30 Questions
What is the primary function of the bimetal construction in the airspeed indicator?
To counteract the expansion of the capsule due to temperature changes
What do the red radial lines on the airspeed indicator represent?
The maximum speed limited by structural considerations of the airframe
What is the significance of the green or white range on the airspeed indicator?
It indicates the stall speed of the aircraft, dependent on the configuration of the flaps and/or landing gear
What is the purpose of the amber caution speed range on the airspeed indicator?
To require smooth turbulent-free conditions for safe operation
What is the term for the maximum speed limited by structural considerations of the airframe?
Vne
What is the significance of the airspeed indicator markings for pilots?
To provide a visual aid for pilots to operate the aircraft within safe limits
What is the primary function of a pitot probe in an aircraft?
To measure airspeed
What is the purpose of a calibrated drain hole in a pitot probe?
To allow moisture to escape without affecting the sensed pressure
What is the name of the detecting element used to measure static pressure in an aircraft?
Static port
What is the purpose of a powerful electrical heater element in a pitot probe?
To heat the airstream to prevent moisture from freezing
What is a common issue with the simple tube design of a pitot probe?
Moisture in the airstream can collect in the tube and cause erroneous airspeed readings
In some light aircraft, what is the static vent often simply?
A hole drilled in the fuselage skin
What is the primary variable measured by the conventional airspeed indicator in a Machmeter?
Airspeed
What is the purpose of the aneroid capsule in the Machmeter mechanism?
To measure altitude
How is the altimeter mechanism calibrated in the Machmeter?
To QNE
What is the effect of temperature on the speed of sound in the Machmeter?
It is variable, but compensated for by the altitude measurement
What drives the indicator pointer in a Machmeter?
A series of rocking shafts and levers
What is the advantage of combining a Machmeter and airspeed indicator into one instrument?
Saved space on the panel
What is the function of the calibrated leak in the metering unit of a Vertical Speed Indicator?
To vent static pressure to the interior of the case
During straight and level flight, what is the position of the pointer on the dial of a Vertical Speed Indicator?
At the 0 feet per minute position
What is the effect of a decrease in pressure inside the capsule of a Vertical Speed Indicator?
The capsule compresses
What is the purpose of the capillary tube in a Vertical Speed Indicator?
To supply static pressure to the inside of the capsule
What is the component that connects the measuring element to the indicating element in a Vertical Speed Indicator?
Rocking shaft and sector gear
In what type of flight is the static pressure constant and there is no movement of air through the metering unit orifice?
Straight and level flight
Why is it necessary to fit probe covers on the pitot static probe while the aircraft is on the ground?
To reduce the chance of injury to personnel and prevent insect nests
What can cause a blockage in the pitot port?
Wasp nests
What is critical for the pitot static probe?
Probe alignment
What happened to an Airbus A330 in Brisbane, Australia in 2013?
It had an airspeed indication failure during take-off
What should be consulted for specific information about pitot static system maintenance?
The aircraft's maintenance manual
What can happen if the pitot static probe is bent or twisted?
It can cause incorrect airspeed readings
Study Notes
Temperature Compensation in Airspeed Indicators
- Temperature increase affects the ranging bar, which deflects in the opposite direction to counteract capsule expansion.
- This keeps the indicating element at a constant reading.
Airspeed Indicator Markings
- Airspeed indicators have various limitation markings for pilots, specific to the aircraft model.
- A red radial line indicates the never exceed speed (Vne), limited by structural considerations of the airframe.
- The stall speed is indicated by the low-speed end of the green or white ranges, dependent on flap and landing gear configuration.
- The amber caution speed range requires smooth, turbulent-free conditions for safe operation.
Pitot Static System
- A pitot probe consists of an open-ended tube projecting into the airstream, creating pitot pressure.
- The simple tube design has disadvantages, such as moisture accumulation, which can be alleviated with a calibrated drain hole and electrical heater element.
- Static ports detect static pressure, either incorporated into other elements or as individual vents in the fuselage.
Machmeter
- A Machmeter measures airspeed and altitude, using the pressure difference between pitot and static pressure.
- The altimeter mechanism is calibrated to QNE and modifies the airspeed capsules' output.
- Altitude measurement provides equivalent temperature according to the ISA chart.
Vertical Speed Indicator (VSI)
- The VSI mechanism consists of a capsule sensing element, metering unit, and indicating element.
- During straight and level flight, the static pressure is constant, and the pointer is at the 0 feet per minute position.
- During climbs, the differential pressure causes the capsule to compress, rotating the lever link and indicating a climb condition.
Pitot Static System Maintenance
- The pitot static probe is a delicate instrument requiring care during handling and maintenance.
- Probe alignment and opening conditions are critical.
- Probe covers with trailing warning flags should be fitted during ground operations to prevent damage, injury, or wasp infestations.
Test your knowledge of the pitot static system, a crucial component of aircraft instrumentation. Learn about the pitot probe, pitot pressure, and its role in aerodynamics. This quiz is designed for pilots and aviation professionals preparing for the CASA Part 66 exam.
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