Revisiting the PC-12 Crash

Peter Garrison

Monday, August 24, 2015 at 10:55 PM ET

Verified

** The PC-12, with six aboard, had barely begun its trip
when the pilot lost control of the airplane.**

Key Takeaways:

The article uses the 2012 Pilatus PC-12 crash, where an instrument-rated pilot failed to intervene after an autopilot disconnect, as a case study for the dangers of uncontrolled spiral dives and subsequent inflight breakups.
A key takeaway is that an airplane trimmed for low speed can generate dangerously high G-forces during recovery from a high-speed spiral dive, leading to structural failure if the pilot attempts to level out too aggressively.
Proper recovery from an extreme spiral dive involves reducing power, leveling the wings while trimming nose down, and potentially deploying landing gear to increase drag, emphasizing the need to limit G-loads rather than making rapid pitch-up inputs.

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In my March Aftermath column on the 2012 crash of a Pilatus PC-12 in Florida, I faulted the National Transportation Safety Board for mixing up indicated and true airspeeds. Actually, it was I who misread the report. I am indebted to reader Timothy Burtch, an accident investigator with the NTSB, for pointing out that the maximum speed of 338 knots that the airplane reached in a spiral dive before it broke apart was, in fact, an indicated airspeed, not a true one, and that the airplane did, therefore, exceed its maneuvering speed by
175 knots as the report stated.

The Pilatus, with a family of six aboard, was climbing through FL 250 in IMC. It was at 109 kias, in a 25-degree right bank, deviating to avoid an area of rain, when the autopilot disengaged for unknown reasons. Presumably a chime sounded and a warning light illuminated, but the pilot seemingly did nothing to take control of the airplane. The baffling aspect of that accident was the pilot’s apparent failure to act even when the airplane was vertically banked and plunging downward at a horrific rate.