On June 14, 2012, at 1450 mountain daylight time, a Yakovlev model Yak-52, N76YK, was substantially damaged when the nose landing gear collapsed during landing roll at Fort Collins-Loveland Municipal Airport (KFNL), Loveland, Colorado. A sustained ground fire ensued after the airplane came to rest on the runway. The airline transport pilot was not injured. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the personal flight, which was operated without a flight plan. The flight departed Greeley-Weld County Airport (KGXY), Greeley, Colorado, at 1435 with the intended destination of KFNL.

The pilot reported that the nose landing gear collapsed shortly after touchdown. The airplane came to rest nose down on the runway and a fuel fire erupted in the engine compartment. Aircraft firefighting and rescue (ARFF) responded to the accident site and extinguished the fire. The engine structural supports were substantially damaged during the nose gear collapse. The forward fuselage structure sustained substantial damage during the ground fire.

The Yakovlev model Yak-52 utilizes air pressure during landing gear extension/retraction, flap deployment, wheel braking, and engine start. The pneumatic system is activated by opening a main valve located in the cockpit. This pneumatic system valve should remain open for all operations. However, with the pneumatic system valve closed, the residual air downstream of the valve can be used to operate the associated systems until the pressure is depleted. Extending the nose gear requires the most amount of air pressure force in order to deploy the nose gear forward into the relative wind.

The pneumatic system valve was found closed (off) at the accident site, the observed air-pressure supply was about 75-percent, and the landing gear selector handle was down. The pneumatic system valve was opened, and the nose landing gear deployed rapidly into the down-and-locked position. The nose landing gear components appeared to be undamaged.

While seated in the front seat, the pneumatic system valve is located on the left sidewall, slightly behind the pilot's left elbow position. The pilot reported that the pneumatic valve installed in his airplane did not incorporate an open/closed position placard. The activation of the pneumatic valve is normally identified by the aural sound of air rapidly charging the remainder of the system. The pilot also noted that the cockpit air-pressure gauge only indicated the bottle pressure, regardless of the pneumatic valve position.

The pilot reported that before the first flight of the day, he opened the pneumatic system valve prior to pulling the airplane out of his hangar. He subsequently checked the position of the valve two additional times before departing on the flight to KGXY. After an uneventful landing at KGXY, he set the parking brake and left the pneumatic system valve in the open position. After refueling he reentered the cockpit to prepare for the return flight to KFNL. The pilot surmised that he inadvertently closed the pneumatic system valve as he followed the before engine startup checklist. With the pneumatic system valve closed, he was able to start the engine, takeoff, and fully retract the landing gear. As the flight approached KFNL, he extended the landing gear by placing the landing gear handle into the down position. The pilot reported that before landing he verified the position of the landing gear by referencing the mechanical barber-pole indicators, which suggested that all of the landing gear were fully extended.

A mechanic familiar with Yak-52 airplanes reported that the mechanical barber-pole indicators, located forward of the windscreen and in the pilot's sightline, should not be used as the primary indication of the landing gear position. The mechanical indicators are intended to be used in conjunction with the landing gear position indicator lights to ensure the landing gear is fully extended.

At 1455, the airport's automated surface observing system reported the following weather conditions: wind 080 degrees at 10 knots, gusting 17 knots; clear skies; visibility 10 miles; temperature 29 degrees Celsius; dew point 06 degrees Celsius; altimeter setting 29.95 inches of mercury. The direction of the surface wind had varied between 040 and 140 degrees since the previous hourly weather report.

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