1.Instrumentation9 February 2005

2. Instrumentation Pitot-static system Altimiter Vertical Speed Indicator Airspeed Indicator Gyroscopic Instruments Turn coordinator Artificial horizon Heading indicator Magnetic Compass OAT Gauge 3. Pitot-static system Operates in response to air pressure Two air pressures: Static pressure Taken from static vents, powers all three pitot- static system instruments (ASI, VSI, Altimeter) Impact pressure Powers airspeed indicator only 4. Static System & Altimetry Static system powers altimeter Altimeter operates as a barometer Set altimeter on the ground to local settings Air pressure decreases at a constant rate perfoot increased in lower atmosphere(approximately 1000 per 1 Hg) Nonstandard temperature and pressure affectaltimeter 5. Altimeter As static pressure decreases, indicated altitude increases Altimeter setting is adjustable in KohlsmanWindow, aka Altimeter Setting Window Local altimeter setting willcause the instrument to readthe approximate fieldelevation when located onthe ground at the airport Reset altimeter to 29.92when climbing through18,000 feet. 6. Altitude Terminology Indicated Altitude Altitude read on the altimeter when it is set to the current local altimeter setting Absolute altitude Height above the surface True altitude True height above Mean Sea Level (MSL) Pressure altitude Altitude indicated whenever the altimeter setting dial is set to 29.92 (Standard Datum Plane) Density altitude Pressure altitude corrected for non-standard temperature and/or pressure. 7. Altimetry Standard day 29.92 Hg and +15 deg. C On a standard day at sea level, pressurealtitude, true altitude, indicatedaltitude, and density altitude are allequal. 8. High to lowlook out below When flying from an area of lowpressure/low temperature to an area ofhigher pressure/higher temperaturewithout adjusting the altimeter setting, thealtimeter will indicate lower than the truealtitude settingand vice versa. 9. Density vs. True Altitude 10. Vertical Speed Indicator (VSI) Operates only on staticpressure, but is adifferential pressureinstrument Operates on theprinciple of acalibrated leak Face of VSI outputschange in pressureover time displayed infeet per minute. 11. Airspeeds and Airspeed Indicator Airspeed Indicator Displays differencebetween pitot(impact) pressureand static pressure Pressures are equalwhen airplane isparked on groundin calm air. 12. Airspeeds Indicated airspeed (IAS) Uncorrected reading from the airspeed indicator Calibrated airspeed (CAS) Indicated airspeed corrected for installation and instrument error. True airspeed (TAS) Calibrated airspeed corrected for temperature and pressure variations. Groundspeed (GS) Actual speed of the airplane over the ground this is the TAS adjusted for wind. 13. Airspeeds color coded VSO stall speed / minimumsteady flight in landingconfiguration (lower limit of whitearc) VFE max. flap-extended speed(upper limit of white arc) VS1 stall speed in specifiedconfiguration (lower limit of greenarc) VNO max. structural cruisingspeed (top of green arc, bottomof yellow arc) VNE never exceed speed (upperlimit of yellow arc, marked in red) 14. Airspeeds, others VLE max. landing gear-extended speed. VA design maneuvering speed (flown inrough air or turbulence to preventoverstressing airframe) VY Best rate-of-climb airspeed (creates mostaltitude in a given period of time) VX Best angle-of-climb speed (airspeedresulting in most altitude in a given distance.) 15. Gyroscopic Principles Rigidity in space PrecessionAxis of rotation points in aTilting or turning of a gyro inconstant direction regardlessresponse to a deflectiveof the position of its base. force. 16. The Attitude Indicator Relies on rigidity in space Direction of bank determined by relationship ofminiature airplane to the horizon bar. Miniature airplane remains stationary horizon moves 17. Turn Coordinator Relies on precession As an airplane enters a turn, the TC indicates rate of roll. When bank is held constant, TC indicates rate of turn. Most TCs display an index on the Standard- rate turn, wherein the airplane takes 2 minutes to turn 360 degreers. The ball or inclinometer indicates quality of turn (skid/slip status). 18. Heading indicator Gyroscopic compass Magnetic compasses are difficult to read and sufferfrom errors; the heading indicator (also known as adirectional gyro or DG) DGs suffer from precession due to bearing friction the indicator must be realigned with the magneticcompass during straight-and-level, unacceleratedflight. 19. Magnetic Compass Compass points to magnetic north Susceptible to several errors 20. Compass Errors Variation Deviation Magnetic Dip 21. Dip errors Magnetic dip: When turning north from an easterly or westerlyheading, the compass lags behind the actualaircraft heading. When a turn is initiated whileon a northerly heading, the compass firstindicates a turn in the opposite direction. When turning south from an easterly or westerlyheading, the compass leads the actual heading.When a turn is initiated on a southerlyheading, the compass immediately leads ahead. Mnemonic: UNOS undershootnorth, overshoot south 22. Dip errors continued Accelerating or decelerating while headingeither east or west will also cause compasserrors. When accelerating on an east or westheading, the compass indicates a turn to thenorth. When decelerating on an east or westheading, the compass indicates a turn to thesouth. Mnemonic: ANDS acceleratenorth, decelerate south. Compass accurate only in S&L, unacceleratedflight. 23. Variation Errors Magnetic poles do not coincide with geographicpoles. Most places on Earth, thecompass needle does notpoint to True North. Angulardifferences betweenmagnetic north and truenorth are called variationsand are displayed onaeronautical charts. 24. Deviation Errors The metal, electrical systems, andoperating engine all create magneticfields from the aircraft. Aircraft manufacturers installcompensatory magnets to preventmost errors. Remaining errors arecalled deviation. A card in the aircraft will list thedeviation at various different compasspoints. 25. Next Week- Regulations- (FAR/AIM & Test Prep)