Vision Research: Flying and Space Travel; Proceedings of Spring Meeting, 1964. Edited by Milton a. Whitcomb and William Benson (1968) / Chapter Skim
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VISION PROBLEMS IN LOW-ALTITUDE, HIGH-SPEED FLIGHT
VISION PROBLEMS IN LOW-ALTITUDE, HIGH-SPEED FLIGHT
Pages 145-205
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From page 145... ...
The concept of flying at extremely low altitudes in order to penetrate enemy territory is by no means a new one. However, recent advances in radar defense systems and the accuracy of guided-missile systems have made it imperative that attacking aircraft avoid early detection, if at all possible, in order to insure survival.
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From page 146... ...
The purposes of the research were: first, to determine whether pilots under operational conditions become lost frequently enough to constitute a significant cause of mission failure; secondly, to determine the role for research and to establish the priority of research problems within this area: and, finally, to evaluate possible experimental techniques to be used in solving the research problems. The inquiry was limited during this phase to those missions in which the pilot must fly at low altitudes under visual flight rules.
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From page 147... ...
Fig. 1 shows the number of aircraft completely destroyed and the number of lives lost in major aircraft accidents attributable to geographic disorientation in military aviation during the years 1958 to 1962.
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From page 148... ...
A total of 72 Navy, Marine Corps, and Army pilots was asked to describe their most serious personal experiences with geographic disorientation. All but four pilots described at least one instance of becoming lost in flight; the majority said they had had many such experiences.
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From page 149... ...
When asked to relate his most serious personal experience of being lost, the pilot simply relates his most recent one -- usually an experience which has occurred within the past few months. Flight Assists to Lost Civilian Aviators The large number of civilian aviators who become lost is indicated by the Flight Assist Reports issued by the Federal Aviation Agency (FAA)
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From page 150... ...
It is important to point out that the "abort" and "recover" percentages are minimum figures, in that many cases of disorientation went unreported, and any case that was doubtful, or that had insufficient information, was thrown into the "O.K." category. Records of Individual Pilots To clarify the data obtained from the flight critiques, a study of individual differences in low-altitude navigational performance was made.
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From page 151... ...
5. Frequency distribution of disorientation incidents showing individual differences in geographic orientation performance.
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From page 152... ...
Conclusions The results of the initial investigation showed that aircraft accidents caused by geographic disorientation take a significant toll of aircraft and human lives. But the reports of critical incidents by military pilots and the large number of flight assists to lost civilian pilots indicate that geographic disorientation is far more prevalent than indicated by accident data.
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From page 153... ...
Disorientation incidents occurred about equally often at all distances from less than 50 miles to more than six hundred miles from the point of origin. In other words, the occurrence of geographic disorientation was not systematically related to distance flown, and it appears that geographic disorientation can overtake the pilot at almost any stage of a flight.
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From page 154... ...
Fig. 8 shows the different types of aircraft accidents that resulted from geographic disorientation in military aviation.
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From page 155... ...
The General Problem Areas These statistical analyses provided useful background information on the problem of geographic disorientation, but the identification of research problems came from an exhaustive study of all available informational sources. Some of the sources have already been described: aircraft accident reports, critical incident reports, flight assist reports, and the critiques of lowaltitude missions on the Sandblower courses.
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From page 156... ...
The hierarchy of problem areas was verified in the second study, which was based on 108 reports of critical incidents of geographic disorientation as personally experienced by military pilots of fixed-wing and rotary-wing aircraft. None of the pilots in the second study was from the group represented by the Sandblower mission critiques, making this an independent sample.
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From page 157... ...
10. Causes of 108 critical incidents of geographical disorientation in personal experiences of military pilots, classified by problem area.
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From page 158... ...
Army pilots. The Role of Visual Checkpoints in Geographic Orientation Since all three sources indicated that visual-reference problems played a key role in geographic orientation, a study designed to clarify this role was conducted.
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From page 160... ...
In evaluating various experimental techniques, it was found that there are two requirements of primary importance. One is the need for fidelity of visual cues -- that is, the method should provide visual stimuli which are comparable to the visual conditions in the real-world situation.
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From page 161... ...
It is possible to give him various control tasks to perform, but these will not influence the visual field, although it is possible to provide some visual compatibility with pitch, yaw, and speed control. However, the technique has the advantage of being relatively inexpensive, and is well adapted to the study of visual-reference problems (variables affecting the detection and identification of checkpoints.
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From page 162... ...
There presently exist various facilities that can be adapted to research on geographic orientation. One of these is located at North American Aviation's flight simulation laboratory in Columbus, Ohio.
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From page 163... ...
J Geographic orientation in aircraft pilots: a problem analysis.
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From page 164... ...
Flight operations at very low altitudes -- 200 (ft) and below -- have increased the demands on the visual system by changing what used to be a quasi-static visual problem to one with complex dynamic properties.
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From page 165... ...
The visual and dynamic properties of the real world are fully represented by definition. The introduction of experimental control into these observations, however, presents stubborn problems.
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From page 166... ...
It is anticipated that the controlled addition of visual complexity will permit separation of the effects of parameters which, in nature or terrain simulation, are usually confounded. DYNAMIC PROPERTIES OF THE LOW-ALTITUDE VISUAL FIELD Single-Point Geometry Unaccelerated flight past a point on the ground produces changes in the line-of-sight to that point, as shown in Fig.
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From page 167... ...
2. Apparent angular motion of ground objects.
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From page 168... ...
In a target complex made up of a horizontal area with projections on it, e.g., buildings on flat ground, the total apparent angular subtense of the horizontal elements will be increasing faster, 1/R3, with decreasing range than the vertical elements, 1/R2 (Fig.
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From page 169... ...
For more widely separated objects, some or all of which have significant vertical extent, observer motion at low altitude produces the effect of intermittent, partial, or total eclipsing of one object by another. Such masking effects seem certain to have an important effect on airborne recognition performance, but data and descriptive metrics are lacking.
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From page 170... ...
In the threedimensional diagram presented earlier, this study corresponds to full dynamic properties, relatively simple visual properties, and modest control of variables.
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From page 171... ...
. Flight Tests The initial flight test of low-altitude visual performance was an attempt to introduce as much experimental control as possible into a real-world study.
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From page 173... ...
Because of the high cost of flight testing, the number of observations of each target under any condition is small. However, collapsed data provide meaningful results when recognition range is plotted against altitude (Fig.
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From page 174... ...
60 70 FIG 11. Selected flight test data points compared with static prediction.
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From page 175... ...
L An experimental comparison of TV and direct vision for low altitude target recognition.
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From page 176... ...
Army Aeromedical Research Unit Fort Rucker In order to make any comments about the operational problems associated with low-altitude flight in Army aviation more meaningful it should first be explained what "nap-of-the-earth" can mean in terms of flight profile (Bell Helicopter Corp., n.
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From page 177... ...
Extrapolation of the reasonably effective visual range at this altitude was made from some data included in a Marine Corps study (Marine Corps School, 1961) which worked out to be about 0.188 nautical miles, or 1,142 ft.
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From page 178... ...
3. At very low altitudes, e.g., 30 ft, on flat terrain the visual streaming effects have been reported to produce nausea in pilots flying at 250 knots.2 The Army surveillance aircraft, OV-1, is capable of flying at this speed, and new experimental helicopters are rapidly approaching the 200-knot/hr capability.
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From page 179... ...
J A study of geographic orientation in aircraft pilots.
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From page 180... ...
This paper is based on Projects 9069Z, 5967Z2, and 0501T1 conducted at the Air Proving Ground Center, Air Force Systems Command. The results of the first of these projects were documented in PGN Document 641, "Human Factors Aspects of Low-Altitude Flight: A Sample of Fighter Pilot Attitudes and Altitude Estimates," dated February 1964, prepared by Robert L
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From page 181... ...
The Deputy for Effectiveness Test, Air Proving Ground Center (Air Force Systems Command) , in conjunction with the Tactical Air Warfare Center (Tactical Air Command)
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From page 182... ...
. For example, rocketry and strafing are severely limited from a highperformance aircraft flying at extremely low altitudes.
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From page 183... ...
Data on low-altitude flight directly pertinent to tactical operations gathered from field tests in which high-performance aircraft and qualified line fighter pilots were utilized are extremely rare. Regulations of the Federal Aviation Agency (FAA)
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From page 184... ...
12. The relationships between anxiety level and the estimates made by the pilots are extremely interesting, since subjects of high anxiety made significantly higher altitude estimates, with unfavorable conditions and longer flight durations interacting with anxiety level.
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From page 185... ...
4. Means for altitude estimates for reciprocating-engine and jet aircraft: 10-min flight duration period -- anxiety grouping.
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From page 186... ...
7. Means for altitude estimates for reciprocating-engine and jet aircraft: 10-min flight duration period -- total flying hours grouping.
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From page 187... ...
8. Means for altitude estimates for reciprocating-engine and jet aircraft: 1-hr flight duration period-total flying hours grouping.
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From page 188... ...
10. Mean for altitude estimates for jet aircraft: 10-min flight duration period -- total jet time grouping.
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From page 189... ...
12. Mean for altitude estimates for jet aircraft: 2-hr flight duration period -- total jet time grouping.
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From page 190... ...
In fact, very little data obtained from physical testing are available. In order to approach this significant gap, a test was conducted at Eglin Air Force Base to determine the effect of aircraft speed on low-altitude acquisition of ground targets (Joska, 1963)
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From page 191... ...
1000 4000 0 1000 2000 3000 4000 Acquisition OisMnce (Yards)
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From page 192... ...
Speed Versus Target Acquisition Distance.3 Test Speeds Sample No. Compared Sizes Results 1 250/350 KTAS0 7 Accept -- no difference 10 due to speed 2 350/450 KTAS 9 Reject -- a difference 7 due to speed 3 450/550 KTAS 6 Accept -- no difference 5 due to speed 4 250/450 KTAS 5 Accept -- no difference 6 due to speed 5 250/550 KTAS 7 Reject -- a difference 7 due to speed 6 350/550 KTAS 9 Reject -- a difference 6 due to speed 5% level of significance.
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From page 193... ...
Following necessary adjustments, it was determined that the only second-order interactions which were significant were the pilots with targets and pilots with trials. Finally, the analysis of variance in Table 3 shows that speed was a significant factor in target acquisition distance, and also that the number of trials by a particular pilot produced a significant difference in acquisition distances.
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From page 195... ...
In light of these factors, another test is presently being conducted at the Air Proving Ground Center to evaluate training techniques designed to improve the perceptual efficiency of pilots and thus improve their capability for target acquisition and recognition. These techniques involve use of linearly programmed photographs (ranging from low stimulus ambiguity to high stimulus ambiguity)
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From page 196... ...
Further, teaching machines are small and reliable, possessing great versatility, and film strips can be made up in a matter of days, hence, giving a reasonable reaction time for both large- and small-scale missions. SUMMATION The effort of the Deputy for Effectiveness Test in the area of low-altitude flight testing has been, to date, one of investigating various aspects of target acquisition and recognition, including evaluation of the techniques designed to improve the perceptual efficiency of pilots, and thus improve their capability for target 196
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From page 197... ...
F Human factors aspects of low-altitude flight: a sample of fighter pilot attitudes and altitude estimates.
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