Piper PA-31-350 Navajo Chieftain

The Piper PA-31-350 Navajo, C-GHMK, departed from St. Andrews, Manitoba, on a visual flight rules charter flight to Berens River. One pilot and ten passengers, including one infant, were on board, and a dog was stowed in the baggage compartment behind the right, rear seat. At approximately 1530 central daylight saving time (CDT), while the aircraft was at an altitude of about 2 500 feet and about 30 nautical miles south of Berens River, the pilot heard a loud sound from the left engine. He saw deformation of the left engine cowling and smoke coming from the engine, and the aircraft yawed to the left. Part of the engine cowling departed in flight. The pilot could not pull the left propeller lever beyond half of its normal travel, nor could he move it into the feather position. He set maximum power on the right engine, but the aircraft did not maintain altitude. The pilot advised company dispatch over the radio that he would attempt a forced landing, then force landed in a mossy marsh area. Everyone on board, including the dog, deplaned. Five of the passengers sustained minor injuries during the evacuation. A fire ensued, completely destroying the aircraft except for the empennage aft of the horizontal stabilizers.

Probable cause:

Findings as to Causes and Contributing Factors:
1. The number three cylinder lower forward through stud was missing its base nut, which allowed the lower rear base nut of the number two cylinder to loosen.
2. The missing base nut of the through stud indicates that the base nut did not have sufficient clamping force; however, it could not be determined if the base nut did not receive the required torque during installation or if the base nut lost its clamping force during engine operation.
3. The d-inch studs and the 2-inch through studs of the number two cylinder failed in fatigue, and the number two cylinder of the left engine separated from the crankcase.
4. The left propeller could not be feathered because of interference between the propeller governor control and the separated number two cylinder.
5. The drag from the unfeathered left propeller and the deformed left engine cowling resulted in the aircraft being incapable of maintaining its altitude.
Other Findings:
1. The pilot was certified and qualified for the accident flight.
2. The aircraft's weight and balance were within the specified limits at the time of the accident.
3. The ELT was not readily accessible without tools.

Final Report:

Crash of a Piper PA-31-350 Navajo Chieftain in Tanana: 1 killed

Date & Time: Jun 11, 1999 at 0723 LT

Type of aircraft:

Piper PA-31-350 Navajo Chieftain

Operator:

Registration:

N41078

Flight Phase:

Takeoff (climb)

Flight Type:

Cargo

Survivors:

Site:

Airport (less than 10 km from airport)

Schedule:

Fairbanks – Tanana – Galena

MSN:

31-8352017

YOM:

1983

Flight number:

LFS1604

Location:

Tanana

Alaska

Country:

United States of America

Region:

North America

Crew on board:

Crew fatalities:

Pax on board:

Pax fatalities:

Other fatalities:

Total fatalities:

Captain / Total flying hours:

3227

Captain / Total hours on type:

861.00

Aircraft flight hours:

15229

Circumstances:

A twin-engine airplane on a scheduled passenger/cargo flight, departed a rural airport located along the north shore of the Yukon River with only the pilot aboard. The airplane appeared to depart normally, but remained low, flying over the river, about 200 feet above the ground. About five minutes after departure, the pilot contacted a local weather observation facility on the common traffic advisory frequency (CTAF), and reported he was having a problem with the airplane, stating he may have to ditch. He did not describe the nature of the problem. The pilot then said he was clipping trees, and was attempting to return to the runway. The airplane collided with several trees located on a gravel bar in the Yukon River, separating the outboard end of the left wing. The airplane then collided with the river and sank, about 1.5 miles south of the airport. A fast river current, and silty water conditions hampered recovery efforts, but the left wing, the left engine, and the fuselage were recovered from the river. The left engine propeller appeared to be feathered. The right wing and the right engine were not recovered. Postaccident examination of the left engine disclosed no evidence that it was producing power upon impact, or any evidence of any preimpact mechanical malfunction. Inspection of the airframe disclosed no evidence of any preimpact mechanical malfunction.

Probable cause:

The exact cause of the accident could not be determined.

Final Report: