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There is a curious box between the engines of an A-10. It's seems rather rudimentary, like an afterthought, although it was present on the prototype.

I've found a few cutaways but this part is hidden. I'm fairly sure that at least the front is hollow, so perhaps related to an APU. The question is, what is it for, and why, even in the context of the somewhat inelegant A-10, why so unrefined?

A-10 - source: savasucakalari source: savasucakalari

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  • $\begingroup$ I feel like there is an identical question around here for some reason but I can't seem to find it! $\endgroup$ – dalearn Dec 6 '17 at 14:24
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It is the intake/exhaust duct of the cooling system.

Basically, the front side consists of the ram air duct, which feeds air into the ECU precooler, with the (heated) exhaust air vented out through the rear. The image below shows a closeup of the duct.

A-10 cooling duct

Image description: Kenneth Thompson, 576th Aerospace Maintenance and Regeneration Squadron aircraft mechanic, aligns a portion of the pre-cooler ram air duct onto the top of an A-10A Thunderbolt on Davis-Monthan Air Force Base, Ariz., Jan. 23, 2013. Source: warthognews.blogspot.in

Here's another image that shows a cross-section of the system. The cooling system (without the box) could be seen above the APU.

A10 Warthog cooling system

Image from pintrest.

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    $\begingroup$ I wonder if you can shine any light onto the the boxy design of the duct? Airliners etc. tend to have intakes built smoothly into the side of the airframe. I'm assuming this one is on top to reduce the chance of dust and foreign objects from getting in? $\endgroup$ – Cooper Oct 31 '16 at 13:50
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    $\begingroup$ @Cooper I think it's simply the consequence of the location of ECU. The front of the aircraft is dominated by the massive GAU-8. This along with the location of engines, have meant that the ECU, APU etc. are in the rear part of fuselage. And you'd be right that the location is to reduce chances of fod ingestion; also A10 being purely designed for CAS, it wasn't fine tuned for drag reduction, though my guess is that the contribution of the 'box' to drag would be negligible. $\endgroup$ – aeroalias Oct 31 '16 at 14:01
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    $\begingroup$ Nah, it's just there so that guy has something to hang on to if the pilot takes off while he's still there. *nodnod* $\endgroup$ – David Richerby Oct 31 '16 at 19:44
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It's an intake (front) and exhaust (back) for the cooling system.

Sources: Photographs, diagram.

However I can't for the life of me find any reference to its unusual boxy design. Perhaps it simply doesn't need streamlining because the A-10 is designed for relatively low-speed flight.

The position of the box is probably high up (much like the engines) to reduce the chances of dust and foreign objects from clogging the intake, as the aircraft is designed to fly at very low altitudes.

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