# NTSB DEN91LA096: Bell 47G-3B-1, N40DP, Colorado Spring, CO, July 4, 1991

- Type: NTSB accident investigation
- Classification: Accident · No injuries · Limited investigation · Final report
- Date: July 4, 1991, 10:40 local (16:40 UTC)
- Place: Colorado Spring, CO
- Coordinates: 38.829154, -104.809951 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=38.8292&lon=-104.8100&mi=10
- Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping)
- Highest injury: No injuries
- Injuries: 2 uninjured
- Status: Completed, report May 5, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 18110
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN91LA096
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18110/pdf
- Page: https://openairdocs.org/ntsb/DEN91LA096

## Probable cause

THE PILOT ATTEMPTING TO OPERATE THE HELICOPTER OUTSIDE THE DESIGN OPERATING ENVELOPE.  FACTORS WERE:  HIGH ALTITUDE, HIGH TEMPERATURE, AND HIGH DENSITY ALTITUDE.

## Sequence of events

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

- Forced landing, takeoff
  - terrain condition - rough/uneven
  - altitude - dispatched, pilot in command (contributing factor)
  - weather condition - icing conditions (contributing factor)
  - performance data - not used, pilot in command (cause)
  - weather condition - high density altitude (contributing factor)
- In flight collision with terrain/water, descent - uncontrolled

## Analysis

DURING TAKEOFF FROM A HIGH ALTITUDE, HIGH DENSITY ALTITUDE HELICOPTER PAD, INSUFFICIENT POWER WAS AVAILABLE TO MAINTAIN FLIGHT OUT OF GROUND EFFECT AND THE HELICOPTER SETTLED INTO ROUGH AND UNEVEN TERRAIN.  THE MAIN ROTOR BLADES STRUCK THE TERRAIN DURING LANDING.  DENSITY ALTITUDE WAS 11,700 FEET.

## Aircraft

- Registration: [N40DP](https://openairdocs.org/deregistered/N40DP-2014-10-06), registration cancelled 2014-10-06, S/N 3763, built 1968 (OpenAirDocs)
- Reported make and model: BELL 47G-3B-1
- Registry model: [Bell 47G-3B-1](https://openairdocs.org/model/bell-47g-3b-1) (registry code 1181028) (OpenAirDocs)
- Registry engine: [Lycoming TVO-435-GIA](https://openairdocs.org/engine/lycoming-tvo-435-gia) (registry code 41526, turbo-prop) (OpenAirDocs)
- Category: Helicopter
- Serial number: 3763
- Engines: LYCOMING TVO-435V1 270 horsepower reciprocating
- Damage: Substantial damage
- Flight: Part 135
- Operator: Helitech, Inc.

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 42; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; flight hours: 3,300 total, 500 in this make and model, 29,023 as pilot in command

## Weather

- Conditions: Visual (VMC), Day
- Wind: 270° at 3 knots
- Visibility: 65 statute miles
- Lowest ceiling: none
- Temperature: 81 °F, dew point 34 °F
- Altimeter: 30.00 inHg

## 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 19910704025849A](https://openairdocs.org/incident/19910704025849A), Jul 4, 1991: Bell 47G3B1, Colorado Spring, CO, Substantial damage. Unable to climbout above trees after takeoff. Aborted. Landed in rough ground. Density altitude was 11700 feet.

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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