For the second year in a row, U.S. Federal Aviation Regulations Part 121 and Part 135 scheduled (commuter) operations resulted in no fatalities, according to preliminary data from the U.S. National Transportation Safety Board (NTSB).1 Part 135 on-demand (air taxi) flights, however, had the most fatal accidents and fatalities since 2008.
The accident rates for scheduled Part 121 flights and scheduled Part 135 flights favored Part 121 flights. The former had a rate of 0.314 accidents per 100,000 departures, the latter 0.714 accidents per 100,000 departures, or 2.3 times the Part 121 rate. The contrast based on rates per 100,000 flight hours was even starker: 0.162 for Part 121 versus 1.303 for commuter flights, making the commuter rate eight times that for Part 121 air carriers.
Departure information was unavailable for Part 135 on-demand operations, but the rate for all accidents per 100,000 flight hours showed nearly the same discrepancy: 2.4 times the rate of nonscheduled Part 121 operations. The rate for commuters was 1.303, that for on-demand flights was 1.500, 15 percent higher.
The term “accident,” which covers a lot of sins, is an inexact metric for risk management. The NTSB endeavors to be more descriptive by classifying accidents as major, serious, injury or damage in descending order of severity.2 Part 121 operations have enjoyed two years in the 2002–2011 decade with no major accidents, and 2011 was one of them. On top of that, there were no serious accidents, the next-most significant category, for the second successive year.
The 2011 rate per million flight hours of Part 121 major accidents — zero — compares with an average rate of 0.108 for the 2002–2010 period.3 The rate of serious accidents in the nine years previous to 2011 averaged 0.090, versus zero in 2011. The injury accident rate, 1.070 per million flight hours in 2011, was up from the 0.742 average from 2002 to 2010.
In Part 121 scheduled operations, there were 28 accidents in 2011, one more than in 2010 and less than the average 29.7 for the 2002–2010 stretch. The accident rate per 100,000 departures in 2011, at 0.314, was the highest since 2003 and above the average for the previous nine years, 0.288.
Part 121 nonscheduled operations — cargo flights and some charter flights in transport category airplanes — resulted in three accidents in 2011, none fatal. It was the first year since 2006 with no fatal accidents in this industry segment. The number of accidents matched that of 2010, and was less than the 2002–2010 average of 5.2. The 2011 accident rate per 100,000 departures, 1.987, was an increase over 2010’s 1.801.
Part 135 scheduled (commuter) operations had no fatal accidents for the fifth straight year. There were four accidents in 2011, down from six in 2010; the average for the previous nine years was 4.4. The 2011 rate, 0.714 accidents per 100,000 departures, was a 29 percent improvement on 2010’s 1.011. The average rate for 2002–2010 was 0.800.
Two years earlier, in 2009, the number and rate of fatal accidents for Part 135 on-demand (air taxi) operations showed an impressive year-over-year improvement (ASW, 4/10, p. 48). That now appears to have been a one-off. Numbers and rates of fatal accidents rose in 2010 and 2011. In 2011, there were 16 fatal accidents, up from six in 2010. The fatal accident rate per 100,000 flight hours was 0.48, compared with 0.19 in 2010. The rate for all accidents per 100,000 flight hours rose from 1.00 in 2010 to 1.50 in 2011.
- The NTSB classifications are as follows:Major — an accident in which any of three conditions is met: A Part 121 aircraft was destroyed, or there were multiple fatalities, or there was one fatality and a Part 121 aircraft was substantially damaged.
Serious — an accident in which at least one of two conditions is met: There was one fatality without substantial damage to a Part 121 aircraft, or there was at least one serious injury and a Part 121 aircraft was substantially damaged.
Injury — a nonfatal accident with at least one serious injury and without substantial damage to a Part 121 aircraft.
Damage — an accident in which no person was killed or seriously injured, but in which any aircraft was substantially damaged.
- All averages in this article are means.
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