Count vs. Rate
The blueline shows the accident count (how many US helicopters had an accident in a month). The orange line shows the accident rate per 100,000 flight hours (the number of US helicopter accidents per month divided by the number of flight hours estimated to have occurred that month). While the two data sets look similar (both show that accidents were reduced in December and February), the accident rate provides more context about safety in our industry.
Counts Do Not Tell the Whole Story
Let’s say that Operator A and Operator B both had two accidents last year—sounds like they have similar safety records. But if you learned that Operator A flies 1,000 hours a year and Operator B flies 100,000 hours a year, then your opinion of their relative safety records would change.
Rates Provide Context
To compare safety performance, you need to consider the number of accidents (the count) AND the number of opportunities for accidents (in this case, the number of flight hours). In the example, Operator A has an accident rate of 0.002 per 100,000 flight hours. Operator B’s accident rate of 0.00002 per 100,000 flight hours is better by a factor of 100.
Underreported Flight Hours Affects Accident Rates
Many think that the helicopter industry underreports our flight hours, which increases the margin for error in calcuating the accident rate.
Fill Out Your GA Survey
The best way to ensure that we are looking at accurate accident rate data? Report your flight hours on the GA survey (www.aviationfleetsurvey.org). Help the FAA and the helicopter industry improve the accuracy of its accident data.
Did You Know?
The 2017 GA survey listed 10,511 rotorcraft operating in the United States. Visit bit.ly/GA-SurveyResults to see more of the information gathered by past GA surveys.
