# What is the advantage of combining the rudder and brake pedals in aircraft?

I've read about several aircraft having their rudder and brake pedals very close together. To me this seems confusing and prone to error. It looks easy to mistake the rudder / brake pedals and inadvertently press the wrong one when flying or taxiing the aircraft. Since these are fundamentally important controls, this could lead to disaster.

So what is the advantage of keeping the rudder / brake pedals in this configuration? Are there any historical reasons for this design choice?

• Note that the rudder and brakes are on the same pedals, not different ones. Nothing to confuse. Apr 27, 2014 at 4:20
• There is at least one accident related to brake pedals, Crash: Yak Service YK42 at Yaroslavl on Sep 7th 2011, failed to climb on takeoff. The problem was not caused by the combining itself, but the fact that the pilots switched from different aircraft type with different pedal design and didn't get sufficient training (plus all the other holes in the cheese like poor take-off briefing). Apr 28, 2014 at 6:51

## 4 Answers

All of the aircraft that I have ever seen have the rudder and braking functions combined into one set of two pedals. To operate the rudder you press on the bottom part of the pedals, so that they slide back and forth on tracks, and to operate the brakes, you press the top part of the pedals so that they rotate towards the floor. The left pedal operates the left wheel brake, and the right pedal operates the right brake, so you can use differential braking to turn the plane. For rudder operation, the motion of the two pedals is locked together (i.e. press on the right pedal for right rudder, and the left pedal moves aft while the right pedal moves forward).

Because of the two different motions (rotation for brakes versus sliding for rudder) there isn't a problem with hitting the brakes when you want rudder or vice versa. Typical early training is to operate the rudder using your toes on the lower parts of the pedals, so and to only put your whole foot on the pedal to actuate the braking mechanism.

• In what aircraft does the rudder pedal assembly slide back and forth on tracks? Granted I don't have experience in all industry sectors, but all assemblies I have experience with are hinged, not tracked. The only tracked assembly I have come across is a PC flight simulator peripheral. Sep 4, 2016 at 13:26

Here are a few design constraints:

• Unlike a car, there is sometimes the need to apply the left brake independently from the right brake. (See What is differential braking? for more details and pictures.)
• There is a need to control the rudder, and you need to be able to move it either direction.
• The pilot needs to be able to make small and rapid adjustments to them both, in both directions.
• The pilot needs to be able to use both at the same time.
• The pilot needs to be able to use both while at the same time controlling pitch and bank.

Based on this, it's pretty easy to see that a push button, lever, or toggle switch somewhere wouldn't meet all of these requirements, especially if you need to use your hands (which are already occupied with the yoke) to do it.

There are three axis of motion on an aircraft that the pilot can control directly, and with current designs, the flight controls move the aircraft in the same direction that they are moved:

• Bank is controlled by turning the yoke left and right, which lowers the wing in the direction that you turn it.
• Pitch is controlled by pushing the yoke forward or pulling it back, making the nose raise or drop.
• Yaw is controlled by pushing the pedals in the direction that you want the nose to pivot.
• Since your feet are already on the rudder pedals and you need two brake pedals too (point one from above), they usually just put the brakes on the top of the rudder pedals so that they can be used at the same time.1

1 There are also hand brakes in some older aircraft that require you to use your hand. This has been pretty much abandoned in favor of toe (or heel) brakes since it did not allow for differential braking.

• +1 just a footnote to your footnote: you get all sorts of mechanisms (handbrake, coupling with airbrakes, pedal brakes) in sailplanes, which usually feature one main wheel anyway. Apr 26, 2014 at 18:20
• There are a couple of newer LSAs that use hand brakes too, like the Dynamic WT9. Apr 26, 2014 at 20:32
• Many aircraft (esp. older Russian military designs, such as MiG-21) used a hand brake on the central stick and could do differential braking, by moving the rudder pedals the usual way. The pedals released the braking pressure from the respective wheel. In fact, these aircraft usually relied solely on differential braking for turns.
– Zeus
Mar 1, 2018 at 0:19

It is by design.

An airplane have three axes to move, unlike a car, thus more controls should be provided to the pilot. As primates have two legs and two arms, the designers of airplanes put foot pedals to control the rudders.

Because Newton came up with the first law of motion before airplanes were built, we needed to have devise a way to stop airplanes, and hence brakes were invented. But unlike cars, where a foot or feet are used to apply the brakes, rudder pedals were already occupying that region. And hence airplane designers added brakes on top of the rudder pedals.

Like everything else, this also evolved overtime.

The rudder's direction in aircraft since the "Golden Age" of flight between the two World Wars into the 21st century has been manipulated with the movement of a pair of foot pedals by the pilot, while during the pre-1919 era rudder control was most often operated with by a center-pivoted, solid "rudder bar" which usually had pedal and/or stirrup-like hardware on its ends to allow the pilot's feet to stay close to the ends of the bar's rear surface.

I disagree with the statement that combining them leads to any confusion. The rudder pedal/brake assembly is very easy to understand and master. The mistakes you make as a student are minimal and do not happen after a little training anyway.

Another reason for having rudder pedals on the floor is that in a coordinated turn, you might have to add slight rudder along with banking the airplane. As hands are used to bank, rudder pedals are controlled by feet. This situation is only applicable during flight.

During flight, brakes do not have any effect as they are applied on the main landing gear.

During taxiing, when you press the rudder pedal (not applying brakes), on smaller airplanes, the nose wheel is turned.

• Just out of curiosity, have any notable aircraft been built that eliminate rudder pedals in favor of twisting a "joystick" (sidearm or central) or even the yoke? Or is that just too different from what pilots are used to? I believe that some spacecraft used twisted sidearm controllers for yaw control. Jun 24, 2014 at 15:23
• I can think of only linked aileron and rudder systems like in the Ercoupe. Interestingly, the Wright Flyer had it's yaw control linked to it's roll control (which was wing warping, not ailerons). Aug 14, 2015 at 17:04

One other factor... this results in a more natural usage of the control. Since a lot of aircraft steer on the ground by differential braking, the pilot will use the same control and same basic thought process for yaw on the ground that they use in the air. In the air, left rudder to yaw left. On the ground, press on the top of the left rudder pedal to turn left. This is one less detail that a pilot has to keep in their mind. They have plenty of details already, so any reduction in pilot mind load is a big bonus.

Early aircraft, especially early airliners like the Ford Trimotor and DC2, used a braking bar to accomplish the differential braking (called the 'Johnson bar'... it was about .75 meters in length, so some wishful thinking was probably involved) that required a fair amount of skill to master, as well as a fair amount of arm strength. Hydraulic brakes on the rudder pedals were a huge improvement.