FTW93LA272

NTSB accident investigation · Coen Benson B8 · Aurora, CO · September 3, 1993

Accident · FatalLimited investigationFinal report
Date
September 3, 1993, 16:27 local (23:27 UTC)
Place
Aurora, CO
Injuries
1 fatal
Damage
Destroyed
Phase of flight
Enroute
Aircraft
UNREGCoen Benson B8
Weather
Visual (VMC) · Day
Status
Completed · report August 1, 1994
Report
Approved by Office Director
Case key
18841

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

On this page

Probable cause

Fatigue failure of the center engine mount that altered the thrust and lift vectors.

Sequence of events

NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.

Loss of control - in flightCruise - normal
Engine assembly,mount - failure,totalCause
Engine assembly,mount - fatigue
Aircraft control - not possiblePilot in command
In flight collision with terrain/waterDescent - uncontrolled
Terrain condition - open field

Analysis

The aircraft was seen flying between 300 and 400 feet above the ground when, according to a witness, it suddenly 'rolled right, nearly inverted, and descended approximately 80 degrees nose down.' Several deep gouges and a scrape mark were noted atop the engine crankcase, directly beneath the center engine mounting bolt. The engine mount was fractured. This fracture, according to a metallurgist, was due to fatigue. The remaining fractures were due to overload. There was no evidence of flight control malfunction or failure.

Factual narrative

On September 3, 1993, approximately 1627 mountain daylight time, an unregistered Coen's Benson B8 impacted terrain in Aurora, Colorado. The pilot was fatally injured and the aircraft was destroyed. Visual meteorological conditions prevailed at the time, and no flight plan was filed for the personal flight.

A motorist saw the gyroplane flying at an altitude between 300 and 400 feet. He said the aircraft suddenly "rolled right, nearly inverted, and descended at approximately 80 degrees nose down." A Federal Aviation Administration inspector who went to the accident site reported all components of the aircraft were recovered, and noted the main rotor blades were bowed "conically."

Examination of the wreckage revealed several deep gouges and a scrape mark atop the engine crankcase, directly beneath the center engine mounting bolt. The engine mount was fractured. According to a University of Denver metallurgist, it appeared this fracture was due to fatigue. The remaining fractures were the result of overload. No evidence of flight control malfunction or failure was found.

Aircraft

Registration
UNREG
Reported as
Coen Benson B8
Category
Gyroplane, amateur-built
Engine
Mcculloch 4318, 90 horsepower, reciprocating
Damage
Destroyed
Flight
Personal · Part 91
Registered owner
Coen, Gary D.
Airworthiness certificate
Special, Experimental (Special)
Last inspection
Unknown · September 3, 1993
Departed
FTG · Watkins, CO

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
57
Certificate
Student
Medical
Class 3, Expired
Seat
Front
Toxicology
Performed
Flight hours
90 total

Weather

Conditions
Visual (VMC) · Day
Visibility
50 statute miles
Lowest ceiling
None