Yakovlev Yak-52 N76YK accident near Loveland, Colorado

Probable cause

The pilot’s inadvertent closure of the pneumatic system valve, which resulted in the nose landing gear not fully extending before landing. Contributing to the accident was the pilot's reliance on the mechanical landing gear position indicators instead of the cockpit indicator lights to verify landing gear extension.

NTSB analysis

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-fed fire in the engine compartment ensued. Postaccident examination revealed that the pneumatic system valve, which should remain open for all operations, was in the closed position. This resulted in less pressure in the system than was needed to fully extend the nose landing gear before landing. When the pneumatic system valve was subsequently opened, the nose landing gear deployed rapidly into the down-and-locked position. The nose landing gear system components appeared to be undamaged. The pilot reported that earlier in the day he had opened the pneumatic valve and surmised that he must have inadvertently closed the pneumatic system valve before departing on the accident flight. The pilot reported that before landing he verified the position of the landing gear by referencing the mechanical barber-pole indicators, which suggested the landing gear was fully extended. However, the mechanical barber-pole indicators, which are 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 in the cockpit to ensure the landing gear is fully extended.

Text from the NTSB. Open the NTSB docket for CEN12LA374 for the full record.