Barometric Instruments Flashcards
What are the two most important reasons why the principles of operation and the interpretation and reading of instruments used on modern aircraft needs to be thoroughly understood by the technician?
- Safety
- The instruments can provide the technician with indications of powerplant or system conditions. This data can be used for troubleshooting.
What are the two basic types of mechanical pressure measuring instruments?
Bourdon Tubes & Diaphragm/Bellows
What does the Bourdon tube measure?
Typically used for high pressure readings such as oil pressure and hydraulics.
Can be used to measure low pressures.
What are Bellows or Diaphragms used for?
Used to read comparatively low pressure readings.
What is a sealed aneroid called?
Diaphragm
What is it called when diaphragms (aneroid cells) are stacked?
Bellows
What 3 aircraft instruments are built with bellows and diaphragms and “powered” by air pressures.
Altimeter
Airspeed Indicator
Vertical Speed Indicator
What is the source of “power” for the Altimeter, A/S indicator and VSI instruments?
Pitot-static system
What does the pitot system provide?
Ram air
What does the pitot system consist of?
One or more pitot tubes and various connections and tubing
What is the only instrument that uses ram or pitot air pressure?
Airspeed Indicator
When may a pitot tube be heated?
If the A/C is certified for IFR flight
When is an aircraft not required to have a heated pitot tube?
If the aircraft is certified for VFR flight only
How do you test the heating element on a pitot tube?
Turn on the aircraft, turn on the pitot head, and look for the draw on the ammeter
What does the static system provide?
The static system provides low pressure air to the altimeter and Vertical Speed
Indicator (VSI)
Where are the Static Ports typically located?
Typically located on the side of the A/C fuselage.
May also be located in the pitot head
What is built into the pitot system and static system to prevent water reaching the instruments and causing damage?
moisture drains
What will moisture do to the pitot and static systems?
Cause corrosion and may also freeze at altitude - rupturing lines or or damaging instruments
What type of static drains may be on larger aircrafts?
Petcock type drain valves
The pitot system and static system are completely independent systems but….
both systems are needed to provide readings for the instruments
When inspecting or working on or around pitot or static systems…
care must be taken not to damage the openings to these ports
What must you always use when connecting, disconnecting, or torquing rigid tube fittins?
Two wrenches
What should you never do to pitot static ports?
Never spray water directly into them
What type of damage can cause readings to be incorrect?
Static erosion