It seems unlikely that incapacitation by smoke alone can happen so quickly that the crew could not send out a message if the cockpit communication equipment had not been disabled by fire first.
However this would not be the first time a major avionics fire near the cockpit led to the loss of a passenger aircraft. A Swissair MD-11 jumbo jet was lost due to this cause. The intensity of the fire and smoke in the cockpit forced the crew out of the cockpit in that instance. Evidence of this was found in the form of molten droplets from overhead equipment panel burned their way into the cushion of the pilot and copilot' seats, indicating they were not in their seats in the later stages of the fire.
However this would not be the first time a major avionics fire near the cockpit led to the loss of a passenger aircraft. A Swissair MD-11 jumbo jet was lost due to this cause. The intensity of the fire and smoke in the cockpit forced the crew out of the cockpit in that instance. Evidence of this was found in the form of molten droplets from overhead equipment panel burned their way into the cushion of the pilot and copilot' seats, indicating they were not in their seats in the later stages of the fire.
