Systems Flight Instruments Overview Deice and Antiice Systems

Systems & Flight Instruments

Overview • Deice and Anti-ice Systems • Reference Systems • Flight Instruments • Instrument Preflight © 2015 Coast Flight Training. All Rights Reserved.

Deice vs. Anti-Ice • • Deice Systems – used to remove ice after it forms Anti-ice Systems – used in advance to prevent ice from accumulating Some systems act as both Deice and Anti-ice Breakdown of Anti-ice/Deice systems • Induction • Structural (wing, pitot, windscreen, etc. ) • Propeller (if applicable) © 2015 Coast Flight Training. All Rights Reserved.

Induction Ice Control • Keeping ice out of engine air intake areas • Heated inlets on turbine engines (exhaust gas) • Carburetor heat for piston engines • Piper Archer and Piper Seminole have carburetor heat © 2015 Coast Flight Training. All Rights Reserved.

Heated Engine Inlets • Typical for turbojet and turboprop aircraft • Some hot exhaust gas or hot bleed air is routed though piping inside the engine • Hot gas flows to the front engine nacelle • The extreme heat melts or evaporates any ice on contact prior to entering the engine inlet © 2015 Coast Flight Training. All Rights Reserved.

Heated Engine Nacelle (Inlet) © 2015 Coast Flight Training. All Rights Reserved.

Carburetor Heat Systems • Simple system of changing source of intake air • Carburetor heat off: Cool air comes from outside through an air filter • Carburetor Heat On: • A pilot operated handle turns a valve to cut off direct outside air • Intake air now comes from air that has passed over the muffler shroud and been heated having *Note: Use of Carburetor heat will enrich the mixture © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Structural Ice Control • Ice on wings greatly reduces lift • Ice on windscreen hinders pilot vision • Ice on sensors disrupts critical instrument readings such as altitude and airspeed • Use of multiple systems • Electrical • Pneumatic • Mechanical / Fluid © 2015 Coast Flight Training. All Rights Reserved.

Wing De-Icing Boots • • • Deice only Typical for turboprop and turbo-charged piston aircraft Leading edge of wings have rubber strips Strip held flat with vacuum pressure when not in use Strip uses pressurized air to inflate into ridges • Turboprops bleed air off the compressor section • Turbocharged pistons use the turbocharger compressor • Ridges break ice off the leading edge • If too little ice, ice will form on ridges • If too much ice, boots can’t break it © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Wing – Hot Wing System • Used on turbojets • Very hot air is bled off of the high pressure compressor section of the jet engine • Hot air is routed through piping in the leading edge of the wind to melt existing ice or prevent buildup • The hot air is vented at some point • Can be used as anti-ice or deice © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Wings – Fluid System • “Weeping Wing” • Ethylene-glycol solution • Flows aft from holes near leading edge • Fluid reacts to lower freezing temperature of the aluminum metal • Prevents ice from adhering to the wing surface • Cannot work once ice accumulates • Anti-ice only © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Windscreen Anti-Ice • Fluid type – ethylene-glycol solution • Electric heat – element in between two layers of windshield is applied an electric current • Defroster/Defogger – use of heat from muffler shroud • Installed in Archers, Arrows and Seminoles © 2015 Coast Flight Training. All Rights Reserved.

Instrument Systems • Electrically heated ports/probes • • Pitot port, static port, pitot-mast heat Stall warning sensor heat AOA, Fuel vents and other sensors Heated pitot-mast installed in Cadets, Arrows and Seminoles © 2015 Coast Flight Training. All Rights Reserved.

Propeller Ice Control • Fluid type – ethylene-glycol • Fluid sprays from the hub • Centrifugal force carries the fluid out toward the tips • Electrically heated prop boots • Inboard leading edge (slower moving part) requires ice protection • Outboard moves too fast for ice to build • System requires a high electric load • Heating element boot is divided into two sections • Electric current alternates to these blade sections © 2015 Coast Flight Training. All Rights Reserved.

Engine Driven Vacuum System • Engine driven vacuum pump pulls air from the instrument case. • Air is drawn into the instrument from the cockpit through an air filter • Normal pressure entering the case due to suction spin the gyros as it catches the rotor vanes • Gyro speeds vary between 8000 and 18000 RPM • Some aircraft have electric backup pump © 2015 Coast Flight Training. All Rights Reserved.

Reference Systems • Standard Pressure: 29. 92 in Hg or 1013. 2 mb • Standard Temperature: 59°F or 15°C • Deviations from standard result in different reading on certain instruments © 2015 Coast Flight Training. All Rights Reserved.

Pitot-Static System • System Description • • Pitot tube Static port Drain holes Lines • Instruments • Altimeter, airspeed indicator and VSI • Must be checked every 24 months © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Altimeter • There is a set of aneroid wafers (capsules) inside the case sealed at 29. 92” Hg • The static line allows atmospheric pressure to enter the case (not the wafers) © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

How the Altimeter Works • As altitude increases, static pressure decreases, thus pressure in the case decreases allowing the wafers to expand • As altitude decreases, static pressure increases thus pressure in the case increases causing the wafers to compress • The expansion/compression is linked to gears and turn the dials on the face of the instrument • The knob resets the position of the indicating needle according to altimeter setting © 2015 Coast Flight Training. All Rights Reserved.

Altimeter Error • Position error - In some installations, position error can be of considerable magnitude • Scale error - Caused by the aneroid wafers not assuming the precise size designed for a specific pressure difference • Mechanical error - Mechanical error is caused by misalignment or slippage in the gears and linkage connecting the aneroid wafers to the display © 2015 Coast Flight Training. All Rights Reserved.

Altimeter Errors • Density error - Non-standard temperatures cause an error in calculating altitude (not a problem because all react the same and vertical separation is still maintained) • Hysteresis - This error is a lag in the altitude indications caused by the elastic properties of the materials used in the aneroids. It occurs when an aircraft initiates a large, rapid altitude change or an abrupt level-off from a rapid climb or descent • Reversal error - During abrupt or rapid attitude changes, reversal error occurs; it is only momentary in duration © 2015 Coast Flight Training. All Rights Reserved.

Types of Altitude • Indicated altitude - Read off the altimeter • Pressure altitude - Height above standard datum plain • Pressure altitude = Indicated altitude when Kohlsman set to 29. 92” Hg • Density altitude - Pressure corrected for non-std temp • True altitude - Height above sea level • True altitude = Indicated altitude when Kohlsman set to current pressure setting • Absolute altitude - Height above the ground (terrain) © 2015 Coast Flight Training. All Rights Reserved.

Types of Altitude © 2015 Coast Flight Training. All Rights Reserved.

Calculating Pressure Altitude • To calculate pressure altitude: • PA = field elevation + (29. 92 – altimeter setting) x 1000 Note: Elevation refers to physical height above sea level; it can be an altitude in flight © 2015 Coast Flight Training. All Rights Reserved.

Calculating Density Altitude • To calculate Density Altitude: • DA = PA + (120 x (OAT °C– ISA temperature °C)) Note: ISA refers to the temperature it should be at the local altitude under standard temperature conditions. Example, sea level = 15°C, 6000 feet = 3°C. (use the temperature lapse rate of 2°C per 1000’ increase in altitude) © 2015 Coast Flight Training. All Rights Reserved.

Vertical Speed Indicator • The case contains a diaphragm connected directly to the static line • The case is connected to the static line through a calibrated leak © 2015 Coast Flight Training. All Rights Reserved.

How the VSI Works • Changing pressures (associated with climbs and descents) expand contract the diaphragm connected to the needle on the face • The VSI is connected to the static line through a calibrated leak • The leak allows pressure to flow in/out of the case slower than the diaphragm • This allows the VSI to measure the trend and rate of change using differential pressure © 2015 Coast Flight Training. All Rights Reserved.

VSI Errors • There is a 6 -9 second lag before getting an accurate of climb/descent • Trend is instantaneous • Instantaneous VSI (IVSI) has little or no lag © 2015 Coast Flight Training. All Rights Reserved.

Airspeed Indicator • The case contains a diaphragm connected to the pitot (ram air) line • The case is connected to the static line © 2015 Coast Flight Training. All Rights Reserved.

How the Airspeed Indicator Works • Measures difference in pressure between ram air in pitot tube inlet and atmospheric pressure from static port • The difference in pressures moves a diaphragm which links to the indicating needle on the face of the instrument © 2015 Coast Flight Training. All Rights Reserved.

Types of Airspeed • Indicated airspeed - Read directly from the indicator • Calibrated airspeed - Indicated airspeed corrected for installation / position error • Equivalent airspeed - Calibrated airspeed corrected for compressible airflow error (>10, 000 MSL and >250 kts) • True airspeed - Equivalent airspeed corrected for non-std temp and press • Groundspeed - True corrected for wind • Speed of movement across the ground – used for ETE) • Mach # - Ratio of true airspeed to local speed of sound © 2015 Coast Flight Training. All Rights Reserved.

Calculating True Airspeed • Prior to flight • Can be calculated by correcting calibrated airspeed for non-standard temperature • Cruising true airspeed can be found in charts • In-flight • Utilize scale on airspeed indicator • Align indicated altitude with ambient air temp • True airspeed indicated on the white sliding scale © 2015 Coast Flight Training. All Rights Reserved.

Pitot-Static System Erros • Pitot-tube freezes • The airspeed indicator will read zero as long as the static port is still clear • Static port freezes • Airspeed indicator will read accurately at the frozen altitude; reads higher if aircraft descends and lower if aircraft climbs • Altimeter freezes at frozen altitude • VSI indicated level © 2015 Coast Flight Training. All Rights Reserved.

Using Alternate Static Source • Prior to operation • Close all vents to cockpit and storm window • Turn on heater and defroster • Instrumentation indications • Airspeed indicator reads higher than indicated • Altimeter reads higher than normal • VSI shows a momentary climb © 2015 Coast Flight Training. All Rights Reserved.

Engine Vacuum System © 2015 Coast Flight Training. All Rights Reserved.

Gyroscopic Principles • Rigidity in space • A spinning gyroscope tends to remain aligned with its axis of rotation • Precession • When a force is applied on a rotating disc (gyroscope) it is felt 90 degrees in the direction of rotation from where it is applied © 2015 Coast Flight Training. All Rights Reserved.

Attitude Indicator • Depiction of aircraft position relative to horizon • Often called an artificial horizon • Gives instantaneous pitch and bank information • Contains a gyro with dual gimbals for movement • Display • Blue over brown indication mimics the horizon • A movable (miniature) aircraft © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

How the Attitude Indicator Works • A gyro uses pendulous vanes to stabilize the artificial horizon to the actual horizon • Using the principle of rigidity in space, the aircraft actually pitches and bank around the gyro and is indicated by the face © 2015 Coast Flight Training. All Rights Reserved.

Attitude Indicator Limitations • Exceeding below values can cause the gyro to tumble (spin erratically) and become inaccurate • Banking more than 110 degrees • Pitching more than 70 degrees © 2015 Coast Flight Training. All Rights Reserved.

Attitude Indicator Errors • During turns the gyro tend to precess inside the gyro, leading to a false indication of a climb and turn in the other direction after completing a 180 degree turn • Accelerating causes a false climb indication • Decelerating causes a false descent indication © 2015 Coast Flight Training. All Rights Reserved.

Attitude Indicator Check • After engine start and vacuum pressure, the gyro should align with the horizon within 5 minutes • Check the vacuum pressure • If it does not align then it is likely malfunctioning • During taxi, pilots should ensure that during turns on the ground the gyro does not bank more than 5 degrees © 2015 Coast Flight Training. All Rights Reserved.

Directional Gyro • The case contains a gyro mounted on 1 gimbal for single-axis rotation • The gyro is attached to a gear that connects to the face card • A knob can adjust the face card by disconnecting the gears and turning the entire card © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

How the Directional Gyro Works • The gyro stabilizes the indicator using between 10, 000 to 18, 000 RPM • The aircraft turns around the indicator according to the principle of rigidity in space © 2015 Coast Flight Training. All Rights Reserved.

Directional Gyro Limitations • Exceeding 55 degrees of bank or pitch may cause the gyro to tumble (spin erratically) and become inaccurate • Can be reset by momentarily caging the gyro • Do this by pulling the cage knob (if installed) and then releasing it © 2015 Coast Flight Training. All Rights Reserved.

Directional Gyro Errors • Error about 3 degrees every 15 minutes due to precession • Knowing this, the pilot should realign using the magnetic compass every 15 minutes and before attempting any holds, approaches or course tracking © 2015 Coast Flight Training. All Rights Reserved.

Horizontal Situation Indicator - HSI • Not a vacuum instrument, but related to DG • Not a gyro instrument, slaved to remote compass • Remote compass continually updates heading • It combines both the DG and the VOR/ILS display • Benefit of reducing workload and removing reverse sensing on backcourse © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

Turn Coordinator • Electrically driven gyro • Used to determine quality of turn • Standard rate turn indicated by white lines • Contains the inclinometer (slip/skid indicator) © 2015 Coast Flight Training. All Rights Reserved.

How does the TC Work? • Uses principle of precession • Yaw from turn causes force on side of gyro • Force is translated 90 deg in direction of spin, which rolls the gyro and mini airplane or needle © 2015 Coast Flight Training. All Rights Reserved.

Turn Coordinator vs. Turn and Slip Indicator • Turn coordinator has a gyro that is canted back 30 degrees and a set of calibrated springs • This allows the TC to indicate rate-of-roll © 2015 Coast Flight Training. All Rights Reserved.

© 2015 Coast Flight Training. All Rights Reserved.

TC/TS Errors • The only real error comes when the springs wear out or get out of calibration • This would cause erroneous indications © 2015 Coast Flight Training. All Rights Reserved.

Instrument Preflight Checks • Airspeed should read zero • Altimeter reads within 75’ of field elevation with correct altimeter setting applied • Attitude indicator becomes level within 5 minutes of vacuum pressure and does not bank more than 5 degrees on the ground in turns © 2015 Coast Flight Training. All Rights Reserved.

Instrument Preflight Checks • Heading indicator does not precess more than 3 degrees every 15 minutes • Turn coordinator is level with no flags while not turning • Vertical speed indicator reads zero © 2015 Coast Flight Training. All Rights Reserved.

Instrument Taxi Check • Check that attitude indicator does not bank more than 5 degrees in a taxiing turn • Check that the heading indicator turns in the correct direction when turning © 2015 Coast Flight Training. All Rights Reserved.

Instrument Taxi Checks • The turn coordinator turns in the direction of the turn, the “ball” should swing in the opposite direction (all ground turns are skids) • The compass should be full of fluid, free floating, turn in the correct direction and indicate a known heading (check when parallel to a runway: Rwy 5 = 050 or 230 if opposite) © 2015 Coast Flight Training. All Rights Reserved.

References • Pilot’s Handbook of Aeronautical Knowledge • Instrument Flying Handbook • Instrument Procedures Handbook © 2015 Coast Flight Training. All Rights Reserved.