The Lingering Mystery of 'Undetermined Reasons'

When an accident’s cause is not easily found.

Peter Garrison

Tuesday, February 18, 2020 at 06:02 PM ET

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A Rutan VeriEze similar to the subject aircraft. Wikimedia

Key Takeaways:

The article discusses a 2007 VariEze crash initially classified as "loss of control for undetermined reasons," emphasizing the mystery surrounding such accidents.
Initial investigation focused on the aircraft's airbrake due to a prior reported fear by the pilot, but experts and the aircraft's designer, Burt Rutan, largely dismissed it as a cause for loss of control.
The author suggests a critical oversight in the NTSB's report, noting that while cables were examined, the VariEze's unique pushrod-based pitch control system was not explicitly mentioned as recovered or analyzed.
A sudden mechanical failure in the pitch control system, such as a loose bolt causing the stick to go slack, is hypothesized as a plausible, though unprovable, cause for the pilot's panicked cry and the resulting crash.

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When the National Transportation Safety Board announces the probable cause of an accident, it often makes use of certain stock phrases. One of the most common is: “loss of control for undetermined reasons.”

Unlike “controlled flight into terrain,” which can often be traced to an incorrectly selected radio frequency or a sectional chart left behind, loss of control for undetermined reasons remains mysterious. These are not the loss-of-control accidents that result from icing encounters or from a non-instrument-rated pilot flying into IMC; in those cases, reasons can at least be plausibly guessed. Undetermined reasons really are undetermined.