SEA99LA020 · Garlick UH-1H
Garlick UH-1H · Accident: airframe, component or system failure while maneuvering
Event
- NTSB case
- SEA99LA020
- 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
- 0
- 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
Garlick UH-1H
- Aircraft type
- Garlick UH-1
- Category
- Helicopter
- 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
- N94NW
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 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 133: Rotorcraft Ext. Load
- 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 · hover
- 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
- Airframe, component or system failure
- 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
- Vertical stabilizer › Fatigue
- Vertical stabilizer › Fractured
- Vertical stabilizer › Separation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While in a hover during heavy-lift aero-logging operations, the vertical fin separated from the tail boom, resulting in an uncontrolled descent into the terrain. During the investigation, the NTSB Materials Laboratory determined that the separation was due to the propagation of a number of fatigue cracks which had initiated within the fourth rivet hole above where the left side of the spar fin cap protruded from the tail boom. Although the FAA had previously issued Airworthiness Directive (AD) 97-20-09 to address the separation of vertical fins from UH-1 helicopters used in repeated heavy-lift operations, the Rotorcraft Directorate determined that the AD was not adequate. As a result, the Directorate initiated the formulation of a Priority Letter Airworthiness Directive requiring the replacement of the original fin spar with one that '...has been shown to account for the effects of repeated heavy-lift operations.'
Probable cause
The total separation of the vertical fin (stabilizer), as the result of fatigue cracks which initiated in the fourth rivet hole above where the fin extends from the tailboom.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record SEA99LA020
- Event ID
- 20001211X11632
- Case number
- SEA99LA020
- 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. 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: 9e9d5b1a4c9f4ff55c23cff3b340bb187068b499d086de01880902299c132db7; retrieved 2026-09-21T11:18:02.853Z.