United States of America

The pilot landed with the landing gear in the retracted position, when both the main and auxiliary hydraulic systems failed to extend the gear. The airplane caught fire as it skidded down the runway. The left inboard main tire had blown on takeoff and a 30-inch section of tread was loose. Black marks were along the length of the landing gear strut and up into the wheel well directly above the left inboard wheel. The normal and emergency hydraulic systems both connect to a common valve body on the landing gear actuator. This valve body also had black marks on it. A gap of 0.035 inch was measured between the valve body and actuator. When either the normal or auxiliary hydraulic system was pressurized, red fluid leaked from this gap. Examination revealed that one of two bolts holding the hydraulic control valve in place had fractured and separated. The fractured bolt experienced a shear load that was oriented along the longitudinal axis of the actuator in a plane consistent with impact forces from the flapping tire tread section.. Separation of only one bolt allowed the control valve to twist about the remaining bolt in response to the load along the actuator's longitudinal axis. This led to a loss of clamping force on that side of the actuator. Hydraulic line pressure lifted the control valve, which resulted in rupture of an o-ring that sealed the hydraulic fluid passage. 14 CFR 25.739 describes the requirement for protection of equipment in wheel wheels from the effects of tire debris. The revision of this regulation in effect at the time the airplane's type design was approved by the FAA requires that equipment and systems essential to safe operation of the airplane that is located in wheel wells must be protected by shields or other means from the damaging effects of a loose tire tread, unless it is shown that a loose tire tread cannot cause damage. Examination of the airplane and the FAA approved production drawings disclosed that no shields were installed to protect the hydraulic system components in the wheel well.

While enroute from Pueblo, Colorado, to Columbia, South Carolina, the captain's windshield delaminated, and the flight diverted to Fort Lauderdale, Florida, for repairs. The flight crew stated the first officer was flying the airplane and had been instructed by the captain to make a firm landing at Fort Lauderdale to get the airplanes weight on the wheels, due to the airplane being light. The landing was firm and the first officer activated the engine thrust reversers. As the nose landing gear touched down, the airplane began veering to the left. Attempts to control the veer to the left were unsuccessful and the airplane ran off the left side of the runway. The airplane then ran over a taxiway and collided with a taxiway sign and the concrete base for the sign. The nose landing gear collapsed and the airplane came to rest. Examination of the runway showed alternating dark and light marks from the left main landing gear tire were present on the runway about 160 feet before marks from the right main landing gear tire are present. Post accident examination of the airplanes landing gear, tires, wheels, bakes, spoilers, and engine thrust reversers, showed no evidence of pre-accident failure or malfunction. At the time of the accident the flight crew had been on duty for about 17 hours 45 minutes.

The airplane landed wheels up after the instructor pilot failed to lower the landing gear. The instructor told the student to execute 'a no flap landing due to a simulated hydraulic pump failure.' The student established the airplane on the approach and called for the 'Emergency Gear Extension Checklist.' The instructor delayed extending the gear in accordance with the operator's flight standards manual, which stated that the landing gear should not be extended until the landing was assured. Later in the approach, when the gear warning horn stopped sounding, due to the student's movement of the power levers forward, the instructor removed his hand from the gear handle without extending the gear. The instructor stated that 'because [the student] had already called for the [Emergency Gear Extension] checklist once before, in a split second thought process, [he] mistakenly thought it had been completed.' Following the accident, the landing gear system was tested and found to operate normally. Review of the maintenance records revealed no uncorrected discrepancies. At the time of the accident, the instructor pilot was completing a 9-hour work day, and did not have a lunch break.