(CAF 101) Theory of Flight Instruments Notes.pdf

SY 2024-2025 1st Trimester Prof: Capt. Jason Veralde Theory of Flight Instruments CAF-101 ___ Notes Module 1: 6 Basic Flight Instruments Divided into 2 groups: Pitot-Static Gyroscopic Airspeed Indicator Heading Indicato...

SY 2024-2025 1st Trimester Prof: Capt. Jason Veralde Theory of Flight Instruments CAF-101 ___ Notes Module 1: 6 Basic Flight Instruments Divided into 2 groups: Pitot-Static Gyroscopic Airspeed Indicator Heading Indicator Vertical Speed Indicator Turn Indicator or Turn & Slip Indicator Altimeter Attitude Indicator James Harold Doolittle - The first pilot to take off, fly and land an airplane using instruments alone Atmosphere - The spheroidal gaseous envelope surrounding a heavenly body Composition of atmosphere 78% Nitrogen 21% Oxygen 1% Other gas Properties of the Earth’s atmosphere Pressure - The application of force to something by something else - The pressure (force) exerted in every direction by the weight of the atmosphere Atmospheric Pressure - Force or weight exerted on any object by the column of air above the object. Pressure decreases from the point of measurement at the sea level to the top of the atmosphere. Temperature - Degree of hotness or coldness measured on a definite scale - When the pressure is cold, the slower the molecules move - When the pressure is hot, the faster the molecules move  Terrestrial Radiation Q: Why is it hotter at lower altitudes? - The sun heats up the earth’s ground, the earth’s ground releases the absorbed heat - There are many molecules in the earth’s ground, that’s why they are the first ones who will feel the heat from the earth Q: Why don’t molecules just pass heat to one another? - Air molecules are bad conductors of heat Density - Mass per unit volume - Amount of matter present in a given volume - More pressure on the ground means more air is there Mercury Barometer - Used to measure the Earth’s atmosphere International Standard Atmosphere or ISA Mean sea level - The level of surface of the sea especially at its mean position midway between high and low water * If we increase 1000 ft, the pressure - 1.00, the temperature - 2.00 * If we increase for example 500 ft, the pressure - 0.5, the temperature - 1.00 Altitude Pressure Temperature 0/MSL 29.92 in Hg. 15 C 1000 ft 28.92 in Hg. 13 C 500 ft 28.42 in Hg. 14 C Module 2: Airspeed Indicator Air Pressure Types Static Pressure (SP) - Atmospheric Pressure/ Ambient Air Pressure - Exerted equally in all directions regardless of motion Dynamic Pressure (DP) - Pressure exerted by the air as an object moves through it - Proportional to the airspeed and air density Total Pressure (TP) - Sum of the (SP) and (DP) Airspeed Indicator - Indicates the speed of the aircraft in relation to the air - Reads Dynamic Pressure to display airspeed - The faster you go, the more dynamic pressure - The lower you go, the less dynamic pressure \\ Explanation: Total pressure enters the pitot tube, the total pressure pushes the diaphragm outward. Now, the static pressure from the static port enters directly into the case, which now pushes the diaphragm inwards causing it to contract. Since the static pressure inside the diaphragm pushes the diaphragm outwards, this will cause both static pressure to cancel out which leaves remaining inside the diaphragm is the dynamic pressure which now expands the diaphragm into the gears and the gears rotate the needle dial that indicates the airspeed of the aircraft through the airspeed indicator. Now, when you slow down, the diaphragm contracts. Errors Position Error - When flying at high angles of attack, the airflow is not parallel to the longitudinal axis of the aircraft  Density Error - The dynamic pressure depends not only on the airspeed, but also on the density of the air Wind Error Airspeeds Indicated Airspeed (No Errors) - The speed indicated on the instrument - Does not include any correction Calibrated Airspeed (Instrument and Position Errors) - Indicated Airspeed corrected for instrument and position errors True Airspeed (Density Error) - The airspeed corrected for Density Error (Temperature & Pressure) - The real speed of the aircraft in relation to the air TAS Calculation - Flight Computer - Airspeed Indicator TAS Scale Rule of Thumb - TAS increases by 2% for every 1000 ft. Increase in altitude Groundspeed (Wind Error) - Actual aircraft speed in relation to the ground - The TAS corrected for wind 2 Units for Airspeed Indicator Knots MPH White arc - Flaps operating range Green arc - Normal operating range Yellow arc - Caution range Red line - Never exceed beyond this point Module 3: Vertical Speed Indicator aka The Variometer or Vertical Velocity Indicator (VVI) - Measures change in altitude - Indicates the rate at which the aircraft climbs or descends - Only need static pressure Gives 2 information: TREND and RATE Trend is the instant climb or descent of the aircraft (Shows the instant climb or descend) Rate is how fast you are climbing or descending and has a delay of 6-9 seconds (ft/min climb or descent) (Shows how fast you climb or descend) ex: 300 ft/min climb or 200 ft/min descent *You count the lines by hundreds *When you are stabilized with your altitude or when the dial is on zero, the trend is neutral LEVEL FLIGHT Explanation: Static pressure from the static port enters the diaphragm and the calibrated leak via the tubes. The calibrated leak controls the entrance and exit of the air pressure. Big static pressure when entered to the calibrated leak becomes smaller due to the tight space of the calibrated leak. Now the static pressure inside the diaphragm is equal to the static pressure inside the case and are pushing to each other that’s why there is no difference in pressure. DESCEND Explanation: When we descend, pressure gets bigger. The cause of delay is the tight space of the calibrated leak that makes static pressure take time to enter the case. CLIMB Explanation: The static pressure inside the case exits through the calibrated leak (which is tight) that will cause delays NOTE *The VSI gets it’s readings from the pressure differential between the static air pressure inside the diaphragm and inside the case Calibrated Leak - cause of delay Module 4: Altimeter - Measures Vertical Distance from a reference point 2 Units for Altimeter Feet Meters Types of Altimeter Barometric Altimeter - measures altitude based by atmospheric pressure Radio Altimeter - measure altitude based height above ground level (AGL) *Aircraft flying above up to the reference point or mean sea level (MSL) is called Altitude *Aircraft flying above up to the the highest point of the ground is called Height *From the mean sea level up until to the highest point of the ground is called Elevation Kollsman Window Triangular needle (10000 ft) Short needle (1000 ft) Long needle (100 ft) Q: How does an altimeter work? - It measures the pressure difference *29.92 is the constant or standard pressure of the Aneroid Capsule Standard Explanation: Pressure that enters from the static port will not cause the Aneroid Capsule/Wafer to expand or contract since they have the same pressure. It will instead cause them to be tight Climbing Explanation: Pressure coming from the static port is now lesser than the pressure inside the Aneroid Capsule, because of this, the Aneroid Capsule expands and pushes the gears and moves the needle Descending Explanation: 28.92 may be weaker compared to 29.92 but it has the force to kind of resist the movement of the aneroid capsule. So the aneroid capsule will now somehow contract because the static pressure inside got stronger a bit Q: How do you read the altimeter 2000 ft - The short needle is pointed at 2 so it’s reading is 2000  - The long needle is pointed at 0 so it’s reading is 000 - The triangular needle has not yet passed 1 which is 10000 feet so the reading is 00000 - Total: 2000 ft 12000 ft - The short needle is pointed at 2 so it’s reading is 2000 - The long needle is pointed at 0 so it’s reading is 000 - The triangular needle has passed 1 which is 10000 feet so the reading is 10000 - Total: 120000 ft 1800 ft - The short needle has not yet reached 2 so it’s reading is still at 1000 *When the short needle has not yet reached the next number, the reading will be the number before the next target number - The long needle is pointed at 8 so it’s reading is 800 - The triangular needle has not yet passed 1 so the reading is 00000 - Total: 1800 ft 1360 ft - The short needle has no yet reached 2 so it’s reading is still at 1000 - The long needle is at the 60 mark between 3 and 4 so it’s reading is 360 *The small lines between the numbers are counted by 20s - The triangular needle has not yet passed 1 so the reading 00000  Crosshatch Flag - Appears only when below 10000 ft - Disappears when above 10000 ft Types of Altitude Indicated Altitude - Altitude shown/indicated in the altimeter Calibrated Altitude - Indicated altitude compensated for instrument errors Absolute Altitude - Height or vertical distance above ground level (AGL) Pressure Altitude - Altitude when set to standard pressure (29.92 in. Hg.) True Altitude - Actual altitude above mean sea level (MSL) Q Codes QNE = 29.92 in. Hg. QNH = Mean Sea Level QNA = Current Pressure QFE = Field Elevation - How to find? When you are landed on the ground, rotate your barometric knob until the needle is back to zero and read the pressure in your Kollsman Window Explanation: When it is cold, pressure drops fast because air contracts but when it is hot, pressure takes time to drop because air expands *Air when hot, expands *Air when cold, contracts Standard Conditions: Equal IA and TA High Temperature: TA is higher than IA Density Altitude True Altitude Computation Flight Computer Approximate Formula Density Altitude - Pressure altitude corrected for non-standard temperature Factors Affecting Density Pressure Temperature Humidity 3 H - High, Hot, and Humid *Optional  QNH - Current Pressure Density Altitude Computation Flight Computer Table Approximate Formula [DA = PA + 120 (OAT - ISA)] Module 5: Attitude Indicator Gyroscope - Any symmetrical body rotating at a speed sufficient to experience gyroscopic effects - A rotating wheel, mounted so that its axis is free to move in one or more directions Gyroscopic Principles Rigidity in Space - A wheel with a heavily weighted rim spun rapidly will remain in a fixed position in the plane which it is spinning “Kahit anong position mo itapon ang gyroscope, the roter will always remain in a fixed position as long it is spinning fast” Precession - Tilting or turning of a gyro in response to pressure “It is spinning on a certain direction, if you would put force at this point, it will be felt 90 degrees toward that direction” Suction Gauge - It is essential to monitor if vacuum system is working Normal Range: 4.5 in. Hg. - 5.4 in.Hg. Q: How does a vacuum system work? Attitude Indicator - aka Artificial Horizon - Senses roll as well as pitch, down, which is the up and down movement of the airplane’s nose Gives 2 information: Senses Roll and Pitch Inside of the Attitude Indicator *Additional Info Module 6: Turn Indicators - Provide an indication of turn direction and quality as well as a backup of bank information in the event of attitude indicator failure Types of Turn Indicators Turn Coordinator - Mainly used in modern aircrafts Turn & Slip Indicator - The classic turn indicator Turn & Slip Indicator Turn Coordinator Correction (0 degrees per sec) Q: How to read the turn indicator? - When the needle/miniature airplane is pointed at the doghouse or turn index it means your aircraft is turning 3 degrees per second *3 degrees per second - Standard rate of turn Q: What is the 2 min turn? *It will take you 2 mins (120 sec) to make a 360 turn as long as you maintain the needle/miniature airplane in the doghouse or turn index *The box (pointed by the green line) will light up red when it does not receive enough power from the electrical system Inclinometer - Allows to measure “quality” of the turn , It has white kerosene inside Q: Why white kerosene? - Low freezing point  \ Coordinating Turn - Standard or Correct Way Skidding Turn - Over Turning Slipping Turn – Under Turning *Step on the rudder to fix if you are over/under turning Module 7: Heading Indicator aka Directional Gyro - Senses airplane movement and displays heading on 360° azimuth card Cardinal Heading North - 360° East - 090° South - 180° West - 270° Parts of the Heading Indicator Compass Rose (numbers and lines) Adjustment Knob Miniature Aircraft Current Heading (◇) *Right turn, Increase heading *Left turn, Decrease heading *Add 0 always to the number *Every line is 5° 2 Instruments give us Heading: Heading Ind. (Primary) (Relies on the Magnetic Compass) Magnetic Compass (More Accurate) (North Seeking Device) (A lot of errors) *To make the Heading Ind. accurate, realign it with the Magnetic Compass using the adjustment knob every 15 mins Q: Why do we need to realign? - Because the earth is rotating 15° per hour Module 8: Magnetic Compass - Instrument used to determine the orientation (heading) in relation to the Earth's magnetic north Magnetic North The direction that a compass needle points to as it aligns with the Earth's magnetic field. Shifts over time Geographical North / True North Where all longitudinal lines meet Fixed geographic reference point used for navigation, mapping, and other applications *Magnet inside the magnetic compass *Red is North, Blue is South *The magnet follows the magnetic north *Right turn, + *Left turn, - *They reverse/flip the card, so that wherever we heading, we can really see it *When the plane turns right, the compass card moves to the left and vice versa Module 9: Compass Errors Variation - aka Mag Var, Magnetic Declination - Angular difference between the true and magnetic poles at a given point *When the magnetic north is in the left, you are in the west variation *When the magnetic north is in the right, you are in the east variation *When there is no angular difference, there is zero variation Isogonic Line - lines of equal magnetic variation - imaginary lines on the Earth's surface that connect points with the same magnetic declination  Agonic Line - imaginary lines on the Earth's surface where the magnetic declination is zero *East variation we subtract, West variation we add Deviation - Compass error which occurs due to disturbances from magnetic fields produced by metals and electrical accessories within the airplane itself  Magnetic Dip *The nearer you get to the poles, the magnet will shift *It is angled to the magnetic north *Will cause problems in magnetic compass *The result of magnetic dip is acceleration error *It follows the magnetic field  Acceleration Error - Compass error that occurs when accelerating/decelerating on a westerly/easterly heading - More evident the farther from the equator  Turning Error - Compass error that occurs when turning to/or from headings of North/South - More evident the farther the equator