Lonewolf,
Something about using P2 to substitute for pitot air strikes me as very wrong, but I can't put my finger on it.
Station 1 is the free stream, PT2 is total pressure at the engine inlet. Total pressure is total pressure, whether you measure it at the engine inlet face or with a pitot tube, so long as it is properly derived and calibrated it’s the same.
A33Zab
Wouldn't do it for GE. Sensor in inlet is Temp sensor T12, PS1.2 is static pressure ports just IFO fan. The only probe measuring dynamic pressure is P2.5 just after the booster, but this is only used for conditioning monitoring and that's an option.
That’s actually enough. If you have inlet temp, static pressure at the inlet, fan rpm and total pressure after the booster you have to use a fan map model and look up the pressure, but it can be calculated, and probably already is being calculated by the FADEC already and compared with the ideal map for condition monitoring. What you would do is, using the inlet temperature and rpm, you know how much pressure is being made by the fan and that allows you back calculate the free stream total pressure. Can be done pretty accurately (within a couple of knots) if you know the altitude.