GB2179612A

GB2179612A - Aircraft instrumentation

Info

Publication number: GB2179612A
Application number: GB08318715A
Authority: GB
Inventors: Peter John Bennett
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1982-07-12
Filing date: 1983-07-11
Publication date: 1987-03-11
Also published as: GB2179612B

Abstract

In an aircraft attitude indicator as presented in a head up display format an aircraft symbol (11) indicates pitch angle with respect to pitch bars, such as pitch bar (12). The pitch bars are labelled to indicate actual pitch angle (eg (14)). The aircraft symbol (11) is fixed in the display (10) and the pitch bars move across the display in response to changes in pitch. The bar spacing is varied with pitch angle, as may be seen by comparing the spacing between bar pairs (eg (12,30) and (31,32)). Thus the number of bars in the display gives a pilot an analogue of pitch such that attitude may be assessed without reading pitch bar labels. In particular the 'ladder effect', as occurs in prior art indicators when looping manoeuvres are performed and rapid movement of pitch bars occurs at rate at which pitch bar labels cannot be read, is avoided. <IMAGE>

Description

SPECIFICATION Aircraft attitude indicator This invention relates to aircraft instrumentation, and in particular to instrumentation for providing an indication of aircraft attitude.

In aviation the pilot of an aircraft requires an indication of attitude in order to accurately and successfully complete manoeuvres. In aerobatic aircraft where complex manoeuvres are performed a reliable attitude indication is vital. Any confusion or misinterpretation of attitude can result in failure of the manoeuvre, with potentially disastrous consequences.

In an aircraft equipped with a head up display an attitude indication may be provided by labelled bars overlaid on an outside view. A symbol may be placed in the field of view to indicate for example pitch, Climb Dive Angle (CDA) or Velocity Vector (VV) by its relationship to the bars. The symbol may be fixed in the display and pitch indicated by movement of the bars past the symbol or the symbol may move in the display to indicate CDA or VV, and CDA indicated by movement of the bars past the symbol. In this specification and as is common amongst pilots the term pitch will be used to encompass both actual pitch and CDA, and pitch bars used to encompass any bars indicative of attitude.

During a manoeuvre involving a high rate of change of pitch, such as a looping manoeuvre, pitch bar movement is rapid. This can lead to pilot confusion as the bar labels cannot be read and a feel for absolute pitch angle or CDA can be lost. This is known by pilots as the 'ladder effect'.

According to the present invention, there is provided an aircraft attitude indicator having pitch bars and characterised in that pitch bar spacing is varied over a range of pitch angles and that such bar spacing provides a measure of pitch.

The spacing may be advantageously varied such that the pitch bars are more closely spaced towards zenith and nadir. The spacing of visible bars may be contracted towards the zenith and nadir or alternatively the spacing may be equidistant such that interpoiation between bars may be easily made.

In order that features and advantages of the present invention and the way that it may be put into effect may be appreciated some embodiments will now be described by way of example only with reference to the accompanying diagrammatic drawings of which: Figure 1 represents a typical Head up Display (HUD) format, Figure 2 represents the HUD format at a different angle of pitch, Figure 3 represents an alternative HUD format, and Figure 4 represents means for providing a head up display.

Where appropriate in the figures, common reference numerals have been used.

In a Head up Display 10 (Figure 1 ) an aircraft symbol 11 indicates pitch angle with respect to pitch bars, such as pitch bar 12. The pitch bars are labelled, such as with label 14, to indicate actual pitch angle. The aircraft symbol 11 is fixed in the display 10 and the pitch bars move across the display in response to changes in pitch. The pitch bar representing zero pitch (not shown) is a reinforced bar and superimposed over the actual horizon as viewed from the aircraft, when it is displayed. In accordance with the present invention, the pitch bar spacing is varied over a range of pitch angles. This is illustrated (Figure 2) to show how the spacing is reduced as the zenith (90") is approached. An indicator 20 is provided at the zenith. A similar indicator (not shown) is provided at nadir.It will be appreciated that the displayed bars are equally spaced within the display, 10, so that linear interpolations may be made. For example aircraft symbol 21 (Figure 2) accurately indicates a pitch angle of 77.5 .

The pitch bar spacing may be set in response to a gearing coefficient computed from pitch angle such that at zero pitch the gearing is 1:1, varying gradually to approximately 3:1 at zenith and nadir.

From the foregoing, the following specific features of the present invention will be apparent: the number of bars in the display gives the pilot an analogue of pitch ii attitude may be assessed without reading pitch bar labels iii rate of change of pitch may be assessed by bar spacing change and the ladder effect is overcome, and iv a desired pitch angle may be achieved by linear interpolation.

In one embodiment of the present invention the gearing applied to the pitch bars was computed in accordance with the following law: For pitch angle ((3) less that if5": Gearing coefficient = 1 50 For pitch angle (0) greater than +5 : Gearing coefficient = ( 5) (0 + 45) In an alternative embodiment of the present invention (Figure 3) pitch bar spacing is contracted towards zenith and nadir, without enforcing linear spacing of the visible bars.

in general, the aircraft symbol is the display may be used to indicate either climb dive angle (ie the smaller angle between aircraft velocity vector and the horizontal) or pitch angle and bank angle.

in order that the invention may be further appreciated means for computing the gearing and setting pitch bar spacing will now be described.

Values for CDA 40 (Figure 4), pitch angle 41, and bank angle 42 are available from aircraft systems, and may be combined to position an aircraft symbol via generator 43 within a display provided by a pilot display unit 44 for presentation as a head up display 45. The system as thus far described and its operation will be known to those skilled in the art.

From CDA 40 or actual pitch angle 41 a pitch angle (o) is computed 46. The basis for computation will depend upon whether a CDA or actual pitch display is required, and is indicated diagrammatically by an OR gate 47 for the sake of clarity. A gearing G (that is a scale factor determining pitch bar spacing) of unity 48 or (50/(0 + 45 )) 49 is applied to computed pitch (0) dependent upon a comparison 400 with 5 , representing a gearing function cross-over, and as described above. The required gearing is applied 401 to pitch bars generated by a conventional pitch bar generator 402. The general pitch bars are positioned within the display 403 with respect to computed pitch angle 0. It will be appreciated by those skilled in the art that the representation of Figure 4 is presented as a block diagram to show clearly how the present invention may be implemented. It will further be appreciated that the implementation will vary from installation to installation and that in particular the functional blocks may be embodied in the programs for a computer, which form no part of the present invention as such.

Claims

CLAIMS The matter for which the applicant seeks protection is:

1. An aircraft attitude display comprising a cathode ray tube or other display screen and means for producing a displayed image which includes pitch bars and characterized in that pitch bar spacing is varied over a range of pitch angles such that bar spacing provides a measure of pitch.

2. An aircraft attitude display as claimed in claim 1 and characterized in that the pitch bars are more closely spaced towards zenith and nadir.

3. An aircraft attitude display as claimed in claim 1 or claim 2 and characterized in that the spacing of visible bars is equidistant.

4. An aircraft attitude display as claimed in claim 1, claim 2 or claim 3 and characterized in that bar spacing is set by a gearing computed from pitch angle.

5. An aircraft attitude display as claimed in claim 4 and wherein the gearing is gradually varied between a first value at zero pitch and a second value at zenith and nadir.

6. An aircraft attitude display as claimed in claim 4 and wherein the gearing is varied in accordance with a predetermined function.

7. An aircraft attitude display as claimed in any preceding claim and wherein bar spacing provides a measure of actual pitch.

8. An aircraft attitude display as claimed in any of claims 1 to 6 and wherein bar spacing provides a measure of climb dive angle.

9. An aircraft attitude display as claimed in any preceding claim and wherein an aircraft symbol moves within the display to indicate velocity vector and wherein bar spacing provides a measure of climb dive angle as a component of velocity vector.

10. An aircraft attitude display substantially as herein described with reference to the drawings.

11. A head up display providing an aircraft attitude display as claimed in any preceding claim.

12. An aircraft including an attitude display as claimed in any of claims 1 to 10

13. A method of indicating pitch on a cathode ray tube or other display screen involving the step of varying pitch bar spacing over a range of pitch angles such that bar spacing provides a measure of pitch.