Fault Tree — Triple Hydraulic Loss
Total hydraulic power loss on a three-system narrowbody over a five-hour leg, where a single common-cause fluid contamination event sits in all three branches and dominates a picture that looks fully redundant.
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title "Loss of all hydraulic power — narrowbody transport"
mission 5h # one flight leg
top "All three hydraulic systems lost" = AND(green_lost, blue_lost, yellow_lost)
gate green_lost "Green system lost" = OR(green_edp, green_leak, eng1_shutdown, fluid_contam)
gate blue_lost "Blue system lost" = OR(blue_pump, blue_leak, ac_bus_loss, fluid_contam)
gate yellow_lost "Yellow system lost" = OR(yellow_edp, yellow_leak, eng2_shutdown, fluid_contam)
event green_edp "Green engine-driven pump fails" rate=2.4e-5
event yellow_edp "Yellow engine-driven pump fails" rate=2.4e-5
event blue_pump "Blue electric pump fails" rate=3.1e-5
event green_leak "Green line rupture" rate=8.0e-7
event blue_leak "Blue line rupture" rate=8.0e-7
event yellow_leak "Yellow line rupture" rate=8.0e-7
event eng1_shutdown "Engine 1 in-flight shutdown" rate=1.1e-5
event eng2_shutdown "Engine 2 in-flight shutdown" rate=1.1e-5
event ac_bus_loss "AC essential bus lost" rate=6.0e-6
// The one event that is NOT independent between systems.
event fluid_contam "Hydraulic fluid contamination (common cause)" p=2.5e-5