Flowmeter Output and High-Pressure Fuel Filter Quiz

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What are the three main categories of metering requirements for the engine fuel system?

Steady running state, smooth maximum rate accelerations, rapid deceleration without risking combustion chamber flameout

What is the purpose of the normal running line in the engine fuel system?

It specifies the fuel requirement for a given rpm

What happens when there is an increase in fuel flow in the engine fuel system?

It initially gives rise to a back pressure which restricts compressor air delivery

How does the engine fuel system handle acceleration?

Acceleration ceases when the engine stabilizes at the steady state demand line Signup and view all the answers

What effect does a decrease in fuel flow have on the engine in the fuel system?

It reduces the available energy in the gas stream, causing the engine to decelerate Signup and view all the answers

How does the engine fuel system avoid flameout?

Sufficient fuel flow must be maintained to avoid flameout Signup and view all the answers

What is the purpose of controlling the fuel spill in the HP pump?

To allow over fueling during acceleration or under fueling during deceleration as required. Signup and view all the answers

At what approximate percentage of HP does the minimum fuel spill occur?

8% Signup and view all the answers

Where does the HP pump receive its fuel supply from?

From the Low-Pressure (LP) fuel pump. Signup and view all the answers

What is the purpose of the Low-Pressure (LP) Fuel Filter Differential Pressure (DP) Transducer?

To measure differential pressure across the LP fuel filter and the absolute pressure of the fuel supply to the HP pump. Signup and view all the answers

What is the role of the Fuel Return to Tank (FRTT) Differential Pressure Transducer?

To measure the differential pressure across the FRTT mounting and provide the oil filter differential pressure measurement for the engine oil system. Signup and view all the answers

What is the function of the LP fuel filter differential pressure transducer when the differential pressure rises above the second EEC-predetermined threshold?

To display a maintenance message in the cockpit indicating complete blockage of the filter and the filter bypass valve fully open. Signup and view all the answers

What is the purpose of the Fuel Metering Unit (FMU)?

The FMU meters the fuel required by the engine in response to control signals generated by the EEC. Signup and view all the answers

How is positive fuel flow obtained with the engine running?

Positive fuel flow is obtained when the aircraft fuel control switch is in the 'ON' position and both Independent Overspeed Protection (IOP) channels for that engine are not demanding engine shutdown. Signup and view all the answers

What happens during deceleration in the FMU operation?

During deceleration, the EEC command to increase fuel flow causes the EHSV to direct HP servo fuel to the Fuel Metering Valve (FMV) bottom piston, allowing it to open. Signup and view all the answers

How is engine shutdown achieved by the EEC and FMU?

Engine shutdown is achieved by the EEC and FMU through fuel switch command, COSS 'OFF' solenoid energizing, and manual closing and opening of the PRSOV using solenoid coils. Signup and view all the answers

What is the purpose of the Fuel Switch in the FADEC and FMU interface?

The fuel switch is manually selected by the pilot to either the 'OFF' or 'ON' position and interfaces with both the EEC and the FMU to close and open the PRSOV using solenoid coils and indicate the switch position to the EEC. Signup and view all the answers

What does the Fuel Flow Transmitter provide an indication of, and how is the fuel flow indication to the cockpit derived?

The Fuel Flow Transmitter provides an indication of engine fuel flow to the Engine Instruments and Crew Alerting System (EICAS) system. Signup and view all the answers

What is the purpose of the fuel spray nozzles in the combustion chamber?

To deliver metered fuel into the combustion chamber in a pattern suitable for maximum combustion efficiency. Signup and view all the answers

How is the fuel atomized in the fuel spray nozzles?

The fuel is forced through a narrow circumferential orifice and mixes with HP delivery air on exit, causing it to become atomized. Signup and view all the answers

What happens to the fuel in the fuel burner nozzles and manifold during engine shutdown?

The back pressure in the combustor chamber forces the fuel out of the fuel burner nozzles and manifold in reverse direction, and it is collected in the drains tank. Signup and view all the answers

What are the indications displayed in the Fuelsynoptic 213 window?

Digital readings of engine fuel flow and two pointer arrows to indicate the difference in fuel flow between the two engines. Signup and view all the answers

What are the limitations for the engine fuel temperature?

Minimum: -40°C, Maximum Unrestricted: +140°C, Maximum (15 Minute) Transient: +165°C Signup and view all the answers

What is the purpose of the dual ignition system in the BR725 engine?

To produce an electrical spark to ignite the fuel-air mixture in the combustion system. Signup and view all the answers

What is the purpose of the Fuel Temperature Transducer?

To provide an electrical signal representative of the fuel delivery temperature at the FCOC fuel outlet. Signup and view all the answers

What is the absolute filtration rating of the HP Fuel Filter?

250 micron Signup and view all the answers

What is the function of the Overspeed and Splitter Unit (OSU) during engine shutdown?

To allow fuel to be purged through the manifold segments in reverse direction from the fuel nozzles through the OSU into the drains tank. Signup and view all the answers

What is the material used for the filter element of the HP Fuel Filter?

Stainless steel Signup and view all the answers

What is the primary purpose of the Fuel Manifold?

To provide fuel distribution to 20 fuel nozzles by supplying HP fuel from the OSU to 10 fuel spray nozzles on the upper half and 10 on the lower half of the engine. Signup and view all the answers

How does the Overspeed and Splitter Unit (OSU) minimize fuel anomalies during low flow conditions?

By dividing the engine metered fuel flow equally between the upper and lower burner manifold segments. Signup and view all the answers

What is the purpose of alternating the ignition systems for each ground start sequence?

Equalize igniter plug usage and ensure no dormant faults exist Signup and view all the answers

When are both ignition systems energized in flight?

When water ingestion or a surge I stall is detected Signup and view all the answers

How does the EEC detect electrical faults in the ignition system?

By using internal voltage and current monitors Signup and view all the answers

What components make up the High Energy Ignition Units?

Input EMI Filter, Power Control Section, Discharge Section Signup and view all the answers

What is the function of the input EMI filter in the ignition unit?

Filters out high-frequency elements and prevents contamination of the aircraft DC power supply Signup and view all the answers

How is the energy released by the ignition unit to ignite the fuel I air mixture?

As a capacitive discharge pulse of energy Signup and view all the answers

What is the purpose of the resistor in the discharge section of the ignition unit?

To bleed off power from the capacitor when the power supply is removed Signup and view all the answers

What are the two conductors in the ignition leads responsible for?

Inner wire conductor: current routing from the ignition unit to the igniter plug, Outer conductor: current routing from the igniter plug back to the ignition unit case Signup and view all the answers

What is the purpose of the wire-braid outer cover in the ignition leads?

Protection for the flexible conduit and conductors Signup and view all the answers

What is the function of the flexible conduit in the ignition leads?

To route the inner and outer conductors and provide flexibility Signup and view all the answers