# Turn rate of a jet vs. biplane

A friend and I were debating whether a biplane/propeller plane has a faster turning rate than jet aircraft. I argued that the propeller planes often do have better turning rates than jets, but I could not explain why. Does anyone know why this is?

• Did you think about the difference in stalling speeds... – Solar Mike Nov 17 '19 at 4:22
• This question might be a better fit for SE Aviation. – Fred Nov 17 '19 at 4:33

A low speed biplane will have a smaller turn radius than a jet, for the same reason that a car can make a smaller radius turn at low speeds.

For "normal" non-aerobatic flight, the standard time to make a horizontal turns is the same for all aircraft: 3 degrees per second, or 2 minutes for a full 360 degree circle. If a jet is flying at 5 times the speed of a biplane, the radius of the circle will be 5 times as big.

Low speed aircraft may use a standard turn rate of 6 degrees per second not 3, and some very large aircraft use 1.5 degrees per second. Of course if air space is being shared by different aircraft, it is easier for air traffic control to avoid potential collisions if all the planes turn at the same rate.

The maximum rate of turn is limited by the centripetal acceleration of the plane. Sustained turns above about 5g are limited by the ability of the pilot to remain conscious, but partial turns up to 9g are possible. The maximum instantaneous turn rate for a military fast jet is typically about 20 degrees per second, which would theoretically give a 360 degree turn in 18 seconds if other factors didn't prevent that from being done.

As well as the inability of the pilot to operate at sustained high g loads, the drag on the aircraft increases at very high turn rates, and the engine power may not be able to maintain constant speed, even flying a military jet with reheat. If the speed reduces too much, there is a high probability that the intended turn will become a stall or a spin.

Of course the fastest "turn" in one sense of the word is an intentional spin. Aircraft designed for aerobatics may be able to spin faster than one complete turn per second.

Long ago , the IL Air National Guard flew F51 and F84 ; at summer camp they shared the same dedicated airfield. In the distance you could see an F84 line up on a straight approach to land; Occasionally an F51 would make a 90 degree turn and land in front of the F84. When the F84 made its large turn it was so far away that you couldn't see it unless you were looking that way with binoculars. The F51 were dramatically more maneuverable than the F84 . I think it is a safe guess the a biplane is more maneuverable than an F51 , so no comparison to a modern jet. However , the speeds are rather different .