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NTSB accident investigation · Sorensen Danny S BF9 2 · Evanston, WY · May 31, 2018

Accident · No injuriesData collectionFinal report
Date
May 31, 2018, 17:45 local (23:45 UTC)
Place
Evanston, WY
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N81973Sorensen Danny S BF9 2
Defining event
Enroute: Fuel exhaustion
Weather
Visual (VMC) · Day
Status
Completed · report November 5, 2018
Report
Approved by Office Director
NTSB office
General Aviation Accidents
Parties
FAA
FAA report
20180531006429A
Case key
97419

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

The pilot’s failure to fuel the biplane’s main fuel tank before the flight and his inadequate preflight inspection, during which he did not verify the fuel quantity, which resulted in fuel exhaustion

Findings · 4

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.

Fluids: fuelAircraft › Fluids/misc hardware · Fluid levelSorensen Danny S BF9-2: 1 caseAll aircraft: 1,695 casesProbable cause
Planning/preparation: fuel planningPersonnel issues › Task performance · PilotSorensen Danny S BF9-2: 1 caseAll aircraft: 719 casesProbable cause
Inspection: preflight inspectionPersonnel issues › Task performance · PilotSorensen Danny S BF9-2: 1 caseAll aircraft: 551 casesProbable cause
Object/animal/substance: ground vehicleEnvironmental issues › Physical environment · Contributed to outcomeSorensen Danny S BF9-2: 1 caseAll aircraft: 132 cases

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 of the biplane reported that he believed he had departed with 38 gallons of fuel in the main fuel tank and 17 gallons in the auxiliary fuel tank. En route, the auxiliary fuel tank ran dry, so he switched to the main fuel tank, which he believed had 35 gallons of fuel remaining. The pilot reported that, while descending to the destination airport, the engine experienced a loss of power. He added that he believed the throttle linkage had broken and that the carburetor was at idle. During the forced landing, he aligned the airplane with a highway and observed four semi-tractor trailers but thought they were ahead of his flightpath. The biplane struck one of the semi-tractor trailers, violently turned right, and then came to rest inverted on the right side of the highway. The biplane sustained substantial damage to the left wings. Postaccident examination revealed that the main fuel tank was empty, and the throttle linkage was intact. The pilot reported that his typical fueling process is to fuel the main fuel tank before fueling the auxiliary fuel tank. He added that he reviewed fuel receipts and found that, before the accident flight, he fueled the auxiliary fuel tank first and, while following his routine, believed that the main fuel tank had already been fueled. This resulted in a departure with 10 gallons of fuel less than planned. The pilot reported that there were no preaccident mechanical failures or malfunctions with the biplane that would have precluded normal operation.

Factual narrative

The pilot of the biplane reported that he believed he had departed with 38 gallons of fuel in the main fuel tank and 17 gallons in the auxiliary fuel tank. En route, the auxiliary fuel tank ran dry, so he switched to the main fuel tank, which he believed had a remaining 35 gallons of fuel. The pilot reported that, while descending to the destination airport, the engine experienced a loss of power. He added that he believed the throttle linkage had broken and the carburetor was at idle. During the forced landing, he aligned the airplane with a highway and observed four semi-tractor trailers, but thought they were ahead of his flight path. The airplane struck one of the semi-tractor trailers, violently turned to the right, and came to rest inverted on the right side of the highway. The airplane sustained substantial damage to the left wings. Postaccident examination revealed that the main fuel tank was empty, and the throttle linkage was intact. The pilot reported that his habitual fueling process is to fuel the main fuel tank before fueling the auxiliary fuel tank. He added that he reviewed fuel receipts and discovered that, before the accident flight, he fueled the auxiliary fuel tank first and, while following his routine, believed that the main fuel tank had already been fueled. This resulted in a departure with 10 gallons of fuel less than planned. The pilot reported that there were no preaccident mechanical failures or malfunctions with the biplane that would have precluded normal operation.

Aircraft

Registration
N81973
Reported as
Sorensen Danny S BF9 2 (NO SERIES)
Category
Airplane, amateur-built
Serial number
24601-001
Built
2008
Airframe hours
309.8
Engine
Vendenyev M-14P, 360 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Airworthiness certificate
Special, Experimental (Special)
Last inspection
Condition · March 23, 2018
Departed
LMO · Longmont, CO
Destination
EVW · Evanston, WY
Equipment
Handheld GPS

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
68
Injuries
None
Certificate
Commercial
Airplane ratings
Single-engine land
Medical
Class 2, Without waivers/limitations
Last flight review
October 5, 2016
Seat
Rear
Flight hours
2,016 total · 310 in this make and model · 1,980 as pilot in command · 33 in the last 90 days · 12 in the last 30 days · 7 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
220° at 19 knots, gusting 25
Visibility
10 statute miles
Lowest ceiling
None
Temperature
72 °F, dew point 28 °F
Altimeter
29.82 inHg
Observed at
KEVW, 2 nm away

Docket · 2

The files NTSB released with the investigation on September 10, 2018, on NTSB’s docket system: statements, records, photos and specialists’ reports. 5.2 MB 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.