Saturday, June 08, 2019

Loss of Engine Power (partial): Yakovlev Yak-52, N132MD, accident occurred April 29, 2017 near Porterville Municipal Airport (KPTV), Tulare County, California

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entity:

Federal Aviation Administration / Flight Standards District Office; Fresno, California

Aviation Accident Final Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board: 

Aviation Accident Data Summary - National Transportation Safety Board:

Location: Porterville, CA
Accident Number: WPR17LA094
Date & Time: 04/29/2017, 1015 PDT
Registration: N132MD
Aircraft: YAKOVLEV YAK 52
Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial)
Injuries: 1 Minor, 1 None
Flight Conducted Under: Part 91: General Aviation - Personal


The airline transport pilot reported that, during a formation flight, the engine started to run rough. Unable to maintain level flight, the pilot detached from the formation to troubleshoot the problem. The pilot noted that there were about 29 gallons of useable fuel onboard and all other indications were normal. The engine continued to lose power, and about 500 ft above the ground, the pilot elected to land in a vineyard. During landing, the airplane touched down, came to an abrupt stop, nosed over, and came to rest inverted.

Postaccident engine examination revealed small pieces of fabric in the fuel screen. In addition, some metal shavings and a small piece of metal were found in the fuel intake and carburetor inlet screen. The origins of the metal piece and shavings could not be determined. It is unlikely that the observed debris was enough to clog the fuel system; however, it is possible that there were other, non-observable pieces of debris in the fuel system that could have resulted in decreased fuel flow and the partial loss of engine power.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
A partial loss of engine power due to contaminants in the fuel system that decreased the fuel flow, the source of which could not be determined.


Fuel - Fluid condition (Cause)

Environmental issues
Debris/dirt/foreign object - Effect on equipment (Cause)

Factual Information

On April 29, 2017, about 1015 Pacific daylight time, a Yakovlev Yak 52 airplane, N132MD, experienced a total loss of engine power and was substantially damaged during the off airport forced landing in a field near Porterville, California. The airline transport pilot sustained minor injuries and the one passenger was uninjured. The airplane was registered to and operated by the pilot as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The local flight originated from Porterville Municipal airport (PTV) at 0935.

The pilot reported that the purpose of the flight was to practice a mass formation flight. As planned, the pilot separated from the mass group as a formation of four to land. Shortly after separating from the larger formation, the engine started to run rough and intermittent. Unable to maintain level flight, the pilot detached from the four-airplane formation. He noted that 29 gallons of usable fuel was remaining, he checked the magnetos, ignition switch, generator, battery, and all indications were normal. The engine continued to lose power, and about 500 ft above the ground, he elected to land in a vineyard. During landing, the airplane touched down, came to an abrupt stop, and nosed over coming to rest inverted.

During a postaccident examination of the airplane and engine by a mechanic and Federal Aviation Administration inspector, the spark plugs were removed and exhibited signatures consistent with normal wear and operation. The engine was rotated by hand and thumb compression was established in all cylinders. The oil screen was removed and was clear of debris. The fuel tanks were empty, and the fuel system was continuous throughout. The fuel screen exhibited some small pieces of unknown fabric. In addition, a small about of metal shavings from an unknown source and a small chunk of metal were found in the fuel intake and inlet screen.

The carburetor was removed and examined. The carburetor throttle plate moved from stop to stop. The fuel metering section was heavily damaged and fracture separated; the needle valve moved freely. There were no signs of corrosion throughout. The fuel inlet screen was clear of debris with the exception of small metal shavings and a small chunk of metal. The origin of the metal pieces was not determined.

History of Flight

Loss of engine power (partial) (Defining event)

Off-field or emergency landing
Nose over/nose down 

Pilot Information

Certificate: Airline Transport; Commercial
Age: 78, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Front
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present:No 
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 05/25/2016
Occupational Pilot: No
Last Flight Review or Equivalent: 04/17/2017
Flight Time:  26144 hours (Total, all aircraft), 712 hours (Total, this make and model), 18824 hours (Pilot In Command, all aircraft), 21 hours (Last 90 days, all aircraft), 9 hours (Last 30 days, all aircraft), 0 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: YAKOVLEV
Registration: N132MD
Model/Series: YAK 52
Aircraft Category: Airplane
Year of Manufacture: 1983
Amateur Built: No
Airworthiness Certificate: Experimental
Serial Number: 833802
Landing Gear Type: Retractable - Tricycle
Seats: 2
Date/Type of Last Inspection: 02/08/2017, Annual
Certified Max Gross Wt.: 2899 lbs
Time Since Last Inspection: 21 Hours
Engines: 1 Reciprocating
Airframe Total Time: 1734 Hours at time of accident
Engine Manufacturer: Vedeneyev
ELT: Installed, not activated
Engine Model/Series: M14P
Registered Owner: On file
Rated Power: 360 hp
Operator: On file
Operating Certificate(s) Held: None 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: PTV, 443 ft msl
Distance from Accident Site: 7 Nautical Miles
Observation Time: 0956 PDT
Direction from Accident Site: 134°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 7 knots /
Turbulence Type Forecast/Actual: / None
Wind Direction: 210°
Turbulence Severity Forecast/Actual: / N/A
Altimeter Setting: 30.11 inches Hg
Temperature/Dew Point: 19°C / 2°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Porterville, CA (PTV)
Type of Flight Plan Filed: None
Destination: Porterville, CA (PTV)
Type of Clearance: None
Departure Time: 0935 PDT
Type of Airspace:

Airport Information

Airport: Porterville Municipal Airport (PTV)
Runway Surface Type: N/A
Airport Elevation: 443 ft
Runway Surface Condition: Soft; Vegetation
Runway Used: N/A
IFR Approach: None
Runway Length/Width:
VFR Approach/Landing: Forced Landing

Wreckage and Impact Information

Crew Injuries: 1 Minor
Aircraft Damage: Substantial
Passenger Injuries: 1 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Minor, 1 None
Latitude, Longitude: 36.090833, -119.140278 (est)

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