Effects of Pilot Fatigue on Short-Haul Commercial Operations.

(A comparison between Low Cost Pilots versus Schedule Operations Pilots).

Fatigue has been cited as a causal factor to many aviation accidents and incidents. Jackson & Earl¹ conducted a research in 2006, to find evidence of increasing levels of fatigue faced by short haul commercial pilots especially with new operational requirements in both scheduled and low cost carriers. This article provides a meta-analysis done on the original results.

Illustration 1 shows that, regardless of age, both low cost pilots and schedule operations pilots, claimed to experience similar amount of fatigue [effect size (d)≤ 0.3]. For Cohen's effect size (d)³, an effect size of 0.2 to 0.3 is considered as a "small" effect, around 0.5 as a "medium" effect and 0.8 to infinity, a "large" effect.Therefore, despite the differences in nature of operations and work schedules, short haul pilots, in general, were highly susceptible to fatigue.

Illustration 1: Comparison between low cost and schedule operation pilots
	Low Cost Pilots (n = 55)		Schedule Operations Pilots (n = 94)
Measures	Mean	Std Devt	Mean	Std Devt	Effect Size (d)	Effect Interpretation
Age*	39.8	8.0	37.9	9.8	0.2	small
Physical fatigue **	12.9	3.4	11.7	3.2	0.3	small
Psychological fatigue **	6.2	2.1	5.7	1.8	0.2	small
Global fatigue **	19.1	5.1	17.4	4.6	0.3	small
^* Denotes Age range of 21-59. ** Based on the 11-item chronic fatigue scale (CFS) questionnaires² .

From Illustration 2, the comparison shows that the sectors flown per duty for study group is not significant (p value <0.05). Therefore, from the reports, both, low cost and scheduled airline pilots felt fatigue despite their own work schedules. Notably, Illustration 2 does show a significantly higher prevalence of psychological fatigue reported by low cost pilots (p value > 0.05).

Illustration 2 : Fatigue responses (mean difference)
Pilot (low cost vs schedule ops)	Mean difference	p value ^@	Level of significance
Sectors flown per duty	1.0	0.02	no significance
Physical fatigue	1.2	0.04	no significance
Psychological fatigue	0.5	0.09	significant
Global fatigue	1.7	0.03	no significance
(@: p value< 0.05 - no significance; p value > 0.05 - significant).

Illustration 3 shows that a majority of short haul pilots, low cost and scheduled operations pilots, claimed to have operated aircrafts while feeling severe fatigue and felt that their judgment were impaired while flying. Therefore based on anecdotal (Illustration 3) and quantified (Illustration 1 & 2) evidence, short haul pilots does experience high level of fatigue that affects their performance and judgement.

Illustration 3 : Fatigue responses from short haul pilots
	Yes	No	Not Sure
Fatigue measure on the CFS (score ≥ 4)*	75%	25%	-
Feel tired with impaired judgment while flying	80%	19%	1%
* Based on the 11-item chronic fatigue scale (CFS) [Range 2-31].

Study scope

The collected data are collated from 162 short haul pilots (55 pilots- low cost airlines & 94 pilots- schedule operations airlines). The results from the general aviation pilots (13 pilots) were excluded from the study to provide a clearer assessment of commercial operations. Other factors, for example, duty hours were not taken into account and could have a significant impact in the results. Still, the results are of operational relevance in maintaining safer operations, in terms of fatigue management in the short haul industry.

Methods

Research approach

This was an exploratory research into the subjective fatigue levels reported by short hauls pilots, in order to ascertain whether fatigue is caused by the differences in work schedule between low cost and scheduled operations airlines pilots.The collected data was based on an anonymous Internet based questionnaire hosted on the Professional Pilots’ Rumours Network (PPRUNE) website for a month.

Sample

Data was collected from 162 short haul commercial pilots. The average (median) pilot was male with a mean age of 38.3 years. The pilots had held a Commercial Pilot’s License or an Airline Transport Pilot’s License for a mean duration 11.9 years (range 1-39). The mean numbers of sectors performed per day was 4 (range 1-20).

Variables

Jackson & Earl (2006)¹ used 11- item chronic fatigue scale (CFS) which gives a physical, psychological and global fatigue scores in order to ascertain the severity of the respondents’ fatigue levels in a binary classification.

Chronic Fatigue Scale (CFS)/ Chalder Fatigue Scale (2006)² was scored using the 0–3 method for scoring each question (0 ‘Less than usual’, 1 ‘No more than usual’, 2 ‘More than usual’ and 3 ‘Much more than usual’).

Chadler Fatigue Questionnaire² (image embedded from MEACTIONUK.ORG.UK ).

The items chosen for analysis in this article: Physical, psychological and total fatigue score were chosen because it represented markers from the chronic fatigue scale that were quantifiable.

Data analysis

This meta-analysis uses descriptive statistics, namely central tendency and dispersion from the original research to provided more quantifiable evidence of fatigue from the pilots’ perspective. From this analysis, it can be concluded that there are identifiable fatigue problems faced by short haul pilots regardless of the type of operations.

References

JACKSON Craig A & Laurie EARL (2006). Prevalence of fatigue among commercial pilots. Occupational Medicine, 2006, volume 56, pages 263-268.
CHALDER Trudie, Peter D White & Michael SHARPE (2006). Pacing,graded activity,and cognitive behaviour therapy; a ramdomised evaluation.Pg 162. Retrieved from http://www.meactionuk.org.uk/FULL-Protocol-SEARCHABLE-version.pdf.
Effect Size Retrieved from http://en.wikipedia.org/wiki/Effect_size.

+++Footnotes+++

^@ P-Value of 0.05 is referred to in this research as a significance level or level of significance.
Other casual factors of fatigue including duty time and time of day could have provided a more reliable and useful result.

Author

TT (2013). Massey University, Singapore .Thomastoh380

Want to know more?

Prevalence of fatigue among commercial pilots: The original research paper regarding the prevalence of fatigue among commercial pilots
CFS questionnaire and sample (PACE): Sample of the 11- item CFS questionnaire
CFS Fatigue Scale: Interactive sample of the CFS questionnaire.
Statistical_significance: Description of Statistical significance.
P-Value: Description of P-Value in statistic.