Vertigo in Flight - Spatial Disorientation (SD)

Vertigo in Flight - Spatial Disorientation is one of the dangerous situations that pilots will always encounter in flight. It is vital that pilots recognise this hazard in all its aspects. The subject of vertigo is taught in ground courses in flight schools and units and taught to pilots. The flight doctors of the air bases also have a great duty in this regard. In order to contribute to the knowledge of my fellow pilots about vertigo, I thought it would be useful to prepare an article about the vertigo incidents I have experienced in my flying life, the causes of vertigo and the psychology of pilots and share it with my fellow pilots. While preparing this article, I benefited from the information notes I obtained from Prof. Dr. Muzaffer Çetingüç, Retired Air Medical Colonel (former base flight doctor and President of Eskişehir Physiological Training Centre) and Dr. Engin Demir, Air Space Medicine Specialist. 

The definition of vertigo is given on the VERTIGO page of the "Aviation Medicine Association" document as follows: "Vertigo in flight, Spatial Disorientation (SD) is a condition that pilots encounter many times in their flight life. It occurs in clouds, very hazy weather, or night conditions where there are no visual references required for flight in the air and occurs as a result of the weakness of the pilot's vestibular balance system in the inner ear. It is a phenomenon that is not related to the flight hours, but is present for pilots of all ages and experience and will cause the aircraft to enter an abnormal condition if corrective actions are not taken". 

ILLUSION IN THE AIR

Spatial Disorientation-SD (Spatial Disorientation Disorder) is the inability of the pilot to accurately perceive the movement and position of himself/herself or the aircraft he/she is flying in relation to the plane of the earth or to another aircraft in line of sight. In cases where the position of the aircraft is managed or attempted to be managed according to the pilot's sensory illusions and illusions, there is a great danger and the flight may result in an accident-crash if the control is not ensured.

Human beings are functionally adapted to live under an average gravitational force of 1G on earth. Under normal conditions, when a human being is under the influence of gravitational force on the earth, he/she maintains his/her position and balance by integrating and interpreting the sensory data inputs obtained through 80% eyes, 15% vestibular system, (inner ear semicircular canals and balance organs) and 5% deep sensory organs in a certain harmony in the central nervous system. The Proprioceptive System (Proprioceptive System) sends messages to the brain by sensing the direction of the load on the body through the pressure-sensitive deep sensory cells located between all joints, in the muscles and under the skin. In a standing person, the gravitational force in the direction of the head to the foot is sensed by the cells in the joints and the soles of the feet, and the position of the body is reported.

In the flight environment, changes in the movement, speed and position of the aircraft used in an environment where external visual references are complete, inadequate or absent, and inadequate or incorrectly perceived visual references disrupt this harmony; Therefore, there is a situation where normal physiological orientation cannot be provided or there is difficulty in providing it. For this reason, it is inevitable that the aircrews have problems in maintaining their spatial orientation in the flight environment, where they are exposed to movements of varying intensity, duration and direction, and a number of visual illusions.

THE RELATIONSHIP BETWEEN THE PILOT'S SENSATION OF TINNITUS AND THE INNER EAR ORGANS

It is very striking that there is a similarity between the position and function of the semicircular canals in the inner ear, which provide the balance of the human being together with the organs of vision and deep senses, and the position and function of the three axes of an aircraft passing through the centre of gravity.

An aircraft makes yaw movements around the long axis, which is one of the three axes passing through the centre of gravity, glides and climbs around the horizontal axis, and yaw movements around the vertical axis. Similarly, the position of the semicircular canals in the inner ear around three different axes is used to perceive movements similar to the movements around the axes in an aircraft. (The above illustrations show the position of the semicircular canals in the inner ear on the left and the position of the axes passing through the centre of gravity of an aircraft on the right).

Spatial Disorientation is analysed in three different types according to the pilot's reaction to the sensory illusion he/she is experiencing. (In the rest of the article, Spatial Disorientation will be abbreviated as SD).

Type 1 (Unnoticed) SD: 

This is the type of SD where the pilot is not aware that he/she is flying in an abnormal position or experiencing disorientation. There is something wrong with the flight, but the pilot does not realise that he is experiencing SD and continues to control the aircraft according to his perceptions, which he thinks are correct but are in fact incorrect. This is the most dangerous type of SD and is insidious and usually results in an accident. Type 1 SD is the most important cause of CFIT (Controlled Flight Into Terrain) accidents, where the pilot flies without realising that he is losing altitude towards the earth and the flight ends in a crash.

One of the most typical examples of fatal accidents caused by Type 1 SD is the plane crash in which John F. Kennedy Jr, son of President John F. Kennedy, lost his life on 16 July 1999. The accident happened as follows: J. F. Kennedy Jr. took off from the airport in Essex County, New Jersey, with his wife and his wife's sister in a single-engine, propeller-driven Piper PA-32R Saratoga model aircraft, without taking a second pilot, at night, in a hazy weather with no moonlight, to go to the airport on the island of Martha's Vineyard, 200 miles away. The plane crashed into the ocean 7.5 miles from Martha's Vineyard airport. Three days after the accident, the wreckage of the aircraft was found 37 metres deep in the sea by the search and rescue teams of the US Navy and the wreckage was removed. During the examination of the Flight Data Recorder (FDR) found in the wreckage of the aircraft, it was determined that the accident occurred due to the pilot's Spatial Disorientation.  On the date of the accident, John F. Kennedy Jr.'s total flight time was 310 hours and his total night flight time was 36 hours. According to the examination of the FDR records by the Accident/Destruction Committee, it was determined that the pilot approached Martha's Vineyard airport at an altitude of 3.000 feet, descended to 2.000 feet for a while, at this altitude, the aircraft swerved to the right and left, and after gaining and losing altitude, the aircraft dived at a steep angle of 90 degrees and hit the waters of the Ocean at that steep angle. A sentence in the Accident/Destruction report contains the following statement: "If the pilot is not experienced in the use of "Gyroscopic" flight instruments in instrument flight, he has difficulty in understanding the position of the flight and, through a chain of errors, hits the ground with a "graveyard spiral", usually in a steep dive".

Type 2 (Recognised) SD: 

This is the type of SD where the pilot is aware that he/she is flying in an abnormal position or experiencing disorientation. There is something wrong in the flight and the pilot's perception of the orientation does not correspond to what the instruments show. Since the pilot is aware of this abnormality, he/she tries to get rid of this situation by applying the procedures to combat SD. Pilots describe this situation as "being vertigo" among themselves. As mentioned here, pilots use the term Vertigo instead of Spatial Orientation in everyday language. In my articles, I prefer the term vertigo, which pilots use in daily language.

As you will notice in the above paragraph, the pilot in a Type 2 SD condition does not make the same mistake as the pilot in a Type 1 SD condition, but tries to get rid of this condition by realising the abnormality he/she is experiencing and applying the method of combating SD. I have occasionally experienced vertigo in cloud and night conditions in jet training and combat jet aircraft in which I have served in my flying life, and I have landed safely by relying on the instruments and applying the necessary procedures. When I examined the information notes prepared and sent to me by Prof. Çetingüç and Air Space Medicine Specialist Dr. Engin Demir, I realised that the type of vertigo I experienced at night and in clouds falls into the Type 2 SD category with its scientific definition. 

Type 3 (Incapacitating) SD: 

This is the type in which the pilot experiences a state of incapacitation during the flight to the extent that he/she is unable to continue the flight for any reason. The occurrence is severe enough to prevent the pilot from reading the indicators and obtaining a stable view of the external environment, in case of inner ear balance organ errors, the eyeballs involuntarily move left and right and cannot focus on the objects to be looked at. Reflexes may occur at a level that prevents the control of the aircraft, and even pilots may become incapacitated to the extent that they cannot make healthy decisions and control the aircraft due to the excitement they experience.

The most important feature of Type 3 SD is that the pilot is aware that he/she is experiencing SD, but cannot do anything to overcome it and regain control. In some of the illusions and sensory illusions defined and included in the concept of SD, some sensory illusions similar to the feeling of dizziness (such as vertigo) may be experienced. In another illusion, during angular acceleration/acceleration, the pilot feels as if he/she is moving in the opposite direction of the acceleration movement, and during the climb or dive movement of the aircraft, the minimal movement of the eyeballs in the opposite direction due to the inertial force causes the illusion that the aircraft is climbing or diving more than it is. False climb and dive sensations may also occur during sudden acceleration/deceleration. The pilot may be fooled by this illusion and give unnecessary and incorrect correction controls and crash the aircraft or stall it with climb control. Coriolis Illusion is when the flow of endolymph fluid in the semicircular canals of the pilot's inner ear stops after 20 seconds during prolonged turns made at a constant angle and flight speed, and the pilot loses orientation when the endolymph flow becomes chaotic when the head is suddenly turned in one direction, and the pilot experiences a false dive, climb, tumble perception, especially in cloud or night flight where there is no visual reference. If there is a visual reference, it can be overcome slightly, but it is difficult at night and in clouds. The pilot should rely on flight instruments, not perceptions.

DIFFERENT CAUSES OF SD

As mentioned in the introduction above, the concept of SD includes not only sensory illusions originating from the vestibular system (inner ear), but also some sensory illusions originating from the visual system, such as the confusion of earth-sky lights. Relative motion is the illusion that the movement of another vehicle passing by a stationary vehicle A creates the illusion that vehicle A is also travelling backwards. In situations such as heavy rain or snowfall hitting the windscreen of the aircraft, the pilot may be mistaken in the perception of movement and speed.  In some pilots, the large glass canopy covering above the waist, such as the F-16 aircraft, creates a feeling as if they are flying on a flying carpet (flying carpet, magic carpet illusion). Therefore, the concept of SD is a broader and more inclusive concept than the concept of vertigo and includes many other illusions in addition to the illusions that create the sensation of vertigo.

AIRLINE AIRCRAFT ACCIDENTS IN THE SCOPE OF TYPE3 SD

The Type3 SD illusion occurs not only in training and fighter jet aircraft, but also in airline aircraft that are always flown with two pilots. On 30 January 1975, a Turkish Airlines (THY) F28 Fokker-1000 twin-jet engine aircraft crashed into the sea off Ambarlı, west of Yeşilköy, while landing at Yeşilköy Airport in overcast and rainy weather at night after taking off from İzmir/Cumaovası Airport, killing 42 people, including the entire flight crew and passengers. In this incident, while the aircraft was on the final approach to the 05 direction of the runway over Marmara for landing, a complete electrical failure occurred at the airport, the runway lights went out, and the pilots passed on the final approach and headed towards the sea. Within 30 seconds, the generators were switched on and the runway lights were switched on. The pilots did not report any malfunction to the tower and the aircraft crashed into the sea off Ambarlı. 

Similar to this accident, on 23 August 2000, an Airbus A320 aircraft of Gulf Air Airlines crashed into the Persian Gulf on landing at Bahrain Airport after taking off from Cairo Airport, killing 143 people, including the flight crew and passengers. In the accident report published on 15 August 2002, it was stated that the pilots were unsuccessful in their approach to runway 12 of the airport for landing and lost control of the aircraft during the approach and crashed into the Persian Gulf. The statement that the pilots lost control of the aircraft due to "Spatial Disorientation" was included in the official accident report.

HOW DID I MEET VERTIGO?

How did I first meet vertigo in flight? In the USA, where I went with three of my classmates for pilot training, after successfully completing the instrument flight and arm flight training phases in T-33 type aircraft, navigation flights were planned with our instructors in two aircraft arms, except for boarding flights on weekends to the farthest airports where the aircraft could go with full fuel load. In these flights above 30.000 feet altitude, the instructor would fly in the front cockpit of the number 1 aircraft in the front, and the student pilot would fly in the rear cockpit under the bellows. (The term "under the bellows" refers to the arrangement where the rear cockpit upper window is covered with a white sheet so that the pilot cannot see outside and can only fly by looking at the instruments). In the front cockpit of the aircraft in the arm, the student flew and the instructor flew in the rear cockpit. Thus, while the student pilot flying in the rear cockpit of the No. 1 would be doing long-distance instrument flight training, the student pilot flying in the arm as No. 2 would be doing long-distance arm flight training. On one of these flights, we were scheduled to fly from our airfield in Greenville, Mississippi to the airfield in Pittsburgh, 680 nautical miles away from our instructor's hometown, except for the weekend (For comparison, think of the 680 nautical miles we flew that day as the distance between Istanbul Atatürk Airport and Van Airport). On the way to Pittsburgh, I flew with the instrument under the bellows in the rear pilot's cabin of the aircraft in front, and my friend Kaya Ergenç in the front cockpit of the aircraft in the arm had done arm flight training on the arm of my aircraft. After spending the weekend there, we took our seats for the return flight, Kaya Ergenç in the rear cockpit of the front aircraft under the bellows and me in the front cockpit of the arm aircraft as number two.

We had learnt from the meteorological report that the road was covered with clouds up to an altitude of 30,000 feet. The two aeroplanes started their engines at the planned time, entered the runway and took off. While I was climbing in the clouds on Kaya's arm, I said to myself: "How nice! Kaya is a great instrument flyer, and I am gaining instrument flight experience in the cloud on Kaya's arm." Probably about 10 minutes had passed since we entered the cloud in the climb when I had the feeling that the bank of the aircraft in front of me started at 30 degrees to the left and gradually increased and the bank reached over 60 degrees. While I was trying to hold on to the arm in the cloud by following the bank of the aircraft in front of me, on the other hand, I was complaining to myself: "Why does this Kaya bank over 60 degrees on a straight course? "Since, as a rule, turns are made with a 30-degree bank in instrument flights in the clouds, I could not figure out why my friend Kaya, who was a very good flyer, increased his bank to 60-70 degrees in the clouds. I could not ask Kaya on the radio why he increased his bank because I was afraid of my instructor. At that moment, it suddenly occurred to me that I might have vertigo. During our training at the flight school, I had listened attentively to the lectures given by our flight doctor on Spatial Disorientation / Vertigo in Flight, and I had read the articles published in magazines on this subject and studied this phenomenon called vertigo. Although I had a lot of difficulty holding on to Kaya's arm in the cloud, I used all my effort and was able to keep the aircraft in arm flight. When Kaya came out of the cloud above 30,000 feet during the climb, my vertigo sensation suddenly disappeared. This was my first encounter with vertigo. When we landed on the ground and came to the squadron, I told Kaya at length about how I got vertigo while flying in the cloud on his arm. (My dear classmate, Retired Brigadier General Kaya Ergenç, passed away on 30 October 2010.  I took this opportunity to commemorate Kaya Ergenç, a solid, honest person, pure heart, my dear brother. May he rest in peace!).

AN INCIDENT OF VERTIGO AT MERZIFON F-86 BASE

I would like to tell you about a vertigo incident experienced by a squadron mate of mine at Merzifon F-86 Base, where I was assigned after graduating from flight school. One day, when the weather was covered with dense clouds, the squadron had planned instrument flight missions. We took off in pairs of F-86s at 5 minute intervals.  At the end of our navigation missions, the columns took turns in a waiting pattern in the clouds. On the return of the mission, the column coming over the square five minutes ahead of me reported that it had entered a waiting pattern at 200 altitude. Approximately 15 - 20 seconds had passed when the number two of the column said in an excited voice the number of the lead aircraft: "184, you have increased the bank too much, reduce your bank". The leader said in a very calm voice: "I am not in bank, I am in level and horizon flight".  The number two shouted at the same time in a much more excited and louder voice: "184, you are increasing the bank more than 90 degrees, reduce your bank". The lead pilot again replied in a very calm voice: "There is no bank in the aircraft, we are flying straight and level". When the number two of the arm shouted "184 you are reversing, you are reversing, reduce your bank!", I could not stand it and addressed the number two of the arm by name: "Ertan, your leader says you are in level flight. You definitely have vertigo. Since you have vertigo, you think that your leader is in bank, don't leave the column!"

A beautiful F-86 aircraft in the Merzifon Base car park.

I had learnt that when giving instructions to the pilot by radio in such critical situations, addressing the pilot by name, rather than by aircraft number, creates a relaxing and reassuring feeling on the pilot. Addressing the pilot by name again on the radio: "Ertan! You are definitely in a state of vertigo, do not leave the arm." There was no conversation on the radio for about 30 seconds. In the meantime, when the pilot did not say anything on the radio, I started to worry whether he had left the column and entered an abnormal situation, when the leader reported to the tower: "Merzifon, two aircraft have left 200, started descending". So number 2 had not left the column. When we arrived at the squadron after landing, my pilot friend told me about the vertigo he experienced as follows. He said that when they pulled the Merzifon Radio Headlamp station and entered the turn for the waiting pattern, he had the feeling that the degree of bank, which was normally 30 degrees in the turn, was gradually increasing; he felt that the leader's bank exceeded 90 degrees and they were close to the opposite, and he shouted to the leader to take his bank. He said that he had experienced vertigo with low bank in his previous flights, but he had never experienced near-vertical vertigo like on that day's flight, that he had tightened his body muscles a lot in vertigo, that he had put his feet on the steering wheels, that he had contracted his body to the point of sticking his helmet to the ceiling of the canopy, and that he had tried to hold on to the arm in this way. Ertan was the biggest pilot of our fleet. During the vertigo, he put his feet on the steering wheels so hard and leaned so hard on his shoulder straps that his helmet touched the bottom of the canopy. When he landed, his knees and shoulders were still in pain. In fact, I had gone a little out of order by warning our friend Ertan, who was not in my arm, while he was in the arm of another leader. When I landed on the ground, I went to his leader and apologised to him for warning the pilot in his arm. The arm leader, who was one class senior to me, said that he welcomed my warning the pilot in his arm in that critical vertigo state and the matter was settled.

Unfortunately, four of our pilots were martyred in two separate accidents at Merzifon Base, which were considered to have been caused by vertigo during the flight of F-86s. In the accident dated 6 May 1958, during the descent of the twin F-86s in the clouds, the aircraft hit the ground beyond the descent line and two of our pilots were martyred. On 28 April 1964, in a similar accident that occurred during the descent of the F-86 column in the clouds, the aircraft hit the ground near the descent line and two of our pilot mates were martyred. 

THE VERTIGO I EXPERIENCED DURING A NIGHT FLIGHT IN A T-33 AIRCRAFT AT BALIKESİR BASE

In December 1967, the political situation in Cyprus had become very tense. Forward preparation was ordered to the bases and leave was cancelled in mid-December. Personnel were staying at the base guest house for a mission to be given at any moment. Taking into account that radio traffic could be intercepted, confidential messages were carried back and forth between Balıkesir and the Force Command Headquarters in Eskişehir by T-33. While I was flying in the F-84F aircraft of the unit, I was also flying in T-33s. One night around 22:00, I was called to the Combat Operations Centre. The Base Operations Training Chief, Kur. Colonel Sermet Yüzer (now the Operations Commander in his current job description) asked me to immediately get on a T-33 and go to Eskişehir and fulfil the instructions I would receive from the Force Command. In the meantime, orders were given to the Base Liaison Squadron and the T-33 was prepared for flight. At the time when I was given the flight mission by the Combat Operations Centre, almost all of the pilots in the guesthouse were resting in their rooms. In order not to disturb any of my friends at this late hour, I decided to go on the mission alone, without taking a pilot to the rear pilot's quarters. I went to Meydan Operations, took clearance for Balıkesir - Eskişehir IFR at an altitude of 21,000 feet and went to the aircraft. I hurriedly entered the cockpit, started the engine and took off from runway 36. Immediately after turning in the direction of Eskişehir, I entered the cloud at around 1,500 feet. The cloud I entered was a calm cloud typical of the winter months. During the climb in the cloud, a light snowfall started. When I switched to straight flight at an altitude of 210 on the route, the snowfall had intensified. I should explain how this snowfall happens to my pilot friends who fly in combat aircraft and have not encountered snowfall in clouds at night. While you are flying your instrument flight by looking at the flight instruments on the maroon panel, the snowflakes coming in the form of straight beams up to a distance of 40-50 cm from the windshield (windshield) open like an umbrella in accordance with the aerodynamic air flow of the windshield, hit the windshield rapidly and slide over the canopy. This snowfall was very different from the precipitation I had encountered in the clouds during my previous night flights. Perhaps due to the effect created by the dense snowflakes that monotonously hit the windscreen at a certain angle without interruption and scattered, after a while I got vertigo and had the feeling that I was flying with a 30 degree bank to the left. Since I knew the sensation of vertigo very well, including the anatomical details, I continued to fly on the route by maintaining a straight and horizonal flight position in the attitude gyro without any alarm. While I was continuing my flight in this way, I started to be disturbed by the light of the amber coloured radio control lamp located behind the crowbar, at the bottom left of the maroon panel, close to my foot level. Since I started my first night flight in jets at the flight school, I had made it a habit to keep the cockpit heater at the coolest level and the maroon lights at the lowest level. I thought that flying in a cool cockpit would keep me fresh throughout the flight, and flying at the lowest cockpit light level would ensure that my eyes would not be disturbed by the light and that I would have a better night landing. As I got used to flying with very low cockpit light during night flights, the light of this lamp started to disturb my eyes as if it was a yellow ship's searchlight as the minutes passed. At some point, I decided that I could no longer tolerate this amber coloured light disturbing my eyes and decided to remove the lamp from its place. Since this amber coloured lamp enabled the radios in the front and rear cockpits to be used separately, it had to be switched ON in both cockpits. When I switched the control switch to the rear cockpit and turned it OFF to extinguish the lamp, my external radio contact was lost and I could not hear the flight tower. That's when it dawned on me. When going for solo flights, shoulder straps were tied and locked in the rear cockpit and this radio control switch was switched ON. When I went to the aircraft in a hurry, I had not checked the rear cockpit and had not turned the radio control switch ON, thinking that the rear cockpit had been checked for solo flights anyway. In order to get rid of this amber-coloured light, while holding the crowbar with my right hand, I bent down to the lowest level of the left rear part of the crowbar and dismantled the lamp shaped like the thimble used by tailors for hand sewing with my left hand. When the light went out, I breathed a sigh of relief and straightened up. After I bent down to dismantle the lamp, I lifted my head sharply while straightening up and the vertigo condition increased even more and the left-sided tilting sensation increased to around 60 degrees. When the vertigo increased, I thought to myself, "Oh silly İrfan! At the end of a tiring day, at this late hour of the night, why did you go on a solo flight like a pirate and didn't take a friend in the back cockpit?"

A T-33 Aircraft in the Parking Lot of Balıkesir Base

Front Cockpit of a T-33 Aircraft

In conversations with my friends who had vertigo before, I had heard that some of them felt themselves in a 90-degree bank in case of vertigo, while others felt themselves in the opposite flight state. I was suggesting to myself that I would be able to go to Eskişehir and land comfortably with this 60-degree bank. As I approached Eskişehir, I made contact with the flight tower. After a while, I pulled the Eskişehir radio beacon at 210 altitude. After reporting to the tower that I had pulled the radio beacon, I started descending at 120 and switched to the GCA channel. When I started to descend, the vertigo feeling with a 60-degree bank was still continuing. For a moment, even if the vertigo was not up to 90 degrees and even if it gave me the feeling that I was in reverse flight, I was suggesting to myself that I would land under the clouds and complete my landing safely by fully trusting the values shown by the attitude gyro and following the instructions given by the GCA operator. While I was struggling with vertigo on the GCA approach, the GCA operator immediately warned even the smallest escapes I made on the heading and continued the approach without deviating an inch from the glide line as if he was flying in the aircraft instead of me. When I descended under the clouds around 1,500 feet from the ground, I saw the runway lights right in front of me. At that moment, the feeling of the 60-degree bank to the left of the unholy vertigo disappeared in an instant. By the way, I owe a big thank you to whoever the GCA operator was who gave me a perfect approach with his instructions in the snow that night!

I do not want to keep these vertigo incidents I experienced in flight to myself, but I would like to write and publish these memories and I would like my pilot friends who will read these memories to learn the necessary lessons from these memories. Because every pilot should know that vertigo may occur in flight when certain conditions occur. Therefore, pilots should first of all recognise this enemy called "Vertigo". If we apply to pilots the famous principle of "Know your enemy first!" of the Chinese thinker, philosopher and General Sun Tzu, who lived 500 years ago, the principle of "Know your enemy, Vertigo, first!" is a very valid principle that pilots should definitely take into consideration. A pilot who knows the scientific aspects of vertigo and visualises it in his/her mind will not be easily caught by this unholy enemy!

In our Air Force, there were also pilots from combat jet and jet training aircraft who were martyred by falling into the sea and lakes in clear weather when meteorological conditions were favourable. In those years, from the squadrons of our Air Force, one F-100C and one F-84F aircraft crashed into the Mediterranean Sea, two F-104G aircraft crashed into the Aegean Sea, one F-84G aircraft crashed into the Marmara Sea (the pilot was my beloved classmate), one F-84G aircraft crashed into Lake Beyşehir, and one RF-84F reconnaissance aircraft crashed into Lake Sapanca, I remember that an F-84G crashed into Lake Apolyont, and worst of all, 5 F-84Gs and a T-33 jet training aircraft with two pilots crashed into Lake Manyas on different dates, and unfortunately, all the pilots of these aircraft were martyred.

Prof.Dr.Muzaffer Çetingüç, an expert in flight medicine, explains the sensory errors over the lake and the sea as follows "The most important illusions in flights over lakes and seas are visual illusions, not vestibular illusions of the inner ear balance organ. Altitude perception is much better in low flights in terrestrial geographies due to the diversity of different ground structures, houses, trees. For this reason, the pilot flying at low altitudes over land can accurately estimate the distance to the ground. However, this feeling and perception decreases over water, and the pilot may be mistaken in estimating the height from the water surface in flights over lakes and seas where he thinks he can get out of the dive. Fluctuations on the water surface and boats and other vehicles on the water can be a reference for the pilot to estimate the altitude at which he flies. In night flights over water, the error increases much more. Especially if the moon and starlight reflects on still waters, distance estimation becomes much more difficult".

When I look back over the years of my flying life, I remember the pilots who entered an abnormal state due to vertigo at night or in the clouds while flying solo or in the arm, and who were martyred or parachuted because they could not get out of the abnormal state, and my fellow pilots who had vertigo in the cloud and could not get out of the abnormal state, but who survived by getting out of the abnormal state when they came out of the cloud, luckily because the cloud bottom ceiling was sufficient.  

It is a requirement of being a good pilot that pilots should visualise and recognise Spatial Disorientation, which is one of the causes of fatal accidents occurring both in military aircraft and civil airline aircraft, in their minds and brains, and if they realise that they are suffering from such a feeling misconception, they should overcome these feeling misconceptions by fully trusting the flight instruments, especially the Attitude Indicator. During my flight training, my instructor repeatedly said to me: "Sarp, in in-cloud flights, do not trust your own feelings, trust the flight instruments! Trust your attitude gyro!" I have never forgotten it!

In recent years, special SD simulator devices that make pilots experience Vertigo-Spatial Disorientation have been developed. One of these devices is used for SD training at the Air Force Aircrew Health Research and Application Centre (USAEM) in Eskişehir.  Another simulator is used in Ankara Gülhane Training and Research Hospital for SD training of civilian pilots.

Dear fellow aviators, as I come to the end of this article, I sincerely hope that my fellow pilots who will read this article, which I have prepared with a pilot / flight doctor teamwork, will benefit from the information on Type 1 SD, Type 2 SD and Type 3 SD in this article and recognise the unholy enemy called vertigo, and also learn the necessary lessons from the stories about Spatial Dysoientation / Vertigo in Flight, so that they do not get caught by this unholy enemy called vertigo in flight.  

İrfan Sarp

Contact: [email protected]