Turns and load factor

What makes an airplane turn

When you bank, the lift vector tilts. Part of the lift now acts sideways (the horizontal component), and that's what pulls the airplane around the turn. The rudder doesn't turn the airplane; it keeps it coordinated.

Because some lift is now pulling sideways, less is holding the airplane up. To keep your altitude, you have to increase total lift by adding back pressure (a higher angle of attack). That's why you pull a little as you roll into a turn, and release as you roll out.

Load factor

Load factor is the ratio of the load on the wings to the airplane's weight, measured in Gs. In straight-and-level flight it's 1G. In a level turn it increases with bank angle:

Past about 45°, load factor climbs very quickly. At 60° your wings carry twice the airplane's weight.

Stall speed goes up in a turn

Stall speed increases with the square root of the load factor. At 2G (a 60° level turn), stall speed is about 41% higher. If your airplane stalls at 50 knots straight and level, it stalls around 70 knots in a 60° turn. This is why low, steep, slow turns (like an overshooting turn to final) are so dangerous.

Limits and maneuvering speed

Airplanes are certified for limit load factors. A normal category airplane is designed for +3.8G and -1.52G; a utility category airplane for +4.4G and -1.76G. The design maneuvering speed (V_A) is the speed below which the airplane will stall before it exceeds its limit load. V_A decreases as weight decreases, so a lightly loaded airplane needs to be flown slower in turbulence.