Improved head-up display pitch bar system for aircraft

DETAILED DESCRIPTION It is an object of the invention to provide a head-up display system to provide the pilot with very clear analog indications of climb-dive angle which can be immediately appreciated and also to provide a particular indication of chosen climb-or-dive angles .
+-.
.
phi.
.
sub.
1 which will be useful as references against which climb-or-dive angles may be judged.
According to the present invention a head-up display system includes means for generating a pitch ladder pattern having pitch bars which are straight lines with a central gap, the pitch bars representing climb angles being solid lines and the pitch bars representing dive angles being dashed lines, the pattern having a scale which is unity in a central region and which decreases smoothly from the central region towards the extremes of the pattern, characterized in that: a.
the central bar representing level flight is considerably longer than any other bar, and the lengths of the bars decrease according to a relationship with their displacement from the central bar; b.
the zenith or 90.
degree.
climb angle is indicated by a distinctive star symbol and the nadir or 90.
degree.
dive angle is indicated by a distinctive earth symbol, and c.
the pattern has two inner regions on either side of the central region, and two outer regions between the inner regions and zenith and nadir respectively, and the graduation intervals in the outer regions are considerably greater than the graduation intervals in the inner regions, so that the first graduation interval in each outer region is considerably wider than the last graduation interval in each inner region, thus providing distinctive indications of the angles at which the inner regions end and the outer regions begin.
Preferably the zenith star symbol is shown in outline only, and the earth symbol is a circle filled by shading lines.
Preferably the central region extends to .
+-.
5.
degree.
and the inner regions extend to .
+-.
30.
degree.
.
Preferably the graduation intervals in the outer regions are twice as large as the graduation intervals in the inner regions