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 manufacturers

Airports

More airports

Operators

More operators

About

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

Statistics

Moderator preview for long-term trend segmentation and comparisons.

MCP API Docs

Model Context Protocol setup, tools, and examples with full site integration.

Loading MCP docs…

NTSB Reports for iPhone

Bring investigation work into a native iOS workflow.

Open canonical report links inside the app, keep saved activity synced, and move through media, dockets, findings, and watchlists with native speed.

Free on the App Store iOS 17+ Push alerts

Download on the App Store

Native search, saved reports, search alerts, in-app docket PDFs, inline figures, and media-first report detail.

App Store screenshot showing a report detail page with photos, overview tabs, and a formatted summary. — Report Detail **Open a full case instantly.** Move through overview, summary, media, and structured report detail in one native flow.

App Store screenshot showing the search and browse feed with recent accident reports. — Search + Browse **Find cases with less friction.** Search by tail, operator, airport, or browse recent reports from a native feed.

App Store screenshot showing docket documents inside a report detail view. — Docket Files **Read attachments in-app.** Open PDFs, statements, data files, and supporting records without leaving the case.

App Store screenshot showing the accident media viewer with investigation video. — Photos + Video **Review investigation media natively.** Swipe through extracted images and video in a full-screen viewer built for mobile reading.

App Store screenshot showing inline figures embedded inside a report narrative. — Inline Figures **See report visuals in context.** Embedded charts and figure callouts stay inside the narrative instead of feeling bolted on.

Alerts

Manage watched reports, watched searches, and notification preferences for your account.

Loading alerts…

Admin Console

Operational visibility for users, API health, and database statistics.

Loading admin tools…

NTSB Report

April 3, 1987 · Hiller UH-12ET · N135HA

Big Lake, MN

Overview

Report Status

Preliminary report

Event Type

Accident

Date

April 3, 1987

Injury Outcomes

No injuries (2 uninjured)

Location

Big Lake, MN

Aircraft

Hiller UH-12ET

Tail Number

N135HA

Injuries

None

Aircraft Damage

Substantial

NTSB Number

CHI87DER03

AIRCRAFT WAS BEING MANEUVERED FOR LANDING ON A GROUND SUPPORT TRAILER WHEN IT EXPERIENCED A POWER FAILURE. DUE TO HIGH TREES AUTOROTATION WAS MADE TO ADJACENT FIELD. AIRCRAFT LANDED ON ROUGH/UNEVEN TERRAIN AND ROLLED OVER. INVESTIGATION REVEALED CONTAMINATED FUEL SYSTEM. APPROXIMATELY ONE GALLON OF A WHITE MILKY SUBSTANCE WAS DRAINED FROM THE SUMP AND ALL MAJOR COMPONENTS OF THE FUEL SYSTEM WERE CONTAMINATED. THE ORIGIN OF THE CONTAMINATION COULD NOT BE DETERMINED.

Full Narrative

AIRCRAFT WAS BEING MANEUVERED FOR LANDING ON A GROUND SUPPORT TRAILER WHEN IT EXPERIENCED A POWER FAILURE. DUE TO HIGH TREES AUTOROTATION WAS MADE TO ADJACENT FIELD. AIRCRAFT LANDED ON ROUGH/UNEVEN TERRAIN AND ROLLED OVER. INVESTIGATION REVEALED CONTAMINATED FUEL SYSTEM. APPROXIMATELY ONE GALLON OF A WHITE MILKY SUBSTANCE WAS DRAINED FROM THE SUMP AND ALL MAJOR COMPONENTS OF THE FUEL SYSTEM WERE CONTAMINATED. THE ORIGIN OF THE CONTAMINATION COULD NOT BE DETERMINED.

Flight

Event TypeAccident

Event Time15:40 CST

Nearest Airport0nm N

Runway0

Runway Length0

Runway Width0

Flight Plan FiledNone

Aircraft FireNo

Aircraft ExplosionNo

Aircraft

AircraftHiller UH-12ET

Tail NumberN135HA

Aircraft CategoryHeli

DamageSubstantial

Operating RulePart 91

Engines1

Engine TypeTurboshaft

Engine DetailsAllison · 250-C20B · Turboshaft · 400

Seats3

People & Injuries

Injury SummaryNo injuries (2 uninjured)

Fatal0

Serious0

Minor0

Uninjured2

Total2

Crew 1Age 29 · Second Class

Conditions

ConditionsVMC

LightDaylight

WindCalm

Visibility20 sm

CeilingNone

Temperature / Dew Point50 / 0 C

Altimeter0

Weather SourcePILO

500 – Data service is offline

The modern interface for aviation safety intelligence.

Your saved activity

Saved Reports

Saved Searches

Search everything

Loading…

Safety trends by operating rule

High-signal investigations

Browse the aviation graph

Last Data Update

By Decade

By Month

Aircraft Manufacturer

Airports

Operators

About

Aviation safety reports, made easier to study

FAQs

April 3, 1987 · Hiller UH-12ET · N135HA

Overview

Accident Location

NTSB Probable Cause

Full Narrative View original narrative

Key Findings (Experimental AI)

Recent Report Updates

Photos and Videos

Selected image

Flight

Aircraft

People & Injuries

Conditions

Related investigations

NTSB Docket Documents

Document

Additional Resources

See Also

External Links

Appendix: Source Data

Full Narrative