. Firstly, an analogue display may be provided, using the aircraft weather radar as example, in which the temperatures determined by the sensors for each pixel are displayed in colour, thereby enabling the pilot to use his judgement in assessing whether any area of the aircraft appears abnormal.

In a second display means, the pilot may select a particular location covered by one or more pixels and directly display the measured temperature using a graphical representation. In this case, if one engine is suspect, the pilot is able to display the graph of measured temperature over a period of time to determine whether there has been any sudden change at any point. This method of display is also of assistance where the pilot may have discharged one of the two fire extinguisher bottles and is uncertain as to whether the second should be discharged or kept back for a further emergency. The graphical display will enable the engine temperature to be seen at or shortly after extinguisher discharge, thereby enabling any reduction in temperature with the possibility of the fire being extinguished to be observed.

Figure 4 shows an analogue form of display in which the computer generated outline of the aircraft 40 is depicted on a colour radar display screen 41. The colour temperature determined from each pixel scanned by the sensors is converted to a suitable hue and processed in a form to be displayed on the screen as a series of temperature contours. As can be seen, the hottest temperatures 42 are recorded in the region of the exhaust core of each engine with progressively lower temperatures 43, 44 being recorded outwardly from the engine structures. Information derived from the relative motion or range finder sensors may also be displayed giving an indication of control surface or undercarriage position.

Figure 5 shows an alternative means of displaying the data acquired by the sensor, in which the pilot has specifically requested data determined by the pixels covering the starboard outer engine be presented. The display shows radiated temperature sensed against time and is a real time moving display. The current temperature is indicated at 50 whereas 51 is the instant at which the fire extinguisher was discharged. 52 is the point at which the engine fire alarm initiated. Time minus five minutes shows normal engine temperature prior to the occurrence of the emergency. With a display of this kind, the pilot is able to play back the sensor data, thus enabling a more meaningful assessment of the situation to be made, and in particular whether the fire was of a nature with a rapid increase of temperature in a short period which might make a forced landing essential, or whether it was a more insidious slow failure which can be contained by the on board systems. At 50 the pilot is able to assess that the engine has now cooled well below normal operating temperature after having been shut down.

It will be apparent that the data available can be easily recorded in digital form without requiring the use of wide band recording techniques such as are necessary with optical video systems. With a video system, a greater part of the information captured and stored and available to the pilot is superfluous and irrelevant, whereas in the present invention, the information captured is only that required to appraise the situation.

In order to reduce interference from extraneous sources, various filter means may be incorporated and as a first line of defence, optical filters can be included in front of the sensors and as a second line of defence, electronic filtering can be employed.

Although aircraft systems and in particular engines incorporate a wide variety of sensing devices, primarily to provide for automatic control, such devices are more than likely to be rendered useless especially in the event of a catastrophic engine failure. The present invention enables adequate sensing of parameters to be achieved at a remote location where damage or impairment of the sensor system is unlikely.

In one particular embodiment the sensor means uses a laser radar arrangement operating on the Doppler principal whereby displacement of any parts of the aircraft structure can be detected. By using a laser radar, very small movements in the nature of vibrations in the structure can be determined and by a scanning method a "signature" of various parts of the aircraft structure can be obtained. The technology for obtaining such signatures is already known and used for identifying different classifications of vehicles in a battlefield environment for example.

By combining the laser radar scanning with an infrared detecting system, information can be built up of the structure in discrete elements and relating to temperature profiles and vibration parameters. At any one instant, the overall signature can be compared with a stored value and a suitable alerting signal generated if any predetermined deviance from the normal occurs. With such a system, stored signatures relating to a number of different, phases in the flight would be required and a further embodiment avoids this by generating an average value for the signature over a period of time with the average at any particular instant being a historical value of past sensor measurement. With this system, any sudden deviation determined between the instantaneous signature and the historical averaged signature can be used to generate the alert.

A further advantage of the last mentioned method is that a "library" of signatures can be built up over an extended period of operation of the aircraft and any instantaneous signatures, for example obtained during flight testing, can be compared with the library to determine whether any significant long term changes in vibrational temperature or other characteristics have occurred. By simple measurements a number of factors could be measured, for example, the speed and smoothness of deployment of flaps and like devices, any jerky or discontinuous motion indicated from the sensors possibly giving advanced warning of an impending failure. Similarly, unusual or excessive vibrational movements in panels and airframe structures could be detected to provide an indication of fractures , cracking and unacceptable looseness in connections.

Claims

\ θCLAIMS

1. An in-flight monitoring and assessment system for an aircraft comprising a sensor means positioned in or on an aircraft and viewing one or more discrete locations on the external aircraft structure, the sensor means providing a signal relating to a parameter within the discrete location.

2. A system according to Claim 1, wherein the sensor detects radiation or motion or position or any combination thereof.

3. A system according to Claim 1 or 2, wherein the sensor or sensors are arranged to view a plurality of discrete locations which in combination cover a substantial part of the critical aircraft structure, the signal derived from each location forming one pixel element of an overall image.

4. A system according to any preceding claim, wherein the signal from the sensor is processed to provide an output signal feeding a display means or a comparator.

5. A system according to Claim 4, wherein the comparator means serves to generate an output warning signal when the parameter deviates from a preset value.

6. A system according to any preceding claim, comprising an infra-red detector means which is adapted to view an external area of the aircraft and covering said area in a number of discrete elements or pixels, each said pixel being associated with a predetermined value of a relevant parameter and any deviation from this value feeding an output signal for a display or providing a warning.

7. A system according to Claim 6, wherein the infra-red sensors are combined with a laser range finder or motion detecting means whereby changes or relative displacement of parts of the aircraft structure are detected, whereby the sensor breaks down the external view into a plurality of pixels which may be scanned sequentially or in parallel with information relating to temperature or movement or position being derived digitally and thereafter fed to a suitable processing means preferably including a memory such that with each pixel there. is associated a range of digital values which are acceptable, said values changing according to the particular flight phase or conditions at any instant. IS

8. Method for the monitoring and assessment of an aircraft using one or more sensors mounted on the aircraft structure and viewing selected external locations of the aircraft, in which method: a) the sensors break down the external view of the aircraft structure into a series of discrete areas forming pixels, b) radiation of wavelength greater than visible light being detected by the or each sensor for each said area, c) the sensor or sensor output signals being processed to provide data relating to a parameter defined by radiation detected within each said area.

9. Method in acordance with Claim 8, wherein the sensors scan the aircraft structure over a predetermined area, said area being divided into pixels.

10. Method in accordance with Claim 8 or 9, wherein the sensors are responsive to infra-red radiation, particularly fcjr infra-red radiation.

11. Method in accordance with any preceding Claim 8 to 10, wherein the sensors or further sensors determine range, position or movement within the pixel.

12. An aircraft including a system according to any preceding claim.

13. A system substantially as described herein and exemplified.