pneumatic Systems

Question 1

Pneaumatics is used

Answer 1

~Light a/c to power gyroscope
~Light twins use to de icing boots
~Large a/c for air conditioning,pressurisation and ice protection
~large a/c may use engine bleed air to power the pneumatic sys
~requirements to heat and ventilate in all a/c with enclosed cabins

Question 2

Advantages

Answer 2

Air readily availble
~pneumatic is light weight
~piston a/c genereate compressed air using compressors
~bleed system
~smaller fire risk
~used as a shock asborber

Question 3

Disadvantages

Answer 3

~cannot match hyd systems for speed and energy transmission
~difficult to seal
~difficult to trace leaks
~potential threat extremelty hot
~bleed air reduces enigne efficiency

Question 4

Light a/c pneu

Answer 4

A small engine driven vacuum pump is used to genrate the supply
~the pump is driven by engine via a quill shaft which is designed to shear if the torque load it experience become excess.

Vacuum gauge on the instrument panel confirms that the pump is operating satisfactory

Question 5

Three usual sources of compressed air for gas turbine a/c

Answer 5

Bleed air from the main engines
Compressed air from the apu
Compressed air supply by gpu

Question 6

Bleed air

Answer 6

You can’t choice how much you can get between High pressure and low pressure stage ,but only operate the shut off valve.

Because of the pressure variation with rpm bleed air is taken from two different sections

Question 7

Overheat detection

Answer 7

Each loop protects an area know as zone
Typically there are two loops in each zone
Is it fine to operate wiht one loop inop but only very strick limited time period

Question 8

Where are the Indication of the bleed air system parametres shown and what are the parametres shwon?

Answer 8

Indication of the bleed air in displayed in EICAS or ECAM.

Parameters&raquo_space;temperature,pressure and valve position sensors

Question 9

Bleed air tapping

Answer 9

~Bleed air passes through high pressure shut off valve(HPSOV) limits the pressure to about 100 psi

~then goes through pressure reducing shut off valve (PRSOV) reduces pressure to 40 psi

~pre cooler uses LP fan air to reduce the temperature

Question 10

Shut off valve operation

Answer 10

Operated pneumatically but controlled eletrically

Question 11

Pneumatic system architecture

Answer 11

~stainless steel&raquo_space; for high temperature and or high pressure ducts
~light alloy&raquo_space; for intermediate temperature and pressure ducts
~plastic /fibreglass&raquo_space; for low temperature or low pressure ducts

Question 12

Principle bleed air malfunctions

Answer 12

~over temp
~over pressure
~low pressure
~over heat /duct leak