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ASN Wikibase Occurrence # 152196
Last updated: 21 October 2019
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Date:02-JAN-2013
Time:20:57
Type:Silhouette image of generic B407 model; specific model in this crash may look slightly different
Bell 407
Owner/operator:Mercy Air
Registration: N445MT
C/n / msn: 53959
Fatalities:Fatalities: 3 / Occupants: 3
Aircraft damage: Written off (damaged beyond repair)
Category:Accident
Location:near Clear Lake, IA -   United States of America
Phase: En route
Nature:Ferry/positioning
Departure airport:Mason City, IA
Destination airport:Emmetsburg, IA (IA76)
Investigating agency: 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 airmenís 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.

Probable Cause: The pilotís inadvertent encounter with localized icing conditions and his subsequent in-flight loss of helicopter control.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20130102X35708&key=1


Revision history:

Date/timeContributorUpdates
03-Jan-2013 02:44 gerard57 Added
03-Jan-2013 03:08 gerard57 Updated [Location]
03-Jan-2013 08:15 Geno Updated [Time, Cn, Operator, Location, Departure airport, Destination airport, Source, Narrative]
17-Jan-2013 09:09 Geno Updated [Time, Location, Destination airport, Source, Narrative]
03-Mar-2013 10:35 TB Updated [Time, Operator, Location, Departure airport, Destination airport, Source, Narrative]
18-Aug-2014 09:34 Aerossurance Updated [Narrative]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
28-Nov-2017 14:05 ASN Update Bot Updated [Operator, Other fatalities, Nature, Departure airport, Destination airport, Source, Narrative]

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