Accident Overview
On June 14, 2012, at 1450 mountain daylight time, a Yakovlev Yak-52, registration N76YK, was substantially damaged during landing at Fort Collins-Loveland Municipal Airport (KFNL), Loveland, Colorado. The nose landing gear collapsed during the landing roll, and the airplane came to rest on the runway before a fuel fire erupted in the engine compartment. Airport firefighting and rescue personnel responded and extinguished the fire. The airline transport pilot, who was also the owner and operator, was not injured.
Flight Details
The personal flight was conducted under 14 Code of Federal Regulations Part 91 in day visual meteorological conditions without a flight plan. The aircraft departed Greeley-Weld County Airport (KGXY) at 1435, with an intended destination of KFNL.
Aircraft Damage
The engine structural supports were substantially damaged during the nose gear collapse. The forward fuselage structure sustained substantial damage from the ground fire.
Pneumatic System Description
The Yak-52 uses air pressure for landing gear extension and retraction, flap deployment, wheel braking, and engine start. The pneumatic system is activated by opening a main valve in the cockpit, which should remain open for all operations. With the valve closed, residual air downstream can operate systems until pressure depletes. Extending the nose gear requires the most air pressure force due to deploying forward into the relative wind.
Examination Findings
At the accident site, the pneumatic system valve was found closed (off), the observed air-pressure supply was about 75 percent, and the landing gear selector handle was in the down position. When the valve was opened, the nose landing gear deployed rapidly and locked into position; the gear components appeared undamaged.
Pilot Statements
The pilot reported that the pneumatic valve installed in his airplane did not have an open/closed position placard. Activation of the valve is normally identified by the aural sound of air rapidly charging the system. The cockpit air-pressure gauge indicates bottle pressure regardless of valve position.
Before the first flight of the day, the pilot opened the pneumatic system valve prior to pulling the airplane from the hangar. He verified the valve position twice before departing to KGXY. After an uneventful landing, he set the parking brake and left the valve open. Following refueling, he reentered the cockpit and believed he inadvertently closed the valve during the before engine startup checklist. With the valve closed, he started the engine, took off, and fully retracted the landing gear. On approach, he extended the landing gear by placing the handle down. Before landing, he verified gear position using mechanical barber-pole indicators, which suggested all gear were fully extended.
Mechanic's Comment
A mechanic familiar with Yak-52 airplanes stated that the mechanical barber-pole indicators, located forward of the windscreen, should not be used as the primary indication of landing gear position. They are intended to be used in conjunction with the landing gear position indicator lights.
Weather Conditions
At 1455, the airport's automated surface observing system reported wind from 080 degrees at 10 knots, gusting 17 knots; clear skies; visibility 10 miles; temperature 29°C; dew point 6°C; altimeter 29.95 inches of mercury. The surface wind direction had varied between 040 and 140 degrees since the previous hourly report.