24- Aircraft Pneumatic Systems

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PNEUMATIC SYSTEMS
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The learning objective of this presentation,
To develop the student's knowledge of the
vacuum system to meet the basic functions
in vacuum system that supply essential
instruments of the aircraft and ability to
detect abnormal or unsafe operation and
responding to a vacuum system failure
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Aircraft Pneumatic System Intro
Vacuum Systems
Pneumatic Use in Small Aircraft
Pneumatic System Components
Air Pumps
Pneumatic System Operation
Actions before every flight
Failure Causes
Early Recognition
Emergency Procedures
Spatial Disorientation
Redundancy Options
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Sometimes called vacuum pressure systems
Aircraft Pneumatic Systems power
Instruments, *landing gear, *flaps, air
conditioning, windows, doors and more
In light Aircraft, Suction Pressure Gauge
shows Vacuum System Pressure
• Pumps
• Relief Valves
• Vacuum Air Filter
• Suction Gauge Gyro
instruments:
- Attitude Indicator
- Heading Indicator
• Gyro compass
• Artificial Horizon
• Turn coordinator
•Air Pump
•Vacuum Regulator
•Inlet Air Filter
•Overboard Vent Line
•Gauges:
– Attitude Indicator
– Heading Indicator
•System Indicators
– Suction Gauge – Gyro
Flag
– Annunciator Lights
Pneumatic Air Filter
- Prevents system
contamination
- Remove air particulates
- Clean air is essential to
good operation
Pneumatic Pressure
Regulator
- Prevents System
over pressurization
- Insures proper
calibration
Heart of pneumatic system is pressure or vacuum air pump
(Usually engine driven)
• Two basic types :
• Wet air pumps use engine oil to lubricate pump internally
• Dry air pumps - more common –have graphite vanes inside pump
casing - self-lubricate as pump rotates
•Filtered Air is pulled through
system by vacuum pump
•Evacuated air passes through
instrument case causes gyro
to spin
•Spinning gyros provide
“rigidity in space” for
instrument references
•Air exhausts through Gyro
Pressure Gauge exhaust port
– Gauge measures system
pressure
•Failure Warning Systems
Check for oil leaks
Check the hose
And clamps for
Oil leaks
Check for
loose fittings
that allow
contaminants
into the
system
Check for
external
damage
• System Contamination
- Solid particles in pneumatic
system damage pump
and plug valve openings
– Liquids from oil, water, or engine
cleaning solvents
• Restriction/ leaks within the system
-A loose fitting or damaged hoses
-Worn out, misused, or incorrectly
routed hoses
• Sudden changes in engine speed
- Abrupt engine deceleration
- Sudden engine stoppage
• Pneumatic System health can be
determined by the indications on
either the vacuum gauge or flags on
the attitude indicator
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Inaccurate/conflicting Instrument
information
Suction/pressure gauge indicates outside
normal operating (green) range
Spotting pneumatic system failure early
reduces chances of spatial disorientation
95% are Fatal
1995-2004 Accidents
cause by vacuum Failure
5% non Fatal
1st Qtr
2nd Qtr
 While pneumatic system failures alone
do not cause accidents, spatial
disorientation does, and tragically
these accidents are almost always
fatal
• Activate a back up power supply for
pneumatics ( aux Vacuum pump if have)
• Maintain partial panel instrument flying
- Cover up or simulate loss of flight instruments
• Make timed turns
• Notify ATC
• In IMC –seek and fly VMC
When your instruments disagree, confusion,
dizziness, and uncertainly can cause loss of
control. Spatial disorientation occurs quickly when
outside visual reference
is poor such as night, IMC , Haze
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Electrical Power Instruments
Secondary Air pump ( Electric Aux Vacuum
Pump)
Pressure differential Switch
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Pneumatic Systems fail at unexpected times
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The danger , in the event of pneumatic system
failure is spatial disorientation
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Have a good knowledge what power systems on
the aircraft you fly
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Practice on the partial panel Flying and be
familiar with aircraft instruments
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Whether you rent, own, or operate become
familiar with the maintenance history of the
Aircraft

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