Probable Cause #58: Known Deficiencies
This article originally appeared in Aviation Safety, Apr. 2006.It's rare to find even a brand-new airplane without at least one "squawk" -- a mechanical deficiency. Of course, the FAA would say that all equipment and components of an aircraft must be working properly or placarded as inoperative, else the airplane isn't legally airworthy. The FAA will also say that all equipment listed in the aircraft's Type Certificate Data Sheet must be installed and operating for airworthiness, and any additional equipment required by regulation for the specific operation must be in good working order. In the real world, however, it doesn't work that way, and pilots routinely launch a flight with some equipment known to be intermittent, at best. While operating with known deficiencies in equipment is rarely a good idea, there are ways to minimize the risks posed. The severity of a deferred squawk can prevent some kinds of operations, while making others more risky than they need to be. An example of the former might be a failed navigation light, making night flight illegal. An example of the latter could be an inoperative alternator, which could make just about any flight out of visual range from a non-towered home base a bad idea. I have, on occasion, flown aircraft with known squawks. It wasn't the smartest thing I've ever done, but I was careful to ensure there were no other issues with the aircraft, especially the kind that could have complicated the original problem. But I try to draw the line at engine deficiencies, especially with a single. On the few occasions I have had a known engine problem, the only flying I did was either directly over an airport in an attempt to diagnose the problem or the flight to the engine shop. But that's with a single. If I had a twin with a known problem in one of its engines, I don't know if I would be more or less inclined to fly the airplane, either normally or at all. This month's example teaches us that known engine problems are a good reason to ground the airplane until the problem can be found and fixed.