The first formal investigation of the problem of location, operation and jettison of escape windows and hatches of helicopters following ditching has been conducted in a new simulator. There were 48 aircrew who attempted 298 escapes using a vao riety of 24 escape routes and 9 different types of escape hatches. Overall results, while superficially indicating that the task was easy, in fact revealed many unforeseen problems. Specifically, there was no standardization of hatches and levers, there were problems with location and operation of levers principally due to poor design, and an ergonomics study has not been conducted to investigate the problem. Underwater escape training with hatches in position must be mandatory for all who fly off–shore or over water for a living, and further research should be conducted to design a better standard hatch and Jettison system.Abstract
This study focused on the problem of describing changes in total peripheral resistance (TPR) and systemic arterial compliance (SAC) under time-varying +Gz acceleration stress. Nonsteady-state measures of peripheral resistance can only be derived when arterial compliance is taken into account. We have developed a successful analytical model to track simultaneous changes in peripheral resistance and systemic arterial compliance during non-stationary periods of increased gravitational lead on a beat-to-beat basis. Using a 2-element windkessel model, aortic flow into an input node was defined as equal to the sum of a capacitative (Cuo) and a resistive (Rarterial) flow leaving the node such that: ASEM.65.5.396_IE1.gif We made the assumption that Cao and Rarterial were constant over a cardiac cycle, anddivided the pressure and flow signals for each beat of a record into two different intervals, integrating this equation over each, giving two equations in two unknowns. Cao and narterial were thenobtained from the matrix solutions. To test the model, we used recordings from chronically instrumented baboons subjected to a 10 s rapid onset +Gz (head-tofoot) stress. Beat-to-beat calculations of peripheral resistance and systemic arterial compliance from our model were compared to values obtained from a previously reported 3-element windkessel model.Abstract
To adequately assess the viability of any particular causal theory of orthostatic intolerance, physical and physiological parameters thought to be associated with orthostasis must be evaluatedsimultaneously within the same individual. Time, cost, and complexity of instrumentation generally limit studies of orthostatic i tolerance to a single independent effect for any given sample of subjects. We, therefore, measured 6 key physical and physiological variables associated with various theories of orthostatic intolerance in 14 males to test the hypothesis that physical factors rather than physiological reflex mechanisms were dominant in contributing to orthostatic tolerance. Measurements included height, plasma volume (expressed as percent of total weight), variation inR-R interval, leg compliance, and carotid-cardiac (high pressure), and cardiepulmonary (low pressure) berereflex sensitivity. Subjects' orthostatic intolerante was quantified by time to syncope during progressive supine lower body decompression. Correlations, regression coefficients, and indices of replicability were calculated using 500 to 1000 bootstrap rasamplings of the original 14 observations. Although all six measurements correlated with time to syncope when evaluated individually, only height (negative), percent plasma volume weight (positive), and, to a lesser extent, carotid-cardiac barareflex sensitivity yielded consistent (reproducible) results when all measures were tested simultaneously. These results suggest that while orthostatic intolerance may be dependent upon a variety of physiological reflexes, physical factots such as height and plasma volume tend to dominate the prediction of time to syncope during lower body negative pressure(LBNP). Physiological reflexes, which act to maintain adequate profusion to the brain during normal terrestrial pasture in humans, may be overwhelmed by the additional orthostatic challenge imposed by progressive lower body decompression.Abstract
Lower body negative pressure (LBNP) of 100 mm Hg generates a footward force approximating one body weight for most subjects, yet LBNP may also produce syncope by pooling blood in the lower body. We hypothesized that dynamic leg exercise would improve LBNP tolerance by reducing lower body fluid accumulation. Seven healthymale subjects underwent four supine LBNP tolerance tests: 1) the control condition: conventional, resting LBNP with a saddle (SADL); 2) resting LBNP against a footplate instead of a saddle (FP); 3) cyclic, non-load-bearing ankle plantar- and dorsiflexion movements during LBNP with a saddle (SADLEX); and 4) LBNP with cyclic ankle plantar- and dorsiflexion exercise against the footplate (FPEX). Tolerance tests consisted of reducing chamber pressure in 10 mm Hg decrements every 3 rain to -100 mm Hg or presyncope. Tolerance was assossed by integrating the area under the LBNP x time step function. Exercise doubled LBNP tolerance relative to resting LBNP (SADL: 771 ± 162 mm Hg x min; FP: 819 ± 212; SADLEX: 1461 ± 175; FPEX: 1656 ± 160; p < 0.05). During FPEX, footward force oscillations averaged 215 ± 14 N (21.9 ± 1.4 kg), and mean peak force of 872 ± 26 N (88.9 ± 2.7 kg; n = 5) was produced by plantarflexing against 100 mm Hg LBNP. Calf volume increased slightly less when exercise accompanied LBNP (SADLEX and FPEX), while heart rate increased more. Therefore, exercise iraproved tolerance in part by skeletal muscle pumping of venous blood from the legs.However, because this pumping effect was relatively small, movement-induced sympathetic nervous system activation probably also improved LBNP tolerance by increasing heart rate and peripheral vasoconstriction to maintain blood pressure.Abstract
To investigate the effect of spaceflight on cell mediated immunity we tested delayed-type hypersensitivity (DTH) in S cosmonauts on three missions in the orbital space station MIR. DTH was determined by the intradermal application of seven antigens and a control using the standardized Multitest M6rieux. This multiple prick puncture test was applied prior to, during, and fallowing missions, which lasted for up to 177 d. In four of the five cosmonauts, reaction scores of DTH-rosponses below the warning level were noted during flight (two subjects) or following landing (two subjects). In-flight reductions of DTH-respanses were possibly induced by a series of stressful extravehicular activities and recovered to normal levels after landing. The resuits confirm earlier observations of a decreased lymphocyte function following spaceflights determined by means of mitogenic responsiveness of lymphocytes. Thus, the notion of a possibly impaired cell-mediated immunity under stress in association with spaceflight gains further support.Abstract
Otolaryngologic disease was the third most common medical cause of permanent grounding, accounting for 145 (12.2%) of 1,186 aircrew members permanently grounded for various medical reasons in the General Hospital of the Chinese Air Force, 1961-90. We reviewed the medical files of these 145 grounded aircrow members. Theirmean age was 31.7 years, their mean flight time before grounding was 878.3 hours, and the mean course of disease from onset to disqualification for flying was 3.9 years. Nearly half of them flew in fighter aircraft and 91 (62.8%) were pilots. The most common otolaryngologic condition responsible for permanent grounding was barotitis media, followed by hearing loss, M6ni6re's disease, motion sickness, and vertigo. The information from this report demonstrated that the grounded aircrew members were likely to be young, and that the course of disease from onset to grounding was too long.Abstract
The ”Guinea Pig Club” was formed in 1941 by a group of airmen who had sustained grievous injuries-mostly serious burns of the hands and face-and been treated by a team of plasticsurgeons led by a remarkable New Zealander, Archibald Mclndoe, atthe Queen Victoria Hospital at East Grinstead in England. The most senior ”Guinea Pig” was Tom Gleave, a fighter pilot who had been shot down during the Battle of Britain, and who carried out his duties as ”Chief Guinea Pig” until his death in June 1993. This paper describes Tom Gleave’s arrival at the Queen Victoria Hospital, and the formation and development of The Guinea Pig Club.Abstract
Crew fatigue associated with successive and unaugmented 36 h missions was evaluated in B-1B simulators. Data were obtained from 32 operationally qualified crewmembers. All crew members completed three consecutive, long duration missions, each preceded by 33 to 35h of crew rest. Oral temperature, salivary melatonin and cortisol, as well as actigraph and subjective measures, were collected during all missions. Temperature and melatonin data indicate that crews maintained their local home base circadian cycles. Elevated cortisol and subjective fatigue during the first mission indicate that it was the most difficult of the three. Furthermore, quality and duration of sleep were lowest during the first missio.These findings emphasize the need for realistic training in long duration fatigue management to improve the safety and effectiveness of the first and subsequent missions.Abstract
Several situational awareness (SA) and workload measurement techniques were investigated in simulated air-to-ground missions. These techniques included measures of effectiveness, subjective ratings, performance measures, and physiological measures. The results demonstrated strengths and weaknesses in all of these techniques. Measures of effectivenessand subjective ratings suggested that the experimental manipulations were effective in altering SA. The performance measures produced mixed results. Physiological measures detectedsome intriguing effects in the EEG. Overall, the complexity of the relationship between SAand workload encourages the use of multiple tools in any SA evaluation.Abstract
Three Situational Awareness Rating Scales (SARS) were developed to measure pilot performance in an operational fighter environment. These instruments rated situational awareness (SA) from three perspectives: supervisors, peers, and self-report.SARS data were gathered from 205 mission-ready USAF F-15C pilots from 8 operational squadrons. Reliabilities of the SARS were quite high, as measured by their internal consistency (O.9S to 0.99) and inter-rator agreement (0.88 to 0.97). Correlations between the supervisory and peer SARS were strongly positive (0.89 to 0.92), while correlations with the self-report SARS were positive, but smaller (0.45 to0.57). A composite SA score was developed from the supervisory and peer SARS using a principal components analysis. The resulting score was found to be highly related to previous flight experience and current flight qualification.A prediction equation derived from available background and experience factors accounted for 73% of its variance. Implications for use of the composite SA score as a criterion measure are discussed.Abstract
The United States Air Force has conducted an extensive research effort to determine the most effective way to present aircraft control, performance, and navigation information on the head-up display (HUD). The primary objective of the research was to develop a standard HUD symbology set to be used as a primary flight reference for fighter-type aircraft during instrument meteorological conditions. This paper summarizes the research conducted by scientists in the Visual Orientation Laboratory at the Flight Motion Effects Branch of the Human Systems Center’s Armstrong Laboratory. Five experiments that examined various control and performance symbology elements are reviewed. Suggested standardization guidelines based on experimental findings are discussed, including the following: the use of counter-painters for airspeed and altitude indicators, vertical and horizontal asymmetry for climb/dive ladder configurations, a ghost horizon, analog vertical-velocity information, energy management symbelogy, and quickening for climb/dive markers.Abstract
Virtual or 3–D audio display technology has become a reallty. This type of system has the capability of synthesizing signals presented over headphones that give the user the illusion that the sound is emanating from some external location. The development of this technology, its applications, and its performance in beth laboratory and flight test situations are presented. Potential fighter aircraft applications include threat location warning, wingman location indication, spatially separated multi–channel communications, and audio target location indications. The laboratory performance data show an average Iocalization error in azimuth of approximately 5°, a minimum audible angle of approximately 5°, and a speech intelligibility improvement of up to 28%. Flight test results demonstrated successful audio cued target acquisition, a subjective decrease in target acquisition times, a subjective improvement in speech intelligibility, a subjective increase in situational awareness, and a subjective decrease in pilot workload. A summary of beth laboratory and flight test results is presented in addition to recommendations for future research.Abstract
There were 29 (80%) subjects from a squadron of 36 F-! 6 pilots who voluntarily participated in a newly developed anonymous, self-administered, computerized testing protocol. The test bcltteryconsisted of two 2.5-h blocks that gathered demographic information and measured personality (MMPl-2), cognitive capacity (MAB), crew coordination skills (PCI), and history of psychiatric diagnoses (C-DIS). The test battery also included a peer rating survey that collected information about the squadron’s top performers and their personal qualities. Results indicated that aviatorscan agree who are top performers and what personal qualities are important in top performers. This pilot project demonstrated the success of the battery to gather aircrew information in a field location. Test data are presented.Abstract
Reviews of the research literature have generally concluded that personality factors contribute little to pilotperformance.One possible explanation for the failure to find stronger relationships may be due to the lack ofappropriate taxonomies for both personality constructs and for performance constructs. The present research was designed to examine the relationship between personality and combat performance using the “Big Five” model of personality and a multi-component model of pilot combat performance. A sample of 100 USAF pilots rated the importance of 60 traits for effective performance on performance dimensions such as flying skills and crew management. Theresults indicated that pilots from different aircraft agreed that the personality trait of ConKientiousness was themost important determinant of performance on all performance dimensions. Implications for pilotselection are discussed.Abstract
Do gender differences exist in perceptual-motor performance, and, if so, are the differences as substantial as those observed in trade/technical knowledge tests? What roles do general cognitire ability and videogame experience have in determining perceptual-motor performance? To address these questions, we administered a battery of computer-based tests requiring multilimb coordination and perceptual matching to a sample of 392 USAF enlistees (72% male). Our main findings were that general cognitive ability had the expected positive main effect on performance and gender and videogame experience had an interactive effect, such that videogame experience benefited men’s but not women's performance. The role of experience on perceptual-motor performance merits further attention, especially with regard to gender differences.Abstract
This experiment studied changes in brain activity as subjects performed a variable demand spatial rotation task. The task involved the sequential presentation of a template histogram and a spatially rotated comparison histogram. Task difficulty was manipulated by varying the number of bars and the degree of rotation. Topographical analysis of the brain event-related activity data indicated the presence of negative components that were maximal at the vertex within 80 ms and bilaterally in the temporal lobes within 140 ms of stimulus onset and that appearad to be insensitive to changes in task difficulty. Demandsensitive potentials were recorded, however. Positive components corresponding to P200 and P300 activity were recorded symmetrically around site PZ. The P200 component declined in amplitude, but showed no changes in latency as task demand increased. P300 activity declined in beth amplitude and latency as the task became more difficult. Finally, a positive component was recorded over right central cortex approximately 490 ms after stimulus onset. Thiscomponent declined in amplitude but increased in latency as task difficulty increased.Abstract
Pursuit tracking eye movements were analyzed from selected patients with neurological injuries and compared to the responses of 20 normal subjects. The patients/subjects tracked a small spot of light moving sinusoJdally in the horizontal plane at a frequency of 0.4 Hz and a peak-to-peak amplitude of 40° Eye-movement responses were separated into a smooth-pursuit component and a saccadic component. The smooth-pursuit component was analyzed by calculating the gain, phase, and asymmetry. The saccadic component was quantified by calculating the percentage of the total tracking movement contributed by the saccadic system. The patients with smooth-pursuit impairment exhibited a higher percentage of saccadic tracking and a lower smooth pursuit gain compared to the normal subjects. One patient with a unilateral lesion exhibited significant asymmetry in the smooth-pursuit component. In this case, the direction of the asymmetry indicated the side of the lesion.Abstract
This paper reports the epIdemiology of hospital-diagnosed acute viral hepatitis in U.S. Air Force personnel from 1980--89. First hospitalizations for viral hepatitis generally declined, ranging from 24.6 to 47.2 par 100,000 personnel. Hepatitis rates were higher among men, (RR = 1.3; 95% C.l., 1.1-1.5) and higher among blacks, compared to whites (RR = 1.4; 95% C.I.,1.3--1.6). Analysis of risk associated with various occupations demonstrated an increased risk of viral hepatitis for procedurally oriented medical personnel (physicians, clinical nurses, dentists) when compared to all other occupations (RR = 1.5; 95% C.I., 1.1-1.9). Pilots and navigators demonstrated a decreased risk of acute viral hepatitis. Members hospitalized for hepatitis B had a prior or concurrent diagnosis for sexually transmitted disease in 37% of cases; for drug abuse, 32% of cases. Serum samples from 332 individuals demonstrated that hepatitis A had the highest rate of agreement (84%) between serology and haspital discharge diagnosis. Only 3% of individuals with the diagnosis of NANB hepatitis were positive for hepatitis C.Abstract
Completion of cardiovaKular evaluations of 387 members marked the end of 40 years of follow-up in the West Point Study. Coronary artery disease (CAD) caused 4 cases of sudden death,14 cases of myocardial infarction (MI), 13 cases of angina, and 17 cases of silent CAD. Using risk factors (serum cholesterol, estimated HDL-cbulesterol, systolic blood pressure, and smoking status) measured before age 28, we derived a multivariate regrossion formula for predicting which members of the study, had they been pilots, would have been grounded for CAD before age 55. This derivation used data from only those subjects with CAD or with no evidence of CAD. We then used the formula to compute a risk-related score for each member of the study. In the tertile group with the highest risk-related Kores, 17% manifested CAD by age 55 and the first event occurred at age 39. In the tertile group of lowest scores, 2% experienced CAD by age SS and the first event occurred at age 51. We conclude that it is possible to select pilot candidates with the lowest risk for CAD.Abstract
Current high-performance fighter aircraft subject pilots to acceleration farces that can adversely effect performance and induce uncansciousness during flight. The main strategies to helpthe fighter pilot sustain +Gz include a pressurized anti-G garment (G-suit), the anti-G straining maneuver, and centrifugetraining to aptimize this effective, but very fatiguing, manauver. To improve anti-G support for aircraw, a positive-pressurebreathing anti-G system (PBG) has been developed in the COMBAT EDGE program. In order to determine if any acute adversehealth effects are occurring from the use of PBG, a survey of 241(F-15 and F-16) pilots (49 using PBG and 192 using standardmethods) was conducted. Questions were asked regarding acutehealth effects and the impact of PBG an missian accamplishment.With the exceptian of dry caugh, no significant increases in adverse events were found, and acceptance in the F-16 was muchgreater than in the F-15Abstract
Air combat maneuver acceleration (G) profiles with onset/offset patterns that occur faster than the response characteristics of the human cardiovascular system may lead to regulatoryinstability and, ultimately, acceleration-induced loss of consciousness (G-LOC) incidents. We have developed an acute animal model that simulates the hemodynamic situations seen under acceleration to study the effects of complex G environmentson individual roflexogenic areas. This preparation allowed us toindividually isolate the effects of high gravity on venous returnand cardiac preload, arterial baroreflexes and splanchnic capacity. This report describes the preparation and presents examplesof the types of +Gz simulations Passible and recordings of theresponses of the animals. Further, we tested the hypothesis thatthe volume of blood displaced from the cephalic regions of thecirculation and the rate of displacement into the splanchnic capacitance with G onset is affected by distending pressure at thecarotid/aortic barareceptor sites. Early results from 7 dogs showthat resistance to flow into the splanchnic beds is affected bychanges in distending pressure occurring at arterial baroroceptor sites. When pressure distending the carotid/aortic berareceptors was increased, resistance to flow into the abdominal Vascular beds was decreased. This result suggests that suddenIncreases in +Gz loads occurring during the overshoot phasefrom a previous G-peak may result in reduced tolerance.Abstract
It has been suggested there is a relationship between acceleration-induced loss of consciousness (G-LOC) and head/body position.A two-part investigation was conducted to determine whether head and body Position affects acceleration tolerance.A retrospective analysis of high-G training data (N = 1,914)compared G-LOC occurrence during straight-ahead exposure to a ”check-6” exposure[10 s at +9 Gz;6 G/s onset rate; G-suit inflated; anti-G straining maneuver (AGSM) performed].A prospoctive study (N = 12) was conducted with accelerationexposures using light loss criteria with subjects in straight-ahead, above, over-the-right shoulder, or over-the-loft shoulder Positions.Profiles consistedof 0.1 G/s onset-rate runs (no G-suit inflation; relaxed) to a maximum of +9 Gz and 0.5 G/s onset-rate runs (G-suit inflated; AGSM performed) to +9 Gz for up to 26 s.In the retrospective study, no significant difference existed between G-LOC occurrence during straight-ahead (22/1914) and check-6 (32/1914) Positions.During the prospective study with AGSM runs, there was no significant difference in the time at maximum G among any of the Positions. During the relaxed runs, several comparisons yielded significant differences in peak G attained. These results indicate there may be an underlying physiologic effect of head and body Position on acceleration tolerance; however, the AGSM and the G-suit overcame this effect.Although task saturation and distraction may compromise performance of the AGSM and subsequently predispose acceleration-rolated hazards, a proper AGSM, combined with effective protective systems, remains essential components of a protection strategy.Abstract
Fit for the modern flight helmet is not just comfort, but iocludes proper placement of added components (e.g., earcups, helmet-mounted optics, etc.), stability, and even center of gravity location. Many fielded and prototype helmets have been criticized for poor fit, not providing adequate sizes, and compromising safety. In this paper, evidence from studies using new surface digitizing techniques is presented revealing that a large part of the problem is due to thefact that the development of these helmets was based on traditional anthropemetry. These findings demonstrate the need for improved methods of specifying, designing, and evaluating helmets. Specifically, for development of equipment which must interface with the human body, there is a need for fit assessment in conjunction with surface scanning to define: 1 correct positioning of the humanwith respect to the equipment; 2 proper sizing; and 3 proper size issuing schemes.Abstract
Relatively little experimental and theoretical data exist on the retinal hazards of ultrashort laser pulses operating in the visible and near infrared spectral regions. Because of potential nonlinear effects that can occur from high-peak irradiance, ultrashorl laser pulses propagate from the cornea to the retina, we have developed four projects within our Ultrashort Pulse Effects program. First, we discuss preliminary EDSO threshold values for nanosecond (ns), picosecond (ps), and fomtosecond (fs) single pulses for in-vivo ocular exposures in Dutch Belted Rabbits using pulses in the visible spectral region. Then we examine two experiments that study nonlinear absorption using water tubes and measure the nonlinear refractive index of ocular tissue using the Z-Scan technique. Finally, we determine laser-induced breakdown thresholds in ultrahigh purity water. These studies give reasonable estimates of the damage thresholds and insight into the biophysics of how ultrashort pulses interact with ocular media.Abstract
Battlefield laser proliferation poses a mounting risk to aircrew and ground personnel. Laser eye protection (LEP) based on current mature, mass-praducibletechnologies absorbs visible light and can impact visual performance and color identification. These visual consequences account for many of the mission incompatibilities associated with LEP. Laboratory experiments and field investigations that examined the effects of LEP on visual performance and mission compatibility are reviewed.Laboratory experiments assessed the ability of subjects to correctly read and identify the color of head-down display symbology and tactical pilotage charts (TPC’s)with three prototype LEP visors. Field investigations included Weapons Systems Trainer (WST), ground, and flight tests of the LEP visors. Recommendations for modifying aviation lighting systems to improve LEP compatibility are proposed. Issues concerning flight safety when using LEP during air operations are discussed.Abstract
Ultrashort electromagnetic pulses are being increasingly produced by modern high power microwave and laser devices.These ultrashort pulses can produce electromagnetic transients in tissue that prompt safety questions concerning the possible exposure of living beings to ultrashort electromagnetic pulses.The existence of electromagnetic transients may permit meaningful advances in medical therapy and imaging. Electromagnetic transients, potentialmedical applications, and anticipated research avenues relevant to occupational health and safety issues are discussed.Abstract
The U.S. Air Force is concerned with the health and safety of personnel working with emitters of nonionizing electromagnetic radiation.Therefore, an understanding of basic mechanisms of interaction of this radiation with biosystems is essential.A nonresonance, nonclassical mechanism exists for interactions with biosystems under low energy (isothermal) field conditions.This mechanism is slow, or delayed, luminescence. Such a mechanism can form the basis for very sensitive biosensors naturally or artificially connected to metabolic and synthetic cellular processos.Abstract
The spatial variability of hydraulic conductivity is studied using grain-size data collected at a groundwater tracer test sitelocated at Columbus AFB, MS. The study involves vertical kriging and the construction of segmented trend surfaces. It is observed that there exists some simple spatial patterns of hydraulic cond ctivity. Also, a passible existence of a relationship between theresults obtained from grain-size data and the detrended flowmeterdata are shown.Abstract
Cleanup and treatment of hazardous wastes incur major operational costs for the U.S. Air Force. Bioremediation can provide a cost-effective alternative to traditional technologies for a wide range of natural organic compounds such as jet fuel. Bioventing and natural attenuation are emerging as treatments of choice in many instances. Synthetic organic chemicals are much more resistant to biodegradation. However, recent advances in biotechnology allow the development of strains able to use nitro- and chloro-substituted organic compounds as their sole source of carbon and energy. Current basic research is focused on expanding the range of synthetic chemicals amenable to biodegradation. At the same time, development of appropriate bioreactors and models for scale up are essential for practical application of the technology.Abstract