WPR19LA125

NTSB accident investigation · Stearman A75N1(PT17) · Sequim, WA · April 28, 2019

Accident · Minor injuriesClass 3 · LimitedFinal report
Date
April 28, 2019, 13:37 local (20:37 UTC)
Place
Sequim, WA
Injuries
2 minor
Damage
Substantial damage
Phase of flight
Enroute
Aircraft
N68825Stearman A75N1(PT17)
Defining event
Enroute: Loss of engine power (total)
Weather
Visual (VMC) · Day
Status
Completed
Report
Approved by Office Director
Investigation class
Class 3
NTSB office
Western Pacific Region
Parties
FAA
FAA report
20190428003559A
Case key
99341

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 total loss of engine power due to the fatigue failure of the crankshaft.

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): recip eng cyl sectionAircraft › Aircraft power plant · Fatigue/wear/corrosionBoeing A75N1(PT17): 2 casesAll aircraft: 373 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

Shortly after takeoff for a personal flight, about 1,200 ft mean sea level, the pilot observed spraying oil and light oil smoke and detected the smell of oil coupled with an engine vibration. The pilot decided to make a forced landing. The engine vibration increased, and the engine seized before landing. The forced landing resulted in substantial damage to the right wing and fuselage. Examination of the radial engine revealed a crankshaft failure due to fatigue; beach marks (also known as arrest marks) were observed in the region of the fracture surface. The maintenance records indicated that the last engine overhaul was accomplished about 15 years before the accident. Engine time since major overhaul recorded at the last annual inspection about 9 months before the accident was 143 hours.

Factual narrative

On April 28, 2019, about 1337 Pacific daylight time, a Boeing A75N1 biplane, N68825, was substantially damaged when it was involved in an accident near Sequim, Washington. The pilot sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 local personal flight. According to the pilot’s statement, he had departed from runway 27 at Jefferson County Airport (0S9), Port Townsend, Washington, to the west. About 1,200 ft mean sea level (msl), over Discovery Bay, he began to smell burning oil. He then saw spraying oil and a light oil smoke coupled with engine vibration. A return to the departure airport was not an option, so he turned left toward land and began a slight descent with full power. The pilot stated that the terrain on the shoreline was rugged and the surrounding terrain above the shoreline was densely forested. The pilot attempted to troubleshoot the engine vibration; however, there was no change, and the engine vibrations increased. The pilot stated that the windscreen, his face, and goggles were covered in oil and his forward visibility was greatly reduced. He reduced power to land on the rugged shoreline. As the pilot turned toward the beach, the engine seized, and his rate of descent increased. During the flare to land, the right main landing gear and right wing impacted the water. The airplane came to rest upright on the ground, oriented more than 90° from the direction of landing, and sustained substantial damage to the wing and fuselage. A teardown examination of the engine was performed on May 8, 2019. When the No. 3 cylinder was removed the failed crankshaft was observed. Beach marks (also known as arrest marks), consistent with fatigue failure, were observed in the region of the fracture surface. Maintenance records revealed that the airplane was powered by 220-HP Continental Motors W670-6A radial engine, serial number 16541. The most recent annual inspection was completed August 1, 2018, at a recorded tachometer reading of 555.4 hours; the tachometer reading at the time of the accident was 560 hours. Engine time since major overhaul was 143.2 hours. Maintenance records further revealed that an engine overhaul was performed on April 3, 2004, the engine was completely disassembled. All steel components were magnafluxed and all aluminum parts were zyglow-inspected.

Aircraft

Registration
N68825
Reported as
Stearman A75N1(PT17) (Undesignat)
Category
Airplane
Serial number
75-5708
Built
1942
Airframe hours
555.4
Engine
Continental W670-6A, 220 horsepower, reciprocating
Damage
Substantial damage
Flight
Personal · Part 91
Operator
Port Townsend Aero Museum
Registered owner
Port Townsend Aero Museum
Airworthiness certificate
Special, Restricted (Special)
Last inspection
Annual · August 1, 2018 · 5 hours before
Departed
0S9 · Port Townsend, WA
Destination
0S9 · Port Townsend, WA
Equipment
None

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
58
Injuries
Minor
Certificate
Airline transport
Airplane ratings
Single-engine sea, Multi-engine land, Single-engine land, Multi-engine sea
Instrument ratings
Airplane
Medical
Class 1, Without waivers/limitations
Last flight review
January 31, 2019
Seat
Rear
Restraint
4-point
Flight hours
20,000 total · 1.1 in this make and model · 19,000 as pilot in command · 225 in the last 90 days · 75 in the last 30 days · 3 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
270° at 10 knots
Observed at
NMI, 20 nm away

Docket · 3

The files NTSB released with the investigation on December 15, 2021, on NTSB’s docket system: statements, records, photos and specialists’ reports. 10.0 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.