Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Milwaukee, Wisconsin
Sonex Aircraft LLC; Oshkosh, Wisconsin
Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf
Investigation Docket - National Transportation Safety Board:https://dms.ntsb.gov/pubdms
Sonex Ltd: http://registry.faa.gov/N12YX
Location: Fond du Lac, WI
Accident Number: CEN16LA302
Date & Time: 08/03/2016, 1155 CDT
Registration: N12YX
Aircraft: SONEX LIMITED WAIEX
Aircraft Damage: Substantial
Defining Event: Powerplant sys/comp malf/fail
Injuries: 2 Serious
Flight Conducted Under: Part 91: General Aviation - Instructional
Analysis
Shortly after takeoff on an instructional flight, the pilots heard a sudden change in engine noise. The instructor scanned the engine instruments and observed that the engine rpm was lower than expected. The instructor took control of the airplane and attempted to return to the airport. The airplane was not able to maintain altitude, and the instructor could not restore engine power to full. Unable to reach the airport, the instructor initiated a forced landing to a field. During the approach, the airplane collided with a power transmission line and impacted terrain. An examination of the engine found that the Nos. 1 and 2 exhaust valves displayed excessive wear. While such wear will result in a loss of engine power, it could not be determined what caused the sudden change in noise and engine power that the pilots experienced on the day of the accident.
Probable Cause and Findings
The National Transportation Safety Board determines the probable cause(s) of this accident to be:
A partial loss of engine for reasons that could not be determined during an examination of the engine.
Findings
Environmental issues
Wire - Contributed to outcome
Not determined
Not determined - Unknown/Not determined (Cause)
Factual Information
On August 3, 2016, about 1155 central daylight time, a Sonex Limited Waiex airplane, N12YX, impacted terrain following a partial loss of engine power near the Fond du Lac County Airport (FLD), Fond du Lac, Wisconsin. The private rated pilot and flight instructor were both seriously injured. The airplane was substantially damaged. The airplane was registered to and operated by Sonex Ltd under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the light, which operated without a flight plan. The airplane was departing FLD at the time of the accident.
According to information provided by the flight instructor, the pilots were performing takeoffs and landing on runway 27 at FLD. Shortly after takeoff, when the airplane was between 200 to 300 ft above ground level, they heard a sudden change in the engine noise. The instructor observed that the engine rpm was between 2,500 to 2,600 rpm, when the engine was previously performing about 3,100 rpm. The instructor took control of the airplane and began an immediate left turn for runway 15. The airplane would not maintain altitude, so he momentarily leaned the mixture which did not improve engine performance, so he returned the mixture to full rich, and performed a forced landing to a field. The airplane collided with an unseen transmission line and impacted terrain. A postaccident examination of the airplane revealed substantial damage to the fuselage and both wings.
An examination of the engine was conducted at Sonex under the auspices of the Federal Aviation Administration. A compression check of the engine found low compression of the number 1 and 2 cylinders. Examination of the exhaust valves found they displayed excessive wear.
Pilot Information
Certificate: Airline Transport; Commercial
Age: 73, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Glider; Helicopter
Restraint Used: 4-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): Airplane Multi-engine; Instrument Airplane
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 04/04/2016
Occupational Pilot:
Last Flight Review or Equivalent: 05/14/2016
Flight Time: 29114 hours (Total, all aircraft), 35 hours (Total, this make and model), 24019 hours (Pilot In Command, all aircraft), 92 hours (Last 90 days, all aircraft), 9 hours (Last 30 days, all aircraft)
Pilot Information
Certificate: Private
Age: 64, Male
Airplane Rating(s): Single-engine Land
Seat Occupied:
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed:
Medical Certification: Class 3 With Waivers/Limitations
Last FAA Medical Exam: 11/26/2014
Occupational Pilot:
Last Flight Review or Equivalent:
Flight Time:
Aircraft and Owner/Operator Information
Aircraft Manufacturer: SONEX LIMITED
Registration: N12YX
Model/Series: WAIEX NO SERIES
Aircraft Category:Airplane
Year of Manufacture: 2003
Amateur Built: No
Airworthiness Certificate: Experimental
Serial Number: 0001
Landing Gear Type: Tailwheel
Seats: 2
Date/Type of Last Inspection: 02/07/2016, 100 Hour
Certified Max Gross Wt.:
Time Since Last Inspection:
Engines: 1 Reciprocating
Airframe Total Time: 304.3 Hours as of last inspection
Engine Manufacturer: AMA/EXPR
ELT: Installed, not activated
Engine Model/Series: AeroVee
Registered Owner: SONEX LTD
Rated Power: 80 hp
Operator: SONEX LTD
Operating Certificate(s) Held: None
Meteorological Information and Flight Plan
Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KFLD, 807 ft msl
Observation Time: 1053 CDT
Distance from Accident Site: 0 Nautical Miles
Direction from Accident Site: 100°
Lowest Cloud Condition:
Temperature/Dew Point: 30°C / 22°C
Lowest Ceiling: Broken / 3100 ft agl
Visibility: 10 Miles
Wind Speed/Gusts, Direction: 4 knots, 270°
Visibility (RVR):
Altimeter Setting: 30.05 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: FOND DU LAC, WI (FLD)
Type of Flight Plan Filed: None
Destination: OSHKOSH, WI (OSH)
Type of Clearance: None
Departure Time:
Type of Airspace:
Airport Information
Airport: FOND DU LAC COUNTY (FLD)
Runway Surface Type: Asphalt
Airport Elevation: 808 ft
Runway Surface Condition: Dry
Runway Used: 27
IFR Approach: None
Runway Length/Width: 3602 ft / 75 ft
VFR Approach/Landing: None
Wreckage and Impact Information
Crew Injuries: 2 Serious
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 Serious
Latitude, Longitude: 43.770278, -88.501389 (est)
14 CFR Part 91: General Aviation
Accident occurred Wednesday, August 03, 2016 in Fond du Lac, WI
Aircraft: SONEX LIMITED WAIEX, registration: N12YX
Injuries: 2 Serious.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
On August 3, 2016, about 1155 central daylight time, a Sonex Limited Waiex airplane, N12YX, impacted terrain following a partial loss of engine power near the Fond du Lac County Airport (KFLD), Fond du Lac, Wisconsin. The private rated pilot and flight instructor were both seriously injured. The airplane was substantially damaged. The airplane was registered to and operated by Sonex Ltd under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan.
According to preliminary information obtained by investigators, the pilots were performing touch-and-go landings at KFLD. Shortly after takeoff, the pilots reported a loss of engine power. During the forced landing, the airplane collided with a transmission line and impacted terrain. An inspection of the airplane revealed substantial damage to the fuselage and both wings.
The airplane was retained for further examination.
The National Transportation Safety Board did not travel to the scene of this accident.
Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Milwaukee, Wisconsin
Sonex Aircraft LLC; Oshkosh, Wisconsin
Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf
Sonex Ltd: http://registry.faa.gov/N12YX
Location: Fond du Lac, WI
Accident Number: CEN16LA302
Date & Time: 08/03/2016, 1155 CDT
Registration: N12YX
Aircraft: SONEX LIMITED WAIEX
Aircraft Damage: Substantial
Defining Event: Powerplant sys/comp malf/fail
Injuries: 2 Serious
Flight Conducted Under: Part 91: General Aviation - Instructional
On August 3, 2016, about 1155 central daylight time, a Sonex Limited Waiex airplane, N12YX, impacted terrain following a partial loss of engine power near the Fond du Lac County Airport (FLD), Fond du Lac, Wisconsin. The private rated pilot and flight instructor were both seriously injured. The airplane was substantially damaged. The airplane was registered to and operated by Sonex Ltd under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the light, which operated without a flight plan. The airplane was departing FLD at the time of the accident.
According to information provided by the flight instructor, the pilots were performing takeoffs and landing on runway 27 at FLD. Shortly after takeoff, when the airplane was between 200 to 300 ft above ground level, they heard a sudden change in the engine noise. The instructor observed that the engine rpm was between 2,500 to 2,600 rpm, when the engine was previously performing about 3,100 rpm. The instructor took control of the airplane and began an immediate left turn for runway 15. The airplane would not maintain altitude, so he momentarily leaned the mixture which did not improve engine performance, so he returned the mixture to full rich, and performed a forced landing to a field. The airplane collided with an unseen transmission line and impacted terrain. A postaccident examination of the airplane revealed substantial damage to the fuselage and both wings.
An examination of the engine was conducted at Sonex under the auspices of the Federal Aviation Administration. A compression check of the engine found low compression of the number 1 and 2 cylinders. Examination of the exhaust valves found they displayed excessive wear.
Pilot Information
Certificate: Airline Transport; Commercial
Age: 73, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Glider; Helicopter
Restraint Used: 4-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): Airplane Multi-engine; Instrument Airplane
Toxicology Performed: No
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 04/04/2016
Occupational Pilot:
Last Flight Review or Equivalent: 05/14/2016
Flight Time: 29114 hours (Total, all aircraft), 35 hours (Total, this make and model), 24019 hours (Pilot In Command, all aircraft), 92 hours (Last 90 days, all aircraft), 9 hours (Last 30 days, all aircraft)
Pilot Information
Certificate: Private
Age: 64, Male
Airplane Rating(s): Single-engine Land
Seat Occupied:
Other Aircraft Rating(s): None
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed:
Medical Certification: Class 3 With Waivers/Limitations
Last FAA Medical Exam: 11/26/2014
Occupational Pilot:
Last Flight Review or Equivalent:
Flight Time:
Aircraft and Owner/Operator Information
Aircraft Manufacturer: SONEX LIMITED
Registration: N12YX
Model/Series: WAIEX NO SERIES
Aircraft Category:Airplane
Year of Manufacture: 2003
Amateur Built: No
Airworthiness Certificate: Experimental
Serial Number: 0001
Landing Gear Type: Tailwheel
Seats: 2
Date/Type of Last Inspection: 02/07/2016, 100 Hour
Certified Max Gross Wt.:
Time Since Last Inspection:
Engines: 1 Reciprocating
Airframe Total Time: 304.3 Hours as of last inspection
Engine Manufacturer: AMA/EXPR
ELT: Installed, not activated
Engine Model/Series: AeroVee
Registered Owner: SONEX LTD
Rated Power: 80 hp
Operator: SONEX LTD
Operating Certificate(s) Held: None
Meteorological Information and Flight Plan
Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KFLD, 807 ft msl
Observation Time: 1053 CDT
Distance from Accident Site: 0 Nautical Miles
Direction from Accident Site: 100°
Lowest Cloud Condition:
Temperature/Dew Point: 30°C / 22°C
Lowest Ceiling: Broken / 3100 ft agl
Visibility: 10 Miles
Wind Speed/Gusts, Direction: 4 knots, 270°
Visibility (RVR):
Altimeter Setting: 30.05 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: FOND DU LAC, WI (FLD)
Type of Flight Plan Filed: None
Destination: OSHKOSH, WI (OSH)
Type of Clearance: None
Departure Time:
Type of Airspace:
Airport Information
Airport: FOND DU LAC COUNTY (FLD)
Runway Surface Type: Asphalt
Airport Elevation: 808 ft
Runway Surface Condition: Dry
Runway Used: 27
IFR Approach: None
Runway Length/Width: 3602 ft / 75 ft
VFR Approach/Landing: None
Wreckage and Impact Information
Crew Injuries: 2 Serious
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 2 Serious
Latitude, Longitude: 43.770278, -88.501389 (est)
NTSB Identification: CEN16LA302
14 CFR Part 91: General Aviation
Accident occurred Wednesday, August 03, 2016 in Fond du Lac, WI
Aircraft: SONEX LIMITED WAIEX, registration: N12YX
Injuries: 2 Serious.
This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
On August 3, 2016, about 1155 central daylight time, a Sonex Limited Waiex airplane, N12YX, impacted terrain following a partial loss of engine power near the Fond du Lac County Airport (KFLD), Fond du Lac, Wisconsin. The private rated pilot and flight instructor were both seriously injured. The airplane was substantially damaged. The airplane was registered to and operated by Sonex Ltd under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan.
According to preliminary information obtained by investigators, the pilots were performing touch-and-go landings at KFLD. Shortly after takeoff, the pilots reported a loss of engine power. During the forced landing, the airplane collided with a transmission line and impacted terrain. An inspection of the airplane revealed substantial damage to the fuselage and both wings.
The airplane was retained for further examination.
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