RMIT飞行训练课件－ RMIT飞行训练课件－Pitot Static System 皮托静压系统

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PITOT / STATIC SYSTEMS
Aim: To understand the principles of operation behind a pitot / static system,
considering the possible errors and limitations involved.
Application:
- Used when relying on the pressure instruments.
- ASI, ALT and VSI.
Revision:
 Static Pressure
- pressure due to weight of air molecules pushing down. Reduces with
increased altitude.
 Dynamic Pressure
- pressure due to relative movement. Depends on density and velocity.
- PD =
 Total Pressure
- PT =
Definitions:
 Static Vent
- measures PS and usually flush-mounted on fuselage side.
Brief 28
RMIT Flight Training Pitot/ Static Systems
 Pitot Tube
- measures PT and mounted where airflow not greatly disturbed. Usually on
outer wing section.
- pitot heat provided to guard against ice.
 Alternate Static Source
- emergency static port, found in cockpit, used in an emergency.
- slightly lower than atmosphere pressure due to slight suction created by
door seals.
Principles:
 A typical pitot/ static system is shown below:
 Airspeed Indicator (ASI)
- measures PD (½V2) and extracts V to show aircraft velocity.
- diaphragm is used filled with pitot pressure (PT) and PS surrounding it. The
diaphragm will position itself, and the pointer will then relate the difference.
PD = PT – PS
Brief 28
RMIT Flight Training Pitot/ Static Systems
 Altimeter (ALT)
- uses PS only and relates it to height
- contains an aneroid capsule exposed to PS from the static vent. Fixed
diaphragm contains air as a reference. As aircraft climbs, PS reduces and
the capsule expands driving the pointer via mechanical linkages.
- time lag does exist
 Vertical Speed Indicator (VSI)
- uses PS only, and works on the principles of converting rate of change of
PS to a rate of change of altitude
- instrument is a flexible capsule exposed to PS housing a choke valve.
- aircraft descends, PS increases. This pressure is fed into the capsule and
the choke valve. Therefore there is a delay to the increase in PS in the
capsule. The capsule then expands driving a pointer until the pressure
equalises with that in the choke valve.
Considerations:
 Instrument Errors
- due to imperfections in the design and installation.
 Instrument Lag
- response time of pressure instruments can be slow due to long lines or
rapid pressure changes.
 Position Error
- poor design and placement of vents may not be representative of the free
atmospheric pressure.
Brief 28
RMIT Flight Training Pitot/ Static Systems
 Blockages
ASI ALT VSI
Pitot Climb Over read - -
Blockage Descent Under read - -
Static Climb Under read Under read Under read
Blockage Descent Over read Over read Over read
Airmanship:
- Know where the alternate static source is located
- Always check pitot and static vents during pre-flight
Brief 28
RMIT Flight Training Pitot/ Static Systems
Brief 28
RMIT Flight Training Pitot/ Static Systems

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感谢楼主万分感谢感谢万分

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谢谢楼主，我正准备去RMIT读书