N711EX

History of Flight

On October 18, 1995, about 2055 eastern daylight time, a Piper PA-31-350, N711EX, ditched in the Atlantic Ocean, approximately 6 miles south of John F. Kennedy International Airport (JFK) Jamaica, New York, and was substantially damaged. The airline transport pilot (captain) and three passengers were not injured. The commercial pilot (first officer) received minor injuries, and one passenger was fatally injured. Visual meteorological conditions prevailed, and an IFR flight plan had been filed for the flight, which departed Atlantic City, New Jersey, approximately 2010. The on-demand air taxi flight was being conducted in accordance with 14 CFR Part 135.

While descending from 5000 feet to 3000 feet, en route to Farmingdale, New York, the pilot was in contact with JFK Approach Control. He informed the controller at JFK that the left engine had failed and the engine cowling was open. The pilot declared an emergency and requested a landing at JFK. The controller cleared the pilot to land on runway 4.

The crew performed the emergency checklist and feathered the left propeller. The captain said that he could see the three propeller blades, but could not determine if the blades were feathered. The crew said that after everything was secured and the right engine was at full power, they could not arrest a 300 to 500 feet-per-minute rate of descent. The captain then told the first officer to instruct the passengers to don their life vests, and to advise them that they were going to ditch in the water. The crew also informed JFK that they could not make the airport and would be landing in the water. The pilot asked JFK to send rescue help.

After landing in the water, all the occupants exited the airplane from the left front pilot's emergency door. The airplane sank in approximately 85 feet of water. The victims were in the water for approximately 30 minutes before being rescued by a Coast Guard Helicopter and a New York City Police Boat. One of the passengers was in cardiac arrest when he was retrieved from the water.

The accident occurred during the hours of darkness at approximately 40 degrees, 31 minutes north, and 73 degrees, 45 minutes west.

PERSONNEL INFORMATION

Information on the pilot is contained in this report under First Pilot Information and Second Pilot Information, Supplement "E".

AIRCRAFT INFORMATION

The engine log books showed that the left engine was overhauled by T. W. Smith Engine Co., Inc. on January 31, 1994, with a total accumulated time of 4970.5 hours. The log book listed the AD notes and service bulletins that had been complied with at the time the engine was rebuild. These included Service Instruction 1123C, which is discussed in the Additional Information section below. At 268.2 service hours since overhaul; all cylinders were removed from the engine and oversize thru-studs were installed. The engine log book entry reported that the thru-stud installation was performed in accordance with Lycoming's, service instruction (SI) 1290D, with T. W. Smith Co., performing the over sizing of the bores. The engine was then reassembled by a second mechanic for the operator. The accident occurred approximately 80 hours after the thru-studs were replaced. Further information on the aircraft is contained in this report under Aircraft Information.

METEOROLOGICAL INFORMATION

Visual meteorological conditions prevailed at the time of the accident. Meteorological information is contained in this report under Weather Information.

WRECKAGE AND IMPACT INFORMATION

The aircraft crashed in the waters of the Atlantic Ocean, approximately 6 miles south of JFK Airport. The airplane was found and recovered from the ocean on November, 3, 1995, and examined at parking lot near Jamaica, New York.

Examination of the wreckage revealed that it was intact and had sustained very little damage during impact with the water. Several sections of the airplane's fuselage, wings and nose section were damaged during the removal of the airplane from the water. The left engine cowling was not recovered from the water, and was not examined.

Continuity of the flight control systems was established. The flaps and the landing gear were found retracted.

Examination of the engines revealed that cylinder #2 on the left engine had separated and was found lying on the bottom of the ocean, about 20 feet from the wreckage. Both engine's were corroded by the salt water. The left engine was removed from the airframe for further examination. Examination of the right engine revealed no discrepancies.

TEST AND RESEARCH

The left engine was shipped to Lycoming's facilities, in Williamsport, Pennsylvania, and was dissembled under the supervision of the NTSB on December 19, 1995.

The exterior examination of the engine revealed that it was corroded and some of the steel parts were rusting. The #2 cylinder was separated from it's mounting pad. The #2 connecting rod and piston were not located.

The engine was completely disassembled and the crankcase showed that "o" ring seals were used to seal the outside two forward nose bolts, the two forward, #2 cylinder hold down studs, and the two rearward, #5 cylinder hold down studs. According to Lycoming this is "not approved" by the engine manufacturer. The interior of the crankcase revealed crankcase dowels and rubber "o" rings at thru-studs locations.

It was determined that markings on the crankcase indicated that the crankcase had been reworked, to include welding, and the installation of oversize thru-studs. It was determined that the oversize thru-studs were installed the doweled crankcase with an incorrect fit.

A section of the left crankcase was cut, and shipped to the NTSB Materials Laboratory in Washington, DC, for further examination.

The forward portion of the left crankcase half, #2 cylinder with piston and thru-studs (2), were examined at the NTSB Materials Laboratory. According to the Metallurgist's Factual Report, initial examination showed that the engine case half was fractured in several locations. The lower three cylinder studs were fractured and the upper three studs were not received. The two thru-studs were fractured with the fracture ends on the left (#2 cylinder) side of the crankcase. The #2 cylinder head and barrel were mechanically damaged and the aluminum head showed "extensive corrosion." The #2 piston was found intact, but had "suffered corrosion attack to the dome."

Optical inspection of the case fracture surfaces uncovered features typical of "overstress separations" in cast aluminum with no indications of "preexisting cracks." "No evidence of weld repair was visible on the received portion of the case."

Fretting damage was observed on the parting surface of the case, and polishing on the "faying" surfaces of the propeller bearing bosses around the #2 main bearing thru-stud holes. The upper bosses exhibited light polishing while more wide spread polishing and areas of light to moderate fretting were present on the lower boss surface. The #3 main bearing bosses showed light wear and fretting, and the lower boss had a "prominent" impression adjacent to the bearing surface. The impression was consistent with contact by the "anti-rotation tang" of the right half of the bearing shell.

The #2 cylinder mounting pad exhibited several areas of denting and other mechanical damage. Two of the dents matched the shape of the inboard edge of the piston skirt. The cylinder pad displayed several areas of light to moderate fretting, in the lower aft quadrant around the lower thru-stud and on the case at the upper left stud.

The three cylinder hold down studs were fractured. The lower forward 1/2 inch diameter (large), and the lower aft 3/8 inch (small) studs were fractured through the forward fine nut threads about 0.4 inches above the deck. The lower forward small stud was fractured flush with the deck through the coarse case threads.

The NTSB Metallurgist's Factual Report stated; "...magnified optical examinations revealed high stress fatigue features through about 2/3 of the small lower aft stud...the fatigue initiated at multiple origin sites in a thread root on the cylinder hole side of the stud...the fatigue penetrated...about 2/3 of the stud cross section, with the remainder having overstress features. The lower forward small stud also displayed similar high stress fatigue features...but the extent was not optically apparent...."

All three studs were sectioned from the case, ultrasonically cleaned in acetone, and each stud was examined with a scanning electron microscope (SEM).

According to the NTSB Metallurgist's Factual Report; "SEM viewing confirmed the observations on the lower aft small stud, as high stress fatigue from multiple origins with about 60 to 80% penetration of the stud. The lower forward small stud fracture also displayed fatigue features from multiple origins. The extent of the fatigue progression through the bolt was found to be 60 to 80% of the studs cross section...the large stud...surface damage...flatten [sic] the taller fracture features giving the surface a polished appearance...fatigue striations were detected between the damage areas on about 80 to 90% of the stud surface...specific fatigue initiations sites were not found, however the striation orientations suggest that the fatigue progressed from the thread root on the cylinder centerline side of the stud...examination also revealed a small crack in the adjacent thread root that was opened during the fracture of the stud. The crack was fatigued from multiple initiation sites."

The upper and lower #3 main bearing thru-bolt studs were both fractured through the threads of the #2 cylinder. The upper thru-stud was cut off and SEM examined. Examination revealed "heavy fracture face rubbing damage" that obscured much of the fracture topography in the traverse area. "Fatigue striations" were fou...