Aircraft Accident/Incident Report

Gulf Of Mexico, -- 00000
Sunday, May 11, 2003 15:33 CDT

NTSB Narrative Summary Released at Completion of Accident

The helicopter, which had a FADEC controlled turboshaft engine installed, was in cruise flight (about 800 feet AGL) over open ocean water when the FADEC FAIL aural warning sounded, followed closely by sound of the LOW ROTOR RPM horn. Simultaneously, the LOW ROTOR RPM, FADEC FAIL, and FADEC FAULT cockpit caution lights illuminated. The 8,300-hour helicopter pilot attempted to regain the RPM's with no result. The FADEC AUTO/MANUAL indicator light/button showed the engine control mode to be in the "AUTO" condition. The pilot recalls that the Ng was approximately 89%. The pilot stated that about 10 seconds elapsed from the onset of the event to cross checking the Ng. The pilot then depressed the AUTO/MANUAL button and switched to the MANUAL mode. He then increased the throttle above the 90% detent to try to regain rotor RPM's. He recalled that the light displayed "MANUAL", and that the FADEC FAIL aural warning ceased after the button was depressed. While descending, on three separate occasions, the pilot attempted to increase the throttle which were accompanied by three uncommanded right yaws, approximately 1-2 seconds apart. During the third uncommanded yaw, the ENGINE OUT audio sounded and the ENGINE OUT light illuminated (these occur when Ng drops below 55%). The pilot then entered a full autorotation, deployed the skid mounted emergency float system and landed upright on the water. Metallurgical examination of the 1st thru 4th stage turbine wheels and 1st thru 3rd stage turbine nozzles, revealed that all associated damage was due to extreme over-temperature operation. The manual mode schedule of the Hydro-mechanical Unit (HMU) was found within limits, and the auto mode schedule had a flow shift of +10 to +15 PPH. Evaluation and testing of the Electronic Control Unit (ECU) and its sub-components revealed a shorted condition on the ECU -15V power supply. Disassembly of the ECU and tests of the Interface (IF) and Power (PWR) circuit boards revealed that the C321 capacitor (p/n CDR33BX104AKUR) on the IF board was found thermally distressed and was measured at .58 ohms. The C321 is a high frequency bypass capacitor from -15V to ground. The PWR board was also visually inspected and the CR423 diode was found thermally stressed. According to the manufacturer, the CR423 diode provides rectification on the -15V power supply and was likely stressed as a result of the shorted C321 capacitor. The C321 capacitor was removed from the IF board and there was no longer a short on the -15V power supply. The ECU was re-assembled, operated, and passed a functional acceptance test after removal of the C321 capacitor. The shorted condition of the C321 capacitor forced the -15V power supply to a low voltage condition and a significant current draw, resulting in the rectifying diode to overheat. According to the manufacturer, the -15V power failure of the ECU resulted in the HMU to revert to manual fuel metering. In the manual mode, the engine would have overspeed protection, but not overtemperature protection.

NTSB Probable Cause Narrative

The short circuit of the C321capacitor in the Electronic Control Unit (ECU) that resulted in a single-point failure of the ECU's -15V power supply which disengaged/reverted the Hydro-mechanical Unit (HMU) from automatic to manual fuel control. Factors contributing to the accident were the pilot's attempted remedial actions in the manual mode that resulted in the engine over temperature and loss of power, and the lack of suitable terrain for the forced landing.

Event Information

Type of Event Accident
Event Date 5/11/2003
Event Day of the Week Sunday
Time of Event 1533
Event Time Zone Central Daylight Time
Event City Gulf Of Mexico
Event State GULF OF MEXICO
Event Country --
Zipcode of the event site 00000
Event Date Year 2003
Event Date Month 5
MidAir Collision Indicator No
On Ground Collision occurred ? No
Event Location Latitude 294112N
Event Location Longitude 0911018W
Event Location Airport --
Event Location Nearest Airport ID --
Indicates whether the acc/inc occurred off or on an airport Off Airport/Airstrip
Distance from airport in statute miles --
Degrees magnetic from airport --
Airport Elevation --
Weather Briefing Completeness --
Investigator's weather source Witness
Time of the weather observation
Direction of event from weather observation facility (degrees) --
Weather Observation Facility ID --
Elevation of weather observation facility --
Distance of event from weather observation facility (units?) --
Time Zone of the weather observation --
Lighting Conditions Day
Lowest Ceiling Height --
Lowest Non-Ceiling Height 2000
Sky/Lowest/Cloud Conditions Scattered
Sky Condition for Lowest Ceiling None
Visibility Runway Visual Range (Feet) --
Visibility Runway Visual Value (Statute Miles) --
Visibility (Statute Miles) 7
Air Temperature at event time (in degrees celsius) 32
Dew Point at event time (in degress fahrenheit) 25
Wind Direction (degrees magnetic) 210
Variable Wind Indicator Wind direction could be determined
Wind Speed (knots) 5
Wind Velocity Indicator --
Wind Gust Indicator Not Gusting
Wind Gust (knots) --
Altimeter Setting at event time (in. Hg) 29.95
Density Altitude (feet) --
Intensity of Precipitation --
METAR weather report --
Event Highest Injury None
On Ground, Fatal Injuries --
On Ground, Minor Injuries --
On Ground, Serious Injuries --
Injury Total Fatal --
Injury Total Minor --
Injury Total None 4
Injury Total Serious --
Injury Total All --
Investigating Agency NTSB
NTSB Docket Number (internal use) 18111
NTSB Notification Source FAA Operations Center
NTSB Notification Date May 12 2003 12:00AM
NTSB Notification Time 1800
Fiche Number and/or location -used to find docket information DMS
Date of most recent change to record Sep 13 2005 12:54PM
User who most recently changed record NTSB\JOHB
Basic weather conditions Visual Meteorological Cond
FAA District Office Baton Rouge, Louisiana

Aircraft Involved

Aircraft #1

Aircraft Registration Number N491PH
NTSB Number FTW03FA148
Missing Aircraft Indicator --
Federal Aviation Reg. Part Part 135: Air Taxi & Commuter
Type of Flight Plan filed Company VFR
Flight plan Was Activated? Yes
Damage Substantial
Aircraft Fire None
Aircraft Explosion None
Aircraft Manufacturer's Full Name Bell
Aircraft Model 407
Aircraft Series Identifier --
Aircraft Serial Number 53386
Certified Max Gross Weight 5259
Aircraft Category Helicopter
Aircraft Registration Class --
Aircraft is a homebuilt? No
Flight Crew Seats --
Cabin Crew Seats --
Passenger Seats --
Total number of seats on the aircraft 6
Number of Engines 1
Fixed gear or retractable gear Fixed
Aircraft, Type of Last Inspection AAIP
Date of Last Inspection May 1 2003 12:00AM
Airframe hours since last inspection 24
Airframe Hours 5230
ELT Installed Yes
ELT Activated Yes
ELT Aided Location of Event Site No
ELT Type --
Aircraft Owner Name Petroleum Helicopters Inc.
Aircraft Owner Street Address PO Box 90808
Aircraft Owner City Lafayette
Aircraft Owner State LA
Aircraft Owner Country USA
Aircraft Owner Zipcode 70509
Operator is an individual? No
Operator Name --
Operator Same as Owner? Yes
Operator Is Doing Business As --
Operator Address Same as Owner? Yes
Operator Street Address --
Operator City --
Operator State --
Operator Country --
Operator Zip code --
Operator Code --
Owner has at least one certificate --
Other Operator of large aircraft? --
Certified for Part 133 or 137 Operation --
Operator Certificate Number --
Indicates whether an air carrier operation was scheduled or not Non-scheduled
Indicates Domestic or International Flight Domestic
Operator carrying Pax/Cargo/Mail Passenger Only
Type of Flying (Per_Bus / Primary) --
Second Pilot on Board No
Departure Point Same as Event No
Departure Airport Code --
Departure City EI 380, GOM
Departure State GM
Departure Country USA
Departure Time 1453
Departure Time Zone CDT
Destination Same as Local Flt --
Destination Airport Code 9LA7
Destination City Morgan City
Destination State LA
Destination Country USA
Specific Phase of Flight Cruise
Report sent to ICAO? Yes
Evacuation occurred Yes
Date of most recent change to record May 19 2005 4:07PM
User who most recently changed record CASH
Since inspection or accident Time of Accident
Event Location Runway Number and Location NA
Runway Length --
Runway Width --
Sight Seeing flight No
Air Medical Flight No
Medical Flight --