Pilot Debrief

Robinson R44 near Welsh, LA — 2020-07-02

Final reportCEN20LA286
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Date
2020-07-02
Location
Welsh, LA, USA
Aircraft
Robinson R44
Registration
N7511D
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Climb

Probable cause

A partial loss of engine power while in flight due to corrosion of engine components, which resulted in a loss of control and a subsequent impact with terrain.

NTSB narrative

The pilot was flying the helicopter to a local area farm to wash and clean the helicopter. During the flight, the low rotor RPM horn activated, and the helicopter sustained a partial loss of engine power. The pilot immediately lowered the collective and applied power to no avail, so he elected to land the helicopter immediately. During the off-field emergency landing, about 3 to 5 ft off the ground, the helicopter started to spin to the right. The pilot applied the left pedal and “rolled off” the throttle to arrest the spin; however, the helicopter continued to spin. The helicopter impacted a flat grass field and came to rest on its left side. The helicopter sustained substantial damage to the fuselage, tailboom, and empennage. The camshaft and tappet bodies from the engine were examined and it was determined that they were worn and had spalled areas on the camshaft lobe for the No. 1 cylinder exhaust valve and its associated tappet body. Various particles were found in the engine oil filter. The oil suction screen had deterioration and holes in it due to corrosion. These conditions would have allowed debris to bypass the screen. It is likely the camshaft lobe for the No. 1 cylinder exhaust valve and its associated tappet body sustained corrosion pitting and some of the particles found in the engine oil filter were from these components. The oil suction screen failed from erosion-corrosion, preventing it from performing its function of filtering debris. The degradation and failure of these engine components resulted in a partial loss of engine power while in flight. When the corrosion sequence initiated on these various engine parts could not be determined based on the available evidence.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Pilot could have conducted a thorough preflight inspection for engine issues.

NTSB coding

Evidence available

  • Photos
  • 9 docket documents
View NTSB final reportView NTSB docket

Docket documents9

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