# NTSB SEA96LA073: Cessna 500, N727TK, Salt Lake City, UT, April 1, 1996 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: March 31, 1996, 17:30 local (Apr 1, 1996, 00:30 UTC) - Place: Salt Lake City, UT - Coordinates: 40.809467, -111.940383 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.8095&lon=-111.9404&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 7 uninjured - Status: Completed, report August 21, 1997 - Report: Approved by Office Director - NTSB case key (mKey): 42349 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=SEA96LA073 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/42349/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=42349 - Page: https://openairdocs.org/ntsb/SEA96LA073 ## Probable cause fatigue failure of the engine compressor impeller. Inadequate quality control by the manufacturer was a related factor. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Loss of engine power(total) - mech failure/malf, takeoff - compressor assembly,impeller - fatigue (cause) - inadequate quality control, manufacturer (contributing factor) ## Analysis The pilot reported that during the takeoff ground roll, a loud 'boom' was heard, and the right engine lost power. The pilot aborted the takeoff and immediately brought the thrust lever to idle power. He stated that as the airplane was turning off of the runway onto a taxiway, the right engine 'blew.' The pilot continued to taxi the airplane back to the fixed base operator. After the airplane was secured, the pilot inspected the right engine and found evidence of an uncontained engine failure. Debris from the right engine had punctured the side of the pressure vessel and damaged the wing. Further inspection revealed the engine impeller had broken into two large pieces. A metallurgical examination of the impeller determined that a fatigue crack had originated from the aft face in the area containing a circumferential groove mark that was produced during machining of the aft face prior to blue etch anodizing. ## Factual narrative On March 31, 1996, approximately 1730 mountain standard time, a Cessna 500, N727TK, registered to and operated by TKA Express as a 14 CFR Part 91 business flight, experienced an uncontained engine failure during the take off ground roll at the Salt Lake City International Airport, Salt Lake City, Utah. Visual meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The airplane was substantially damaged, and the private and commercial pilots, and their five passengers were not injured. The flight was destined for Visalia, California. In written statements prepared by both pilots, they reported that the engine start and all pre-take off checks were completed with no abnormalities noted. The airplane was taxied to runway 35 and held for approximately ten minutes before the tower controller cleared the flight for take off. The first pilot reported that he advanced the thrust levers through 80-81%, when a loud "boom" was heard and the airplane began to shake. The second pilot stated that he looked out the right side window and noticed that the main fan from the right engine had come free and was flying through the air. The second pilot then looked at the right engine gages and noticed that there were no indications. The first pilot reported that he immediately brought the thrust lever for the right engine to idle power. When he was making the turn onto the taxiway to clear the runway, the right engine "blew." The first pilot continued to taxi back to the fixed base operator (FBO) as the second pilot notified the control tower of the situation. After the engines were shut down and the passengers were deplaned, both pilots inspected the right engine and found that it was smoldering. It was noted that debris from the engine had punctured the side of the pressure vessel and damaged the wing. Inspection of the engine by a Federal Aviation Administration inspector from the Salt Lake City Flight Standards District Office discovered that the impeller had broken into two large pieces. The impeller was removed from the engine and sent to the National Transportation Safety Board Metallurgical Lab for inspection. During the inspection the metallurgist reported that "a fatigue crack emanated from multiple origins on the aft surface..." The metallurgist further stated that "...this fracture revealed that the immediate fatigue origin area contained mechanical damage that obliterated the original fracture features. However, just off but near the origin the fracture was undamaged and displayed clear evidence of fatigue striations..." Calculations made by the metallurgist to determine the number of striations, indicates that the fatigue crack propagated a total of 8,066 cycles from the origin to the terminus. The impeller has a limited life of 8,400 flight cycles, after which it must be replaced. A representative from Pratt & Whitney Canada reported that the impeller is forged, then machined to final shape. After machining, the impeller is blue etch anodized to determine if the surfaces "contain metallurgical anomalies." Examination of the impeller indicated that the exposed surfaces did exhibit a blue tint, which is indicative of blue etch anodizing. Further examination revealed that the reduced balance tab area and the holes located on the flange were a gray color typical of the base metal without the blue etch anodizing. The metallurgist reported that "SEM examination of the blue tint surfaces revealed minute pin-hole-like features, whereas, the surface of the reduced balance tab area and holes on the flange contained features typical of a machined surface with no pin-hole-like features." The Pratt & Whitney representative reported that this impeller was forged in 1975, and machined in 1976. The impeller was installed in the accident engine when the engine was manufactured. The aircraft flight log indicates, as of 3/29/96, total engine cycles of 5,134. Maintenance records indicate that the aircraft has operated in both the United States and for several years in Mexico. The aircraft was returned to U.S. registry in 1995. The records available to determine the entire history of maintenance performed and the total number of cycles on this engine are incomplete. It was determined that at the time of the accident, the engine had accumulated approximately 3,400 hours since the last overhaul dated in 1980. ## Aircraft - Registration: [N727TK](https://openairdocs.org/deregistered/N727TK-2017-03-24), registration cancelled 2017-03-24, S/N 500-0141, built 1974 (OpenAirDocs) - Reported make and model: Cessna 500 - Registry model: [Cessna 500](https://openairdocs.org/model/cessna-500) (registry code 2076602) (OpenAirDocs) - Registry engine: [Pratt & Whitney Canada JT15D-1A](https://openairdocs.org/engine/pratt-whitney-canada-jt15d-1a) (registry code 52110, turbo-fan) (OpenAirDocs) - Category: Airplane - Serial number: 500-0141 - Airframe hours: 6714 - Engines: P&W JT15D-1A 2200 lbs thrust turbo fan - Damage: Substantial damage - Flight: Business, Part 91 - Registered owner: Tka Express - Airworthiness certificate: Standard, Normal - Last inspection: AAIP, February 12, 1996, 18 hours before - Departed: SLC - Destination: VIS, VISALIA, CA - Flight plan: IFR - Airport: SLC, Salt Lake City Intl, runway 35, 9,596 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; private; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--w/ waivers/lim; seat: left; flight hours: 3,800 total, 700 in this make and model, 3,700 as pilot in command, 30 in the last 90 days, 10 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Visibility: 50 statute miles - Lowest ceiling: none - Temperature: 50 °F ## 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 19960331007529A](https://openairdocs.org/incident/19960331007529A), Mar 31, 1996: Cessna 500CESSNA, Salt Lake City, UT, Substantial damage. Uncontained engine failure on takeoff roll. Loud boom right engine blew up. Aborted. Engine near tbo from 1980. (-16) during takeoff roll #2 engine compressor… ## Docket (5 files) The files NTSB released with the investigation on April 29, 1997, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=42349. 2.3 MB in all. - Supplement E (item 1, .PDF, 182 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40465699&FileExtension=.PDF&FileName=Supplement%20E-Redacted.PDF - Supplement S (item 2, .PDF, 63 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40066989&FileExtension=.PDF&FileName=Supplement%20S-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2 - Donald L. Allyn (item 3, .PDF, 543 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40465700&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%2F2%20-%20Donald%20L.%20Allyn-Redacted.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1/2 - Cameron C. Dumas (item 4, .PDF, 590 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40465701&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1%2F2%20-%20Cameron%20C.%20Dumas-Redacted.PDF - NTSB Metallurgist's Factual Report (item 5, .PDF, 936 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40066992&FileExtension=.PDF&FileName=NTSB%20Metallurgist%27s%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. --- 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.