# NTSB DEN91FA072: Beech C23, N6AL, Boulder, CO, May 18, 1991

- Type: NTSB accident investigation
- Classification: Accident · Serious injuries · Field investigation · Final report
- Date: May 18, 1991, 10:50 local (16:50 UTC)
- Place: Boulder, CO
- Coordinates: 40.020809, -105.249855 (estimated)
- Nearby events: https://openairdocs.org/map.md?lat=40.0208&lon=-105.2499&mi=10
- Phase of flight: [Approach](https://openairdocs.org/ntsb-phases/500) (OpenAirDocs' grouping)
- Highest injury: Serious injuries
- Injuries: 2 serious, 1 minor
- Status: Completed, report April 8, 1993
- Report: Approved by Office Director
- NTSB case key (mKey): 18024
- NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=DEN91FA072
- NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/18024/pdf
- Page: https://openairdocs.org/ntsb/DEN91FA072

## Probable cause

INADVERTENT STALL/MUSH DUE TO THE PASSENGERS'S DELAY IN RELINQUISHING AIRCRAFT CONTROL, AND INADEQUATE SUPERVISION OF THE FLIGHT BY THE PILOT IN COMMAND.  FACTORS WERE:  MIXTURE NOT LEANED, AND A HIGH DENSITY ALTITUDE TAKEOFF WITH A SLIGHT QUARTERING TAILWIND.

## Sequence of events

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

- Forced landing, approach - vfr pattern - downwind
  - weather condition - high density altitude (contributing factor)
  - mixture - not used, pilot in command (contributing factor)
  - weather condition - tailwind (contributing factor)
  - aircraft control - performed, passenger
  - supervision - inadequate, pilot in command (cause)
  - relinquishing of control - delayed, passenger (cause)
  - stall/mush - inadvertent, passenger (cause)
- In flight collision with terrain/water, descent - uncontrolled
  - terrain condition - ground
  - terrain condition - open field

## Analysis

THE REAR SEAT PASSENGER SAID THE INSTRUCTOR LET THE FRONT SEAT PASSENGER MAKE THE TAKEOFF AND 'TALKED' HIM THROUGH THE PROCEDURE.  SHORTLY AFTER LIFT OFF, BOTH PASSENGERS HEARD A 'WARNING BUZZER' SOUND THAT CONTINUED UNTIL GROUND IMPACT. THE INSTRUCTOR WAS SERIOUSLY INJURED AND COULD NOT RECALL ANY DETAILS OF THE ACCIDENT.

## Aircraft

- Registration: [N6AL](https://openairdocs.org/deregistered/N6AL-1994-03-17), registration cancelled 1994-03-17, S/N M1421 (OpenAirDocs)
- Reported make and model: BEECH C23
- Registry model: [Beech C23](https://openairdocs.org/model/beech-c23) (registry code 1151242) (OpenAirDocs)
- Category: Airplane
- Serial number: M-1421
- Airframe hours: 2756
- Engines: LYCOMING O-360-A4G 180 horsepower reciprocating
- Damage: Substantial damage
- Flight: Business, Part 91
- Operator: Dakota Ridge Aviation, Inc.
- Registered owner: Dakota Ridge Aviation, Inc.
- Airworthiness certificate: Standard, Normal; Standard, Utility
- Last inspection: Annual, March 7, 1991, 68 hours before
- Airport: IV5, Boulder Municipal, runway 26, 4,100 × 75 ft, asphalt

## Flight crew

As NTSB recorded them. NTSB leaves out names.

- Pilot; age 23; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, valid medical--no waivers/lim.; seat: left; flight hours: 767 total, 2 in this make and model, 682 as pilot in command, 61 in the last 90 days, 20 in the last 30 days

## Weather

- Conditions: Visual (VMC), Day
- Wind: 130° at 7 knots
- Visibility: 25 statute miles
- Lowest ceiling: 1,200 ft broken
- Temperature: 63 °F, dew point 45 °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 19910518016499A](https://openairdocs.org/incident/19910518016499A), May 18, 1991: Beech C23, Boulder, CO, Substantial damage. Demo flight allowed passenger to make takeoff. Stall horn on steep bank. CFI unable regain control. Stalled,crashed

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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