Premium on Safety - Issue 44, 2022 - 10

LESSONS LEARNED
Missing Pieces
Discerning a plausible, detailed probable cause isn't always
possible without modern flight data recording
BY DAVID J. KENNY
Investigations of accidents in light aircraft are sometimes hindered
by the lack of crucial bits of information-in turn limiting the lessons
they might otherwise inform. When an airplane or helicopter is lost
at night in a rural area, even its location may be difficult to pinpoint
unless it was under radar control or transmitting ADS-B position
signals. In the absence of cockpit voice and flight data recorders-
and of data logging in older aircraft-there's no way to determine
what control inputs were made when or the cockpit situation that
produced them. Even when the formidable forensic skills of NTSB
specialists can reconstruct what happened, it may be impossible to
learn how, or why.
At 22:40:18 Central Standard Time on November 18, 2018, a
Cessna 441 Conquest II disappeared from radar contact. The air
ambulance flight had departed from the Bismarck Municipal Airport
in Bismarck, North Dakota, at 22:31 on a positioning flight to Sloulin
Field in Williston, North Dakota, operating under an IFR clearance
with a filed altitude of 14,000 feet. No distress calls were received.
The Conquest's last radio transmission was the pilot's readback of
Bismarck Departure Control's clearance direct to Williston as the
airplane climbed through 2,600 feet.
Between 22:41:05 and 23:08:13, repeated radio calls were made by
Bismarck Approach, Minneapolis ARTCC, and a commuter airliner
on approach to Bismarck. There was no reply. Search and rescue
efforts were initiated, directed toward the area of the last radar hit,
and the wreckage was discovered roughly 20 miles northwest of
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Bismarck around three hours later. The debris field was nearly half a
mile long and some 750 feet across, oriented north to south.
The call to pick up a patient at Williston had come in at 20:49. The
pilot obtained an online weather briefing at 21:59 and filed an IFR
flight plan at 22:27, estimating 45 minutes en route at 281 knots
airspeed. Fuel on board was listed as three hours 30 minutes,
and the pilot did not file an alternate airport. He received his IFR
clearance one minute later and was cleared to take off from Runway
31. In addition to the pilot, a paramedic and a flight nurse were on
board. Prevailing weather included 10 miles visibility beneath an
Even when the formidable forensic skills
of NTSB specialists can reconstruct what
happened, it may be impossible to learn
how, or why.
overcast layer at 2,400 feet, northeasterly winds at 9 knots, and a
temperature and dew point of -4 degrees and -6 degrees Celsius,
respectively. AIRMETs Sierra for IFR conditions and Zulu for icing
were in effect, and weather radar depicted a large area of light
snow north of Bismarck.
Radar track data showed that the Conquest climbed to 14,000 feet
on a direct track to Williston. One minute after leveling off, however,
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