ASN Wikibase Occurrence # 173237
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| Date: | Friday 23 January 2015 |
| Time: | 16:30 LT |
| Type: | Bell UH-1Y Venom |
| Owner/operator: | 3rd MAW USMC |
| Registration: | 168402 |
| MSN: | |
| Year of manufacture: | 2011 |
| Fatalities: | Fatalities: 2 / Occupants: 2 |
| Aircraft damage: | Destroyed |
| Location: | Marine Corps Air Ground Combat Center, Twentynine Palms, CA -
 United States of America
|
| Phase: | Landing |
| Nature: | Military |
| Departure airport: | Miramar Naval Air Station (KNKX) |
| Miramar Naval Air Station (KNKX) | |
| Confidence Rating: |  Information is only available from news, social media or unofficial sources |
The helicopter, a Bell UH-1Y Venom (aka Super Huey), crashed during a training exercise. Both crew members died in the crash.
At the heart of the tragedy was an improperly installed filter cover, which allowed the transmission to dump all its oil during flight. Ultimately, investigators found that the aircraft plummeted 200 feet, just 400 yards away from the Marines' intended landing point.
About 34 minutes into the 49-minute flight, the pilots noticed that their oil pressure gauge fluctuated and then plummeted to zero.
While the warning lights typically indicate an emergency, the pilots likely assumed the problem was due to a faulty gauge, not actual fluid loss, because of recent maintenance issues. About a week prior, their aircraft had undergone maintenance because of a faulty reading, which included replacing oil pressure sensors.
With Twentynine Palms more than 15 minutes away, the pilots decided to continue flying. They passed two airports where they could have landed safely before the transmission froze, the investigators found.
According to Navy aviation publications, zero oil pressure should trigger pilots to execute “impending [main rotor gear box] failure procedures,” under the assumption that the aircraft will soon become inoperable. That means landing as soon as possible.
“Loss of MRGB oil pressure will render the helicopter unflyable within 15 minutes,” the aircraft’s Naval Air Training and Operating Procedures Standardization manual states.
A new MGB filter cover improperly installed three days before leaked or came off in flight.
The root cause of the trouble with the filter was a maintenance error made long before the accident. The filter housing must be uninstalled to change the filter. But at some point, an unapproved epoxy was used to seal the filter body, preventing Marines from removing it.
As a result, three waivers were issued over months to forgo a filter change. It was deemed unlikely that the filter was dirty, an assumption supported by the post-crash investigation, meaning the filter itself was not a contributing factor.
However, during one failed attempt to change the filter while it was still installed in the aircraft, the cover was damaged. That required that a new one be installed on Jan. 20. Three Marines worked to accomplish the task, which was later inspected and approved by a superior.
But because the filter housing was contained in a small space, they did not realize that a retaining ring that holds the cover on was not seated properly. That ultimately led to massive fluid loss during flight.
The investigator recommended changes to the filter housing maintenance that caused the leak. Those include:
Ensuring proper supervision of flightline maintainers removing the 40-micron filter housing.
Update naval air publications with detailed instructions for removal, disassembly, inspection, reassembly and installation of the filter housing.
Ensure all members of the UH-1 helicopter community learn pertinent information from the accident and begin training with it pending publication updates.
Prohibit the installation of the filter cover without removing the entire filter housing.
Sources:
http://www.utsandiego.com/news/2015/jan/23/helicopter-crash-military-miramar-twentynine-palms/
https://www.marinecorpstimes.com/news/pentagon-congress/2015/01/24/2-marines-die-in-california-helicopter-crash/
https://www.cnn.com/2015/01/24/us/california-marine-helicopter-crash/
http://fox5sandiego.com/2015/01/24/2-marines-killed-in-twentynine-palms-helicopter-crash/
https://www.3rdmaw.marines.mil/
https://www.marinecorpstimes.com/news/your-marine-corps/2015/10/25/investigation-faulty-filter-cover-pilot-error-caused-fatal-marine-helicopter-crash/
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 24-Jan-2015 09:03 | gerard57 | Added |
| 24-Jan-2015 18:06 | Geno | Updated [Location, Departure airport, Destination airport, Source] |
| 25-Jan-2015 04:24 | Geno | Updated [Aircraft type, Source, Narrative] |
| 26-Oct-2015 08:24 | Aerossurance | Updated [Time, Operator, Departure airport, Destination airport, Source, Damage, Narrative] |
| 26-Oct-2015 08:36 | Aerossurance | Updated [Registration] |
| 28-Dec-2019 17:44 | stehlik49 | Updated [Operator, Operator] |
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