Thursday, December 21, 2017

Flight Design CTLS, N527TS: Fatal accident occurred July 28, 2016 at Fond du Lac County Airport (KFLD), Wisconsin

Aviation Accident Final Report - National Transportation Safety Board: https://app.ntsb.gov/pdf 

Analysis

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. 

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
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.

Findings

Aircraft
Fuel - Fluid condition (Cause)
Fuel control/carburetor - Malfunction (Cause)
Performance/control parameters - Not attained/maintained (Factor)

Personnel issues
Aircraft control - Pilot (Factor)

Factual Information

History of Flight

Prior to flight
Fuel contamination (Defining event)

Initial climb
Powerplant sys/comp malf/fail
Loss of engine power (partial)

Emergency descent
Off-field or emergency landing

Post-impact
Part(s) separation from AC

The National Transportation Safety Board traveled to the scene of this accident.

Aviation Accident Factual Report - National Transportation Safety Board: https://app.ntsb.gov/pdf

Investigation Docket  - National Transportation Safety Board:  https://dms.ntsb.gov/pubdms

http://registry.faa.gov/527TS



Location: Fond du Lac, WI
Accident Number: CEN16FA290
Date & Time: 07/28/2016, 0821 CDT
Registration: N527TS
Aircraft: FLIGHT DESIGN GMBH CTLS
Aircraft Damage: Substantial
Defining Event: Fuel contamination
Injuries: 1 Fatal, 1 Serious
Flight Conducted Under: Part 91: General Aviation - Personal 

HISTORY OF FLIGHT

On July 28, 2016, about 0821 central daylight time, a Flight Design GMBH model CTLS airplane, N527TS, impacted terrain following a loss of engine power after takeoff. The pilot was fatally injured and the passenger was seriously injured. The airplane was substantially damaged. The airplane was registered to, and operated by a private individual as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the accident site about the time of the accident, and the flight was operated without a flight plan. The flight originated from Fond du Lac County Airport (FLD), Fond du Lac, Wisconsin at the time of the accident and its destination was not determined.

Witnesses reported seeing the airplane take off to the north and turn left, towards the airport, while still over airport property. They added that the engine sounded abnormal. 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 on the radio state he was making an immediate return to the airport.

Pilot

No pilot logbooks were located during the investigation and the pilot's time in the make and model of the accident airplane could not be determined. The pilot reported 110 total hours on his last application for medical certificate dated April 15, 2002. The pilot did not hold a current FAA medical certificate; however, he was operating the airplane under the Sport Pilot Medical rule.

Pilot-Rated Passenger

No pilot logbooks belonging to the pilot-rated passenger were located during the investigation. The pilot-rated passenger reported 2,136 total hours on his last application for medical certificate dated July 15, 1996.

AIRCRAFT DESCRIPTION

A review of the airplane's maintenance records revealed a 200 hr Carburetor Service Requirement per SI-912-021, Inspections of Carburetors, was complied with on December 9, 2014. According to the records the Hobbs meter read 829.5 hrs at the time of the inspection.



WRECKAGE DESCRIPTION

During impact, both wings separated from the fuselage and the engine intruded into the cockpit area. Flight control continuity to the elevator and rudder was verified continuous from the cockpit to each control surface. Flight control continuity was interrupted to both wings, but all observed breaks in continuity were consistent with overload failure during impact. A slight fuel smell was present at the accident scene. Both the left and right fuel tanks were compromised. Several ounces of liquid consistent with aviation fuel were recovered from the right-wing fuel tank, which appeared light blue in color and free of contaminants. The three composite propeller blades were broken and had separated near the propeller hub. The blade sections that were observed were absent chord wise scratches or leading-edge damage. The engine was removed from the wreckage and examined separately at a secure location.

MEDICAL AND PATHOLOGICAL INFORMATION

The pilot died on August 9, 2016. An autopsy was authorized and conducted on the pilot by the Fond du Lac County Medical Examiner's Office. The cause of death was attributed to multiple injuries sustained in an airplane accident. Forensic toxicology was not performed.

TESTS AND RESEARCH

Engine examination.

The engine was examined on August 17, 2016, in the presence of the NTSB Investigator in Charge. When examined, the engine remained attached to the engine mount.. The exhaust system was damaged and the muffler was not attached to the engine. No anomalies were noted of the ignition system. The fuel pump was removed and hand actuated. Liquid consistent in smell and color to aviation fuel was contained within the pump and squirted out when the pump was actuated. The oil cooler was detached and impact damaged. The engine was equipped with a non-approved aftermarket oil filter. The filter was cut open and inspected for ferrous material; no anomalies were noted. No anomalies were noted with the cylinders and cylinder heads. The engine was hand rotated; continuity was verified and no anomalies were noted. The radiator was impact damaged. The air filtration system was not available for examination.

The engine was equipped with two carburetors; one carburetor fed the number 1 and 3 cylinder, while the second carburetor fed the number 2 and 4 cylinders.

The 1/3-cylinder carburetor float bowl was removed. Flaking was noted on the floats and unidentified contamination, along with corrosion on the bottom of the float bowl. The main jet was clear of obstructions. No fuel was found within the carburetor.

The 2/4-cylinder carburetor float bowl was removed. Flaking was noted on the floats and contamination and corrosion on the bottom of the float bowl. The main jet was clear and no fuel was found within the carburetor. The piston slide was stuck on the carburetor chamber top. The piston was removed from the chamber top. An unknown substance was present that prevented the piston from sliding up and down within its respective bore. The piston slide was stuck in the idle position. Both carburetors were sent to the NTSB Materials Laboratory for further examination.

Carburetor examination.

The NTSB's laboratory removed the float bowls from each of the carburetors. Two black floats were present in each bowl, and all four floats moved freely on their respective posts. The floats were removed from the bowls and labeled by carburetor number and position relative to the side of the carburetor with the control lever. Next, each float was weighed and subsequently submerged for 12 hours in a covered container of automobile gasoline. After soaking, the floats were removed from the gasoline and then weighed again after the soak. Each float had a total weight gain of less than 1%. Additionally, the sum of the weights for the two floats from each carburetor was 5.668 grams and 5.674 grams for the 1/3 carburetor and the 2/4 carburetor, respectively. The maximum allowable combined weight for carburetor floats in each carburetor is 7 grams per the BRP-Powertrain Maintenance Manual for the Rotax 912-series engines.

The interior surfaces of the bowls had black areas along with areas of white film and other accumulations of white and yellow corrosion products. The black areas were mostly circular in shape and located on the lower surfaces of the bowls.

A white film was present in many areas, particularly on the lower surface and side of the bowl for carburetor 1/3. Isolated areas with thicker accumulations of white material was observed in some areas. When disturbed with tweezers, the accumulation had a powdery consistency, and the underlying surface of the bowl was black.

Some areas had an accumulation of yellow material. When disturbed with tweezers, the formation largely maintained its shape, but was easily broken into smaller crystalline chunks when pressure was applied. The surface under the yellow accumulation was also colored black.

Samples of the white and yellow accumulations were removed from the surface and placed onto carbon tape stuck to an aluminum stub to facilitate a compositional analysis using energy dispersive x-ray spectroscopy (EDS). Both samples had large peaks of zinc and oxygen consistent with oxides associated with the cast zinc bowl. Both samples also showed smaller peaks of sulfur and lead. The yellow sample and areas of the white sample also showed a peak of aluminum. Additionally, the yellow sample showed peaks of iron and potassium and a higher peak of carbon. Some areas of the yellow sample also showed a peak of silicon.

During the examination, the plunger from the 2/4 carburetor was reinserted into the 2/4 carburetor, and the springs and covers were put into place on their respective carburetors, and subsequently, the plungers were moved up and down. It was noted that the plunger from the 1/3 carburetor moved relatively easily while the plunger from the 2/4 carburetor had a tendency to stick. The plungers were removed from the carburetors with the housings and were manipulated again. The plunger from the 2/4 carburetor tended to stick compared to the plunger in the 1/3 carburetor.

The plungers were removed from the covers again, and accumulations of white material of varying thickness were present within the interior surface.

The surface of the plunger shaft housing on the 1/3 carburetor cover also had white material on the surface, but the material appeared to be more evenly distributed around the housing surface.

A sample of the white material from the plunger shaft housing from the 2/4 carburetor cover was removed and examined using EDS. The resulting spectrum showed high peaks of aluminum and oxygen, consistent with oxidation from the carburetor cover, which was made of an aluminum alloy.

ADDITIONAL INFORMATION

Rotax Aircraft Engines issued Service Instruction (SI)-912-021 on November 9, 2009. The following was extracted from that SI:

1.5) Compliance

- After engine installation/initial operation/return to service of an engine.

- When engine is running rough.

- And/or at the next scheduled maintenance event of carburetor (see Maintenance Manual for engine type 912/914 Series, current issue).

WARNING: Non-compliance with these instructions could result in engine damages, personal injuries or death.

3.1) General

Several carburetors have been found with contamination (dirt, remains of rubber from fuel lines and Loctite, resin-like substance, sediments etc.) in the float chamber.

WARNING: This contamination could possibly cause a partial or complete blockage of the idle or main jet or of other ducts vital for operation, leading to poor performance or stoppage of engine.

3.1.1) Possible shortcomings in the fuel system

- Dirt in the fuel system

- Missing or unsuitable fuel filter

- Clogged fuel filter

- Unsuitable fuel lines

- Dirt in fuel manifold

- Poor float chamber venting

- Insufficient flushing of the fuel system prior to initial engine operation

- Fuel pressure too low or too high

- Unsuitable fuel tanks and tank coatings

- Contaminated float chambers (e.g. corrosion caused by high water content in the fuel)

3.1.2) Fuel

Use only quality fuel as specified.

- EN 228 regular, EN 228 premium, EN 228 Super plus or AVGAS 100LL.

NOTE: The exact defined minimum requirements for fuel are specified in the relevant operators manual (for the relevant engine type) and the Service Instructions SI-912-016/SI-914-019 and SI-2ST-008 „Selection of suitable operating fluids", current issue.

The Rotax 912ULS engine maintenance manual specifies removal/assembly of both carburetors every 200 hours. 

Pilot Information

Certificate: Private
Age: 78, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): None
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Sport Pilot Unknown
Last FAA Medical Exam: 04/15/2002
Occupational Pilot: No
Last Flight Review or Equivalent:
Flight Time: 110 hours (Total, all aircraft), 0 hours (Total, this make and model) 

Pilot-Rated Passenger Information

Certificate: Flight Instructor; Commercial
Age: 71, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s):
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): Airplane Single-engine; Instrument Airplane
Toxicology Performed: No
Medical Certification: None None
Last FAA Medical Exam: 07/15/1996
Occupational Pilot: No
Last Flight Review or Equivalent: 
Flight Time: 2136 hours (Total, all aircraft), 0 hours (Total, this make and model) 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: FLIGHT DESIGN GMBH
Registration: N527TS
Model/Series: CTLS
Aircraft Category: Airplane
Year of Manufacture: 2008
Amateur Built: No
Airworthiness Certificate: Special Light-Sport
Serial Number: 08-02-04
Landing Gear Type: Tricycle
Seats: 2
Date/Type of Last Inspection: 01/24/2015, Annual
Certified Max Gross Wt.: 2950 lbs
Time Since Last Inspection: 135 Hours
Engines: 1 Reciprocating
Airframe Total Time: 960 Hours at time of accident
Engine Manufacturer: ROTAX
ELT: Installed, activated, did not aid in locating accident
Engine Model/Series: 912ULS
Registered Owner: On file
Rated Power: 100 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: KFLD, 807 ft msl
Observation Time: 1321 UTC
Distance from Accident Site: 1 Nautical Miles
Direction from Accident Site: 188°
Lowest Cloud Condition: Scattered / 1700 ft agl
Temperature/Dew Point: 19°C / 17°C
Lowest Ceiling: Broken / 5000 ft agl
Visibility:  10 Miles
Wind Speed/Gusts, Direction: 8 knots, 60°
Visibility (RVR):
Altimeter Setting: 29.97 inches Hg
Visibility (RVV):
Precipitation and Obscuration: Light - Rain
Departure Point: Fond du Lac, WI (FLD)
Type of Flight Plan Filed: None
Destination:
Type of Clearance: None
Departure Time: 0820 CDT
Type of Airspace: Class G

Airport Information

Airport: FOND DU LAC COUNTY (FLD)
Runway Surface Type: Asphalt
Airport Elevation: 808 ft
Runway Surface Condition: Unknown
Runway Used: 36
IFR Approach: None
Runway Length/Width: 5941 ft / 100 ft
VFR Approach/Landing: None 

Wreckage and Impact Information

Crew Injuries: 1 Fatal, 1 Serious
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Fatal, 1 Serious
Latitude, Longitude:  43.780000, -88.488889











NTSB Identification: CEN16FA290
14 CFR Part 91: General Aviation
Accident occurred Thursday, July 28, 2016 in Fond du Lac, WI
Aircraft: FLIGHT DESIGN GMBH CTLS, registration: N527TS
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 either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

On July 28, 2016, about 0821 central daylight time, a Flight Design GMBH model CTLS airplane, N527TS, impacted terrain while returning to land after initial takeoff. The pilot and single passenger were seriously injured. The airplane was substantially damaged. The airplane was registered to, and operated by a private individual as a 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed at the accident site about the time of the accident, and the flight was operated without a flight plan. The flight originated from Fond du Lac County Airport (FLD), Fond du Lac, Wisconsin at the time of the accident and its destination was not determined.

Witnesses reported seeing the airplane takeoff to the north and start a left turn back to the airport. They stated the engine sounded abnormal and 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 said they heard the pilot on the radio state he was making an immediate return to the airport.

During the impact both wings separated from the fuselage and the engine intruded into the cockpit area. Flight control continuity to the elevator and rudder was verified continuous from the cockpit to each control surface. Flight control continuity was interrupted to both wings, but all observed breaks in continuity were consistent with failure in overload during impact. Some fuel smell was present at the accident scene, but both the left and right fuel tanks were compromised. Several ounces of fuel were recovered from the right wing tank, which appeared light blue in color and free of contaminants. The three composite propeller blades were separated from the propeller hub. The blade sections that were observed were absent chord wise scratches or leading edge damage. The engine and wreckage were recovered to a secure storage location and retained for further examination.

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