A Bad Split

It stands to reason that the goofiest stuff that you will ever experience as a pilot will usually come at the moment you are least prepared for it. As if it was some cosmic joke, minor failures in our aircraft systems cause extreme problems if we aren’t thinking of what the consequences could be.

Our intrepid pilot was out for a bit of VFR fun and adventure in his light single. The weather was fair, and there wasn’t a cloud in the sky to obscure his CAVU day, as he wended his way along the east coast of our country.

Our pilot was thinking that days like this don’t come along often. Too many times these days his view has been obscured by pollution or by the smoke of forest fires, or just a lousy inversion layer that created a fuzzy haze over the entire area. But not today! The cool, northern wind had blown that all out to sea, and with it his troubles.

His trusty fuel computer told him he had an hour and change of reserves on board, which despite being well within the safety limits required by the FARs, was approaching his more conservative, personal limits. Thus, he set his course for the nearest airport in his path, which had a nice long strip to land on.

The non-towered field was not very busy, and our pilot made the usual Unicom announcements regarding his position and intentions. As he slowed to his gear speed, he reached over and flipped the gear switch down. He watched as the gear indicators headed in the right direction, and the lights came on indicating that his gear were down and locked.

He then slowed the plane down a bit more to nearly within the flap speed. NEARLY was the key word here — he was still a few knots above it, and knew that the plane should be able to handle it. He pushed the flap selector to 15 degrees, and watched the indicator move…

As the flaps approached 15 degrees and stopped, the plane rolled hard turn to the right. Our pilot cranked in full ailerons to get the plane back on course, and increased power. A look out the window quickly revealed his problem — the left flap had deployed, but the right flap had stayed retracted!

The plane was cross-controlled, and the flap was bigger than the aileron. He worried about what would happen as the airspeed dropped, and whether he would be able to maintain control. He knew he had to get the split-flap scenario corrected, but wasn’t sure how to do it the right way.

With his knowledge of the plane that he had learned at a Service Clinic held by the type club for his model, he believed he had a broken flap cable on the right side. Based on this information, he decided the best course of action would be to carefully try to raise the flaps back to the full up position, to clear the flap.

He bumped the flap control up and watched BOTH flaps carefully — the right flap stayed up, and the left flap retracted. As the left flap came up, he eased off the aileron pressure, and got the plane back into straight and level flight.

Shaken by the challenge and the adrenaline rush that came with it, our pilot was now toasty… yet slightly moist. He got out his POH, and looked for guidance on no flap landings, and finding none, looked up the clean stall speed for the plane. He then added five knots for good measure, and made his approach, ready to go around if he wasn’t able to make the runway. The winds and luck were with him, and he was able to safely land.

THE PITFALLS OF PREVENTATIVE MAINTENANCE Our pilot had actually been proactive in his maintenance. He had elected to replace both flap actuator cables during his last annual inspection. His old cables were over 40 years “young,” and he wanted to improve the reliability of his plane. In a classic case of the misguided ‘if it ain’t broke don’t fix it,’ the new flap cables had been made incorrectly. Plus, his plane was one of the first to experience failures, so no service bulletin or AD had been issued. Our friend got lucky — he caught this one in VFR conditions, with a clear horizon right in front of him. If he was in the soup on an instrument approach, the sudden attitude change could have had significantly greater consequences.

If there is a single control surface on your plane that is bigger, you have an exception to the rule. A big control equals a big force for you to encounter, which means finding this problem early would have minimized the surprise, and allowed for a prompt recovery.

Know how your flaps work. Are they cable actuated, or hydraulic? Does an electric motor drive them, or a simple handle? Know what makes your flaps move, and what their fail-safe position is. This knowledge can help to get you out of a split flap situation almost as fast as you can get into one — if you KNOW how your flaps work.

BOTTOM LINE: New parts don’t always mean no problems. Any time you change anything on your airplane, consider yourself a test pilot. You can’t tell when the start of a manufacturing run is, or when a supplier changes. If you are the first one to find a problem, it can be a real surprise. Keep your eye on new components, and EXPECT PROBLEMS. As a personal suggestion, we recommend that you try not to take that first test flight on a hard IFR day. We often take for granted the operation of our many aircraft systems, extending and retracting our flaps deserves more attention.