Originally Posted by
B2N2
I’ve recently read Lufthansa Technik is working on a 380 Freighter combi, pax in upper deck and cargo on lower deck.
This would require either having lower deck as Class C cargo compartment with associated fire detection and suppression system or lobby for regulation change to allow Class E on combi aircraft.
I can't imagine what the weight penalty would be for a Class C fire suppression system for such a large volume as the lower deck of A380, and then to add it on top of A380's less than stellar useful load. This could be mitigated by "ETOPS-like" restriction of maximum time from an adequate airport. But funny enough, A380 can't really fit anywhere a B777 or a B747 can, so more troubles ahead.
Class E would be even a more difficult puzzle to solve, as fire suppression is essentially done by de-pressurising the aircraft once fire condition is detected, followed by a flight at ~FL250 until reaching diversion airport. So either they separate the aircraft into two pressure vessels, allowing separate pressure control between lower and upper deck, or to equip the passenger cabin with similar oxygen system that is available to flight crew on freighter aircraft, again with significant weight penalty.
No doubt, the technical solution for this problem exists. But I don't think it will come even close to being economically viable.