As a newly certificated private pilot with 200 hours in my logbook, I bought a 1972 Cessna 172L that had been restored to excellent condition. Everything in the airplane seemed to work fine until the weather got colder. At that point the elevator trim started getting very stiff at higher altitudes and, eventually, on the ground. Finally it just froze solid. My mechanic examined and lubricated the elevator trim, which made it better briefly, but the condition returned. I asked him to rebuild it.
It was a cold winter morning on the day after the job was finished when I went for a test flight. After my preflight, I sat in the cockpit and ran the trim through its range. I pulled the yoke fully aft, thus allowing me to see the trim tab work and confirm that with the trim fully nose-up, the tab was deflected far above the elevator. Everything wound smoothly, with a nice positive feel. Satisfied, I returned the trim to the takeoff setting, fired up the engine, and taxied to the active runway.
My takeoff was normal. The crisp, cold air and high pressure combined to give me a 1,100 foot-per-minute rate of climb — not too shabby for a 172. Indeed, my nose-up attitude increased as I gained speed — requiring me to push forward on the yoke to maintain the proper attitude. I rolled the trim wheel nose down to take some of the pressure off the yoke. The airplane responded by trying to climb at an even higher nose-up angle. I glanced at my airspeed — it was decaying below the best angle-of-climb speed. To keep the nose from going too high, I pushed the yoke forward with more force, fighting the power of the engine. I cranked in additional trim to lower the nose. But all that seemed to happen was that I had to push even harder on the yoke to maintain control of the airplane. I cranked in more trim and realized, as the airplane kept pulling up, that I was losing control. Also, the controls began to get mushy, telling me that I was about to stall with the engine at takeoff power at perhaps 250 feet agl.
I realized that I was in deep trouble. With the mushy control I was able to push the nose down a little; but as soon as I did so, the airspeed picked up again and the yoke forces became stronger, requiring me to push harder again. There was no way that I could get the nose down for level flight — I simply was not strong enough to overcome the yoke forces. I finally did something sensible — I pulled the throttle most of the way back. Almost instantly, the great pressure against me on the yoke disappeared, and I regained control of the airplane. I remembered to pull the carburetor heat on and limped around the pattern at 1,900 rpm, while still pushing on the yoke to maintain a level attitude.
After I landed and shut down, I tried to figure out what was wrong. I climbed out of the airplane and examined the trim. It all looked fine. I ran the trim control through its range again; the trim tab seemed to track perfectly. I decided on one more test flight before going back to the mechanic. I reasoned that I had now figured out how to control the airplane.
After the second takeoff, the circumstances began to repeat themselves. I added nose-down trim — the nose tried to go up. Finally, the light dawned — the trim was working backwards. Experimentally, I rolled the trim wheel down, which should have made the nose go up — voilá! The nose dropped. Now in full control, I went around the pattern with the trim working perfectly, albeit backwards, and landed again.
At this point I did not want to fly the airplane another minute. I taxied to the mechanic's hangar and told the shop owner what had happened. He was furious that such a mistake had come out of his shop. Apparently, a new mechanic who had come well recommended had been assigned to my airplane.
The incident taught me several things. First, think through how things work on an airplane — when the trim tab is deflected down, it forces the elevator up. I had checked the freedom of travel of the trim control, but I had never thought about the way it worked to confirm that it was going in the proper direction. We have all heard horror stories of fatal crashes because ailerons were rigged backwards. Yet the same thing almost happened to me because the trim control was reversed. The incident also taught me that maybe I would make a decent pilot some day — I had survived a potential tragedy by being alert enough in an emergency to retard the throttle when I ran into forces I could not otherwise control.
Bob Locher, AOPA 1115770, of Geyserville, California, has now logged 750 hours in seven years of flying. He still owns the 1972 Cessna 172L.
"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.
Related Articles
