Pressure Instruments Flashcards
1
Q
Pressure instruments
A
also known as Pitot-Static Instruments
use air pressure differential to provide indication
2
Q
International Standard Atmosphere
A
Air is a perfectly dry gas
- Temperature at sea level is 15 °C
- Standard temperature lapse rate is 1.98 °C or 2°C per 1,000 feet increase in altitude
- Mean sea level pressure is 29.92 in, or 1013.2 hPa
- Standard pressure lapse rate is 1 inHg per 1,000 feet.
3
Q
ISA notes to pilots
A
- Certain instruments are calibrated to ISA conditions
- If non-ISA conditions exist, they need to be calibrated by the pilot
4
Q
Static Pressure
A
- Ambient air pressure
- Exerted by the surrounding
air, equally in all directions
5
Q
Static Port
A
Located in an area on the fuselage which is free of aerodynamic disturbances
6
Q
Dynamic Pressure
A
Pressure exerted by air resisting motion through the air
- Impact/Ram air pressure
- Pressure due to motion
- ½ρv2
7
Q
Total Pressure
A
Dynamic pressure + Static Pressure
Also known as pitot pressure
8
Q
Pitot-Tube
A
Elongated tube with a hole oriented to relative wind
Collects air molecules which translates in to amount of dynamic pressure
9
Q
Pitot-Static System
A
- combination of the pitot tube and static port
- Allows us to measure airspeed, altitude, and vertical speed
10
Q
Pitot-static system problems
A
- Partially Blocked Pitot Tube
- Partially Blocked Static Port
- Blocked Pitot Tube Intake and Drain Hole
- Blocked Pitot Tube Intake
- Blocked Static Port
11
Q
Causes of Pitot-static system problems
A
- In-Flight Icing
- Insects
- Volcanic Ash
- Heavy rain
- Crude Oil Smoke
- Failure to remove maintenance seals or protective covers from external vents prior to flight
- Failure to select pitot static heat on
- Damage to the radome/nose cone of an aircraft causing erroneous pitot and static information.
12
Q
Avoiding pitot-static problems
A
- Keep the pitot tube cover on until just before startup.
- Check the pitot tube
- Check the static port
- Check the ASI on takeoff roll and announce “airspeed alive”
- Use pitot heat when operating in visible moisture
- Avoid flight in icing conditions
- Always check the weather
13
Q
Surviving pitot-static problems
A
- Engage pitot and/or static port heating systems
- Use alternate static air sources (if applicable)
- Break the VSI to let static pressure from inside the aircraft into the system.
- If airspeed indicator is inaccurate, or inoperative, maintain a known pitch and power setting that will give a safe airspeed.
