# NTSB CHI01IA047: Cessna 172S, N582SP, St. Cloud, MN, December 12, 2000 - Type: NTSB incident investigation - Classification: Incident · No injuries · Incident investigation · Final report - Date: December 12, 2000, 14:00 local (20:00 UTC) - Place: St. Cloud, MN - Coordinates: 45.550132, -94.170761 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.5501&lon=-94.1708&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report September 6, 2001 - Report: Approved by Office Director - NTSB case key (mKey): 50785 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CHI01IA047 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/50785/pdf - Page: https://openairdocs.org/ntsb/CHI01IA047 ## Probable cause the fatigue failure of the propeller blade during the initial takeoff climb. The failure was a result of a material defect, which occurred during the manufacturing process and the manufacturers failure to detect the defect. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Airframe/component/system failure/malfunction, takeoff - initial climb - propeller system/accessories,blade - separation (cause) - propeller system/accessories,blade - fatigue (cause) - material defect (cause) - inadequate quality control, manufacturer (cause) - Forced landing, emergency landing after takeoff - Occurrence ## Analysis The outer 14 inches of one of the propeller blades separated during takeoff at an altitude of 400 to 500 feet above the runway. The certified flight instructor was able to land the airplane on a parallel taxiway without incident. The propeller had 236 hours total time at the time of the incident. Metallurgical examination revealed that about 60 percent of the fracture surface contained features typical of fatigue cracking which emanated from the flat face of the blade arm, near the trailing edge. The examination also revealed the microstructure was normal with the exception that the grain flow pattern followed the surface of the scallop region and not the surface of the blade. Chromium present in the scalloped region of the fracture and not on the fatigued surface indicated that the chromic anodized solution penetrated the indication during the anodizing process prior to the blade being painted. ## Factual narrative On December 12, 2000, at 1400 central standard time, a Cessna 172S, N582SP, experienced a separation of a portion of one of the propeller blades on takeoff. The takeoff was being made on runway 31 (5,200 feet by 100 feet) at the St. Cloud Regional Airport, St. Cloud, Minnesota. The separation occurred at an altitude of 400 to 500 feet above the runway and the certified flight instructor (CFI) was able to land the airplane on a parallel taxiway without incident. The CFI and the student pilot on board were not injured. The airplane received minor damage from vibration as a result of the propeller separation. The 14 CFR Part 91 instructional flight was operating in visual meteorological conditions and no flight plan was filed. The local flight was originating at the time of the incident. A review of maintenance records and aircraft times revealed the propeller had 236 hours of total time prior to this incident. The propeller was removed from the airplane and was shipped to the NTSB Metallurgical Laboratory in Washington D.C. for examination. The portion of the blade that separated was recovered at a later date and it too was shipped to the metallurgical laboratory. Inspection of the propeller revealed one blade had fractured about 14 inches from the centerline of the propeller hub. The Material Laboratory Factual Report stated, "Examination revealed that about 60 percent of the fracture surface was on a flat chordwise plane, was faceted in appearance, and contained crack arrest positions, features typical of fatigue cracking in wrought aluminum alloys. The features in the fatigue region emanated from the flat face of the blade arm, near the trailing edge.... The fracture surface forward of the fatigue region was matte in appearance and on an irregular plane that was generally oriented at a 45 degree angle to the spanwise direction, typical of an overstress region stemming from the fatigue region." A metallographic examination of the propeller blade indicated, "...the microstructure for the propeller was normal with the exception that the grain flow pattern followed the surface of the scallop region and not the surface of the blade." A metallurgical evaluation performed by Alcoa concluded "The presence of Cr [chromium] in the 'scalloped' region and not on the fatigued surface indicates that the chromic anodized solution penetrated the indication during the anodizing process. This observation, the grain flow below the 'scalloped' area...and the morphology of the 'scalloped' area indicate that the discontinuity was open to the surface prior to painting." See attached Material Laboratory Factual Report for more details. ## Aircraft - Registration: [N582SP](https://openairdocs.org/aircraft/N582SP), registered now, S/N 172S8509, built 2000 (OpenAirDocs) - Reported make and model: Cessna 172S - Registry model: [Cessna 172S](https://openairdocs.org/model/cessna-172s) (registry code 2072439) (OpenAirDocs) - Registry engine: [Lycoming I0360 SER A&C](https://openairdocs.org/engine/lycoming-i0360-ser-a-c) (registry code 41511, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 172S8509 - Engines: Lycoming IO-360 180 horsepower reciprocating - Damage: Minor damage - Flight: Instructional, Part 91 - Operator: Modern Aero - Registered owner: Arken Air, Inc. - Airworthiness certificate: Standard, Normal - Last inspection: Annual, November 13, 2000 - Departed: STC - Airport: STC, St. Cloud Regional, runway 31, 5,200 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 23; commercial, flight instructor; airplane ratings: single-engine sea, single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; seat: right; flight hours: 800 total, 250 in this make and model, 680 as pilot in command, 200 in the last 90 days, 50 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 240° at 9 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 27 °F - Altimeter: 30.00 inHg - Observed at: STC ## 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 20001212028289I](https://openairdocs.org/incident/20001212028289I), Dec 12, 2000: Cessna 172S, St Cloud, MN, Minor damage. (-23)During departure from the saint Cloud regional airport (STC), the a/c experienced a failure of the propeller. The propeller failed approx. 14 inches from… 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.