Abstract: An aircraft fire protection system which includes a plurality of water spray nozzles spaced along a plurality of longitudinal conduits all cross-connected by a plurality of transverse conduits, with "choking" type flow restrictors spaced between groups of spray nozzles to limit flow following conduit rupture. Conduits are connected to the aircraft on-board water supply system via a pump and non-return valve in series and, additionally or alternately, a plurality of externally mounted self-sealing couplings are interconnected to the conduits, one of which couplings should be accessible to fire-fighting personnel for fire tender hose hookup regardless of aircraft orientation and attitude. A two-way flow restrictor includes a housing with a captured ball valve element with flutes by-passing opposing seating shoulders for the ball to provide two predetermined "choked" flow rates for normal and reverse flow modes.