You're rolling into a steep turn, and you feel yourself pressed into the seat. It's not just you feeling it. Your airplane is too. It's called load factor, and here's how it works.

What Is Load Factor?

Load factor is the ratio of lift to weight, and it's measured in Gs. A load factor of 2 means your aircraft is producing twice as much lift as its weight. That causes you, and the airplane structure, to experience a 2G load.

There are two reasons it's important to understand load factor. First, it's possible to structurally overload your aircraft, causing it to bend or break. Second, as load factor increases, so does your stall speed. That means you can stall at speeds well above your published stall speed.

How Aircraft Are Designed for Load

Aircraft designers can't build for every possible extreme. Instead, they design around what's called a "limit load factor," which is the highest load the aircraft is expected to see in normal operation. The FAA sets these limits based on the aircraft's category:

• Normal: 3.8Gs
• Utility: 4.4Gs
• Acrobatic: 6.0Gs

You can find your aircraft's certification category in the AFM/POH and often on cockpit placards. For most GA training aircraft, they're normal category planes.

On top of the limit load factor, the FAA requires a 1.5x safety factor. That means a normal category aircraft must be able to withstand up to 5.7Gs before structural failure.

But here's the important part: that buffer exists to protect you when you encounter something unexpected, not to give you extra room to push the aircraft harder.

What Happens in a Steep Turn

Steep turns are one of the quickest ways to add load factor, and the numbers climb fast once you pass 45 degrees of bank.

At 60 degrees of bank in a level turn, you're pulling 2Gs. At 80 degrees, that jumps to 5.76Gs. That's close to the limit load factor of an acrobatic aircraft, and well beyond what a normal category airplane is built for.

For most GA aircraft, 60 degrees is as far as you want to go. According to FAR 23.2005(d)(2), "airplanes not certified for aerobatics may be used to perform any maneuver incident to normal flying, including lazy eights, chandelles, and steep turns, in which the angle of bank is not more than 60 degrees."

So what does load factor have to do with stall speed? Stall speed increases in proportion to the square root of load factor.

You can see from the diagram above that as load factor increases, stall speed increases at an increasing rate.

Here's a real world example that you could experience on your next flight: a 60 degree banked turn produces 2 Gs of load factor. And since the square root of 2 is 1.41, that means that your stall speed will be 41% faster in a 60 degree, constant altitude coordinated turn than it would be in straight and level flight.

Putting It All Together

Load factor is what your aircraft's structure carries, measured in Gs. Your airplane was designed around a limit load factor for its category, with a 1.5x safety factor on top of that. In steep turns, that load factor builds faster than you might expect. Keep your bank reasonable, know your limits, and never exceed the limit load factor of your plane.