Let me tell a little story…
First, the plane:
It’s a 1976 Cessna 172. 8,352 hours, used regularly as a trainer, but generally well maintained.
But on the left flap actuating rod, right adjacent to the jam nut, there’s a hairline fracture that would need a magnifying glass to see. Its the result of more than one overstress as a student has put down flaps above Vfe. The crack is about 3/4 of the way through the rod and about to let go. In fact, its going to fail on the very next flight, as the flaps go from 10º to 20º, and the split flap situation it causes will roll the airplane left at about 30º/second.
Second, the pilots:
Bob was one of my students. From the first touch and goes, we only applied flaps in straight and level flight - 10º on downwind, 20º on base and full flaps on final with the field made. I emphasized it was safest to deploy flaps when level, and to plan his patterns to do so. I explained that while split flaps were extremely rare, they can and did happen and if they ever did, he’d be more likely to recognize what was going on and deal with it if the uncommanded roll began from wings level. Anyway, it became a habit, which was my intention, and now with 550 hours he no longer even really thinks about it.
Carol was not a student of mine. Though she was taught a similar use of flaps in the pattern, her instructor never really emphasized that there was any specific reason she only deployed flaps while on a leg in the pattern, and not while turning. Now, with 1,200 hours she pretty much puts down flaps whenever and wherever in the pattern she feels like it, and has the skill to do so. Just not an issue, and not worth worrying about.
Finally, the fateful day.
Bob has just rolled out on base, is in a good position and altitude and reaches for the flap switch to go to 20º. The right flap obediently goes to 20º right as the left flap control rod fails and the left flap retracts completely. In the two seconds of “deer in the headlights” adrenaline-spiked delay, the 172 has rolled 60º left into a 60º bank. He finally responds by pushing forward and applying opposite aileron, which stops the roll and seems to barely be decreasing the bank. Finally it dawns on him to undo the last thing he did and he retracts the flaps, regaining normal control. Whew! He leaves the flaps alone, gets back in the pattern and makes an acceptable no-flap landing and taxis in with the left flap dangling free. What a story!
Carol, like Bob, put down 10º of flaps on downwind. Now, as she rolls into her typical 30º bank for the turn to base, she figures its a good time to deploy the next “notch” of flaps. The right flap obediently goes to 20º right as the left flap control rod fails and the left flap retracts completely. In the two seconds of “deer in the headlights” adrenaline-spiked delay, the 172 has rolled 60º left into a 90º bank. This is not something she has ever seen before - the 172 in knife edged flight on its way to being inverted. She responds reflexively, kicking right (top) rudder while pulling back on the stick - as most pilots untrained in aerobatics will do when inverted. The airport security cameras catch it all, and the NTSB report mentioned some combination of “Split-S” and “Snap Roll/Spin” in the accident report. No need to mention that it was a fatality.
The above scenarios are not being put forth for the benefit of the grizzled, high time pilots who have been doing what they’ve been doing, one way or another, for decades and thousands of hours. I know all about old dogs and new tricks, and how anyone chooses to fly does not really impact me one way or another.
But I would advise any prospective, student or new pilot to carefully consider the above scenarios and how you might respond to each. And to look carefully for the well reasoned argument that deploying flaps in turns is somehow necessary. Cropdusters and airliners and specific cases aside, I just have not heard any convincing argument.
But That’s Just Me!™
