Piper PA-31-350 N3BT

Summary

On 14 October 2008 at about 15:05 local time, a Piper PA-31-350 registered N3BT, operated by Ameriflight, Inc., was involved in an accident near Portland, Oregon, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

14 October 2008 at 15:05

Classification

Accident

Location

Portland, Oregon, United States

Nearest airport

Portland (PDX)

Coordinates

45.5306, -122.6791

Aircraft

Piper PA-31-350

Registration

N3BT

Category

Airplane

Engines

2

Operator

Ameriflight, Inc.

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

Portland → Pendleton

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR09LA013

Nobody was injured.

An in-flight engine fire due to the fatigue fracture of an exhaust pipe that resulted from a failure of the pipe's slip joint.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The pilot reported that shortly after departure, and about 1,000 feet above ground level, she noticed that the left engine’s manifold pressure dropped about 6 inches below the right engine’s indications. The engine was surging, and she thought that the turbocharger had stopped operating. The left cylinder head temperature was reading 0 degrees, but all other gauges were normal. No smoke or flames were noticed as the pilot returned to the airport for landing without declaring an emergency or shutting down the engine. During taxi to the ramp, the engine lost power. Postflight examination revealed a broken exhaust pipe on the right side of the exhaust system, with evidence of a fire in the accessory section and a burned-through section of skin. Metallurgical examination disclosed that the aft exhaust pipe flange had cracked and fractured due to fatigue. Dimensional measurements of the flange wall thickness were within design limits. The hardness was as expected for the specified type 321 steel, indicating that bending stresses acting on the flange exceeded its design capability. The cracking occurred due to excessive stresses that developed from thermal expansion of the exhaust line and insufficient sliding action at the slip joints within the exhaust pipe system. Bending of the flange and subsequent fatigue cracking indicated that the slip joints had likely not been working properly for some time.

Quoted verbatim from the NTSB record.