pjvr99 Posted February 20, 2011 Share Posted February 20, 2011 So there we were, an engine giving 104% performance, 29.85"Hg air pressure, and 20°C OAT. Engage the pitchlock, push the throttle to take off. Watch the overspeed at 105% rpm, fuel flow at 1500pph, torque around 10000"lb. Next moment fire warning light flashes on, fuel flow shoots to 2000pph, torque rising rapidly, and rpm on the way down. Then everything goes back to pitchlock settings, ....... and again the fire warining, and fuel and torque rise, rpm drop, and back again. Fighting the instinctive throttle back to prevent overtorque/flame-out situation while pitchlocked, yet still trying to analyze the situation, I finally opted for feather shut- down. Lots of extremely wide eyes in the control, I find myself thinking "double rum and coke would be good about now", and realizing that I'm in the Magic Kingdom. So reset everything, cool down the engine and start up again. Everything all happens again except this time there is no response on the throttle when I tried to throttle back. Another feather shut down!! Decided that because the engine had been standing unpreserved for a looonnnggg time, it must be the fuel control governor that cr@pped out. One FCU change later and we try again. Initial pitchlock check good - joy!! 20 minutes later (and another feather shutdown), I'm shaking from adrenaline overload. After consulting with the prop shop brains trust, the decision was made to replace the valve housing. Again everything checked good, with 3 back-to-back pitchlocks successful. Work through an entire run sheet, and get to the pitchlock step again, back to square one!!! Slaved in a spare prop main control conduit - no change! Started investigating the test cell cables and junction boxes. Finally found the 'sync box' of the test cell had a burnt component. The main control and the fire detector leads run in the same harnass. So I'm guessing damaged wires inside the harnass shorted between the prop control and the fire circuit. Disabled the fire circuit and replaced the prop control box, now everything is working as advertised. My arms, however, feel like I've been wrestling bears or something ....... Quote Link to comment Share on other sites More sharing options...
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