A Kick to the Stomach


Posted on Feb 15, 2021 by Karl Fischbach

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:

  1. 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.
  2. 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. At Aircraft Specialties Services we know Starter Adapter failure can be a truly frustrating experience. A perfectly good aircraft that just sits on the ramp. This usually happens at the worst possible time, when it’s sitting on someone else’s ramp for example. We also know making repairs with a factory new Starter Adapter is a very costly proposition. That is why we stock a full range of overhauled Starter Adapters ready for immediate exchange. Our technicians have years of experience rebuilding these Continental adapters, using the highest quality parts. We can also overhaul your own core, if you prefer, and get it back to you quickly. Give us a call; we can get you back in the air fast and at a price you can afford! That’s the Aircraft 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.

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