Quote:
Originally Posted by rotorwrench
Aviation systems must be as reliable as possible or they would never be approved for use.
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You know that rule about exceptions?
It sounds like you're an A&P, so you might like this.
I flew for a while for an outfit that had several Aztecs. One day while VFR (Thank you very much) over water and about 10 miles out on a long final, the airplane surges with severe yaw. Oh, God, and just as the tattooed on your eyelids engine out checklist comes to life, another surge and we're back to balanced thrust. In 20 seconds another surge, and back again to normal. Then it was constant, in and out, repeating over and over. WTF??? So after about 6 cycles I decided I didn't like it very much, and pulled a throttle to see which one made it go away. Right one. OK. I don't know what in the world is going on, but this engine is going to idle until I'm on the ground. From there not too big a deal, sort of a short strip single engine, plant it, taxi, offload passengers, call the chief pilot. (Not a single passenger asked a question)
Wait for the company airplane, mechanic tears into it. Turns out this Lycoming series was built with both mags on the same gearcase cover. The cover bolts had come loose, but not completely out. However the cover could hang just far enough out so the gears came out of mesh. What was happening was the gears were meshing in and out, and when they were in sometimes they were out of time and produce no power, and when they were in sometimes they were in time you'd get full thrust.
So yeah, redundancy, until all of a sudden there isn't any redundancy anymore.