Lessons from a loop

In contrast, I often merely talk a student through her first loop in my Cessna Aerobat: commence a shallow dive over a long road to achieve the appropriate entry speed, pull back on the yoke and look to the side when the horizon is no longer in sight, add power heading straight up, ease off the back-pressure along the top to silence the stall warner, look at the ground through the skylights to ensure we’re still parallel to the road, retard the throttle when headed straight down, and pull back once more on the yoke to establish a V_Y airspeed climb. The loop should feel smooth and effortless and a student’s first is often a good one. It’s gratifying to see success early on.

My affection for the loop goes beyond its proper place on a pilot’s bucket list of fun adventures. The procedure above contains two subtle yet important safety lessons for everyday flight. But first, I’ll share a frustrating conversation that happens on practical exams and why loops can drive the proper message home.

“How do you recover from a stall?” is a question I often pose to candidates and “Add full power and push the nose down to the horizon” is a typical reply. “OK, then what is the corrective action if the stall warner sounds but the nose is below the horizon?” After a long pause and furrowed brow, the candidate replies, “Add full power and bring the nose to the horizon” while using his hands to simulate pulling back on the yoke.

I shudder when I imagine this is how the pilot in the 2009 Colgan Air crash might have responded to the same query. During that landmark accident, the captain, who was the pilot flying, was on an instrument approach into Buffalo, New York, and as the airframe picked up ice during the descent, the angle of attack increased until the stick-shaker warned of an impending stall. Instead of pushing forward to recover, he pulled back on the control column and used ailerons to counteract a dropping wing, sent the airplane spinning to the ground and thereby sealed the fate of 50 people who perished in the accident.

Even flight instructor candidates struggle to imagine that an airplane’s wings can be stalled with the nose below the horizon. (That’s especially surprising as these candidates have earned a spin endorsement during which the aircraft wings are stalled, despite a view of the ground that fills the entire windscreen.) Indeed, the way that we practice and demonstrate stalls on a practical exam often isn’t how the inadvertent ones happen. Hearing the stall warning blare while the aircraft nose is below the horizon can be confusing and pilots find pulling back on the yoke a compelling, albeit incorrect, way to stay away from the ground.

Over the years, I’ve heard misunderstandings about the connection between stalls and the horizon on countless practical exams. During a week that I spent at a single flight school, I listened to the same explanation from most of the candidates. I asked one of the flight instructors why their students uniformly provide the same wrong, and dangerous, procedure and he explained, “Well, it’s in our standardization manual.” Sure enough, he showed me that the manual’s stall recovery procedure stated that the nose should be lowered to the horizon.

I asked a flight school administrator about removing “horizon” from the reference and he shared his reticence to do so. There had been multiple cases of students landing in a nose-low attitude that ended up with a prop strike and even shearing off the nose wheel of their trainers. They surmised that the students felt they were about to stall and shoved the nose forward aggressively. Of course, I can’t say for sure but after flying with thousands of practical exam candidates, I very much doubted their conjecture’s truth. Of all those, I have advised just two that I believe approached too slowly on final. The grand majority fly the final approach segment with too much energy (see “Flare is Not a Four-Letter Word”, June 2020 AOPA Pilot) and a pilot-induced oscillation is the more likely culprit. It took several conversations, but they finally excised “horizon” from the stall recovery procedure.

We’re now ready to return to the loop and discover its messages.

Pitch angle and angle of attack are unrelated. In performing a loop, a pilot sees every pitch attitude of which an airplane is capable. But at no time during a properly flown loop does the airplane ever stall. The loop demonstrates that it often doesn’t matter where the horizon is.

No matter what attitude, the antidote to a stall is pushing forward on the yoke. Stalls can happen during a loop when the pilot pulls too aggressively. During the period between the nose pointing straight up and inverted flight, for example, the stall warner is sounding and releasing the back-pressure will silence the horn. Not doing so can result in a stall/spin from the top of the loop. With sufficient altitude, one could pretend that it was intentional. Spinning from a loop is fun and you’ll even see it at airshows. Pulling too hard at any point during the loop can lead to a stall but the proper recovery procedure is the same. (See above.)

Pilot candidates can usually recite the saying that an airplane can stall in any attitude and at any airspeed but it’s clear that few internalize that fact. Considering, and better yet flying, a loop can send that lesson home in a fun and memorable way. 

Catherine Cavagnaro teaches aerobatics at UOS and is the Gaston Swindell Bruton Professor of Mathematics at Sewanee: The University of the South.