Air Tractor AT-401 N92PK

Summary

On 6 June 2007 at about 16:00 local time, a Air Tractor AT-401 registered N92PK, operated by Whittington Air & Ground LLC, was involved in an accident near Oak Grove, Louisiana, 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

6 June 2007 at 16:00

Classification

Accident

Location

Oak Grove, Louisiana, United States

Coordinates

32.8617, -91.3894

Aircraft

Air Tractor AT-401

Registration

N92PK

Category

Airplane

Engines

1

Operator

Whittington Air & Ground LLC

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Eudora → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

DFW07LA138

Nobody was injured.

A complete loss of power due to failure of the impeller drive gear train and displacement of the blower spring drive mechanism, which resulted in seizure of the propeller shaft/crankshaft. Also causal was the failure of the phenolic separator bracket of the rear impeller support bearing for undetermined reasons. A factor was the none suitable terrain for the forced landing.

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

Read the full NTSB narrative

The 5,475-hour commercial pilot reported that after performing an aerial application pass in his radial-engine-powered airplane, he initiated a turn to reverse direction to start another pass. At the top of the turn, he heard a loud bang from the radial engine, followed by the sound of the engine winding down. He also noticed white smoke from the exhaust, a loss of power, and a drop in manifold pressure. The pilot made an forced landing to a field, where the airplane rolled about 250 yards before it flipped over. The airplane was released to the owner after the accident, who later sold it to another operator. Due to the damage sustained in the accident, the engine was disassembled and examined before the new owner could return the airplane back to service. The new owner provided an engine disassembly report. According to the report, "undetermined causes resulted in distress to the phenolic separator bracket of the rear impeller support bearing resulted in its separation and fragmentation." The reports adds that "this initiated a chain reaction of events throughout the rest of the engine as clearances, lack of lubrication and subsequent wearing of engine components took place." This damage ultimately resulted in destruction of the blower labyrinth seal and the impeller gear train, which reduced power output. The engine reports concludes that "the destroyed impeller drive gear train and the distress caused by the displaced blower spring drive mechanism, coupled with reduced power output, resulted in seizure of the propeller shaft/crankshaft and complete loss of power."

Quoted verbatim from the NTSB record.