Fuel Metering Systems
Fuel Metering Systems is a core knowledge area on the AMT — Powerplant FAA written exam. This hub collects our 16 in-depth, ACS-aligned fuel metering systems articles — each written in plain English and grounded in the official FAA handbooks. Work through them below, then drill the topic with practice questions.
Pressure-Injection Carburetor Design and Operation
Pressure-injection carburetors meter fuel by balancing multiple air pressures against a diaphragm-and-valve system, enabling reliable mixture control at all attitudes and altitudes without the float-system limitations common in simpler designs.
Carburetor Icing Types and Prevention Methods
Carburetor icing can occur well above freezing in humid conditions, threatening engine power and safety; understanding its three types and prevention methods is essential for every powerplant technician.
Float-Type Carburetor Operating Principles
Float-type carburetors use a venturi, float chamber, and metering jet to mix fuel and air in the correct ratio for combustion; understanding their operating principles is essential for AMT powerplant certification.
Carburetor Heat System Operation and Carb Heat Valve
The carburetor heat system prevents and eliminates ice formation in the carburetor venturi and throttle by routing warm air around the intake, and every AMT must understand how the carb heat valve controls this alternate air path.
Accelerator Pump and Power Enrichment Circuits
The accelerator pump and power enrichment circuits prevent lean stumbles during rapid throttle advances and ensure rich mixture delivery at high power settings — two critical carburetor systems every powerplant technician must understand.
Continuous-Flow Fuel Injection System Operation
Continuous-flow fuel injection delivers a steady, metered stream of fuel to each cylinder's intake port, eliminating carburetor icing and improving mixture distribution — a critical system for AMT Powerplant certification.
Mixture Control Systems in Carburetors
Mixture control systems in aircraft carburetors regulate the fuel-to-air ratio across varying altitudes and operating conditions, preventing rich-mixture inefficiency and lean-mixture engine damage.
Fuel Injection System vs Carburetor System Comparison
Fuel injection systems deliver fuel directly to each cylinder intake port while carburetors meter fuel through a venturi, each offering distinct advantages, limitations, and maintenance considerations for powerplant technicians.
Bendix RSA Fuel Injection Servo Operation
The Bendix RSA continuous-flow fuel injection servo precisely meters fuel by balancing impact air pressure against throttle-controlled venturi suction, delivering consistent mixture ratios across all power settings—a critical concept for AMT Powerplant certification.
Fuel Discharge Nozzle Function and Maintenance
Fuel discharge nozzles atomize and distribute fuel into the induction system or combustion chamber; understanding their design, flow characteristics, and maintenance keeps engines running efficiently and safely.
Throttle Body and Fuel Control Unit Operation
The throttle body and fuel control unit (FCU) work together to meter the precise air-fuel mixture delivered to aircraft engines, and understanding their operation is essential for AMT Powerplant certification.
Idle Mixture and Idle Speed Adjustment Procedures
Proper idle mixture and idle speed adjustment on reciprocating engines ensures smooth low-power operation, correct fuel-air ratios at idle, and clean acceleration without stumbling or roughness.
Fuel Injection System Troubleshooting and Leak Checks
Fuel injection systems deliver precise fuel-air mixtures directly to each cylinder, but leaks and metering faults can ground an aircraft fast — learn how to diagnose and correct them using FAA-approved procedures.
Vapor Lock Causes and Prevention in Fuel Metering Systems
Vapor lock occurs when fuel vaporizes inside the fuel system before reaching the engine, disrupting metering and causing power loss or engine stoppage — understanding its causes and prevention is essential for safe aircraft maintenance.
Fuel-Air Mixture Ratio and Engine Performance Effects
The fuel-air mixture ratio directly governs combustion efficiency, power output, and engine temperature in aircraft piston engines — understanding it is essential for safe operation and the AMT Powerplant exam.
Altitude Compensation and Automatic Mixture Control
Altitude compensation and automatic mixture control systems automatically adjust the fuel-air mixture as air density changes with altitude, preventing over-richening and maintaining efficient engine operation without constant pilot intervention.
More AMT — Powerplant subjects
Articles are original summaries grounded in the public-domain FAA handbooks and cite their source. ACS-aligned study aids — not a substitute for the official handbooks or regulations.