SEA98LA080

NTSB accident investigation · Air Tractor AT-401 · Idaho Falls, ID · May 20, 1998

Accident · Minor injuriesLimited investigationFinal report
Date
May 20, 1998, 09:15 local (15:15 UTC)
Place
Idaho Falls, ID
Injuries
1 minor
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N1009TAir Tractor AT-401
Weather
Visual (VMC) · Day
Status
Completed · report July 12, 2000
Report
Approved by Office Director
FAA report
19980520010249A
Case key
42789

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

The NTSB’s determination of the probable cause, and any contributing factors.

The pilot's failure to maintain clearance from a power transmission line during an aerial application flight. Factors include a power line located just beyond the boundary of the field being sprayed, and the pilot's incorrect judgement of the distance between the wire and his aircraft.

Analysis

According to the pilot, who was maneuvering near the power line while applying chemicals to a field, he had just rolled wings-level and descended for another pass when his left wing contacted the top wire of the power line. He said that he saw the line and thought he had clearance, but the aircraft's wing caught the wire near its tip. He reported that after colliding with the power line, the aircraft struck the ground in a 'cart-wheeling' motion. He further stated that he was accustomed to flying the AT-300, but that he had recently purchased the AT-401, and that this was his first application flight using the new aircraft. It was his opinion that the different size and sight-picture of the 401 had caused him to think he had more clearance from the wire than he actually had.

Factual narrative

On May 20, 1998, approximately 0915 mountain daylight time, an Air Tractor AT-401, N1009T, collided with a power transmission line during an aerial application flight about two miles northwest of Idaho Falls, Idaho. The commercial pilot, who was the sole occupant, received minor injuries, and the aircraft, which was owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 137 flight, which originated at an agricultural airstrip near Osgood, Idaho, was being operated in visual meteorological conditions.

According to the pilot, who had been maneuvering near the power line while applying chemicals to a field, he was just rolling wings-level and descending for another pass when his left wing contacted the top wire of a power line located just beyond the boundary of the field he was spraying. He said that he saw the line and thought he had clearance, but the aircraft's wing caught the wire near its tip. He reported that after colliding with the power line, the aircraft struck the ground in a "cart-wheeling" motion. He further stated that he was accustomed to flying the AT-300, but that he had recently purchased the AT-401, and that this was his first application flight using the new aircraft. It was his opinion that the different size and sight-picture of the 401 had caused him to think he had more clearance from the wire than he actually had.

Sequence of events

NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.

In flight collision with objectManeuvering
Clearance - not maintainedPilot in commandCause
Distance - misjudgedPilot in commandFactor
Object - wire,transmissionFactor

Aircraft

Registration
N1009T
Reported as
Air Tractor AT-401
Category
Airplane
Serial number
401-0707
Airframe hours
4,055
Engine
P&W 1340-AN2, 600 horsepower, reciprocating
Damage
Substantial damage
Flight
Aerial application · Part 137
Registered owner
Orlin D. Lewis
Airworthiness certificate
Special, Restricted (Special)
Last inspection
100 hour · April 21, 1998 · 9 hours before
Departed
Osgood, ID

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
53
Certificates
Commercial, Flight instructor
Airplane ratings
Single-engine land
Instrument ratings
Airplane
Medical
Class 2, Valid Medical--w/ waivers/lim
Seat
Center
Flight hours
9,882 total · 9 in this make and model · 9,761 as pilot in command · 12 in the last 90 days · 9 in the last 30 days · 4 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
50° at 7 knots
Visibility
10 statute miles
Lowest ceiling
None
Temperature
50 °F

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.

Other investigations on N1009T · 1

Matched to the same aircraft by N-number and date.