# NTSB CHI93IA382: Fairchild SA-227-AC, N446MA, Grand Rapids, MN, August 30, 1993 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: August 30, 1993, 12:30 local (17:30 UTC) - Place: Grand Rapids, MN - Coordinates: 47.219654, -93.520751 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=47.2197&lon=-93.5208&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report September 26, 1994 - Report: Approved by Office Director - NTSB case key (mKey): 9201 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI93IA382 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/9201/pdf - Page: https://openairdocs.org/ntsb/CHI93IA382 ## Probable cause the fractured aileron cable and other maintenance personnel's inadequate maintenance/adjustment. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, maneuvering - flt control syst,aileron control cable/rod - fractured (cause) - maintenance,adjustment - inadequate, other maintenance personnel (cause) ## Analysis THE FLIGHT CREW WAS ON A REPOSITIONING FLIGHT. THE CREW EXPERIENCED A RESTRICTION TO AILERON CONTROL WHILE MANEUVERING TO LAND. ON APPROACH TO LANDING THERE WAS LIMITED AILERON CONTROL TO THE LEFT, AND NO AILERON CONTROL TO THE RIGHT. THE AIRPLANE LANDED SUCCESSFULLY. SUBSEQUENT EXAMINATION OF THE AILERON CABLE DISCLOSED THAT IT WAS BROKEN. AN INDEPENDENT METALLURGICAL EXAMINATION OF THE CABLE REVEALED THAT THE FAILURE WAS CONSISTENT WITH IT HAVING COME OFF THE PULLEY AND WEARING AGAINST A SMALL DIAMETER STEEL PIN. AFTER THE INCIDENT, A COMPLETE INSPECTION OF THE AIRLINE'S FLEET WAS CONDUCTED ON THE AILERON CONTROL CABLES AND NO SIMILAR DISCREPANCIES WERE FOUND. ## Factual narrative On August 30, 1993, at 1230 central daylight time, a Fairchild SA-227-AC, N446MA, registered to Mesaba Aviation, Inc. of Minneapolis, Minnesota, and operated by a crew of one ATP rated pilot and a commercial instrument rated pilot, experienced a restriction of aileron control while maneuvering to land at Grand Rapids/Itasca County Airport, Grand Rapids, Minnesota, on runway 34 (5,755' x 100' dry/asphalt). The flight landed without incident and a broken aileron cable was found on examination. The flight was a CFR 14 Part 91 repositioning flight that had departed Thief River Falls, Minnesota, exact time unknown, on an IFR flight plan. No passengers were on board the flight. Visual meteorological conditions prevailed at the time of the incident. The airplane sustained no structural damage and the two crew members reported no injuries. The pilot stated that during a right turn, the yoke snapped free to the right. Some aileron control to the left was possible, but limited. There was no aileron control to the right. Minneapolis Center was contacted and advised of the situation. The crew elected to land with one half flap setting. During the final approach, the crew experienced what appeared to be aileron lockup, but with force, freed the controls. The airplane landed on runway 34. On examination the aileron cable was found to be broken. The aileron cable was replaced and the airplane was returned to service. Due to this incident, Mesaba conducted a complete system survey on their fleet of 21 Metro III aircraft, to inspect aileron cables. No additional discrepancies were found. A metallurgical examination of the broken aileron cable was conducted on September 27, 1993, by AADFW, Inc., in Euless, Texas, at the request of the Federal Aviation Administration to determine the tensile strength, chemical composition, and failure mode of the broken cable. A copy of the report is attached as an addendum to this report. The conclusion stated in the report was that the pulley over which the cable was routed was phenolic and did not appear to have any wear to the extent that would be expected if a steel cable in contact with the pulley had worn as much as the cable in this investigation. The reported indicated that it was more probable that the cable came off the pulley and had worn against a small diameter steel pin. The report further stated that service of the cable over a pin would provide higher stresses in the cable because of bending over an unacceptably small diameter pin. Such service would also provide a pivot pin that is most likely harder than the cable against which the cable would rub and wear. Service such as described above would be expected to result in fatigue failures of the cable wires that would appear exactly like what was observed in the laboratory. ## Aircraft - Registration: [N446MA](https://openairdocs.org/deregistered/N446MA-2005-03-18), registration cancelled 2005-03-18, S/N AC-693B, built 1987 (OpenAirDocs) - Reported make and model: FAIRCHILD SA-227-AC - Registry model: [Fairchild SA227-AC](https://openairdocs.org/model/fairchild-sa227-ac) (registry code 3377509) (OpenAirDocs) - Registry engine: [AiResearch TPE331 series](https://openairdocs.org/engine/airesearch-tpe331-series) (registry code 01514, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: AC-693 - Airframe hours: 11069 - Engines: GARRETT TPE-331-11U turbo prop - Damage: No damage - Flight: Business, Part 91 - Operator: Mesaba Aviation, Inc., doing business as Northwest Airlink - Registered owner: Nationasbanc Leasing Corp - Airworthiness certificate: Standard, Normal - Departed: TVF, THIEF RVE FALLS, MN - Flight plan: IFR - Airport: GPZ, Grand Rapids, runway 34, 5,755 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 34; airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, unknown; seat: left; flight hours: 5,200 total, 2,400 in this make and model, 200 in the last 90 days, 9 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 10 knots, gusting 16 - Visibility: 10 statute miles - Lowest ceiling: 2,100 ft broken - Temperature: 59 °F, dew point 55 °F - Altimeter: 29.00 inHg - Observed at: GPZ ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Incident 19930830038759I](https://openairdocs.org/incident/19930830038759I), Aug 30, 1993: Swrngn SA227AC, Grand Rapids, MN, Minor damage. No aileron control to right. Control maintained with differentail power and rudder. Aireron cable broken. 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.