Flight Design GMBH CTLS accident near Fond Du Lac, Wisconsin, July 28, 2016
On July 28, 2016 at about 1:21 pm local time, a 2008 Flight Design GMBH CTLS, registered N527TS, was substantially damaged in an accident during prior to flight near Fond Du Lac, Wisconsin (Fond Du Lac County airport). It was a personal flight under general aviation rules (Part 91). 1 person was killed and 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
Carburetor contamination following exposure to water in the fuel, which resulted in a carburetor malfunction and a partial loss of engine power. Contributing to the accident was the pilot's loss of airplane control that resulted in a stall.
Source: NTSB aviation accident database, copy made October 4, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- July 28, 2016 · about 1:21 pm local time
- Place
- Fond Du Lac, Wisconsin · Fond Du Lac County · map
- Type
- Accident
- Injuries
- 1 person was killed and 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Flight Design GMBH CTLS, built 2008 · all CTLSs on the register
- Registration
- N527TS · no longer on the register · serial 08-02-04
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The private pilot departed the airport in the light-sport airplane and made a left turn back toward the airport while still over airport property. The airplane was at a low altitude when it rolled to the left and impacted terrain, consistent with a loss of control following an aerodynamic stall. Witnesses stated that the engine sounded abnormal. One witness reported that the airplane did not climb above treetop height before it rolled into a steep left turn and descended into terrain. An additional witness did not see the accident occur but heard the pilot state on the radio that he was making an immediate return to the airport. The terrain in front of the pilot on departure was commercial properties and parking lots, and was unsuitable for landing. During postaccident examination, contaminants and corrosion were found in both carburetor bowls. The piston slide in the carburetor for the Nos. 2 and 4 cylinders was found stuck in the idle position in its bore on the carburetor chamber top. A white substance was present on the interior surface of the bore that prevented the piston from sliding up and down within the bore. Testing of the substance determined that it was likely contamination produced by oxidation and corrosion of the aluminum alloy carburetor chamber top because of exposure to water-contaminated fuel. The engine manufacturer had previously issued a Service Instruction (SI) that warned of the possibility of poor performance or engine stoppage due to contaminants in the carburetor float chamber. One of the sources of contaminants identified in the SI was corrosion caused by high water content in fuel. Both carburetors had been inspected in accordance with the SI about 130 flight hours and 19 months before the accident, which was within the SI recommended 200-hour inspection interval. The contaminants found in the carburetors were indicative of the use of fuel with high water content at an undetermined time, most likely after compliance with the SI.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
What happened, in order
- Fuel contamination during prior to flight defining event
- Powerplant sys/comp malf/fail during initial climb
- Loss of engine power (partial) during initial climb
- Off-field or emergency landing during emergency descent
- Part(s) separation from AC during post (impact)
The NTSB's findings
- cause Aircraft › Fluids/misc hardware › Fluids › Fuel › Fluid condition
- cause Aircraft › Aircraft power plant › Engine fuel and control › Fuel control/carburetor › Malfunction
- factor Aircraft › Aircraft oper/perf/capability › Performance/control parameters › (general) › Not attained/maintained
- factor Personnel issues › Task performance › Use of equip/info › Aircraft control › Pilot
Pilot
- Certificate: private
- Ratings: single-engine land
- Flight time: 110 hours in all; 0 in this make and model
- Medical certificate: Sport Pilot
- Seat: left
- Injury: fatal
Pilot-Rated Passenger
- Certificate: flight instructor, commercial pilot
- Ratings: multi-engine land; single-engine land; instructor: airplane single-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 2,136 hours in all; 0 in this make and model
- Medical certificate: None
- Seat: rgt
- Injury: serious injuries
The aircraft
- Airframe total time: 960 hours
- Last inspection: annual inspection, January 24, 2015; 135 hours since
- Maximum gross weight: 2,950 lb
- Seats: 2
- Landing gear: fixed
- Engine: Rotax 912ULS (piston); 960 hours total
The flight
- Departed from: FLD Fond Du Lac WI at 1:20 pm
- Flight plan: none
- Runway 36, 5,941 ft by 100 ft
- A second pilot was aboard
Weather at the time
- Light: daylight
- Wind: from 060° at 8 knots
- Visibility: 10 statute miles
- Sky: broken clouds at 5,000 ft; scat at 1,700 ft
- Temperature: 66°F (19°C), dew point 63°F (17°C)
- Altimeter: 29.96 inHg
- Observation at 1:21 pm from KFLD, 1 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight crew | 1 | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
About this page
Everything above comes from the NTSB's public accident database: the narrative, probable cause and findings are the NTSB's own words, and the coded tables behind its report (pilot, aircraft, flight, weather, injuries, sequence of events) are written out in plain English. Pilots' ages, home towns and medical details are left out on purpose. The documents and photographs are the NTSB's docket, the folder of records gathered during the investigation, shown as the NTSB released them (the NTSB redacts some personal details first) and listed under the NTSB's own titles. This site's own text never names pilots, passengers or anyone else involved. A preliminary report describes what is known soon after the event and can change; the final report, with the probable cause, usually follows one to two years later and this page is refreshed when it does. Case number CEN16FA290.