Aircraft instruments
- 2. Pitot – Static SystemPitot – Static System
- 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?
- 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
- 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
- 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?
- 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.
Editor's Notes
- #8: Ram air pushes against a diaphragm inside the airspeed indicator, te airtight case is vented to the static ports. A mechanical linkage translates the expansion and contraction of the diaphragm into needle movement.
- #18: Measures how fast the static pressure increases or decreases as the airplane climbs or descends. It then displays this pressure change as a rate of climb or descent in feet per minute. Not affected by air temperature since it measures only changes in air pressure