A simulator is defined as a machine with a similar set of controls designed to provide a realistic imitation of the operation of a vehicle, aircraft, or other systems. These simulators provide safe and controlled environments to train the users on vehicle and device operation, to evaluate the safety of devices and controls and to conduct research on driving and driving behaviors [1]. The use of flight simulator for training aircrew (both military and commercial) has increased since World War II. Aircrew training involves use of sophisticated ground-based flight simulators [2]. In any training incident / accident, the loss of a pilot and an aircraft costs in terms of money and manpower; and in turn, decrease overall operational capability [3]. The simulators enable experience of a broad range of flight conditions and emergency procedures without jeopardizing flight safety. However, as the use of flight simulators has consistently increased over the years, a phenomenon known as simulator sickness (a subset of a larger entity of motion sickness syndrome) upon simulator exposure (SE) came into light. It is also known as visually-induced motion sickness (MS) [4]. This Simulator Sickness (SS) has been largely considered to be a persistent limiting factor in continuing flying training [5]. Simulator sickness (SS) is classically characterized by nausea, dizziness, postural instability, fatigue and general malaise [5, 6]. On cessation of SE, few symptoms may persist up to several hours; these symptoms are called after-effects. These after-effects may have adverse impact on postsimulator training activities [5].
These symptoms can be measured both subjectively (using questionnaires) and objectively (using biomedical instrumentation) for research purposes. SS appears to be most pronounced in high performance aircraft and helicopter simulators [5]. AirFox® DISO, a disorientation simulator is widely used in Indian Air Force to train aircrew of all streams (fighters, transport and helicopters) on spatial disorientation. No data is available in respect of the incidence of simulator sickness on AirFox® DISO and also on incidence of simulator sickness in Indian aircrew.
The study aimed to determine the incidence of simulator sickness in Indian aircrew after a simulator exposure using the AirFox® DISO using a Simulator Sickness Questionnaire (SSQ).
The study was carried out on the AirFox® Disorientation (DISO) installed in the Department of Acceleration Physiology & Spatial Orientation at Institute of Aerospace Medicine (IAM), Indian Air Force (IAF), Bangalore.
It is an advanced spatial disorientation training simulator with six degrees of freedom motion system (Roll, Pitch, Yaw, Heave, Surge, Sway) along with continuously rotating yaw system.
60 healthy Indian aircrew aged between 21 to 50 years participated in the study. The protocol for the study was approved from the Institute Ethics Committee. A written consent was taken from the subjects after they were fully briefed regarding the protocol and the risks involved. A thorough history was taken to exclude any unsuitability for the study. All the subjects were examined clinically before the experiment.
The subjects had the option of withdrawing from the study at any point of time during the study.
The inclusion criteria was healthy male aircrew of all the streams (viz. fighter, transport and helicopter) between age bracket of 21 years to 50 years,
The exclusion criteria included female subjects, non-pilots, civil pilots or aircrew with any illness or on any medication.
The subjects were briefed about the protocol of simulator profile and instructed to fly the same Free Flight profile for a period of 45 minutes. The profile comprised of general handling turns and maneuvers like loops and rolls. The free flight profile of 45 minutes was developed with the help of a Qualified Flight Instructor. After proper briefing, the participant was strapped to the seat (inside the cockpit). The radio-communication was checked. After starting the AirFox® DISO, the Free Flight profile was selected for simulation.
Simulator Sickness Questionnaire (SSQ) is the gold standard for measuring SS [2, 6, 7, 8, 9, 11]. This questionnaire consists of 16 symptoms associated with SS. It was administered as soon as subject came out of the generic cockpit. The subjects were instructed to “Please indicate the severity of symptoms that apply to them “right now” by circling the appropriate word”. SSQ provides four subscales viz. Nausea (N), Oculomotor (O) & Disorientation (D) and Total Severity (TS) scores. Total Severity is a convenient summary of impact of simulator exposure on different target systems within humans. Only SSQ-TS was used for statistical analysis because it is computed by adding the sums of symptomrating for nausea, oculomotor and disorientation subscales and thus is the single best index of overall severity [11].
A total of 60 subjects were studied for the after-effects of SE in terms of simulator sickness. It was measured and scored to calculate the incidence of SS as per laid down methodology. The incidence of SS was calculated by listing the percentage of participants who reported at least one symptom following simulator exposure. Incidence of SS in present study was 70%. 42 out of 60 subjects reported at least one symptom.
Symptom Reported | % Reported |
---|---|
Fullness of head | 60% |
Dizziness while eyes were closed | 50% |
Eye strain | 45% |
General discomfort | 25% |
Symptomatic subjects (n=42) were distributed in two groups viz. group A and B on the basis of age. 34 out of 48 subjects from group A had SS. The mean age of subjects in group A and B was 25.75±7.42 years and 32.17±4.62 years respectively. There was significant difference in age between group A and B.
The present study was undertaken with the aim to study the incidence of simulator sickness in Indian aircrew using AirFox® Disorientation Simulator. Additionally, it studied the role of age, flying experience and history of motion sickness or simulator sickness in causation of SS.
The data on incidence and susceptibility of IAF aircrew to simulator sickness is limited. Thus, the aims and objectives were decided with a view to study various factors pertaining to causation of SS in Indian aircrew so that the outcome of simulator training can be improved.
In the present study, the incidence of SS (using SSQ) was found to be 70%. The older experienced subjects were found to have more SS than the younger subjects. None of the subjects reported any history of MS / SS. The result of the present study is similar to studies done by Braithwaite el al (1990) Kolasinski (1995), Kennedy & Fowlkes (1992) and Johnson (2007) [2, 13, 14, 15].
As per the Simulator Sickness Questionnaire (SSQ), in the present study, the commonly reported symptoms were fullness of head (60%), dizziness with eyes closed (50%), eye strain (45%) and general discomfort (25%). Johnson (2005) reported that eyestrain (37%) and fatigue (27%) were the common symptoms whereas Braithwaite and Braithwaite reported that commonly reported symptoms were disorientation (24%) and difficult focusing (24%) [7, 15]. Kennedy et al found that fatigue (43%), sweating (30%) and eyestrain were the common symptoms reported by subjects [13]. The responses given by subjects [13]. The responses given by subjects in the present study are similar to those in the earlier studies mentioned above.
Immediately post-simulator exposure, the mean SSQ-TS scores in present study was reported as 16.08. This indicates a concern for post-simulation activities taken soon after exiting simulator, as reported by Kennedy et al [14]. It implies that the AirFox® Disorientation simulator produced symptoms of SS which raise concern for post-simulator exposure activities.
Using SSQ-TS scores, the incidence of SS in the present study was found to be 70%. In the review by McCauley (1984), incidence was reported to range from 10-80% [10]. Braithwaite and Braithwaite reported an incidence of 60% during simulation in Lynx helicopter simulator [15]. Kennedy & Fowlkes found that incidence ranged from 12-60% [13]. Pausch et el (1992), in their review, reported that it could range from 0-90% [4]. The result of the present study is similar to the findings by Pausch et al and Kennedy & Fowlkes.
In the present study, the following factors were found to increase the risk of SS.
In addition, there are some other factors which might have reduced the risk of Simulator sickness. These factors include the following:-
With a view to study the incidence of simulator sickness in Indian aircrew using AirFox® 60 healthy male volunteers were given a single simulator exposure in the form of a Free Flight profile (for a duration of 45 min) in the AirFox® DISO simulator. The effects of simulator flying experience (given in AirFox® DISO simulator) caused Simulator Sickness and the same was assessed using SSQ, a gold standard for the same. The SSQ was administered immediately post-SE and SSQ-TS scores were compiled and scored. The incidence of SS was found to be 70%. The commonly reported symptoms were fullness of head, dizziness with eyes closed, eye strain and general discomfort. The study showed that aircrew in AirFox® Disorientation simulator did report symptoms pertaining to SS and these symptoms were scored to calculate the incidence of SS (=70%) which was found to be high. Thus, this study concludes that the simulator exposure in this simulator produce SS.