Force on pilot ejecting at supersonic speeds? Using the Rayleigh drag equation, and approximations for the air density, drag and frontal area of the pilot, and mass, at around 300 m/s (subsonic) a pilot might experience deceleration forces of about 40G. BTW, I assumed a drag coefficient of 1 since a Human being strapped to a chair is not especially aerodynamically slippery.
Now, if that was raised by another 100 m/s making it supersonic, how much would the force increase disproportionately?
Note that one person has ejected at low altitude supersonic and lived - just. So, how much of a difference does being on the wrong side of that dividing line make?
 A: There are lots of papers reporting measurements of the drag coefficient of a sphere below and above supersonic speeds. Glancing through them, it appears the drag coefficient does increase as the speed goes supersonic, but by relatively modest amounts.
Obviously a pilot isn't a sphere, and the airflow will be affected by the presence of the plane, so I think we can at best guesstimate the drag. My guesstimate would be no dramatic increase in force with speed as the airflow goes supersonic.
A: The acceleration needs to be provided here to conclude the net force on the pilot. 
Zero g: it shows free fall. Let me elaborate simply :
Weight= Mass × g force
Now in your case if the pilot goes to 400m/s in 10 seconds from a standstill, he will experience( i deem he'll feel it more than he experiences it :)) his weight FOUR the times as against whilst he ain't driving. 
Moreover, g force, the name seemed misleading to me, it shows the acceleration, instead of the force. g-force=force AGAINST gravity. A book resting on table, g-force=1g, UPWARDS. 
The example i presented, g-force=5g(assuming the pilot goes straight upwards). 
