FlyingStone
That is my recollection of the FCU on the -3 engine as well. There is mechanical feedback to the throttle to ensure the lever is and remains at idle as the FCU schedules into reverse. That would suggest that a TR problem will give a rapid and complete closure of the thrust lever to idle. If it is working anywhere near correctly.. If the cable itself has a failure (other types I fly have repetitive inspections of the TR follow-up cables due to failures), a failure in the cable itself could be an issue. Cannot recall if the TR cable acts under tension to close or not, which could discount that as a failure mode. The other issue that can cause both thrust levers to reduce is a TAT probe failure, which signals for limit cases to the AT system calculation, or of the PT2 on an engine going bad, as that has a limiter input to the FCU, but that should not move the thrust lever. The main memory of the FCU was it was quite expensive to buy the replacement.
The FCU was properly known as a MEC and had the PMC as a trimming system which was a form of limited EEC/DEEC. The MEC took the PS12 and T2 for the governing system input along with PLA. The only other items that it did was to give flight idle, variable bleed valves, VBV and the variable stator valves, VSVs. The latter was IIRC fluidic control system but with mechanical feedback to the MEC. Expensive when they went bad. The PMC trimmed fuel electrically and didn't drive the PLA. Hazy.
TD Racer On the CVR, I'm not sure it will reveal anything of great note in this case. That the crew didn't correct the TL split is indicated in the FDR data reportedly. There are not too many logical reasons why a crew member on seeing a split would not remove the split, yet that appears not to have happened. The highest likelihood is the crew were not aware of the split through distraction with other tasks, and that can be assessed in a simulator with a cohort of drivers as to the likelihood of detection. To get in before the objections, there is a history of extended time to detect a condition or a complete failure to detect in our sorry past. Take a B747 that has a gear red light for 2 minutes and lands with no nosewheel... and that was a "top-of-the-line" IP. Expectations of immediate and correct crew responses is akin to "they said artificial sweeteners were safe, and WMD's were in Iraq, and Anna Nicole married for love!". If it's recovered, great, but the event shows that the crew likely never recognized the condition, otherwise they would have got to Ponkianak for their Kopi Luwak.
Last edited by fdr; 12th Feb 2021 at 01:11.