This document provides information about various aircraft instruments including: - The airspeed indicator which uses ram air from the pitot tube and static air, and displays airspeeds like Vso and Vfe. Blockages of the pitot tube or static vent can cause errors. - The altimeter which uses only static air input and displays various altitudes like indicated, pressure, and density altitude. Not updating the altimeter setting can cause errors. - Gyroscopic instruments like the attitude indicator and heading indicator which function based on the principles of rigidity in space and precession. - The turn coordinator and inclinometer which indicate aircraft bank and slip/skid. - The magnetic compass

1. Aircraft InstrumentsAircraft Instruments

2. Pitot – Static SystemPitot – Static System

3. Airspeed IndicatorAirspeed Indicator

4. Airspeed Indicator SymbologyAirspeed Indicator Symbology
► White Arc – FlapWhite Arc – Flap
operating Rangeoperating Range
► Green Arc – NormalGreen Arc – Normal
OperationsOperations
► Yellow Arc –Yellow Arc –
Caution Area (OnlyCaution Area (Only
use in smooth air)use in smooth air)
► Red Line – NeverRed Line – Never
Exceed SpeedExceed Speed

5. Aircraft AirspeedsAircraft Airspeeds
► Vso – Stall speed in landing configurationVso – Stall speed in landing configuration
► Vs – Stall speed in clean (flaps up) configurationVs – Stall speed in clean (flaps up) configuration
► Vy – Climb speed for the max amount of height v.Vy – Climb speed for the max amount of height v.
timetime
► Vx- Climb speed for the max amount of height forVx- Climb speed for the max amount of height for
distancedistance
► Vfe- Flap Extension speed: Flaps should not beVfe- Flap Extension speed: Flaps should not be
used above this speedused above this speed
► Va – Design maneuvering/rough air speed:Va – Design maneuvering/rough air speed:
Speed at which abrupt full control inputs can beSpeed at which abrupt full control inputs can be
used without risking structural damage. Shouldused without risking structural damage. Should
never be exceeded in rough air. Changes withnever be exceeded in rough air. Changes with
weightweight
► Vno – Max structural Cruise speedVno – Max structural Cruise speed

6. Types of AirspeedsTypes of Airspeeds
► Calibrated
 Speed corrected for installation and instrument errors.
 At high angle of attack, the pitot tube does not point straight into the
relative wind, this tends to make the airspeed indicate lower than
normal at low airspeeds.
 Not usually a problem in cruise, usually we only worry about calibrate
airspeed when we are converting to true airspeed.
► True
 The actual speed of your airplane is moving through undisturbed air.
 On a standard day, Calibrated airspeed will be equal to TAS.
 As density altitude increases, true airspeed increases for a given CAS
or amount of power.
 TAS can be calculated by using CAS with temperature and pressure on
your E6B
► Equivalent
 Calibrated airspeed corrected for adiabatic compressible flow at a
particular altitude.
 Above 200 kts and 20,000 feet air compresses in front the pitot tube
causing abnormally high airspeeds. Many flight computers are designed
to compensate.

7. Airspeed IndicatorAirspeed Indicator
► Uses ram air from the pitot tube as well as static air.Uses ram air from the pitot tube as well as static air.
► Ram air pushes against a diaphragm inside the airspeedRam air pushes against a diaphragm inside the airspeed
indicator, which will then be able to expand or contractindicator, which will then be able to expand or contract
accordingly. This movement of the diaphragm is thenaccordingly. This movement of the diaphragm is then
translated into needle movement.translated into needle movement.

8. Airspeed IndicatorAirspeed Indicator
► If the Pitot tube is blocked and the drain is open, speed will go toIf the Pitot tube is blocked and the drain is open, speed will go to
zero.zero.
► If the Pitot tube is blocked and the drain is open, it will act as anIf the Pitot tube is blocked and the drain is open, it will act as an
altimeter.altimeter.
► If the the Static vent is blocked, the airspeed will read higher than itIf the the Static vent is blocked, the airspeed will read higher than it
should above altitude where it became blocked and lower than itshould above altitude where it became blocked and lower than it
should below.should below.
► If all three all blocked, the needle will freeze.If all three all blocked, the needle will freeze.

9. Questions?Questions?
►How does the airspeed indicator computeHow does the airspeed indicator compute
indicated airspeed?indicated airspeed?
►How will we know if we have a blocked pitotHow will we know if we have a blocked pitot
tube?tube?
 What would you do?What would you do?
►Will you need to compute your equivalentWill you need to compute your equivalent
airspeed for flight?airspeed for flight?

10. AltimeterAltimeter

11. AltimeterAltimeter
► Static Input OnlyStatic Input Only
► Manufacturer seals theManufacturer seals the
aneroid wafer(s) at aaneroid wafer(s) at a
specific pressure. Asspecific pressure. As
the static pressure fillsthe static pressure fills
in the area aroundin the area around
these sealed wafers,these sealed wafers,
they will be able tothey will be able to
contract or expandcontract or expand
accordinglyaccordingly

12. Altimeter OperationAltimeter Operation

13. Types of AltitudeTypes of Altitude
► IndicatedIndicated
 What you read on the altimeter when it is correctly adjusted toWhat you read on the altimeter when it is correctly adjusted to
show approximate height above mean sea levelshow approximate height above mean sea level
► CalibratedCalibrated
 Indicated altitude corrected to compensate for instrument errorIndicated altitude corrected to compensate for instrument error
► PressurePressure
 Displayed when altimeter is set to standard sea level (29.92).Displayed when altimeter is set to standard sea level (29.92).
 Vertical distance above the standard datum planeVertical distance above the standard datum plane
► DensityDensity
 Pressure altitude corrected for non – standard temperaturePressure altitude corrected for non – standard temperature
 Used to determine aircraft performance, when high (tempUsed to determine aircraft performance, when high (temp
above standard), performance will be worse.above standard), performance will be worse.
► TrueTrue
 Actual height above mean sea levelActual height above mean sea level
 Sectional chartsSectional charts
► AbsoluteAbsolute
 Actual height of aircraft above the earths surface.Actual height of aircraft above the earths surface.

14. Altimeter ErrorsAltimeter Errors
► Make sure you update your altimeter setting asMake sure you update your altimeter setting as
often as possible (or at least every 100 miles)often as possible (or at least every 100 miles)
► If you fly to an area with a lower altimeter setting,If you fly to an area with a lower altimeter setting,
without resetting your altimeter, you may fly at awithout resetting your altimeter, you may fly at a
lower altitude than you had intended.lower altitude than you had intended.
► ““High to low, look out below”High to low, look out below”
► On warm days, true altitude is higher thanOn warm days, true altitude is higher than
indicated. Aircraft true altitude is lower thanindicated. Aircraft true altitude is lower than
indicated in colder air.indicated in colder air.
► Static BlockageStatic Blockage
 Altimeter will freeze at the altitude the blockage occuredAltimeter will freeze at the altitude the blockage occured

15. High to Low, Look out Below!High to Low, Look out Below!

16. Questions?Questions?
► How does the altimeter work?How does the altimeter work?
► What altitude is displayed on a sectional chart?What altitude is displayed on a sectional chart?
► If I fly from an area of a pressure setting of 29.92If I fly from an area of a pressure setting of 29.92
to an area where it was 30.00, would I be likely toto an area where it was 30.00, would I be likely to
be flying above or below where I should?be flying above or below where I should?
► How would you know if the static port wasHow would you know if the static port was
blocked?blocked?
 If you then turned on alternate air, what kind ofIf you then turned on alternate air, what kind of
indication would you generally expect?indication would you generally expect?

17. Vertical Speed IndicatorVertical Speed Indicator
► Rate of climb and descentRate of climb and descent
► Trend will show immediate indication of anTrend will show immediate indication of an
increase in the airplanes rate of climb or descentincrease in the airplanes rate of climb or descent
► Rate shows a stabilized change in altitudeRate shows a stabilized change in altitude

18. Vertical Speed IndicatorVertical Speed Indicator
► Static air enters both theStatic air enters both the
diaphragm and the areadiaphragm and the area
around it. However, the airaround it. However, the air
in the diaphragm isin the diaphragm is
constantly updated whileconstantly updated while
the air outside of it is verythe air outside of it is very
slowly allowed to escapeslowly allowed to escape
through a calibrated leak.through a calibrated leak.
The instrument measuresThe instrument measures
the difference in these twothe difference in these two
pressures (the air wherepressures (the air where
you where v. where youyou where v. where you
are)are)

19. Vertical Speed Indicator ErrorsVertical Speed Indicator Errors
►Blocked StaticBlocked Static
 Zero IndicationZero Indication
►Lags: should not be relied upon to giveLags: should not be relied upon to give
instantaneous informationinstantaneous information
 Don’t “chase the needle”Don’t “chase the needle”

20. Pitot – Static SummaryPitot – Static Summary
► While the Altimeter, VSI and airspeed indicator allWhile the Altimeter, VSI and airspeed indicator all
use Static air, only the airspeed indicator usesuse Static air, only the airspeed indicator uses
PitotPitot
► If you notice all of your pitot static instruments areIf you notice all of your pitot static instruments are
giving conflicting information, try turning using thegiving conflicting information, try turning using the
alternate air sourcealternate air source
► If only your airspeed indicator is not workingIf only your airspeed indicator is not working
properly, try turning on pitot heatproperly, try turning on pitot heat

21. Gyro InstrumentsGyro Instruments

22. Which instruments areWhich instruments are
Gyroscopic?Gyroscopic?
► Which instrument(s) are powered by the vacuumWhich instrument(s) are powered by the vacuum
system?system?
► Which are powered by the electrical system?Which are powered by the electrical system?
 Why?Why?

23. Gyroscopic PrinciplesGyroscopic Principles
► Rigidity in SpaceRigidity in Space
 A wheel with a heavilyA wheel with a heavily
weighted rim spun rapidlyweighted rim spun rapidly
tends to remain fixed in thetends to remain fixed in the
plane in which it is spinningplane in which it is spinning
 The wheel is mounted on aThe wheel is mounted on a
set of gimbals so that theset of gimbals so that the
gyro is able to rotate freely ingyro is able to rotate freely in
any planeany plane
 As the gimbals’ base tiltsAs the gimbals’ base tilts
and twists, the gyro remainsand twists, the gyro remains
spinning in its original planespinning in its original plane
 Allows a gyroscope toAllows a gyroscope to
measure changes in themeasure changes in the
attitude or direction of anattitude or direction of an
airplaneairplane

24. PrecessionPrecession
► What is precession?What is precession?
 When an outside force triesWhen an outside force tries
to tilt a spinning gryo, theto tilt a spinning gryo, the
gyro responds as if the forcegyro responds as if the force
had been applied at a pointhad been applied at a point
90 degrees in the direction90 degrees in the direction
of rotationof rotation
► Precession side – effects?Precession side – effects?
 Friction in gimbals andFriction in gimbals and
bearings may cause a slowbearings may cause a slow
drifting in the headingdrifting in the heading
indicator and occasionalindicator and occasional
small errors in the attitudesmall errors in the attitude
indicatorindicator

25. Questions?Questions?
►Why is the turn coordinator powered by theWhy is the turn coordinator powered by the
electrical system?electrical system?
►A spinning wheel tends to stay in its originalA spinning wheel tends to stay in its original
plane when disrupted, this refers to whatplane when disrupted, this refers to what
concept?concept?
►Our heading indicator has becomeOur heading indicator has become
inaccurate by 5 degrees since takeoff, whatinaccurate by 5 degrees since takeoff, what
is causing this?is causing this?

26. Vacuum InstrumentsVacuum Instruments

27. Attitude IndicatorAttitude Indicator
► Only instrument that givesOnly instrument that gives
immediate and directimmediate and direct
indication of the airplane’sindication of the airplane’s
pitch and bank attitude.pitch and bank attitude.
► OperationOperation
 Gyro spins in the horizontalGyro spins in the horizontal
plane, mounted on dualplane, mounted on dual
gimbals that allow it togimbals that allow it to
remain in the planeremain in the plane
regardless of aircraftregardless of aircraft
movement.movement.
 Pendulous vanes allow thePendulous vanes allow the
attitude indicator erect itselfattitude indicator erect itself
on taxion taxi

28. Attitude Indicator ErrorsAttitude Indicator Errors
► Usually less than 5 degrees of bank error and 1 bar width of pitchUsually less than 5 degrees of bank error and 1 bar width of pitch
error in a 180 degree turn.error in a 180 degree turn.
► Pendulous vanes act on the attitude indicators gyro in an undesirablePendulous vanes act on the attitude indicators gyro in an undesirable
way during turns.way during turns.
► The same pendulous vanes will cause the gyro to try to line up with theThe same pendulous vanes will cause the gyro to try to line up with the
g – forces of a turn.g – forces of a turn.
► Acceleration and Deceleration can induce precession errors. DuringAcceleration and Deceleration can induce precession errors. During
acceleration, horizon bar may show a climb, reinforcing theacceleration, horizon bar may show a climb, reinforcing the
somatogravic illusion.somatogravic illusion.
► Tumbling: Past 100 degrees of bank or 60 degrees of pithTumbling: Past 100 degrees of bank or 60 degrees of pith

29. Heading IndicatorHeading Indicator
► What does it do?What does it do?
 Senses rotation aboutSenses rotation about
the aircraft’s verticalthe aircraft’s vertical
axis.axis.
► Errors?Errors?
 Precession can causePrecession can cause
heading to drift, soheading to drift, so
remember to re – checkremember to re – check
about every 15 min.about every 15 min.

30. Turn IndicatorsTurn Indicators
► Turn Coordinator:Turn Coordinator:
 Rate and RollRate and Roll
► Slip and SkidSlip and Skid
 Rate ONLY – older aircraftRate ONLY – older aircraft
► What is the inclinometer?What is the inclinometer?
 Slip? Rate of turn is too slowSlip? Rate of turn is too slow
for the angle of bank, ballfor the angle of bank, ball
moves insidemoves inside
 Skid? Rate of turn is tooSkid? Rate of turn is too
great for the angle of bank.great for the angle of bank.
► Standard Turn?Standard Turn?

31. Gyro Instruments SummaryGyro Instruments Summary
►The gyroscopic instruments incorporate twoThe gyroscopic instruments incorporate two
concepts, Rigidity in Space and precessionconcepts, Rigidity in Space and precession
►The turn coordinator is powered by theThe turn coordinator is powered by the
electrical system rather than the vacuumelectrical system rather than the vacuum
system so that in case of a failure, the pilotsystem so that in case of a failure, the pilot
will always have a way to reference flightwill always have a way to reference flight
attitude.attitude.

32. CompassCompass
► Bar Magnet alignsBar Magnet aligns
itself with the magneticitself with the magnetic
fieldfield

33. Compass ErrorsCompass Errors
►Variation: Difference between the true andVariation: Difference between the true and
magnetic poles. Use correction indicated onmagnetic poles. Use correction indicated on
sectionalsectional

34. Compass ErrorsCompass Errors
►Deviation: Compass error due toDeviation: Compass error due to
disturbances in magnetic field de to metalsdisturbances in magnetic field de to metals
and electrical accessories in the airplane.and electrical accessories in the airplane.
Use deviation card in airplane to correct.Use deviation card in airplane to correct.

35. Compass ErrorsCompass Errors
►Magnetic Dip: Bar magnet contained inMagnetic Dip: Bar magnet contained in
compass is pulled by the earth’s magneticcompass is pulled by the earth’s magnetic
field, it tends to point north and somewhatfield, it tends to point north and somewhat
downward. Greatest near the polesdownward. Greatest near the poles

36. Compass ErrorsCompass Errors
►Acceleration Error: Occurs whenAcceleration Error: Occurs when
accelerating or decelerating on an easterlyaccelerating or decelerating on an easterly
or westerly heading. As you accelerate,or westerly heading. As you accelerate,
inertia causes the compass weight on theinertia causes the compass weight on the
south end of magnetic to lag and turn thesouth end of magnetic to lag and turn the
compass toward north. As you decelerate,compass toward north. As you decelerate,
inertia causes weight to move ahead,inertia causes weight to move ahead,
moves the compass toward a southerlymoves the compass toward a southerly
heading.heading.

37. Compass ErrorsCompass Errors
►Turning Error: Most pronounced whenTurning Error: Most pronounced when
turning to or from headings of north orturning to or from headings of north or
south.south.
►When you begin a turn from a heading ofWhen you begin a turn from a heading of
north, the compass initially indicates a turnnorth, the compass initially indicates a turn
to the opposite direction. When the turn isto the opposite direction. When the turn is
established, the compass begins to turn inestablished, the compass begins to turn in
the correct direction, but it lags behind thethe correct direction, but it lags behind the
actual heading.actual heading.

38. Questions?Questions?