SEA93LA172

Upon arrival at victoria, british columbia, the pilot was unable to extend the nose landing gear. He diverted to Portland international airport where nose gear extension was again unsuccessful. The pilot executed a nose gear up landing and shut down both engines prior to touchdown. The aircraft landed hard in the grass short of runway 28R. Examination of the landing gear system revealed no malfunction with either the nose gear actuator or hydraulic system. A tire imprint on the inside left nose gear door and paint observed abraded from the bottom edge of the gear door fork, indicated overcenter jamming of the gear with the hinge pin seat along the bottom edge of the fork.

On August 8, 1993, at 2025 hours Pacific daylight time (PDT), a Beech BE-76 Duchess, N3692X, registered to and being flown by Donald Flynn, a commercially certificated pilot, sustained substantial damage while landing with the nose gear retracted at the Portland International Airport, Portland, Oregon. The pilot and his wife were uninjured. Visual meteorological conditions existed at the time. The airplane had been operating on an IFR flight plan originating from Whitehorse, Yukon Territory, Canada, and destined for Victoria, British Columbia. The flight, which was personal in nature, was to have been operated in accordance with the requirements set forth in 14CFR91.

The pilot reported that upon arrival at Victoria he was able to extend the main landing gear but the nose landing gear remained retracted. This condition was confirmed by a tower flyby and the illumination of green lights for both main gear and the absence of a green light for the nose gear. The pilot then diverted to Portland.

Upon arrival at Portland, the pilot communicated with a Beech trained mechanic and discussed the condition. Additional attempts to lower the nose gear were unsuccessful and the pilot executed a nose gear retracted landing.

An FAA inspector who interviewed the pilot following the landing reported that the pilot intentionally chose to land in the grass short of the runway, and that he shut down both engines prior to touchdown. The aircraft was observed to land hard by tower and crash crew personnel in the grass short of the threshold of runway 28R and slightly north of the extended centerline.

Testing of the main landing gear system as well as examination of the nose gear wheel well by FAA personnel and a mechanic from Flightcraft revealed that the nose landing gear hydraulic actuator operated properly as did the hydraulic power pack.

Inspection of the nose gear wheel well by the Investigator in Charge revealed a black smear on the inside center section of the left nose gear door. The smear was close to the inboard edge of the door, directly beneath the normal resting location of the nose tire with the nose gear in the retracted position. The smear was striated, i.e., longitudinal streaks were observed within the smear, consistent with those which would have been made had the door contacted the nose wheel tire while still rotating. The sequencing of the nose gear doors is adjusted such that the nose wheel does not normally contact the doors.

The nose gear doors retract fork was also inspected. The upper and lower fork guide faces were observed to be free of paint as was the inside of the fork groove. The outside edge of the lower guide face displayed paint abrasions, as did the outside edge of the lower portion of the fork. No such paint abrasions were observed on the corresponding upper outside fork edge (refer to DIAGRAM I).

Normal operation of the nose gear occurs when hydraulic pressure at the nose gear actuator retracts the actuator cylinder. This pulls the upper drag leg hinge point up and aft in an arc. The lower drag leg, also attached at this point, moves in the same direction. The hinge pin between the two drag legs extends outboard and eventually contacts the fork guide faces. As the pin moves into the fork groove, the fork rotates in an upwards and aft arc, retracting the left and right nose gear doors via mechanical linkages.