Flight Instrument Systems

1. Flight Instrument Systems

2. Gyroscopic Flight Instruments • Attitude Indicator • Heading Indicator • Turn Coordinator • Gyros are mounted on gimbals which allow the plane to move about the gyro which remains fixed in space

4. Fundamental Concepts • Rigidity in Space - a wheel with a heavily weighted rim spun rapidly tends to remain fixed in the plane in which it is spinning • Precession - when an outside force is applied the gyro responds as if the force had been applied at a point 900 further around in the direction of rotation

5. Pendulous Vanes • Open and close to help keep the gyro parallel to the ground • Act on the attitude indicator in an undesirable way during turns do to centrifugal force • Errors are at a maximum in a 1800 turn, no more than 50 of bank

6. Tumbling • Old attitude indicators would precess rapidly or tumble if you exceeded 1000 or 600 of pitch • Often these attitude indicators had a caging device to right them

7. Heading Indicators • Must be aligned with the magnetic compass to make it work (Free Gyro) • Must be checked approximately every 15 minutes • A heading indicator with a north seeking system is called a slaved gyro.

8. Turn Indicators • Standard rate turn is 30 • A 3600 turn takes 2 minutes • To determine the angle of bank required to make a standard rate turn take the (true airspeed in Knots divided by 10) + 5 • At 100 Knots it is approximately 150

9. Turn Instruments • Turn coordinator • Rate of roll • Rate of turn • Turn and slip indicator • Rate of turn only • Inclinometer

12. Slip and Skid • Slip - rate of turn is too slow for the bank and the ball moves to the inside of the turn • Skid - rate of turn is too great for the angle of bank and the ball moves to the outside of the turn

13. Slip

14. Skid

15. Instrument Checks • With the power off, warning flags display OFF indications • Inclinometer full of fluid and ball at lowest point • Turn on master and listen for grinding noise in electric gyros • After starting check ammeter

16. Instrument Checks • Listen for noise from vacuum gyros • If you think you hear noise, shut off the engine and listen to the gyros spin down • It can take 5 minutes for the gyros to reach full operating speed

17. Instrument Checks • While taxing out, the turn coordinator and heading indicator should indicate a turn in the correct direction • The ball should swing to the outside in turns • Align the heading indicator with the magnetic compass during runup and check again before takeoff

18. Magnetic Compass • Errors • Variation - the angular difference between the true and magnetic pole • Deviation - errors due to magnetic interference with the metal components of the aircraft • Magnetic dip - the compass tries to point down deep inside the earth

19. Variation

20. Deviation

21. Magnetic Dip

22. Northerly Turning Error

23. Acceleration Error

24. Pitot Static Instruments • Airspeed Indicator • Vertical Speed Indicator • Altimeter

25. Airspeed Indicator

26. Airspeed Indicator VSO VNE VNO VFE

27. Colored Arcs • Yellow - operate in the caution area only in smooth air • Green - normal operating range • White - full flap operating range

28. Types of Airspeeds • Indicated - displays the speed of your plane. It is the basis for determining your aircraft performance • Calibrated is indicated corrected for installation and instrument error • Equivalent airspeed is calibrated airspeed corrected for adiabatic compressible flow at a particular altitude

29. Types of Airspeeds • True Airspeed is the actual speed your airplane moves through the air. The calibrated airspeed corrected for density altitude • Mach is the ratio of the aircraft’s true speed to the speed of sound

30. Altimeter

31. Types of Altitude • Indicated - is what you read on the altimeter • Pressure - is displayed when you have the altimeter set to 29.92. It is the vertical distance above the standard datum plane • Density - pressure corrected for nonstandard temperature

32. Types of Altitude • True - is the actual height of an object above mean sea level. • Absolute - is the actual height of the aircraft above the earth’s surface

33. ISA • International Standard Atmospheric Sea Level - 150 C - 29.92 in HG • Before IFR flight the altimeter set to the current altimeter setting should be within 75 feet of the actual elevation

34. Vertical Speed Indicator

35. Vertical Speed Indicator • Displays rate and trend information • 6-9 second delay • Gives erratic readings during turbulence or when applying abrupt control inputs • Not setting before starting engines and use that setting for zero • Not legally required for IFR flight

36. Pitot Static System Ram air inlet Drain hole

37. System Errors • Can be caused by blockage of the pitot tube, static port or both • Blockages can be caused by moisture, ice, dirt or even insects • Use pitot tube cover when parked • Use pitot heat when flying in visible moisture

38. Pitot Blockage • Ram air inlet clogged, drain hole open pressure in line to airspeed indicator drops to zero, airspeed indicator indicates 0 • Ram air inlet clogged, drain hole clogged, air trapped in line, airspeed indicator does not react to changes in speed but altitude like an altimeter

39. Static Blockage • Airspeed indicator will continue to react to changes in airspeed but they will not be accurate • Altimeter will freeze in place • VSI will freeze at zero • Use alternate static source or break glass in VSI