Air Tractor AT-401 N1012T

Summary

On 16 August 2011 at about 15:00 local time, a Air Tractor AT-401 registered N1012T was involved in an accident near Hardin, Montana, 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

16 August 2011 at 15:00

Classification

Accident

Location

Hardin, Montana, United States

Coordinates

45.7333, -107.6167

Aircraft

Air Tractor AT-401

Registration

N1012T

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Hardin → Hardin

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR11LA386

Nobody was injured.

The loss of engine power during takeoff due to the fatigue failure of the turbine wheel blades, which resulted from inadequate maintenance and inspections.

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 takeoff for the aerial application flight, the engine quit. He did not have sufficient altitude to restart the engine, so he made a forced landing to an open field; the airplane came to rest upright, and the airframe sustained structural damage. A visual examination of the engine at the accident site revealed that the compressor section had sustained fire damage and that the turbine section had broken and missing vanes. Postaccident metallurgical examination revealed that one of the turbine wheel blades had fractured and that the fracture surfaces revealed signatures consistent with fatigue propagation and subsequent failure. About 1 year 5 months before the accident, an examination of the engine revealed excessive wear to the combustor outer liner lugs, and the engine was determined to be unserviceable. About 1 year 1 month later (about 4 months before the accident), the airplane underwent a 100-hour inspection and was returned to service in an airworthy condition. No evidence was found indicating that the engine was overhauled or replaced during the 1-year period between when it was determined to be unserviceable and when it was returned to service. The pilot reported that the airplane had undergone a 100-hour inspection 1 week before the accident, but no entries were found pertaining to the inspection in the airplane's maintenance logbooks. The engine had accrued 2,819.6 hours since major overhaul. No evidence was found indicating that the engine was inspected in accordance with the manufacturer's recommended time between overhaul inspection interval of 2,000 hours. It is likely that proper maintenance inspections would have detected the crack and wear in the engine.

Quoted verbatim from the NTSB record.