Saturday, February 08, 2020

Loss of Engine Power (Total): Beech V35 Bonanza, N6257V; accident occurred July 08, 2017 near Jones Farm Field Airport (OK12), Walters, Cotton County, Oklahoma

Airplane at Accident Site.

Hole Adjacent to Number 4 Cylinder.

Removed Engine Prior to Examination.

Vacuum Pump Gasket as Discovered.
(Red Arrow Indicates Exposed Oil Orifice).

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

Additional Participating Entities:

Federal Aviation Administration / Flight Standards District Office; Oklahoma City, Oklahoma
Continental Engines; Mobile, Alabama

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location: Walters, OK
Accident Number: CEN17LA286
Date & Time: 07/08/2017, 1050 CDT
Registration: N6257V
Aircraft: BEECH V35
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries: 2 Minor
Flight Conducted Under: Part 91: General Aviation - Personal 

On July 8, 2017, about 1050 central daylight time, a Beech V35 airplane sustained substantial damage during a forced landing after a loss of engine power near Walters, Oklahoma. The airline transport pilot and one passenger sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed. The airplane was registered to Gas Corporation of America of Wichita Falls, Texas, and the flight was being operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The flight originated at 1040 from Kickapoo Downtown Airport (CWC), Wichita, Falls, Texas, and was en route to Lawton, Oklahoma.

The pilot reported that about 10 minutes after departing CWC, the oil pressure went to zero and the engine failed. He executed a forced landing to a soft farm field, about one mile south of the Walters Airport (OK12). The pilot and passenger exited the airplane with minor injuries. The airplane sustained substantial damage to the firewall and lower fuselage.

A review of the airplane maintenance records showed that the vacuum pump was replaced on July 7, 2017, the day before the accident. The engine was visually examined and disassembled. During the disassembly, it was discovered that a improper gasket (P/N-21051) was installed on the vacuum pump. The gasket was normally used for the installation of a carburetor. The installed gasket did not completely cover the high-pressure oil orifice on the vacuum pump mounting fixture. The proper gasket was (PN-MS9134-01) for the vacuum pump. Three connecting rods showed thermal and impact damage, and three rod journals were observed to be dry and showed thermal discoloration. 

Pilot Information

Certificate: Airline Transport
Age: 48, Male
Airplane Rating(s): Multi-engine Land; Single-engine Sea
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 1 Without Waivers/Limitations
Last FAA Medical Exam: 06/14/2016
Occupational Pilot: No
Last Flight Review or Equivalent:
Flight Time: (Estimated) 5000 hours (Total, all aircraft), 26 hours (Total, this make and model), 20 hours (Last 90 days, all aircraft), 1 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Make: BEECH
Registration: N6257V
Model/Series: V35 UNDESIGNATED
Aircraft Category: Airplane
Year of Manufacture: 1967
Amateur Built: No
Airworthiness Certificate:Normal 
Serial Number: D-8587
Landing Gear Type: Retractable - Tricycle
Seats: 6
Date/Type of Last Inspection: 02/07/2017, Annual
Certified Max Gross Wt.: 3400 lbs
Time Since Last Inspection: 10 Hours
Engines: Reciprocating
Airframe Total Time: 3432 Hours at time of accident
Engine Manufacturer: Continental
ELT: C91A installed, not activated
Engine Model/Series: IO-520-BB6
Registered Owner: On file
Rated Power: 300 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: LAW
Distance from Accident Site: 20 Nautical Miles
Observation Time: 1053 CDT
Direction from Accident Site: 180°
Lowest Cloud Condition:  Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 3 knots /
Turbulence Type Forecast/Actual:
Wind Direction: 130°
Turbulence Severity Forecast/Actual:
Altimeter Setting: 30.07 inches Hg
Temperature/Dew Point: 25°C / 22°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Wichita Falls, TX (CWC)
Type of Flight Plan Filed: None
Destination: Lawton, OK (LAW)
Type of Clearance: None
Departure Time: 1040 CDT
Type of Airspace: Class E

Airport Information

Airport: Jones Farm Field Airport (OK12)
Runway Surface Type:
Airport Elevation: 1042 ft
Runway Surface Condition: Dry
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 Minor
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 Minor
Latitude, Longitude: 34.399167, -98.266389 (est)


  1. Maybe have a little "talk" with the mechanic,reckon ?

  2. A come-to-Jesus meeting about getting the job done right the first time and aircraft safety.

  3. So many factors in this screw-up.
    1. Who supplied the gasket? Less than $3 retail for the MS9134-01 gasket, should come with a new or rebuilt pump. Did pump supplier send the wrong one? If not with pump, did mechanic rummage in a leftover parts pile?
    2. Did the new gasket get held up to match-check against the old gasket?
    3. Did the terminology "dry pump" bias the mechanic to not realize there is an oil supply passage on the accessory mount?
    4. Inside diameter of gasket is a fit to the raised "male" ring feature on the pump, incorrect gasket obviously not proper fit if checked to pump.
    5. As shown in NTSB photo, easy to see oil passageway not closed properly by gasket if placed on studs and looked at before pump installed.

    The pump supply/overhaul companies can help the customers avoid mechanic incompetence on this substitution by including a warning tag attached through the corner of the dry pump "Use only gasket MS9134-01 to prevent loss of oil from accessory mount and engine damage". Should not have to do that, but look at the total expense from this mistake, which could have been fatal if the terrain was not as accommodating.

    The mechanic should verify what P/N gasket to use, but in the modern "TL:DR" world of today, perhaps a wired warning tag on the pump is going to become your only hope.