Methodology
How we measure
Five principles sit under every figure we publish. They are stated here so any reader can hold us to them.
1. Scope
The record covers US-registered fixed-wing turbine airplanes (business jets and turboprops) in business use: owner-flown and corporate flights under Part 91, fractional programs under Part 91 subpart K, and on-demand charter under Part 135. Scheduled airline operations, agricultural aircraft and helicopters are outside it. Hull loss comes first; liability measures follow as the record supports them.
2. Exposure is counted in aircraft-years
A rate is events divided by exposure. Our exposure is every year each aircraft spent on the US register, across the whole fleet, including aircraft that have since left it. Aircraft-years measure time on the register, not hours flown.
3. Events
An event is an accident. Every rate is a count of accidents over a count of aircraft-years, on a stated scope and window.
4. Publication floors
No rate is published where exposure falls below 500 aircraft-years. Small groups produce rates that swing on one event, and a rate that swings on one event tells an underwriter nothing. Where a figure is withheld for this reason, the page says so.
5. Every figure is dated, versioned and restated in public
Investigations close months after an accident, damage findings change, and our own methods improve. When a published figure moves, we record the old value, the new value, the date and the reason in the restatement log. Old values are not deleted.
Expected loss
An aircraft’s expected hull loss is a range for the next twelve months, set beside its class. Frequency and severity are modeled separately on the full US turbine record and tested out of time, on recent years the models never saw, against the class rate a filed manual uses. No information from after a loss is ever an input, and estimates are restated when a model is rebuilt.
Each model ships with its validation and full documentation, organized to ASOP No. 56, Modeling, so an actuary relying on the output has what the standard asks for. The documentation is provided to clients and their actuaries under agreement.
What we do not publish
Figures for any identified aircraft, operator or person; rates for individual aircraft families, beyond the one comparison in our research; and the internal workings of how the record is assembled. The first two are what clients pay for. The last is ours.
See what the record knows about your book.
Send tail numbers or a schedule. Someone will reply within one business day, and the work runs on your own aircraft.