# NTSB FTW91LA064: Bell 47G4, N1195W, Corpus Christi, TX, April 27, 1991

- Type: NTSB accident investigation
- Classification: Accident · Minor injuries · Limited investigation · Final report
- Date: April 27, 1991, 08:30 local (13:30 UTC)
- Place: Corpus Christi, TX
- Coordinates: 27.770017, -97.51979 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=27.7700&lon=-97.5198&mi=10
- Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping)
- Highest injury: Minor injuries
- Injuries: 2 minor
- Status: Completed, report March 31, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 23322
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=FTW91LA064
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/23322/pdf
- Page: https://openairdocs.org/ntsb/FTW91LA064

## Probable cause

THE INITIAL RESTRICTED MOVEMENT AND EVENTUAL LOCKING OF THE CYCLIC CONTROL AS A RESULT OF THE FAILURE OF THE LATERAL SERVO. A FACTOR WAS THE INSTALLATION OF THE FAILED COMPONENT BY AN UNQUALIFIED PERSON.

## Sequence of events

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

- Airframe/component/system failure/malfunction, maneuvering - turn to reverse direction
  - rotorcraft flight control,cyclic control - movement restricted (cause)
  - rotorcraft flight control system,primary servo - worn (cause)
  - maintenance,replacement - performed, unqualified person (contributing factor)
  - precautionary landing - initiated, pilot in command
- Loss of control - in flight, landing - flare/touchdown
  - rotorcraft flight control,cyclic control - locked (cause)
- In flight collision with object, descent - uncontrolled
  - object - tree(s)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

A COMMERCIAL PILOT WAS MANEUVERING A HELICOPTER TO CONTROL A HERD OF CATTLE. THE PILOT NOTICED AN INTERMITTENT BINDING IN THE LEFT QUADRANT OF THE CYCLIC CONTROL. HE NOTIFIED HIS FLIGHT LEADER OF HIS INTENTIONS TO LAND AND INSPECT THE HYDRAULIC SERVOS IN THE FLIGHT CONTROL SYSTEM, AND INITIATED A PRECAUTIONARY LANDING CLOSE TO THEIR MAINTENANCE SUPPORT VEHICLE. DURING THE LANDING FLARE, THE HELICOPTER PITCHED SHARPLY TO THE RIGHT REAR AS THE LATERAL CYCLIC CONTROL BECAME LOCKED. THE PILOT APPLIED FULL RIGHT PEDAL TO TRY TO CUSHION THE LANDING AND PREVENT THE HELICOPTER FROM ROLLING. THE HELICOPTER WAS DESTROYED UPON IMPACT WITH THE MESQUITE TREES. THE FAILED LATERAL SERVO HAD BEEN REPLACED BY AN UNQUALIFIED PERSON PRIOR TO THIS FLIGHT.

## Aircraft

- Registration: [N1195W](https://openairdocs.org/deregistered/N1195W-2013-11-13), registration cancelled 2013-11-13, S/N 3348, built 1965 (OpenAirDocs)
- Reported make and model: BELL 47G4
- Registry model: [Bell 47G-4](https://openairdocs.org/model/bell-47g-4) (registry code 1181030) (OpenAirDocs)
- Registry engine: [Lycoming VO-540 series](https://openairdocs.org/engine/lycoming-vo-540-series) (registry code 41534, reciprocating) (OpenAirDocs)
- Category: Helicopter
- Serial number: 3348
- Engines: LYCOMING VO-540-B1B3 280 horsepower reciprocating
- Damage: Destroyed
- Flight: Aerial observation, Part 91
- Operator: W. J. Tiller, doing business as Tiller Helicopter Services
- Registered owner: W. J. Tiller

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: helicopter, airplane; medical: class 2, valid medical--no waivers/lim.; flight hours: 2,079 total, 130 in this make and model, 2,079 as pilot in command, 106 in the last 90 days, 68 in the last 30 days, 1 in the last 24 hours

## Weather

- Conditions: Instrument (IMC), Day
- Wind: 130° at 12 knots
- Visibility: 2 statute miles
- Lowest ceiling: 900 ft overcast
- Temperature: -0 °F, dew point -0 °F

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.

---
OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.