As a major part of my 25-year job as an avionics technician, I have the responsibility of returning aircraft to service after avionics work has been performed. I have to go on many test flights in all types of corporate and private aircraft. Consequently, I have the dubious privilege of encountering all kinds of problems — ranging from minor avionics squawks to major airframe issues. Most of these problems usually are solved on the ground, but many times they become evident only in the air.
We had just completed avionics work on a Cessna Citation 500, and I was asked to go along on the test flight to see whether the autopilot problems had been successfully repaired. Our maintenance department had also completed some work, and all general aircraft functions were to be checked on this test flight. I had already performed a full avionics systems test on the ground; all systems appeared normal.
The owner of the aircraft was a German gentleman who spoke English with a heavy accent, and his copilot was his son. Usually I sit in the copilot's seat when performing test flights, but since his son was coming on the flight, I was relegated to sitting on the seat directly behind the copilot.
We taxied to the active runway and stopped in the run-up area. I watched and was impressed as the pilot and his son performed a very thorough preflight, using a complete checklist. I paid close attention as they checked the position of the elevator trim tab. It was correctly set to the takeoff position. After we were cleared for takeoff, I watched as the pilot pushed forward on the power levers. The airplane surged forward, and the airspeed indicators came alive. Everything appeared to be OK, when suddenly the jet jumped off the runway. It seemed to me to be a bit too soon, and the pilot suddenly began screaming in German at his son. I did not understand what he was saying until he looked back at me and shifted to English.
"Trim runaway, trim runaway," he screamed. The Citation was lurching nose-up into the air, and I knew we were about to stall. The pilot and his son both had their knees up against the control column, and each had both of his hands on the control yokes to hold down the nose. The pilot pulled back on the throttles to ease the pressure on the controls. There was no runway left to attempt a landing straight ahead. Every time he eased back on the throttles, it felt as if the airplane would not be able to stay in the air with such a small amount of thrust. He then would apply power, and again the nose would again begin to pitch up into a stall attitude. I knew that if the situation were not resolved we would either stall and crash into the industrial area to the east of the airport or, if he pulled back on the throttle too much, we would not be able to remain airborne.
We managed to turn crosswind and downwind while reporting to the tower that we had an emergency. I took off my seat belt, worked my way between the pilot and the copilot, and popped the trim circuit breaker. I then grabbed the manual trim wheel and began trimming it forward. The wheel just spun freely in my hands with no effect on the trim condition. We continued to hobble on downwind, then base and final, with the nose of the plane lurching for the sky and then dropping toward the ground over and over again. As we came in on final, the pilot throttled back completely and basically made a dead-stick landing. We rolled off the runway and coasted to a stop in a run-up area. As soon as we stopped I knew what had happened. The pilot and his son sat there for a few moments, trembling and struggling to regain their composure. The copilot and I then climbed out of the airplane, and I immediately went to the back of the Citation.
"Open that," I said, pointing to the battery access compartment in the rear of the airplane. I immediately saw the cause of the problem. Lying in a tangled mess in front of me were the aircraft trim cables. They had completely fallen off the trim pulley assembly near the roof of the aft compartment.
Upon further investigation, it was discovered that the airplane had just completed a major airframe inspection at another facility, and the cable stops for the trim cables had been placed in the wrong position. The airplane had been flown from Texas with no problem.
Sometime during the airplane's stay in Ft. Lauderdale, someone ran the trim control to the full nose-up position. The trim cable system has a chain that rides on a gear back at the tail assembly. With the stops in the incorrect position there was nothing to stop the chain from riding off the gear when the trim wheel was run all the way up. The trim tab remained in the full nose-up position, and then the cables fell off the gear. The trim indicator in the cockpit, which was now no longer mechanically linked to the trim tab in the rear of the aircraft, indicated takeoff position when checked by the pilot.
Ever since this experience I have advised all pilots who fly in Citations with this type of trim system to open up the battery access door and visually inspect the trim cable system in the rear of the aircraft as part of their preflight inspection. It could save someone's life.
Al Vargas, AOPA 1408258, of Deerfield Beach, Florida, is an avionics technician and 400-hour private pilot.
"Never Again" is presented to enhance safety by providing a forum for pilots to learn from the experiences of others. Manuscripts should be typewritten, double-spaced, and sent to: Editor, AOPA Pilot, 421 Aviation Way, Frederick, Maryland 21701.
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