NTSB Identification: CHI91LA146.
The docket is stored on NTSB microfiche number 43818.
Accident occurred Sunday, May 05, 1991 in ANN ARBOR, MI
Probable Cause Approval Date: 06/02/1992
Aircraft: ROBINSON R22 BETA, registration: N2360K
Injuries: 1 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
THE PLT RPRTD THAT DURING FLT, HE NOTED RPM FLUCTUATIONS & A WARNING BUZZER. HE ADJUSTED THE THROTTLE TO 100% & NOTED THAT ALL GAGES WERE 'IN THE GREEN.' HE CHECKED THE CARBURETOR (CARB) HEAT GAGE & NOTED IT WAS ONE NEEDLE WIDTH ABOVE THE YELLOW SECTION & THAT THE OUTSIDE AIR TEMP WAS 9 DEG C (48 DEG F). WITH THESE INDCNS, HE DISCOUNTED CARB ICE & DID NOT APPLY CARB HEAT. SUBSEQUENTLY, THE ENG LOST ADDITIONAL POWER BEFORE THE PLT COULD REACH THE RWY. DURING AN EMERG LANDING, THE HELICOPTER ROLLED OVER. AN EXAM & SUBSEQUENT ENG RUN REVEALED NO MECHANICAL ANOMALIES, EXCEPT THAT THE CARB AIR TEMP GAGE WAS INDICATING 4 DEG C ABOVE THE ACTUAL TEMP. TEMP & DEW POINT AT ANN ARBOR WERE 51 & 50 DEG F, RESPECTIVELY. ACCORDING TO CARB ICE CHARTS, CONDITIONS WERE CONDUCIVE TO CARB ICE.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: LOSS OF ENGINE POWER DUE TO CARBURETOR ICE, AND THE PILOT'S FAILURE TO USE CARBURETOR HEAT. FACTORS RELATED TO THE ACCIDENT WERE: CARBURETOR ICING CONDITIONS, AND A FALSE INDICATION FROM THE CARBURETOR AIR TEMPERATURE GAGE.
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