Aircraft InstrumentsAircraft Instruments

Pitot – Static SystemPitot – Static System

Airspeed IndicatorAirspeed Indicator

Airspeed Indicator SymbologyAirspeed Indicator Symbology

► White Arc – Flap White Arc – Flap operating Rangeoperating Range

► Green Arc – Normal Green Arc – Normal OperationsOperations

► Yellow Arc – Yellow Arc – Caution Area (Only Caution Area (Only use in smooth air)use in smooth air)

► Red Line – Never Red Line – Never Exceed SpeedExceed Speed

Aircraft AirspeedsAircraft Airspeeds► Vso – Stall speed in landing configurationVso – Stall speed in landing configuration► Vs – Stall speed in clean (f laps up) configurationVs – Stall speed in clean (f laps up) configuration► Vy – Climb speed for the max amount of height v. Vy – Climb speed for the max amount of height v.

t imetime► Vx- Climb speed for the max amount of height for Vx- Climb speed for the max amount of height for

distancedistance► Vfe- Flap Extension speed: Flaps should not be Vfe- 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 ful l control inputs can be Speed at which abrupt ful l control inputs can be used without r isking structural damage. Should used without r isking structural damage. Should never be exceeded in rough air. Changes with never be exceeded in rough air. Changes with weightweight

► Vno – Max structural Cruise speedVno – Max structural Cruise speed► Vne – Never Exceed SpeedVne – Never Exceed Speed

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 wil l be equal to TAS. As density alt i tude 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 alti tude. Above 200 kts and 20,000 feet air compresses in front the pitot tube

causing abnormally high airspeeds. Many f l ight computers are designed to compensate.

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 airspeed Ram air pushes against a diaphragm inside the airspeed

indicator, which will then be able to expand or contract indicator, which will then be able to expand or contract accordingly. This movement of the diaphragm is then accordingly. This movement of the diaphragm is then translated into needle movement.translated into needle movement.

Airspeed IndicatorAirspeed Indicator

► If the Pitot tube is blocked and the drain is open, speed will go to If 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 an If 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 it If the the Static vent is blocked, the airspeed will read higher than it should above altitude where it became blocked and lower than it should 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.

Questions?Questions?

►How does the airspeed indicator compute How does the airspeed indicator compute indicated airspeed?indicated airspeed?

►How will we know if we have a blocked pitot How 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 equivalent Will you need to compute your equivalent airspeed for flight?airspeed for flight?

AltimeterAltimeter

AltimeterAltimeter

► Static Input OnlyStatic Input Only► Manufacturer seals the Manufacturer seals the

aneroid wafer(s) at a aneroid wafer(s) at a specific pressure. As specific pressure. As the static pressure fills the static pressure fills in the area around in the area around these sealed wafers, these sealed wafers, they will be able to they will be able to contract or expand contract or expand accordinglyaccordingly

Altimeter OperationAltimeter Operation

Types of AltitudeTypes of Altitude► IndicatedIndicated

What you read on the alt imeter when it is correct ly adjusted to What you read on the alt imeter when it is correct ly adjusted to show approximate height above mean sea levelshow approximate height above mean sea level

► CalibratedCalibrated Indicated alt i tude corrected to compensate for instrument errorIndicated alt i tude corrected to compensate for instrument error

► Pressure Pressure Displayed when alt imeter is set to standard sea level (29.92). Displayed when alt imeter is set to standard sea level (29.92). Vert ical distance above the standard datum planeVert ical distance above the standard datum plane

► DensityDensity Pressure alt i tude corrected for non – standard temperaturePressure alt i tude corrected for non – standard temperature Used to determine aircraft performance, when high (temp Used to determine aircraft performance, when high (temp

above standard), performance wil l be worse.above standard), performance wil l be worse.► True True

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.

Altimeter ErrorsAltimeter Errors► Make sure you update your altimeter setting as Make 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 a without 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 than On warm days, true altitude is higher than

indicated. Aircraft true altitude is lower than indicated. 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

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

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 29.92 If I fly from an area of a pressure setting of 29.92

to an area where it was 30.00, would I be likely to to 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 was How would you know if the static port was blocked?blocked? If you then turned on alternate air, what kind of If you then turned on alternate air, what kind of

indication would you generally expect?indication would you generally expect?

Vertical Speed IndicatorVertical Speed Indicator

► Rate of climb and descentRate of climb and descent► Trend will show immediate indication of an Trend 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

Vertical Speed IndicatorVertical Speed Indicator► Static air enters both the Static air enters both the

diaphragm and the area diaphragm and the area around it. However, the air around it. However, the air in the diaphragm is in the diaphragm is constantly updated while constantly updated while the air outside of it is very the air outside of it is very slowly allowed to escape slowly allowed to escape through a calibrated leak. through a calibrated leak. The instrument measures The instrument measures the difference in these two the difference in these two pressures (the air where pressures (the air where you where v. where you you where v. where you are)are)

Vertical Speed Indicator ErrorsVertical Speed Indicator Errors

►Blocked Static Blocked Static Zero IndicationZero Indication

►Lags: should not be relied upon to give Lags: should not be relied upon to give instantaneous informationinstantaneous information Don’t “chase the needle”Don’t “chase the needle”

Pitot – Static SummaryPitot – Static Summary

► While the Altimeter, VSI and airspeed indicator all While the Altimeter, VSI and airspeed indicator all use Static air, only the airspeed indicator uses use Static air, only the airspeed indicator uses PitotPitot

► If you notice all of your pitot static instruments are If you notice all of your pitot static instruments are giving conflicting information, try turning using the giving conflicting information, try turning using the alternate air sourcealternate air source

► If only your airspeed indicator is not working If only your airspeed indicator is not working properly, try turning on pitot heatproperly, try turning on pitot heat

Gyro InstrumentsGyro Instruments

Which instruments are Which instruments are Gyroscopic?Gyroscopic?

► Which instrument(s) are powered by the vacuum Which 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?

Gyroscopic PrinciplesGyroscopic Principles

► Rigidity in SpaceRigidity in Space A wheel with a heavily A wheel with a heavily

weighted rim spun rapidly weighted rim spun rapidly tends to remain fixed in the tends to remain fixed in the plane in which it is spinningplane in which it is spinning

The wheel is mounted on a The wheel is mounted on a set of gimbals so that the set of gimbals so that the gyro is able to rotate freely in gyro is able to rotate freely in any planeany plane

As the gimbals’ base tilts As the gimbals’ base tilts and twists, the gyro remains and twists, the gyro remains spinning in its original planespinning in its original plane

Allows a gyroscope to Allows a gyroscope to measure changes in the measure changes in the attitude or direction of an attitude or direction of an airplaneairplane

PrecessionPrecession► What is precession?What is precession?

When an outside force tries When an outside force tries to tilt a spinning gryo, the to tilt a spinning gryo, the gyro responds as if the force gyro responds as if the force had been applied at a point had been applied at a point 90 degrees in the direction 90 degrees in the direction of rotationof rotation

► Precession side – effects?Precession side – effects? Friction in gimbals and Friction in gimbals and

bearings may cause a slow bearings may cause a slow drifting in the heading drifting in the heading indicator and occasional indicator and occasional small errors in the attitude small errors in the attitude indicatorindicator

Questions?Questions?►Why is the turn coordinator powered by the Why is the turn coordinator powered by the

electrical system?electrical system?►A spinning wheel tends to stay in its original A spinning wheel tends to stay in its original

plane when disrupted, this refers to what plane when disrupted, this refers to what concept?concept?

►Our heading indicator has become Our heading indicator has become inaccurate by 5 degrees since takeoff, what inaccurate by 5 degrees since takeoff, what is causing this?is causing this?

Vacuum InstrumentsVacuum Instruments

Attitude IndicatorAttitude Indicator► Only instrument that gives Only instrument that gives

immediate and direct immediate and direct indication of the airplane’s indication of the airplane’s pitch and bank attitude.pitch and bank attitude.

► OperationOperation Gyro spins in the horizontal Gyro spins in the horizontal

plane, mounted on dual plane, mounted on dual gimbals that allow it to gimbals that allow it to remain in the plane remain in the plane regardless of aircraft regardless of aircraft movement.movement.

Pendulous vanes allow the Pendulous vanes allow the attitude indicator erect itself attitude indicator erect itself on taxion taxi

Attitude Indicator ErrorsAttitude Indicator Errors► Usually less than 5 degrees of bank error and 1 bar width of pitch Usually 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 undesirable Pendulous 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 the The 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. During Acceleration and Deceleration can induce precession errors. During acceleration, horizon bar may show a climb, reinforcing the acceleration, 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

Heading IndicatorHeading Indicator

► What does it do?What does it do? Senses rotation about Senses rotation about

the aircraft’s vertical the aircraft’s vertical axis.axis.

► Errors?Errors? Precession can cause Precession can cause

heading to drift, so heading to drift, so remember to re – check remember to re – check about every 15 min.about every 15 min.

Turn IndicatorsTurn Indicators► Turn Coordinator:Turn Coordinator:

Rate and RollRate and Roll► Slip and Skid Slip and Skid

Rate ONLY – older aircraftRate ONLY – older aircraft► What is the inclinometer?What is the inclinometer?

Slip? Rate of turn is too slow Slip? Rate of turn is too slow for the angle of bank, ball for the angle of bank, ball moves insidemoves inside

Skid? Rate of turn is too Skid? Rate of turn is too great for the angle of bank.great for the angle of bank.

► Standard Turn?Standard Turn?

Gyro Instruments SummaryGyro Instruments Summary

►The gyroscopic instruments incorporate two The gyroscopic instruments incorporate two concepts, Rigidity in Space and precessionconcepts, Rigidity in Space and precession

►The turn coordinator is powered by the The turn coordinator is powered by the electrical system rather than the vacuum electrical system rather than the vacuum system so that in case of a failure, the pilot system so that in case of a failure, the pilot will always have a way to reference flight will always have a way to reference flight attitude.attitude.

CompassCompass

► Bar Magnet aligns Bar Magnet aligns itself with the magnetic itself with the magnetic fieldfield

Compass ErrorsCompass Errors

►Variation: Difference between the true and Variation: Difference between the true and magnetic poles. Use correction indicated on magnetic poles. Use correction indicated on sectionalsectional

Compass ErrorsCompass Errors

►Deviation: Compass error due to Deviation: Compass error due to disturbances in magnetic field de to metals disturbances 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.

Compass ErrorsCompass Errors

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

Compass ErrorsCompass Errors

►Acceleration Error: Occurs when Acceleration Error: Occurs when accelerating or decelerating on an easterly accelerating or decelerating on an easterly or westerly heading. As you accelerate, or westerly heading. As you accelerate, inertia causes the compass weight on the inertia causes the compass weight on the south end of magnetic to lag and turn the south 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 southerly moves the compass toward a southerly heading.heading.

Compass ErrorsCompass Errors►Turning Error: Most pronounced when Turning Error: Most pronounced when

turning to or from headings of north or turning to or from headings of north or south. south.

►When you begin a turn from a heading of When you begin a turn from a heading of north, the compass initially indicates a turn north, the compass initially indicates a turn to the opposite direction. When the turn is to the opposite direction. When the turn is established, the compass begins to turn in established, the compass begins to turn in the correct direction, but it lags behind the the correct direction, but it lags behind the actual heading.actual heading.

Questions?Questions?