Saturday, May 26, 2018

Cessna U206G Turbine Stationair, N891LL, registered to and operated by the State of Illinois: Accident occurred August 25, 2016 in Cave-In-Rock, Illinois



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

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Springfield, Illinois
Illinois Department of Transportation; Springfield, Illinois
Soloy Aviation Solutions; Olympia, Washington
Textron Aviation; Wichita, Kansas

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/N891LL




Location: Cave-In-Rock, IL
Accident Number: CEN16LA335
Date & Time: 08/25/2016, 1005 CDT
Registration: N891LL
Aircraft: CESSNA U206G
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries: 1 Serious, 1 Minor
Flight Conducted Under: Public Aircraft 

On August 25, 2016, about 1005 central daylight time, a Cessna U206G airplane, N891LL, was substantially damaged during a forced landing near Cave-In-Rock, Illinois. The pilot received minor injuries and the camera operator received serious injuries. The airplane was registered to and operated by the State of Illinois under the provisions of 14 Code of Federal Regulations Part 91 as a public use flight. Day visual meteorological conditions prevailed for the local flight, which departed without a flight plan from Abraham Lincoln Capital Airport (SPI), Springfield, Illinois at 0845.

Prior to departure for the aerial mapping flight, the pilot stated the fuel tanks were dipped to confirm a desired fuel load of 550 lbs (89 gallons). During the first 45 minutes of the flight, the fuel selector was in the "both" tanks position. After noticing a fuel imbalance, the pilot moved the fuel selector to the "right" tank position, where it remained for about the next 30 minutes.

While wings level at 3,500 ft above ground level (agl), the pilot and photographer noticed an abrupt loss of engine power. The pilot switched the fuel selector back to the "both" tanks position and was unsuccessful in restarting the engine three times. During the restart attempts and engine out descent, the pilot elected not to feather the propeller due to his concern of the time required to unfeather the propeller. Step No. 2 of the 'Engine Restart During Flight' checklist in the airplane's Pilot Operating Handbook directs the propeller control be placed to feather. With the propeller not feathered, the pilot stated the airplane descended at a high vertical speed.

The pilot executed a forced landing, during which the airplane impacted a grassy area at a high descent rate. Both wings and the engine firewall were damaged when the airplane hit a berm. Prior to egressing the airplane, the pilot turned the battery switch off and moved the fuel selector to the "off" position.

Examination at the accident site revealed the airplane was resting left wing low, with fuel leaking out of the left-wing tank vent. During recovery operations, 20 gallons of fuel were drained from the right wing and 5 gallons from the left wing. After removal from the accident site, the airplane was placed in the operator's hangar, where the investigative team performed a records review and examined the airframe and engine systems.

In 1988, a Soloy Turbine PAC engine was installed in accordance with supplemental type certificate (STC) SA2353NM. This powerplant conversion included an Allison 250-C20S free turboshaft engine and a Soloy reduction gearbox.

Examination of the engine revealed no evidence of engine fire, uncontained failure or malfunction. Minor impact damage was present on the outer combustion chamber, but the engine was otherwise undamaged. Both oil and fuel filters were equipped with bypass indicators. Neither filter indicated bypass.

The N2 rotor rotated smoothly by manually turning the power output shaft. Rotational continuity from the power turbine to the propeller was confirmed and the power turbine was not damaged. The N1 rotor rotated normally after energizing the starter-generator. The N1 spun up normally. Borescope inspection of turbine blades revealed no evidence of thermal erosion, foreign object damage or abnormal combustion.

The fuel supply line was disconnected from the fuel spray nozzle, revealing a few drops of fuel in the line. The starter-generator was engaged to check for fuel flow to the fuel spray nozzle; no fuel flowed. The fuel line to the fuel-flow transducer was disconnected and the starter-generator was engaged, with no fuel flow.

The fuel line to the check valve assembly was disconnected and the starter-generator was engaged. After a brief purge of air, fuel flowed freely from the fuel supply line. The disconnected fuel lines were reconnected, the fuel spray nozzle was connected to the fuel supply line, and the starter-generator was engaged again. After air was purged from the fuel pump, fuel flowed freely to the fuel nozzle, which produced a normal spray pattern.

The purpose of the check valve assembly is to prevent a buildup of raw fuel in the combustion case if the burner drain valve remains in the open position when the engine is not operating, which could result in a hot start. The check valve also prevents fuel nozzle drip at shutdown, reducing the risk of a fire. Based on the design, an engine restart is not possible when air from the fuel system has reached the check valve, and there is no procedure to clear the air while in-flight.

A vacuum test was performed on the engine fuel system. The fuel line at the fuel selector switch was capped off, and 8 pounds per square in vacuum (PSIV) was applied to the drain port of the engine-mounted fuel pump. The system held the vacuum for two minutes.

The wing fuel vent systems were examined by applying compressed air through each wing fuel vent line, with no blockages observed. Both wing fuel vent valves operated normally, with no restrictions. Both wing float switches were electrically tested, with no anomalies. The respective wing fuel low level lights illuminated when each wing fuel float valve reached about 2 inches from the bottom of the respective fuel tank. A vacuum test was performed from the engine pump filter bowl to the fuel valve, with no defects noted.

Compressed air was applied to test for air leaks in the wing fuel feed tubes/lines, from the wing to each fuel reservoir. No anomalies were noted. The fuel selector valve was removed from the airplane and the bottom plate was removed to expose the plate with the ports. The valve was selected to each position (OFF, LEFT, RIGHT, BOTH), with no anomalies noted.

After completion of the examination, the engine was shipped to the Rolls-Royce engine testing facility, where an engine functional test run was conducted. The engine started normally. Since a propeller was not available to prevent an overspeed, the engine was only accelerated past ground idle enough to demonstrate normal acceleration capability. The fuel pump was dissembled and there was no evidence of cavitation or other malfunction.

The Shadin Fuel Flow Indicator was removed from the airplane and shipped to the National Transportation Safety Board Vehicle Recorder Division. The unit displayed engine fuel flow, fuel used, and fuel remaining. The unit did not interface with airplane's fuel quantity indicating system and required the crew to enter the initial fuel onboard. All calculations and data provided by the unit were based on fuel flow. Between power cycles, the indicator retained the last fuel used and fuel remaining. After power up, the unit indicated fuel remaining was 325 lbs. and fuel used was 225 lbs. 



Pilot Information

Certificate: Airline Transport
Age: 69, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Left
Other Aircraft Rating(s): Helicopter
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): Airplane Multi-engine; Airplane Single-engine
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 02/10/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: 10/09/2015
Flight Time:   8357 hours (Total, all aircraft), 268 hours (Total, this make and model), 7135 hours (Pilot In Command, all aircraft), 43 hours (Last 90 days, all aircraft), 25 hours (Last 30 days, all aircraft), 2 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: CESSNA
Registration: N891LL
Model/Series: U206G
Aircraft Category: Airplane
Year of Manufacture: 1986
Amateur Built: No
Airworthiness Certificate: Experimental
Serial Number: U206-06937
Landing Gear Type: Tricycle
Seats: 2
Date/Type of Last Inspection: 02/04/2016, Annual
Certified Max Gross Wt.: 3600 lbs
Time Since Last Inspection:
Engines: 1 Turbo Prop
Airframe Total Time: 6170 Hours at time of accident
Engine Manufacturer: Allison
ELT: C126 installed, activated, aided in locating accident
Engine Model/Series: 250C20S
Registered Owner: STATE OF ILLINOIS
Rated Power: 420 hp
Operator: STATE OF ILLINOIS
Operating Certificate(s) Held: None

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KHSB, 396 ft msl
Observation Time: 1015 CDT
Distance from Accident Site: 26 Nautical Miles
Direction from Accident Site: 322°
Lowest Cloud Condition: Clear
Temperature/Dew Point: 29°C / 25°C
Lowest Ceiling: None
Visibility:  10 Miles
Wind Speed/Gusts, Direction: 6 knots, 240°
Visibility (RVR):
Altimeter Setting: 30.1 inches Hg
Visibility (RVV):
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: SPRINGFIELD, IL (SPI)
Type of Flight Plan Filed: None
Destination: SPRINGFIELD, IL (SPI)
Type of Clearance: None
Departure Time: 0845 CDT
Type of Airspace:  Class G 

Wreckage and Impact Information

Crew Injuries: 1 Serious, 1 Minor
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Serious, 1 Minor
Latitude, Longitude:  37.477500, -88.214444










NTSB Identification: CEN16LA335
14 CFR Public Use
Accident occurred Thursday, August 25, 2016 in Cave-In-Rock, IL
Aircraft: CESSNA U206G, registration: N891LL
Injuries: 1 Serious, 1 Minor.

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 25, 2016, about 1005 central daylight time, a Cessna U206G airplane, N891LL, was substantially damaged during a forced landing near Cave-In-Rock, Illinois. The pilot received minor injuries and the camera operator received serious injuries. The airplane was registered to and operated by the State of Illinois under the provisions of 14 Code of Federal Regulations Part 91 as a public use flight. Day visual meteorological conditions prevailed for the local flight, which departed without a flight plan from Abraham Lincoln Capital Airport (SPI), Springfield, Illinois at 0845. 

While conducting an aerial mapping flight, the pilot stated the turbine engine lost total power. The pilot attempted to restart the engine, but was not successful and executed a forced landing, which substantially damaged both wings and the engine firewall. The airplane was retained for further examination.

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