Communications: electrical – Aircraft alarm or indicating systems – Nonalarm flight indicator
Reexamination Certificate
1999-11-05
2003-05-20
Swarthout, Brent A. (Department: 2632)
Communications: electrical
Aircraft alarm or indicating systems
Nonalarm flight indicator
C340S974000, C340S975000, C345S007000
Reexamination Certificate
active
06567014
ABSTRACT:
TECHNICAL FIELD
The present invention relates to aircraft head-up display (HUD) systems and, in particular, to HUD display strategies and symbologies to aid a pilot in detecting and recovering from unusual aircraft attitudes (climb/dive pitch and or roll) during flight.
BACKGROUND OF THE INVENTION
HUD systems are now widely used in both military and commercial aircraft to provide pilots with essential information superimposed onto their forward field of view through the aircraft windshield. The information displayed is typically data and/or symbolic images indicative of flight conditions, such as aircraft altitude or airspeed, navigation information, or guidance information.
FIG. 1
generally illustrates a side view of the optics geometry of a head up display system in the cockpit
10
of an aircraft
11
having a windshield
12
. A pilot is shown at
13
with an eye shown at an eye reference point
14
within an eyebox (exit pupil) indicated by dashed lines
15
. The eye reference point
14
is a geometrical point in space.
FIG. 2
illustrates a field of view from the pilot to the combiner
20
.
Guidance information displayed on a HUD combiner for observation by a pilot generally includes symbology that represents position and attitude guidance for the aircraft during flight. One example is a flare anticipation cue implemented in a Flight Dynamics head-up guidance system that is certified by the Federal Aviation Administration for use on Boeing 737-300 aircraft. The flare anticipation cue alerts the pilot several seconds before the aircraft reaches a flare initiation height and indicates to the pilot the pitch up rate required at the initial part of the flare.
Another application of head-up displays is guidance information that can be displayed to a pilot during low visibility ground weather conditions to assist the pilot after touchdown in safely taxiing the aircraft to the airport terminal. A pending patent application, also owned by the assignee of the present application, describes methods and symbologies for taxi mode of operation, including the production of a turn anticipation cue that, together with a turn direction arrow, is displayed as a symbol on a HUD system combiner as part of aircraft rollout on an active runway and taxi operations to and from an airport terminal. The turn anticipate cue alerts the pilot that a turn from the current path of the aircraft is approaching within a predetermined time or distance. HUD displays thus can be used in various modes of operation, including a basic mode, en route mode, approach/landing mode and a taxiing mode as noted.
One very important yet challenging task is to design a HUD display to assist the pilot in recognizing and recovering from an unusual attitude (UA) of the aircraft. One important aspect of the problem is to enable the pilot to quickly and accurately identify which way is up (away from the center of the earth). In a heads-down display (HDD), color is used to advantage in this regard. An attitude display or attitude indicator ball in the HDD displays a straight line representing the horizon; solid brown color below the horizon (i.e. toward the ground), and a solid blue color field above the horizon to indicate the direction of the sky. That combination of indicia makes it easy for the pilot to quickly identify which way is up. Most head-up displays, however, are limited to simple monochromatic symbologies: Solid fields, shading, cross-hatching and the like generally are not used because they occlude the view through the windshield outside the aircraft. Consequently, attitude indicators like the HDD cannot be used for HUD.
Another challenge in addressing unusual attitudes in HUD arises because HUD's provide a very limited field of view (FOV). For example, a typical HUD today provides a 30 degree by 24 degree FOV (The dimensional units most often used to describe symbol size and position are miliradians (mrad) of angular arc. Either way, a specified viewing distance is required to convert to equivalent linear dimensions of the display). Given the relatively limited FOV available in the HUD, display of a wide range of conformal climb/dive pitch angles is not possible. One means to increase the range of angles displayed is through pitch compression. However, compression of the pitch ladder is undesirable, at least in some circumstances, as it may to lead to disorientation. Put another way, a “conformal” or one-to-one display on the HUD consistently tracks the “real world” that the pilot is viewing through the windshield. Compression seems necessary in order to accurately display the more extreme excursions in pitch and roll that occur during unusual UA's, yet conformal orientation cues may be superior in just those situations. There is some controversy as to the most appropriate approach. If full-time scaling is not selected, this issue is further complicated by consideration of switching between compressed and noncompressed display modes; for example, should a compression mode switch take place gradually or in a discrete step. See Newman at page 87.
FIGS. 3 and 4
illustrate a typical prior art HUD display. The features and symbols employed in this type of display shown in
FIG. 3 and 4
include the following: to the left side of the display is an air speed indicator
302
, in this case a “tape” display combining both analog and digital features. A digital ground speed indicator
304
also is provided in the lower left quadrant of the display. Other known air speed indicators include digital and counter-pointer symbols. To the right side of the display is an altitude indicator
310
. In this case, an altitude “tape” is shown. A digital vertical speed indicator
306
also is provided generally in the lower right hand quadrant of the display. Again, other types of altitude displays are known in the art. Referring to
FIG. 4
, the display
300
includes a horizon indicator
312
, in this case a straight line segment with no break. A conventional pitch ladder
314
is provided for indicating climb/dive attitude in conjunction with the horizon
312
.
The pitch ladder
314
in
FIG. 4
includes a series of steps, spaced apart typically in 5 degree pitch increments. There, the steps are labeled
5
,
10
, (
0
is the horizon line
312
), and finally minus 5 degrees. Each pitch step indicator comprises a pair of line segments with a space in the middle, symmetrically arranged about the water line indicator
316
, and having perpendicular ends on the outboard side of each line segment pointing toward.the horizon; for example, see reference number
315
. The water line symbol
316
, also called a bore sight, indicates an axis parallel to the fuselage of the plane and generally remains in a fixed position near the center of the FOV.
An airplane: symbol
320
in
FIG. 4
indicates the current flight path of the aircraft. In the display of
FIG. 4
, the aircraft is in what would generally be considered an unusual attitude. The display indicates a pitch of about 2 degrees and a roll, angle of about 140 degrees. Here, an “Augie arrow”
322
is displayed to point toward the horizon. The Augie arrow has been suggested for use during unusual attitudes as an orientation cue, but we consider it too small and too subtle and not compelling enough to be useful in identifying and recovering from a UA.
FIG. 5
is another example of a prior art HUD display, including most of the features and symbols already described with reference to FIG.
4
. In
FIG. 5
, the horizon
330
is shown as a dashed line, known as a ghost horizon. In this case, the pitch ladder provides the usual 5 degree steps; and it can be observed that 0 degrees pitch is just about where the horizon
330
is shown in the drawing. As the pitch ladder moves further down in the display (presumably as the aircraft assumes a greater pitch), the horizon would no longer be visible on the display (assuming no automatic compression of the ladder). The ghost horizon is dashed to indicate that it is no longer a conformal representation of the horizon relative to the pitch
Hansen Richard
Hartman Brian
Wood Robert B.
Eppele Kyle
Jensen Nathan O.
Rockwell Collins, Inc.
Swarthout Brent A.
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