During flight training, student U.S. Naval helicopter pilots learn the use of flight instruments through a prescribed series of simulator training events. We recorded the training flights of 76 student U.S. Naval helicopter pilots undergoing the simulator phase of basic flight instrument training. From the final basic instrument simulator flight, the Vertical S-I (VS) flight maneuver, a standard flight maneuver required of the students, was selected for analysis. This maneuver was chosen because the ideal performance was well described. The training simulator is the 2B42 training device, a 6° of freedom, motion-based, high-fidelity instrument trainer. The quality of the flight performance of the cohort of student aviators executing the VS was described using objective measures of deviation from the ideal flight path. The measures included air speed, altitude, and heading average error from target values and standard deviations. The distributions of these scores for the 76 student pilots were described and used to calculate a composite score that summarized a student's overall performance of the maneuver. The worst four, the best four, and a group of four average pilots were identified from their composite scores and their relative performance was compared. A graphical summary of each pilot's flight performance was developed, and from this performance summary a pattern became evident that suggested that differences in performance levels were related to the use of flight instruments.Abstract
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Pilots may have difficulty controlling aircraft at both high and low force levels due to larger variability in force production at these force levels. The aim of this study was to measure the force variability and landing performance of pilots during an instrument landing in a flight simulator. There were 12 pilots who were tested while performing 5 instrument landings in a flight simulator, each of which required different control force inputs. Pilots can produce the least force when pushing the control column to the right, therefore the force levels for the landings were set relative to each pilot's maximum aileron-right force. The force levels for the landings were 90%, 60%, and 30% of maximal aileron-right force, normal force, and 25% of normal force. Variables recorded included electromyographic activity (EMG), aircraft control forces, aircraft attitude, perceived exertion and deviation from glide slope and heading. Multivariate analysis of variance was used to test for differences between landings. Pilots were least accurate in landing performance during the landing at 90% of maximal force (p < 0.05). There was also a trend toward decreased landing performance during the landing at 25% of normal force. Pilots were more variable in force production during the landings at 60% and 90% of maximal force (p < 0.05). Pilots are less accurate at performing instrument landings when control forces are high due to the increased variability of force production. The increase in variability at high force levels is most likely associated with motor unit recruitment, rather than rate coding. Aircraft designers need to consider the reduction in pilot performance at high force levels, as well as pilot strength limits when specifying new standards.Abstract
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Auditory speech thresholds were measured in this study. Subjects were required to discriminate a female voice recording of three-digit numbers in the presence of diotic speech babble. The voice stimulus was spatialized at 11 static azimuth positions on the horizontal plane using three different head-related transfer functions (HRTFs) measured on individuals who did not participate in this study. The diotic presentation of the voice stimulus served as the control condition. The results showed that two of the HRTFS performed similarly and had significantly lower auditory speech thresholds than the third HRTF. All three HRTFs yielded significantly lower auditory speech thresholds compared with the diotic presentation of the voice stimulus, with the largest difference at 60° azimuth. The practical implications of these results suggest that lower headphone levels of the communication system in military aircraft can be achieved without sacrificing intelligibility, thereby lessening the risk of hearing loss.Abstract
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This investigation evaluated the influence of ethnicity, Caucasian (CAU) vs. African American (AA), on thermosensitivity and metabolic heat production (HP) during cold water immersion (20°C) in 15 CAU (22.7 ± 2.7 yr) vs. 7 AA (21.7 ± 2.7 yr) males. Following a 20-min baseline period (BASE), subjects were immersed in 20°C water until esophageal temperature (Tes) reached 36.5°C or for a maximum pre-occlusion (Pre-OCC) time of 40 min. Arm and thigh cuffs were then inflated to 180 and 220 mm Hg, respectively, for 10 min (OCC). Following release of the inflated cuffs (Post-OCC), the slope of the relationship between the decrease in Tes and the increase in HP was used to define thermosensitivity (β). ANOVA revealed no significant difference in thermosensitivity between CAU and AA (CAU = 3.56 ± 1.54 vs. AA = 2.43 ± 1.58 W · kg-1 · °C-1). No significant differences (p > 0.05) were found for Tsk (CAU = 24.2 ± 1.1 vs. AA = 25.1 ± 1.1°C) or HP (p > 0.05; CAU = 2.5 ± 0.8 vs. AA = 36.5 ± 1.8 W · kg-1). However, a significant (p < 0.05) main effect for ethnicity for Tes was observed (CAU = 36.7 ± 1.8 vs. AA = 36.5 ± 1.8°C). These data suggest, despite a differential response in Tes between AA and CAU groups, the β of HP during cold water immersion is similar between CAU and AA. Therefore, these data demonstrate that when faced with a cold challenge, there is a similar response in HP between CAU and AA that is accompanied by a differential response in Tes.Abstract
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The aim of this study was to compare the effectiveness and tolerability of a chronobiotic (melatonin) with a hypnotic (zolpidem) and the combination of both substances to alleviate jet lag symptoms associated with eastward travel. This double-blind, randomized, placebo-controlled study is based on 137 volunteers flying from Switzerland to the American continent and back (6–9 time zones). The participants either received melatonin 5 mg (n = 35), zolpidem 10 mg (n = 34), a combination thereof (n = 29) or placebo (n = 39) on the eastbound flight back to Switzerland and once daily at bedtime on 4 consecutive days after the flight. The test battery included daily sleep logs, symptoms questionnaires, and the Profile of Mood States (POMS). Also, on the last treatment day, Visual Analog Scales (VAS) were completed to assess overall jet lag ratings and treatment effectiveness. Baseline data were collected on 4 consecutive days 2 wk after the flight. During post-flight treatment and baseline, motor activity was assessed in a subgroup of 49 subjects using wrist-worn ambulatory monitors. The self-rated sleep quality was significantly improved by zolpidem, especially during the night flight. Subjects taking zolpidem reported significantly less jet lag and zolpidem was rated as the most effective jet lag medication. However, zolpidem and the combination melatonin/zolpidem were less well tolerated than melatonin alone; adverse event reports included nausea, vomiting, amnesia and somnambulia to the point of incapacitation. Confusion, morning sleepiness and nausea were highest in the combination group. All active treatments led to a decrease of jet lag severity with zolpidem being the most effective treatment, particularly in facilitating sleep on night flights. Potential individual adverse reactions to this hypnotic have to be considered.Abstract
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Attitudes toward fairness and effectiveness of mandatory drug testing vary within pilot populations (4,8) as well as other populations (3). This descriptive-correlational study examined civilian student pilots' attitudes toward urinalysis (UA) drug testing over a 10-yr period and the pilots' opinions regarding effectiveness, adequacy, and fairness of the testing as a deterrent for substance abuse among pilots. A sample of three different groups of civilian aviation students (n = 314), consisted of 103 pilots studied prior to implementing a mandatory drug testing program, 113 pilots studied 1 yr after implementing a mandatory drug testing program, and 98 pilots studied 6 yr into a mandatory drug testing program. A 14-item questionnaire (α = 0.74), indicating degrees of agreement, was completed by the student pilots who were enrolled in a large civilian pilot training program. There were no significant differences among the study pilots' feelings related to anxiety of drug testing when comparing non-mandatory and mandatory groups over time. The pilots continue to believe that alcohol use by pilots within this civilian piloting training program has decreased since testing was mandated and that drug use also showed a significant decrease (p = 0.01), although not as significant (p = 0.0001) as the decrease in alcohol use. The study showed that alcohol and drug testing is more generally accepted by the pilots in the study as the decade of the 1990s came to a close.Abstract
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Over-accommodation, a tendency to focus at a distance closer than the desired distance, has been previously shown to occur when using a head-up display (HUD). A simple system was developed as a warning of an inappropriate visual accommodative response (WIVAR) during flight training. Two lines, which are seen as four low-contrast lines (physiological diplopia) if the user is focused in the distance due to the link between convergence and accommodation, are projected onto the pilot's HUD combiner. The results show that by using the WIVAR system the accommodative response can be kept more distant when viewing forward-looking infra-red imagery (by 0.12 ± 0.04 D; p < 0.05), performing a high cognitive workload task (by 0.07 ± 0.03 D; p < 0.05) and especially when viewing in a Ganzfeld (by 0.41 ± 0.12 D; p < 0.01). While collimated HUD imagery stimulates the user to a more distant focus, the use of the WIVAR lines can cause additional relaxation of accommodation.Abstract
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The U.S. Army Aeromedicat Evacuation community (MEDEVAC) possesses a long-standing tradition of excellence in the care and transportation of combat casualties. Recent developments in civilian air medical transport and quantitative review of MEDEVAC operations have identified potential areas for improvement, concentrating on enhanced flight medic standards, training, sustainment and medical oversight of the air ambulance system. These proposed changes are discussed in detail, from the perspective of current emergency medicine and aviation medicine standards of practice. If instituted, these changes would facilitate the emergence of a true air medical transport capability comparable with the civilian community standard.Abstract