We begin a series on preventing loss of control in flight with a look at stalls. How do they happen? How can you avoid them?
The FAA's #FlySafe campaign, is an endeavor to educate pilots about best practices for operating within their aircraft's performance limitations. A major component to this campaign is preventing loss of control in flight, or LOC-I accidents. This works in tandem with the NTSB's 2017-2018 "most wanted" list for areas of aviation that require critical changes to reduce accidents. Preventing LOC-I has made the list for the third year running, playing a role in around 48% of fatal fixed wing general aviation accidents.
As part of a four-part series, we’ll dive into how LOC-I happens, how to prevent it, and how to react if one occurs. For part 1, the focus is on stalls, the most common cause of LOC-I.
While you'll often hear or even reference the term "stall speed," stalling is less a function of speed than it is of angle of attack--the angle between the chord line and the relative wind. You'll know from your training that air flowing smoothly over the tops of the wings is required for an airplane to stay in the air. When AOA increases above a certain point for a certain speed (critical AOA), the wind can no longer flow easily over the wing and a stall occurs.
It is possible to stall an aircraft at any airspeed, attitude, or power setting. A stall warning horn will often alert a pilot to an impending stall, allowing a brief window for recovery before a full stall, but you can't always rely on the horn. Other signs of imminent stall include:
- Increased aircraft reaction time to control movements
- Larger control movements required to net desired aircraft response
- Buffeting, rolling, or vibrations (right before the stall occurs)
- Change in the sound of the air flowing along the aircraft
The best defense against stalls is pilot awareness: focus on flying the aircraft at all times. This is especially true during takeoff and landing, as low-altitude stalls are both the most common (due to increased workload) and the most dangerous (due to limited recovery time). Keep an eye on the instruments, know your aircraft limitations and thresholds for critical AOA, and make changes in power or pitch as needed to prevent stalls before they happen. Make a habit of checking the AOA indicator, if equipped, as it can provide specific information as to if you're trending toward a stall.
Mind over matter
Stall recovery can involve many different factors, depending on the situation under which a stall is entered. There are, however, a few basic principles that apply to all scenarios. The first and foremost goal is always to reduce the AOA. You may be inclined to prioritize increasing power or maintaining your altitude in a moment of panic, but this does nothing for you if you remain at critical AOA. This almost always means reducing pitch to restore normal airflow over the wings.
Once the stall warnings have been eliminated, you can then address the remaining problems, such as rolling the wings level, adding power smoothly as necessary, or retracting speed brakes. It is not recommended to perform a stall recovery with the autopilot on, as the autopilot may cause undesirable changes to controls or trim. If autopilot is engaged; turn it off prior to beginning stall recovery.
It is recommended that pilots seek out additional training in stall recognition and recovery with a flight instructor skilled in such techniques. Experiencing and recovering from stalls in controlled conditions can help you react appropriately in the event of an unintentional stall.
We'll dive deeper into LOC-I recovery techniques in Part 4 of our series on LOC-I. Next week, check back for Part 2 of 4: LOC-I caused by spatial disorientation.
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