U.S. patent application number 14/079408 was filed with the patent office on 2015-05-14 for lighting systems for landing in a degraded visual environment.
The applicant listed for this patent is Taylor L. Kiel. Invention is credited to Taylor L. Kiel.
Application Number | 20150130644 14/079408 |
Document ID | / |
Family ID | 53043340 |
Filed Date | 2015-05-14 |
United States Patent
Application |
20150130644 |
Kind Code |
A1 |
Kiel; Taylor L. |
May 14, 2015 |
LIGHTING SYSTEMS FOR LANDING IN A DEGRADED VISUAL ENVIRONMENT
Abstract
Lighting systems and methods for landing in a degraded visual
environment are disclosed. The lighting systems comprise one or
more lighting units mounted to an aircraft operable to hover near a
landing zone. Each lighting unit is operable to provide adjustable
illumination to the landing zone, and has a radiant power output
between a minimum and a maximum. The minimum radiant power output
is just sufficient to allow a pilot to distinguish features in the
landing zone when below a first altitude wherein the downwash from
the aircraft rotors, propellers, or engines begins to raise
particulates from the landing zone and continues to be just
sufficient to allow the pilot to distinguish features as the pilot
descends from the first altitude to termination at the landing
zone, and the maximum radiant power output is less than about five
times the minimum radiant power output.
Inventors: |
Kiel; Taylor L.; (El Paso,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kiel; Taylor L. |
El Paso |
TX |
US |
|
|
Family ID: |
53043340 |
Appl. No.: |
14/079408 |
Filed: |
November 13, 2013 |
Current U.S.
Class: |
340/953 |
Current CPC
Class: |
B64D 47/04 20130101 |
Class at
Publication: |
340/953 |
International
Class: |
G08G 5/02 20060101
G08G005/02 |
Claims
1. An aircraft lighting system comprising one or more lighting
units mounted to an aircraft, the aircraft operable to hover near a
landing zone, wherein each lighting unit is operable to provide
adjustable illumination to an illuminated area in the landing zone,
and wherein each lighting unit has a radiant power output between a
minimum and a maximum, wherein the minimum radiant power output is
just sufficient to allow a pilot to distinguish features in the
landing zone when below a first altitude wherein the downwash from
the aircraft rotors, propellers, or engines begins to raise
particulates from the landing zone and continues to be just
sufficient to allow the pilot to distinguish features as the pilot
descends from the first altitude to termination at the landing
zone, and wherein the maximum radiant power output is less than
about five times the minimum radiant power output.
2. The aircraft lighting system of claim 1, wherein each lighting
unit comprises a plurality of lighting elements emitting light at a
plurality of wavelengths.
3. The aircraft lighting system of claim 2, wherein the plurality
of wavelengths can produce white, green, and infrared
illumination.
4. The aircraft lighting system of claim 2, wherein the plurality
of lighting elements comprise light emitting diodes (LEDs).
5. The aircraft lighting system of claim 1, wherein the illuminated
area of the landing zone is approximately equal in size and shape
to the field of view of a pilot or crew member looking through a
chin bubble or a side door or window of the aircraft.
6. The aircraft lighting system of claim 5, further comprising a
shroud, wherein the shroud is operable to limit the emission of
light to a direction toward the illuminated area of the landing
zone.
7. The aircraft lighting system of claim 1, wherein each lighting
unit further comprises one or more lasers aimed generally in the
direction of the illuminated area of the landing zone.
8. The aircraft lighting system of claim 7, wherein each lighting
unit comprises a plurality of lasers emitting light at a plurality
of wavelengths.
9. The aircraft lighting system of claim 8, wherein the plurality
of wavelengths comprise red, green, and infrared.
10. The aircraft lighting system of claim 8, wherein the plurality
of lasers comprise semiconductor lasers each having a power output
of between 0.1 mW and 1.0 mW.
11. The aircraft lighting system of claim 7, wherein the one or
more lasers create a pattern onto the landing zone which changes as
a function of altitude.
12. The aircraft lighting system of claim 11, wherein a spot
projected from the one or more lasers on the landing zone changes
size as a function of altitude.
13. The aircraft lighting system of claim 11, wherein a spot
projected from the one or more lasers onto the landing zone changes
shape as a function of altitude.
14. The aircraft lighting system of claim 11, wherein two spots
projected from the one or more lasers onto the landing zone have a
separation which changes as a function of altitude.
15. The aircraft lighting system of claim 1, wherein the
particulates comprise dust or sand.
16. The aircraft lighting system of claim 1, wherein the
particulates comprise water, snow, or ice.
17. A method for illuminating a landing zone comprising providing
one or more lighting units to an aircraft, the aircraft operable to
hover near the landing zone, wherein each lighting unit is operable
to provide adjustable illumination to the landing zone, and wherein
each lighting unit has a power between a minimum and a maximum,
wherein the minimum power is just sufficient to allow a pilot to
distinguish features in the landing zone from below a first
altitude wherein the downwash from the aircraft rotors, propellers,
or engines begins to raise particulates from the landing zone and
continues to be just sufficient to allow the pilot to distinguish
features as the pilot descends from the first altitude to
termination at the landing zone, and wherein the maximum power is
less than about five times the minimum power; during an approach or
landing of the aircraft, leaving the lighting units off until the
aircraft descends below the first altitude, and turning the
lighting units on below a second altitude wherein the second
altitude is below the first altitude.
18. The method of claim 17, wherein the second altitude is about 20
ft.
Description
FIELD OF THE INVENTION
[0001] One or more embodiments of the present invention relate to
illumination systems for assisting in landing aircraft in a
degraded visual environment.
BACKGROUND
[0002] Rotorcraft (e.g., helicopters) and VTOL (vertical takeoff
and landing) aircraft have a natural tendency to stir particulates
into the air with their downwash when operating near the Earth's
surface. This typically occurs while maintaining or transitioning
in or out of the hovering flight regime, at an altitude that is
within one to two times the equivalent rotor diameter. In certain
environments, a relatively high concentration of stirred
particulates, typically dust, may significantly obscure the
pilot(s) field of view (FOV). The particulates can result in the
loss of outside visual references, or brownout (in a dust
environment), which can induce spatial disorientation in a pilot.
The pilot(s) may not be able to see the ground. Depending on
conditions, particulates may comprise dust, sand, snow, or other
materials that can become airborne either due to rotor downdraft or
local weather conditions.
[0003] The difficulty of a brownout situation is further compounded
at night, because there are fewer visual cues available. Further,
pilots (especially military aviators) may be using night-vision
goggles (NVGs) which typically restrict the FOV to 40.degree..
Using NVGs, also referred to as flying "aided," provides a visual
acuity of 20/25 at best [Army 2007A]. Due to the challenges
involved in such operations, pilots learn to use a variety of
compensatory methods.
[0004] One method of compensation is to maintain enough forward
airspeed during the approach and touchdown to outrun the formation
of particulates and prevent the particulate formation from
enveloping the cockpit. While effective in some situations, this
method is not suitable for many landing zones, particularly those
that are rough, sloping, confined, or pinnacle. Another method is
referred to as termination to a point OGE (out of ground effect)
[Army 2007B, Army 2013]. This method requires more power. The
initial approach is to a high hover position directly over the
intended point of landing. The high hover position is used to stir
and dissipate the dust before descending to the ground. Hovering
OGE is effective is some situations, but there are disadvantages.
First, depending on the aircraft gross weight and environmental
conditions, the power required may not be available to hover OGE.
Second, it may not be a tactically advisable maneuver, because it
exposes the aircraft in its most vulnerable state for an extended
period. Third, descending from an OGE hover surrounded by a ring of
circulating dust can induce spatial disorientation, resulting in
improper control manipulation, consequent aircraft drift, and/or an
unanticipated, possibly damaging touchdown rate.
[0005] Generally, in helicopters, once outside references are lost
out of the windshield, focus is directed through the chin bubble
and/or other cockpit door windows. If references are lost through
the chin bubble and windows, the focus transitions to the flight
instruments, and the approach is aborted using an instrument
take-off (ITO). Technically, since the maneuver is not initiated
from the ground, it is actually more a modified "go-around." Once
above the dust with adequate visibility, the crew may continue
visually and re-evaluate the situation.
[0006] Regardless of the method employed, there is always the
potential to become partially or completely enveloped in dust. At
night, when shifting focus from the windshield to the chin bubble
or other windows, NVG use provides additional limitations. When
looking through NVGs, depth perception is severely limited,
especially at close ranges. The resolution at close range may be
lower due to individual focus settings or constraints. The pilot
may not have a clear sight picture of the immediate ground surface
during the final stage of an approach. Cross-checking the chin
bubble or cockpit door window looking through NVGs requires a large
head movement that can be hazardous during the critical final
moments of an approach.
[0007] An alternative, not printed in Army training manuals, is
used in some cases to provide improved visibility beneath the
aircraft. The landing light or search light is turned on, and the
pilot looks beneath the NVG eyepieces and through the chin bubble
or cockpit door window using the unaided eye. This technique can
offer the best combination of available options by allowing the
pilot to divide his/her attention by looking through the windshield
using the NVGs (arrow 102) at horizon associated references and
maintaining a good ground reference cross-check by glancing through
the chin bubble unaided (arrow 104), as illustrated in FIG. 1.
[0008] One problem with using landing lights or search lights in
this way is that tactical considerations may be sacrificed to the
intensity of the light. Further, the landing light and searchlight
are considered incompatible with NVGs, because they are
conventional white lights (unless the searchlight is infrared). The
compatibility issue is, however, more of a misconception than a
reality with modern NVGs. Modern NVGs, such as the AN/AVS-6(V)3
(Exelis Night Vision, Roanoke Va.), have automatic brightness
control (ABC) and bright source protection (BSP) which are built-in
features designed to prevent blinding the user or damaging the
NVGs. However, most white lights are still not conducive for use
with NVGs, because ambient light is amplified approximately
2000-3000 times by the goggles, and BSP has the side effect of
lowering resolution [Army 2007A].
[0009] Viewing underneath the goggles aided by the landing light or
searchlight light works in many instances, but in heavy or severe
dust the pilot may still be disoriented due to the intensity. This
is likely why the method is not formally recommended. Military
helicopters do have infrared searchlights that are considered NVG
compatible, but as discussed above, looking through the chin bubble
with NVGs requires excessive head movement and provides low
resolution viewing, limited FOV, and lack of depth perception. The
intensity of the infrared searchlight can also produce
disorientation while looking through NVGs in heavy or severe dust
just as the landing light can. Although the infrared searchlight
has adjustable brightness, it is a very coarse adjustment, has
limited directional control, and always defaults to maximum
brightness when power to it is cycled.
SUMMARY OF THE INVENTION
[0010] Lighting systems and methods for landing in a degraded
visual environment are disclosed. The lighting systems comprise one
or more lighting units mounted to an aircraft that is operable to
hover near a landing zone. Each lighting unit is operable to
provide adjustable illumination to the landing zone, and has a
radiant power output between a minimum and a maximum. The minimum
radiant power output is just sufficient to allow a pilot to
distinguish features in the landing zone when below a first
altitude wherein the downwash from the aircraft rotors, propellers,
or engines begins to raise particulates from the landing zone and
continues to be just sufficient to allow the pilot to distinguish
features as the pilot descends from the first altitude to
termination at the landing zone. The particulates can include dust,
sand, water, snow, or ice.
The maximum radiant power output is less than about five times the
minimum power. In some embodiments the maximum radiant power output
is less than about three times the minimum radiant power output. In
some embodiments the maximum radiant power output is less than
about two times the minimum radiant power output.
[0011] Each lighting unit can include a plurality of lighting
elements collectively emitting light at a plurality of wavelengths.
The plurality of wavelengths produce white, green, and infrared
illumination; each illumination can be individually enabled. The
plurality of lighting elements can be light emitting diodes
(LEDs).
[0012] The illuminated area of the landing zone can be
approximately equal in size and shape to the field of view of a
pilot or crew member looking through a chin bubble or a side door
or window of the aircraft. A shroud can be provided, limiting the
emission of light to a direction toward the illuminated area of the
landing zone.
[0013] Each lighting unit further can also include one or more
lasers aimed generally in the direction of the illuminated area of
the landing zone. The lasers can emit light at a plurality of
wavelengths including red, green, and infrared which can be
individually enabled. The lasers can be semiconductor lasers each
having a power output of between 0.1 mW and 1.0 mW.
[0014] One or more lasers can create a pattern on the landing zone
which changes as a function of altitude. A spot projected from a
laser onto the landing zone can change size as a function of
altitude. A spot projected from a laser onto the landing zone can
change shape as a function of altitude. Two spots projected from a
laser onto the landing zone can have a separation which changes as
a function of altitude.
[0015] A method for illuminating a landing zone is also provided.
One or more lighting units are attached to an aircraft that is
operable to perform vertical takeoffs and landings. Each lighting
unit is operable to provide adjustable illumination to a landing
zone, and has a radiant power output between a minimum and a
maximum, wherein the minimum radiant power output is just
sufficient to allow a pilot to distinguish features in the landing
zone from below a first altitude wherein the aircraft rotors,
propellers, or engines begins to raise particulates from the
landing zone and continues to be just sufficient to allow the pilot
to distinguish features as the pilot descends from the first
altitude to termination at the landing zone, and wherein the
maximum radiant power output is less than about five times the
minimum radiant power output. In some embodiments the maximum
radiant power is less than about three times the minimum radiant
power output. In some embodiments the maximum radiant power is less
than about two times the minimum radiant power output. During an
approach or landing of the aircraft, the lighting units are left
off until the aircraft descend below the first altitude, and then
turned on below a second altitude wherein the second altitude is
below the first altitude. The second altitude can be about 20
ft.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows the "cross-check" technique looking through and
under NVGs.
[0017] FIG. 2 shows aircraft losses from non-combat causes for
2002-9.
[0018] FIG. 3 shows simulated airflow (3A) and dust density (3B)
for a thrust-normalized advance ratio of 0.80.
[0019] FIG. 4 shows simulated airflow (4A) and dust density (4B)
for a thrust-normalized advance ratio of 0.29.
[0020] FIG. 5 shows simulated airflow (5A) and dust density (5B)
for a thrust-normalized advance ratio of 0.12.
[0021] FIG. 6 shows a concept illustration for a dust-light system
mounted on a helicopter.
[0022] FIG. 7 shows various views of a dust-light prototype
[0023] FIG. 8 shows an example mounting structure and
connections
[0024] FIG. 9 shows the chin bubble FOV for the right pilot in a
Black Hawk helicopter
[0025] FIG. 10A shows the surface visible through the chin bubble;
FIG. 10B illustrates the inverse square law.
[0026] FIG. 11 shows two proposed mounting locations for
dust-lights on a Black Hawk helicopter.
[0027] FIG. 12 shows a first mounting location with the access
panel removed.
[0028] FIG. 13 shows details of a second mounting location.
[0029] FIG. 14 shows a third mounting location.
[0030] FIG. 15 shows an example switch arrangement on the
collective.
[0031] FIG. 16A shows the cockpit view during heavy dust approach
at 19 ft above ground level (AGL).
[0032] FIG. 16B shows the cockpit view during heavy dust approach
at 9 ft AGL.
[0033] FIG. 17A shows the cockpit view during heavy dust approach
at 3 ft AGL.
[0034] FIG. 17B shows the cockpit view during heavy dust approach
at termination.
DETAILED DESCRIPTION
[0035] Before the present invention is described in detail, it is
to be understood that unless otherwise indicated this invention is
not limited to specific aircraft or specific lighting modalities.
It is also to be understood that the terminology used herein is for
the purpose of describing particular embodiments only and is not
intended to limit the scope of the present invention.
[0036] It must be noted that as used herein and in the claims, the
singular forms "a," "and" and "the" include plural referents unless
the context clearly dictates otherwise. Thus, for example,
reference to "a lighting unit" includes two or more lighting units,
and so forth.
[0037] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limit of that range, and any other stated or intervening
value in that stated range, is encompassed within the invention.
The upper and lower limits of these smaller ranges may
independently be included in the smaller ranges, and are also
encompassed within the invention, subject to any specifically
excluded limit in the stated range. Where the stated range includes
one or both of the limits, ranges excluding either or both of those
included limits are also included in the invention. Where the term
"about" is used in front of a numerical value, the value is deemed
to be within .+-.10% of the numerical value.
[0038] As used herein, the term "particulate" refers to any small
particles that can become airborne in a landing location either due
to rotor downwash or due to local weather conditions. Examples
include dust, sand, and snow. Examples described herein are general
described using dust as an exemplary but non-limiting embodiment of
particulates that can reduce visibility. Exemplary landing zones
are dry, dusty surfaces, although degraded visible environments can
also occur under conditions of heavy fog, rain, snow, water
landings, marsh landings, and so on.
[0039] As used herein, the term "light dust" refers to a degraded
visual environment (DVE) in which objects and terrain beyond the
region of a particulate cloud are visible (i.e., an observer such
as a pilot can see through the DVE).
[0040] As used herein, the term "moderate dust" refers to a
degraded visual environment (DVE) in which only objects and terrain
within a particulate cloud are visible (i.e., an observer can see
part way through the DVE).
[0041] As used herein, the term "heavy dust" refers to a degraded
visual environment (DVE) in which no objects or terrain within a
particulate cloud is visible (i.e., visibility ends abruptly within
the DVE).
[0042] As used herein, the term "altitude" refers to the vertical
position of an aircraft (height above the Earth's surface) relative
to a position where the aircraft is stationary on the Earth's
surface.
[0043] As used herein, the term "termination" refers to the end
state of a landing approach where the "altitude" as defined above
has reached zero.
[0044] The inventor has surprisingly found that pilots can perform
best when using a combination of aided and unaided viewing
techniques in the dust environment at night. Accordingly, there is
a need for a purpose-built landing illumination system better
suited to night-time landing in particulate environments than prior
art landing lights.
[0045] FIG. 2 shows the relative incidence of rotary wing combat
non-hostile event losses for the years 2002-9 from a study on
rotorcraft safety [Harrington 2010]. "Brownouts" or "degraded
visual environment" (DVE), accounted for the greatest number of
combat non-hostile losses. The study concluded that an integrated
systems approach would be required to overcome the hazards
associated with dust environments, suggesting elements such as
improved cockpit display symbology and auto-land capabilities.
[0046] Currently, such prospective solutions and avionics-based
technologies are in different stages of development. Various
sensors are used to construct terrain and obstacle imagery
displayed inside the cockpit along with corresponding flight
symbology. One approach uses millimeter-wave radar to detect
obstacle hazards and overlay them onto a known terrain database.
Another system uses ladar combined with a dynamic graphics
generator to produce a comparable display interface. While showing
potential as integrated brownout landing solutions, workload may be
very high for the pilot for obstacle avoidance. One or both pilots'
attention needs to be on the new display during the final stages of
approach and landing--a departure from conventional methods. The
methodology associated with these systems introduces new human
factors hazards, and certainly will require formal training and
acclimation. These systems will require extensive integration into
existing platforms at a considerable cost, particularly on a
large-scale retrofit. The required hardware for radar and ladar
systems can weigh between 30 and 100 pounds [Harrington 2010].
[0047] Researchers from the University of Glasgow conducted a
simulation of helicopter brownout using fluid dynamics software to
model various particle properties and their reactions under
different flight conditions for both single rotor and tandem rotor
configurations. They compared dust simulation results using varying
values of the "thrust-normalized advance ratio" [Phillips 2009].
This important term accounts for main rotor thrust, approach speed,
and descent rate. Essentially, the larger the value, the higher
forward airspeed is during the approach. FIGS. 3-5 illustrate that
the predicted dust formation gains height and is more pronounced
ahead of the aircraft as the approach closure rates become
slower.
[0048] The images in FIGS. 3A, 4A, and 5A show the
three-dimensional flow pattern, and the images in FIGS. 3B, 4B, and
5B show the relative cross-sectional dust density. FIGS. 3A &
3B are for a thrust-normalized advance ratio of 0.29. FIGS. 4A
& 4B are for a thrust-normalized advance ratio of 0.80. FIGS.
5A & 5B are for a thrust-normalized advance ratio of 0.12. As
the forward speed of the aircraft decreases (lower advance ratio),
a larger cloud of dust is raised. Note that the area directly
beneath and in front of the lower nose section (chin bubble area)
has a very low relative dust density in all cases, suggesting that
this can be a key area in which visual contact with the ground can
be maintained given a suitable illumination method.
[0049] Embodiments of the present invention provide improved
illumination to aid pilots in landing rotorcraft and VTOL aircraft
in particulate (light dust to heavy dust) landing conditions,
especially under limited light conditions such as night-time
landings and where tactical considerations require the use of low
light levels to minimize visibility to outside observers. As will
be detailed below, the lighting systems can have multiple modes and
levels to provide good visual assistance to the pilot(s) to enable
them to see the ground with sufficient visual acuity without making
the aircraft excessively visible to outside observers. It should be
further noted that, although embodiments are described for
rotorcraft and VTOL aircraft that are operable to hover and perform
vertical takeoffs and landings, actual landings may not be
vertical. In most examples of DVE landings, the approach is not
vertical. However, the degradation of the visual environment is
still a consequence of the use of a rotating blade or wing surface
to generate lift.
[0050] In some embodiments, additional landing lighting systems
(referred to herein as a "dust-light" systems) can be installed
singly or in pairs. A pair of lighting systems, one on each side of
the cockpit can be particularly useful for a typical cockpit crew
comprising two pilots. Additional systems can also be provided for
other crew members. These can be either mounted to the airframe or
handheld, for example, by a crew member located at an open
doorway.
[0051] In some embodiments, the dust-lights are adapted for use in
conjunction with NVGs. For example, the pilot can look through the
NVGs out of the windshield and cross-check beneath the goggles with
the unaided eye through the chin bubble and/or out of the cockpit
door or door windows; the pilot need not move their head, just
their eyes. Minimal adaptation by the pilots is required; the new
lighting system facilitates landing using methods already familiar
to trained pilots.
[0052] In exemplary embodiments, a system is provided for a Black
Hawk helicopter. The typical altitude below which dust envelopment
occurs is about 50 ft. Below this altitude, pilots may transition
to looking through the chin bubble during an approach. It will be
apparent to one of ordinary skill that the lower the altitude from
which the lights are employed, the less observable the aircraft
will be from the surrounding environment. The lighting system need
only provide enough light to aid the pilot in seeing the landing
zone visible through the chin bubble at distances of 50 ft or less.
In some embodiments, the lighting system is optimized for use below
20 ft. Some observations by the inventor suggest that operation at
20 ft and below provides sufficient light to provide adequate
assistance to the pilot in heavy dust conditions.
[0053] In some embodiments visible light is used of sufficient
intensity that the pilot can see the landing zone with the unaided
eye below his NVGs. The light can be limited so as not to cause
adverse reflections off dust during the approach, particularly
through the NVGs. In some embodiments laser light can be used to
supplement depth perception by providing an identifiable point
where the laser terminates on the surface. The surface immediately
surrounding the laser termination point can be illuminated more
generally, for example, using LED light sources or other low-level
light sources as shown in FIG. 6. In some embodiments the laser
light is omitted.
[0054] FIG. 6 shows the laser 602 as lines of visible light (e.g.,
green and/or red) with a termination point 604 shown as a sunburst
symbol, exaggerated in size for the purpose of clarity. The LED
beam width is represented by the dotted lines 606, and the
illuminated surface is represented by the oval 608 surrounding the
sunburst. Also shown is the normal FOV 610 of the right-hand pilot
through NVGs and the windshield. In some embodiments, the LEDs can
be white and/or green for the unaided eye, looking through the chin
bubble below the NVGs. In some embodiments, the LEDs and/or laser
can be infrared. When infrared light is selected (e.g., for
tactical reasons to reduce visibility), the pilot makes all
observations through the NVGs moving his head as necessary to look
through the NVGs and the chin bubble. In some embodiments, both
visible and infrared light sources are provided, and the pilot can
choose light sources (and intensities) according to the needs of a
particular approach and/or landing. In some embodiments, a green
and red laser can be projected simultaneously to provide a beam
that is visible in and out of dust conditions. Table 1 provides a
reference under which conditions each illumination mode may be
visible. The reference to visibility for the LEDs pertains to the
target surface, whereas the visibility for the lasers pertains to
the beam itself and/or the laser spot projected on the ground.
TABLE-US-00001 TABLE 1 Visibility Characteristics of Light Sources
in Different Conditions No Dust Dust Source Unaided Aided Unaided
Aided LED White X X X X Green X X Infrared X X *Laser Red X X X
Green X X X Infrared X X *X indicates beam or spot is visible.
[0055] The specifications for the lasers and low level light
sources can vary according to the needs of a particular aircraft
and its landing characteristics. The output power can be made
adjustable, either by the pilot directly, or with the assistance of
some form of automated intensity adjustment aided by a reflected
light sensor. An automated system can provide just enough light to
provide a desired reflected light intensity returned to the
aircraft with a maximum allowed level based on tactical
considerations.
[0056] Any laser source providing a beam of appropriate wavelength
and power can be used. In the configuration of Example 1, three
lasers, two visible and one infrared are provided to accommodate
different terrain, particulate, and tactical situations. The pilot
can select whichever provides the best visibility subject to
operating constraints. Typically, Class I lasers with an output
power of 0.5-1 mW are suitable, although other powers can also be
used. These lasers can be semiconductor lasers such as those used
in laser-pointing and laser-sighting applications. A typical green
laser can have a wavelength of about 532 nm; a typical red laser
can have a wavelength of about 650 nm; and a typical infrared laser
can have a wavelength of about 830 nm, although these wavelengths
can vary, and other wavelengths can be used. In some embodiments,
the light from the laser is well-collimated such that the projected
spot size on the ground is substantially constant during approach.
In some embodiments, the laser can be focused or divergent with
either fixed or adjustable focal length/divergence angle. A
converging or diverging beam can be adjusted so that the projected
spot size on the ground changes with altitude and provides an
additional visual cue to the pilot as to current altitude at short
range where conventional radar and barometric altimeters do not
provide adequate precision and accuracy. Astigmatism can also be
deliberately used such that the projected spot has an aspect ratio
that changes with altitude. For example, a cylindrical lens can
provide a different effective focal length along one axis compared
to a perpendicular axis. A round spot will be projected at one
altitude, and the spot will appear to be elongated along one axis
of the other as the altitude deviates from that giving the round
spot. In some embodiments, the focal lengths are adjusted to give a
round spot at termination. In some embodiments two lasers can be
aimed at different angles such that the separation of their
projected spots varies with altitude. In some embodiments the
projected spots coincide when termination is reached.
[0057] The laser spots can provide useful visual cues as to the
location of a surface that may be otherwise difficult to see
through the particulates and low-light conditions. A larger
illuminated area can also be valuable to aid the pilot in landing
at a particular target location, avoiding any local obstacles
either on or above the ground. In some embodiments, the larger
illuminated area is defined by a FOV around the laser spot,
although it is also possible to point the laser spot and
illuminated area independently toward different locations. Any
low-level illumination source can be used, including conventional
landing lights set at low power, although typical aircraft control
systems are not configured to operate landing lights with the small
FOV and low intensities optimal for particulate environments and
tactical or clandestine operations. The power levels for
conventional landing lights and dust-lights can be a more than an
order of magnitude higher than those of an ideal dust-light system
as can the desired FOV. Accordingly, a dedicated dust-light system
can be a preferred implementation.
[0058] In some embodiments LEDs are used and can provide a suitable
combination of power level and controllability. In some embodiments
an array of LEDs of each wavelength is provided. These can be
arranged in any convenient geometric configuration, the ring
arrangement described in Example 1 being only one of many possible
configurations that would be apparent to one of skill in the art.
The minimum total radiant power output should be just sufficient to
provide ground visibility to the pilot as he descends below a
particular altitude such as the 50 ft or 20 ft suggested above for
use with the Black Hawk helicopter. The maximum radiant power
output should be limited so as not to provide more light than is
necessary to assist the pilot, for example, no more than 2, 3, or 5
times the minimum radiant power output. For tactical use, the
illumination level can be further controlled, either manually or
automatically so as to maintain only the minimum level needed at
any given time and location. The illuminated area can be kept small
to match the FOV of the pilot looking, for example, through the
chin bubble. The light assembly can be further shrouded and aimed
so that the light has low visibility to any observer outside the
FOV. In some embodiments the total power for each array of LEDs can
be less than about 10 W or about 20 W depending on the size and
configuration of the particular aircraft. By comparison, the
typical prior art landing lights and searchlights operate at or
above about 600 W and 250 W respectively, and cannot readily
provide the low-level controlled intensities of the dust-light
system, even if it were possible to aim them in a useful direction
for illuminating the surface seen through the chin bubble.
[0059] While light can penetrate particulates to some extent, a
dust-light system can only physically increase visibility to what
may be observed during equivalent dust conditions in daylight.
Dust-light systems can aid in maintaining or establishing outside
references in what would otherwise be total darkness, or
particulate-entrained NVG-green-hued rotorwash.
[0060] In some embodiments, the aim of the dust-light system is
fixed at installation based on an average pilot size and eye
location. In some embodiments, fine tuning of the beam direction
can be provided using a suitable gimble mount with two axes of
adjustment. The adjustment can allow optimization of the aim of the
dust-light system for a particular combination of pilot, seat
adjustments, and aircraft.
Example 1
A Multiwavelength Dust-Light Assembly with Both LEDs and Lasers
[0061] FIGS. 7A-C show views of a design for an exemplary
dust-light assembly. A 5-inch diameter mounting flange has a depth
of about 2-3 in, and a weight of about 5 lbs. Three central
recesses 702 are provided to mount red, green, and infrared
semiconductor lasers. The surrounding recesses 704-708 house the
LEDs by type in concentric rings. From inner to outer rings the
order is infrared 704, green 706, and white 708. The chamfered
outer ring is designed to collimate the LED beam so that it only
illuminates a target area consistent with the FOV available through
a single chin bubble at 50 ft and below. In addition, the outer
ring serves to shroud the light source from outside observation in
a tactical environment. The inner face of the dust-light is further
protected by a scratch-proof, non-reflective, tinted glass which
also aids in reducing outside observation.
[0062] The outer flange of the unit mounts flush to the aircraft
exterior to a fixed flange using four bolts with thread locking
compound, and further sealed around the perimeter of the unit using
standard nonpermanent compound (e.g., PRO-SEAL.RTM. made by
Proseal, Adlington, Cheshire UK). The mounting configuration would
be similar to that of the Electro-Optic Missile Sensors (EOMS) of
the Common Missile Warning System (CMWS), shown in FIG. 8.
[0063] Power can be provided to the back of the unit via a plug
connection 802, supplying 28 VDC from the number 2 DC primary
bus.
Example 2
Aircraft Integration
[0064] In order to adapt a dust-light system to a specific
airframe, the ergonomics of the cockpit layout and nose section of
the aircraft must be taken into account. One of the primary
considerations is the FOV from the pilots' perspective through the
chin bubble. In this example, integration is described for a Black
Hawk helicopter. The chin bubble in a Black Hawk is reasonably
sized, but does not provide much forward looking capability. Rather
it provides more lateral and downward visibility as shown in FIG.
9.
[0065] A superimposed ring 902 shows the approximate center of the
FOV through the chin bubble for the right-hand pilot. When the
aircraft is on the ground, the fixed dust-lights can be aimed at
their respective chin bubble FOV center. The seat position from
which the image in FIG. 9 was captured is full aft, and
mid-position height, in accordance with the design eye point for a
70-inch tall pilot. The design eye point for the UH-60 in
accordance with the Army field manual [Army 2007A], is to have the
ground in view beginning at 12 ft from the nose (with the aircraft
on the ground). Measuring from the approximate pilot's eye
position, the viewing angle ranges are found to be approximately
42-49.degree. down and approximately 18-22.degree. outward. The
seats are capable of adjusting a total of 5 inches fore/aft and
up/down. The anti-torque pedals 904 are shown full forward, but can
be adjusted fore/aft a total of 6.5 inches. The FOV from the left
pilot seat is approximately the same. These measurements cannot
account for every possible combination of height, seat position,
pedal adjustment, and anthropometric variability, but they are
valid for the majority of military aviators given the constraints
of the HH-60L cockpit.
[0066] Visible surface area outside the chin bubble from the
pilot's perspective is approximately 6.5 ft.sup.2 with the aircraft
on the ground. This was measured by placing rigid plastic sheets
marked with square foot gridlines beneath the chin bubble and
estimating the visible area as shown in FIG. 10A. Following the
inverse square law in regard to area, as shown in FIG. 10B, it is
evident that visible area increases by multiplying by the square of
the radius (distance) r, where r is the distance from the pilot's
eyes to the ground along the central FOV axis, i.e., 9 ft.
[0067] At 50 ft altitude, measured from the Earth's surface to the
radar altimeter antenna, the pilot's eyes are 54.5 ft above the
surface; 54.5 ft divided by 9 ft equals 6.05 r, squaring 6.05
equals 36.67, and multiplying this result by 6.5 ft.sup.2 yields
238.35 ft.sup.2. Therefore, the area visible through the chin
bubble at 50 ft altitude is approximately 238.35 ft.sup.2. This is
equivalent to a square surface area of 15.44.times.15.44 ft, or a
circular surface area 17.42 ft in diameter. Note these are
estimates based on specific eye point with the aircraft at a level
attitude. Shifting of the pilots head and changing the aircraft
pitch attitude can alter this figure drastically. But these
estimates can be used to establish a baseline figure for a
preliminary design.
[0068] The dust-light can be located in an area which can readily
provide the proper positioning for the system to work effectively,
while minimizing the required modification to existing airframe
structure. Two primary locations 1102 and 1104 are identified in
FIG. 11. Location 1102 requires minimal modification due to an
existing maintenance access panel. Only the panel itself would
require modification; the dust-light would be directly mounted to
the panel. Alternatively, the dust-light can be provided as a
direct bolt-on replacement for the access panel. The addition of
the dust-light would not interfere with normal maintenance actions
associated with this location. FIG. 12 shows the area located
directly behind the panel at location 1102. Flight control linkages
1202 are visible behind the panel, but are several inches from the
panel itself leaving sufficient room for the dust-light system
hardware. Internal space is, however, more limited than at location
1104. The more significant issue that complicates using location
1102 is that the dust-light must project at a significant angle
relative to the centerline axis of the mounting hole in order for
it to be effective. This would require either angling the face of
the dust light, or adding an angled-mirror modification to project
the beam properly.
[0069] Location 1104 offers placement of the dust-light that is
more aligned with the required aiming direction for the dust-light.
The drawback is that location 1104 would require more airframe
modifications than location 1102. The modifications required would
consist of cutting sheet metal and drilling using a circular
template, which may or may not be considered a unit-level
maintenance action, depending on the organizational resources. FIG.
13 shows the space behind location 1104 from a vantage point within
the cockpit and behind the anti-torque pedals, with an interior
panel removed. The intended location of the sheet metal
modification and dust-light installation is indicated by the circle
1302. The control rod running through the circle is offset above
and to the side of the mounting site, and will not cause
interference.
[0070] If the AN/AVR-2B Laser Warning System is installed on the
aircraft, the associated mounting structure can also serve as a
potential location 1402 for the dust-lights as shown in FIG. 14.
Location 1402 is compatible with achieving the proper beam angle
and is practical in that it only requires modification to an
existing modular component, requiring no direct airframe
modification.
[0071] The dust-lights can be controlled via a rocker switch
mounted on the collective. The collective is shown in FIG. 15,
depicting where several existing light functions can be controlled.
One control option is to replace the existing searchlight rocker
switch 1502 with a split rocker switch, one side for the dust-light
modes, and the other remaining side for searchlight functions. This
placement would be a seamless integration, requiring no change to
the pilots' natural hand placement. The only change would be in
tactile identification of the appropriate switch. Given the vast
diversity of switches available, and the ample size of the Black
Hawk collective control head, it would be a suitable option.
Example 3
An Approach Sequence
[0072] FIGS. 16 and 17 show a photo sequence taken during a single
approach into a heavy dust landing zone. Looking closely, one can
observe the dust formation and visibility in relation to altitude.
FIG. 16A shows the aircraft at 19 ft above ground level; the dust
cloud is beginning to come into view from the cockpit.
[0073] The dust obscures the chin bubble first as the rotorwash
begins to shear material from the surface. As the helicopter closes
on a landing surface, a surrounding wall of dust forms, and the FOV
through the chin bubble begins to clear, as shown in FIG. 16B,
where the aircraft is at 9 ft above ground level. This is
consistent with the dust simulation models shown in [Phillips 2009]
that are reproduced in FIGS. 3-5. As the helicopter continues to
descend, the surrounding dust-entrained air mass begins to
circulate through the rotor system, further degrading visibility as
shown in FIG. 17A, where the aircraft is at 3 ft above ground
level.
[0074] However, visibility continues to improve through the chin
bubble all the way to termination on the ground illustrated in FIG.
17B. The illustrated approach was made to a specific point with low
touchdown speed resulting in about a one foot roll-out. The wind
was from approximately 270.degree. at approximately 20 knots and
the approach direction was 310.degree.. Conducting this approach at
night using NVGs would have been far more challenging, and could
have easily resulted in a go-around. The area beneath the chin
bubble would have been completely dark and would have offered no
outside reference to the unaided eye; the pilot would have had to
repeatedly move his head downward to look through the chin bubble
using his NVGs to gain reference during this critical stage. Making
such head movements is not ideal and potentially unsafe.
[0075] It will be understood that the descriptions of one or more
embodiments of the present invention do not limit the various
alternative, modified and equivalent embodiments which may be
included within the spirit and scope of the present invention as
defined by the appended claims. Furthermore, in the detailed
description above, numerous specific details are set forth to
provide an understanding of various embodiments of the present
invention. However, one or more embodiments of the present
invention may be practiced without these specific details. In other
instances, well known methods, procedures, and components have not
been described in detail so as not to unnecessarily obscure aspects
of the present embodiments.
REFERENCES
[0076] [Army 2007A] Field Manual 3-04.203 Fundamentals of Flight,
Dept. of the Army, Washington, D.C. [0077] [Army 2007B] Training
Circular 1-237Aircrew Training Manual, Utility Helicopter, H-60
Series, Dept. of the Army, Washington, D.C. [0078] [Army 2008] Army
Regulation 95-1 Aviation Flight Regulations, Dept. of the Army,
Washington, D.C. [0079] [Army 2010] Technical Manual 1-1520-253-10
Operator's Manual for HH-60L Helicopter, Dept. of the Army,
Washington, D.C. [0080] [Army 2013] Training Circular 3-04.33
Aircrew Training Manual, Utility Helicopter, H-60 Series, Dept. of
the Army, Washington, D.C. [0081] [Harrington 2010] Harrington, W.
et al., "3D-LZ Brownout Landing Solution," American Helicopter
Society 66.sup.th Annual Forum, Phoenix, Ariz., Ann. Forum
Proc.--AHS, 66 (2010), 983-1001. [0082] [Phillips 2009] Phillips,
C. & Brown, R. E., (2009): "Eulerian Simulation of the Fluid
Dynamics of Helicopter Brownout," Journal of Aircraft, 46 (2009),
1416-29, doi: 10.2514/1.41999.
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