Loss of control Accident Robinson R44 Raven II N7511D,
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ASN Wikibase Occurrence # 238577
 
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Date:Thursday 2 July 2020
Time:09:00 LT
Type:Silhouette image of generic R44 model; specific model in this crash may look slightly different    
Robinson R44 Raven II
Owner/operator:Direct Aerial Services, LLC
Registration: N7511D
MSN: 1252
Year of manufacture:2002
Total airframe hrs:1834 hours
Engine model:Lycoming Engines O-540-F1B5
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:Welsh, Jefferson Davis Parish, LA -   United States of America
Phase: En route
Nature:Private
Departure airport:Welsh, LA (6R1)
Destination airport:Welsh, LA
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
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.


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.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN20LA286
Status: Investigation completed
Duration: 1 year and 8 months
Download report: Final report

Sources:

NTSB CEN20LA286

Location

Revision history:

Date/timeContributorUpdates
24-Jul-2020 20:40 Captain Adam Added
26-Aug-2020 08:19 ASN Update Bot Updated [Time, Cn, Operator, Departure airport, Source, Narrative]
01-Jul-2022 09:07 ASN Update Bot Updated [Time, Operator, Other fatalities, Destination airport, Source, Narrative, Category, Accident report]
01-Jul-2022 09:08 harro Updated [Phase, Narrative]

Corrections or additions? ... Edit this accident description

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