There is a hole on the belly fairing circled in yellow. I guess is an air intake but I tried searching some info and couldn't find anything. Atr 75


  • $\begingroup$ By the way, this kind of hole isn't restricted to the ATR-72; the 737 also have a similar design feature, and it is for the same purpose as well. $\endgroup$ Commented Oct 24, 2016 at 6:55

2 Answers 2


It is the ram air intake for the air conditioning system. There are two of them, one on each side.

Here is an image from the ATR-72 FCOM:

ATR 72

ATR-72 Air conditioning System, image from 737ng.co.uk

Details from the same document:

The air conditioning system is supplied by air processed through two packs which regulate air flow and temperature. The two packs are installed in the main landing gear fairings and operate automatically and independently.

The left pack supplies the cabin and cockpit air conditioned; the right pack supplies only the cabin air conditioned.

Also, as @Jonathan Walters points out, the intake is a good example of NACA inlet (or NACA scoop) and are found in a number of aircraft, for example Boeing 737.

  • 3
    $\begingroup$ You might consider adding that it is an example of a "NACA scoop" $\endgroup$
    – J W
    Commented Jan 29, 2016 at 0:14

A ram air inlet for reducing the heat of the Primary and Secondary Heat Exhangers caused by the bleed air coming from the PACK Valve (Primary XCGR) and from ACM Compressor part (Secondary XCGR). It is usually ventilated by 2 means:

  1. RAM AIR if the speed is > 150kts or
  2. Ground cooling turbofan (operated by bleed air coming from Pneumatic system) if the speed is < 150 kts.

This ram air is exhausted outboard via a ram air outlet near the Main Landing Gears

  • Note: The operation of the Ground cooling turbofan is electrically controlled by MFC and pneumatically operated by bleed air from pneumatic source (ENGINE).

Hope this helps..

B.E. Nolasco
ATR 72-500 Maintenance Instructor


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .