Abstract

The objective is to assess the remarkable ability of modern commercial aircraft to fly without serious mishaps or delays, to examine how this dependability as been achieved, and to anticipate some of the improvements that can be expected in the future. The unstated basic principle underlying many of the aircraft designer’s activities appears to be: Avoid trouble by making it easy for the pilot to stay away from it. Four different approaches illustrate the application of this principle: evolutionary improvement (jet engine), high dependability through redundancy (avionics), painstaking detail design and experimentation (pilot seat cushions), and increased pilot command and control over his craft (flight control systems). Further increases in airplane dependability through the application of these methods are expected.

Abstract

A 20-minute tilt table test was given to 18 young men and 18 young women. One man and one woman fainted during the test. Both groups showed similar orthostatic responses. Although the women had higher orthostatic heart rates and lower orthostatic blood pressure values than the men, this was attributed to similar sex differences found in recumbency.

Abstract

Two experienced and two inexperienced pilots flew Hiller 12-E and 12-EL helicopters through a series of standard maneuvers. Metabolic and heart rates were determined during each maneuver. Heart rates were significantly lower in the 12-EL, which has boosted controls, though metabolic rates were virtually identical in the two aircraft. There were no significant differences between the experienced and inexperienced pilots in either helicopter, even though the latter had not previously flown the 12-EL. The highest metabolic rates, during hovering maneuvers, approximated twice resting (seated) values. These metabolic levels were accompanied by heart rates in the neighborhood of 100/minute both in flight and during mild exercise on the ground.

Abstract

Pig-tail Macaques fed a diet of cereal grains consistently produced urine of a high (8.0-9.0) pH, with considerable calcium ppt. present.

When the protein and carbohydrate source was changed to casein and sucrose respectively, the urine pH dropped within 24 hours to a point well into the acid range, and insoluble precipitates vanished.

This phenomenon made possible the launch into space of a monkey of this species in NASA's Biosatellite D spacecraft, with reasonable hope of success. Early tests showed that the precipitates, which were primarily calcium phosphates and carbonates, were collecting in and plugging conduits carrying urine from the animal to a waste container.

Abstract

Although the air conduction audiogram alone does not provide sufficient information for diagnosis in hearing loss cases, it usually gives an indication as to whether the loss is conductive or sensorineural in origin. This information is essential to the proper handling of patients, particularly those who may be exposed to intense noises. A method for interpretation of audiometric contours is given, followed by a step-by-step procedure for analyzing the pure tone audiogram. In addition, recommendations are made concerning the handling of patients whose audiograms fall outside normal limits. Utilization of these procedures within a comprehensive program of hearing testing, noise control, and education has been found to constitute a successful hearing conservation program wherever personnel work in hazardous noises. The analysis technique should also be helpful in dealing with various types of hearing losses in many situations. A chart, Key to Interpretation of the Pure Tone Air Conduction Audiogram, provides a quick reference to patient disposition.

Abstract

Water cooling in space suits is a powerful means of extracting metabolic heat, so effective that a man can be overcooled even when working hard. The problem is how to control the cooling. Manual control by the subject has been used but man is a poor judge of his own thermal state and often reacts too late or too strongly. Automatic control based upon physiological changes is discussed in this paper for astronauts who might work hard during extravehicular activity while relying on water cooling to prevent heat accumulation and sweating in space suits.

Abstract

The rationale for personnel protection against accidental decompression in transport aircraft that will be operating in the 1970 decade is reviewed. Data pertinent to manned and simian tests that were conducted in conjunction with the B-70 program is presented in context with a review of the literature dealing with the effects of rapid decompression to altitudes of 45,000 feet and above. The results of these findings indicate a need for additional protection for flights in this region and questions the use of oxygen masks for contingencies above 35,000 feet. Potential alternatives which would augment aircrew protection are discussed in terms of feasibility and the physiological characteristics of the existing pilot inventory. A recommendation is made to provide flight stations with a capsule which would rapidly achieve a ground level oxygen equivalent upon decompression warning and be equipped for flydown to an altitude where demand oxygen equipment can safely be utilized.

Abstract

Intraocular presure changes and retinal observations, along with cardiovascular pressure measurements, were made during and after decompression of both conscious and anesthetized dogs from 10,000-ft altitude, while breathing either air or O₂, to pressures that might be encountered in supersonic or high performance aircraft if cabin pressure were lost. Decompressions were made within either 1 min (slow) or 1 sec (rapid), and exposures lasted 2 min.

When air had been breathed, intraocular pressure almost doubled during slow decompressions to 45,000 ft, and almost tripled in value at 80,000 ft. No increase was measured during the 45,000-ft exposure in which O₂ was breathed, but during the 80,000-ft exposure intraocular pressure doubled when O₂ had been breathed. Fast decompressions resulted in slightly higher values. Soon after recompression to ground level pressure, intraocular pressure increased to slightly higher values than those measured during the exposure.

Bubbles were never observed in the aqueous humor. Some retinal blanching occurred during exposure when intraocular pressure was elevated. A flame-type hemorrhage was seen infrequently. Although peripheral vision will likely be reduced, it is reasoned that changes observed during exposures at 45,000 ft are not generally of sufficient magnitudes to prevent the successful completion of a mission before vision is lost with unconsciousness. Exposure to 80,000 ft, however, especially with air, may cause temporary visual impairment that lasts for a few minutes after consciousness is regained. Safe recovery is contingent, however, on an immediate recompression to a safe pressure.

Abstract

The ability of trained miniature pigs to traverse a two-chambered shuttlebox was evaluated after they received midline tissue doses of pulsed, mixed gamma-neutron radiations ranging from 1000 to 14,700 rads. At 2400 rads or more, most pigs were almost immediately incapacitated with severe convulsions. At doses of 2400 and 5000 rads the animals began to recover and perform after a few minutes when the convulsions subsided. At higher doses, most animals became comatose and did not begin to recover until 15 to 50 minutes postirradiation. After recovering the pigs worked for a time at relatively normal levels. Later their performance degenerated, and the pigs became permanently incapacitated a few hours before death. At doses of 7600 rads and higher, some of the animals recovered only partially before becoming permanently incapacitated; and at 13,200 rads or more, most animals were permanently incapacitated immediately after irradiation.

Abstract

Fractures of vertebrae are still common during ejection from military aircraft. The majority of fractures occur between T8 and L1. Experiments were conducted on the vertical accelerator using seated human cadavers. Strain gages were installed on the anterior and lateral aspects of the vertebral bodies in order to assess the relative importance of bending and axial compression. The existence of significant bending stresses has been established. It is shown that these high bending stresses are caused by the forward rotation of the head and torso.

Various restraint system and seat-back configurations were investigated. The results show that bending strains can be reduced by increasing shoulder strap pre-tension and by leaning the seatback rearwards.

It is suggested that future models predicting vertebral injury of the seated human subjected to caudocephalad acceleration should take into account forward flexion of the head and torso and the effects of external restraints.

Abstract

Eye movements in both the horizontal as well as vertical plane and eye blinks were recorded in 13 skilled and 13 unskilled pilots while flying the UH-1D helicopter during a cross-country flight of approximately 50 minutes duration. Saccadic eye movements in both the horizontal and vertical plane were evaluated. The results demonstrate that skilled pilots engage in significantly more visual search activity in the horizontal plane than is true of novice pilots. Both skilled and unskilled pilots demonstrate changes in visual search activity as a function of time on task. These changes include: a decrease of searching in the horizontal plane; a decrease in searching in the vertical plane; an increase in the amount of time not engaged in search activity per unit time; and a decrease in blink rate. These results are interpreted as suggesting a decrease in visual search activity as a function of time-on-task.

Abstract

Consumption of food using conventional spoons and forks was investigated in a weightless environment aboard an NF-100F Aircraft. The foods which were tested included entrees, soups, fruits and vegetables, either fresh, precooked frozen, precooked wet packaged, rehydrated freeze-dried, reconstituted dehydrated or canned. All foods with the exception of whole peas were consumed without contaminating the atmosphere of the aircraft. Whole peas required a cream sauce for reliable manipulation with a spoon in the Zero “G” environment. It was demonstrated that the interfacial tensions between water and the food, containers, and utensils provide sufficient adhesion to retain food on the eating utensil during transfer from the food container to the subject’s mouth.

Abstract

The effects of compression and decompression on blood and urine chemistry in humans were assessed. Subjects were exposed to pressures up to 10 atmospheres absolute (ATA), breathing air or a 20/80 oxy-helium mixture for 1/2-1 hour periods, and 2 ATA of 100% oxygen for 1/2-hour. Samples of blood and urine were collected at depth and throughout the decompression period. Marked decreases in the excretion of sodium and calcium were found at depth on the air dives, these changes being completely reversible on decompression. Oxy-helium and pure oxygen did not alter the normal pattern of electrolyte excretion. A significant correlation between the degree of retention of sodium and/or calcium and the total pressure of air was found. Significant increases in serum potassium and inorganic phosphorous and decreases in albumin also occurred in humans at 200 and 300 ft. of air. The alterations in electrolyte distribution in humans breathing air at pressure resemble the changes found with various anaesthetic agents and implicate the narcotic properties of the nitrogen component of air.

Abstract

Although the USAF mid-air collision rate fell from 0.8 in 1947 to 0.16 in 1968, the consistent increase in the number of mid-air collisions per hundred thousand major accidents during this same period indicates that these remain one of the most acute problems in aviation safety. An evaluation of these accidents establishes not only their increasing relative frequency but also their lethal potential and their relation to aerospace traffic density and type of mission. The analysis of a classic example establishes man’s psychophysiological inability to avoid mid-air collisions on the basis of see and be seen. Man’s psychophysiological limitations remain constant. Future aerospace research and development must bridge this gap between technological advances and fixed human capabilities if mid-air collisions are to be prevented. A number of ways in which this may be done are suggested.

Abstract

Eight subjects were exposed to accelerative forces of 2.0 G_z in the Naval Air Development Center human centrifuge facility. Samples of hand-eye coordination were examined both during and after exposure.

While exposed to the 2.0 _z environment, subjects initially reached below, and then, above, a mirror-viewed target. When the accelerative forces were removed, transient after-effects were observed in which subjects reached still further above the target before they returned to baseline levels of accuracy. The aftereffects resulted only when the subjects had an opportunity to make reaching movements while they were exposed to the increased accelerative forces. Where present, the after-effects were observed for both arms.

The data suggest that the relationship between intended motor outputs and their proprioceptive-kinaesthetic consequences provides adequate information for rapid behavioral compensation and adaptation to altered accelerative forces. Further, vestibular and/or sensory-tonic factors are implicated in bringing about changes in the apparent elevation of targets viewed under increased accelerative forces.

Abstract

A study of the worldwide Aeromedical Evacuation System included an evaluation of the potential of the AES in the overall treatment of the seriously ill patient. The findings relevant to this portion of the study were based on ( 1 ) analysis of specific case histories of seriously ill patients involved in various treatment plans, each of which included air evacuation operations; (2) the application of techniques to grossly calculate the relative stress on the patient imposed by various treatment and evacuation alternatives and their application to determinations of optimum treatment plans where air evacuation is available; and (3) analysis of trends and the probable influence of new developments in medical treatment, medical equipments, air transport, and the military-civilian interfaces in the exploitation of air ambulances and specialty treatment centers. A brief description of the study program and some of its findings pertinent to the topic are presented. The study, conducted by a multi-disciplined team comprised of medical, operational, and engineering personnel, included first-hand observations of the AES covering in excess of 100,000 miles of evacuation routes throughout the worldwide system and interviews with over 150 authorities.

Abstract

During a routine company prescribed physical examination, a 50-year-old airline captain was found to have an abnormal resting electrocardiogram and a positive post exercise Master two-step test. Previous ECG’s taken annually over a period of 18 years were normal. Reexamination showed a reversion to normal with a normal exercise electrocardiogram. It was decided that this case was an unusual type of Wolff-Parkinson-White syndrome and was not related to coronary heart disease. From an analysis of the literature, and our experience with this case, it is likely that exercise electrocardiograms in the presence of Wolff-Parkinson-White type of accelerated conduction, have no diagnostic value because of the frequency of false positive tests.

Abstract

Mieroangiopathic hemolytic anemia was first used to describe the anemia which resulted from direct contact between erythrocytes and pathologically altered blood vessels producing red cell fragmentation. Fragmentation occurs in assoeiatiou with many disease entities and its existence has been known for many decades. Some authors felt that these forms were senescent red cells; however, more evi:lence points to a pathological origin. Forcing red cells aeross fibrin strands produces fragmentation in vitro. Thrombin, endotoxin, and certain venom coagulants when infused into rabbits produces red eell fragmentation in vivo. Altered fibrinogen catabolism and thrombocytopenia in patients with microangiopathic hemolytic anemia suggests that intravascular fibrin or platelet agglutination causes red cell fragmentation by mechanieal factors. These fragmented red eells release ADP and thromboplastin causing more intravaseular fibrin and establishing a vicious cycle. Thus, the etiology of fragmentation is both mechanical and chemical. While this mechanism is fairly well agreed upon, the initiating factor is still in question and here many factors may be implicated.

Abstract

Alterations to the near visual acuity requirements for professional pilots are recommended, and the reasons for these proposed alterations are discussed. The factors which influence the power and type of lens chosen for flight-deck use by a presbyopie pilot are presented, particular reference being made to the range of distances over which the main instrument panel should appear clear rather than the single distance usually considered. The possibilities of ophthalmic correction for the overhead panel are briefly examined and are concluded to be less satisfactory than a human factors engineering solution.

Abstract

Two cases of head injury complicated by subdural hematoma were referred to the USAF School of Aerospace Medicine seventeen months and two years post-surgery for aeromedlcal evaluation. In one, persistent focal central spikes and, in the other, a seizure after sleep deprivation precluded return to flying. These two high-xdsk factors for post-traumatic epilepsy (subdural hematoma and focal spike EEG abnormality) are reviewed.