Flight Instruments Flashcards
Air pressure instruments
ASI
Altimeter
VSI
Types of pressure
Static
Pressure at any point in atmospher
No movement
Decreases with altitude
Sensed through static vent/port
Dynamic
Pressure of movement
Felt on forward facing surfaces
1/2 density v^2
Pitot
Dynamic pressure and static pressure combined
Pitot static system
Pitot port
Forward facing collects all air
Located in space with uninterrupted airflow
Static port
Static pressure
Located in area least affected by passing airflow
Ex pitot tube or pitot head
Pitot heat use
Melts ice keeps tubes clear
ASI
uses dynamic pressure
Pitot p into diaphragm (sealed aneroid capsule)
Static pressure surrounds the diaphragm
Diaphragm expands and contracts based on pressure difference between dynamic and static
Expansion calibrated to indicated airspeed
Only completely accurate at ISA conditions
Knots
Nautical miles per hour
ISA conditions
15°c
1013.25 hPa
1.225 kg/m^3 (density)
Airspeed correction order
IAS position error CAS (calibrated airspeed)
CAS compressibility error (air not an ideal fluid) EAS (equivalent airspeed)
EAS density error TAS (true airspeed)
I
C
E
T
ASI indicator markings
Vso
Stalling speed in landing configuration
Vs1
stalling speed clean
Vfe
Max flap extension speed
Vno
Max structural cruising speed normal ops
Vne
Never exceed
White
Vno to Vfe
Green
Vs1 to Vno
Yellow
Vno to Vne
Red line at Vne
ASI blocks and leaks
Pitot blockage (icing )
Under read airspeed until zero
Pitot leak
Underestimate airspeed due to decreased pitot pressure
Static blockage
Traps static
Over read descent
Under read climb
Altimeter
Static pressure
Fed into diaphragm (sealed aneroid capsule) surrounded by baseline pressure (preset)
QNH sub scale reads above sea level not agl
QNH
Height above sea level
QFE
Height above Aerodrome level
QNE
Height above ISA sea level
Vsi
Metering unit slows down change of pressure in surrounding area of aneroid capsule
Aneroid changes faster and hooked up to indicator
