NTSB Factual Report

HISTORY OF FLIGHT

On April 7, 2002, at 1015 central daylight time, a Piper PA-46-310P, N9184F, sustained substantial damage during a forced landing to a road near Hastings, Minnesota, after a loss of engine power. The commercial pilot and three passengers were not injured. The CFR 14 Part 91 personal flight departed the St. Paul Downtown Airport (STP), St. Paul, Minnesota, about 1000 en route to Red Wing Regional Airport (RGK), Red Wing, Minnesota. Visual meteorological conditions prevailed. The flight was on a IFR flight plan to RGK.

The pilot reported he was, "In cruise and level at 3000' with an instrument clearance to start the GPS approach to RGK. I noticed a slight surging of the engine and observed manifold pressure cycling minus 3 inches and back to normal a couple of times which lasted just a few seconds then the manifold pressure became steady again at the cruise setting of 29.5 inches. About 30 seconds to one minute after the surging stopped the engine power suddenly reduced to no more than idle power and was running very rough. Then the power partially increased for a few seconds temporarily as a result of throttle and mixture manipulation. Then the engine lost all power with the prop wind milling and smoke coming from the front of the engine cowling. Immediately upon loosing the power I requested a vector from approach control to the nearest airport and was given a vector and the distance to the Red Wing (RGK) airport which turned out to be 11 miles. I knew I could not make it to the airport with little or no power since I was now at approximately 2200 feet AGL." The pilot executed a forced landing to a paved road, but during touchdown, the left wheel was off the left side of the pavement in the ditch. The airplane veered left off the road and sustained substantial damage when the left wing hit a small tree and the airplane skidded sideways across a road and into an open plowed field.

AIRPLANE INFORMATION

The airplane was a single engine Piper Malibu, PA-46-310P, s/n 8408068. The airplane seated six and had a maximum gross weight of 4,100 pounds. The last annual inspection was conducted on November 9, 2001. The airplane had flown 132 hours since the last inspection and had a total time of 5,574 hours.

The engine was a 310 horsepower Continental TSIO-550-C engine that was manufactured on March 14, 1997. On January 11, 2000, the engine was top overhauled with new cylinders and pistons. The engine time was 1,027 hours. The engine time at the last inspection on November 9, 2001, was 1,516 hours. At the time of the accident, the engine had flown 621 hours since the last top overhaul.

ENGINE INSPECTIONS

A Federal Aviation Administration airworthiness inspector conducted an inspection of the engine on April 16, 2002, at the St. Paul Downtown Airport, St. Paul, Minnesota. The inspection revealed that the engine case halves could not be completely separated due to internal damage. The airworthiness inspector reported, "The inspection revealed the connecting rods for cylinders 3, 4, and 5 were all broken loose from the crankshaft, and these three crank journals showed evidence of extreme heat. The connecting rod cap and bolts for cylinder 6 showed signs of excessive heat. So excessive that the cap nuts were melted on to the bolts on piston #6 connecting rod." The engine was sent to the engine manufacturer for disassembly and further inspection.

The engine inspection was conducted at Teledyne Continental Motors (TCM) in Mobile, Alabama, on June 28, 2002. The TCM report summarized the inspection by stating the following:

"The number 6 piston was fractured across the piston crown structure in line with the piston pin. A hole was burned in the piston near the center of the crown along a fracture line, to the piston interior. The fractured piston was cut to view the fractured section. After cleaning of combustion deposits from the fracture surfaces, the piston exhibited a fatigue fracture. The origin of this fracture was the crown surface. No number stamp or defects were observed at the fracture origin site.

After the hole was burned through the number 6 piston, the crankcase was pressurized and oil was exhausted. The engine experienced an oil starvation event followed by 3 connecting rods dislodged from the crankcase journals, damaging the crankcase, camshaft, and lifter boxes.

All other pistons were visually inspected and no fractures in the crown surface were observed." (See TCM Engine Analysis Report)

TESTS AND RESEARCH

The number 6 piston, P/N 654867, from the Continental TSIO-550-C engine, S/N 802557, was sent to the National Transportation Safety Board's (NTSB) Materials Laboratory for further examination. The NTSB Materials report stated the following:

"The piston was submitted in two separate sections, which were cut apart to expose the fracture surface prior to submittal. Examination of the surface between the two halves of the piston revealed the presence of a large pre-existing crack. The crack was found to be directly in-line with the pin axis…...Visual examination of the fracture surface from the piston half that contained the part markings revealed two fatigue regions. Both of the fatigue regions had a thumbnail shape, were flat, and contained crack-arrest marks. The origin area for the larger fatigue region was located at the top surface of the piston approximately 1.25 inch from the outer diameter. Approximately 0.6 inch from the origin location was a burned-through hole in the crown from flame erosion. The crack was approximately 2.1 inch wide by 0.7 inch deep. A smaller fatigue crack in the same plane initiated from the pin hole surface and propagated toward the crown…...This crack was approximately 0.6 inch wide by 0.18 inch deep. The closest part marking to the origin of the larger fatigue crack on the crown surface was approximately 0.6 inch away."

The NTSB inspection revealed that, "no material defects or surface anomalies such as abusive machining marks, nicks, or indentations were present at the origin of the larger fatigue crack." It also showed that base metal composition of the piston was consistent with alloy AE109 specification. (See NTSB Materials Laboratory Factual Report)

ADDITIONAL INFORMATION

An accident involving a Piper PA-46-310, N9298Y, which experienced an engine failure, occurred on November 26, 2000. The NTSB investigation, FTW01LA026, revealed that the number 4 piston had a fatigue crack and a burn through hole that was similar in nature to the fatigue failure found on N9184F. However, the piston in the FTW01LA026 investigation had a number stamp on the top of the piston crown, which acted as the initiation point of the crack propagation. During the course of the investigation of N9298Y, it was discovered that the airplane had experienced an earlier engine failure that was the result of a fatigue fracture of the number 6 piston. The FTW01LA026 report stated, "The number 6 piston exhibited a hole in the crown structure of the piston, and the hole was burned through the crown structure along a crack that extended from the forward side just past the center of the piston, in-line with the piston pin. A TCM metallurgist examined the crack and determined the fracture originated at the upper crown surface and progressed through the structure in fatigue. There were no marks stamped in the crown of the piston."

The engine manufacturer reported that it was in the process of redesigning the piston used in the 310 horsepower TSIO-550-C and 350 horsepower TSIO-550-E engines.

Parties to the investigation included the Federal Aviation Administration and Teledyne Continental Motors, Inc.

NTSB Probable Cause

The engine failure due to oil starvation as a result of the fatigue fracture of the number 6 piston. Additional factors were the unsuitable terrain for landing encountered by the pilot, and the inadequate piston design by the manufacturer.