# NTSB MIA91LA113: Bell UH-1B, N9687R, Vero Beach, FL, March 12, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: March 12, 1991, 09:00 local (14:00 UTC)
- Place: Vero Beach, FL
- Coordinates: 27.720767, -80.390823 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=27.7208&lon=-80.3908&mi=10
- Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 1 minor
- Status: Completed, report January 25, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 32844
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=MIA91LA113
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/32844/pdf
- Page: https://openairdocs.org/ntsb/MIA91LA113

## Probable cause

IMPROPER MAINTENANCE ADJUSTMENT BY COMPANY MAINTENANCE PERSONNEL RESULTING IN OVERTORQUE OF A TAILBOOM ATTACH BOLT WHICH ALLOWED THE TAILBOOM TO SHIFT.  THIS DISENGAGED THE TAIL ROTOR DRIVE SHAFT AT A COUPLING RESULTING IN THE LOSS OF TAIL ROTOR DRIVE.

## Sequence of events

In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf).

- Airframe/component/system failure/malfunction, takeoff - initial climb
  - misc rotorcraft,tail boom - overtorque (cause)
  - maintenance,adjustment - improper, company maintenance personnel (cause)
  - misc rotorcraft,tail boom - stripped thread
  - rotor drive system,tail rotor drive shaft coupling - disengaged (cause)
- Loss of control - in flight, takeoff - initial climb
  - emergency procedure - initiated, pilot in command
- Hard landing, descent - emergency
  - object - tree(s)
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - ground

## Analysis

SHORTLY AFTER TAKEOFF AT 40 FT AGL, THE PLT STATED THAT HE OBSERVED THE HIGH/LOW ROTOR/ENG WARNING LIGHT WAS ILLUMINATED & THE HELICOPTER ENTERED AN UNCOMMANDED RT YAW.  HE ENTERED AN AUTOROTATION & WHILE DESCENDING, THE MAIN ROTOR BLADES CONTACTED TREES. HE PULLED COLLECTIVE PITCH BEFORE IMPACT WITH TERRAIN. EXAM OF THE HELICOPTER REVEALED THAT THE UPPER RT TAILBOOM ATTACH BOLT WAS STRIPPED WHICH ALLOWED THE TAILBOOM TO SHIFT RESULTING IN THE SEPARATION OF THE NOS. 1 & 2 TAIL ROTOR DRIVE SHAFT SECTIONS AT THE COUPLING.  EXAM OF THE STRIPPED BOLT BY A QUALIFIED INDIVIDUAL REVEALED THAT IT FAILED DUE TO BEING OVERTORQUED.  THE COMPANY MECHANIC STATED THAT THE TAILBOOM ATTACH BOLTS ARE CHECKED FOR PROPER TORQUE EVERY 100 HRS & WAS LAST ACCOMPLISHED ABOUT 55 HRS EARLIER.

## Aircraft

- Registration: [N9687R](https://openairdocs.org/deregistered/N9687R-2017-06-30), registration cancelled 2017-06-30, S/N 62-12529 (OpenAirDocs)
- Reported make and model: BELL UH-1B
- Registry model: [Bell UH-1B](https://openairdocs.org/model/bell-uh-1b) (registry code 1181410) (OpenAirDocs)
- Category: Helicopter
- Serial number: 62-12529
- Airframe hours: 7047
- Engines: LYCOMING T53L11D 1100 horsepower turbo shaft
- Damage: Substantial damage
- Flight: Aerial application, Part 137
- Operator: Colony Services, Inc.
- Registered owner: Colony Services, Inc.
- Last inspection: 100 hour, August 28, 1990, 55 hours before
- Airport: NONE, Unknown

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 47; commercial, airline transport; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 1, valid medical--no waivers/lim.; flight hours: 5,120 total, 1,420 in this make and model, 4,650 as pilot in command, 60 in the last 90 days, 60 in the last 30 days, 6 in the last 24 hours

## Weather

- Conditions: Visual (VMC), Day
- Wind: calm
- Visibility: 10 statute miles
- Lowest ceiling: none
- Temperature: 61 °F, dew point 46 °F
- Altimeter: 30.00 inHg
- Observed at: VRB, 5 nm away

## FAA reports on this event (1)

The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs).

- [Accident 19910312021829A](https://openairdocs.org/incident/19910312021829A), Mar 12, 1991: Bell UH1B, Vero Beach, FL, Substantial damage. Loud noise and right yaw. Autorotated into trees. Tail boom attach bolt stripped. Boom shifted. Uncoupled shaft.

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

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