Evergreen International Airlines

Learjet 35

The crew of the twinjet reported that the positioning flight after maintenance was uneventful. However, during the landing roll at their home base, the thrust reversers, steering, and braking systems did not respond. As the airplane approached the end of the runway, the pilot activated the emergency braking system; however, the airplane overran the end of the runway, coming to rest in a ditch. None of the three occupants were injured, but the airplane sustained substantial damage to both wings and the fuselage. Two squat switches provided redundancy within the airplane’s electrical system and were configured to prevent inadvertent activation of the thrust reversers and nosewheel steering during flight and to prevent the airplane from landing with the brakes already applied. Because postaccident examination revealed that the squat switch assemblies on the left and right landing gear struts were partially detached from their mounting pads such that both switches were deactivated, all of these systems were inoperative as the airplane landed. The switch assemblies were undamaged, and did not show evidence of being detached for a long period of time. The brakes and steering were working during taxi before departure, but this was most likely because either one or both of the switches were making partial contact at that time. Therefore, it was most likely that the squat switch assemblies were manipulated on purpose during maintenance in an effort to set the airplane’s systems to “air mode.” Examination of the maintenance records did not reveal any recent procedures that required setting the airplane to air mode, and all mechanics involved in the maintenance denied disabling the switches. Mechanics did, however, miss two opportunities to identify the anomaly, both during the return-to-service check and the predelivery aircraft and equipment status check. The anomaly was also missed by the airplane operator’s mechanic and flight crew who performed the preflight inspection. The airplane’s emergency braking system was independent of the squat switches and appeared to operate normally during a postaccident test. Prior to testing, it was noted that the emergency brake gauge indicated a full charge; therefore, although evidence suggests that the emergency brake handle was used, it was not activated with enough force by the pilot. The pilot later conceded this fact and further stated that he should have used the emergency braking system earlier during the landing roll. The airplane was equipped with a cockpit voice recorder (CVR), which captured the entire accident sequence. Analysis revealed that the airplane took just over 60 seconds to reach the runway end following touchdown, and, during that time, two attempts were made by the pilot to activate the thrust reversers. The pilot stated that as the airplane approached the runway end, the copilot made a third attempt to activate the thrust reversers, which increased the engine thrust, and thereby caused the airplane to accelerate. Audio captured on the CVR corroborated this statement.

Douglas DC-9

The DC-9 arrived at Carswell AFB at 01:12 CST after a flight from Kelly AFB. The aircraft was off-loaded and re-loaded with cargo by USAF personnel. The engines were then started at 02:04. The crew received taxi instructions for runway 17 and took off from this runway at 02:09. At (or immediately after) rotation, the main cargo door opened. An emergency was declared and the crew climbed to 2500 feet msl before entering a right turn. When about 5nm north of the airport the captain began a shallow turn to the right (for base leg). The aircraft crossed the extended centreline and the captain tightened the turn to establish their position relative to the runway threshold. In doing so, the air load on the door probably caused it to rapidly move to its full open over the top position. A sudden opening of the door would also have produced an unexpected change in the yawing and rolling moments. The captain, possibly partially disoriented, may not have sensed the increasing roll and nose tuck and thus failed to correct a changing attitude until a critical bank angle and loss of altitude had occurred. The DC-9 struck the ground in an inverted, nose down, left wing low attitude and disintegrated. It appeared that the first officer, when closing the main cargo door, didn't hold the door control valve 'T' handle in the closed position long enough for the latching hooks to move into place over the door sill spools. External latched and locked indicators were applied incorrectly, so the first officer thought the door was latched properly when the handle was pointed more toward the 'locked' than the 'unlocked' chevron. It also appeared that one of the two open door warning light switches was malfunctioning. Because of their wiring, this malfunction made the entire door warning system ineffective.

De Havilland DHC-6 Twin Otter

The airplane departed Nome on a VFR flight to Shishmaref, about 122 miles to the north. Few minutes after takeoff, the crew encountered poor weather conditions with snow falls, limited visibility (night) and icing conditions. The airplane struck the slope of a mountain located to the north of Nome. As the airplane failed to arrive at destination, SAR operations were initiated but eventually suspended few days later as no trace of the aircraft nor the four occupants was found. The wreckage was localized on February 10, 1980. The aircraft was destroyed upon impact and all four occupants have been found dead.

Cessna 411

While in cruising altitude on a ferry flight from Flagstaff to Silver City, the pilot lost control of the airplane that entered a dive and crashed in flames near Show Low. The aircraft was totally destroyed and the pilot, sole occupant, was killed.