With 37 passengers, two pilots and one cabin attendant a deHavilland DHC-8-102 was scheduled to operate a flight from Seattle to Spokane (Both in the state of Washington, USA). This would be the crew's third sector of the day after an uneventful return trip to Pasco (Washington, USA).
The cockpit section (Source; baaa-acro.com © KG Photography)
After completing the required preflight requirements, and with the passengers on board, the aircraft's engines were started. At 18.10 lt (local time) the aircraft started to taxi to Runway 16L. 15 minutes later the crew read back their take-off clearance and started their take-off roll. The take-off was uneventful with the aircraft lifting off at 101 knots, with a positive climb rate the landing gear was retracted, followed by flap retraction. Subsequently, engine power was reduced from the take-off setting to 1050 rpm and 88% torque. At an altitude of 1000 feet, a left turn was initiated. Once the aircraft was levelled off after the turn the crew noticed a reduction in power on the righthand engine, with the torque dropping to ~50%, and the aircraft yawing to the right. Both power levers were advanced to the maximum power setting, however, the right-hand engine torque kept on dropping. As it was still producing power the captain elected to keep the engine running, however a return to the airport was deemed necessary. ATC and the cabin attendant were informed about the situation and the required checklists were completed.
As the aircraft decelerated the landing gear was lowered and the aircraft was turned onto the final approach, at that point, they were ~1 mile from the touchdown zone of runway 16L
While scanning for possible conflicting traffic the first officer observed a bright flash from the right engine, and the centre access panel missing from the nacelle. He then observed flames and more parts (panels) departing the aircraft. He immediately informed the captain by stating "We got a fire".
Engine side view (Source & © NTSB) The captain called for flaps 15º and retarded the right condition lever to the START-FEATHER position. Instructing the copilot to pull the fuel cut-off T-Handle and to discharge the fire extinguishers. This had no effect and the fire continued to burn. At that time the crew noticed the three green down and locked lights for the landing gears had gone off. While approximately 1/4 mile from the runway the crew noticed that the controllability of the aircraft was changing, it was wallowing around. As the aircraft touched down a short while later the power lever for the left engine was pulled back, and the aircraft then started to veer to the left of the runway. With the application of rudder, differential braking and nosewheel steering the captain attempted to regain directional control. This was unsuccessful. When also the emergency brakes were carefully applied, no noticeable deceleration was present, after which the captain put the lever in the parking position.
Part of the wreckage (Source; baaa-acro.com © KG Photography)
With the aircraft now uncontrollable the crew informed ATC of their situation and locked their shoulder harnesses. The aircraft crossed a grass patch and taxi ways it rolled onto the ramp. it struck several jetways and pieces of ground handling equipment, causing the outboard section of the left wing. Finally coming to a stop against another jetway.
Firefighters extinguished the post-crash fire and assisted the passengers and crew in evacuating the aircraft. The flight crew had to be liberated from the flight deck as the cockpit door and emergency exit were jammed shut.
Four of the passengers sustained serious injuries, while 24 other passengers and the flight- and cabin crew sustained minor injuries. The material damage was extensive, with the aircraft (Valued at $ 5.640.000) and various pieces of ground equipment being destroyed (with the damage estimated at $280.000 at the time of the accident investigation). An investigation was launched by the NTSB (National Transportation Safety Board). After an extensive investigation, the Accident Investigation Report was published ten months after the accident. A large list of findings is contained in the report, with the finding of an incorrectly installed fuel filter cover being identified as the cause of the fuel leak, the ignition source was not identified.
The filter cover installation, correct left, as found on the accident aircraft right. (Source & © NTSB)
The NTSB concluded that the probable cause of the accident was;
The improper installation of the high-pressure fuel filter cover allowed a massive fuel leak and subsequent fire to occur.
Contributing to the accident was the failure of the airline maintenance crew to detect and correct the improper installation
Also contributing was the loss of the right engine centre access panel by a fuel explosion. Causing the fire fighting to be ineffective, resulting in a burn trough of a hydraulic line, leading to a loss of control
The accident report which served as the source for the blog can be accessed by clicking on the .pdf file below;