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UNIVERSITY OF SALENTO – SCHOOL OF INDUSTRIAL ENGINEERINGDEPT. OF ENGINEERING FOR INNOVATION – Lecce-Brindisi (Italy)

MASTER OF SCIENCE IN AEROSPACE ENGINEERINGMASTER OF SCIENCE IN AEROSPACE ENGINEERING

PROPULSION AND COMBUSTIONPROPULSION AND COMBUSTION

Aircraft Systems Mechanical, Electrical and Aircraft Systems Mechanical, Electrical and Avionics.pdfAvionics.pdfChap. 6 - Pneumatic SystemsChap. 6 - Pneumatic Systems

LECTURE NOTES AVAILABLE ON LECTURE NOTES AVAILABLE ON http://www.ingegneria.unisalento.it/scheda_personale/-/people/antonio.ficarella/materiale

Prof. Eng. Antonio FicarellaUniversity of Salento - [email protected]

REVIEW R01

DATE 17/01/2014

FILE propASpneumaticR01.odp

RESPONSIBLE Antonio [email protected]

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INTRODUCTION

use of engine bleed air for a number of aircraft systems, either for reasons of heating, provision of motive power or as a source of air for cabin conditioning and pressurisation systems

Medium-pressure bleed air is used to start the engine in many cases, either using air from a ground power unit, APU or crossbled from another engine on the aircraft which is already running.

Bleed air is also used to provide anti-ice protection by heating the engine intake cowling and it is also used as the motive power for the engine thrust reversers.

pressurising hydraulic reservoirs, providing hot air for rain dispersal from the aircraft windscreen, pressurising the water and waste system and so on. In some aircraft Air Driven Pumps (ADPs) are used as additional means of providing aircraft hydraulic power

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Use of Bleed Air

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As well as the main aircraft engines the Auxiliary Power Unit (APU) is also a source of high pressure bleed air.

Some aircraft designs are actively considering the use of in-flight operable APUs to assist in in-flight engine re-lighting and to relieve the engines of offtake load in certain areas of the flight envelope.

By means of a cross flow Shut-Off Valve (SOV) the system may supply air to the opposite side of the aircraft during engine start or if the opposite engine is inoperative for any reason

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A pneumatically controlled High Pressure Shut-Off Valve (HP SOV) regulates the pressure of air in the engine manifold system to around 100 psi and also controls the supply of bleed air from the engine.

The Pressure-Reducing Shut-Off Valve (PRSOV) regulates the supply of the outlet air to around 40 psi before entry into the pre-cooler.

The valve position is signalled by means of discrete signals to the bleed air controller and pressure switches provide over and under-pressure warnings.

The various pressure, flow and discrete signals enable the bleed air controller Built-In Test (BIT) to confirm the correct operation of the PRSOV and fan control valve combination.

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Engine Bleed Air Control

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Bleed Air System Users

Wing and Engine Anti-Ice

The protection of the aircraft from the effects of aircraft icing represents one of the greatest and flight critical challenges which confront the aircraft.

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The presence of hot air ducting throughout the airframe in the engine nacelles and wing leading edges poses an additional problem; that is to safeguard against the possibility of hot air duct leaks causing an overheat hazard. Accordingly, overheat detection loops are provided in sensitive areas to provide the crew with a warning in the event of a hot gas leak occurring.

A number of low speed commercial aircraft employ a method of de-icing based on a flexible rubber leading edge ‘boot’ that is inflated by air pressure to dislodge ice built up on the surface.

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Engine Start

Thrust Reversers

Hydraulic Systems

Pneumatic pressure is commonly used to pressurise the aircraft hydraulic reservoirs.

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Pitot Static Systems

the pitot static system is an instrumentation system used to sense air data parameters of the air through which the aircraft is flying.

Without the reliable provision of air data the aircraft is unable safely continue flight. The pitot static system is therefore a high integrity system with high levels of redundancy.

An aircraft will have three or more independent pitot and static sensors

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minimise the effect of the boundary layer

a heater element is incorporated to prevent the formation of ice that could block the sensor or create an erroneous reading. The pitot heating element is active throughout the entire flight.

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Innovative Methods of Pitot-Static Measurement

• Pitot pressure

• Static pressure

• Angle of attack (α)

• Angle of sideslip (β)