Question : You have studied major systems of an aircraft during

this course. In this assignment, you have to select your favorite

aircraft (fighter / cargo / commercial passenger) and choose any
system (only one system) of that aircraft you like the most. The
choice should be made based on the distinctive performance
features as compared to other aircraft of the same category. Write
at least 2000 words on that system covering the following aspects:
(a) System Overview (20) (b) Major Components (20) (c) System
Operation (20) (d) Comparison with any aircraft of same category
showing supremacy of your selected aircraft over the other one.
(40) Support your answer with relevant figures.

The Boeing 747, one of the largest commercial aircraft, features a sophisticated
hydraulic system crucial for various critical functions, including landing gear, flight
controls, brakes, and flaps. The hydraulic system operates by using fluid under pressure
to transmit power. A Hydraulic System is a force multiplying system that utilizes Pascal’s
law for it operation. A small force is applied over a small surface area and a large force
acts on the large output plate. The output Force is multiplied by a factor of the ratio
between the output and input area.

Boeing 747 Hydraulic System:

The Boeing 747 has four independent hydraulic systems which are numbered from 1 to
4, to ensure safety in case one may failure. Each system is pressurized by either engine-
driven pumps or electric pumps, and all systems use hydraulic fluid to operate aircraft
components. In case one system fails, the others can take over critical functions to
maintain safe operations.

Main Components of the of Boeing 747 Hydraulic System:

1. Hydraulic Pumps:
Engine Driven Pumps:

These are the primary pumps located on the engines and are powered by engine
rotation. Each of the four hydraulic systems has at least one Engine Driven Pump, which
generates high pressure as the engine turns during normal operation of aircraft.

Electric Motor Driven Pumps:

These pumps are especially use during ground operations or in the event of an engine
failure or in case of failure of any engine driven pump. These provide backup pressure.
They are powered by internal batters or alternator and hence can operate independently
of engine power or during engine failure.

Air Driven Pumps:

These pumps can be used to provide hydraulic pressure if both engine and electric
pumps fail. They are typically driven by compressed air from the aircraft’s pneumatic
system.

2. Hydraulic Fluid:

The hydraulic fluid used in the system is typically Skydrol, a phosphate-ester-based fluid
with fire-resistant properties. These hydraulic fluids have a high flash point and density
changes are negligible in operational Temperature. The Hydraulic fluid is circulated
throughout the system via hydraulic pumps.

3. Accumulators:

These are devices that store hydraulic fluid under pressure to ensure that the system
can respond quickly to demand l. They also act as dampeners to reduce system
vibrations and spikes in pressure. They also proved addition pressure in care multiple
operations are carried out simultaneously for example during landing or during takeoff.

4. Reservoirs:

Each system has a reservoir that stores hydraulic fluid. These reservoirs are pressurized
to ensure a continuous supply of fluid to the pumps. They have filters to remove
contaminants from the fluid.

5. Control Valves:

Control valves regulate the flow of hydraulic fluid to various components. These valves
direct fluid to the desired system, such as the landing gear, flight controls, or brakes,
depending on pilot inputs/requirement.
Major Functions of the Hydraulic System:

1. Landing Gear Operation:

Landing gears are retracted to reduce drag

during flight and the deployed during landing.
The hydraulic system powers the extension
and retraction of the landing gear. It provides
the necessary force to move the heavy
landing gear components, including the main
wheels and nose wheels.

2. Flight Control Surfaces:

The system operates primary flight control

surfaces, such as ailerons, elevators, and
rudders, which are essential for the aircraft's
maneuverability. It also powers secondary
flight controls like slats, flaps, and spoilers,
which are used during takeoff, landing, and in-
flight adjustments.
 3. Braking System:

Hydraulic pressure is used to apply the brakes on the landing gear during ground
operations. The braking system is highly critical, especially during landings at high
speeds. The breaking force need to insure that the aircraft does not over shoot the
runway.

4. Thrust Reversers:

The hydraulic system powers the thrust reversers,

which redirect engine thrust forward to help slow
the aircraft upon landing. This function is critical
for safe deceleration and is deployed in most
modern aircrafts.

Hydraulics and Safety:

One of the Key feature of The Boeing 747 hydraulic system is designed with redundancy
for safety:

Multiple Systems:

With four independent hydraulic systems, if one or two systems fail, the remaining
systems can still provide enough power to critical functions. Each system is assigned
specific tasks, but in case of emergency / failure of a system other can take over
function.

Isolation Valves:

These valves can isolate portions of the hydraulic system in case of a leak or failure,
ensuring that the rest of the system remains operational.
Distribution of Hydraulic Power:

Each of the four hydraulic systems powers specific parts of the aircraft:

 System 1:

Typically powers the left outboard ailerons, elevators, rudders, and a portion of
the landing gear system.

 System 2 and 3:

These systems generally power the inboard flaps, flight spoilers and other
secondary control surfaces. Systems 2 and 3 also have critical backup functions,
including powering the main flight controls in case one fails.

 System 4:
 Similar to System 1, it powers the right outboard flight controls, landing gear, and
other auxiliary functions.

System Pressures:

The hydraulic systems operate at a pressure of approximately 3,000 pounds per square
inch, which is standard the standard for most large commercial aircraft. This high
pressure allows for the efficient transmission of power to heavy-duty components like
landing gear and flight control surfaces. It also insures quick response of air craft to
piolet input.

Monitoring and Maintenance:

The hydraulic systems are continuously monitored during flight for pressure, fluid levels,
and temperature. Warning systems alert the pilots if any issues may arise which then
can be isolated as mentioned in previous passages. Maintenance crews regularly check
for leaks, filter cleanliness, and the condition of the hydraulic fluid to prevent
contamination.

Comparison of Boeing 747 with A 370:

The hydraulic systems of both the Airbus A320 and Boeing 747 handle essential tasks
like flight control, landing gear operation, and braking. However, the Boeing 747’s
system stands out with its more advanced architecture, superior redundancy, and robust
operational philosophy, reflecting its larger size, more complex design, and Boeing’s
engineering excellence. Here's a comparison highlighting these distinctions:

1. Hydraulic System Configuration:

 Boeing 747:

The 747 has four independent hydraulic systems (systems 1, 2, 3, and 4) for
redundancy and safety. Each system operates at a pressure of 3,000 psi.

The four systems are designed to ensure that even if one or more systems fail, the
remaining ones can still perform critical functions like operating flight controls and the
landing gear.

These systems are powered by engine-driven pumps, electric motor driven

pumps, and air driven pumps, ensuring high reliability across different phases of
flight.

 Airbus A320:

The A320 has a simpler configuration with three hydraulic systems: Green, Yellow,
and Blue.
Each of these systems operates independently at 3,000 psi and is powered by different
types of pumps:

 The Green system is powered by engine-driven pumps.

 The Yellow system is powered by an engine-driven pump and an
electric pump for backup.

The Blue system is powered by an electric pump and includes a Ram Air Turbine
(RAT), which can deploy in case of a complete electrical failure to provide hydraulic
pressure for essential functions.

Power Sources and Backup Systems:

 Boeing 747:

The 747 uses a combination of engine-driven pumps, electric pumps, and air-
driven pumps. The air-driven pumps provide a backup in case of engine or electric
pump failures, ensuring constant hydraulic pressure in all phases of flight.

The 747's design is focused on redundancy, with each system capable of powering
critical components, ensuring multiple backups for flight-critical functions like landing
gear and flight controls.

 Airbus A320:

The A320’s three systems are powered by engine-driven pumps and electric pumps.
A major backup in the A320 is the Ram Air Turbine (RAT), which deploys in the case of
a complete electrical and hydraulic failure. It is designed to maintain minimal hydraulic
pressure for essential flight control functions in emergencies.

The Yellow system has an electric pump that can operate independently on the ground,
useful for ground operations like braking or cargo door operations when engines are off.

Emergency Operations:

 Boeing 747:

In the case of a major hydraulic failure, the 747 relies on the multiple independent hydraulic
systems to ensure redundancy. If one or two systems fail, the remaining systems are designed
to take over most flight-critical operations.

The air-driven hydraulic pumps can also kick in to provide pressure if other sources fail.

 Airbus A320:
The A320 is equipped with the Ram Air Turbine (RAT), which can be deployed to power the
Blue system in the event of total engine or electrical power failure. This allows the aircraft to
maintain minimal control authority, enough to land safely.

The electric pump in the Yellow system also provides backup hydraulic power for braking
and landing gear in emergencies.

Conclusion:

The hydraulic system of the Boeing 747 is an essential aspect of the aircraft's operation,
providing the power to move critical components like the landing gear, flight controls,
and brakes. Its design incorporates redundancy, with four independent systems to
ensure the safety and reliability of the aircraft, even in the case of partial system failure.
The four Hydraulic Systems permit the highest degree of reliability per system operation
with all major controls powered by dual-tandem actuators or having redundancy in
location of operation. The Boeing 747 is an iconic aircraft known for its distinctive humpback
design, size, and capabilities. Often referred to as the "Queen of the Skies," it was the first wide-
body "jumbo jet" and revolutionized air travel by allowing airlines to transport significantly more
passengers and cargo over long distances. Here’s a detailed overview of its features and
contribution.