FTW84LA136 · Sikorsky S-58E
Sikorsky S-58E · Accident: airframe, component or system failure while maneuvering
Event
- NTSB case
- FTW84LA136
- 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
Sikorsky S-58E
- Aircraft type
- Sikorsky S-58
- 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
- N70709
- 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 91: General Aviation
- 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
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Tree(s)
- 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
- Rotor drive system, intermediate gearbox(42 deg) › Fatigue
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE HELICOPTER WAS HOVERING ABOVE TREES AT ABOUT 100 FT AGL WHEN THE TAIL ROTOR CHIP DETECTOR LGT FLICKERED SVRL TIMES, THEN ILLUMINATED STEADILY. THIS WAS FOLLOWED BY A LOUD GRINDING NOISE FROM THE TAIL AREA & THE ACFT YAWED TO THE RIGHT. THE ACFT ENTERED AN AUTOROTATION AFTER MAKING 3 TURNS TO THE RIGHT. IT DESCENDED INTO THE TREES AT WHICH TIME THE MAIN ROTOR BLADES WERE BROKEN OFF. AN EXAM OF THE INTERMEDIATE TAIL ROTOR GEAR BOX DISCLOSED THAT 6 TEETH IN THE INPUT BEVEL PINION GEAR, PN S1635-64114, HAD FAILED IN THE ROOT AREA. A METALLURGICAL EXAM DETERMINED THAT THE FAILURE ZONE HAD FATIGUE INDICATIONS. CRACKS WERE FOUND IN OTHER AREAS OF THE GEAR BOX. SIKORSKY ENGINEERS DETERMINED THAT THE GEAR BOX HAD BEEN SUBJECTED TO HEAVY LOADS. THE GEAR BOX HAD BEEN LAST OPENED IN 1968. ONE GEAR WAS NOT A SIKORSKY PRODUCT.
Verbatim NTSB analysis from the NTSB dataset
Sources
NTSB record FTW84LA136
- Event ID
- 20001214X38779
- Case number
- FTW84LA136
- 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: 1453baba227492fe1a495b82203f74f706c437809dc2ef00594ac8cd7271b0fa; retrieved 2026-09-21T17:41:30.566Z.