That's Stall Folks
Words: Nick Jones
You might have heard of stall warning devices, but if you have never flown with one in RAAus you are not alone. At present, many light aircraft are simply not fitted with them. Let’s dive in and understand exactly they are, how they work and how they can help improve safety in aviation.
In many GA Aircraft and just about all commercial planes, there is a small device installed that when the plane is getting close to a stall (around 5 - 10 knots from stalling), they will alert the pilot. Some will have an inbuilt verbal alert, especially aircraft with glass panels. Many GA planes have what is known as a ‘stick shaker’ which is a device that adds a vibration to the yoke when it is approaching a stall. But most commonly, in lighter aircraft, is the stall horn or electronic equivalent. It varies between devices, but generally as the plane gets closer to stalling either the pitch will change or the stall beeping will become more frequent, not that dissimilar to the sound of a metal detector.
There are three main kinds. The horn, lift detector stall warnings and Angle of Attack (AoA) sensors. The first of these created, and by far the simplest, is the stall horn. It is just a small opening that sits on the leading edge of the wing, which acts more or less like an umpire whistle. As the wing approaches a stall, the location where the air splits around the wing shifts. This ingenious little device takes advantage of the shift in air pressure and direction, triggering the whistle to via a tube that comes out of a horn, which amplifies the sound into the cockpit. When fitted, it’s the last thing you’ll hear before touching down on the runway.