Incident Bell 407 N373RL, 11 Nov 2014
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ASN Wikibase Occurrence # 171446
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Type:Silhouette image of generic B407 model; specific model in this crash may look slightly different    
Bell 407
Owner/operator:Rotorcraft Leasing Company LLC
Registration: N373RL
MSN: 53373
Fatalities:Fatalities: 0 / Occupants: 4
Other fatalities:0
Aircraft damage: None
Location:Gulf of Mexico, off LA -   United States of America
Phase: Initial climb
Departure airport:VK189 offshore installtion, GOM
Destination airport:MP301 offshore installtion, GOM
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Ditched following a loss of engine power shortly after take off. The pilot and three passengers were uninjured. The helicopter sustained no damage during the ditching.

The pilot reported that, about 30 seconds after takeoff from an off-shore platform, about 400 ft mean sea level, the helicopter experienced a series of compressor stalls and engine surges. The pilot adjusted the collective pitch and began a slow descent. After the pilot decreased the engine power, the surges and stalls ceased. However, when the pilot began increasing power while attempting to return to the platform, the surges and stalls recurred. The pilot reported hearing the low rpm horn and observing that the power turbine gauge was near the redline. The pilot subsequently entered an autorotation, inflated the floats, flared the helicopter, and then landed it on the water. The pilot estimated from the time of the initial compressor stall to water contact was approximately 15 to 30 seconds.

The helicopter did not sink. The pilot subsequently deployed the life rafts and got a verbal response from all the passengers that they were "ok." He directed the passengers to collect their belongings and a first aid kit in case it was needed. They got into the life raft on the left hand side of the helicopter.

The bleed valve was bench tested by the operator. Testing revealed the bleed valve closed early. Disassembly revealed corrosion was present in the bleed valve and corrosion flakes were found in the bleed valve exit orifice. Witness marks consistent with wear were found on the bleed valve bellows face near the exit orifice.

An early closing bleed valve could contribute to surging in the Ng range where it would normally be open, engine power at two percent below power assurance chart levels could contribute to engine surging, and a faulty ECU or T1 sensor could contribute to engine surging. Based on the information available, it cannot be concluded that they had an effect on the subject engine during the incident event.

Subsequent to the incident, the operator made the decision to revise the bleed valve overhaul schedule from 1,500 hours to 750 hours. Additionally, the operator's managers will increase surveillance on engine water wash and chemical wash procedures to insure proper techniques are used when performing these tasks.

The National Transportation Safety Board determines the probable cause(s) of this incident as follows: Engine power surges during takeoff for reasons that could not be determined during postaccident testing of the engine and the engine control unit.



Accident investigation:
Investigating agency: NTSB
Status: Investigation completed
Download report: Final report

Revision history:

20-Nov-2014 09:42 Aerossurance Added
08-Dec-2015 10:55 Aerossurance Updated [Destination airport, Narrative]
08-Dec-2015 13:16 Aerossurance Updated [Operator, Narrative]
23-Sep-2016 14:33 Aerossurance Updated [Source]
23-Sep-2016 15:02 Aerossurance Updated [Departure airport]
30-Nov-2016 20:58 Aerossurance Updated [Location]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
14-Jan-2023 12:14 Aerossurance Updated [Departure airport, Destination airport, Source]

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