# NTSB CEN18LA382: Cessna 206, N247F, Sugar Land, TX, September 19, 2018

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: September 19, 2018, 15:04 local (20:04 UTC)
- Place: Sugar Land, TX
- Coordinates: 29.644443, -95.656112
- Nearby events: https://openairdocs.org/map.md?lat=29.6444&lon=-95.6561&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Defining event: [Approach-VFR pattern final: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342)
- Highest injury: Minor injuries
- Injuries: 1 minor, 2 uninjured
- Status: Completed, report February 11, 2020
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: National Transportation Safety Board, U.S. Drug Enforcement Administration, Lycoming Engines, Textron Aviation (Cessna Aircraft)
- NTSB case key (mKey): 98324
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA382
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98324/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=98324
- Page: https://openairdocs.org/ntsb/CEN18LA382

## Probable cause

Fatigue failure of the No. 1 cylinder intake valve, which resulted in the loss of engine power.

## Findings

NTSB's coded findings; those marked are part of the probable cause.

- [Engine (reciprocating): recip engine power section](https://openairdocs.org/ntsb-findings/01058520): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-findings/01058520/cases.md?model=2073301), [All aircraft, 233 cases](https://openairdocs.org/ntsb-findings/01058520/cases.md)
- [Engine (reciprocating): recip eng cyl section](https://openairdocs.org/ntsb-findings/01058530): Aircraft › Aircraft power plant · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-findings/01058530/cases.md?model=2073301), [All aircraft, 373 cases](https://openairdocs.org/ntsb-findings/01058530/cases.md)
- [Object/animal/substance: wind sock](https://openairdocs.org/ntsb-findings/03022030): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-findings/03022030/cases.md?model=2073301), [All aircraft, 12 cases](https://openairdocs.org/ntsb-findings/03022030/cases.md)
- [Object/animal/substance: ground vehicle](https://openairdocs.org/ntsb-findings/03022025): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-findings/03022025/cases.md?model=2073301), [All aircraft, 132 cases](https://openairdocs.org/ntsb-findings/03022025/cases.md)
- [Object/animal/substance: wall/barricade](https://openairdocs.org/ntsb-findings/03022027): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-findings/03022027/cases.md?model=2073301), [All aircraft, 29 cases](https://openairdocs.org/ntsb-findings/03022027/cases.md)

## Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event best describes what happened.

- [Approach-VFR pattern final: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Cessna 206H, 1 case](https://openairdocs.org/ntsb-events/342/sequence.md?model=2073301), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md)
- [Uncontrolled descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 206H, 3 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2073301), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)
- [After landing: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cessna 206H, 3 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2073301), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md)

## Analysis

The airline transport pilot and the flight instructor were conducting an instructional flight in a public aircraft with an observer on board and proceeded to an airport to conduct instrument approaches. After crossing the final approach fix and before arriving at the missed approach point, the engine lost power. The instructor took control and maneuvered the airplane over a set of power lines. He attempted 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, and its left wing struck a passing vehicle. The landing gear struck the concrete median, yawing the airplane clockwise, and the airplane's tail struck a second vehicle. Postaccident engine examination revealed the No. 1 cylinder intake valve had failed. Fractured pieces of the intake valve had been drawn into the intake plenum. The No. 1 cylinder was extensively damaged, and all of the piston heads had impact marks or pieces of valve embedded in the heads. The No. 1 cylinder, No. 1 piston, its intake and exhaust valve train components (springs, pushrods, and rocker arms), and 12 hydraulic lifters were sent to the engine manufacturer for metallurgical examination, which revealed that the No. 1 cylinder intake valve had failed in fatigue; however, the root cause of the failure could not be determined due to the extensive damage after the valve failure. Both the intake and exhaust rocker arms had nonconforming shoe heights. In addition, nine of the hydraulic lifters failed the leak-down test, including the No. 1 intake. Maintenance information revealed the engine had been overhauled 4 years earlier, during which all 12 hydraulic lifters were replaced. The intake and exhaust rocker arms had been reworked and reused, and about 0.01 inch of material had been removed from the shoe pads during the overhaul. While the nonconforming rocker arm shoe height and lifter may have contributed to a malfunction of the valve, the investigation could not determine with certainty the reason for the fatigue failure. The fatigue failure of the No. 1 cylinder intake valve resulted in the loss of engine power.

## Factual narrative

***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. According to the Lycoming report, the no. 1 intake valve failed in fatigue, but the root cause of the fatigue failure could not be determined with any degree of certainty. The intake lifter and nonconforming rocker arm may have contributed to a malfunction in the No. 1 intake valve train. The valve stem 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."

## Aircraft

- Registration: [N247F](https://openairdocs.org/aircraft/N247F), registered now, S/N 20608247, built 2005 (OpenAirDocs)
- Reported make and model: Cessna 206 (H)
- Registry model: [Cessna 206H](https://openairdocs.org/model/cessna-206h) (registry code 2073301) (OpenAirDocs)
- Registry engine: [Lycoming IO-540 series](https://openairdocs.org/engine/lycoming-io-540-series) (registry code 41530, reciprocating) (OpenAirDocs)
- Category: Airplane
- Serial number: 20608247
- Year built: 2005
- Airframe hours: 3636
- Engines: Lycoming IO-540-AC1A5 300 horsepower reciprocating
- Damage: Substantial damage
- Flight: Public aircraft - federal, Public use
- Operator: U.S. Drug Enforcement Administration
- Registered owner: Silver Creek Aviation Services
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, August 9, 2018, 45 hours before
- Departed: KCXO, Conroe, TX
- Destination: KCXO, Conroe, TX
- Airport: SGR, Sugar Land Regional, runway 17, 8,000 × 100 ft, concrete
- Equipment: Stall warning system

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; injuries: none; private, commercial, airline transport, flight instructor; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review May 18, 2018; seat: right; restraint: 3-point; flight hours: 4,919 total, 1,044 in this make and model, 4,638 as pilot in command, 124 in the last 90 days, 46 in the last 30 days, 5 in the last 24 hours
- Pilot; age 33; injuries: none; private, commercial; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review August 16, 2018; seat: left; restraint: 3-point; flight hours: 328 total, 205 in this make and model, 228 as pilot in command, 118 in the last 90 days, 34 in the last 30 days, 2 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 210° at 3 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 93 °F, dew point 73 °F
- Altimeter: 29.92 inHg
- Observed at: KSGR, 1 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 20180919013829A](https://openairdocs.org/incident/20180919013829A), Sep 19, 2018: Cessna 206H, Sugarland, TX, Destroyed. N247F was inbound on the RNAV 17 to Sugarland, Texas (sgr). The aircraft had leveled off at the minimum descent altitude (mda) of 640 feet when the engine…

## Docket (18 files)

The files NTSB released with the investigation on June 25, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=98324. 15.8 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1-2 (item 1, .PDF, 683 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473662&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-2-Master.PDF
- Flight Crew Interviews (item 2, .PDF, 175 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473663&FileExtension=.PDF&FileName=Flight%20Crew%20Interviews-Master.PDF
- NTSB Engine Examination Factual Report (item 3, .PDF, 12 photos, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473664&FileExtension=.PDF&FileName=NTSB%20Engine%20Examination%20Factual%20Report-Master.PDF
- Memorandum (item 4, .PDF, 84 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40477699&FileExtension=.PDF&FileName=Memorandum-Master.PDF
- Excerpts from Engine Logbook (item 5, .PDF, 248 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473665&FileExtension=.PDF&FileName=Excerpts%20from%20Engine%20Logbook-Master.PDF
- Lycoming Mandatory Service Bulletin 369Q, Engine Inspection after Overspeed (item 6, .PDF, 327 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473666&FileExtension=.PDF&FileName=Lycoming%20Mandatory%20Service%20Bulletin%20369Q,%20Engine%20Inspection%20after%20Overspeed-Master.PDF
- Textron Lycoming Service Instruction 1425A, Suggested Maintenance Procedures to Reduce the Possibility of Valve Sticking (item 7, .PDF, 314 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473667&FileExtension=.PDF&FileName=Textron%20Lycoming%20Service%20Instruction%201425A,%20Suggested%20Maintenance%20Procedures%20to%20Reduce%20the%20Possibility%20of%20Valve%20Sticking-Master.PDF
- McCauley Propeller Systems,Teardown Inspection Report 18-08 (item 8, .PDF, 174 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473668&FileExtension=.PDF&FileName=McCauley%20Propeller%20Systems,Teardown%20Inspection%20Report%2018-08-Master.PDF
- Propeller Overspeed Test (item 9, .PDF, 622 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473669&FileExtension=.PDF&FileName=Propeller%20Overspeed%20Test-Master.PDF
- AmSafe Failure Analysis and Corrective Action Report (item 10, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473670&FileExtension=.PDF&FileName=AmSafe%20Failure%20Analysis%20and%20Corrective%20Action%20Report-Master.PDF
- Fuel Testing and Examination (item 11, .PDF, 154 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473671&FileExtension=.PDF&FileName=Fuel%20Testing%20and%20Examination-Master.PDF
- Wreckage Diagram (item 12, .PDF, 1 photo, 4.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473672&FileExtension=.PDF&FileName=Wreckage%20Diagram-Master.PDF
- RNAV Approach Procedure (item 13, .PDF, 59 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473673&FileExtension=.PDF&FileName=RNAV%20Approach%20Procedure-Master.PDF
- RNAV (GPS) RWY 17 Approach Procedure (item 14, .PDF, 59 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473674&FileExtension=.PDF&FileName=RNAV%20(GPS)%20RWY%2017%20Approach%20Procedure-Master.PDF
- Partial Transcript of Radio Communications (item 15, .PDF, 322 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473675&FileExtension=.PDF&FileName=Partial%20Transcript%20of%20Radio%20Communications-Master.PDF
- Certification of Party Representatives to NTSB Investigation (item 16, .PDF, 239 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473676&FileExtension=.PDF&FileName=Certification%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Master.PDF
- Report Photos (item 17, .PDF, 11 photos, 3.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40473677&FileExtension=.PDF&FileName=Report%20Photos-Master.PDF
- Revised NTSB Factual Report (item 18, .PDF, 58 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40479229&FileExtension=.PDF&FileName=Revised%20NTSB%20Factual%20Report-Master.PDF

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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