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NTSB AVIATION ACCIDENT/INCIDENT DATABASE REPORT


General Information

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 

Operations Information

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    

Narrative

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.

Sequence of Events

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

Probable Cause

THE FATIGUE FAILURE OF THE CRANKSHAFT.

Aircraft Information

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    

Environment/Operations Information

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

Pilot-in-Command

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