A normal smoggy day at Chino airport. I’d just taken off with my student, Stan, whom I was checking out in the Taylorcraft.

The takeoff was normal, but after we leveled off, Stan was having trouble keeping the plane’s nose down. This was normal, since our increasing speed tended to force the nose up.

“Trim the nose down, Stan.”

“I am trimming down.”

“Trim down more.”

“I am!”

“Give me the wheel.”

I grabbed the dual control wheel and it just about hit me in the face! The airplane was trying mightily to pitch up. If the nose had risen a bit more, the airplane would have stalled and plummeted toward the ground. I could barely keep it level by forcing the control wheel forward. “Stan, we need to turn back to the airport; something’s wrong.” I said.  Let me land the plane because we don’t know how it will react.”

I held forward pressure on the wheel all the way to landing, then jumped out and walked around to the tail. What was I looking for? The horizontal tail surface of the aircraft has two moveable parts—elevator and trim tab. The elevator moves up and down in flight, causing the airplane to pitch up or pitch down.

On the back of the elevator is a tiny trim tab operated by a trim tab wheel in the cockpit. Rolling the wheel back causes the trim tab to turn down into the slipstream (the wind that flows past the airplane in flight). This pushes the whole elevator up, causing the nose of the plane to pitch up. When the tab is turned up, the elevator is pushed down, causing the nose to pitch down.

So I yelled to Stan who was still in the cockpit, “Stan; roll the trim wheel forward.” He rolled. I carefully observed the trim tab back at the tail. As Stan rolled the wheel forward, the trim tab was turning downwards! In flight, this would force the elevator up, which would pitch the nose up, the opposite of how it was supposed to work. The mechanic (probably my boss) had hooked up the trim control cable backwards! “We can’t fly this airplane until we get this control fixed!” I told Stan.

You don’t normally check the trim tab movement when preflighting an airplane. But this mistake could have been disastrous. I hate to think if Stan had been flying without an instructor.