Sikorsky S-70A incident near Pacoima, California, August 30, 2004
On August 30, 2004 at about 7:40 pm local time, a Sikorsky S-70A (helicopter), registered N160LA, suffered minor damage in an incident near Pacoima, California (Whiteman airport). It was a public-use flight under general aviation rules (Part 91). No one was hurt; 3 people were on board or involved. The weather was visual conditions (good weather).
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The NTSB's probable cause their words, unchanged
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.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- August 30, 2004 · about 7:40 pm local time
- Place
- Pacoima, California · Whiteman · map
- Type
- Incident
- Injuries
- No one was hurt; 3 people were on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Sikorsky S-70A · all S-70As on the register
- Registration
- N160LA · registry record · serial 702453
- Damage
- Minor damage
- Flight
- Public-use flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
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.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: airline transport pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 12,600 hours in all; 201 in this make and model; 75 in the last 90 days; 20 in the last 30 days; 12,000 as pilot in command
- Last flight review: March 1, 2004
- Medical certificate: Class 2 (with waivers/limitations)
- Seat: rgt
- Injury: no injuries
The aircraft
- Airframe total time: 1,493 hours
- Last inspection: continuous airworthiness programme, July 1, 2003; 89 hours since
- Maximum gross weight: 22,000 lb
- Landing gear: fixed
- Engine 1: General Electric T700-701C (turboshaft); 0 hours total
- Engine 2: General Electric T700-701C (turboshaft); 0 hours total
The flight
- Departed from: NA Pacoima CA at 7:35 pm
- Destination: PMD Palmdale CA
Weather at the time
- Light: daylight
- Wind: from 210° at 2 knots
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 90°F (32°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 3 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Other NTSB records under N160LA the same tail number, which may have belonged to a different aircraft at the time
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number LAX04IA311.