DSPLY Source b737NG
 

Hi

Why can you get a DSPLY Source annunciation and both EEC lights illuminated, indicating reversion into alternate soft mode?

Why does one possibly bring up the other?

I thought the EECs simply control engine thrust within safe parameters as they are effectively FADECs?

Hi Pin...

Here goes my 2 cents:

EECs needs to monitor a variety of parameters to do his magic, right ?

Unfortunately, some of the information used by the EECs is delivered by the DEUs. :bored:

A DSPLY SOURCE indicates a DEU problem... This way, EECs will lack some of the information needed and will initially revert to SOFT ALTERNATE (using the last valid parameters as reference).

Hope that helps ! :ok:

Almost correct.
If one DEU fails, both engines will depend on one source. So in case the remaining DEU provides corrupted data, both engines would be affected. Being in soft alternate and later in hard alternate the engines will not rely on a single source but operate on independent data

As said by B737 SFP ,the deu convert analogic data to numeric data in order to be used by EEC wich undestand only numeric data