The effects of flight continuity on workload, awareness and errors
Casner carried out a research experiment into the physical performance and mental performance of an out of loop experience created in the cockpit during the routine instrument approach and missed approach procedure in 2010.
Table 1 uses the central tendency of the mean and the standard deviation to measure the mental performance in terms of perceived pilot workload and the physical performance in terms of errors made on the instrument approach and missed approach. Table 1 showed an increase in perceived mental workload of pilots with less preparation time for the instrument procedure. This would seem logical. However the amount of errors made did not vary significantly between the continuous flying condition of 2.4 and the no preparation condition of 3.8 both rounded up to 3 and 4 errors with a standard deviation of approximately 2 errors. The amount of errors therefore varied per individual pilot.
We know that the test sample included pilots ranging form 500 to 30,000 flight hours of experience. An instrument approach is a routine procedure and highly experienced pilot process information at a higher rate leaving more brain function to sort out the instrument approach and will be more likely to make fewer errors. Perhaps a more controlled experiment would involve selecting pilots who hold a license with approximately the same flight hours and repeat the experiment for different ranges of flight hours. The results would be more consistent as we see the trends between excess brain capacity verses the workload saturation in terms of errors made.
Mental and physical performance measured by the mean and standard deviation per flight condition
|Mental Performance||Physical Performance||Physical Performance|
|Flight in/out of the loop condition||Mean workload Rating||Average number of errors||Standard Deviation of errors|
Casner used an “awareness self-assessment instrument” (Casner, 2010, p. 4) used by Vidulich and Hughes (1991). They were asked to evaluate their awareness both when taking control of the airplane at the start of the instrument procedure and their awareness on finishing the instrument procedure with a strength ranging from “absolute, very strong, strong, weak and equal” (Casner, 2010, p. 6). In table 2, I have used the standard deviation to indicate the size of the relationship between each condition. The standard deviation indicated a strong relationship between the continuous flight conditions compared to the no preparation condition, which again would seem logical. However the relationship between the continuous flight conditions compared to the preparation flight condition was very weak. It appears that pilot’s awareness was reasonably similar to preparation time and no preparation time.
Relationship of metal perceived awareness to preparation time
|Flight in/out of the loop condition||Standard deviation (t score) at beginning of pilot’s control||Standard deviation (t score) at end of pilot’s control|
|Continuous verses no preparation time||3.17||-1.86|
|No prep time verses with preparation time||2.51||2.81|
|Preparation verses continuous||nil||nil|
12 U.S pilots were selected on a volunteer basis for this experiment. 10 pilots held a current commercial pilot licence while the 2 remainder pilots held a current airline transport pilot licence (Casner, 2010). 11 out of the 12 pilots also held a flight instructors certificate (Casner, 2010). Each pilots had between 500 and 30,000 hours of flight experience.
Each pilot performed 3 instrument approaches and missed approaches.
1. The control: The pilot flew a normal instrument approach and missed approach uninterrupted.
2. Preparation time: The pilot was given an out of loop experience by unplugging the headset and watching a comedy movie on a hand held device. The pilot was asked to plug the headset back in and given the charts in time for a 2 minute preparation period before the approach and missed approach.
3. No Preparation: The pilot was given an out of loop experience by unplugging the headset and watching a comedy movie on a hand held device. The pilot was asked to plug in the headset and given control of the airplane and the charts to fly the approach on arriving at the approach.
Casner had 3 research focus questions:
The first asking if “pilots can successfully assume the controls of an aircraft in the midst of a busy instrument flight procedure” (Casner, 2010, p. 2), This is an irrelevant question for all IFR pilots have received adequate training and are paid for their ability to fly the plane including conducting an instrument approach and missed approach, when required, competently.
The second investigates the “perceived workload, awareness, and the number of errors committed” (Casner, 2010, p. 2), by a pilot who fly’s continuously compared to an out of the loop pilot. This is the actual question that Casner has investigated and compiled data through this experiment.
The third question investigates the effect of preparation time on pilot performance for an instrument approach and missed approach (Casner, 2010,). This question is a little ambiguous for it does not differentiate between a negative or positive effect of preparation time on performance. Nor does it specify that the performance is being measured in terms of errors made through the procedure and the mental workload and awareness experienced by the pilot.
In this experiment the preparation time for an instrument approach and missed approach was varied from no preparation, 2 minutes preparation and continuous in the loop flight. An out of loop experience was created by removing the pilot instrument charts. Having the pilot unplug the headsets and focus their attention on a comedy movie on a handheld device. Pilots were told to avoid looking at any of the instrumentation for this would help maintain a mental awareness of the instrument approach.
The experiment took place in an airplane, a Cessna 172S that was equipped with a VOR navigation source and a conventional course deviation indicator (Casner, 2010). The aircraft had use of autopilot and an installed GPS receiver but these were not used (Casner, 2010). Each pilot wore view limiting devices (i.e. hood or foggels)
In the aircraft were the experimenter and the pilot.
The experiment concluded with a briefing. Pilots were told they would be flying 3 instrument approaches including the missed approach. The experimenter would be flying the airplane when the pilot was removed from the loop. The pilot was removed from the loop by unplugging the headset, having all charts taken away, and by refraining to look at the any instrumentation while the experimenter flew and to focus on a comedy movie being watched on a handheld device (Casner, 2010).
Each pilot was given the approaches in a different order that was randomly selected (Casner, 2010).
When the experimenter was flying he would set up the instruments and radios but the pilot will still need to further set up the instrumentation as he required on receiving control of the airplane (Casner, 2010).
When the pilot was flying the examiner would ask the pilot to estimate his perceived workload during each 60 seconds of the approach and missed approach by using the “instantaneous self-assessment (ISA) workload measurement scale” (Casner, 2010, p. 4) which gives an estimation between 0 and 100 in increments of 5.
The experimenter recorded pilot errors when the cropped up.
After flying all 3 full approach procedures the pilot filled out a self-assessment “comparative rating” (Casner, 2010, p. 4), form comparing their workload to each of the 3 approaches.
Casner used an “instantaneous self-assessment (ISA),” scale to record a verbal response from the pilot flying (as cited in Casner, 2010, p. 4), to measure the pilots workload experienced. It consists of a scale between 0 and 100 in increments of 5. It was chosen to minimize the intrusion on pilot as they focused on flying the approach (Casner, 2010).
“The awareness self-assessment instrument is a comparative ratings form first used by Vidulich and Hughes (as cited in Casner, 2010, p. 4), used to compare the awareness in relationship strength between the 3 flight preparation conditions stated (Casner, 2010, p. 4).
This research only took into account an out of loop experiment during an instrument approach and missed approach, which is a routine procedure in which all the information is readily in front of the pilot. However there is potential for study into further out of loop experiments involving more complex decision making such as emergency situations when the required information needs to be gathered and an awareness of the aircrafts state and position is important.
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