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Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20
Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft a
a
a
a
SARAH A. NUNNELEY , PATRICK J. DOWD , LOREN G. MYHRE , RICHARD F. STRIBLEY & RICHARD C. MCNEE
a
a
U.S.A.F. School of Aerospace Medicine , Brooks A.F.B, Texas, 78235, U.S.A. Published online: 27 Mar 2007.
To cite this article: SARAH A. NUNNELEY , PATRICK J. DOWD , LOREN G. MYHRE , RICHARD F. STRIBLEY & RICHARD C. MCNEE (1979) Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft, Ergonomics, 22:5, 549-555, DOI: 10.1080/00140137908924639 To link to this article: http://dx.doi.org/10.1080/00140137908924639
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
ERGONOMICS, 1979, VOL. 22, No.5, 549-555
Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft
Downloaded by [University of Toronto Libraries] at 09:08 19 November 2014
By SARAH A. NUNNELEY, PATRICK J. DoWD, LOREN G. MYHRE, RICHARD F. STRIBLEY AND RICHARD C. McNEE U.S.A.F. School of Aerospace Medicine. Brooks A.F.R .. Texas 78235. U.S.A. Heat stress can be a significant problem in high-performance aircraft, where it has a measurable ohvsiolouicul impact on aircrcw and may alter the learning curve for novel tasks. In these experiments nine 1111:11 wen: uamed 1O plateau performance on a compensatory tracking task. They were then tested at the end of 2 h exposures to the following conditions (Tdbl Tw b ,
"C): Control (C) 25/ambienl. Warm (W) 35/26 and HOI (H) 40/30. For Wand H, globe
temperature was raised to 12°C above Tdb by infrared lamps. While W was physiologically compensable. H was near the upper limit of tolerance. as shown by steadily rising heart rate. elevated rectal temperature and I A kg mean weight loss. The simplest tracking task showed a small but statistically significant improvement in time on target with heat, while two more difficult tasks showed no change. Human operator modelling supported these findings. Discussion relates these results to actual cockpit conditions and the literature of performance in heal.
1. Introduction Heat stress is a common problem in high-performance aircraft because weight and power considerations limit the amount of cooling available. Particularly troublesome are ground operations and low-level, high-speed flight in warm climates. Heal sources for the cockpit include high ambient temperature, sunlight, aerodynamic heating and heat generated by avionics. Miniaturized instrumentation now allows the recording of cockpit conditions in flight (Allan et al. 1976, Nunneley and James 1977). Relevant variables include air temperature, humidity, radiant heat load and air velocity, as well as physiological status. These measurements confirm the existence of significant heat stress in flight: in summer, fighter cockpits commonly exceed 50°C Td b during ground standby and remain above 30°C during low-level flight (Allan et al. 1976, Stribley et al. 1977, unpublished data from this laboratory). The resulting physiological strain is intensified by the requirement that aircrew wear multiple layers of protective clothing and equipment. Losses of 1-2 % body weight are seen during typical sorties of 1-2 h duration (Allan et al. 1976, Bollinger and Carwell 1975). This raises the question of possible heat-related changes in aircrew performance. The relevant literature is large, complex, and often contradictory. Several comprehensive reviews exist( Grether 1973, Jones 1969, Poulton 1976, Wing 1965). Nevertheless, it is still impossible to predict the effect of a specific environment on mental function. We have therefore conducted a series of performance tests in a chamber using thermal conditions which resemble those recorded in flight. The first set of experiments involved assessment of fatigue and cognitive function during pairs of . sorties' (Nunneley et al. 1978). The major finding was that heat not only induced fatigue but interfered with the normal learning curve. Nine of the same subjects were trained on a tracking task for this second set of experiments. 2. Methods 2.1. Experimental Task and Conditions The compensatory tracking task consisted of a computer-driven display as
550
Sarah A. N tl/lIleley et al.
illustrated in figure I. The subject attempted to keep a moving dot centred within a fixed circle (6 mm diameter), using a force control stick; error appeared as a vertical displacement of the dot from centre (Threatt 1976). Each run consisted of three 5 min RANDOM ... NOISE -
Figure I.
Schematic diagram of compensatory tracking task. Error display consists of vertical displace-
Downloaded by [University of Toronto Libraries] at 09:08 19 November 2014
ment on cathode ray tube.
trials separated by a 3 min rest interval, with different plants and input noise bandwidths as follows: Trial I
Plant
2
K/s K/s
3
Kls (s
+
a)
Bandwidth (Hz) 0·5 1·5 0·5
The K{s plant responded to control inputs at a velocity which was proportional to stick output; increasing the input noise bandwidth made the task more difficult since the higher frequencies imposed faster rates of random target motion. The Kls (s + a) plant incorporated a lag between control input and target response. All subjects were trained until their learning essentially plateaued. They were then tested in groups of three, each group completing" its experiments in 21 days or less. TQ further control learning effects, the sequence of temperature exposure was based on a latin square design using three squares, one for each group of subjects tested. The three thermal environments used were designated e (control), W (warm) and H (hot) as shown in table I. At the subject's location air movement was just perceptible, averaging 1-2 Table I.
Chamber conditions
r: (0C)
C 25
W 35
T.'
Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20
Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft a
a
a
a
SARAH A. NUNNELEY , PATRICK J. DOWD , LOREN G. MYHRE , RICHARD F. STRIBLEY & RICHARD C. MCNEE
a
a
U.S.A.F. School of Aerospace Medicine , Brooks A.F.B, Texas, 78235, U.S.A. Published online: 27 Mar 2007.
To cite this article: SARAH A. NUNNELEY , PATRICK J. DOWD , LOREN G. MYHRE , RICHARD F. STRIBLEY & RICHARD C. MCNEE (1979) Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft, Ergonomics, 22:5, 549-555, DOI: 10.1080/00140137908924639 To link to this article: http://dx.doi.org/10.1080/00140137908924639
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
ERGONOMICS, 1979, VOL. 22, No.5, 549-555
Tracking-Task Performance during Heat Stress Simulating Cockpit Conditions in High-Performance Aircraft
Downloaded by [University of Toronto Libraries] at 09:08 19 November 2014
By SARAH A. NUNNELEY, PATRICK J. DoWD, LOREN G. MYHRE, RICHARD F. STRIBLEY AND RICHARD C. McNEE U.S.A.F. School of Aerospace Medicine. Brooks A.F.R .. Texas 78235. U.S.A. Heat stress can be a significant problem in high-performance aircraft, where it has a measurable ohvsiolouicul impact on aircrcw and may alter the learning curve for novel tasks. In these experiments nine 1111:11 wen: uamed 1O plateau performance on a compensatory tracking task. They were then tested at the end of 2 h exposures to the following conditions (Tdbl Tw b ,
"C): Control (C) 25/ambienl. Warm (W) 35/26 and HOI (H) 40/30. For Wand H, globe
temperature was raised to 12°C above Tdb by infrared lamps. While W was physiologically compensable. H was near the upper limit of tolerance. as shown by steadily rising heart rate. elevated rectal temperature and I A kg mean weight loss. The simplest tracking task showed a small but statistically significant improvement in time on target with heat, while two more difficult tasks showed no change. Human operator modelling supported these findings. Discussion relates these results to actual cockpit conditions and the literature of performance in heal.
1. Introduction Heat stress is a common problem in high-performance aircraft because weight and power considerations limit the amount of cooling available. Particularly troublesome are ground operations and low-level, high-speed flight in warm climates. Heal sources for the cockpit include high ambient temperature, sunlight, aerodynamic heating and heat generated by avionics. Miniaturized instrumentation now allows the recording of cockpit conditions in flight (Allan et al. 1976, Nunneley and James 1977). Relevant variables include air temperature, humidity, radiant heat load and air velocity, as well as physiological status. These measurements confirm the existence of significant heat stress in flight: in summer, fighter cockpits commonly exceed 50°C Td b during ground standby and remain above 30°C during low-level flight (Allan et al. 1976, Stribley et al. 1977, unpublished data from this laboratory). The resulting physiological strain is intensified by the requirement that aircrew wear multiple layers of protective clothing and equipment. Losses of 1-2 % body weight are seen during typical sorties of 1-2 h duration (Allan et al. 1976, Bollinger and Carwell 1975). This raises the question of possible heat-related changes in aircrew performance. The relevant literature is large, complex, and often contradictory. Several comprehensive reviews exist( Grether 1973, Jones 1969, Poulton 1976, Wing 1965). Nevertheless, it is still impossible to predict the effect of a specific environment on mental function. We have therefore conducted a series of performance tests in a chamber using thermal conditions which resemble those recorded in flight. The first set of experiments involved assessment of fatigue and cognitive function during pairs of . sorties' (Nunneley et al. 1978). The major finding was that heat not only induced fatigue but interfered with the normal learning curve. Nine of the same subjects were trained on a tracking task for this second set of experiments. 2. Methods 2.1. Experimental Task and Conditions The compensatory tracking task consisted of a computer-driven display as
550
Sarah A. N tl/lIleley et al.
illustrated in figure I. The subject attempted to keep a moving dot centred within a fixed circle (6 mm diameter), using a force control stick; error appeared as a vertical displacement of the dot from centre (Threatt 1976). Each run consisted of three 5 min RANDOM ... NOISE -
Figure I.
Schematic diagram of compensatory tracking task. Error display consists of vertical displace-
Downloaded by [University of Toronto Libraries] at 09:08 19 November 2014
ment on cathode ray tube.
trials separated by a 3 min rest interval, with different plants and input noise bandwidths as follows: Trial I
Plant
2
K/s K/s
3
Kls (s
+
a)
Bandwidth (Hz) 0·5 1·5 0·5
The K{s plant responded to control inputs at a velocity which was proportional to stick output; increasing the input noise bandwidth made the task more difficult since the higher frequencies imposed faster rates of random target motion. The Kls (s + a) plant incorporated a lag between control input and target response. All subjects were trained until their learning essentially plateaued. They were then tested in groups of three, each group completing" its experiments in 21 days or less. TQ further control learning effects, the sequence of temperature exposure was based on a latin square design using three squares, one for each group of subjects tested. The three thermal environments used were designated e (control), W (warm) and H (hot) as shown in table I. At the subject's location air movement was just perceptible, averaging 1-2 Table I.
Chamber conditions
r: (0C)
C 25
W 35
T.'
