Yokes: What Are They and What Do They Do?
The yoke is among the most important parts of an aircraft. Also known as the control wheel or control column, the yoke is a device used for piloting certain fixed-wing aircraft. The pilot uses the yoke to control the attitude of the plane, typically in both pitch and roll. Rotation of the yoke controls the ailerons as well as the roll axis. Fore and aft movement of the yoke controls the elevator and pitch axis. When the pilot pulls back on the yoke, the nose of the aircraft rises. When the yoke is pushed forward, the nose is lowered. Similarly, when the yoke is turned left the plane rolls to the left, and when it is turned to the right, the plane rolls right.
In small and medium-sized aircraft, usually propeller driven, there is a mechanical system wherein the yoke is connected directly to the control surfaces through a series of cables and rods. Human power alone is not enough to control more powerful aircraft, so hydraulic systems are used. In these systems, yoke movements control hydraulic valves and actuators. In modern aircraft, yokes may feature a stick shaker, which is designed to warn the pilot of a potential stall, or a stick pusher, which assists in stall recovery.
Yokes are made in a variety of sizes and styles, the most common being a “U” or “W” shape. Some aircraft, such as the Aerospatiale/BAC Concorde and aircraft made by Embraer, use an “M” shape. Though uncommon, some aircraft use circular designs similar to a steering wheel. In larger aircraft, the yoke is usually mounted on a post protruding from the floor, known as the control column. In most other aircraft, the yoke is mounted on a horizontal tube that protrudes from the instrument panel.
Advantages and Disadvantages of Yoke
Just like any other aerospace component, yokes have both advantages and disadvantages. For example, side-sticks and center-sticks are better than yokes when making rapid control inputs and dealing with high g-forces. This is why they are used in military, sport, and aerobatic aircraft. However, yokes are more precise due to their larger range of motion. Additionally, yokes provide the pilot with more visual feedback. Another advantage of yokes is that they are connected and move together, therefore providing instant notification to both pilots when one makes a control input. This differs from some fly-by-wire control sticks that allow pilots to send different, sometimes conflicting, inputs.
Another disadvantage of yokes is that they take up more room than side-sticks in the cockpit, and may even block certain instruments. By comparison, side-sticks limit intrusion, and make it easier to enter and exit the cockpit. Despite their larger size, yokes can be comfortably used with either hand. This makes them useful if the pilot needs a free hand to write or use other controls in the cockpit.
Though they are extremely popular, yokes are not found on all aircraft. Helicopters, for example, use a cyclic, and military fighter aircraft use a center or side-stick. Certain light aircraft use a stick if the pilots prefer that control system. The latest family of Airbus passenger jets use a side-stick to actuate control surfaces. In many flight simulators, there are computer input devices designed to simulate a yoke.
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