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Aircraft Maintenance: The power of twoaircraft maintenance the power of two

Few things serve as sobering a wake-up call as hearing that someone close to you has had a close call, incident, or accident while flying. I experienced that last week with a simple text that read: “Dead stick landing tonight." The text came from one of my closest friends, Paul Morel. Paul isn’t one for drama, but this took understatement to a whole new level. I was anxiously tapping his name on speed dial in seconds.
Image courtesy of Jeff Simon

Paul was flying his Kitfox about 15 miles out from his home base at Mallard’s Landing, a Disney-esque airpark south of Atlanta that lets pilots truly “Live the Dream.” As Paul was flying, he noticed the engine seemed to be getting louder. His first thought was that it might be the ANR in the headset turning off, but he quickly confirmed that something wasn’t right with the aircraft.

A brief check of the panel and controls revealed that the throttle was unresponsive. He reached under the panel and confirmed that one of the two throttle cables had broken. Rotax engines have two independent carburetors that must be controlled simultaneously, thereby requiring two cables. The remaining cable was severely frayed and failed completely as soon as he pulled on it to see if it was workable.

Fortunately, the engine setup was designed to keep the engine running with a failed cable. Paul made it back to the airport and radioed the situation, and the other aircraft quickly cleared the pattern to make way for his emergency landing. Having no control over power and not wanting to overshoot the runway, Paul positioned the aircraft at pattern altitude, cut the engine, and glided to a safe landing.

Knowing how fastidious Paul is about maintenance, I was extremely interested in the cause of the failure and why the progressing wear wasn’t discovered during routine maintenance. The answer was that one of the cable fittings had seized and lost its ability to rotate to accommodate routine movement of the cable. The end result was that every movement of the throttle caused the cable to bend around a sharp edge until it ultimately failed.

The more important question was why the seized joint wasn’t discovered until it caused the catastrophic failure of the cable. The answer is that the cable must be inspected “in action” in order to identify the issue. That’s not an easy task for one person to accomplish alone. For most maintenance shops, this isn’t an issue because they routinely grab the nearest able body within shouting distance to move controls in the cockpit, while the inspecting mechanic observes the system in action at all the critical points in the system.

Having those extra hands is a luxury that most owners don’t have when working on their own aircraft, and it’s even more important for owners of experimental aircraft, who typically perform their own inspections. Many maintenance tasks can be easily accomplished by a single person, but there are certain things for which having a second set of hands and eyes is more than just helpful; it’s critical.

Let’s learn from stories such as Paul’s and adopt the following maintenance rule: Any time that you are working on or in the vicinity of flight controls or engine controls, enlist a helper for the final inspection before returning the aircraft to service. Have him or her manipulate every control through its entire range of movement while you observe the system from beginning to end for binding, interference, security, and proper operation. This maintenance rule applies during inspections, but also after any work that could possibly cause something to shift behind the panel or under the cowl that could infringe on other moving parts.

Take the time to track down the help that you need. It might cost you a beer or two, but it could save you from big trouble down the road. Happy Flying!

Jeff Simon

Jeff Simon

Jeff Simon is an A&P, IA, pilot, and aircraft owner. He has spent the last 17 years promoting owner-assisted aircraft maintenance and recently certified the FlexAlert Multifunction Cockpit Annunciator. Jeff is also the creator of SocialFlight, the free mobile app and website that maps over 20,000 aviation events, $100 Hamburgers, and educational aviation videos www.SocialFlight.com.
Topics: Maintenance

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