Hazardous Events Scale - Civil


The Hazardous Event Scale (HES; Hunter, 1995) is a 10-item scale that assesses participants’ involvement in hazardous aviation events. This scale is based on the generally held premise that in most instances errors and other hazardous events do not lead to accidents because, for any of a number of reasons, the causal chain is broken. However, had the circumstances been slightly different (a little less fuel on board, a little heavier load, visibility slightly worse), then an accident might have occurred. It has been suggested that, disregarding any arguments about accident-prone personalities, those individuals who place themselves in hazardous situations more often are more likely to eventually experience an accident. The HES is proposed as either a predictor of eventual accident involvement, or as a surrogate measures in studies in which the preferred criterion (actual accident involvement) cannot be used.

Number of Items:
There are 10 items. However, the first item, “How many accidents have you been in (as an aircrew member)?” is often deleted, if the researcher intends to correlate the HES score with actual accident involvement.


Participants are asked to indicate how often during the previous 24 months they had been involved in one of the 10 events.

The response scale ranges from 0 to 6 or more. Responses of 6 or more are recorded as 6. Higher scores indicate the person had experienced more hazardous events.

NOTE: Some implementations of this scale only use “0, 1, 2, 3, 4 or more” as the response alternatives.

Simple summation of the responses.
Factor Composition: No factor analyses reported.

Reliability: Four separate studies yielded coefficient Alpha estimates of .64 to .65 for the 9-item scale (excluding accident involvement).

Construct Validity:

Several studies have correlated scores from the HES with self-reported accident involvement. These studies are summarized in the Normative Information section. Generally, positive, significant correlations were obtained between the HES and accident involvement for all the studies.

Normative Information:

Study 1
In the earliest study that included the items comprising the HES, Hunter (1995) conducted a nationwide statistical probability survey of 19,657 pilots. The response alternatives were 0, 1, 2, 3, 4, 5, and 6 or more. Responses for the nine hazardous events items (excluding accident involvement and items that did not appear in subsequent studies) were summed to produce a HES score (M = 6.89, SD = 5.91). For this sample, the HES correlated r = .23 (p < .01) with self-reported accident involvement. Coefficient alpha for this sample and nine-item scale was 0.65.

Study 2
As part of a web-based study of risk perception and risk tolerance among pilots, Hunter (2002) obtained item responses from 394 pilots on the ten-item version of the HES. To create a HES score, we excluded the item that asked about accident involvement and computed the sum of the nine remaining items. The resulting HES score had a mean = 3.16 (SD = 3.42). Pilots’ responses to the first (excluded) item from the10-item scale served as the criterion. As before, that variable was coded as zero or one (no accident reported, one or more accidents reported). Of the 394 respondents, 18 (4.6%) reported having been in an aviation accident during the previous 24 months. The HES score correlated r = .32 (p < .01) with this measure of self-reported accident involvement. Coefficient alpha for this sample and nine-item scale was 0.65.

Study 3
Lubner, Adams, Hunter, Sindoni, and Hellman (2003) conducted a retrospective, anonymous, case-control survey of 4,000 active U.S. pilots with a 42% response rate. As part of this study, they administered seven items from Hunter’s (1995) HES. They computed a HES score by taking the sum of the responses for those seven items. The mean for this HES score was 5.14 (SD = 4.96). For this study, two measures of accident involvement were available: self-reported accident involvement and case-control status based on NTSB records. Of the 1,333 pilots, 597 (44.8%) reported having been in an aviation accident at some point during their flying career. The HES score correlated r = .24 (p < .01) for this self-report measure. Correlating the HES score with case-control status yielded a correlation r = .26 (p < .01) for a sample 1,401 pilots. Coefficient alpha for this sample and seven-item scale was 0.64.

Study 4.
The ten-item HES was administered as part of a study to develop and evaluate a situational judgment test (SJT) for general aviation pilots (Hunter, 2003). The SJT and the HES were administered to 467 participants over the Internet. Item response data on the HES were available for 446 participants and these data were analyzed, as described above, to create a HES score (M = 3.06; SD = 3.39) based on nine of the items. The item concerning accident involvement was recoded (zero or one) as before. Of the 446 pilots, 24 (5.4%) reported having been in an accident during the previous 24 months. The correlation between HES and the self-reported accident status was r = .30 (p < .01). Coefficient alpha for this sample and nine-item scale was 0.65.


Hunter, D. R. (1995). Airman research questionnaire: Methodology and overall results. (DOT/FAA/AM-95/27). Washington, DC: Federal Aviation Administration.

Hunter, D. R. (2002) Risk perception and risk tolerance in aircraft pilots. (DOT/FAA/AM-02/17). Washington, DC: Federal Aviation Administration.

Hunter, D.R. (2003). Measuring general aviation pilot judgment using a situational judgment technique. International Journal of Aviation Psychology, 13, 373-386.

Hunter, D.R. (2006). Risk perception among general aviation pilots. International Journal of Aviation Psychology, 16, 135-144.

Lubner, M., Adams. R., Hunter, D. R., Sindoni, R.& Hellman, F. (2003) Risks for aviation occurrences among U.S. pilots by pilot training. 12th International Symposium on Aviation Psychology, Dayton, OH: April 14-17, 2003.

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