Plane & Pilot
Tuesday, March 11, 2014

Control Failures


Learning to fly with trim can save your life



Teamwork is important in making sure that control failures don't happen. Patty Wagstaff and her crew follow a written checklist before every flight, and the most important item on it is to check for FOD in her airplane.
The NTSB Report read: "On-scene examination determined that the airplane impacted the ground with the left wing down and a 30-degree nose-down pitch. The wreckage examination identified a loose, puck-like, 4.5-inch diameter portable XM-GPS antenna in the empennage tail space that houses the elevator bell crank. The antenna had a 9-mm diameter semicircular indentation witness mark that was consistent in shape and size to the end of a 9-mm diameter bolt that attaches the forward spar of the vertical stabilizer to the fuselage frame, located directly above the elevator bell crank. The antenna location and associated witness mark indicate that the unsecured antenna migrated to the tail section of the airplane and obstructed the free movement of the elevator bell crank, limiting the pilot's ability to control the airplane in pitch."

Control failures and foreign object damage (FOD) aren't something that GA pilots often think about. We might hear of disastrous accidents on takeoff where someone forgets to remove gust locks, but in the air show world, we think about FOD and control failure all the time. In January, the NTSB issued a new safety alert: "All Secure, All Clear (forgotten and unsecured items have jammed control system components and caused crashes)." Aerobatic airplanes are designed to be light, eliminating cockpit refinements like bulkheads, which makes it easy for stuff to get lodged in our flight controls. The careful aerobatic pilot checks for FOD in the airplane before every flight.

I didn't know the pilot in the incident above, but I probably assumed he was too low and lost situational awareness. If the NTSB hadn't found the GPS antenna, we would've never known what happened. An accident without a clear ending is the most tragic because we can't learn from it.

The first of four control failures (yes, I'm counting) I've had due to FOD was in a Super Decathlon. I had just flown 2,500 miles from Alaska to Wisconsin for an aerobatic competition, and the airplane performed beautifully. But, on my first aerobatic practice flight, when I rolled the airplane inverted, I knew immediately something was wrong. I wasn't able to move the stick forward to keep the nose up. Luckily, my ailerons were free and clear, so I was able to roll back upright. The Super D has a very responsive trim control, and I had practiced flying with trim only, maybe just for this moment, so I headed straight for the runway. After landing, I took off the rear fuselage inspection panel and voilĂ ! A full set of keys were wrapped around the elevator bellcrank. They belonged to a friend I had given a ride to just before I left Alaska. He got his keys back via FedEx as soon as I could dig them out of the empennage. Since then, I've never flown akro with a passenger without asking them to first empty their pockets.

Three years later, I was flying a Pitts S-1T. Akro pilots are always looking for ways to lighten their airplanes to get better performance, and I'm no exception. A few days before a contest, I removed the battery from the airplane to save a few pounds.

I arrived at the contest, registered and then took off for a practice flight in the box. I'll never forget the tailslide I executed: The airplane went straight up, the power came off, and I slid backwards and flopped forward to a perfect vertical downline, perfect except that I wasn't able to pull out of it. Something was jamming the elevator control. This wasn't my first rodeo, and I quickly used the Pitts' powerful trim handle to level the airplane off, enter the pattern and make a very careful landing. I looked in the tail and a rather large piece of wood jamming the controls. It was the battery tray. When I removed the battery, I didn't realize the tray the battery rested on wasn't fixed to the steel tube fuselage.



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