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that exits the nacelle tank on its inboard side and immediately connects to a “T” fitting that has one pipe going forward and one pipe going aft. The forward pipe goes to the fuel firewall shut-off valve, just inches away, and the aft pipe is the start of the crossfeed line. This electric boost pump is the only pump that prevents cavitation of the engine-driven, high-pressure pump on the A90, B90 and C90. There is a secondary electric boost pump in parallel with it on the 65-90 and 100, the Straight 90 and Straight 100. The other models – E90, F90, A100, B100, 200s and 300s – have an engine-driven boost pump so the submerged, electric one in the nacelle is now called the “standby pump.”
Between the submerged pump and the exit pipe from the nacelle is a key element – a check valve. This valve permits fuel to exit the nacelle but does not allow fuel to enter the nacelle at this point.
Therefore, concerning the nacelle tank, we have reviewed (1) That its output line can send fuel in two directions: To its own engine and to the crossfeed line. (2) That fuel can come from the nacelle tank here but cannot enter into the nacelle tank due to a check valve.
Both sides, left and right, are as we have presented. This means that there is only one crossfeed line, or pipe that connects the left and right nacelle outlets to each other. This line contains the single crossfeed valve, a Normally-Closed (NC), solenoid-operated valve that uses electric power to open. In all King Air models this valve is located close to the left nacelle tank, not smack- dab half-way under the cabin aisle floorboards.
Assume that the crossfeed valve is open. That would yield a single fuel line connecting the two nacelle
APRIL 2024
King Air 350 fuel panel.
King Air F90 fuel panel.
KING AIR MAGAZINE • 21