Strobe lights - AC cross-tie
I went back into the 1200's series of posts and found that there is indeed no agreement about which exterior lights were on as observed by the ground-technican when the A/C was still on the ground prior to t/o: either the anti-collision lights or the strobes on the wingtips. The first are just put on or off from the cockpit, but the strobes will only start working on N/G lift-off (provided that the cockpit switch is on BOTH (pos+strobes).
If the R 2-5 relay installed were to be of a certain type, it has already been subject to Boeing Alert SBs and FAA AD's in the early 2000's because of unreliability issues with potentially serious consequences (E/B fire or in case of engine failire not connecting certain circuits linked to the generator of the failed enginewith the generator of the still working engine, i.e. the essential function of the AC cross-tie). The latter makes me still wonder about the earlier reported witness statements indicating engine failure and what is stated in the draft report, namely:
1.the apparent excessive length of the runway covered by HFP before rotation,
2.the apparent fact that both engines were producing thrust during take-off run and for the remainder of the flight and
3.the statement that the first visual inspection of the engines didn’t show pre-crash anomalies.
One of the issues of a non-functioning AC cross-tie relay in case of engine failure seems to be that the electrical circuits fed from the generator of that engine may cease to work, freezing e.g. the EPR reading of that engine in the cockpit and not giving any master caution warnings in the cockpit either, making it very difficult for the pilots to notice any malfunction with the affected engine (as it apparently did in a DC-9-32 accident in 1994 in Canada, as reported on in TSB A94C0034).