Avoiding Distractions in Accident Reports

Wed, Dec 26, 2007 — David Evans


Various criticisms have been generated in recent weeks over unimportant and potentially misleading phraseology in accident reports produced by the National Transportation Safety Board (NTSB).

A pertinent example comes from an anonymous but credible source, a long time aviation accident investigator, who said, “I am once again confronted with an irritant found in virtually every VFR [visual flight rules] NTSB investigation report.”

The source of ire is the prominent phrase in the very first paragraph of an accident report that “no flight plan was filed.” An examination of the NTSB report of 12 March 2006 helicopter accident (Report No. SEA06LA065) reveals that the statement was made without further comment. As such, the statement can leave the uninformed reader with the impression that the pilot did something wrong by not filing a flight plan.

The report does not expand on the statement to show how the absence of a flight plan contributed to the accident or reduced aviation safety. Nor does the NTSB report explain that a flight plan was not required for the intended flight or that the regulatory requirement was met by a Flight Notification or Flight Itinerary.

The statement, made without further comment, gives the impression that the pilot was somehow reckless and a scofflaw, thumbing his nose at the regulations.

“You can imagine my surprise when I had the opportunity to examine the engine and found the compressor spool corn-cobbed and the turbines melted,” says the source.

One can quibble. For one thing, the report contains awkward phraseology. For example, the logging operation the helicopter – a Kaman K-1200 – was supporting was described as , quote, a “lumbering flight,” which would suggest a lack of maneuverability as much as a logging operation.

And the report goes into some detail regarding the malfunction:

“A teardown of the engine sub-components determined that the splines on the drive end of the shouldered shaft between the over speed and tachometer drive gearbox assembly and the power turbine governor had worn away to the point where drive power was not being received by the turbine governor. Without drive input, the turbine governor sensed a continuous under speed, and therefore increased fuel flow, resulting in an increase in turbine speed …

“Although the helicopter experienced an over speed of both the power turbine and the main rotors, the pilot stated that he was too busy moving the load of logs away from the people on the ground, and too consumed with finding a reasonable place to land the helicopter, to take time to look back inside to analyze the rpm gauges.

The statement about a flight plan not having been filed was not germane to the accident. Worse, the statement inferred that the pilot should have filed a flight plan, when he was not required to do so. The statement comes under the heading of crack filler – as such, it provides no strength to the subsequent analysis of the factors that did contribute to the crash. (For the report, see )

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