What Is The Airbus Barking Dog Sound?
Have you ever sat on an aeroplane, most likely an Airbus A320/A330 and wondered what on earth is causing the sawing or ‘barking dog sound noise from underneath the aircraft?
This is caused by a Power Transfer Unit, also known as the PTU.
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Watch the video below for more information and an explanation!
I’m a Commercial Airline Pilot, and I hope this video will further explain how this works.
Why Does The PTU Cause This Noise?
This PTU is used to power the hydraulic systems on some Airbus aircraft when it notices a drop in pressure of over 500 psi on either the green or yellow hydraulic system.
The three systems are usually pressurised at 3000psi.
Should the main hydraulic pump (the engines for both the green and yellow systems) be unavailable, as they are when we turn off an engine whilst taxiing (for fuel-saving purposes), there is often a drop in hydraulic pressure, which results in this PTU firing up, creating the ‘barking dog’ or ‘sawing’ noise that is so commonly reported.
Is There Something Wrong With The Aircraft? Airbus Barking Noise
Though very normal to assume this when such a strange noise is made on an aircraft, there is absolutely nothing wrong with the systems.
It’s normal for the hydraulic systems to lose a bit of pressure when carrying out their duties such as raising the landing gear, deploying the flaps or just keeping all of the flight controls moving.
This Airbus barking dog sound is part of normal operation.
The sound is very much like marmite. Some people seem to love the noise that’s made and actually find it one of the best parts about the A320 fleet.
Whereas others cant stand this noise, and find it very unpleasant on the ears!
Why Three Hydraulic Systems On The Airbus?
Most aircraft will have three hydraulic systems. However, the Boeing Jumbo 747 actually had four!
However, some newer aircraft, such as the Airbus A380 and Airbus A350 only have two systems. This saves a considerable amount of weight.
Aircraft have multiple hydraulic systems for redundancy purposes. For example, if one system fails (which is very unlikely) then there are other systems to pick up its slack.
The newer aircraft with just two systems will also have an electrical system to back everything up. This electrical system will provide redundancy to the important systems such as the flight controls etc.