Weatherly 620B N9004M

Summary

On 10 April 2017 at about 23:00 local time, a Weatherly 620B registered N9004M, operated by Skyline Aviation LLC, was involved in an accident near Lewistown, 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

10 April 2017 at 23:00

Classification

Accident

Location

Lewistown, Montana, United States

Nearest airport

Lewistown Muni (LWT)

Coordinates

47.0336, -109.4633

Aircraft

Weatherly 620B

Registration

N9004M

Category

Airplane

Year built

1995

Engines

1

Operator

Skyline Aviation LLC

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Lewistown → Lewistown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

GAA17CA225

Nobody was injured.

The pilot’s failure to maintain altitude during low-altitude maneuvers in flat light conditions.

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

Read the full NTSB narrative

The pilot reported that, during a low-altitude, practice agricultural application flight, he lost depth perception between the snow-covered ground and overcast sky. He added that the airplane impacted the ground and came to rest after sliding about 500 ft. The airplane sustained substantial damage to the right wing and fuselage. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The Federal Aviation Administration's pamphlet, "Flying in Flat Light and White Out Conditions," states the following: Flat light is an optical illusion, also known as "sector or partial white out." It is not as severe as "white out" but the condition causes pilots to lose their depth-of-field and contrast in vision. Flat light conditions are usually accompanied by overcast skies inhibiting any good visual clues. Such conditions can occur anywhere in the world, primarily in snow covered areas but can occur in dust, sand, mud flats, or on glassy water. Flat light can completely obscure features of the terrain, creating an inability to distinguish distances and closure rates. As a result of this reflected light, it can give pilots the illusion of ascending or descending when actually flying level. However, with good judgment and proper training and planning, it is possible to safely operate an aircraft in flat light conditions.

Quoted verbatim from the NTSB record.