Inflight workload assessment: comparison of subjective and physiological measurements

INTRODUCTION: Assessment of pilot workload during flight is an important aviation safety consideration. The aim of this study was to assess inflight pilot workload using both physiological and multidimensional subjective-ratings measurements (heart rate and NASA Task Load Index, respectively), comparing relative sensitivity during the four phases of flight: take-off, cruise, approach, and landing. METHODS: Ten male pilots volunteered to participate in the trials, which took place in a Boeing 747-400 flight simulator. Electrocardiography was performed throughout the test using the portable Cardiovis ECG system. Mean heart rate (HR) and incremental heart rate (delta HR) were considered indices of physiological workload. RESULTS: Peak HR was observed during take-off (83.2 bpm) and landing (88.6 bpm); moreover, delta HR was also greatest (14.2 bpm and 18.8 bpm). The Task Load Index (TLX) scale revealed that mental and performance demands were essential components of workload during flight. In addition, temporal demand was an important component of workload during take-off and physical demand was significant during cruise. Analysis of correlation revealed that the delta HR is significantly related to TLX scores (r = 0.81, n = 40). CONCLUSIONS: Management of the individual sources of stress, which tend to become predominant during different flight phases, should be emphasized in periodic recurrent training. For example, a pilot must be trained to cope with the increased temporal stresses associated with take-off. In addition, the recommendations will be concerned with maintaining vigilance, task allocation between pilots, and inflight rest during long-haul cruise.     

Heart rate variability, cardiac mechanics, and subjectively evaluated stress during simulator flight

The effects of a simulator flight task on the heart rate variation (HRV) and hemodynamic variables were studied in nine pilots with instrument flight ratings. An electrocardiogram (ECG), phonocardiogram (PCG), and impedance cardiogram (ICG) were recorded continuously during three successive flights. Indices of HRV, power spectra, and autocorrelograms were computed from the R-R interval signal. Stroke volume (SV), cardiac output (CO), and systolic time intervals (STI) were determined by means of the ECG, PCG, and ICG. A scaling method for a subjective evaluation of tiredness, effort, and success during the flight was used. The repeats of the flight task decreased the heart rate (HR), CO, and cardiac index (CI). The different phases of the flight altered the HR (mean 97 min-1, S.E.M. 4 min-1), total HRV (RMSM) (mean 33 ms, S.E.M. 5 ms), and the periodic HRV. Subjectively, the pilots felt only moderate stress. The subjectively evaluated tiredness was significantly associated with the STI. Moderate informative stress in the flight simulator affected the chronotropic parameters of the heart. The inotropic state of the heart was not affected by the different phases of the flight but possibly by the diminishing sympathetic drive with accommodation during the repeats.     

EEG and ECG changes during simulator operation reflect mental workload and vigilance

BACKGROUND: Performing mission tasks in a simulator influences many neurophysiological measures. Quantitative assessments of electroencephalography (EEG) and electrocardiography (ECG) have made it possible to develop indicators of mental workload and to estimate relative physiological responses to cognitive requirements. OBJECTIVE: To evaluate the effects of mental workload without actual physical risk, we studied the cortical and cardiovascular changes that occurred during simulated flight. METHODS: There were 12 pilots (8 novices and 4 experts) who simulated a flight composed of 10 sequences that induced several different mental workload levels. EEG was recorded at 12 electrode sites during rest and flight sequences; ECG activity was also recorded. Subjective tests were used to evaluate anxiety and vigilance levels. RESULTS: Theta band activity was lower during the two simulated flight rest sequences than during visual and instrument flight sequences at central, parietal, and occipital sites (p < 0.05). On the other hand, rest sequences resulted in higher beta (at the C4 site; p < 0.05) and gamma (at the central, parietal, and occipital sites; p < 0.05) power than active segments. The mean heart rate (HR) was not significantly different during any simulated flight sequence, but HR was lower for expert subjects than for novices. The subjective tests revealed no significant anxiety and high values for vigilance levels before and during flight. CONCLUSIONS: The different flight sequences performed on the simulator resulted in electrophysiological changes that expressed variations in mental workload. These results corroborate those found during study of real flights, particularly during sequences requiring the heaviest mental workload.     

Stress and workload in pilots

Several studies have highlighted the increase in physiological activity which occurs in pilots during flight and especially during takeoffs and landings. For example, it has been clearly demonstrated that pilots' heart rates increase during the landing approach to reach a peak at or just before touchdown. These changes have been attributed to workload and to psychological or emotional stress. This paper examines a number of test pilots' heart rate responses recorded during various flight trials involving different types of aircraft. Examples include ramp takeoffs in a VTOL fighter, automatic landings in fog, supersonic flight through monsoon rain, and a sortie in which the pilot developed acute appendicitis. It is concluded that heart rate responses in experienced pilots are influenced almost entirely by workload-related factors and not by emotional stressors, such as risk and anxiety. Because of the emotional overtones of the word "stress," it is suggested that the term workload should be used when referring to the reason for increased cardiovascular activity of pilots.     

歼击机飞行员脑力负荷评价模型的研究

目的 评定飞机飞行品质,建立“歼击机飞行员脑力负荷评价模型”。方法 在歼－Ａ和歼－１两种不同飞机的地面飞行模拟器上,由飞过该两种飞机的飞行员进行测试,对评价脑力负荷的主观评价法,主任务评价法,次任务评价法,生理评价法和综合评价法共７个指标用显著性测验进行选择。结果 ５个评价指标当选,根据该５个指标的权重建立了“歼击机飞行员脑力负荷评价模型”,并在歼－Ｃ飞机地面模拟器上进行了验证。结论 结果与试飞员     

Simulator induced syndrome: evidence for long-term aftereffects

Pilots have experienced various adverse symptoms hours and even days following flight simulator training. This study surveyed pilots undergoing simulator training in an attempt to provide an initial gauge of the extent, severity, and possible risk factors of long-term (greater than 1 day) simulator aftereffects. A three-part voluntary and anonymous questionnaire was used to gather data. We studied pilots of varying experience undergoing advanced flight training which included the use of flight simulators. Some 238 pilots participated in the study, and 196 completed the follow-up survey concerning long-term effects. Nine (4.6%) pilots experienced adverse symptoms 24 h or more after completion of their last simulator training, which they attributed to their recent simulator experience. Symptoms reported included: recurrent visual flashbacks, continued balance disturbance, and hand-eye discoordination. Three pilots (1.5%) reported difficulties flying aircraft. Pilot flight experience level, total simulator time, length of simulator session, and sex were not predictive of risk. This study suggests that long-term (greater than 1 day) adverse aftereffects may occur following simulator training.     

深海实潜中下潜人员的心率变异性研究

目的研究深海实潜作业中交感-迷走神经对下潜人员心脏功能的调控作用,为评价潜航员工作负荷提供参考。方法 2名潜航员和3名技术人员(作为乘员)参加实验。每次潜航为1名潜航员操作"蛟龙号"携带1名乘员(技术支持)进行实潜作业,持续时间约11 h。记录他们在潜航前和潜航作业全程的心电图,提取R-R间期,计算心率,并对心率变异性(heart rate variability,HRV)的时域和频域指标进行计算和分析。结果下潜人员的心率都在1 h达到最大并逐渐下降,其中潜航员的心率在1 h~6 h显著高于对照水平(P0.05或P0.01),乘员的心率在1 h~4 h显著高于对照水平(P0.05或P0.01),之后均恢复到对照水平。相比于对照值,在1 h,10 h,11 h,潜航员的LF/HF升高,HF/TP降低(P0.01);乘员的SDNN在8 h、9 h和11 h显著高于对照水平(P0.01)。结论在下潜和上浮阶段,潜航员的交感神经活性升高、迷走神经活性降低,可能与这两个阶段潜航员的工作负荷较高有关。在下潜阶段下潜人员心率的显著升高提示可能存在精神紧张和应激反应。潜航过程中,潜航员的心率逐渐稳定,交感神经兴奋仍有出现,提示在评价潜航员工作负荷时,HRV可能是比心率更敏感的指标。     

Pilot cerebral oxygen status during air-to-air combat maneuvering

BACKGROUND: Successful monitoring of in-flight cerebral oxygen status (COS; cerebral hemoglobin concentration changes and oxygenation changes under dynamic flight conditions) was recently achieved using near-infrared spectroscopy (NIRS). In this study, we examined the effects of air-to-air combat maneuvering on COS. METHOD: Six F-15 fighter pilots performed 2-vs.-1 air-to-air combat one to three times in each of eight sorties. We took continuous measurements of the pilots' in-flight COS using a commercial NIRS system. We measured the direct effects of G-forces on COS as evidenced by relative concentrations of oxy- and deoxy-hemoglobin. RESULTS: With respect to the G-levels reached during air combat maneuvering (Gz range of -0.4 to + 9.5), oxyhemoglobin concentration (O2Hb) and tissue oxygenation index (TOI, the ratio of oxygenated to total tissue hemoglobin) decreased with increasing G-forces during aerial combat maneuver (ACM). Maximum changes in relative O2Hb ranged from -4.2 to -26 micromol x L(-1). Subjects' experience as measured by total fighter time was an independent determinant of the magnitude of decrease in relative oxygenation. CONCLUSIONS: 1. Pilots' COS declined with dynamic G-forces experienced under aerial combat conditions. 2. Fighter pilots with more flying hours maintained a higher cerebral oxygen level at the same level of G-forces than pilots with less flying time. 3. NIRS technology in the form of the NIRO-300G has matured for continuous monitoring of in-flight cerebral oxygen status under vigorous field conditions.     

模拟飞行条件下双重任务时飞行员心理生理参数的变化特点

测量了50名健康飞行员和13名康复疗养飞行员，在模拟飞行条件下双重任务时的心理生理反应。结果发现，模拟飞行各阶段心率变化趋势与实际飞行基本一致，但变化幅度较低。双重任务时，反映情绪性变化的心率、呼吸率及肺通气量明显增加，与思维活动有关的眨眼率增加。心理运动反应速度与飞行操纵质量相互影响，其程度有个体差异。同时在该负荷环境下，发现5例心律失常的无症状飞行员。结果提示，模拟飞行双重任务条件可以造成飞行员心理生理负荷，并可能有助于发现一些潜在性病症。     

Instrument scan strategies of F-117A pilots

BACKGROUND: Eye tracking is an accurate and objective means of measuring an instrument scan pattern. The purpose of this study was to determine if prior aircraft experience, phase of flight, and autopilot mode modified the instrument scan pattern of F-117A pilots. METHODS: There were 23 F-117A pilots, grouped by prior aircraft experience, who flew an instrument approach manually and with autopilot while wearing an El Mar eye tracker in the F-117A simulator at Holloman AFB, NM. Number of fixations, dwell time, and percent total dwell time spent on nine individual instruments were collected and analyzed. RESULTS: The primary flight instrument was determined on the basis of pilot experience, and usage of the primary flight instrument varied significantly with phase of flight and manual vs. autopilot when ANOVA analysis was performed. CONCLUSIONS: Prior aircraft experience affects development of an instrument scan in a new aircraft. Prolonged dwell times on the primary flight instrument and changes in fixations/dwell time during autopilot mode have implications for instrument and cockpit design as well as cognitive load during novel situations. Further studies should be pursued.     

Simulator induced syndrome in Coast Guard aviators

The incidence of adverse symptoms in Coast Guard aviators undergoing flight simulator training was determined. A voluntary, multi-part questionnaire was completed by 238 pilots. During the first simulator flight 64.3% of pilots reported at least one adverse symptom, 39.4% during the last flight. Simulator induced syndrome (SIS) was present in 47.1% of subjects during the first simulator flight, 23.5% during their last flight. Most subjects reported their symptoms as mild, with some symptoms rated as moderate or severe in nature. There was no statistically significant association (p greater than 0.05) between the development of SIS and flight experience, simulator experience, length of simulator session, or self-determined motion sickness susceptibility. There was a significant association (p less than 0.05) between SIS development and the use of simulators with computer-generated imagery (CGI). Nine pilots experienced adverse symptoms at least 2 d after their last simulator flight. In conclusion, this study revealed that SIS occurs frequently, is more common when CGI is present, may recur, suggests an adaptative process, and may not be associated with some factors previously claimed.     

Inflight application of three pilot workload measurement techniques

Three measures of workload were tested during 11 routine missions conducted by the NASA Kuiper Airborne Observatory: communications performance, subjective ratings, and heart rate. The activities that contributed to crewmember workload varied; the commander was responsible for aircraft control and navigation whereas the copilot handled communications with ATC and the astronomers. Ratings of workload, stress, and effort given by the two crewmembers were highly correlated and varied across flight segments, peaking during takeoff and landing. Since the pilots performed different tasks during each segment, their ratings appeared to reflect overall crew workload, rather than experiences specific to each pilot. Subjective fatigue increased significantly from takeoff to landing for all flights, although the increase was significantly greater as landing times shifted from 10:00 p.m. to 9:00 a.m. The type, source, number, and frequency of communications varied significantly across flight segments, providing an objective indicator of pilot workload. Heart rate was significantly higher for the aircraft commander than for the copilot. Although heart rate peaked for both positions during takeoff and landing, the amount of change was significantly greater for the aircraft commander. Subjective ratings of stress, workload, and mental effort were significantly correlated with heart rate and communications frequency but were unrelated to mission duration, rated fatigue, or pilot evaluation of performance.     

Visual symptoms and G-LOC in the operational environment and during centrifuge training of Turkish jet pilots.

BACKGROUND: High-performance fighter aircraft produce high-sustained +Gz forces with rapid onset rates. Because of this G-producing capability, military jet pilots are subjected to physiological stress, which may lead to visual disturbances and G-induced loss of consciousness (G-LOC). Although visual disturbances are very common in jet flights, G-LOC is relatively rare but more dangerous. The frequency and causes of G-LOC need to be determined in the interest of flight safety. METHODS: Part I. A survey was conducted on Turkish jet pilots to reveal the incidence of symptoms due to +Gz acceleration. Anonymous questionnaires were given to F-16, F-4, and F-5 pilots. They consisted of inquiries about the occurrence of visual symptoms and/or G-LOC during +Gz acceleration in the operational environment. Part II. During the years 1992-1996, 486 F-16, 801 F-4, and 256 F-5 fighter pilots underwent high "G" training at Turkish Aerospace Medical Center and they were assessed in terms of G-LOC rates. RESULTS: Part I. A total of 325 pilots who flew T-37 in undergraduate pilot training (UPT) answered the questionnaire. The pilots were divided into 3 groups according to the types of aircraft, which they fly now: 116 F-16, 182 F-4, and 27 F-5 pilots. A total of 311 pilots (95.7%) reported having experienced greyouts and/or blackouts. With 25 pilots (7.7%) experiencing G-LOC, the G-LOC frequency according to the type of aircraft was: 5.2% (T-37) [in UPT]; 4.3% (F-16), 1.6% (F-4), and 0% (F-5). Part II. In centrifuge training, the incidence of G-LOC in pilots of the various types of aircraft were: 12% (F-16), 6.4% (F-4), and 8.6% (F-5). CONCLUSIONS: Centrifuge training reduces G-LOC rates of subsequent centrifuge training; and it is hoped might reduce the G-LOC rate in the operational environment. Almost all jet pilots reported having experienced +Gz related visual symptoms, but G-LOC seems to be a more common problem for pilots who fly rapid onset rate aircraft than pilots who fly high "G" capable but lower G onset rate aircraft.     

The performance of the standard rate turn (SRT) by student naval helicopter pilots

BACKGROUND: During flight training, student naval helicopter pilots learn the use of flight instruments through a prescribed series of simulator training events. The training simulator is a 6-degrees-of-freedom, motion-based, high-fidelity instrument trainer. From the final basic instrument simulator flights of student pilots, we selected for evaluation and analysis their performance of the Standard Rate Turn (SRT), a routine flight maneuver. METHODS: The performance of the SRT was scored with air speed, altitude and heading average error from target values and standard deviations. These average errors and standard deviations were used in a Multiple Analysis of Variance (MANOVA) to evaluate the effects of three independent variables: 1) direction of turn (left vs. right), 2) degree of turn (180 vs. 360 degrees); and 3) segment of turn (roll-in, first 30 s, last 30 s, and roll-out of turn). RESULTS: Only the main effects of the three independent variables were significant; there were no significant interactions. This result greatly reduces the number of different conditions that should be scored separately for the evaluation of SRT performance. The results also showed that the magnitude of the heading and altitude errors at the beginning of the SRT correlated with the magnitude of the heading and altitude errors throughout the turn. This result suggests that for the turn to be well executed, it is important for it to begin with little error in these two response parameters. CONCLUSIONS: The observations reported here should be considered when establishing SRT performance norms and comparing student scores. Furthermore, it seems easier for pilots to maintain good performance than to correct poor performance.     

事故后飞行人员专项心理评估技术的研究

目的通过对事故后飞行人员心理状况进行实证量化研究,形成一套迅速、有效地针对事故后飞行人员的心理评估的专项技术。方法对580名飞行员实施流行病学调查、创伤后应激反应症状自评以及心理健康评估。结果通过流行病学调查筛查出事故亲身经历以及自评影响251例;根据心理特质将飞行人员聚为三类;PTSD-SS阳性51例,经过临床医师确诊34例,其中有28例属于反应过激型的飞行人员,符合率为82.4%。结论心理测验评估结果与临床诊断具有较好的一致性,通过三个层次的筛查与验证性研究,形成对事故后飞行人员心理状况的评估的专项技术,对飞行作战训练有着重要的临床意义。     

Urinary catecholamine responses in F-15 pilots: evaluation of the stress induced by long-distance flights

Included in the Cooperative Cope Thunder exercises from Japan to Alaska is one of the longest distance flight missions carried out by Japan Air-Self Defense Force F-15 pilots. The magnitude of the flight stress of these pilots is considered to be quite high. The purpose of this study was to evaluate the flight stress induced by the long-distance flights. The subjects were eight pilots who participated on a volunteer basis. Samples of urine were collected approximately 30 minutes before (preflight) and 20 minutes after (postflight) the flights. The ratios (post-:preflight) of noradrenaline levels were 1.20 +/- 0.09 (Japan-Alaska) and 1.32 +/- 0.12 (Alaska-Japan), and those of adrenaline were 4.03 +/- 1.06 and 3.68 +/- 0.98. These results strongly suggest that psychological stress during the long-distance flights is increased in the fighter pilots.     

Heart rate monitoring of pilots during steep-gradient approaches.

As part of a large scale investigation into noise abatement landing approaches, one trial involved the flight evaluation of steep-gradient and two-segment approaches; these were 3 degress, 6 degrees, 7.5 degrees, and 9 degrees single-segment, and 7.5 degrees/3 degrees two-segment approaches. To augment the subjective opinions of the test pilots, their heart rates were monitored during all the experimental runs. The resulting heart rate values for the different approaches correlated reasonably well with the subjective ratings of the relative workload levels. There is some evidence that the pilot workload level for the 7.5 degrees/3 degrees approaches is of the same order as the level for the conventional 3 degrees gradient.     

The performance of standard vertical S-1 flight maneuvers by student U.S. Naval helicopter pilots

BACKGROUND: During flight training, student U.S. Naval helicopter pilots learn the use of flight instruments through a prescribed series of simulator training events. We recorded the training flights of 76 student U.S. Naval helicopter pilots undergoing the simulator phase of basic flight instrument training. From the final basic instrument simulator flight, the Vertical S-I (VS) flight maneuver, a standard flight maneuver required of the students, was selected for analysis. This maneuver was chosen because the ideal performance was well described. METHODS: The training simulator is the 2B42 training device, a 6 degrees of freedom, motion-based, high-fidelity instrument trainer. The quality of the flight performance of the cohort of student aviators executing the VS was described using objective measures of deviation from the ideal flight path. The measures included air speed, altitude, and heading average error from target values and standard deviations. RESULTS: The distributions of these scores for the 76 student pilots were described and used to calculate a composite score that summarized a student's overall performance of the maneuver. The worst four, the best four, and a group of four average pilots were identified from their composite scores and their relative performance was compared. CONCLUSIONS: A graphical summary of each pilot's flight performance was developed, and from this performance summary a pattern became evident that suggested that differences in performance levels were related to the use of flight instruments.     

Neuroendocrine responses to psychological workload of instrument flying in student pilots.

BACKGROUND: Information processing and stress tolerance are necessary features for instrument flying (IFR), especially among student pilots. Psychological workload of IFR flight may lead to stress reactions such as neuroendocrine activity. METHODS: Neuroendocrine responses to an IFR flight with Vinka piston-engined primary trainer were studied in 35 male volunteers who participated in the basic military flying course of the Finnish Air Force (FAF). The student pilots performed a 40-min IFR flight mission and a control session on land in randomized order between 11.00 h and 15.00 h. The IFR flight included 3 NDB approaches and was evaluated by flight instructors. Blood samples were collected 15 min before, 5 min and 60 min after the flight as well as control session, and. Plasma ACTH, beta3-endorphin (BE), cortisol, prolactin, adrenaline (A) and noradrenaline (NA) were measured. Psychological evaluations included psychomotor test (Wiener), Multi Coordination and Attention Test, ability tests and personality tests (CMPS and 16 PF). The overall psychological evaluation was made by an aviation psychologist. RESULTS: Plasma ACTH was significantly higher before and 5 min after the flight compared with control levels, but plasma BE increased significantly only before the flight. Plasma cortisol was significantly elevated before and 5 min after the flight. Plasma prolactin, NA and A increases were significant 5 min after the flight. High A levels after the flight correlated significantly with poor IFR flight performance as well as with poor psychomotor test results. CONCLUSIONS: The plasma prolactin and NA increases after the flight represented a direct type of stress reaction to the flight situation. The plasma BE response to IFR flight was an anticipatory stress reaction, but plasma ACTH, cortisol and A responses included both anticipatory and direct types of stress reactions. Psychological factors, flight performance and neuroendocrine responses to IFR flight appear to be associated with each other. Therefore, neuroendocrine reactions as a response to the psychological workload of military flying could be used for identifying stress tolerance in military pilots.     

高性能战斗机大强度飞行对飞行员生理指标及飞行劳动负荷主观评价的影响

目的观察高性能战斗机大强度飞行对飞行员的生理指标及飞行劳动负荷主观评价的影响。方法5名健康男性高性能战斗机飞行员在1个飞行日内共进行22架次的大强度飞行。记录飞行过程中的心电信号,分析心率及心率变异性（heart rate variability,HRV）;飞行后进行飞行劳动负荷和疲劳程度主观评价。结果飞行员大强度飞行时,随着飞行负荷的降低,心率和HRV频域及时域指标呈现一定的规律性变化。心率在夜问较日问低;夜间校正高频功率（high frequency normalized unit,HFnu）高于日间,校正低频功率（low frequency normalized unit,LFnu）及低频高频比值（LF／HF）则低于日问。飞行员飞行劳动负荷及疲劳程度主观评价分值均较低,没有明显的主观疲劳感。结论高性能战斗机大强度飞行对飞行员生理指标有一定影响,但尚未引起飞行疲劳。合理的飞行安排及有力的航卫保障有利于飞行员身体机能的恢复,预防飞行疲劳,保障飞行安全。