Tuesday, October 01, 2019

Loss of Engine Power (Partial): Cessna 206H Stationair, N247F; accident occurred September 19, 2018 near Sugar Land Regional Airport (KSGR), Fort Bend County, Texas

View to the east along Voss Road. Struck vehicles are also visible.

N247F in the median on Voss Road.

Severed empennage.

The nose of the airplane and spilled hydraulic fluid.

The spark plugs after removal from the engine. Note the damage to plugs 1 and 2.

Damage to cylinder 1.

Damage to piston 1. Note embedded valve fragment.

Damage to pistons 2 and 3. Note embedded valve fragments.

Damage to pistons 4 and 5. Note embedded valve fragments.

Damage to piston 6. Note embedded valve fragment.

Bent no. 1 valve stem tip caused by piston and combustion chamber contact, and most probably contributed to no. 1 intake valve failure. 

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

Additional Participating Entities:
United States Drug Enforcement Administration; Fort Worth, Texas
Lycoming Engines; Arlington, Texas
Textron Aviation (Cessna Aircraft); Wichita, Kansas
Federal Aviation Administration / Flight Standards District Office; Houston, Texas
National Transportation Safety Board; Arlington, Texas

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

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


Location: Sugar Land, TX
Accident Number: CEN18LA382
Date & Time: 09/19/2018, 1504 CDT
Registration: N247F
Aircraft: Cessna 206
Aircraft Damage: Substantial
Defining Event: Loss of engine power (total)
Injuries: 1 Minor, 2 None
Flight Conducted Under: Public Aircraft 

***This report was modified on 12/11/2019. Please see the docket for this accident to view the original report.*** 

On September 19, 2018 at 1504 central daylight time, a Cessna 206H airplane, N247F, struck power lines and terrain after the engine lost power while on landing approach to Sugar Land Municipal Airport/Hull Field (SGR), Sugar Land, Texas. There were no injuries to the two pilots aboard. The observer sustained minor injuries. The airplane was registered to Silver Creek Aviation Services and was being operated as a 14 Code of Federal Regulations Part 91 by an entity of the United States Government, both of Fort Worth, Texas, as a public use instructional flight. Visual meteorological conditions prevailed at the accident site, and no flight plan had been filed. The local flight originated from Conroe-North Houston Regional Airport (CXO), Houston, Texas.

Information obtained from the operator indicated that the commercial-rated pilot, under the oversight of a flight instructor, had flown in the Houston Class B airspace for an hour, and was flying the area navigation (RNAV) global positioning system (GPS) instrument approach to runway 17 at SGR. After crossing CASOB, the final approach fix, and before arriving at the missed approach point (MAP), the engine lost power. The instructor took control and maneuvered the airplane over a set of power lines. He was attempting to maneuver under a second set of power lines when the right wing struck one of the lines. The airplane touched down on a roadway, but its left wing struck a passing vehicle. The landing gear then struck the concrete median, yawing the airplane clockwise, and the tail struck a second vehicle. According to the operator, the airplane had about 30 to 32 gallons of fuel in each fuel tank.

The airplane was transported to a secure facility in Alliance, Texas, where a cursory examination was made. The engine, a six-cylinder Lycoming IO-540, was installed new on February 2, 2005. Maintenance information revealed the engine had been overhauled between November 4, 2013, and March 17, 2014. At that time, the engine had accrued 1,983.9 hours. During the overhaul, all 12 hydraulic lifters were replaced. The intake and exhaust rocker arms were reworked and reused.

The engine was rotated manually by rotating the propeller. The propeller moved about 200-degree arc before coming to a stop. The engine was removed from the airframe and disassembled. Borescope examination revealed the no. 1 cylinder intake valve had failed. All the cylinders and pistons were removed. Fractured pieces of the intake valve had been drawn into the intake plenum. The no. 1 cylinder was extensively damaged by fractured intake valve pieces as was the no. 1 piston head. The other piston heads either had impact marks or pieces of valve embedded in their heads. No metal was found in the oil pump, but there were signs of blow-by on the piston skirts. Damage was noted to sparkplugs 1 and 2.

The no. 1 cylinder, no. 1 piston, its intake and exhaust valve train components (springs, pushrods, rocker arms) and 12 hydraulic lifters were sent to Lycoming Engines for metallurgical examination. According to their Materials Laboratory Investigation Report, the no. 1 intake valve had failed in fatigue that initiated from the key recess fillet radius surface, and the fatigue crack radiated across approximately 2/5 of the cross section. Both the intake and exhaust rocker arms had nonconforming gauge shoe heights after about 0.01" material had been removed from the shoe pads during their re-work at overhaul. Except for the nos. 2 and 5 intakes and the no. 1 exhaust, the 9 hydraulic lifters failed the leak-down test, including the no. 1 intake. All other intake valve train components (valve springs, valve keys, spring seats, rotator cap) were undamaged.

The no. 1 intake valve failed in fatigue, but the root cause of the fatigue failure not be determined with any degree of certainty. The intake lifter and shoe height (valve stem tip) most likely contributed to the failure. The tip had separated from stem at the keeper fillet radius. The stem was bent, and head was fractured into several pieces. Damage to the bent stem and fractured head seating was caused by post-fracture contacts with the piston and combustion chamber. The fracture surface of intake valve tip was severely smeared by secondary impact and imbedded with some bronze from the intake valve guide.

The propeller assembly was examined at McCauley Propellers in Wichita, Kansas, under FAA oversight. According to McCauley's Teardown Inspection Report, both blades sustained impact damage and bore indications consistent with "a low amount of rotational energy absorption." No indications of propeller failure or malfunction were found. The propeller governor (Model: DC290D1F-T37, P/N: D-20893-37, S/N: 090066) was sent to Textron Aviation-McCauley Propeller Systems in Wichita, Kansas. The governor was externally examined and functionally tested to manufacturing requirements.

The observer's seatbelt was found released despite her tightening it prior to impact. The seatbelt was sent to AMSAFE for evaluation. According to AMSAFE'S report, the system housing may have taken some crushing damage which created drag on the push button assembly, allowing a partial connection to be made with the pawl. This would only occur "when attempting to lightly engage the connector into the buckle assembly." The report concluded that the connector engaged 100% each time it was tested. "Abrasion was shown in the inner half of the top and side buckle covers as well as along the push button," indicating that the unit "may have been smashed or restricted at some point."

A fuel sample from the left wing was sent to Aviation Laboratories in Kenner, Louisiana, for testing. Their report indicated a slightly elevated water content, but" sample test results appear normal."

Pilot Information

Certificate: Airline Transport; Flight Instructor; Commercial; Private
Age: 42, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land
Seat Occupied: Right
Other Aircraft Rating(s): Helicopter
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): Airplane Multi-engine; Airplane Single-engine
Toxicology Performed: No
Medical Certification: Class 1 Without Waivers/Limitations
Last FAA Medical Exam: 05/01/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent: 05/18/2018
Flight Time:   4919 hours (Total, all aircraft), 1044 hours (Total, this make and model), 4638 hours (Pilot In Command, all aircraft), 124 hours (Last 90 days, all aircraft), 46 hours (Last 30 days, all aircraft), 5 hours (Last 24 hours, all aircraft)

Pilot Information

Certificate: Commercial; Private
Age: 33, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Left
Other Aircraft Rating(s): None
Restraint Used: 3-point
Instrument Rating(s): Airplane
Second Pilot Present: Yes
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 1 With Waivers/Limitations
Last FAA Medical Exam: 09/08/2017
Occupational Pilot: No
Last Flight Review or Equivalent: 08/16/2018
Flight Time:  328 hours (Total, all aircraft), 205 hours (Total, this make and model), 228 hours (Pilot In Command, all aircraft), 118 hours (Last 90 days, all aircraft), 34 hours (Last 30 days, all aircraft), 2 hours (Last 24 hours, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: Cessna
Registration: N247F
Model/Series: 206 H
Aircraft Category: Airplane
Year of Manufacture: 2005
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 20608247
Landing Gear Type: Tricycle
Seats: 3
Date/Type of Last Inspection: 08/09/2018, Annual
Certified Max Gross Wt.: 3605 lbs
Time Since Last Inspection: 45 Hours
Engines: 1 Reciprocating
Airframe Total Time: 3636 Hours
Engine Manufacturer: Lycoming
ELT: Installed, activated, did not aid in locating accident
Engine Model/Series: IO-540-AC1A5
Registered Owner: Silver Creek Aviation Services
Rated Power: 300 hp
Operator: U.S. Drug Enforcement Administration
Operating Certificate(s) Held: None 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KSGR, 82 ft msl
Distance from Accident Site: 1 Nautical Miles
Observation Time: 1453 CDT
Direction from Accident Site: 170°
Lowest Cloud Condition: Few / 4700 ft agl
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 3 knots /
Turbulence Type Forecast/Actual: None / None
Wind Direction: 210°
Turbulence Severity Forecast/Actual: N/A / N/A
Altimeter Setting: 29.92 inches Hg
Temperature/Dew Point: 34°C / 23°C
Precipitation and Obscuration:
Departure Point: Conroe, TX (KCXO)
Type of Flight Plan Filed: None
Destination: Conroe, TX (KCXO)
Type of Clearance: IFR; VFR
Departure Time: 1400 CDT
Type of Airspace: Class D

Airport Information

Airport: Sugar Land Regional (SGR)
Runway Surface Type: Concrete
Airport Elevation: 82 ft
Runway Surface Condition: Dry
Runway Used: 17
IFR Approach: Global Positioning System; Practice; RNAV; Visual
Runway Length/Width: 8000 ft / 100 ft
VFR Approach/Landing: Forced Landing

Wreckage and Impact Information

Crew Injuries: 2 None
Aircraft Damage: Substantial
Passenger Injuries: 1 Minor
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Minor, 2 None
Latitude, Longitude: 29.644444, -95.656111