u5 Flashcards
pitot-static system connects to which instruments
altimeter
airspeed indicator
vertical speed indicator
which instrument connects to both the pitot tube and static port
airspeed indicator
which instruments only connect to the static port
altimeter and vertical speed indicator
difference between ____ and _____ pressure gives airspeed indicator reading
static and dynamic
what is the purpose of the drain hole in the pitot tube
in case its raining and water gets into pitot tube it can drain out
why is pitot tube mounted away from interference (slipstream, wing pressure gradient)
and exactly where is it mounted?
so its only getting dynamic pressure of undisturbed air
below and in front of leading edge of wing (pressure gradient), and far away from fuselage (slipstream)
if you’re flying IFR, what is required for your pitot tube
heating
what is pitot tube positional error
flying at low AoA (fast) = air goes directly into pitot tube = accurate reading
flying at high AoA (slow) = not as many air molecules into pitot tube because flying at high angle = lower dynamic pressure reading than you’re acc going
how would a dent in front of the static port affect the static pressure reading? and behind?
in front: tilts static port towards oncoming air = reading higher pressure than acc
behind: tilts static port away from oncoming air = reading lower pressure than acc
im in an unpressurized plane and uh oh something has blocked my static port. what are two things i can do within the cockpit to get a static reading?
physically rip the static line so its taking in the unpressurized air of the cabin
break glass of VSI
static port is blocked so i switch to my alternate static source. it will read _____ pressure than my regular static port. how will this affect my instruments?
alternate static = lower pressure
ALT = indicate higher than acc
VSI = momentarily indicate a climb but then settle back to 0
ASI = greater than normal speed because since static is reading lower pressure than before, it’s a bigger pressure difference between pitot and static = faster speed
if static port is blocked and you have NOT pulled your alternate static air, what would your instruments look like
ASI = during a climb it’d say you’re going hella slow, whereas in a descent it’d say you’re going hella fast
ALT = stops moving
VSI = 0
if pitot tube is COMPLETELY blocked how is the ASI affected in a climb vs descent
climb = airspeed increases
descent = airspeed decreases
if the pitot tube is PARTIALLY blocked, how will the airspeed indicator be affected
ASI will eventually decrease to 0
because drain hole is open and so air in the system will slowly leak out until it reaches equilibrium with outside air pressure = air pressure difference is zero
explain how the airspeed indicator works mechanically
- ram air through pitot fills up diaphragm = expands diaphragm
- static air fills up the instrument chamber = resists diaphragm
- pressure difference gives indicated airspeed
3 types of airspeed indicator errors
- position and instrument error (position of pitot tube)
- compressibility error (when flying fast 250KT and high altitudes like jets)
- density error (termperature and altitude changes - because indicator is made for standard atmosphere at sea level)
IAS increases ___% for every _____ ft of pressure altitude increase
2%
1000 ft
how does the indicated airspeed for stall change at different altitudes
the stall IAS never changes with altitude
how different are the calibrated airspeed and indicated airspeed at slow vs fast speeds
low speed = high AoA = greater position error = CAS much higher than IAS
high speed = low AoA = less position error = CAS and IAS are pretty much the same
how different are the calibrated airspeed and indicated airspeed at slow vs fast speeds
low speed = high AoA = greater position error = CAS much higher than IAS
high speed = low AoA = less position error = CAS and IAS are pretty much the same
why does the plane stall at a higher TAS than IAS at high altitudes/high termpareatues
because the plane is going faster through less dense air to maintain flight
indicated stall speed depends on
angle of attack of wing
what is ground speed and what is a ground speed check?
- actual speed plane is travelling over the ground (TAS accounting for wind)
- timing how long it takes to flow to a known distance
as bank angle increases = stall speed _____
increases
as weight increases = stalling speed _____
why?
increases
because flying cruise at higher AoA because need more lift for more weight so reach critical AoA easier
fwd vs aft CoG loading. which one results in a higher stall speed and why
fwd CoG = faster stall speed
nose heavy plane = pilot needs to pitch up and fly at higher AoA for same airspeed compared to aft loading
how does turbulence increase the stall speed?
because a gust has the potential to increase AoA suddenly
why do hot temperatures and high elevation increase landing roll? can we slow down our plane on landing to compensate?
because TAS is higher than IAS
no because we don’t want the IAS to be so slow that it’ll reach stalling speed. just accept you have longer landing roll
why is Vx always slower than Vy
because Vx has more induced drag whereas Vy is minimized drag (best L:D)
light vs heavy plane. which one has a lower Va and why
light planes have lower Va because light planes are more forcefully pushed by a gust = easier to over stress
how does the vertical speed indicator work
- as the plane climbs, the static port fills up the diaphragm quickly
- the static port also connects to a narrow hole into the instrument casing that allows for a slow, calibrated leak
- the calibrated leak lags
- difference in air pressure tells us climb/descent
- eventually once in level flight again, the calibrated leak catches up and evens out to diaphragm = zero
two types of VSI errors:
- lag error - takes 6-8 sec for VSI to catch up and acc show a pressure difference
- reversal - sharp and sudden pitch change will cause the VSI to temporarily show the opposite of what the plane is doing
how does the altimeter work
- 29.92 inHg in diaphragm
- static port fills with outside air which affects how compressed the diaphragm is
- compare pressure difference
altimeters tell us indicated altitude. what does this mean
true altitude depends on environment
weather changes outside air pressure (hot day = less dense) so altimeters have a knob to calibrate the altimeter diaphragm to outside airport conditions
when a plane is flying from an area of high pressure to low pressure , without correcting the setting, the altimeter will read ______
too high
flying from low pressure region to high pressure region without changing the altimeter setting, the altimeter will read too _____
low
a low pressure zone will have air spinning ________. this causes a plane to drift ______
counter clockwise
right
for a given vertical depth, the pressure of cold air will change at a _________ rate than warm air
greater
why do you naturally start to descend when you fly through a valley
increased wind speed = decreased pressure in that area = generate less lift
also since we’re in a low pressure zone, your altimeter will indicate that you’re higher than you actually are
how can mountain waves be dangerous for IFR pilot who is looking at their altimeter
wind deflected over mountain = speeds up = decreased pressure = plane thinks its higher than it acc is so your altimeter will over read
also severe downdrafts can push the plane down towards the mountain
must inspect pitot-static system every ____ (time) for IFR flights
24 months
indicated, pressure, density, true and absolute altitude
indicated alt = reading on altimeter when it’s set to current pressure
pressure altitude = pressure in terms of standard atmosphere 29.92
density altitude = pressure altitude accounting for termperature (hot, high, humid = high DA)
true altitude = exact height above mean sea level
absolute altitude = actual height above the earths surface (AGL)
the magnetic compass is inside a case filled with ______. why is it filled with that?
white kerosene
to dampen the vibrations or oscillations of the compass card when we fly
magnetic dip vs magnetic variation vs magnetic deviation
magnetic dip = compass aligns with magnetic fields and near the poles, the field lines bend so the compass itself tilts itself towards the pole = not flat = unreliable reading
magnetic variation = difference between true north and magnetic north heading
deviation = compass readings slightly deviated from magnetic north because the magnetic fields of the plane/electronics itself
isogonic vs agonic line
isogonic = connect locations where the angle between magnetic north and true north is the same
agonic line = the isogonic line that connects places with ZERO degree magnetic variation
rule to convert from TRUE to MAGNETIC course: ______ is least, ____ is best
east is least, west is best
halifax and victoria. which has east and which has west variation
halifax (east) has a WEST variation
victoria (west) has a EAST variation
what is the northerly turning error and what’s the acronym
- during a turn, friction causes inaccurate compass readings
UNOS (northern hemisphere)
undershoot north, overshoot south
turning north, compass initially shows turn in opposite direction (lags)
turning south, compass overshoots before returning to your heading
what is the acceleration/deceleration error and what is the acronym
accelation on an east/west heading will move the compass card incorrectly
ANDS
accelerate north, decelerate south
why can’t you put your ipad on the dashboard
because those electromagnetic fields can mess with your compass magnet and cause it to point in wrong direction
gyroscope has two characteristics and explain
- rigidity in space - once disc spinning, it’s rigid in space and everything else (plane) moves around it
- precession - deflection of a spinning wheel 90º to the plane of rotation
which instruments in plane have a gyroscope
attitude indicator, heading indicator and turn coordinator
attitude indicator on _____ system and turn coordinator on ______ system because….
AI = vacuum
TC = electrical
if one system fails, the other is backup
engine driven vs venturi driven vacuum system
engine driven: engine starts up = immediately powers gyroscope on ground unmoving
venturi driven: gyroscope can only spin when plane is moving so air can go through venturi. so if ice blocks venturi - no airflow to gyroscope = gyroscope stops spinning = vacuum driven instruments fail
the heading indicator has a gyro that spins ________
vertically
what instrument is prone to apparent precession. also wtf is apparent precession
heading indicator
- initially planes HI set to face magnetic north at location 1
- plane crosses multiple isogonic lines
- direction of magnetic north changes but heading indicator can detect that change automatically so need to change HI to correct it
travelling east to west vs west to east. which direction will your HI experience most apparent precession
east to west = drastic heading difference because crossing more isogonic lines
(earth is rotating under plane as well)
why is a heading indicator better than compass
- HI steady in turbulence
- none of the compass errors (UNOS ANDS)
- reliable as long as pilot readjusts for the apparent precession and frictional precession
pilot must set HI to match compass every _____ (time)
15 mins
im banked 55º and my heading indicator is tumbling. can i use it again once in steady flight?
not until its reset by the adjustment knob
the attitude indicator has a gyro that spins _______
horizontally
two basic properties of gyroscope
- rigidity in space
- precession (90º force)
gyros have the LEAST amount of precession when…
(spinning speed, weight, size)
gyro is spinning fast, heavy weight, large radius
Attitude indicator gyro error:
- acceleration indicates a ______
- deceleration indicates a _____
climb
descent
what is a standard rate turn? plane moves _____º of heading change every ______. so it takes ____ mins to turn 360º
3º/sec
2
skid vs slip in terms of bank
skid = not enough bank = ball rolls towards outside of inclometer
slip = too much bank = ball rolls inside of the inclometer
the turn and bank indicator has a gyro that spins ______
vertically
why can a turn and bank indicator only sense YAW motion, and not roll ?
because of it’s mounting.
when precession tries to happen (90º force), it hits the mounting, so it doesn’t move the gyro
resultant force blocked
why can the turn coordinator respond to yaw and roll?
because gyro is mounted 30-35º angle from horizontal
a plane flying at a faster speed needs a _____ bank angle to have the same rate of turn as a slower plane
greater
for standard rate turn, bank angle equation is…
bank angle = (KTAS/10) + 7
which instruments tell us pitch and which ones tell us bank and which ones tell us power?
pitch = AI, altimeter, VSI
bank = AI, TC, heading indicator
power = tach, ASI
instrument flying rn and i’m nose up, approaching a stall? what’s my recovery and which instruments do i use/not use
ASI and TC
(assume vacuum AI and HI have toppled and ALT and VSI are lagging)
as ASI decreasing, approaching a stall
- full power
- nose down until ASI stops decreasing
- level wings with TC
- reduce power to cruise
- cross check instruments
instrument flying rn and i’m nose down spiral. what instruments do i use/recovery
use ASI and TC
look at ASI trend, is it increasing
- power off
- level wings with TC
- nose up until ASI stops increasing
- return to cruise power
- cross check instruments
