Weatherly 620B N9026F

Summary

On 20 April 2005 at about 23:15 local time, a Weatherly 620B registered N9026F was involved in an accident near Downs, Kansas, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

20 April 2005 at 23:15

Classification

Accident

Location

Downs, Kansas, United States

Coordinates

39.8425, -98.9186

Aircraft

Weatherly 620B

Registration

N9026F

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 137: Agricultural

Purpose of flight

Aerial Application

Phase of flight

Not recorded

Route

Private → Unknown

Aircraft damage

Substantial

Weather

VMC

NTSB number

CHI05LA104

1 person had minor injuries.

The loss of engine power due to the failure of the number two cylinder which was the result of the maintenance facility's failure to detect the fatigue crack in the number two cylinder during the engine overhaul. A factor to the accident was the soft field.

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

Read the full NTSB narrative

The agricultural spray airplane sustained substantial damage during a forced landing to a farm field after a loss of engine power. The pilot reported that he was "pulling the airplane up into a right hand turn" at the end of a spray run when he heard a loud "bang" and the engine started to run "really rough." He executed a forced landing to a field. The landing gear broke off due to the soft field conditions. The engine was a 450 horsepower Pratt & Whitney R-985-14B engine. The engine was overhauled 43 hours prior to the accident. At overhaul, the engine had accumulated a total time of 7,027.1 hours. The engine logbook noted that AD 78-0807 was complied with. AD 78-0807 was effective May 2, 1978 for ultrasonic and visual inspections every 150 hours time in service to detect cracking and "to prevent cylinder head separation from the barrel." The logbook did not contain specific information on the previous histories of the installed cylinders. The inspection of the airplane revealed that the number 2 cylinder was broken at the third large cooling vent up from the bottom. The upper portion on the head assembly had separated from the sleeve. The National Transportation Safety Board's (NTSB) Materials Laboratory report noted that the fracture faces were covered by extensive and heavy combustion products and required extensive cleanings to reveal fracture details. Examinations of the fracture faces revealed features and topography indicative of a large area of fatigue progression. The fatigue area was on the aft side of the cylinder, biased toward the exhaust valve. Fracture face markings indicative of multiple fatigue initiation at the inner diameter threads along a wide arc of approximately 140 degrees. Progression was radial through the head with complete penetration over and arc of about 60 degrees centered in the fatigue region. The cylinder head was permanently marked with UT05, UT97, UT91, UT89, and UT89 stamped in the head near the intake port. The "UT" markings on the head are consistent with the markings required by AD 78-0807 and they denote five different ultrasonic inspections since 1989.

Quoted verbatim from the NTSB record.