FTW98LA144 · Bell 47D1
Bell 47D1 · Accident: airframe, component or system failure on approach
From No airport to an unrecorded destination
Event
- NTSB case
- FTW98LA144
- 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
Bell 47D1
- Aircraft type
- Bell 47
- 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
- N13012
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From No airportTo 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
- Approach · VFR pattern final
- 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
- Miscellaneous, bolt/nut/fastener/clamp/spring › Separation
- Rotorcraft flight control, rotating scissors › Disconnected
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The dual student pilot was practicing landings in the local practice area, and had completed 4 to 5 landings. On the next landing, they were heading west, level at 350 feet agl, with an airspeed of 35 mph. As the student lowered the collective to initiate a steep approach, a severe vertical vibration was encountered. About 2 to 3 seconds later, a severe lateral vibration began. The flight instructor took the controls and continued the descent towards the landing area. At about 10 feet the instructor tried to reduce forward airspeed and descent rate by moving the cyclic aft and raising the collective. 'Neither of those inputs seemed to help a lot and we impacted hard.' The helicopter rolled over to the left before coming to rest heading to the east. There were no reported problems with tail rotor control. Examination of the helicopter by the FAA inspector revealed that the scissor hinge bolt which attaches the scissor to the swash plate was missing. He added that according to the maintenance records, the 5, 258 helicopter, underwent a 100 hour inspection on February 15, 1998, approximately 20 hours prior to the accident.
Probable cause
The in-flight disconnect of the rotating scissors due to the separation of its hinge bolt.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record FTW98LA144
- Event ID
- 20001211X09668
- Case number
- FTW98LA144
- 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: d63b403ae963928c6c42ed62868d29838c0052d709f398f74c57445dbb09b0cb; retrieved 2026-09-21T20:54:18.396Z.