If I were asked to choose between a heavy dose of
spatial disorientation in IMC or a kick to the stomach, I
would choose a kick to the stomach every time. To me,
there is no worse feeling than trying to fight-off a case of
the Leans while flying inside the proverbial “ping-pong ball.”
Spatial Disorientation, or simply Spatial-D, is one of a number
of physiological threats to flight that target the pilot’s
ability to successfully command and
effectively operate an aircraft. Others
include the physiological effects of
altitude, performance threats, and
night/visual illusions.
Spatial-D is especially heinous in
that it often goes unrecognized.
To be in full operational control of
an aircraft, we are in command of
that aircraft when we know what
the aircraft is doing, and why it is
doing it. We have lost command if
we know what the aircraft is doing,
but not why the aircraft is doing
it. We have lost control if we don’t
recognize what the aircraft is doing.
That loss of situational awareness
generated by an onslaught of
Spatial-D degrades a pilot’s
command of the aircraft, and may
well lead to loss of aircraft control. In fact, the United
States Air Force has had two recent high-profile fatal
mishaps where spatial disorientation was determined
by the Air Force Accident Investigation Board to be a
contributing factor in loss of aircraft and aircrew:
- An F-15E Strike Eagle was lost on a night sortie
in South West Asia after the pilot lost awareness
of aircraft attitude due to Spatial-D, and rolled
the aircraft inverted at low altitude. The backseater
Weapons Systems Officer (WSO), who
had maintained spatial awareness, attempted
unsuccessfully to recover the aircraft and had to
initiate ejection.
- An F-16 crashed into the Gulf of Mexico on a
training sortie after the pilot lost awareness of
attitude due to Spatial-D brought on by vestibular
and visual illusions.
Cirrus Pilots Too
Jet pilots are not the only aviators vulnerable to Spatial-D
and loss of situational awareness. A close look at Cirrus
fatal mishaps and successful CAPS events show that
disorientation and loss of situational awareness in IMC,
or at night, produce the loss of control outcomes we wish
to avoid. Of the 56 fatal Cirrus accidents with a loss of
control occurrence, 25 accidents (45 percent) involved
IFR flight. (See the safety article, “COPA/Cirrus Aircraft
Examine Loss of Control Accident” in Cirrus Pilot January/
February 2016, pages 46-50.)
Only three of these were landing
accidents, suggesting that proficiency
issues with instrument
flying contributed to the loss of
control. Of the 63 CAPS saves, 12
of the saves (19 percent) contain
indications of pilot disorientation,
loss of situational awareness,
and loss of command that compelled
the pilot to appropriately
activate CAPS.
So why does this happen? What
types of disorientation are
there? How do I prevent or avoid
disorientation? If I experience
disorientation, how do I recover?
Sensory Physiology
In order to understand these
physiological threats to flight,
we must understand our internal
“AHRS” (Attitude Heading and Reference System). Our
system is designed and optimized for five to six feet AGL
and up to only a few knots of groundspeed. Maintaining
orientation in flight at higher elevations and faster speeds
is a challenge.
There are a variety of sensory stimuli inputs that vary in
magnitude and direction. We humans have four primary
senses that help us determine positional awareness
and maintain orientation: vision (eyes), proprioception
(muscles/joints), vestibular (middle ear), and hearing
(inner ear).
Vision Sensing
By far the most important is our vision. It provides up to
80 percent of the information to the brain that builds our
situational awareness and it functions at both conscious
and subconscious levels. Peripheral vision allows us to maintain positional awareness as we walk through the
hallway while paging through our smart phone or with
our nose down in an app.
When flying as pilot in command and entering IMC, we
are instantly deprived of these enormously important
peripheral vision cues that help us maintain attitude.
Instrument pilots efficiently and effectively (mostly)
transition visual processing to a narrower field of view,
coping by maintaining spatial awareness solely with
reference to an artificial attitude instrument, although
those gigantic PFD attitude indicators provide semiperipheral
vision cues when compared to the small threeand-
one-fourth-inch gyros of the recent past.
Proprioception Sensing
Try this: ask your favorite CFII to take off his Ray-Bans,
stand up on one foot, cover one eye, and maintain balance.
That’s no sweat ... too easy. Now ask him to cover both
eyes and watch how long it takes until his balance erodes.
reliant on a few other senses that aid our brain in providing
attitude and positional awareness. The proprioceptive, or
somatosensory system, uses our body’s tactile sensors in
our muscles, joints, ligaments, and skin, but provides less
than five percent of the orientation information to our brain.
can provide false sensations of pitch change with linear
acceleration. Speeding up will increase pressure on
your back creating a false sensation of nose-up pitch,
while deceleration will do the opposite, providing the
false nose-down feeling. Full-motion flight simulators
take full advantage of these sensations to stimulate
our senses into providing that full-throttle acceleration
take-off run “feel.”
Vestibular Sensing
The middle ear’s vestibular system provides up to
15 percent of the attitude information processed by
our brains. The two main components consist of the
semicircular canals, which detect changes in angular
acceleration, and otolith organs, which detect changes
in linear acceleration.
Although functioning on the subconscious level, false
vestibular input can be extremely difficult for the brain
to ignore. The semicircular canals provide the brain the
equivalent of a three axis gyro, providing pitch, roll and
yaw cueing as fluid moves through the half-circular,
interconnected tubes.
Hearing Sensing
While hearing provides limited attitude information
to our brains, some pilots report hearing airspeed
increases due to wind noise. That in turn provides
useful cross-check information to recognize loss of
situational awareness.
Vestibular Shenanigans
Designed to work on the ground,
our internal AHRS, especially our
vestibular system, can be tricked by
motion in flight.
There are two categories of illusions,
depending on which subsystem is
stimulated. If the semicircular canals
are stimulated, then the illusion is
a false sense of spinning/turning
while actually being stationary, or
the false sense of being stationary
when actually turning/spinning.
These illusions are caused by the
inertial delay in the semi-circular
canals. If the otolith organs are
stimulated, then it is categorized
as a somatogravic illusion due to
acceleration.
Let’s take a quick look at some of the
vestibular illusions:
The Leans
The most common vestibular illusion
experienced in flight is a somatogyral
illusion caused by a return to level
flight after an unrecognized roll into
a turn or a return to level flight after
a continuous bank. The result is the
pilot senses a turn or bank in the
opposite direction of the actual bank
as the inertial difference of the fluid
in the canal is registered.
Coriolis Illusion
This illusion starts with the simultaneous
stimulation of two or more
semicircular canals. Often caused
by sudden turning or tilting of the
head, such as quickly looking down
at a circuit breaker, kneeboard, or
Facebook post (just kidding, not really),
while the aircraft is turning. This
illusion results in the sensation of
tumbling about the pitch, yaw, and
roll axis simultaneously.
Graveyard Spiral
A graveyard spiral descent develops
as a result of the same illusion
caused by the Leans, but progresses
as the pilot returns the aircraft to
perceived level, which is actually
a bank. Without the additional lift
component in the bank, the aircraft
descends and the pilot perceives
a level descent and adds control
backpressure, tightening the turn
and worsening the situation by
losing even more
Pitch-up Illusion
A somatogravic illusion caused
by a sudden acceleration in level
flight where the pilot perceives the
nose of the aircraft to pitch up,
resulting in the pilot intentionally
or unintentionally pitching the nose
down. Proprioceptor cues described
above can exacerbate this illusion.
Pitch-Down Illusion
Another somatogravic illusion, caused
by sudden deceleration where the
pilot perceives a nose down pitch
when in level flight, resulting in the
pilot erroneously adding control
backpressure.
Any of these vestibular illusions
can at least trigger a “Holy Crap!”
moment, or worse, cause a pilot to
become quickly disoriented, lose
situational awareness, and then lose
command and control of the aircraft.
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Specialties Services promise.Awareness of the vestibular aspects to spatial awareness
is the first step in maintaining command of our aircraft.
Mnetal Prcosesing
Complicating the complete situational awareness model
are some unique cues provided by our experiences and
training.
Take the paragraph title above. On first look, your brain
processed the term mental processing, although it was
intentionally typed incorrectly. We often overlook some
key indicators that could help us build our situational
awareness and maintain orientation. Expectancy cues
can cause us to inaccurately perceive our surroundings
or our aircraft’s condition or position.
This can manifest itself in a number of ways. For example,
building a mental arrival picture to a landing runway that
is opposite or 90-degrees off of the actual runway in use
can complicate a pilot’s situational awareness. Overreliance
on automation can produce some discernable
expectancy issues.
How often has auto-slew, NAV sequencing, or autopilot
behavior gone unnoticed?
Monitoring the autopilot and muttering into the intercom
“uh ... what is George doing” is a good thing! It means you
were situationally aware and ready to re-take command
by applying a correction or switching automation modes.
Task saturation degrades mental processing and effective
command. Channelized attention has equivalent effects.
Fixating on just altitude, for example, erodes our capacity
to command the other aspects of basic instrument attitude
flight. If George is doing something we were not expecting,
or a sudden caution light demands immediate action,
our excess mental processing capacity and command
performance suffers.
Additionally, to keep mental processing at peak levels, it
is important to keep cockpit distractions at a minimum.
Our Defenses: Prevent, Avoid, Recover
So what is our best defense against Spatial-D and loss
of situational awareness?
There are multiple overlapping and integrated practices
and procedures to fight off Spatial-D and contest degraded
situational awareness. Good spatial orientation is a result
of effective perception and integration of primary visual
cues, namely your PFD and flight instruments.
I know we have heard it before, but trust and understand
your instruments. Utilize all of your avionics tools, including
tiered levels of automation and moving map displays set at
appropriate, discernable settings for range and orientation.
We can work to prepare ourselves for the severe operating
environment of instrument flight. Understand the
vestibular and visual aspects of spatial orientation to
better recognize and avoid the traps presented by these
physiological threats. Brief the operational and environmental
challenges to each segment
of the flight we are executing. Be
cognizant of the effect of dynamic
forces in flight and recognize the
forces at play. For example, being
aware that a visual climbout that
enters IMC in a smooth and sustained
turn could induce the Leans
as you level the wings might entirely
eliminate or shorten the duration of
the vestibual "discomfort."
Build and maintain your instrument
flight proficiency through realistic
and challenging recurrent training. To
prepare for the variety of vestibular
illusions, I highly recommend
practicing under the hood with a
safety pilot at night. The low light
and complete lack of periphery
visual cues seems to enhance the
Spatial-D awareness challenges and
can induce mild somatogyral and
somatogravic symptoms.
Work on improving your instrument
scan. Actively visualize the horizon
from your primary attitude display
out into your periphery instead
of passively allowing conditions
outside the aircraft to impact your
subconscious perceptions. Train and rehearse unusual attitude recoveries to the point that they
become innate procedures.
During practice and training, make mental notes on spatial
awareness conditions that affect you. Before entering
those conditions again, remind yourself of your tendencies
in these situations and develop a plan to alleviate the
effects. Perhaps this means reducing roll rate during roll
in/out of turns and reducing pitch rate and rate of power
application/reduction during climb initiation and level offs.
Also, always adhere to standardized operating procedures
found in the Flight Operations Manual (now the iFOM)
from Cirrus Aircraft. Developing and practicing solid
workflows will enhance task prioritization and execution,
boost mental processing performance (through reduced
task saturation), and enable solid situational awareness.
Demanding conditions and challenging instrument
profiles become relatively easier to handle as our
workflows gain consistency.
Actual recovery from a Spatial-D episode or loss of
situational awareness first requires that it be recognized.
Assuming we have regained command of the aircraft,
I advocate the 3C’s method for recovery: Climb, Cope,
and Confess.
First, get the aircraft climbing away from obstacles or
terrain (or use the blue LVL or Straight-and-Level buttons
on the autopilot to stop terrain closure!). Then prioritize
tasks to regain situational awareness through use of your
PFD, MFD, or other flight instruments. Lastly, confess that
it’s happened to you. With an appropriately rated (and
proficient) pilot in the other seat, perhaps we transfer
command before it’s too late: “Hey man, you have the
aircraft ... I’m tumbleweed.” This may also involve resetting
aircraft position and altitude and should definitely involve
reaching out to air traffic control for assistance.
Being prepared to handle the multitude of sensory inputs
while flying in the IMC environment will help us better
manage the command tasks of flying solely by reference
to instruments.
Keeping the aircraft shiny side up with no false turning
sensation feels good...and much better … than a kick in
the stomach.
This article was initially published in the May / June 2016 issue of COPA Pilot.