Are air intakes usually forward facing?

• A. False
• B. Sometimes backward
• C. Sometimes downward
• D. Forward facing

Answer: (D)

Air intakes are designed to capture the air the engine will compress, and the usual orientation is forward-facing. Facing into the oncoming air takes advantage of the ram effect, increasing the pressure and mass flow into the engine at a given airspeed. It also helps draw in clean, undisturbed free-stream air rather than the slower air hugging the fuselage boundary layer, which would reduce engine efficiency and could cause flow distortions. A forward-facing inlet also makes it easier to protect the opening from debris and rain with proper lip design and filters.

There are occasional special cases for non-engine air systems or unique configurations, but for the primary engine intake, forward-facing is the standard and most reliable arrangement. That’s why forward facing is the best answer.