SEA94FA111
SEA94FA111

HISTORY OF FLIGHT

On April 30, 1994, at 1330 Pacific daylight time, an amphibious Cessna TU206G, N732JK, collided with mountainous terrain after an aborted landing at Lake Isabel, Gold Bar, Washington. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the airline transport pilot and his passenger were seriously injured. The flight originated from Lake Sammamish, Issaquah, Washington, on April 30, 1994, at 0930. Stops were made at Lake Cavanaugh, Washington; Lake Stevens, Washington; and Arlington, Washington.

During a telephone interview, the pilot reported that he intended to land on the lake. The approach to the lake was made to the east. The pilot completed the pre-landing check while on final approach. When the airplane was approximately one-third of the way down the lake, just prior to touch down, the pilot noted that the right side green landing gear down light flickered on and off, the blue gear up lights were illuminated and steady. The pilot stated that he added full power and cycled the gear. The pilot continued to the east, travelling along the south side of the lake. At the end of the lake, the pilot made a climbing left turn and collided with trees along the northeast side of the lake, approximately 500 feet above the water level. The pilot reported that the engine was producing full power.

The pilot stated that he did not look at the left side visual indicator on the top of the float, nor did he have his passenger look at the right side indicator prior to the aborted landing to see if they were indicating the position of the gear.

The passenger recalls that they were intending to land. The airplane was over the lake and low in the valley when the pilot added power and started to climb.

PERSONNEL INFORMATION

The pilot holds an airline transport pilot certificate and is rated for single-engine land, single-engine sea, and multi-engine land airplanes. The pilot did not report his total flight time, therefore, a total flight time was obtained from the Federal Aviation Administration Medical Records. The pilot's last medical certificate was dated January 26, 1994. At this time, the pilot reported a total flight time of 12,700 hours, with 100 hours in the last six months.

WRECKAGE AND IMPACT INFORMATION

The water level below the wreckage was at approximately 2,900 feet Mean Sea Level (MSL). The wreckage was located approximately 500 feet above the water level at 3,400 feet MSL. The terrain angle was measured at approximately 30 degrees. The area was covered with trees measuring in height to 100 feet and dense ground shrubs. The airplane was positioned on its right side with the nose of the airplane positioned on a magnetic bearing of 60 degrees. The right wing was on the down hill side of the wreckage and had separated forward at the wing root. The wing remained attached at the forward attach point. Both the flap and aileron remained attached at their respective hinges. The left wing separated at the point between the aileron and the flap, just outboard of the wing strut. The inboard section remained attached at the wing root with the flap attached at the hinges. The outboard section of the wing with the aileron attached was folded over on top of the inboard section. The flaps were extended to 19 degrees. A damaged tree was noted 20 feet uphill from the wreckage.

Both floats were severely damaged and displaced to the right with respect to the fuselage. Both main landing gear tires were in the retracted position. The nose gear tires located at the bow of the floats were dislodged and laying near the front of the wreckage. Both nose gear actuators were in the locked and retracted position.

The visual gear indicators located on the top of the floats were visible. The left float red indicator flag was in full view through the inspection window and in the "gear up position." The right side flag was also visible and in the "gear up position," however, it was slightly aft. Impact damage was noted just forward of the inspection window. The inspection plate was removed from the right float and it was found that the latch was disengaged by .7 inch. The cable remained attached through the turnbuckle and the cable was tight. Movement of the cable by hand moved the latch. The latch for the left side float was engaged.

The empennage was bent over to the right at a point just aft of the baggage compartment. The control cables were still attached to the empennage and tight. The horizontal stabilizer with the elevators attached, and the vertical stabilizer with the rudder attached were in place and displayed minor damage.

The propeller assembly remained attached to the crankshaft, and the engine remained attached to the airframe. All three blades were bent and displayed extensive leading edge scratches and gouges. One blade tip measuring five and a half inches had separated from one of the blades and was found uphill from the wreckage near the damaged tree.

TESTS AND RESEARCH

The landing gear retraction system is made up of various mechanical, hydraulic, and electrical parts that function together to extend or retract the landing wheels. A gear actuation cylinder located in the aft section of each float, operates both the bow and main gear mechanism through a continuous cable loop.

The hydraulic system consists of two gear actuation cylinders that are operated by an electric hydraulic powered system. Retraction and extension of the landing gear is accomplished by a selector switch located in the cockpit that is integrated with electrical circuits that help control and indicate the position of the gear. Mechanical latches and over-center geometry provide down locks for the main gear and latches for up locks. The bow gear is held in position by the control cable and also utilizes over-center geometry in the down position.

During a normal cycle, the gear locks up or down and the position indicator lights (one for the right side and one for the left side), in the cockpit illuminate to indicate the completion of the cycle. Landing gear extended and locked can be detected by illumination of the down green indicator lights. The gear retracted and locked can be detected by the illumination of the blue water lights. The lights for extended or retracted will go on only when the landing gear is in the locked position. Neither set of lights is illuminated when the landing gear is in transit.

The single red indicator light, labeled "pump on" comes on when current is being supplied to the landing gear motor. When the main gear slide fittings move to the limit of their travel, mechanical latches engage and the appropriate gear limit switches are actuated. The pump is shut off and the appropriate gear position is noted in the cockpit.

The pilot stated that both the blue lights for gear up were illuminated the entire time, however, the green light on the right side only flickered.

The float terminal strip was tested and continuity was established. The remainder of the system had been compromised, therefore, continuity throughout the entire electrical system could not be established.

A representative from the Edo Corporation, the manufacturer of the floats, reported that since the blue water lights were illuminated, the gear would have been in the up and locked position. For the green light on the right side to flicker, he reported that a possible short in the system may have been present.

ADDITIONAL DATA/INFORMATION

The wreckage was released to the owner's representative on September 21, 1994. Shortly after the accident, the wreckage was removed and stored at a facility in Issaquah, Washington.

Lake Isabel is approximately one-and-a-half miles long and 1,600 feet wide at its widest point. The water level varies from the published 2,847 feet depending on the season. At the time of the accident, the water level was approximately 2,900 feet. Steeply rising terrain covered with dense trees surrounds the lake. Normally approaches are made to the east, through a valley on the west end of the lake. Departures are normally made to the west, exiting through the valley.

The Cessna Pilot's Operating Handbook, Landing Gear Malfunction Procedures, states that if the landing gear fails to retract, one of the steps is to visually check at the float inspection openings.

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