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Data Source: NTSB AVIATION ACCIDENT/INCIDENT DATABASE Report Number: CHI95LA024 Local Date: 10/22/1994 Local Time: 13:08 CDT State: ND City: GRAND FORKS Airport Name: Airport Id: Event Type: ACCIDENT Injury Severity: NONE Report Status: FINAL Mid Air Collision: NO
Category of Operation: GENERAL AVIATION Aircraft Type: AIRPLANE Aircraft Damage: SUBSTANTIAL Phase of Flight: 540 CRUISE Aircraft Make/Model: PIPER PA-18-XXX Operator Doing Business As: Operator Name: Operator Code: Operator: Owner Name: UNIVERSITY OF NORTH DAKOTA
THE FLIGHT INSTRUCTOR AND STUDENT WERE EN ROUTE BACK TO THEI R HOME BASE AFTER PRACTICING LANDINGS AT A LOCAL AIRPORT. APPROXIMATELY EIGHT MILES FROM THEIR DESTINATION, THE ENGINE BEGAN TO RUN ROUGH. THE PROPELLER BECAME UNATTACHED AND THE ENGINE COMPLETELY STOPPED RUNNING. A FORCED LANDING WAS MADE ON A FIELD WITHOUT FURTHER INCIDENT. POSTACCIDENT EXAMINATION REVEALED THE CRANKSHAFT HAD COMPLETELY FRACTURED . EXAMINATION OF THE CRANKSHAFT REVEALED A FATIGUE FAILURE INITIATING FROM AN OIL TRANSFER TUBE HOLE. THIS ORIGIN HOLE WAS FOUND TO HAVE AN ENLARGED DIAMETER PORTION ABOVE THE SPECIFIED VALUE. EXAMINATION OF THE AIRPLANE'S LOGBOOK REVE ALED THIS AIRPLANE WAS INVOLVED IN A PROPELLER STRIKE FOUR YEARS AND 1,220 FLIGHT HOURS PRIOR TO THIS ACCIDENT.
Occurrence #: 1 351 LOSS OF ENGINE POWER (TOTAL) - MECH FAILURE/MALF
Phase of Operation: 540 CRUISE
Findings
Subject - Modifier - Personnel Cause/Factor
1a. 14004(S) - 1135(M) Cause
ENGINE ASSEMBLY, CRANKSHAFT - FAILURE, TOTAL
2a. 14004(S) - 1137(M) Cause
ENGINE ASSEMBLY, CRANKSHAFT - FATIGUE
Occurrence #: 2 180 FORCED LANDING
Phase of Operation: 552 DESCENT - EMERGENCY
Findings
Subject - Modifier - Personnel Cause/Factor
Occurrence #: 3 230 IN FLIGHT COLLISION WITH TERRAIN/WATER
Phase of Operation: 552 DESCENT - EMERGENCY
Findings
Subject - Modifier - Personnel Cause/Factor
1a. 19200(S) - 2417(M)
TERRAIN CONDITION - OPEN FIELD
THE FATIGUE FAILURE OF THE CRANKSHAFT.
Number of Seats: 2
Aircraft Use: INSTRUCTIONAL
Type of Operation: 14 CFR 91
Domestic/International:
Passenger/Cargo:
Registration Number: 587PA
Air Carrier Operating Certificates:
Aircraft Fire: NONE
Injuries
Fatal Serious Minor None
Crew 0 0 0 1
Pass 0 0 0 1
Other 0 0 0 0
Invlvd 0 0 0 2
Landing Gear: TAILWHEEL-ALL FIXED
Certificated Maximum Gross Weight: 1750
Engine Make: LYCOMING
Engine Model: O-320-A2B
Number of Engines: 1
Engine Type: RECIPROCATING-CARBURETOR
Basic Weather Conditions: VISUAL METEOROLOGICAL CONDITIONS (VMC) Wind Direction (deg): 240 Wind Speed (knots): 17 Visibility (sm): 15 Visibility RVR (ft): 0 Visibility RVV (sm): 0 Cloud Height Above Ground Level (ft): 10000 Visibility Restrictions: NONE Precipitation Type: NONE Light Condition: DAYLIGHT Departure Airport Id: ND24 Departure City: INKSTER Departure State: ND Destination Airport Id: GFK Destination City: Destination State: ND Flight Plan Filed: NONE ATC Clearance: NONE VFR Approach/Landing: FORCED LANDING Event Location: OFF AIRPORT/AIRSTRIP
Certificates: COMMERCIAL, FLIGHT INSTRUCTOR
Ratings:
Plane: SINGLE ENGINE LAND
Non-Plane: NONE
Instrument: AIRPLANE
Had Current BFR: YES
Months Since Last BFR: 5
Medical Certificate: CLASS 1
Medical Certificate Validity: VALID MEDICAL-NO WAIVERS/LIMITATIONS
Flight Time (Hours)
Total : 1833 Last 24 Hrs : 3
Make/Model : 18 Last 30 Days: 25
Instrument : 852 Last 90 Days: 52
Multi-Engine: 135 Rotorcraft : 0
NTSB Identification: CHI95LA024. The docket is stored in the (offline) NTSB Imaging System.
Accident occurred OCT-22-94 at GRAND FORKS, ND
Aircraft: PIPER PA-18, registration: N587PA
Injuries: 2 Uninjured.
THE FLIGHT INSTRUCTOR AND STUDENT WERE EN ROUTE BACK TO THEIR HOME BASE AFTER
PRACTICING LANDINGS AT A LOCAL AIRPORT. APPROXIMATELY EIGHT MILES FROM THEIR
DESTINATION, THE ENGINE BEGAN TO RUN ROUGH. THE PROPELLER BECAME UNATTACHED AND
THE ENGINE COMPLETELY STOPPED RUNNING. A FORCED LANDING WAS MADE ON A FIELD
WITHOUT FURTHER INCIDENT. POST ACCIDENT EXAMINATION REVEALED THE CRANKSHAFT HAD
COMPLETELY FRACTURED. EXAMINATION OF THE CRANKSHAFT REVEALED A FATIGUE FAILURE
INITIATING FROM AN OIL TRANSFER TUBE HOLE. THIS ORIGIN HOLE WAS FOUND TO HAVE AN
ENLARGED DIAMETER PORTION ABOVE THE SPECIFIED VALUE. EXAMINATION OF THE
AIRPLANE'S LOGBOOK REVEALED THIS AIRPLANE WAS INVOLVED IN A PROPELLER STRIKE
FOUR YEARS AND 1,220 FLIGHT HOURS PRIOR TO THIS ACCIDENT.
Probable Cause
the fatigue failure of the crankshaft.
Full Narrative:
On October 22, 1994, at 1308 central daylight time, a Piper PA- 18, N587PA, registered to the University of North Dakota, sustained substantial damage following a loss of engine power and subsequent forced landing near Grand Forks, North Dakota. The flight instructor and student pilot were not injured. The 14 CFR Part 91 local instructional flight operated in visual meteorological conditions without a flight plan. The flight departed Inkster Airport, Inkster, North Dakota, at 1255 with an intended destination of Grand Forks International Airport.
After practicing several takeoffs and landings at Inkster Airport, the flight instructor and student began their return flight to Grand Forks. While approximately eight miles from Grand Forks, the instructor reported the engine began to run rough for a one to two second period at 2400 RPM. Immediately after the engine roughness was experienced, the propeller became unattached and the engine lost all power. A forced landing was made on a field without further incident.
Post accident examination revealed the crankshaft had completely fractured. The failed crankshaft was sent to the NTSB Materials Laboratory, Washington, D.C., for examination. The laboratory reported that the separation of the crankshaft occurred at an oil transfer tube hole in the main bearing journal. This fracture was caused by fatigue. The fatigue cracking propagated through the journal on a 45 degree plane to the longitudinal direction of the crankshaft. The initial direction of the cracking is consistent with torsional loading condition. Further examination of the origin hole disclosed the depth of the enlarged diameter portions were significantly above the specified value. Normal depth is between 0.078 inch to 0.088 inch. Measurement of the oil hole was found to be 0.139 inch. See attached Metallurgist Report.
The airplane logbook shows the last inspection was an annual inspection performed on November 16, 1994. The airplane had logged 27 hours since the inspection. Total time on the engine at the time of the accident was 1809. The logbook also revealed that N587PA experienced a propeller strike in May, 1991, at 589 total time. As a result of this strike the propeller was replaced. Compliance with Airworthiness Directive for post propeller strike inspection was not accomplished because this incident was classified as minor.
The engine manufacturer was present during the examination of the crankshaft. The manufacturer reported that there are approximately 40,000 of this type of engine in service today with no known incidents of similar failure without a previous incident of a propeller strike.
Source: National Transportation Safety Board