Pilot Debrief

ROBINSON HELICOPTER COMPANY R44 II near Lyons, NE — 2019-08-03

Final reportCEN19LA250
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Date
2019-08-03
Location
Lyons, NE, USA
Aircraft
ROBINSON HELICOPTER COMPANY R44 II
Registration
N440EM
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Maneuvering

Probable cause

The engine's low cylinder compression, which resulted in low rotor rpm and a subsequent dynamic rollover following landing on soft terrain.

NTSB narrative

The airline transport pilot of the agricultural aerial application flight stated that as the helicopter entered the field to be sprayed, the low rotor rpm annunciation sounded. He attempted to recover rotor rpm, but the rpm continued to decay rapidly. He then used the remaining rotor rpm to cushion a landing onto the field. As the helicopter touched down, it slid about 150-200 ft before the skid dug into soft dirt and the helicopter rolled over. Post-accident examination of the engine by the operator revealed that the no. 6 cylinder had more leakage/lower compression than the previous 100-hour recorded compression checks. Reduced compression on one or more cylinders would have reduced excess power available to maintain a rotor RPM and altitude.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have aborted the aerial application before engine issues arose.

NTSB coding

Evidence available

  • 4 docket documents
View NTSB final reportView NTSB docket

Docket documents4

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