engine P1
Quote:
Originally Posted by ettore
Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?
Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.
HN39
Yes the engine probes in the A330 fitted with Roller engines did suffer this problem. RR engines have a P1 probe to measure pressure ratio as the thrust is measured as EPR.
Quite a few years back I had a pax visit to the fight deck of my A330 and who was an engineer from RR Derby. I (actually the a/c) was able to demonstrate this problem as we negotiated TS's over the Philippines and each engine was affected in turn by icing as the supercooled water at cruise altitude exceeded the heating capability of the probes. The effect of the icing of the P1 probes was to reduce maximum allowable EPR (blue triangle in the EPR gauge) in each engine as it was affected by icing. The RR man was excited to access the data from the MCDU (under supervision of course).
I subsequently learned that RR first knew of this problem from experience on the B747-400 but they were reasonably unconcerned as the consequential P1 error from icing was temporary in time and reduced the max allowable EPR and therefore was considered to be safe.