1. I
n our business of flying, “The Per-
fect” is very much still the enemy
of “The Good,” especially when it
comes to attaining dependable, eco-
nomically feasible and broadly available
all-weather operations equipage. The
good in focus here are enhanced vision
systems (EVS).
After years of direct involvement in
EVS development and application, I can
say without qualification that today’s
thermal image-based EVSs are very
good. Remarkable, even. In helping pilots
see through the murk and the dark, they
instill confidence and enhance opera-
tionalsafety.Forhelicopterpilotslanding
at night at a remote location, an EVS can
be the only means of spotting obstacles
and ground personnel.
And if you are appropriately trained,
and your aircraft is equipped with a cer-
tified EV sensor coupled to a head-up
display (HUD), you can legally descend
anadditional100ft.orsobelowpublished
precision approach minimums. This ca-
pability is permitted only if at published
decision height, the flying pilot can “see”
the “runway ” through the EVS image
superimposed on the HUD. If, after de-
scending, the runway is not visible to the
pilot using normal unaided human sight,
a missed approach is required.
The ultimate goal — perfection, if you
will — is the ability to safely conduct air
and ground operations in zero-zero con-
ditions as a matter of course. And no,
EVS can’t deliver that. Yet.
EVS is currently available in three dis-
play configurations, each with a different
acronym, price tag and certification. All
offerimprovedsituationalawarenessdur-
ingtimesofreducedvisibilityduetodark-
ness or weather, or both and, as noted,
one system provides lower minimums:
EVS: Enhanced Vision System. A
stand-alone thermal imaging camera
that sees infrared energy emitting, or
radiating, from objects and forms a real-
time video image that is displayed on an
MFD or dedicated video display screen.
The system’s primary benefit is improv-
ing situational awareness. At night, an
EVS eliminates the visual effects of
darkness, turning it into day on the dis-
play, and enabling the pilot to see and
avoid clouds at night. During the day, the
system enables the pilot to see through
smoke, haze and smog.
EFVS: Enhanced Flight Vision System.
A thermal imaging camera that sees in-
fraredenergyradiatingfromobjectscou-
pled with and displayed on a HUD flight
guidance system. The primary benefits
of this more sophisticated arrangement
is its approval for primary flight guid-
ance in IFR flight, and it can provide
lower minimums. And it, too, enhances
the pilot’s situational awareness.
CVS: Combined Vision System. A ther-
mal imaging camera combined with syn-
thetic imagery, whereby the real-time
EVS depiction is presented as a trans-
lucent overlay on the database-derived
synthetic visuals on the PDF. The main
benefits of this combined system is the
visual addition of transient obstructions
in the approach and landing zone. Such a
system can be regarded as a preliminary
step toward a future “Verified Synthetic
Vision System” so accurate to allow pre-
cision landings followed by taxiing to the
ramp in zero-zero conditions.
EVS, EFVS and CVS can all include
sensors in addition to the IR sensor, such
as visible light sensors. Data from each
senor is electronically “fused” into and
contributes to the image. This “fusion” of
data from multiple sensors is a key com-
ponent of advanced systems.
Today’s EFVSs are expensive —
roughly $800,000+ — components in
avionics suites but a welcome investment
when you need an extra 100-ft. descent
on the published DH — particularly if
it’s at the end of a transoceanic flight, or
there’sahigh-valueperishable,orchiefof
state, in back.
A simple EVS image on the MFD or
stand-alone display can boost the confi-
dence of an IFR-rated private pilot flying
alightsingleortwinatnightorinmoder-
ateIMC.Onaclear,moonlessVFRnight,
a straight EVS will turn night into day on
the display, enabling the pilot to see the
surrounding terrain, roads, buildings,
etc., thus eliminating any night flying
sweats. And it will turn a special VFR
night into a special VFR day, and maybe
add a little range to the reported SVFR
visibility as an added benefit. The price
for being able to see the otherwise un-
seeable ranges from about $25,000 to
$130,000.
A New Way to See Seeing
To better understand the practical per-
formance expectations of current EVS
technology and to appreciate the net op-
erational improvements of future gener-
ation systems, it’s helpful to have a basic
understanding of how IR imaging works
and the limitations that physics imposes
on imaging with this energy source.
To begin, thermal imaging works dif-
ferently than visible light imaging —
that is, the way we see.
Take a look at the accompanying il-
lustration. This shows what portion of
A Sight
to See
EVS is gaining
in popularity for
good reason
By Lou Churchville lou@churchaero.com
technology
56 Business & Commercial Aviation | August 2015 www.bcadigital.com
Gulfstream G280 Planeview EVS
image displayed on a HUD.
Gulfstreamt

2. 58 Business Commercial Aviation | August 2015 www.bcadigital.com
(LWIR) and, to a slightly lesser degree,
mid-wave IR (MWIR) are generally con-
sidered the best for imaging the world.
Short-waveIR(SWIR)camerashadbeen
too expensive and export of the technol-
ogy by U.S. manufacturers limited under
International Traffic in Arms Regula-
tions(ITAR),makingthemcommercially
difficult to deploy.
None of the other IR frequencies sepa-
rating those three can penetrate to the
earth’s surface because gases that are
common constituents of our atmosphere
absorb the energy at their wavelengths.
You may encounter the term “near IR”
(NIR). This refers to the segment of en-
ergyfromtheeye’scutofffatabout0.65µ
to about 1.0µ. This energy is technically
considered “visible light,” but our eyes
are not tuned to react to it.
Infrared energy is blocked by glass,
so the IR energy generated by a glowing
tungsten filament in an incandescent
light is blocked by the glass bulb enclos-
ing the filament. Sometimes, if runway
lights have been on long enough for their
heat to migrate to the light’s assembly,
that hot metal base will show up on a
long-wave/mid-wave EVS display as a
glowing light. The new light-emitting
diode (LED) arrays now being installed
at many airports emit visible light with
almost no “heat,” so they are invisible to
LWIR and MWIR sensors.
Neither LWIR nor MWIR will see,
register or receive visible light. MWIR
cameras can be “stretched” to see a little
into the visible band but then become
subject to “blooming,” a term describing
anincursionintothefieldofviewbyasig-
nificantly stronger source of energy that
slowly radiates out from it. So, when the
sun goes down and the infrared energy
it continuously generates stops raining
down on the now darkened area of earth,
that energy absorbed in the rocks, trees,
concrete, grass, cars and buildings radi-
ates out, albeit at a different rate, accord-
ingtothematerial’stemperature,density
and molecular structure.
Of course, if you are looking at some-
thing that is generating its own heat —
like, say, Jessica Alba — that object will
glowlikeabeaconagainstthebackground
of stuff radiating absorbed energy.
An infrared camera sees the energy
difference of each surface and converts
the minute temperature variance from
the object’s various surfaces into an im-
age. Different temperatures are usually
depicted in shades of grey, representing
rates of IR radiation emitted from the
substances in the camera’s view.
There are three segments in the IR
portion of the EM spectrum that are
useful and, curiously, are fairly evenly
spaced along the continuum. These seg-
ments are defined by the wave sizes in
microns (µ): long-wave IR (8.0 to 14.0µ);
mid-wave IR (3.0 to 5.0 µ); and short-
wave IR (1.0 to 1.5+µ). Long-wave IR
the electromagnetic (EM) spectrum
our eyes register and the relationship
of the other frequencies to each other.
Yes,lightwavesarepartofthespectrum,
which also includes lower frequency ra-
dio and television waves, microwaves
andradar,infrared(IR),visibleandultra-
violet “light,” on up through X-rays, then
gamma rays and, finally, cosmic rays.
Think of your eyes as mini-radar sys-
tems, tuned to this small “visible” por-
tion of the EM frequency spectrum,
registering and resolving into an image
the streaming photons (visible light)
reflecting off objects in the world. The
frequency we call the visible portion of
the EM spectrum reflects off most of the
stuffonthisplanet—stuffweneedtosee
to avoid, to survive and to thrive — ev-
erything from the Alps and Jessica Alba
toairportrunways.Accordingly,humans
andotheranimalsevolvedeyesthat“see”
that portion of the spectrum.
But unlike radar, human eyes do not
generate and project the energy that re-
flects back to create the image you see —
our eyes rely on an outside source, such
as the sun, landing lights or even star-
light as amplified by night-vision goggles
(NVG).
When something like a closing door
or light switch “turns off” the stream of
reflected photons or blocks or scatters
it, as does a window shade or fog, we can
no longer see objects clearly because
all light is absent, or the images are
blocked, or because the existing light
gets scattered on the way to our eyes by
haze, smoke or the fog’s tightly clustered
water molecules.
By contrast, infrared energy, which
occupies another portion of the EM spec-
trum, does not reflect off most stuff.
Rather, it is absorbed by matter and then
technology
Rockwell Collins EVS 3000 image combined
with SVS and displayed on a HUD.
Rockwellcollins
max-viz
Basic Max-Viz EVS for situational
awareness in a King Air with a Pro Line 21
MFD display.

3. www.bcadigital.com Business Commercial Aviation | August 2015 60
altitudes, it does not eliminate missed
approaches entirely. Sometimes (maybe
more than sometimes) the fog is just too
thick for the EVS to pick up the runway.
This performance issue, coupled with
the burgeoning switch among airports
(especially in Europe) from incandes-
centtoenergy-efficient,long-lastingLED
lighting, threatens to further degrade
the dependability of the MWIR single-
spectrum-based EFVS.
For years, some airframe and sen-
sor manufacturers invested in the cur-
rent technology have lobbied the FAA
lighting committee to include a thermal
generator in the specifications for new
runway LED installations. There’s been
resistance to the idea since “stuffing an
electric hair dryer” in an LED array is at
odds with the new lights’ economic and
environmental benefits.
Current and Coming
Enhanced vision systems are clearly a
boontosafetybyprovidingpilotswithen-
hanced situational awareness in general
and, with EFVS, additional landing cred-
its. The systems help reduce weather-
caused delays and diversions.
The technology turns night into day
— delivering a black-and-white real-
time video stream of the world as you
fly over it. It lets pilots see through
haze, smog and smoke as well as mist
and light fog. What exists is good, but
what’s coming is even better as avionics
engineers pursue two very important
technological strategies.
The first is multispectral EVS sen-
sor assemblies, with multiple cameras
each discretely tuned to one of several
frequencies on the EM spectrum. The
information from each sensor
will be electronically fused to
deliver a composite image com-
prising the best data from each.
The second strategy is to
develop advanced image pro-
cessing software, capable of
real-time teasing of every bit
of useful data out of the sensor
packs for highest resolution and
obscurant penetration. Early
releases are being test flown
now and are expected to pro-
vide good or even significant
improvement over mid-wave
cryo-cooled generation one
sensors. These will likely incor-
porate HUD systems for ap-
proaches while switching to the
MFD for situational awareness
and taxiing in low visibility.
Today’s combined EVS and SVS tech-
nology is a marvel but won’t provide the
zero-zero operational ideal performance
without further refinement. First, GPS,
which helps drive the synthetic image,
does not have the accuracy necessary for
vertical guidance to touchdown. Second,
the geographic and topographical data-
basesattheheartofsyntheticvisionhave
errors resulting from atmospheric inter-
ference and other impediments encoun-
tered during the space shuttle’s detailed
scan of the earth’s surface.
EffortsareunderwaytoapplytheEVS
component of CVS to correcting/elimi-
nating the errors resident in SVS depic-
tions of the world. That would open the
doortoapossiblehead-down,orhead-up,
display option of a synthetic world image
thatisexactlyalignedwiththerealworld,
including the depiction of transient ob-
structions in the aircraft’s path — think
Bambi — and enable approach to landing
through touchdown, rollout and taxi to
the ramp in zero-zero conditions.
Technically zero-zero operational ca-
pability exists today but not with eco-
nomicallyfeasibleunclassified hardware.
Progress is being made on both fronts
and, ultimately, a HUD integrated with
a Combined Synthetic Vision System,
or a Combined Synthetic Vision System
embedded in the windscreen will be key
to perfection: landing an FAR Part 25
transport or medical helicopter in zero-
zero, as though conditions were clear
and a million. BCA
causes the image to wash out
details. You can liken it to the
impact on your vision after a
camera flash in your face.
Blooming occurs in a day-
time approach through fog
where the solar light back-
scatter conflicts with the
sensor, or when a bright light
suddenly comes into the field
of view and the EVS image
processing software strug-
gles to balance the exposure.
The software is improving
steadily, but image detail can
be compromised by blooming
on short final, when you need
it the most.
Meanwhile, SWIR holds
promise. Uncooled SWIR
sensorsarenowcomingdown
in price. In addition, security schemes
are being incorporated into the technol-
ogy that precludes its surviving removal
from an EVS assembly. That makes the
component viable from a cost/benefit
standpoint as well as becoming export-
able in accordance with ITAR regula-
tions.
Most EFVSs in service today utilize
mid-wave sensors that are cryogenically
cooled by liquid nitrogen refrigeration to
very low temperatures to gain the sen-
sitivity to see the minute temperature
differences required to image the world
via thermal sensing. When developed,
the award-winning cryo-cooled technol-
ogy for IR sensing was the leading edge
of technology and the best performing
means of thermal imaging.
Compared to new, uncooled sensors,
the cryo-cooled units are heavy, expen-
sive, require pesky maintenance and in-
volve significant cooldown times before
they can operate. Mind you, the microbo-
lometer (un-cooled) sensor technology
is on a par with the cooled sensors but is
lagging in deployment due to the invest-
ment required in time and money to win
certification.
Still, it was these cryo-cooled sensors
that broke the certification barrier for
landing credits — a big technological
and regulatory leap forward — and
cleared the way for a new generation
of uncooled multispectral sensors that
will weigh and cost less while deliver-
ing lower minimum approaches, and
eventually — say, a dozen years or more
from now — zero-zero ground and flight
operations on a regular, reasonably reli-
able, and affordable basis.
A drawback problem with today’s
EFVS is that, while it can reduce descent
To see a video on EVS from Gulfstream
Aerospace click here in the digital edition
of BCA or go to
www.bcadigital.com/evs_gulfstream