An airline crew recently experienced a pitch trim runaway that caused an uncommanded climb to 14,000 feet. Here's what you should know about control failures like this...

Low-Altitude Pitch Trim Runaway

The following incident occured as an Embraer 170 departed from Atlanta. Shortly after takeoff, the pilots experienced a pitch trim runaway during their climb. Initially, the pilots were not able to stop the trim runaway, and the aircraft climbed to 14,000 feet. They declared an emergency shortly after takeoff, to help explain the gravity of the control failure to ATC. There hasn't been a final report released about this event, so what we have at this point is the ATC audio.

The crew did an excellent job flying the plane, communicating with ATC, and safely returning to Runway 10 at ATL. (Remember: Aviate, Navigate, Communicate!)

Here's the ATC audio from the event:

System Review: How Trim Works

Trim holds airspeed. If you trim for a speed and let go of the yoke, your plane will keep flying at that speed, regardless of your power setting. If you trim and change your power, your plane will pitch up or down to maintain your trimmed speed. Trim for climb speed, let go, and you'll maintain climb speed. Trim for cruise, let go, and it'll maintain cruise speed. Trim for final approach speed, let go, and you'll maintain final approach speed. The list goes on.

Trim systems can fail. Broken pulleys, lines, hydraulics, or even FOD in the cockpit can render a trim system useless. A trim runaway happens when an un-commanded trim setting progresses.

Electric Trim vs. Mechanical Wheels

Most general aviation airplanes have pulley/cable trim systems with manual control wheels. These can't "runaway" on you. But other airplanes have electric trim controls with primary and secondary switches.

The Embraer 170, for example, does not have a manual trim wheel. It's trim is controlled with electric switches on the control yoke and center pedestal. And even if trim fails, control can be maintained below certain speeds.

Emergency Procedures Are Similar Across The Board

Look to your emergency checklist or POH for details on how to handle trim runaways in your airplane. For the most part, all procedures are similar. Press and hold the autopilot disconnect button (if available), pull system circuit breakers/push system disconnect buttons, and slow down. In many cases, the slower you fly, the lighter control forces you'll need to control the airplane. If you're flying an airplane without electric trim, you won't experience a trim runaway, but your trim might become jammed instead.

How You Experienced A Trim Failure?

Control failures are a big deal, and there's not a lot we can do in the cockpit to "fix" the situation. Have you ever experienced a control failure or a trim runaway? Tell us in the comments below.