Air Tractor AT-401 N4553K

Summary

On 27 July 2001 at about 15:00 local time, a Air Tractor AT-401 registered N4553K, operated by Willmes, Steven J, was involved in an incident near Kenesaw, Nebraska, United States. One person was on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

27 July 2001 at 15:00

Classification

Incident

Location

Kenesaw, Nebraska, United States

Coordinates

40.6099, -98.6506

Aircraft

Air Tractor AT-401

Registration

N4553K

Category

Airplane

Engines

1

Operator

Willmes, Steven J

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Roseland → Unknown

Aircraft damage

Minor

Weather

VMC

Light

Day

NTSB number

CHI01IA246

Nobody was injured.

The propeller blade fatigue leading to its tip separating during an aerial application. Factors were no suitable terrain for an emergency landing, high vegetation, and soft terrain encountered during the emergency landing.

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

Read the full NTSB narrative

The airplane sustained minor damage when it nosed over during an emergency landing following an in-flight loss of a propeller blade tip. The pilot was uninjured. The pilot stated, "While on a actual spray run the aircraft began to shake and vibrate violently. At that time I shut the power down, climbed about 100 ft to look for a place to land. The area was rolling with pasture land and a corn field in front of me, no roads to land on in the area. ... After a rolling out for a short while in corn the landing gear became stuck in corn and soft sandy soil." A portion of the remaining blade, including the separation, was shipped to the NTSB's Materials Laboratory Division. The laboratory's report stated that "a large portion of the fracture surface was on a 90-degree flat plane with multiple ratchet marks and crack arrest marks on this portion of the fracture surface. These features are typical of a fatigue crack. The fatigue crack originated from multiple origins at the bottom of a gouge on the flat face of the blade about 2.25 inches from the blade's leading edge. The fatigue crack extended through about two-thirds of the blade's cross-section. The remainder of the fracture surface (about one-third of the blade's cross section) was on a 45-degree slanted plane and was typical of an overstress region stemming from the fatigue crack." A section was saw cut from the fracture containing the fatigue origin. The paint was removed from the areas near the crack origin and the surface was re-examined with a scanning electron microscope (SEM). The gouge was measured using the SEM. The report further stated, "The length of the gouge was 0.6 inch (1.5 millimeters), and the depth of the gouge was 0.0055 inch (0.14 millimeters). ... Optical examination of the flat face of the blade near the gouge did not show any evidence of blending or rework in this area." The propeller's last overhaul was completed on January 13, 1998. The propeller accumulated 240 hours of flight since that overhaul.

Quoted verbatim from the NTSB record.