Cable Systems vs. Hydraulic Systems vs. Fly by Wire in Aircraft - AeroGuard

Cable Systems vs. Hydraulic Systems vs. Fly by Wire in Aircraft

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If you’re familiar with aviation lingo, it’s likely you have an idea about the varying control systems on an aircraft. However, do you know the differences between these systems, as well as the benefits and disadvantages of each? Let’s dive in.

A Look at Mechanically Actuated Cable Systems

Mechanically actuated cable systems are one type of primary flight control system. Cables are utilized in engine controls and landing gear as well.

Benefits of Cable Systems

Cable systems have several advantages:

  • Efficient
  • Allows for accurate control
  • Lightweight and strong


Disadvantages of Cable Systems

There is one disadvantage that comes with cable systems:

  • The tension must be adjusted often because of changes in temperature and stretching


Another type of control system includes mechanically actuated hydraulic systems.


Mechanically Actuated Hydraulic Systems Explained

Similar to steering and braking in a car, hydraulic aircraft systems utilize pressurized fluid and mechanical components to move parts of the plane. The components include the hydraulic pump, motor and system plumbing.

A pilot will activate a hydraulic system using a switch or flight control instrument. Once the pump is activated, the system becomes pressurized and the actuator moves to the control surface and is then moved into the proper position.

Hydraulics and Pascal’s Law

Pascal’s law essentially states that if pressure is applied on non-compressible liquid in a closed system, this creates equal pressure throughout that system. Having basic knowledge of Pascal’s law is helpful in understanding aircraft hydraulics.

When a pilot activates a hydraulic system on the aircraft, this causes the actuator’s movement and puts whichever part of the control system utilized into motion.

There are a multitude of benefits hydraulics provide.

Benefits of Aircraft Hydraulic Systems

There are several benefits to hydraulic systems:

  • Responds quickly to control inputs
  • Dependable
  • No delay in movement because liquids aren’t compressible
  • Hydraulics make flight controls easier to maneuver


Disadvantages of Hydraulics

There are a few disadvantages to hydraulic aircraft systems:

  • Hydraulic fluid is considered corrosive
  • Heavier weight for requisite components


Lastly, there are fly by wire aircraft.

Fly by Wire: What it Means

“Fly by wire” is a phrase used to describe a system on an airplane that uses computers rather than mechanics to process flight controls.

The computer works by sending signals to an actuator, which then determines how control surfaces are moved to satisfy what the pilot tells it to do via a sidestick or yoke. The computer communicates using an electric wire, ergo the name, “fly by wire”. Once a signal is received, the flight control computer assesses which movement to make to perform the pilot’s command. The commands move the actuators which send a signal back to the flight computer. This process repeats as the pilot inputs various commands.

Fly by wire aircraft have a variety of benefits associated with them.

Benefits of Fly by Wire Aircraft

Fly by wire aircraft offer:

  • Flight envelope protection system allowing pilots full control without exceeding the aircraft’s limits
  • Weight and drag reduction
  • Increased safety and efficiency
  • Maintenance reduction
  • Reduced workload for pilots


Disadvantages of Fly by Wire

There are some disadvantages that accompany fly by wire aircraft:

  • Can be costly in comparison to a mechanical system
  • More complex technology
  • Pilots must monitor automatic systems



Each of the above systems are used in all different types of aircraft. Training aircraft such as the Piper Archer and Piper Seminole utilized at AeroGuard offer cable systems, while SkyWest CRJs utilize hydraulics and the Airbus A320 uses fly by wire systems. As the airline industry continues to grow and improve, so will its future technology, and that’s something to look forward to!

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