In the final minutes of the flight, the aircraft’s altitude and pitch began to fluctuate. Data from the investigation later showed the aeroplane climbing and descending in increasingly pronounced oscillations. What may have started as a manageable control issue quickly became unstable, with each overcorrection appearing to worsen the aircraft’s movement rather than settle it, resulting in pilot-induced oscillations (PIO) leading to an uncontrollable aeroplane
In December 2023, pilot and aviation content creator Jenny Blalock, known online as “TNFlyGirl”, was flying her high-performance Beechcraft Debonair (BE33) when the aircraft crashed in Arkansas, killing both her and her father. Like most aviation accidents, the investigation looked at a range of possible factors. But one element that stood out in the flight data was the sequence of pitch oscillations during the final stage of the flight.
For many instructors and experienced pilots reviewing the accident, those oscillations raised a familiar topic: aircraft control, trim management, and how quickly a situation can escalate when an aeroplane becomes unstable.
Trim is one of the first concepts introduced in flight training. Rather than constantly holding pressure on the controls to maintain a pitch attitude, the trim system allows the aircraft to balance itself so that only minimal input is required from the pilot. When properly trimmed, the aircraft feels stable and predictable, allowing the pilot to focus on navigation, communication and situational awareness.
Flight instructors often summarise this with a simple phrase: trim until the aeroplane flies itself.
In calm training conditions, the idea seems straightforward. But when workload increases, or something unexpected happens in flight, trim becomes far more important than many pilots realise.
If an aircraft becomes significantly out of trim, the pilot may find themselves applying constant pressure to the controls just to maintain level flight. That extra workload can make even small corrections more difficult. Instead of smooth adjustments, pilots may begin applying stronger control inputs simply to counteract the forces they feel.
This can lead to a situation known as pilot-induced oscillation.
Pilot-induced oscillation occurs when a pilot’s corrections unintentionally amplify the aircraft’s movement rather than stabilising it. The aircraft pitches away from the desired attitude, the pilot corrects, the correction overshoots slightly, and the pilot reacts again. With each cycle, the oscillations can grow larger.
An aircraft that is badly out of trim can make this more likely because the pilot is already applying significant pressure on the controls. When that pressure exists, it becomes easier to overcorrect.
The flight data from the Blalock accident showed that the application of trim in the incorrect direction, out of phase, caused increasing pitch oscillations in the aircraft’s final moments. For many instructors, discussing the accident afterwards became a reminder of how quickly control issues can escalate when the aircraft becomes unstable, and workload rises.
Whilst the autopilot in the accident aircraft did not include automatic trim, many modern cockpits do, which adds another layer to this discussion. Many general aviation aircraft now use autopilots that automatically adjust trim while maintaining altitude or pitch. While this reduces workload, it can also mask what the aircraft is doing behind the scenes.
If the autopilot disconnects while the aircraft is significantly out of trim, the pilot may suddenly experience strong control forces that require immediate correction. If that surprise occurs at a moment of high workload, the situation can quickly become more difficult to manage.
For this reason, instructors often stress the importance of staying comfortable flying manually and understanding how the aircraft’s systems interact with trim.
One of the most useful habits a pilot can develop is recognising when they are fighting the aeroplane. If maintaining level flight requires constant pressure on the controls, something is not balanced properly. In many cases, the solution is not more control input but a simple adjustment to the trim.
It is one of the earliest lessons taught during flight training: establish the desired attitude, trim away the pressure, and allow the aircraft to stabilise.
Accident investigations exist so the aviation community can learn from events that ended tragically. They are not about assigning blame but about understanding the chain of events and identifying lessons that may prevent similar accidents in the future.
For pilots and instructors, discussions following the Blalock accident reinforce a familiar message: the fundamentals still matter. Skills that seem basic during early training remain critical throughout a pilot’s career.
Trim may appear to be a small control in the cockpit, but its role in maintaining stability and reducing workload is fundamental. When used correctly, it allows the aircraft to remain balanced and predictable. When neglected, it can contribute to situations where the pilot begins fighting the aircraft rather than flying it.
In aviation, small details often make the biggest difference. If you’re using automation and you find yourself behind the aircraft, disconnect and fly the aeroplane manually: Aviate – Navigate – Communicate.
