# NTSB CEN09IA578: Cessna 421, N2349S, Sugar Land, TX, September 4, 2009

- Type: NTSB incident investigation
- Classification: Incident · No injuries · Incident investigation · Final report
- Date: September 4, 2009, 17:55 local (22:55 UTC)
- Place: Sugar Land, TX
- Coordinates: 29.62, -95.653892 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=29.6200&lon=-95.6539&mi=10
- Phase of flight: [Other](https://openairdocs.org/ntsb-phases/800) (OpenAirDocs' grouping)
- Defining event: [Other: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330)
- Highest injury: No injuries
- Injuries: 1 uninjured
- Status: Completed, report October 3, 2011
- Report: Approved by Office Director
- NTSB office: Central Region
- Parties: FAA Houston FSDO, Cessna, Cobham
- NTSB case key (mKey): 74714
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN09IA578
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/74714/pdf
- NTSB docket: https://data.ntsb.gov/Docket?ProjectID=74714
- Page: https://openairdocs.org/ntsb/CEN09IA578

## Probable cause

The improper installation of the pitch trim cable which resulted in it making improper contact with a guard pin that led to the fatigue failure of the cable.

## Findings

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

- [Flight control system: elevator tab control system](https://openairdocs.org/ntsb-findings/01022731): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01022731/cases.md?model=2076016), [All aircraft, 37 cases](https://openairdocs.org/ntsb-findings/01022731/cases.md)
- [Action: incorrect action performance](https://openairdocs.org/ntsb-findings/02041015): Personnel issues › Action/decision · Maintenance personnel (probable cause); cases with it: [Cessna 421C, 4 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md?model=2076016), [All aircraft, 1,386 cases](https://openairdocs.org/ntsb-findings/02041015/cases.md)
- [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined; cases with it: [Cessna 421C, 8 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=2076016), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/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: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-events/040/sequence.md?model=2076016), [All aircraft, 484 cases](https://openairdocs.org/ntsb-events/040/sequence.md)
- [Other: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Cessna 421C, 4 cases](https://openairdocs.org/ntsb-events/330/sequence.md?model=2076016), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md)
- [Enroute-descent: Flight control sys malf/fail](https://openairdocs.org/ntsb-events/333); cases with it: [Cessna 421C, 2 cases](https://openairdocs.org/ntsb-events/333/sequence.md?model=2076016), [All aircraft, 410 cases](https://openairdocs.org/ntsb-events/333/sequence.md)

## Analysis

The airplane was on an autopilot descent when the pilot noticed the elevator pitch trim was rotating continuously in the nose-up position. He disconnected the autopilot and immediately heard a popping sound. The movement of the pitch trim stopped, and the pilot could manually turn the pitch trim wheel without force or resistance. He then hand flew the airplane using spoilers, 15 degrees of flaps and exerted approximately 10 to 20 pounds of back pressure on the yoke to keep the airplane in level flight. The pilot executed an emergency landing without further incident. A postincident examination of the airplane revealed that the pitch trim cable had fractured and separated in the area where it passed over the rearmost pulley in the tail. A subsequent materials laboratory examination revealed the pitch trim cable displayed evidence of permanent curved deformation near the fracture location, with localized smearing wear. Several of the fractured cable wires showed evidence of fatigue fracture and some showed the presence of cadmium. One of the cadmium plated pulley guard pins showed evidence of rubbing contact with the cable. The smearing wear and the presence of the cadmium on the cable wires is consistent with a misrouting of the cable over the cable guide pins instead of the proper routing over the cable pulley. Examination of partial aircraft maintenance records did not show entries for any maintenance events when the pitch trim cable was rerouted or reinstalled. The circumstances leading up to the improper misrouting of the pitch trim cables could not be determined.

## Factual narrative

On September 4, 2009, about 1755 central daylight time, a Cessna 421C, N2349S, experienced an in-flight separation of the elevator pitch trim cable during a descent for landing at Sugar Land Regional Airport (SGR), Sugar Land, Texas. The airplane was owned by TMC Aviation, Inc. and was being operated by the pilot on a 14 Code of Federal Regulations Part 91 business flight. Visual meteorological conditions prevailed and the pilot had filed and activated an instrument flight rules (IFR) flight plan. The airplane sustained minor damage. The pilot who was the only person on board was not injured. The flight originated from Santa Fe Municipal Airport (SAF), Santa Fe, New Mexico, about 1340 mountain daylight time. While the airplane was in an 800 feet per minute descent at about 180 to 190 knots the pilot noticed the elevator pitch trim was rotating continuously in the nose up position. He disconnected the autopilot and immediately heard a "popping sound". The movement of the pitch trim stopped, and the pilot could manually turn the pitch trim wheel without force or resistance. He then hand flew the airplane using spoilers, 15 degrees of flaps and exerted approximately 10 to 20 pounds of back pressure on the yoke to keep the airplane in level flight. The subsequent emergency landing at SGR was otherwise uneventful. Examination of the airplane revealed the elevator trim tab was fixed in approximately the neutral position and the pitch trim cable had fractured and separated in the area where it passes over the rearmost pulley in the tail. Cable pulleys in the area of the cable separation appeared to rotate freely on their respective bearings and did not display any significant flat spots within the cable groove. A subsequent materials laboratory examination was conducted of several components. The pitch trim cable displayed evidence of permanent curved deformation near the fracture location, with localized smearing wear and corresponding cracking of the cable wires at the approximate inner radius of the curvature. At the fracture location, some of the cable wire ends were locally curved, and splayed out. Some of the individual wires were bent "L" shape near the fracture with smearing wear and microcracking found on several wire surfaces. Several of the fractured cable wires showed evidence of fatigue fractures. Some of the worn surface areas on the cable wires near the fracture showed the presence of cadmium. One of the cadmium plated pulley guard pins showed evidence of rubbing contact with the cable. Aircraft maintenance records were available for examination for only the previous six years. Those recent records showed numerous times when the pitch trim cables were inspected and cable tension was checked. The records did not show entries for any maintenance events when the pitch trim cable was rerouted or reinstalled.

## Aircraft

- Registration: [N2349S](https://openairdocs.org/aircraft/N2349S), registered now, S/N 421C1209 (OpenAirDocs)
- Reported make and model: CESSNA 421 (C)
- Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs)
- Category: Airplane
- Serial number: 421C1209
- Airframe hours: 2570
- Engines: CONTINENTAL GTSIO520 375 horsepower reciprocating; CONTINENTAL GTSIO520 375 horsepower reciprocating
- Damage: Minor damage
- Flight: Business, Part 91
- Airworthiness certificate: Standard, Normal
- Last inspection: Annual, September 24, 2008, 48 hours before
- Departed: SAF, Santa Fe, NM
- Destination: SGR, Sugar Land, TX
- Flight plan: IFR
- Airport: SGR, Sugar Land Regional Airport, runway 17, 8,000 × 100 ft, concrete

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 60; injuries: none; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review March 7, 2009; seat: left; flight hours: 2,300 total, 800 in this make and model, 2,300 as pilot in command, 50 in the last 90 days, 25 in the last 30 days, 3 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: 150° at 10 knots
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 86 °F, dew point 68 °F
- Altimeter: 29.95 inHg
- Observed at: SGR

## Docket (13 files)

The files NTSB released with the investigation on July 1, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=74714. 2.0 MB in all.

- Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 644 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40343842&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF
- Photo 1 – Drawing of fuselage and tail section (item 2, .PDF, 90 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350497&FileExtension=.PDF&FileName=Photo%201%20%E2%80%93%20Drawing%20of%20%20fuselage%20and%20tail%20section-Master.PDF
- Photo 2 - View of the pulley and guard pin (NTSB Photo) (item 3, .PDF, 60 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350503&FileExtension=.PDF&FileName=Photo%202%20-%20View%20of%20the%20pulley%20and%20guard%20pin%20%20(NTSB%20Photo)-Master.PDF
- Photo 3 - Photo of fractured and separated elevator trim cables (Cessna Photo) (item 4, .PDF, 49 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350505&FileExtension=.PDF&FileName=Photo%203%20-%20Photo%20of%20fractured%20and%20separated%20elevator%20trim%20cables%20%20(Cessna%20Photo)-Master.PDF
- Photo 4 – Scanning Electron Microscope Photo (Cessna Photo) (item 5, .PDF, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350488&FileExtension=.PDF&FileName=Photo%204%20%E2%80%93%20Scanning%20Electron%20Microscope%20Photo%20%20(Cessna%20Photo)-Master.PDF
- Photo 5 – Scanning Electron Microscope Photo (Cessna Photo) (item 6, .PDF, 66 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350504&FileExtension=.PDF&FileName=Photo%205%20%E2%80%93%20Scanning%20Electron%20Microscope%20Photo%20%20%20(Cessna%20Photo)-Master.PDF
- Photo 6 – Close-up view of a guard pin (Cessna Photo) (item 7, .PDF, 50 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350492&FileExtension=.PDF&FileName=Photo%206%20%E2%80%93%20Close-up%20view%20of%20a%20guard%20pin%20%20(Cessna%20Photo)-Master.PDF
- Photo 7 - Close-up view of a guard pin (Cessna Photo) (item 8, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350498&FileExtension=.PDF&FileName=Photo%207%20-%20Close-up%20view%20of%20a%20guard%20pin%20%20(Cessna%20Photo)-Master.PDF
- Photo 8 – View of both guard pins and the upper cable pulley (NTSB Photo) (item 9, .PDF, 308 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350494&FileExtension=.PDF&FileName=Photo%208%20%E2%80%93%20View%20of%20both%20guard%20pins%20and%20the%20upper%20cable%20pulley%20%20(NTSB%20Photo)-Master.PDF
- Photo 9 – View of bottom guard pin of the upper cable pulley (NTSB Photo) (item 10, .PDF, 99 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350502&FileExtension=.PDF&FileName=Photo%209%20%E2%80%93%20View%20of%20bottom%20guard%20pin%20of%20the%20upper%20cable%20pulley%20%20(NTSB%20Photo)-Master.PDF
- Photo 10 – View of upper guard pin of the upper cable pulley (NTSB Photo) (item 11, .PDF, 101 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40350496&FileExtension=.PDF&FileName=Photo%2010%20%E2%80%93%20View%20of%20upper%20guard%20pin%20of%20the%20upper%20cable%20pulley%20%20(NTSB%20Photo)-Master.PDF
- Statement of Party Representatives to NTSB Investigation (item 12, .PDF, 334 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40343846&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF
- Release of Aircraft Wreckage, NTSB Form 6120.15 (item 13, .PDF, 55 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40343847&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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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