Individually Owned: 150,657
Corporate Owned: 137,281
Whiteman Airport
Aircraft Accident/Incident Report
Pacoima, California 91331
Monday, August 30, 2004 12:40 PDT
NTSB Narrative Summary Released at Completion of Accident
The twin-engine helicopter's number 2 engine experienced an uncontained engine failure and liberated debris punctured the helicopter's firewall while in cruise flight. The pilot made an uneventful landing at a nearby airport. Examination of the engine revealed segments of the stage 2 aft cooling plate (S2ACP) exited the power turbine case. Further investigation determined that the gas generator rotor's forward curvic seal was not installed during the operator's replacement of the gas generator turbine (GGT) module 92 hours prior to the event. Manufacturer's analysis of the missing curvic seal revealed it would have caused the reversal of the secondary airflow in the B-sump, which eventually led to auto ignition of the B-sump oil and exposure of the B-sump hardware to elevated temperatures. The elevated temperatures resulted in the separation of several B-sump components, including the separation of the compressor shaft. The compressor shaft separation resulted in the GGT rotor to rub into the stator and extensive secondary damage, including the separation of the S2ACP. The GGT module was replaced 209 hours prior to the event. According to the manufacturer, the forward curvic seal is part of the engine assembly rather than part of either the GGT rotor assembly or the high pressure compressor rotor assembly. According to General Electric (GE), if the curvic seal was removed from the engine during removal of the previous GGT rotor-stator assembly, and either discarded, or returned to GE's service facility with the rotor, a new seal would not have been included with the new GGT rotor-stator assembly, and the GGT could have been reinstalled without it. The manufacturer also reported that the maintenance manuals did not call for the verification of curvic seal installation during GGT replacement. This military engine was not a Federal Aviation Administration (FAA) certificated engine, but did share similar design features of other FAA certificated engines. The manufacturer reported that the civilian certificated engine maintenance manuals do call for the verification of curvic seal installation following a GGT replacement. The engine was removed from the event helicopter 92 hours prior to the event and was shipped to an engine service center for an internal leak at the number 3 labyrinth seal (located in the front frame of the engine). The service center repaired the inlet guide vanes, which, according to the manufacturer, was a typical repair when oil is observed leaking in the flow path in front of the compressor. However, their analysis of the missing curvic seal indicates that it too would have resulted in an oil leak in the front frame.
NTSB Probable Cause Narrative
the failure of the operator's mechanics to install the turboshaft engine's forward curvic seal during a gas generator turbine (GGT) replacement. Contributing factors to the incident were the failure of the manufacturer to provide a forward curvic seal with the replacement GGT, and the lack of a curvic seal installation verification inspection in the maintenance manuals following the GGT installation.
Event Information
| Type of Event | Incident |
| Event Date | 8/30/2004 |
| Event Day of the Week | Monday |
| Time of Event | 1240 |
| Event Time Zone | Pacific Daylight Time |
| Event City | Pacoima |
| Event State | CALIFORNIA |
| Event Country | -- |
| Zipcode of the event site | 91331 |
| Event Date Year | 2004 |
| Event Date Month | 8 |
| MidAir Collision Indicator | No |
| On Ground Collision occurred ? | No |
| Event Location Latitude | 341535N |
| Event Location Longitude | 1182449W |
| Event Location Airport | Whiteman |
| Event Location Nearest Airport ID | WHP |
| 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 | Pilot |
| 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 | -- |
| Sky/Lowest/Cloud Conditions | Clear |
| Sky Condition for Lowest Ceiling | None |
| Visibility Runway Visual Range (Feet) | -- |
| Visibility Runway Visual Value (Statute Miles) | -- |
| Visibility (Statute Miles) | 10 |
| Air Temperature at event time (in degrees celsius) | 32 |
| Dew Point at event time (in degress fahrenheit) | -- |
| Wind Direction (degrees magnetic) | 210 |
| Variable Wind Indicator | Wind direction could be determined |
| Wind Speed (knots) | 2 |
| Wind Velocity Indicator | -- |
| Wind Gust Indicator | Not Gusting |
| Wind Gust (knots) | -- |
| Altimeter Setting at event time (in. Hg) | -- |
| 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 | 3 |
| Injury Total Serious | -- |
| Injury Total All | -- |
| Investigating Agency | NTSB |
| NTSB Docket Number (internal use) | 19900 |
| NTSB Notification Source | FAA |
| NTSB Notification Date | Sep 1 2004 12:00AM |
| NTSB Notification Time | 1330 |
| Fiche Number and/or location -used to find docket information | DMS |
| Date of most recent change to record | Jun 28 2006 1:30PM |
| User who most recently changed record | NTSB\JOHB |
| Basic weather conditions | Visual Meteorological Cond |
| FAA District Office | Federal Aviation Administration Van Nuys FSDO |
Aircraft Involved |
|
|---|---|
Aircraft #1 |
|
| Aircraft Registration Number | N160LA |
| NTSB Number | LAX04IA311 |
| Missing Aircraft Indicator | -- |
| Federal Aviation Reg. Part | Part 91: General Aviation |
| Type of Flight Plan filed | Company VFR |
| Flight plan Was Activated? | Yes |
| Damage | Minor |
| Aircraft Fire | None |
| Aircraft Explosion | None |
| Aircraft Manufacturer's Full Name | Sikorsky |
| Aircraft Model | S-70A |
| Aircraft Series Identifier | -- |
| Aircraft Serial Number | 702453 |
| Certified Max Gross Weight | 22000 |
| 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 | -- |
| Number of Engines | 2 |
| Fixed gear or retractable gear | Fixed |
| Aircraft, Type of Last Inspection | Continuous Airworthiness |
| Date of Last Inspection | Jul 1 2003 12:00AM |
| Airframe hours since last inspection | 89 |
| Airframe Hours | 1493 |
| ELT Installed | Yes |
| ELT Activated | No |
| ELT Aided Location of Event Site | No |
| ELT Type | -- |
| Aircraft Owner Name | County of Los Angeles Fire Department |
| Aircraft Owner Street Address | 12605 Osborne Street |
| Aircraft Owner City | Pacoima |
| Aircraft Owner State | CA |
| Aircraft Owner Country | -- |
| Aircraft Owner Zipcode | 91331 |
| 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 | None |
| 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 | -- |
| Indicates Domestic or International Flight | -- |
| Operator carrying Pax/Cargo/Mail | -- |
| Type of Flying (Per_Bus / Primary) | Public Use |
| Second Pilot on Board | No |
| Departure Point Same as Event | No |
| Departure Airport Code | NA |
| Departure City | Pacoima |
| Departure State | CA |
| Departure Country | USA |
| Departure Time | 1235 |
| Departure Time Zone | PDT |
| Destination Same as Local Flt | -- |
| Destination Airport Code | PMD |
| Destination City | Palmdale |
| Destination State | CA |
| Destination Country | USA |
| Specific Phase of Flight | Cruise - normal |
| Report sent to ICAO? | Yes |
| Evacuation occurred | No |
| Date of most recent change to record | Jun 22 2006 11:07AM |
| User who most recently changed record | JOHB |
| 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 | -- |