Lomapaseo, unless I'm mistaken Nik was alluding to the fact a blocked P3 pipe could dramatically effect the engine indications and basically that may be a factor, if indeed the engine had anything to do with this event.
On the CFM 56 the P3 pipe connects from the side of the combustion case at the 9 o'clock position, its a formed metal pipe, and gives HPC discharge pressure to the ECU, this enters BOTH channels on the ECU and then is converted to by the MEC/HMU to give movement to the valves in the fuel control unit and hence shaft speed. These P3 tubes are metal and have a drain hole at the lowest point, normally only water would collect and be drained away. ice perhaps but unlikely in normal conditions. The P3 is just one of 5 pressure sensors and does not work in isolation from other signals which are used by the ECU.
If for some unknown reason the P3 line was blocked the ECU may not be able to compute a model to adjust the fuel flow within the range from Surge to Flame out and indications would be erratic, but erratic engine indications are something we are trained for in the sim, and assuming one engine is running "normally" there is always comparison to be drawn to assist diagnosis. When unusual parameters are observed they should be entered in the comments section on the TLB to assist the engineers. One presumes the previously reported A/T malfunctions would have been investigated
Last edited by Kirks gusset; 3rd Feb 2021 at 16:41.