I read that the intake mass flow ratio (not sure its translated to correct lingo) can be expressed as:

$C_A = \frac{\textrm{airflow through air intake}}{\textrm{air density } \times \textrm{ speed of free flow }\times \textrm{ intake area}}$

A graph of this could look like:

Air intake factor

Now my question is two fold:

  1. What is the correct english term for this factor?
  2. How do I estimate how much air flows through the intake due to engine suction.
  • $\begingroup$ Maybe the term is more like inflow-number. Don't know. If for example flying at low speed and more air is sucked in that would normally hit the intake if it was only a tube, then the airintake factor is greater than 1. That how I understood it. $\endgroup$
    – Invariant
    Commented Apr 10, 2017 at 2:44

1 Answer 1


Okay, to solve this I assumed the atmospahere is ISA and flying at 0ft. Also that air suction vary linear proportional to mil thrust.

So that airflowThroughAirIntake = factor*thrust

I then did some flight tests to estimate what that factor would be, getting the ratio from the graph at full mil thrust.


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