Shut-off Valves Overview

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Questions and Answers

What is the primary function of the speed governor during governed operation?

To increase the engine's maximum speed

To enhance aircraft climb performance

To maintain a steady governed state (correct)

To regulate fuel mixture automatically

What happens to inlet ram air pressure when an aircraft is descending?

It decreases and mass airflow decreases

It increases and mass airflow remains constant

It increases and mass airflow increases (correct)

It decreases and mass airflow increases

What component is influenced by the inlet and burner pressure bellows?

Pilot servo rod valve

Multiplying lever movement (correct)

Power lever position

Flyweight speeder spring

In the context of acceleration, what effect does moving the power lever upwards have on the spring cap?

It compresses the flyweight speeder spring Signup and view all the answers

What occurs when the flyweights are forced into an underspeed condition?

The pilot valve rod moves downwards Signup and view all the answers

Which variable does NOT affect the operation of the engine during governed or steady operation?

Ambient temperature Signup and view all the answers

How does the engine react to a decrease in inlet air pressure due to climbing?

Adjusts fuel mixture ratio Signup and view all the answers

What is the outcome of a stable power lever position during steady operation?

It necessitates predictable engine reactions to external conditions Signup and view all the answers

What is the main advantage of the vaporiser nozzle in combustion engines compared to atomising nozzles?

It provides a stable combustion at low RPM. Signup and view all the answers

How does the vaporising nozzle discharge fuel compared to the atomiser nozzle?

Upstream then downstream after a turn. Signup and view all the answers

What is the role of the primer or starting fuel system in relation to the vaporising nozzles?

To provide an effective spray pattern for starting. Signup and view all the answers

Which type of vaporiser nozzle has multiple outlets?

Tee-shaped vaporiser. Signup and view all the answers

Why might additional atomising nozzles be used in conjunction with vaporising nozzles during engine operation?

To assist with the starting phase. Signup and view all the answers

What is the primary flow characteristic of vaporising nozzles during operation?

They create a slow-moving, fine spray. Signup and view all the answers

What is the primary function of the redundant channels in an EEC?

To ensure continuous operation despite multiple faults. Signup and view all the answers

What happens when both channels of the EEC fail?

Actuators are spring-loaded to a failsafe position. Signup and view all the answers

Which mode does the EEC enter when both channels fail and the last known ambient pressure signal is used?

Soft Reversionary mode. Signup and view all the answers

What components does the EEC control aside from the primary engine functions?

Fuel and air oil coolers, bleed valves, and variable stator vanes. Signup and view all the answers

How does the EEC achieve an interface between its signal and fuel flow?

By using a hydromechanical unit with an electrical hydraulic servo valve. Signup and view all the answers

What does the Engine Rating Plug select in the EEC?

The appropriate software for the thrust rating of the engine. Signup and view all the answers

What role do dual sensors play in the EEC structure?

To provide feedback via valves and actuators. Signup and view all the answers

In the context of EEC functionality, what is a characteristic of the Hard Reversionary mode?

It uses a fixed corner-point ambient temperature. Signup and view all the answers

What is the primary function of a motor-driven gate valve?

To move a valve gate in and out of the passage Signup and view all the answers

What advantage does a solenoid-operated valve have over a motor-driven gate valve?

It is quicker to open or close Signup and view all the answers

How does the solenoid valve maintain its open position after being activated?

By a spring-loaded locking plunger engaging the valve stem Signup and view all the answers

What triggers the low fuel pressure switch to close?

A drop in normal fuel pressure Signup and view all the answers

When a solenoid coil is energized, what effect does it have on the valve stem?

It exerts a magnetic pull that raises the stem Signup and view all the answers

What must occur for the solenoid-operated valve to close after being opened?

Current must be directed to the closing solenoid coil Signup and view all the answers

What role does the warning light in the cockpit play concerning fuel supply?

Signals that the selected tank is empty Signup and view all the answers

What happens to the locking plunger when the closing solenoid coil is energized?

It moves to disengage from the valve stem Signup and view all the answers

What happens when the power lever is opened in relation to the dump valve?

The dump valve opens the passageway to the manifolds. Signup and view all the answers

What is the function of the dump valve after engine shutdown?

To dump or drain fuel from the fuel manifolds. Signup and view all the answers

What effect does residual engine heat have on fuel if not properly managed?

It leads to fuel boiling and solid deposits. Signup and view all the answers

Under which condition does fuel start to flow into the main manifold?

When fuel pressure is slightly above idle. Signup and view all the answers

What is the purpose of the pressurising valve in the fuel system?

To maintain a preset fuel pressure for combustion. Signup and view all the answers

How does the construction of pressurisation and dump valves differ?

Their construction and operation can vary by manufacturer. Signup and view all the answers

What triggers the closing of the fuel passage after the shutdown?

Loss of pressure signal holding the dump port closed. Signup and view all the answers

What issue does the dump valve help prevent in a gas turbine engine?

Clogging of finely calibrated passageways. Signup and view all the answers

Study Notes

Shut-off Valves

Common shut-off valves include motor-driven gate valves and solenoid-operated valves.

Motor-Driven Gate Valve

Utilizes a reversible electric motor to move a sliding valve assembly.
The motor regulates the position of the valve gate, controlling fuel flow.

Solenoid-Operated Valve

Offers quicker actuation compared to motor-driven counterparts.
Operates via electronic current that creates magnetic pull, opening and holding the valve until current is reversed.

Low-Pressure Transmitters

Alerts pilots when fuel in the supplying tank runs low or a boost pump fails.
The low fuel pressure switch closes at low pressure, activating a cockpit warning light.

Governed Operation

Maintains steady engine operation as per pilot input regardless of external factors like aircraft speed and altitude.
Senses inlet ram air pressure changes to adjust fuel mixture ratios through pressure bellows.

Acceleration Mechanism

Power lever movement compresses the spring cap, affecting pilot servo valve operations and leading to engine acceleration.

Electronic Engine Control (EEC)

Comprises two redundant processing channels that manage engine data and operation.
Capable of continuing function amid multiple faults and switches between active and standby channels efficiently.

Fuel Control Integration

The EEC interfaces with hydromechanical units to regulate fuel flow using various actuators, ensuring stable engine operation across different conditions.

Dump Valve Functionality

Allows for draining fuel from manifolds post-shutdown to prevent issues like boiling or after-burning, which can cause deposits.

Operation of Pressurisation and Dump Valves

Changes state based on power lever movement, with pressure signals managing flow to and from fuel manifolds.

Vaporising Nozzles

Two types: tee-shaped (dual outlets) and cane-shaped (single outlet).
Vaporisers produce a slow-moving spray, enhancing combustion stability at low RPMs; often used with atomising nozzles for starting fuel.

Primer or Starting Fuel System

Small atomising nozzles may assist during the starting phase by injecting fuel into the combustor prior to engine spool-up.

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Description

This quiz covers different types of shut-off valves, focusing on motor-driven gate valves and solenoid-operated valves. Learn about their mechanisms, advantages, and how they control fuel flow in various applications. Test your understanding of these essential components in fluid control systems.