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ASN Wikibase Occurrence # 174294
Last updated: 21 November 2018
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Date:05-MAR-2015
Time:14:22
Type:Silhouette image of generic PT22 model; specific model in this crash may look slightly different
Ryan ST-3KR Recruit
Owner/operator:Private
Registration: N53178
C/n / msn: 1859
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Substantial
Category:Accident
Location:West of Santa Monica Municipal Airport (KSMO), Santa Monica, CA -   United States of America
Phase: Take off
Nature:Private
Departure airport:Santa Monica, CA (SMO)
Destination airport:Santa Monica, CA (SMO)
Investigating agency: NTSB
Narrative:
Shortly after takeoff, the pilot advised the air traffic control tower controller that the engine had lost power, and the pilot requested an immediate return to the airport. The pilot initiated a left turn toward the airport; however, during the approach, he realized that the airplane was unable to reach the runway. Subsequently, the airplane struck the top of a tree and then impacted the ground in an open area of a golf course.

A postaccident examination of the airplane's engine revealed that the carburetor's main metering jet was unscrewed from its seat and rotated 90 degrees. The unseated jet would have allowed an increased fuel flow through the main metering orifice, producing an extremely rich fuel-to-air ratio, which would have resulted in the loss of engine power. It is likely that, over time, the jet gradually loosened from its seat, which allowed it to eventually rotate 90 degrees. No further mechanical failures or malfunctions were revealed that would have precluded normal operation.

A review of the airplane's maintenance records indicated that the carburetor was rebuilt during the airplane's restoration about 17 years before the accident. The carburetor maintenance instruction manual contained no pertinent instructions for the installation of the jet assemblies. Further, no maintenance entries in the engine logbook regarding carburetor maintenance were found. Had the carburetor maintenance instruction manual identified a means to ensure the security of the main metering jet, it is unlikely that the jet would have become unseated. There was no record of maintenance personnel inspecting the carburetor jets during the previous 17 years nor was there a requirement to do so.

The front and rear seats of the airplane were equipped with non-factory-installed shoulder harnesses. The pilot's shoulder harness was installed by mounting the end of the restraint to the lower portion of the seatback assembly, which was made of thin aluminum. No reinforcement material or doublers were installed at or around the attachment bolt hole in the seatback. The lack of reinforcement allowed the attachment bolt, washers, and stop nut to be pulled upward and through the seatback structure during the impact sequence, which resulted in the pilot's loss of shoulder harness restraint. It is likely that the improperly installed shoulder harness contributed to the severity of the pilot's injuries.

As a result of this investigation, the NTSB is working with the pilot community to inform them of the lessons learned from this accident: the security of the carburetor's main metering jet and the security of the shoulder harness are both critical aspects of aviation safety.
Probable Cause: A total loss of engine power during initial climb when the carburetor main metering jet became unseated, which led to an extremely rich fuel-to-air ratio. Contributing to the accident was the lack of adequate carburetor maintenance instructions. Contributing to the severity of the pilot's injuries was the improperly installed shoulder harness.

Sources:

NTSB: https://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20150305X93207&key=1
FAA register: http://registry.faa.gov/aircraftinquiry/NNum_Results.aspx?NNumbertxt=53178


Revision history:

Date/timeContributorUpdates
06-Mar-2015 02:08 Geno Added
06-Mar-2015 02:13 Geno Updated [Source, Narrative]
06-Mar-2015 03:14 Geno Updated [Aircraft type, Registration, Cn, Operator, Source, Narrative]
06-Mar-2015 05:01 harro Updated [Aircraft type]
06-Mar-2015 05:17 harro Updated [Embed code]
06-Mar-2015 08:21 gerard57 Updated [Date, Embed code]
07-Mar-2015 07:24 Anon. Updated [Narrative]
10-Mar-2015 23:36 Geno Updated [Source]
21-Dec-2016 19:28 ASN Update Bot Updated [Time, Damage, Category, Investigating agency]
01-Dec-2017 12:45 ASN Update Bot Updated [Operator, Other fatalities, Departure airport, Destination airport, Source, Embed code, Narrative]

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