I'm trying to get the aircraft up and running from cold and dark "by the book". If I follow the normal procedures in the FCOM (at NP.21.10), however, the F/O preflight procedure calls for the yaw damper switch on followed by verification that the yaw damper light is off. No doubt the mistake I'm making concerns the state of the aircraft at this point, but if I'm starting from cold and dark, when I'm doing this step as prescribed, both engine-driven and electric hydraulic pumps are off. Consequently, the yaw damper light does not extinguish and the switch trips back to off. What troubles me is that I thought that the electric pumps did not go on until after pushback to avoid the risk of injury to ground crew, and the yaw damper is of course not required until much later on. Similarly, when undertaking the overheat and fire panel checks (at NP.21.13), if I hold the test switch to OVHT/FIRE, all the required lights illuminate, and the fire bell sounds, however if I then push the master fire warn light, none of the required lights remain illuminated (ie Nos 1 & 2, APU fire switches, engs 1 & 2 overheat, and wheel well). As I say, there is probably some really fundamentally incorrect assumption that I'm making here, but I'd be grateful if someone might be able to set me straight. thx

Jeff, The yaw damper requires inputs from the inertial reference system, so if you move the yaw damper to the ON position before the IRSs are aligned, the YAW DAMPER light will remain illuminated until alignment has completed. Ray

Thanks, Ray. Will give that a go.

Similarly, when undertaking the overheat and fire panel checks (at NP.21.13), if I hold the test switch to OVHT/FIRE, all the required lights illuminate, and the fire bell sounds, however if I then push the master fire warn light, none of the required lights remain illuminated (ie Nos 1 & 2, APU fire switches, engs 1 & 2 overheat, and wheel well). As I say, there is probably some really fundamentally incorrect assumption that I'm making here, but I'd be grateful if someone might be able to set me straight. thx

Are you speaking of the Fire Warning light on the glareshield? That's not a press-to-test. That's merely for cancelling.