Illusions due to reduced visual cues at night have long been cited as contributing to the dangerous tendency of pilots to fly too low during night landing approaches. The cue of motion parallax, a difference in rate of apparent movement of objects in the visual field, is frequently suggested as contributing to visual judgments of glide path but has not been systematically studied in relation to the night approach problem. Thus, the present experiment examined the effect of varying levels of motion parallax from both radial and vertical motion on perception of the orientation of a runway relative to the ground. Under simulated nighttime conditions (only runway and approach lighting were visible), 16 nonpilots adjusted the apparent slant of a model runway to make it appear horizontal as the model moved toward them along a 3° approach path from a simulated distance of 4.33 to 1.33 nautical miles. Simulated approach speeds of 62 and 125 kn were used. The rate at which the model rotated during slant adjustments varied between 5° and 30°/min. The adjusted slant of the runway model with respect to the approach path (generated approach angle) was the dependent variable. The average generated approach angle for 256 trials was 0.5°. This consistent and large deviation from 3°, which would represent accurate perception, indicates the presence of strong illusions, is in agreement, with the documented tendency of pilots to fly low approaches at night, and is explained in terms of the equidistance tendency and/or errors in perceiving the direction of the model in the visual field. The data also suggest that motion parallax in the runway image is neither a reliable nor an effective cue for the safe judgment of glide path at distances greater than 1.33 miles.Abstract
Information concerning the renin-angiotensin-aldosterone system during physical exercise in the heat with adequate fluid and/or electrolyte supplement is lacking. The present study was intended to describe the changes in renin activity and serum aldosterone, serum sodium, and serum potassium in subjects receiving water or a potassium-rich electrolyte solution while exercising (50% VO2 max) for 120 min in a warm environment (32°C, 50% relative humidity). This study shows that, in subjects receiving the electrolyte supplement, serum potassium is elevated slightly during the exercise period whereas serum sodium is unchanged from preexercise levels without the electrolyte supplement. Plasma renin and aidosterone levels were significantly reduced in the subjects receiving the electrolyte supplement compared to subjects receiving only water. The ingestion of the electrolyte supplement replaced 42% of the sodium and 100% of the potassium lost by way of sweat and urine while exercising in the heat.Abstract
Word discrimination was measured on eight general aviation pilots listening alternately through each of three communication headsets and an aircraft loudspeaker in the presence of light aircraft noise. Each subject listened at the speech intensity designated by him as yielding optimal intelligibility. Performance varied directly with the degree of attenuation provided by the headset. Mean intelligibility scores ranged from 73% through the loudspeaker to 92% through two of the headsets, although retesting through the loudspeaker at a higher signal level improved mean scores to 85%. Articulation functions obtained on four normally hearing listeners tested under the same conditions as the pilots revealed that, for situations when little or no attenuation was available (loudspeaker and one headset), greater signal-to-noise ratios were necessary to allow discrimination equivalent to that obtained under conditions of greater noise attenuation (two headsets). Although good intelligibility could be achieved through the loudspeaker given sufficient signal intensity (>100 dB SPL) some pilots preferred lower levels even though discrimination was reduced.Abstract
Breathing 100% oxygen at ambient pressure induces disorders in glutamate, GABA, and ammonia metabolism in the brain, beginning 30 min after exposure. The steep increase in glutamine content points to an enhanced metabolism of endogenous amino acids and a breakdown of protein, although the glutamate content is scarcely influenced during the first hours of exposure. The graph of glutamine increase proceeds nearly asymptotically after 24 h, which may be related to the permeability of blood brain barrier for glutamine. The initially fast increase in the GABA level attains a half-maximum augmentation after 2-4 h of exposure and a maximum value after 50 h, but then the graph of GABA slopes steeply downwards, and approximately linearly, until 74.76 h and finally, by 103 h, more gradually approaches control values. The increase in GABA level is discussed with regard to the physiological role of GABA as a homeostatic agent that connects oxidative metabolism with neuronal function. Glutamate, the precursor of giutamine as well as GABA, is affected by oxygen breathing with a “loss” of more than 6 μmol/g wet wt. after 100 h of exposure. Functionally, this diminution may be coorelated to the increase of GABA with respect to its anti-excitatory effect and a possible postsynaptic function of giutamine synthetase.Abstract
Oxygen and carbon dioxide tension in arterial blood were studied in mice breathing 100% oxygen at ambient pressure. The lungs were simultaneously investigated in order to relate the oxygen-induced pulmonary alterations to the altered pulmonary function. The development of an impairment in pulmonary diffusing capacity is initiated after 30 h of oxygen exposure, at which time the increase in lung weight is associated with beginning lung edema and beginning accumulation of carbon dioxide in the blood. Red spots or areas on the lung surface, which merged together to large streaks or areas after 20 h of exposure, preceded the measurable diffusing impairment noted at 30 h. Light microscope preparations revealed intraalveolar hemorrhagic exudation and proliferative changes in the alveolar walls. After 50 h, the development of severe pulmonary dysfunction is mainly due to an intense parenchymal reaction in the alveolo-eapillary region with thickening in the alveolar walls, dystelectasis in the corresponding parenchyma, and further development of pulmonary edema. The resulting impairment in pulmonary diffusing capacity causes a steep decrease in oxygen tension and an accentuated increase in carbon dioxide accumulation. The present results are discussed in relation to the previous findings of oxygen-induced alterations in brain glutamate, GABA, and giutamine concentration.Abstract
Deep body and skin temperatures were measured on nine subjects during a I h immersion in water at 2.5°C whilst wearing an RAF Mark 10 immersion coverall. With no additional insulation, mean skin temperature fell 13.1°C and deep body temperature 0.74°C. When a full Acrilan pile suit was worn beneath the coverall mean skin temperature fell 8.3°C and deep body temperature 0.33°C. With insulation covering the trunk and upper limbs alone, mean skin temperature fell 9.9°C and deep body temperature 0.45°C. Conclusions are drawn concerning the effects on body cooling of changes in insulation of aircrew clothing assemblies designed to protect against immersion in cold waterAbstract
A blindfolded recumbent subject experiences a variety of postural illusions when rotated about his Z axis. Initially, during the acceleratury phase of rotation turning about his Z axis is experienced; hut, as rotary velocity increases, a spiraling of the body outward in the direction opposite to true rotation is experienced as well. Above 15-20 rpm, only orbital motion of the body is experienced, with the subject feeling that he is always facing in the same direction. One cycle of the apparent orbit is completed each time the subject actually rotates 360°. The reverse sequence of illusory motion is experienced during deceleration. The illusory motion all subjects experience during Z-axis recumbent rotation is shown to depend upon the touch- and pressure-stimulation of the body surface generated by contact forces of support.Abstract
Female chicks at 2 weeks post-hatch were maintained for 2 weeks at earth gravity or 2 G with daily injections of 0.2 or 0.4 mg estrone. Animals were sacrificed following the last injection and radii were fixed in 10% NBF, decalcified in 3% Nitric acid, doubly embedded, sectioned at 4 to 5 ÎĽm, and routinely processed for histological measurements of the midcoronal height and width of the cartilage zones of the proximal and distal epiphyses. Estrone treatment increased the growth in height and width of the cartilage layers of the proximal epiphyses and inhibited the growth in height of the distal epiphyseal cartilage of earth gravity chicks. Animal exposure to 2 G without estrone treatment resulted in increased width of the cartilage layers of the proximal epiphyses and inhibition of both height and width growth of the cartilage layers of the distal epiphyses. Growth in height, but not width, of the cartilage layers of both proximal and distal epiphyses was inhibited by combined estrone treatment and animal exposure to the 2 G environment.Abstract
The acceptable degree of hypoxia is a most important factor in the design of pressure cabins and of alrcrew oxygen breathing equipment. The studies of the effects of mild hypoxia upon human performance performed since 1960 are reviewed. It is concluded that the hypoxia induced by breathing air at altitudes up to 5000 ft is acceptable for both crew and passengers of combat and passenger aircraft. The magnitude and the effects of the hypoxia induced by rapid decompression are also considered. The results of the experimental investigations are correlated and it is deduced that the minimum acceptable alveolar oxygen tension on rapid decompression is 30 mm Hg.Abstract
Thirty-two USAF aircrewmen with mild or moderate, uncomplicated essential hypertension were treated with Aldactazide (spironolactone and hydrochlorothiazide). The study was designed to determine the efficacy and safety of this drug combination in aircrew subject to the stress of flying high-performance aircraft. All patients were investigated in detail before, and again 6 weeks after, beginning Aldactazide treatment. Adequate blood pressure control was achieved in 94% of patients; 84% were able to return to flying duties. Treatment was associated with a moderate loss of weight and plasma volume, and a slight reduction in renal function. Tolerance to multiple stress tests was unimpaired after treatment. Symptoms attributable to treatment were minimal. We conclude that in the dose used, four tablets or less daily, Aldactazide is a safe and fairly effective secondline treatment for hypertensive aircrewmen.Abstract
Ozone levels were rising during the period 1951 to 1972 and resulted in decreased levels of solar ultraviolet radiation reaching sea level. Analysis of the records of skin cancers for Bristol and Oxford in England showed that during the first decade of this period incidence and mortality for the skin carcinomas, basal cell and squamous cell, fell in line with theory; but both incidence and mortality for melanoma inexplicably rose. Figures for the second decade show that the data were dominated by trends other than those possibly attributable to ozone change.Abstract
.This paper reviews some of the problems encountered in administering satisfactory medical requirements for professional pilots. The role of these requirements in the context of flight safety is discussed. The control of risk by the imposition of strict requirements is contrasted with that achieved by training designed to contain the risk introduced by incapacitation. The fact that aviation safety is based on acceptable risk levels is pointed out and the role of physician in this regard is discussed. The need for a widely accepted minimum level of fitness required for aviation duties is brought out. Certain operational aspects are touched upon. Medical requirements based on the desire to avoid on-duty incapacitation are contrasted with those designed to ensure adequate performance. The present ICAO cardiovascular requirement is discussed with particular reference to permanent grounding following myocardial infarction. The significance of inflight crew incapacitation training is pointed out and a plea for close cooperation between Heensing authorities, airline operators, and pilots is made.Abstract
It is not the first time that Soviet satellites are orbited to carry out an international scientific programme. A new and convicing example of active international cooperation in space studies is the Cosmos-936 satellite which accommodates biological objects and scientific apparatus from the USSR, Czechoslovakia, the USA and France.Abstract