11.16 pneumatic and vacuum Flashcards
what does the pneumatic system do
transfers energy through manipulation of air pressure
what are the sources for pneumatic systems
engines, APU, ground air power units
what 4 categories does the pneumatic/vacuum system fall into
vacuum, low pressure, medium pressure, high pressure
what psi does the low pressure system run at
1-10 psi
what psi does the medium pressure system run at
50-150 psi
what psi does the high pressure system run at
1000-1300 psi
what is the pneumatic system primarily supplied by
engines
what is the duct called that connects the right and left systems
crossover duct, cross bleed manifold
what must be ensured before working on any pneumatic system
its depressurised
where can bleed air be taken from in the engine
LP bleed port, IP bleed port, HP bleed port
how is it chosen what bleed port the pressurised air is taken from on the engine
engine speed
when are the LP and IP bleed ports used
take off, climb and cruise
when is the HP bleed port used
when the IP or LP is inadequate
what are the 2 disadvantages of using bleed air from the engine compressors
air contamination risk, reduced engine performance
what 2 different ways does the APU supply pneumatic air
directly bleeding from compressor, load compressor driven by turbine
what are the 2 actuated devices on the APU
inlet guide vanes, surge control valve
when is bleed air available from the APU
running above 95%
ground sources for bleed air can either be
fixed or portable cart-type
what 3 groups can compressors be split into
positive displacement, multi stage, centrifugal
what can drive the centrifugal compressor
accessory gearbox, engine bleed air
when is the centrifugal compressor drive ratio at maximum
operating at high altitude with low engine RPM
in a pneumatic air high pressure storage bottle what is the psi range
1000-3000 psi
what are air pressure pumps commonly known as
air compressors
what does the air compressor do
absorbs atmosphere air, compresses it, sends it to systems
what are the 2 main positive displacement, vane type vacuum pumps
wet type, dry type
are dry pumps self lubricating
yes
aircraft without the facility for an engine driven vacuum use what
venturi system
what are common problems with venturi
ice formation, damage/deformation, blocked filter cartridge, leaking plumbing
what is a PRV
pressure relief valve
what is the purpose for pressure relief valves
prevent system damage
what can restrictor valves do
increase or decrease airflow
where is the moisture separator located in the pneumatic system
downstream of the compressor
when the aircraft is supplied with air on ground what must happen in the cabin
a door or window must be opened
what are pneumatic manifold ducts made from
strong, corrosion resistant, lightweight tubing
what can a gold coating protect tubing from
hydrocarbon contamination
what must the temp stay between in the pneumatic system
160-200 degrees celcius
what do the manifold pressure sensors do
monitors air supply
what is duct pressure controlled at (psi)
20 psi
what is fan air used for
cooling
what is the FAV
fan air valve
if a leak occurs in an air duct what happens
overheat
what is the pneumatic system controlled with
panel in cockpit or automatically
where are most aircrafts pressure sensors mounted
left and right duct distribution systems
starting the APU requires what
ground air unit or an engine running
what is TAT
total air temperature
