Aircraft Systems

Fuel Selector Position Trap & Unbalanced Feeding

FAA Ref: FAA-S-ACS-6C Area I Task G (Operation of Systems)

Scenario & Physics Summary

Running a fuel tank dry during cruise flight, un-porting during slip maneuvers, and electric fuel pump boost procedure.

Interactive 3D Visual Plates & Scenario Media

Fuel Selector Position Trap & Unbalanced Feeding Plate 1

Plate 1: Fuel Selector Position Trap & Unbalanced Feeding

Fuel Selector Position Trap & Unbalanced Feeding Plate 2

Plate 2: Fuel Selector Position Trap & Unbalanced Feeding

Fuel Selector Position Trap & Unbalanced Feeding Plate 3

Plate 3: Fuel Selector Position Trap & Unbalanced Feeding

Fuel Selector Position Trap & Unbalanced Feeding Plate 4

Plate 4: Fuel Selector Position Trap & Unbalanced Feeding

Aerodynamic & Operational Physics

High-wing aircraft typically use gravity feed with a BOTH position; low-wing aircraft use engine-driven + electric boost pumps with LEFT/RIGHT selection.
Selecting a dry tank introduces air locks into fuel lines, causing sudden engine sputtering.
Immediate action: Turn electric fuel boost pump ON, switch fuel selector to fullest tank, verify mixture RICH, adjust throttle.

FAA Exam Gotcha Alert

Exam Trap: In a prolonged side-slip, fuel in low-wing aircraft un-ports away from the tank outlet, drawing air into the fuel line even with fuel remaining.

Frequently Asked Questions & Exam Explanations

What is fuel un-porting?

Fuel sloshing away from the tank pickup tube during prolonged slips or uncoordinated flight, allowing air into the fuel lines.

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