# NTSB CEN14LA486: Cirrus Design SR22, N22WX, Langola Township, MN, September 7, 2014 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 7, 2014, 13:36 local (18:36 UTC) - Place: Langola Township, MN - Coordinates: 45.801666, -94.134445 - Nearby events: https://openairdocs.org/map.md?lat=45.8017&lon=-94.1344&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 4 uninjured - Status: Completed, report March 14, 2016 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Continental Motors Inc, FAA, Cirrus Aircraft - NTSB case key (mKey): 90039 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN14LA486 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90039/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90039 - Page: https://openairdocs.org/ntsb/CEN14LA486 ## Probable cause Maintenance personnel’s failure to apply sufficient torque on the throttle control lever nut, which resulted in a loss of throttle control and subsequent loss of engine power. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine fuel and control: fuel controlling system](https://openairdocs.org/ntsb-findings/01057320): Aircraft › Aircraft power plant · Incorrect service/maintenance (probable cause); cases with it: [Cirrus Design SR22, 3 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md?model=2130001), [All aircraft, 59 cases](https://openairdocs.org/ntsb-findings/01057320/cases.md) - [Engine (reciprocating)](https://openairdocs.org/ntsb-findings/01058500): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [Cirrus Design SR22, 6 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md?model=2130001), [All aircraft, 497 cases](https://openairdocs.org/ntsb-findings/01058500/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Cirrus Design SR22, 5 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=2130001), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/cases.md) - [Object/animal/substance: wire](https://openairdocs.org/ntsb-findings/03022032): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Cirrus Design SR22, 2 cases](https://openairdocs.org/ntsb-findings/03022032/cases.md?model=2130001), [All aircraft, 588 cases](https://openairdocs.org/ntsb-findings/03022032/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Prior to flight: Aircraft maintenance event](https://openairdocs.org/ntsb-events/040); cases with it: [Cirrus Design SR22, 9 cases](https://openairdocs.org/ntsb-events/040/sequence.md?model=2130001), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md) - [Enroute-cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340); cases with it: [Cirrus Design SR22, 10 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2130001), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) - [Enroute-cruise: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [Cirrus Design SR22, 50 cases](https://openairdocs.org/ntsb-events/341/sequence.md?model=2130001), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Emergency descent: Off-field or emergency landing](https://openairdocs.org/ntsb-events/440); cases with it: [Cirrus Design SR22, 31 cases](https://openairdocs.org/ntsb-events/440/sequence.md?model=2130001), [All aircraft, 3,365 cases](https://openairdocs.org/ntsb-events/440/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Cirrus Design SR22, 113 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=2130001), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The commercial pilot was conducting a cross-country personal flight. He reported that, during cruise flight, the airspeed began to decrease, and the engine began to lose power. The pilot attempted to restore engine power but was not successful. He then conducted a forced landing to a road. During the landing roll, the pilot maneuvered the airplane to miss an oncoming car, and the airplane subsequently struck a guy wire, which resulted in substantial damage to the left wing. A postaccident examination of the engine revealed that the throttle control lever nut was not torqued to factory specifications in accordance with an engine manufacturer service bulletin (SB). The knurl teeth of both the throttle control lever and shaft displayed signatures of machining with adhesive wear scars on the surfaces. In addition, the surface of the control lever that the nut was normally secured to displayed scoring wear scars. The surface signatures were consistent with the throttle control lever nut not having been properly torqued. A review of the engine logbook entries revealed that a rebuilt engine was installed on the airplane about 73.1 flight hours before the accident. The mechanics at the repair station who installed the engine, which would have included installing the throttle body and torqueing the throttle control lever nut, reported that they were knowledgeable of the manufacturer SB, and no discrepancies in their procedures were found. Even though the mechanics reported that they were familiar with the SB, it is likely that they did not apply sufficient torque on the throttle control lever nut during the installation of the engine. ## Factual narrative On September 7, 2014, at 1336 central daylight time, a Cirrus SR22 airplane, N22WX, conducted a forced landing near Langola Township, Minnesota. The commercial-rated pilot and three passengers were not injured. The airplane was substantially damaged. The airplane was registered to N22WX LLC and operated by a private individual under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. The flight originated from the Mankato Regional Airport, Mankato, Minnesota, at 1257 and was en route to the Breezy Point Airport, Breezy Point, Minnesota.According to the pilot, during cruise flight, about 4,500 feet mean sea level, the airplane's airspeed began to decay and the engine's exhaust gas temperatures began to decrease. The pilot attempted to restore power to the engine without success. About one minute later the engine stopped producing power. The pilot performed a forced landing to a rural road. During the landing roll the pilot maneuvered the airplane to miss an oncoming car and collided with a utility pole guy wire. Substantial damage was sustained to the airplane's left wing. A postaccident inspection of the airplane by an inspector from the Federal Aviation Administration (FAA) and representatives from Cirrus Aircraft and Continental Motors discovered that the throttle arm rotated freely on the engine's throttle body. The throttle body was removed from the airplane and a new factory throttle body was installed on the engine and a successful engine run was accomplished. The original throttle body was shipped to the National Transportation Safety Board laboratories for an examination. The throttle control lever exhibited free play relative to the shaft and nut when wiggled by hand. Using a manual torque wrench, the breakaway tightening torque was 21 inch-pounds force (in-lbf), the breakaway removal torque was 15 in-lbf, and the average running torque was 19 in-lbf. According to the Continental Motors' Critical Service Bulletin CSB08-0C, the nut is to be tightened between 100 in-lbf to 120 in-lbf. The nut and the throttle control lever were removed from the assembly. The crests of the throttle control lever's knurl teeth exhibited flat plateaus with adhesive wear scars on the surface of the plateaus. The side of the control lever that the nut is normally secured against displayed circumferential marks consistent with contact with the periphery of the nut flange on its surface. The crests of the throttle body valve shaft tapered knurl teeth exhibited flat plateaus with adhesive wear scars on the surface of the plateaus and accumulated wear debris along the teeth flanks. Both the throttle control arm and throttle shaft were constructed of stainless steel. The number of teeth, knurl pitch, and chamfer angle differed between the level and the shaft mating surfaces. According to representatives from Continental Motors, precise matching of the arm and shaft knurls is not crucial to proper operation. Instead, the knurls act as afriction surface and when the nut is torqued to factory specifications. For testing purposes, the company used mating surfaces that were as dissimilar as possible but still within tolerances, and found it would take significant force on the arm to compromise the set torque. A review of the FAA's Service Difficulty Report database did not find any similar circumstances to the accident airplane. A review of logbook entries found that the engine was a factory rebuilt IO-550-N7B. The rebuild was completed on March 20, 2014, and was installed on N22WX on April 10, 2014. The pilot reported that the engine had a history of problems when the engine was at idle. As a result, the engine's fuel pump was replaced on August 13, 2014, at an engine total time of 62.5 hours. The engine performed normally at idle, but two days prior to the accident it idled higher than normal. The accident occurred at an engine total time of 73.1 hours. An inspector from the FAA interviewed mechanics at the repair station that performed the installation of the throttle body. They were also knowledgeable of the manufacturer's instructions and no discrepancies in their procedures were found. ## Aircraft - Registration: [N22WX](https://openairdocs.org/aircraft/N22WX), registered now, S/N 0281, built 2002 (OpenAirDocs) - Reported make and model: CIRRUS DESIGN CORP SR22 - Registry model: [Cirrus Design SR22](https://openairdocs.org/model/cirrus-design-sr22) (registry code 2130001) (OpenAirDocs) - Registry engine: [Continental IO-550 series](https://openairdocs.org/engine/continental-io-550-series) (registry code 17042, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 0281 - Year built: 2002 - Airframe hours: 2276.2 - Engines: CONT MOTOR IO-550-N7B 310 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, April 10, 2014, 73 hours before - Departed: MKT, MANKATO, MN - Destination: 8MN3, BREEZY POINT, MN - Equipment: ADS-B, Stall warning system, Onboard weather, Airframe parachute, Electronic primary flight display, Electronic multifunction display, Auto-pilot, Angle of attack indicator ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 52; injuries: none; commercial, flight instructor; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review March 17, 2014; seat: left; restraint: 4-point; flight hours: 2,242 total, 1,390 in this make and model, 2,170 as pilot in command, 49 in the last 90 days, 21 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 170° at 13 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 79 °F, dew point 55 °F - Altimeter: 30.05 inHg - Observed at: KSTC, 16 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 20140907016049A](https://openairdocs.org/incident/20140907016049A), Sep 7, 2014: Cirrus Design Corp SR22, St. Cloud, MN, Substantial damage. Pilot reported engine loss of power while at cruise approximately 10 miles north of STC. Pilot landed aircraft on a road. Aircraft sustained substantial when… ## Docket (3 files) The files NTSB released with the investigation on January 28, 2016, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90039. 3.4 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 2.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40436164&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Materials Laboratory Factual Report (item 2, .PDF, 1.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40436165&FileExtension=.PDF&FileName=Materials%20Laboratory%20Factual%20Report-Master.PDF - Accident Flight Data (item 3, .PDF, 62 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40436167&FileExtension=.PDF&FileName=Accident%20Flight%20Data-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. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.