Investigation Docket - National Transportation Safety Board:
Location: Sidney, Nebraska
Accident Number: CEN19LA215
Date & Time: July 9, 2019, 08:13 Local
Registration: N62069
Aircraft: Beech 65
Aircraft Damage: Substantial
Defining Event: Explosion (non-impact)
Injuries: 1 None
Flight Conducted Under: Part 91: General aviation - Positioning
Analysis
The pilot had topped off the outboard fuel tanks before departure. While taxiing for takeoff, the stall warning horn activated, and the pilot pulled the circuit breaker to disable the horn. During the takeoff roll, the pilot heard a loud bang, observed significant damage to the outboard left wing, and aborted the takeoff. While taxiing back to the ramp, the pilot noted smoke coming from the top of the left wing. The pilot taxied the airplane to the corner of the ramp, performed an abbreviated shutdown, grabbed a fire extinguisher, and evacuated. The pilot did not observe any additional smoke or fire and did not discharge the fire extinguisher.
Examination of the airplane revealed fire and thermal damage near the wing root area, including melted and burned wiring. Due to some loose installation screws, a fuel leak was found coming from the fuel sending unit, which had recently been replaced. In addition, a wiring harness was found pinched between a metal clamp and a wing rib. Metal-to-metal contact was noted between exposed wiring and
the wing rib. Based on the fuel leak in the left wing and the pinched wiring, it is likely fuel vapors ignited and caused an explosion of the outboard left wing.
A few months before the accident, the outboard left wing was replaced. The operator's director of maintenance stated that the electrical wiring in the wing was not inspected during the wing replacement.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The improper maintenance of the outboard left wing, which allowed electrical arcing and leaking of the fuel sending unit and subsequently resulted in ignition of fuel vapors and an explosion of the outboard left wing.
Findings
Personnel issues Installation - Maintenance personnel
Personnel issues Post maintenance inspection - Maintenance personnel
Aircraft Electrical pwr sys wiring - Damaged/degraded
Aircraft Fuel quantity sensor - Incorrect service/maintenance
Factual Information
On July 9, 2019, about 0813 mountain daylight time, a Beech 65 airplane, N62069, experienced a left wing explosion during takeoff roll from the Sidney Municipal Airport (SNY), Sidney, Nebraska. The airline transport pilot was not injured, and the airplane sustained substantial damage to the left wing. The airplane was registered to and operated by Bemidji Aviation Services, Inc., as a Title 14 Code of Federal Regulations Part 91 positioning flight. Day instrument meteorological conditions prevailed at the time of
the accident, and an instrument flight rules flight plan was filed. The flight was originating from SNY, and destined for Denver, Colorado.
According to the operator, the pilot had topped off the outboard fuel tanks prior to departure, and the airplane contained about 230 gallons. While taxiing and advancing the engine throttles, the stall warning horn sounded so he pulled the circuit breaker as a corrective action which stopped the stall warning horn. The pilot thought the stall warning horn was in error and no further action was taken before the takeoff. During the takeoff roll, the pilot heard a loud bang and observed significant damage to the outboard left wing. Initially he thought maybe the airplane struck an animal, or the airplane impacted a pothole on the runway. While taxiing back to the ramp, the pilot noted a small amount of smoke coming from the top of the left wing. The pilot taxied the airplane to the corner of the ramp, performed an abbreviated shutdown of the airplane, grabbed a fire extinguisher, and evacuated. The pilot did not
observe any additional smoke or fire and did not discharge the fire extinguisher.
Postaccident examination of the airplane by a Federal Aviation Administration inspector and personnel from the operator revealed fire and thermal damage near the wing root area to include melted and burned wiring. After the accident as a precaution, the airplane was defueled by the operator, and in order to determine if a fuel leak was present, fuel was added to the outboard left wing during the examination. After fueling with 15 to 25 gallons of fuel, fuel began leaking from the top of the left wing fuel sending unit. Safety wire on the fuel sending unit screws was removed, and the fuel sending unit screws were found loose. The screws were tightened and fuel stop leaking from the sending unit. A hole was cut in the wing skin to examine the melted and burned wiring. A wiring harness was found pinched between a metal clamp and a wing rib. The clamp was removed and metal to metal contact was noted between exposed wiring and the wing rib. Due to the thermal damage, the wiring harness could not be separated to determine if the stall warning system could be functionally tested.
On February 22, 2019, the airplane was involved in an accident that required the replacement of the outboard left wing. According to the operator's director of maintenance, the electrical wiring in the wing was not inspected during the wing replacement. In addition, during recent maintenance at an unknown time, the inboard left fuel sending unit was replaced. The most recent continuous airworthiness inspection was completed on June 26, 2019.
History of Flight
Takeoff Explosion (non-impact) (Defining event)
Takeoff Aircraft structural failure
Pilot Information
Certificate: Airline transport; Commercial; Flight instructor
Age: 45, Male
Airplane Rating(s): Single-engine land; Multi-engine land
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): Airplane single-engine; Instrument airplane
Toxicology Performed: No
Medical Certification: Class 1 Without waivers/limitations
Last FAA Medical Exam:
Occupational Pilot: Yes
Last Flight Review or Equivalent: May 16, 2019
Flight Time: 7155 hours (Total, all aircraft), 2500 hours (Total, this make and model), 6301 hours (Pilot In Command, all aircraft), 150 hours (Last 90 days, all aircraft), 50 hours (Last 30 days, all aircraft), 3 hours (Last 24 hours, all aircraft)
Aircraft and Owner/Operator Information
Aircraft Make: Beech
Registration: N62069
Model/Series: 65
Aircraft Category: Airplane
Year of Manufacture:
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 62-3866
Landing Gear Type: Retractable - Tricycle
Seats: 2
Date/Type of Last Inspection: June 26, 2019 Continuous airworthiness
Certified Max Gross Wt.: 8000 lbs
Time Since Last Inspection: Engines: 2 Reciprocating
Airframe Total Time: 8933 Hrs as of last inspection
Engine Manufacturer: Lycoming
ELT: C126 installed, not activated
Engine Model/Series: IO-720-A1B
Registered Owner:
Rated Power: 400 Horsepower
Operator:
Operating Certificate(s) Held: None
Operator Does Business As:
Operator Designator Code: BEMA
Meteorological Information and Flight Plan
Conditions at Accident Site: Visual (VMC)
Condition of Light: Day
Observation Facility, Elevation: 4313 ft msl
Distance from Accident Site: 0 Nautical Miles
Observation Time: 07:53 Local
Direction from Accident Site: 0°
Lowest Cloud Condition: Clear
Visibility: 10 miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 7 knots /
Turbulence Type Forecast/Actual: None /
Wind Direction: 300°
Turbulence Severity Forecast/Actual: /
Altimeter Setting: 30.04 inches Hg
Temperature/Dew Point: 18°C / 12°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Sidney, NE (KSNY)
Type of Flight Plan Filed: IFR
Destination: Denver, CO (DEN)
Type of Clearance: IFR
Departure Time: 08:13 Local
Type of Airspace: Class E
Airport Information
Airport: Sidney Municipal KSNY
Runway Surface Type: Asphalt
Airport Elevation: 4313 ft msl
Runway Surface Condition: Dry
Runway Used: 31
IFR Approach: None
Runway Length/Width: 6600 ft / 100 ft
VFR Approach/Landing: None
Wreckage and Impact Information
Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries:
Aircraft Fire: On-ground
Ground Injuries: N/A
Aircraft Explosion: On-ground
Total Injuries: 1 None
Latitude, Longitude: 41.101387,-102.985275(est)
The National Transportation Safety Board did not travel to the scene of this accident.
Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Wichita, Kansas
