Title says it all... just trying to find out if there is a second NACA duct for the fuel inerting system on the A220, or if it's the same duct that is used for the air conditioning inlet.


2 Answers 2


The fuel inerting system on the A220 uses bleed air from the engines:


The Fuel Tank Inerting System (FTIS) generates nitrogen-enriched air and distributes it into the air space in the fuel tanks to provide non-flammable air in the tanks.

The bleed air, cooled by a ram air heat exchanger, passes through an air separation module that removes oxygen to create the nitrogen-enriched air. The oxygen is expelled overboard and the nitrogen-enriched air is directed into the fuel tanks.


(Bombardier CS300 FCOM 11-07 - Fuel Inerting System)

The air conditioning also uses that same bleed air. The NACA duct you mean is for the ram air used for cooling the bleed air, which is then dumped overboard again.

There are however NACA scoops for each surge tank on the A220:

In flight, NACA scoops located in each surge tank provide ram air pressure to maintain a positive pressure on the fuel in the tanks. During ground operations, NACA scoops provide static ventilation of the tanks and relieve the buildup of air pressure during refueling or thermal expansion of the fuel.

A220 Fuel Tank Ventilation

(Bombardier CS300 FCOM 11-02 - Fuel Storage System)

  • $\begingroup$ I find it amusing that you've illustrated an A220 answer with Bombardier CS300 images. I understand that the systems will, likely, be essentially identical, I just find it amusing. ;) $\endgroup$
    – FreeMan
    Apr 21, 2022 at 15:52
  • 2
    $\begingroup$ @FreeMan Well, the FCOM I have is an older one, which still says CS300, but it's the same aircraft. $\endgroup$
    – Bianfable
    Apr 21, 2022 at 15:53
  • $\begingroup$ Ah. I didn't realize that. It might be worth a note in the answer then. $\endgroup$
    – FreeMan
    Apr 21, 2022 at 15:56
  • $\begingroup$ Ah that makes sense. I had initially been confused by the "ram air" label in the first photo you posted, and was wondering where the outside air was coming from if there was no separate intake for it. The same bleed air is cooled by ram air for both the air conditioning and the fuel inerting system. Thanks! $\endgroup$
    – vazznation
    Apr 21, 2022 at 18:52

Ref OP, there is a separate ram inlet for the Inerting system. The cooling ram inlet is positioned on the LHS near centerline of the belly fairing right next to the service access panel.


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