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Why do Airbus A320s always sound like there is a barking dog in the cargo bins? Three Interesting Facts about the Airbus A-320 Family

a320dog
Why do A320s always sound like there is a barking dog in the cargo bin? (Original Photo by Alan Wilson)

Let’s learn three new things about the A320 series today…

Airbus A320 series are the mainstay of many international short and medium haul fleets. Delta, United, American, JetBlue and Virgin America all fly them. Here are 3 interesting facts you may have never known before.

1.) Those last three digits after the dash (A320-XXX) actually mean something.

Nearly all Airbus jets also have a three number code after the type name. For example, N530VA pictured here is an A319-115. In deciding that three number suffix, the first number is the variant. Since there’s only one primary variant of the A319, it’s “1”, but aircraft like the A330 have a -200 and -300 variant, so the appropriate first digit is used. The second digit identifies the engine manufacturer- 0 is GE, 1 is CFM, 2 is Pratt & Whitney, 3 is IAE, 4 is Rolls Royce, 5 is skipped, and 6 is Engine Alliance. The third digit of the suffix is the engine subtype usually with increasing thrust the higher the number. For the A319, there are eight sub variants and -115 for this aircraft identifies which sub variant it is. Only the early model A300s fall outside Airbus’ nomenclature system.

A passenger's view of the more complex A321 model's flaps after landing.
A passenger’s view of the more complex A321 model’s flaps after landing.

2.) The Flaps on the A-321 are WAY different than the rest of the A-320 fleet.

Compared to the wing of the A319 and A320, the A321’s wing not only has both outboard and inboard double slotted flaps compared to the A320’s single slotted flaps, but the is also a tapering chord extension on the trailing edge of the outboard wing and a constant chord extension on the trailing edge of the inboard wing, adding up to a 4 square meter increase in wing area. It’s not the most ideal flap arrangement for the heavier and longer A321- if it had single slotted flaps like the rest of the A320 family, the degree of rotation needed at takeoff would have insured a tail strike. A slight chord increase and change to double slotted flaps were as far as what could be done and still retain significant production and parts commonality with the rest of the A320 family while eliminating the tail strike issue. 

3.) What is that “barking” noise you hear sometimes while sitting in an A320?

That noise is actually the sound of the Power Transfer Unit or PTU in operation.  The system allows one hydraulic unit to provide pressure to the other without the actual transfer of hydraulic fluid. It is automatically activated at times when the load on one system is high and/or multiple demands are being made on the system.It can also be activated when one hydraulic system fails or is shut down (think taxing after landing) to provide redundant pressure. You can read more about the system here: Ask the Pilot: The Barking Dog Sound

Written by Avgeekery

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