Rushed runup, wind shift preceded power loss on takeoff

ADS-B data and recorded radio traffic suggest the pretakeoff checklist may have been interrupted, abbreviated, or skipped. A quartering tailwind that developed in the minutes before departure may have further complicated the pilot's effort to cope with the emergency once airborne.

At least one witness told local media that the aircraft's engine sounded like it was running intermittently in the seconds before impact, and the aircraft hit the ground (likely in a vertical or near-vertical dive) about 900 feet from the runway. Witnesses who rushed to the scene found the aircraft wreckage engulfed in flames. A traffic camera captured a black mushroom cloud billowing up from the distant impact.

The tower controller at Crystal Airport in Minneapolis cleared the Bonanza for takeoff at 11:50 a.m. Central time, which the pilot acknowledged before beginning the takeoff roll. ADS-B data show the aircraft lifted off from Runway 32 just after passing Taxiway A and was about 90 feet above the right edge of the runway less than a minute later when the pilot made a final transmission. The recorded radio call was distorted, but he appears to have said: "Abort abort Three-Two-X-"

The tower controller, who would have had a clear view of the departing aircraft, responded almost instantly: "Three-Two-X-Ray wind, ah, cleared to land any runway, cleared to land any runway or surface, altimeter three-zero-zero-two."

About 10 seconds later, the Bonanza impacted the ground in a wooded park next to a residential neighborhood and burst into flames. Authorities, colleagues, and family members confirmed the deaths of the pilot, Dr. Joseph Cass, a retired Mayo Clinic orthopedic surgeon, and his partner, North Dakota state Rep. Liz Conmy.

The sequence of events reconstructed from timestamped radio calls recorded by LiveATC.net, and ADS-B data captured by Global ADS-B Exchange, point to two factors that may prove significant: a potentially rushed departure with several other aircraft operating on and around the airport, and a wind shift that happened minutes before takeoff.

Cass initially called ground control at 11:40 a.m. local time to request an IFR clearance for a planned 50-minute trip to Park Rapids Municipal Airport/Konshok Field in Minnesota. The weather in Minneapolis an hour before departure included calm wind, with few or broken clouds at 11,000 feet and 10 miles visibility. A weather front passed the airport while the Bonanza was waiting in line to take off, and the tower advised a landing aircraft the wind was "zero-seven-zero at four" at 11:47 a.m. The next routine weather observation—at 11:53 a.m., two minutes after the accident—included wind from 160 degrees at 6 knots, clearly favoring the opposite-direction runway. Departing the 3,751-foot main runway with a slight quartering tailwind became more aeronautically significant as the airplane struggled to maintain airspeed after takeoff, turning downwind and approaching trees.

Cass, a commercial pilot with an instrument rating who earned his certificate after retiring from the Mayo Clinic in 2017, may have been in a rush to get in the air. He reported "ready to taxi" at the conclusion of his IFR clearance readback, and made a wrong turn from Taxiway A onto a non-movement area (Taxiway E on the airport diagram), one intersection short of Taxiway G.

The Bonanza stopped at the end of Taxiway E, still short of the designated runup area, at 11:43:38 a.m.; Cass contacted the tower controller 40 seconds later and advised that the flight was "ready to depart whenever there's an opening."

Cass was evidently confused about his precise location, and moved up to the runway hold short line following a second request from the tower just after 11:48 a.m.

At 11:49:40, the tower controller directed the Bonanza to line up and wait on the runway, with traffic on the downwind leg. The tower cleared the Bonanza for takeoff at 11:50:10, which the pilot acknowledged, and the Bonanza began its takeoff roll immediately.

At no point during the sequence of events from the conclusion of the (wrong-surface) taxi route to the departure was the aircraft stationary for more than a minute. A pretakeoff check of magnetos, propeller, primer, fuel pump, fuel tank selector, and engine instruments in a single-engine piston airplane typically requires at least that long, often longer, even for a pilot flying a familiar airplane. Preparing for an IFR flight adds a few other tasks to the list, including programming the navigation system and radios, which pilots often delay until after receiving their IFR clearance to avoid having to adjust the route, though the accident flight was cleared as filed.

After liftoff, the Bonanza's groundspeed increased to 100 knots over a 1,300-foot span between recorded ADS-B data points. Cass announced "abort" as the Bonanza passed the runway numbers at about 90 feet agl, and climbed to a maximum of 158 feet agl as the aircraft began a left turn, though it never accelerated. The final data point was recorded within roughly 300 feet from where the aircraft impacted the ground. The Bonanza covered 150 feet in the air between the final two ADS-B data points at 49 knots, a few knots slower than the published stall speeds for that model, and probably with a tailwind.

Takeaways

Never rush (or skip) a checklist. A thorough preflight inspection will uncover many common causes of engine failure before flight. Proper execution of the pretakeoff checklist offers pilots a final opportunity to detect powerplant problems before takeoff. A rushed pretakeoff routine invites errors, oversights, and omissions. "Mismanagement of the engine control systems by the pilot continues to be a leading cause of engine failure," notes FAA Advisory Circular 20-105C. "Despite improvements in engine design and performance over the years, a review of the [NTSB] database shows that powerplant system malfunctions remain the defining event for personal flying accidents."

Maintain situational awareness. It's not clear if the pilot of the April 25 accident flight was aware that the wind was no longer calm, but had shifted to a quartering or possibly a direct tailwind, by the time he began the takeoff roll. Tailwind takeoffs in light wind conditions are not necessarily unsafe, though the ability to maneuver the aircraft is further reduced in the event of an engine failure.

Prime your mind. Power loss on takeoff is one of the most unforgiving emergency scenarios, because there is very little time to react before the airplane slows below stall speed. Professional crews (and conscientious GA pilots) conduct a detailed takeoff briefing that includes various decisions made in advance of various contingencies, with emphasis on abort points and minimum altitude that should be reached before attempting a turnback. A simplified version of this for GA pilots is to say, out loud, "there it is—push" to prime a quick and correct response to a loss of power during takeoff or initial climb.

Pitch for airspeed, even when close to the ground. Aerodynamic stalls are among the least survivable results of power loss on takeoff. While the pilot of the April 25 accident flight had few, if any, good options to land immediately after departing an airport surrounded by residential and commercial development, almost any scenario involving a controlled landing—to include into the canopy of a tree—is more likely survivable than a low-altitude stall.

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