B737ng eec
Hi
Well i am aware of the fact that the mach number is the ratio of tas to local speed of sound which in turn is a function of the ambient temperature.
As far as the ecc using the mach number to compute the required thrust it is mentioned in the maintenance manual for the b737ng apart from other publications in my possession.
From maintenance manual airframe page 189 of 418
Normal mode
In normal mode the EEC claculates the mach number with: two Pt values from the ADIRU’s, P0 from the ADIRU or from the P0 ports on the EEC and the difference between the standard day temperature and the current ambient temperature. If Pt pressure is not valid or if the EEC switch is de-selected the EEC goes to one of the alternate modes.
T12 supplies current ambient temperature when the aircraft is on the ground and for the first 5 minutes after takeoff and then it uses T12 and TAT inputs from the ADIRU to compute current ambient temlerature - i stand corrected with regard to my previous T probe statement.
I do understand the implications that ambient pressure has in the functioning of the engine with regard to thrust limit and proper stoichiometric ratios and airflow patterns inside the engine, but the usage of the mach number escapes me, still.
Many thanks