jet engines in rain conditions
Until the 777 development there were no FAA standards concerning water injestion tolerance .. some engines like the CF-6 are naturally tolerant to water - other engines were very intolerant to water such as the CFM-56. However, the good old boys at Boeing solved this when it appeared on the 737 dual engine flame out - with their "cutback-splitter" fix documented in US patent 5431535 - " Foreign matter diverter systems for turbofan engines ". Since that time - the Airbus A320 & A340 have benefited from this technology as well - since they all use the same engine - more or less .. Today, this is wellunderstood and is further documented in the FAA's engineering design - certification compliance methods for turbomachinery ..
You see there were ingestion standards for water ingestion (rain) but they did not fully recognize neither the statistical magnitude of encounters, nor the mechanisms by which water screws up and engine.
Thus the update to the rule addressed both aspects to provide a projected freedom from multiple engine flameout to better than E-8. Inspite of this update we still have the event like the B737NG in Indonesia and altitude events with ice crystals.
One might notice the variation in test rigs over the years with some manufacturers flooding the inlet of their big fans with water spray across the complete inlet with the majority of the water going out the fan ducts while later test methods tend to concentrate on the core of the engine which has to process the small droplets ice/crystals into gases before they reach the burner (compressor work load),.
