Mr Point
I know that the bomb bay firewire runs through the No 7 tank dry bay but this is not dedicated fire warning for the dry bay itself. A bomb bay fire warning, by definition, indicates a bomb bay fire. Had the crew member on the periscope not seen fire, and with no other indications, the crew would have believed the warning to be spurious (albeit unusual).
A dedicated dry bay smoke detection system would give a quicker warning to the crew, buying precious seconds. The potential down side is that, unlike the underfloor bays, the area could not be viewed for confirmation.
2 "points" for you:
1. Regardless of what the periscope might have revealed, the crew would still have done the drill, which includes switching off the air passing through that hot pipe. However, as the BOI report has stated, the fire became self-propagating very quickly, so the drill would not have achieved anything, except to possibly indicate a hopeless situation.
2. A smoke detector, as part of a fire protection system, would not have been fitted in the 7 Tank dry bay. Leaking Avtur would be the identified hazard, so a flame detector or firewire would be the mitigating control. Anyway, whatever would have been fitted, the crew would do the drill and operate the extinguishant, in all circumstances. A viewer would not be needed for confirmation before operating the extinguishant.
Regards
Ed Set