Recalibrating the flying hours for the Cirrus fleet - Pull early, pull often! - Safety and Training Programs - Cirrus Owners and Pilots Association

Recalibrating the flying hours for the Cirrus fleet

In the past few months, COPA has worked with Cirrus Aircraft engineering to recalibrate the estimates of flying time for the 5,300 aircraft produced since mid-1999.

The Cirrus reliability engineering team maintains a database of aircraft hours by serial number based on information gleaned from warranty cards, service bulletins and AD compliance cards, and other sources. They then fit a Weibull distribution commonly used for failure analysis and reliability engineering. From that distribution, one can estimate the flying time for the whole fleet.

Cirrus Aircraft shares that flying time data with COPA so that we can calculate the accident rate versus 100,000 hours of flying time in the Cirrus fleet.

As you might guess, this methodology of using warranty cards gives great accuracy for the newer planes in the fleet but overlooks most out-of-warranty planes. (One joking suggestion was to issue an AD so that all airworthy airplanes, no matter their age, would have to report their Hobbs time. Cirrus didn't like that idea at all!)

With the 10-year life limit of the CAPS parachute system, we have an opportunity to gather data from these older airplanes. Unfortunately, there is no requirement for Service Centers to report to Cirrus any information on the installation of the parachutes. But with only a limited number of SCs qualified to do parachute repacks, there are fewer sources of data.

At Oshkosh 2012, I met with three of the most active SCs and encouraged them to review their records and share the Hobbs time of planes that they had already done parachute repacks.

With those three SCs, I quickly obtained 64 data points (out of about 300 eligible aircraft). The results were pretty surprising. The lowest time was only 376 hours -- for a 10-year old SR22! The highest time was 3209 hours. The average was 1271 and the median was 1143 (indicating that more planes were below average hours).

Cirrus Aircraft expanded the data collection and updated the parameters of their Weibull distribution. The result drops the estimated flying time by about 20 percent. That is, the fleet crossed the 5,000,000 hour number about August 2012. And the annual flying time is now estimated at 700,000 hours per year.

What remains unchanged is the observation that new Cirrus aircraft fly a lot of hours. That data was always highly accurate for the fleet. But now we know that older Cirrus aircraft fly much less than new aircraft, just as many of you suspected. Only now, we have some better data to work with.

My updated accident statistics are now using those recalibrated fleet hours.

 

Cheers
Rick

Comments
  • Great work Rick.  So hard to get good denominators in most GA aircraft.

  • Rick, you didn't mention who was flying that aircraft with the highest time?

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