Flight Instruments Which way’s up? Written for the Notre Dame Pilot Initiative By the Pilots of the University of Notre Dame “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Roadmap Pitot-Static System Vacuum System Magnetic Compass

Flight Instruments Pitot-Static System and Instruments Airspeed Indicator (ASI) Vertical Speed Indicator (VSI) Altimeter Vacuum System and Instruments Attitude Indicator Heading Indicator Turn Coordinator Suction Gage Magnetic Magnetic Compass

Pitot-Static “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Atmospheric Conditions International Standard Atmosphere (ISA) Pressure = 29.92 inches Hg at sea level Temperature = 15C (59F) Standard Lapse Rates Temperature lapses at 2C per 1,000 feet Pressure lapses at 1.00 inch Hg per 1,000 feet

Airspeed Indicator (ASI) V-speeds VA = maneuvering * VFE = flap extend VLE = landing gear extended VLO = landing gear operating VNO = max structural cruising speed VNE = never exceed speed VR = rotation VX = best angle * VY = best rate * VS = stall clean configuration VSO = stall landing configuration not on ASI (contained in POH) Arcs White Bottom = VSO Top = VFE Green Bottom = VS Top = VNO Yellow Bottom = VNO Top = VNE Red Line = VNE

Types of Airspeed Indicated Airspeed (IAS) Calibrated Airspeed (CAS) Speed indicated on ASI Calibrated Airspeed (CAS) IAS corrected for calibration error Equivalent Airspeed (EAS) CAS corrected for compressibility error True Airspeed (TAS) EAS corrected for density error Altitude Nonstandard temperature Groundspeed (GS) Speed over the ground TAS adjusted for wind

At greater altitudes, the same volume of air contains fewer molecules of the gases that make it up. This means that the density of air decreases with increasing altitude.

Density Altitude

Altimeter 10,000s 1,000s Kollsman Window 100s Adjusting Knob

Altimeter & Types of Altitude Indicated Altitude Altitude indicated on altimeter Pressure Altitude Height above standard datum plane Altitude indicated when set to 29.92 inches Hg Density Altitude Pressure altitude corrected for nonstandard temperature airplane performance decreases with high density altitude True Altitude Actual height above mean sea level (MSL) Absolute Altitude Actual height above ground level (AGL)

Altimeter Errors Flying from high pressure to low pressure without changing altimeter setting (instrument thinks you’re higher) indicated altitude will be higher than actual altitude one inch change in altimeter setting = 1,000 ft indicated altitude in same direction Temperature Impact on True Altitude Warm days Actual altitude is higher than indicated Cold days Actual altitude is lower than indicated

Vertical Speed Indicator (VSI) Rate Information shows stabilized rate of climb or descent Rate appropriate for student pilots is: 500 feet per minute (FPM) rate of descent or climb Several second lag

Blockages in Pitot-Static System Blocked Pitot System Affects Airspeed Indicator (ASI) only clogged pitot tube with clear drain hole shows zero airspeed clogged pitot tube with clogged drain hole shows airspeed varying with altitude Blocked Static System Affects all pitot-static instruments ASI = inaccurate airspeed indications VSI = constant zero indication ALT= frozen at altitude where blockage occurred

Blockages in Pitot-Static System

Vacuum-System “Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”

Vacuum System Instruments -Works by sensing the differences in pressure from vacuum and from outside air. -Diaphragm

Turn Coordinator Miniature Airplane Level Index Turn Index level flight Turn Index standard rate turn (3 deg/sec) Shows roll and yaw of airplane Ball shows whether the angle of bank is coordinated with the rate of turn

Attitude Indicator (AI) Artificial Horizon blue side up Miniature Airplane Pointer Bank Scale 10 bank 20 bank 30 bank 60 bank Adjustment Knob

Attitude Indicator Examples

Heading Indicator (Directional Gyro) Typically “free gyros” no built-in north-seeking capabilities Periodically align with compass – error due to gyroscopic precession Use 360 azimuth right-most zero omitted 340 is shown as 34 60 is shown as 6 Adjustment Knob

Magnetic Compass Variation - angular difference between Magnetic North and True North. Shown on sectionals and will be taught in navigation lessons Deviation - compass error due to disturbance from metals and electrical accessories within the airplane. Correction card shows adjustments to magnetic heading Accurate only when flying in smooth air, in straight & level, unaccelerated flight When on easterly or westerly heading, use the mnemonic acronym ANDS, “Accelerate North, Decelerate South” Turning Error Compass lags when turning from north. Compass leads when turning from south. Use acronym, NOSE, “North Opposite, South Exceeds