Originally Posted by
Techo27
Sorry guys, the fuel control system of any gas turbine engine requires 5 basic inputs for self control either by FADEC or the Fuel control unit itself. These are a reference of PT2 and TT2 for air density, N2 Rpm, Throttle position and PB (Combustion chamber pressure) to prevent engine stall during acceleration. Supersonic aircraft need one additional control factor and that is MA (Mach number) to prevent excessive air entering the engine intake when aircraft airspeed is above Mach.
All other parameters such as N1 Rpm, TIT, FF, PT7 or Oil Pressure are simply for indication to the pilot of the state of his engine EG N1 RPM or PT7-PT2 when converted to an EPR is used to inform the flight crew how much power the engine is producing with FF used as a cross reference. OIl pressure and TIT is simply to inform the aircrew on the state of the engine in regards to oil pressure and operating temperature. Some FADEC systems are designed with software to control any condition outside normal, by warning the aircrew and automatically retarding fuel flow to prevent engine over speeds and over temps and also relight the engine if it flames out during aggressive maneuvering or abnormal atmospheric conditions if throttle position is in flight idle or above.
The FADEC also had a slight problem in this case. P2 / P3 / P6 / N2 /T6 were all going out of normal parameters with an enging that would have been seeing its compresser and turbine stages rapidly chewing themselves up on parts of itself and a rogue intake blank. While myself and a colleague were waiting to ground run a small regional airliner today, we discused the accident in question and realised that an F35B was 7000 Kgs more than our airliners MTOM. Our highly effective brakes on 4 wheels wouldn't stop our aircraft from the distance from engine failure to end of deck at the same speed. The F35B brakes certainly could not.