Don't discount the possibility that the derailment affected the TIU. If you have a Rev. L TIU, they do have a propensity to take damage to the DCS signal driver with voltage spikes. The result is a loss of signal strength. Oddly enough, the symptoms you suggest sound just like poor DCS signals. It's quite possible one or more other engines are just a bit more sensitive to the DCS signal and don't display the same symptoms.
|