Pilot Debrief

BELL HELICOPTER 407 near Clear Lake, IA — 2013-01-03

Final reportCEN13FA122
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Date
2013-01-03
Location
Clear Lake, IA, USA
Airport
MCW
Aircraft
BELL HELICOPTER 407
Registration
N445MT
Category
Helicopter
Highest injury
Fatal
Fatalities
3
Phase of flight
Climb

Probable cause

The pilot’s inadvertent encounter with localized icing conditions and his subsequent in-flight loss of helicopter control.

NTSB narrative

GPS tracking data revealed that, after departure, the helicopter proceeded westbound about 600 ft above ground level (agl), following a roadway. About 6 minutes after liftoff, when the helicopter was about 3/4 mile south of the accident site, it turned right and became established on a northerly course. The helicopter subsequently turned left and appeared to be on a southerly heading at the final data point. Shortly before beginning the left turn, the helicopter entered a climb, reached an altitude of about 1,800 ft agl, and then entered a descent that continued until impact. Weather observations from the nearest Automated Surface Observing System, located about 7 miles east of the accident site, indicated that the ceilings and visibility appeared to be adequate for nighttime helicopter operations and did not detect any freezing precipitation. Although an airmen's meteorological information advisory for icing conditions was current for the route of flight, and several pilot reports of icing conditions had been filed, none of the reports were in the immediate vicinity of the intended route of flight. Witnesses and first responders reported mist, drizzle, and icy road conditions at the time of the accident. It is likely that the pilot inadvertently encountered localized icing conditions, which resulted in his subsequent in-flight loss of helicopter control. A postaccident examination of the helicopter revealed no preimpact failures or malfunctions. The engine control unit recorded engine torque, engine overspeed, and rotor overspeed events; however, due to their timing and nature, the events were likely a result of damage that occurred during the impact sequence. Evidence also indicated that the cyclic centering, engine overspeed, and hydraulic system warning lights illuminated; it is also likely that their illumination was associated with the impact sequence. Further, the engine anti-ice status light was illuminated, which was consistent with the activation of the anti-ice system at some point during the accident flight.

Analysis

Primary failure mode
Controlled flight into terrain
First missed decision gate
Pilot could have aborted the flight due to icing conditions and low visibility.

NTSB coding

Evidence available

  • ADS-B / radar
  • Photos
  • 30 docket documents
View NTSB final reportView NTSB docket

Docket documents30

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