加拿大航空服务难度报告 Canadian Aviation Service Difficulty Reports(6)

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Maintenance personnel determined that a connecting rod had failed and then penetrated the crankcase. As a result, engine oil spewed overboard contaminating the general area. Some of the engine oil entered the turbocharger and ignited, causing the fire to flow along the underside of the wing. Heat damage was evident on the lower wing surface. Secondary damage was also occurred on the lower flap skin and landing gear door.
Time Since Overhaul (TSO): 987 hours.
GARRETT TPE331-10UA (Swearingen SA226TC) SDR # 20040115002
Engine Plenum Fitting Weld Cracked
On climb-out, following take-off roll, the flight crew observed a split-second fire warning indication. The flight crew continued to closely monitor the cockpit gauges and then determined that a false indication had occurred.
Shortly thereafter, the left engine gradually began to lose power until it reached about fifty-five percent torque and its maximum allowable EGT limit. The aircraft returned to base and carried out an uneventful landing.
Upon inspection by maintenance crew, the left engine plenum drain fitting, which is welded to the plenum, was found cracked and partially separated. It was observed that the drain fitting had been incorrectly installed in a slightly rearward direction that later resulted in a stress fracture and failure in the weld area. As a result, hot combustion gases entered into the engine compartment and caused some heat damage to the electrical wiring harnesses in the immediate area.
A review of the SDR database revealed several similar incidents describing cracks at different weld areas of the engine plenum. Particular attention should be paid to the weld areas on the engine plenum fittings (igniter mount bosses, bleed-air extraction port boss, drain valve boss, etc).

PRATT & WHITNEY CANADA PT6A-20 (Beech 99) SDR # 20040513008
Engine Power Control Spring Jammed
The engine power was set to 1,290 foot-pounds for take-off roll. Shortly after rotation, the pilot noticed that the engine torque was slowly increasing on the right engine. The co-pilot attempted to reduce engine power but the power lever would not move. The engine torque continued to increase to approximately 1,500 foot pounds and remained there for about 90 seconds.
After reaching a safe altitude, the pilot shut down the right engine and carried out an uneventful landing.
Prior to removing the engine for an over-torque inspection, maintenance personnel carried out an inspection of the engine mechanical control system. It was then noticed that the engine power control spring link was catching on the control lever-mounting bracket. The control spring link is at the base of the rod end that attaches the airframe Teleflex power cable to the input arm on the cam cluster. The action of the spring link, when it snagged the control lever bracket, would be to pull the power lever towards a higher power setting and ultimately jam at that position.
The SDR submitter stated that this link should have been installed 10-15 degrees further in the counter clockwise direction on the power cable. Furthermore, the submitter stated that the maintenance manual does not give any information on the placement of this link and there is no device, such as a tab or pin that would have prevented this occurrence. A rig pin may not detect this problem unless the rod end is rotated as far as possible clockwise when moving the levers.
　
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