TO Engine Overheat (autothrottle caused)

[downscc 1,327]

2 minutes ago, berts said:

This means that If you program the wrong performance data into the FMS so that the calculated EPR is excessive for those ambient conditions then the EEC will set the actual EPR to equal the excessive calculated EPR figure.

That makes sense. Hurray, I learning something today.

[kevinh 409]

On 1/27/2019 at 10:53 PM, berts said:

I agree it will do based on the commanded EPR as set by the position of the thrust lever, but only when the thrust lever is at the fully forward position.  As I stated earlier "Each engine EEC signals its fuel metering unit to adjust the fuel flow so that the actual EPR equals the calculated EPR",   This means that If you program the wrong performance data into the FMS so that the calculated EPR is excessive for those ambient conditions then the EEC will set the actual EPR to equal the excessive calculated EPR figure.  Fortunately, when the EEC is operating In Normal Mode the engine will still have N1, N2 and N3 overspeed protection.  

Unless you somehow enter the wrong OAT into the FMS, you can’t overboost the engine by setting a low assumed temperature. All you would be doing is derate less. The engine should be within limits at full TO EPR.