Overview
On April 26, 2018, at approximately 1620 Pacific daylight time, a Yakovlev Yak-52, registration N2YK, experienced a loss of engine power and subsequently made an off-airport landing about 3 miles south of Portland-Hillsboro Airport (HIO) in Hillsboro, Oregon. The airplane sustained substantial damage. The airline transport pilot and a pilot-rated passenger suffered serious injuries. The airplane was operated by Classic Aircraft Aviation Museum Inc. under Title 14 Code of Federal Regulations Part 91 as a positioning/ferry flight. Visual meteorological conditions prevailed, and no flight plan was filed for the cross-country flight, which originated from Hobby Field (77S) in Creswell, Oregon, about 1530, with an intended destination of Scappoose Industrial Airpark (SPB) in Scappoose, Oregon.
Flight Sequence
A witness pilot flying in formation with the accident airplane reported that the flight was abeam Corvallis Airport at 4,500 ft mean sea level (msl) when the accident pilot informed him the engine was "starting to miss." The witness asked about intentions, and the accident pilot replied he would continue to Hillsboro. As the flight passed south of McMinnville Airport (MMV), the accident pilot stated he might need to declare an emergency but did not specify the nature. The witness repeatedly advised landing at MMV but received no response. The accident airplane began a moderate descent from 4,500 ft msl, passed the witness on the right, and continued toward HIO. The witness transmitted position reports of nearby airports, to no response. Shortly after, the accident pilot inquired about the witness's location, who responded he was in the 5 o'clock position, high, and one mile in trail. The witness believed the airplane would crash into a mountain ridge as it continued descending. East of Yamhill, Oregon, the airplane turned left, paralleling the ridge on a northwesterly heading at an estimated 150–200 ft agl. The witness again asked intentions without response. The airplane then turned to a northeasterly heading, and shortly after, turned right, passed under the witness's wing, and impacted trees about 3 miles southwest of HIO. The witness noted that from the initial engine issue to the accident, they overflew six airports considered suitable for an emergency landing.
Passenger Account
The passenger, a rated pilot and mechanic, recalled arriving at 77S, where the airplane was already out of the hangar. After a preflight with the pilot, he signed the special flight permit to later add it to the airframe logbook upon arrival at SPB. The engine start and taxi were normal. They took off and climbed to about 3,000 or 4,000 ft in loose formation with another airplane. The passenger flew for a while before handing control to the pilot. Sometime after, the engine began to sputter, and the pilot stated they would not go to SPB but would head to Hillsboro. The passenger recalled the impact with trees.
Wreckage Examination
Examination by a Federal Aviation Administration (FAA) inspector revealed structural damage to the fuselage and left wing. The airplane was recovered for further examination. National Transportation Safety Board (NTSB) and FAA representatives found that both wings had been separated from the airframe for transport. Flight control continuity was established to all primary controls; aileron separations were due to removal and impact damage. Cockpit examination showed the landing gear lever was "up," magnetos "off," cowl flaps open, oil cooler half door open, lock lever mid span, carburetor heat off, fire valve midway, throttle full forward, propeller pitch about 1 inch forward of the aft stop, lock lever full aft, primer in and locked, ventilation control lever full aft. Continuity of throttle, mixture, and propeller controls was established to the engine.
Engine and Component Examination
The engine remained attached via mounts; all fuel and oil lines were secure. Intake and exhaust systems were impact damaged, with no evidence of pre-existing exhaust leaks. Spark plugs No. 8 and No. 3 (front) were impact damaged. The propeller remained attached; one blade separated at the hub, the other fractured mid-span. Front spark plugs showed varied deposits: Nos. 1, 8, 9 had black deposits; Nos. 7 and 3 were impact damaged; Nos. 6, 5, 4, 2 were oil soaked. Rotational continuity of the crankshaft and valve train was established; all pushrods moved equally. Accessory gears rotated accordingly. Fuel vents were clear; the airframe fuel filter contained liquid consistent with 100 low lead fuel, and the screen was debris-free. Both wing fuel tanks were breached. The carburetor, engine-driven fuel pump, and both magnetos were removed for examination at M14 Inc. in Kingman, Arizona. The magnetos were within specifications and produced spark; after heating to 225°F, they operated normally for 15 minutes. The fuel pump functioned normally. The carburetor showed no pre-existing anomalies upon disassembly and visual inspection.