CEN10CA376

NTSB accident investigation · Wells Terry Hula Girl · Wellington, CO · July 3, 2010

Accident · No injuriesData collectionFinal report
Date
July 3, 2010, 12:00 local (18:00 UTC)
Place
Wellington, CO
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Takeoff
Aircraft
N301TWWells Terry Hula Girl
Defining event
Takeoff: Loss of engine power (partial)
Weather
Visual (VMC) · Day
Status
Completed · report October 21, 2010
Report
Approved by Office Director
NTSB office
Central Region
Parties
FAA Denver FSDO
FAA report
20100703038609A
Case key
76556

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

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Probable cause

A partial loss of engine power due to the inadequate design of the engine cowling.

Findings · 1

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Engine (reciprocating)Aircraft › Aircraft power plant · DesignWells Terry HULA GIRL: 1 caseAll aircraft: 497 casesProbable cause

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

The pilot, who is also the designer and builder of the experimental motorglider, was making his second flight after having completed a number of high-speed taxi tests. The pilot said that several months earlier, on his first flight in the motorglider, shortly after becoming airborne the engine experienced a partial loss of power and he landed immediately. On the accident flight, immediately after takeoff, the pusher-configuration engine again lost power from 6,500 rpm to approximately 4,300 rpm. The pilot was not able to climb and was able to maintain flight at only 100 feet above ground level. Approximately one mile from the airport the pilot attempted an off-field emergency landing and then “did an intentional ground loop” to avoid a fence he had not noticed before touchdown. With the motorglider then moving sideways, the tail impacted a small tree. The carbon-fiber tail boom fractured and separated just forward of the vertical fin, causing substantial damage to the motorglider. The solo pilot was not injured. The pilot reported that there was adequate fuel in the tank and previous testing showed there was adequate fuel flow to the engine. After the accident the pilot reported that that his design of the engine cowling needed to be modified and he thought that “an engine compartment pressure differential from outside air caused the carburetor float bowl to empty.”

Factual narrative

The pilot, who is also the designer and builder of the experimental motorglider, was making his second flight after having completed a number of high-speed taxi tests. The pilot said that several months earlier, on his first flight in the motorglider, shortly after becoming airborne the engine experienced a partial loss of power and he landed immediately. On the accident flight, immediately after takeoff, the pusher-configuration engine again lost power from 6,500 rpm to approximately 4,300 rpm. The pilot was not able to climb and was able to maintain flight at only 100 feet above ground level. Approximately one mile from the airport the pilot attempted an off-field emergency landing and then “did an intentional ground loop” to avoid a fence he had not noticed before touchdown. With the motorglider then moving sideways, the tail impacted a small tree. The carbon-fiber tail boom fractured and separated just forward of the vertical fin, causing substantial damage to the motorglider. The solo pilot was not injured. The pilot reported that there was adequate fuel in the tank and previous testing showed there was adequate fuel flow to the engine. After the accident the pilot reported that that his design of the engine cowling needed to be modified and he thought that “an engine compartment pressure differential from outside air caused the carburetor float bowl to empty.”

Aircraft

Registration
N301TW
Reported as
Wells Terry Hula Girl
Category
Glider, amateur-built
Serial number
001
Airframe hours
1
Engine
Rotax 447 ULS, 40 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Airworthiness certificate
Special, Experimental (Special)
Last inspection
Condition · February 27, 2010 · 1 hours before
Departed
4CO2 · Wellington, CO
Destination
4CO2 · Wellington, CO
Airport
4CO2 · Owl Canyon Gliderport, runway 19R, 3,580 × 24 ft, grass/turf

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
63
Injuries
None
Certificate
Private
Airplane ratings
Single-engine land
Last flight review
June 27, 2010
Seat
Single
Flight hours
247 total · 1 in this make and model · 200 as pilot in command

Weather

Conditions
Visual (VMC) · Day
Wind
130° at 11 knots, gusting 15
Visibility
10 statute miles
Temperature
91 °F, dew point 52 °F
Altimeter
29.77 inHg
Observed at
FNL, 21 nm away

Docket · 1

The files NTSB released with the investigation on July 27, 2010, on NTSB’s docket system: statements, records, photos and specialists’ reports. 446 KB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.