NTSB Identification: CHI05FA049.
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Accident occurred Tuesday, December 28, 2004 in Ironwood, MI
Probable Cause Approval Date: 01/31/2006
Aircraft: Piper PA-23-250, registration: N5398M
Injuries: 5 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The twin-engine airplane was substantially damaged during an in-flight collision with terrain following a loss of control in the airport traffic pattern. Approximately 20 minutes prior to the accident the pilot transmitted: "I've got single engine problems here mayday mayday." Radar track data depicted the aircraft established on a northwest course at 3,500 feet mean sea level. At the time the pilot reported the engine failure, track data showed the aircraft entered a descending left turn, losing 1,000 feet and reaching a south heading 24 seconds later. The pilot regained control of the aircraft and air traffic control provided guidance to the destination airport, which was the nearest airport. The pilot subsequently established the aircraft on approach to the airport. The pilot stated that he was going to circle the airport to the left and hand pump the gear down. The aircraft impacted terrain approximately one-quarter mile south of the runway in the side yard of a residence. The residence was located adjacent to airport property. A line of trees about 40 feet in height was located approximately 19 feet west of the accident site. No evidence of a tree strike was observed. The airplane came to rest resting on the nose and the wings. The empennage was oriented vertically, approximately 65 degrees relative to the terrain. The landing gear was extended. Examination of the left engine revealed a separation of the No. 4 cylinder head. The cylinder head had separated between the second and third cooling fin. Metallurgical examination revealed that the fracture was consistent fatigue cracking. Examination of the left propeller and propeller governor did not reveal any anomalies preventing normal operation of the feathering mechanism. Observations during the left propeller teardown were consistent with the propeller not being in the feathered position at the time of the accident. Maintenance records indicated that approximately 345 hours had accumulated on both engines since overhaul. No other anomalies were observed. According to the aircraft manufacturer's documentation, the accident aircraft hydraulic system was powered by one engine-driven hydraulic pump mounted on the left engine. Hydraulic pressure was used to control the retractable landing gear and the flaps. In the event the left engine loses power the hydraulic pump is not powered and emergency gear extension must be used.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Fatigue fracture of an engine cylinder resulting in a loss of power on the left engine. Additional causes were the pilot's failure to maintain minimum control airspeed (Vmc), the resulting loss of aircraft control, and an inadvertent stall/spin. Contributing factors were the pilot's failure to feather the propeller on the failed engine and his decision to turn toward the inoperative engine during the circling maneuver. Additional factors were the inoperative hydraulic system pump and the emergency landing gear actuation which caused the pilot to circle prior to landing.

Full narrative available

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