The pilot, 40, was an instrument flight instructor and held a commercial certificate, with airplane single-engine and multiengine land ratings and an instrument rating. He had something over 1,400 hours and made his living giving flight instruction. His logbook displayed the required endorsement for “training stall awareness, spin entry, spins and spin-recovery procedures.” He mostly flew a Cessna 172, but he had recently administered a flight review in a Stearman. I will call him Jack—not his real name.
In July 2019, Jack bought a homebuilt Poberezny Acro Sport II from its builder. A small two-seat tandem biplane designed by the late founder of the Experimental Aircraft Association, Paul Poberezny, the airplane had a 160 hp Lycoming engine, a gross weight around 1,500 pounds, and a wing loading of 10 pounds per square foot. It would be expected to be a lively performer. Naturally, it’s a taildragger. Jack, his uncle and some friends brought it, disassembled, to his home field, where they reassembled it over a couple of weeks.
On August 9, a Thursday, Jack made his first flight in the Acro Sport, taking it once around the pattern. After landing, he taxied back to his hangar, spun the airplane around three times, and shut it down. The engine ran like a million bucks, he told his uncle, who was watching, and the controls were very responsive. He was happy with his purchase.
A pilot with whom Jack shared hangar space talked with him on Friday. They discussed the first flight, and the pilot asked, out of curiosity, what the Acro Sport’s stall speed was. Jack replied that he didn’t know because the airspeed indicator was out of view, and he couldn’t see it while piloting the aircraft in the rear seat.
Like other small tandem-seat biplanes, the Acro Sport is flown solo from the rear seat. The instrument panel is in the rear cockpit; typically, a rudimentary panel—consisting of airspeed, altimeter and little else—might be provided in the front cockpit as well. Most likely, what Jack meant was not that he could not see the airspeed indicator from the rear seat, but rather that during the landing, when the view forward is blocked by the long front end of the airplane and one orients by peripheral vision, there is no time for looking down at the instrument panel to check the speed at touchdown.
Jack invited a friend, who was also a pilot and had built his own experimental Kitfox, to go up with him on his next flight. On Saturday afternoon, they took off from Runway 27, flew a wide circle, and returned for a fast pass over Runway 9 at 150 feet, followed by a zoom climb.
There were several witnesses, and their accounts coincided. One witness had talked with Jack before the flight, and the man and his son stayed to watch. The man thought the engine was running at full throttle during the pass. He said that the biplane went straight up in the air about 500 to 600 feet before its left wing dropped and it made two or three “spirals down” before hitting the ground.
A woman who was sitting at her campsite a quarter-mile from the end of Runway 9 saw the airplane “going almost straight up in the air.” She thought to herself, “Wow, he is really climbing very steep.” Then she saw the left wing quickly dip down and the airplane go almost, but not quite, straight down.
Another witness mistook the drop of the left wing for a deliberate maneuver and said, “He doesn’t have enough space to do whatever he’s doing.” Moments later, he heard the thud of the impact.
All of the witnesses hurried to the site of the crash, 100 yards from the end of Runway 9. They found both pilots dead in the wreckage.
The National Transportation Safety Board investigators performed the usual checks of control continuity and engine functions, and they found nothing amiss. It was difficult to escape the obvious diagnosis: Jack had stalled out of the zoom climb and had not had enough height to recover from the ensuing spin.
- Read More from Peter Garrison: Aftermath
While NTSB “probable causes” are seldom, if ever, models of elegant English prose, they do contain some nuances. This one blamed “the pilot’s decision to conduct low-altitude aerobatic maneuvers which resulted in an exceedance of the airplane’s critical angle of attack while maneuvering at a low altitude, which resulted in an aerodynamic stall.”
Clearly, the airplane had stalled, and the low altitude had not permitted a recovery. The steep climb was by definition an aerobatic maneuver because it exceeded the parameters of “normal flight,” which are understood to be 60 degrees of bank and 30 of pitch. The statement could have begun, “The pilot inadvertently exceeded the airplane’s critical angle of attack while maneuvering at low altitude…” The nuance was in the word “decision,” which made the basic error one of judgment rather than ship handling.
What the probable cause surprisingly failed to mention was the pilot’s lack of familiarity with the airplane. He had flown it only once before, briefly, just around the patch. He was not used to its light-stick forces. He had not stalled it at all. He had not assessed its recovery characteristics, its behavior when spinning, or its propensity for, or resistance to, secondary accelerated stalls. Critically, he had not ascertained the rate at which it would lose airspeed in a steep climb. He had certainly not rehearsed the zoom climb at a safe altitude—in order to be sure that he knew when to pitch over and what would happen if he were late doing so. He did not know how the addition of a passenger in the front cockpit would affect the airplane’s behavior and performance. In just about every sense you could think of, he and the airplane were strangers to one another.
I have not flown one myself, but I asked a friend who built an Acro Sport II and flew it for a number of years what he thought of the airplane. “Not for the fainthearted” was his reply. But Jack’s first flight had gone off without a hitch, and he evidently felt comfortable in his new ride. Why should he expect trouble on a second flight?
Somewhere between faintheartedness and bravado, there is a region where joyful abandon meets rational discretion, and they fall in love and get married. It is there that pilots ought to dwell. Not all will; the hero in us clamors to be let out. But if time could be rewound like a tape, and Jack could replay the decision that cost him and his friend their lives, he would most certainly say this time: “Yes, I’ll be happy to take you up, but first let me get a couple of hours in the airplane. We barely know each other.”
Too Much Zoom
Among the pleasures of low passes and zoom climbs is that of putting on an impressive performance. In March 2015, the pilot of an American Champion Decathlon made a low pass over a lake while friends watched from a nearby beach. The pilot was grinning from ear to ear, one witness reported, and the passenger was waving. At the end of the lake was a stand of 50-foot trees which the Decathlon should have had no problem clearing; but either because the distracted pilot waited too long to begin his climb or because he climbed too steeply or pitched over too late, the Decathlon stalled, rolled left and crashed.
It may be that Jack’s accident and that one have in common not only a desire to entertain and impress watchers on the ground—a common and harmless enough impulse in itself—but also an unconscious reluctance to appear timid by ending the maneuver too soon. To be impressive, the zoom must not appear too cautious, but to end well, the low pass must not go on too long. In the pleasurable excitement of the moment, a pilot may cross the line where fun turns to folly.
This story appeared in the August 2021 issue of Flying Magazine
