CHI05LA104 · Weatherly 620B
Weatherly 620B · Accident: loss of engine power while maneuvering
From Private to an unrecorded destination
Event
- NTSB case
- CHI05LA104
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Weatherly 620B
- Aircraft type
- Weatherly 620
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N9026F
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From PrivateTo not recorded
- Aircraft age
- Not recorded
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 137: Agricultural
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Maneuvering · aerial application
- First occurrenceThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of engine power
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Engine assembly, cylinder › Failure
- Engine assembly, cylinder › Fatigue
- Other maintenance personnel › Maintenance, inspection, not detected
Approximate · Coordinates from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
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.
Probable cause
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CHI05LA104
- Event ID
- 20050428X00519
- Case number
- CHI05LA104
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, coordinates. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: eae0400203ad3ce956e25c5f9a77936d75e838dc9711c35920c8951ccb7c096f; retrieved 2026-09-21T19:02:35.685Z.