Overall Trends
Total, fatal, and serious accidents in the selected range.
Premium research interface
The modern interface for aviation safety intelligence.
Search investigations, review source evidence, monitor watched reports, and trace long-term patterns from one calm, data-first workspace.
63k+
Reports indexed
1940-2026
Coverage
Recent
Last data refresh
Search everything
Fast key and full-text search with live filters, watches, and precise metadata.
Use quotes for exact phrase matches (for example "fuel selector valve").
Featured Report
Safety trends by operating rule
Track fatal and non-fatal accident patterns across Part 91, Part 135, and Part 121 operations.
Loading trend charts…
High-signal investigations
Major cases, deep-report coverage, and investigation media across decades of NTSB history.
Browse the aviation graph
Move quickly by aircraft, airport, operator, and time with indexes built for research, not wandering.
Last Data Update
By Decade
By Month
Aircraft Manufacturer
More manufacturersAirports
More airportsOperators
More operatorsAbout
Aviation safety reports, made easier to study
NTSB Reports is an independent research and search tool for public aviation accident and incident records. It brings NTSB aviation reports, structured fields, docket files, extracted figures, photos, videos, and update history into one searchable interface.
The goal is practical safety education: make it faster to find relevant investigations, compare similar events, review factual records, and understand the evidence behind probable-cause and preliminary reports.
The investigative work and source records belong to the National Transportation Safety Board and the published investigation record. This site is not affiliated with or endorsed by the NTSB.
FAQs
NTSB Report
August 1, 1990 · Bell 47G-3B-1 · N34691
Hanson, MA
Overview
Report Status
Probable Cause
Event Type
Accident
Date
August 1, 1990
Injury Outcomes
No injuries (1 uninjured)
Location
Hanson, MA
Aircraft
Bell 47G-3B-1
Tail Number
N34691
Operator
Firefly
Injuries
None
Aircraft Damage
Substantial
NTSB Number
NYC90DNA04
THE PILOT STATED THAT WHILE HE WAS OPERATING THE HELICOPTER AT 100 FEET ABOVE THE GROUND IN AERIAL APPLICATION ACTIVITIES, THERE WAS A LOSS OF TAIL ROTOR CONTROL. THE HELICOPTER ENTERED A 'SLOW SPIN' AND DESCENDED INTO THE GROUND. POST-ACCIDENT INVESTIGATION REVEALED THAT THE TAIL ROTOR DRIVE SHAFT WAS 'SHEARED OFF' BETWEEN THE NUMBER 5 AND NUMBER 6 BEARINGS.
NTSB Probable Cause
THE PILOT'S LOSS OF CONTROL OF THE HELICOPTER DUE TO THE FAILURE OF THE TAIL ROTOR DRIVE SHAFT.
Full Narrative
THE PILOT STATED THAT WHILE HE WAS OPERATING THE HELICOPTER AT 100 FEET ABOVE THE GROUND IN AERIAL APPLICATION ACTIVITIES, THERE WAS A LOSS OF TAIL ROTOR CONTROL. THE HELICOPTER ENTERED A 'SLOW SPIN' AND DESCENDED INTO THE GROUND. POST-ACCIDENT INVESTIGATION REVEALED THAT THE TAIL ROTOR DRIVE SHAFT WAS 'SHEARED OFF' BETWEEN THE NUMBER 5 AND NUMBER 6 BEARINGS.
Flight
Event TypeAccident
Event Time07:30 EDT
Nearest Airport0nm N
Runway0
Flight Plan FiledNone
Aircraft FireNo
Aircraft ExplosionNo
Aircraft
AircraftBell 47G-3B-1
Tail NumberN34691
Aircraft CategoryHeli
DamageSubstantial
OperatorFirefly
Operating RulePart 137
Engines1
Engine TypeReciprocating
Engine DetailsLycoming · TV0-435-B1A · Reciprocating · 260
Seats3
People & Injuries
Injury SummaryNo injuries (1 uninjured)
Fatal0
Serious0
Minor0
Uninjured1
Total1
Crew 1Age 32 · Second Class
Conditions
ConditionsVMC
LightDaylight
Wind350° @ 3 kt
CeilingNone
Temperature / Dew Point0 C
Altimeter30.00 inHg
Weather SourcePILO