Flap Track Fairings: What Are They?

If you ask most people who have flown, they would probably say they have seen these “pod-like” structures under the wings of an aircraft. Some people assume that they hold fuel. This is not correct, but in fact, they house the workings of the inboard and outboard flaps. Within these structures, the jackscrew, carriages, gearboxes, and associated mounting bracketry are very un-aerodynamic. Therefore, the canoe-like fairings cover them.

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These structures house the essential components of the hydraulic actuators for the flaps on this Boeing 757
credit: gov.uk

Boeing and Airbus aircraft use similar flap fairings, while McDonnell Douglas aircraft in particular have unique vertical fairings that house the hydraulic actuators.

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Inside the vertical flap fairing on a DC-10 credit: abbottaerospace.com
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Inside the “canoe” – shaped flap fairing on the Boeing 737
credit: abbottaerospace.com
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Some flap track fairings have flashy tips, which are for preventing accidents during ground handling operations, e.g. by belt loaders. They can be a painted or applied with adhesive tape (possibly reflective, useful at night).

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Some aircraft (most notably the A320) have painted flap track fairings to increase visibility and avoid accidents on the ground.
credit: aviation.stackexchange.com
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Not all aircraft have these structures under their wings, as the design of the flap mechanism varies according to the manufacturer. But on most Boeing, Airbus, and McDonnell Douglas aircraft that do have these structures, the principle is the same—to provide an aerodynamic cover which in turn reduces drag.

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Sources:

Cover Photo: https://aviation.stackexchange.com/questions/18749/what-are-these-long-tubes-under-the-wings

https://www.abbottaerospace.com/aa-sb-001/22-aircraft-specific-design-features-and-design-methods/22-16-57-wings/22-16-4-leading-and-trailing-edge-devices/

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https://www.airliners.net/forum/viewtopic.php?t=739199

https://aviation.stackexchange.com/questions/26627/why-are-the-tips-of-the-flap-track-fairings-painted-red

https://assets.publishing.service.gov.uk/media/5422faa6e5274a131400078b/Pub_Version_G-CPER

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