Within the airspeed indicator, there is a certain amount of trapped air. True airspeed (TAS) is the speed at which an airplane is moving relative to the air that surrounds it. The corrected airspeeds are indicated airspeed (IAS), calibrated airspeed (CAS), and equivalent airspeed (EAS). 82 in. Collect flight data on 3 legs 90 degrees apart. Enter CAS, fuel burn rate and cruise power setting in Nav Log. The formula used to calculate a safe speed for a lower weight is , where V A is maneuvering speed (at maximum weight), W 2 is actual weight, W 1 is maximum weight. Read the answer 195 knots (a). At 105TAS 86F burns 8. CAS is calibrated airspeed. What you see on the dial, is the IAS. 0 . You can calculate true airspeed by entering calibrated airspeed, pressure altitude, and temperature into a flight computer. Equivalent airspeed. Look up True Airspeed in your POH, and convert from MPH to KNOTS for your Nav Log. They are also resticted to only subsonic speeds. The window that is between “1:30” and “1:50” on the hour scale is labeled “DENSITY ALTITUDE” and the arrow points to the density altitude. The equations for equivalent airspeed and for calibrated airspeed were developed from the true airspeed equation by setting selected local parameter values to their sea level, standard day equivalents. It can also reduce the chance of a stall. 25 to about 800 hectopascals. Calibrated airspeed is the speed which, under standard sea level conditions, would give the same impact The different airspeeds: IAS is indicated airpseed. . This example shows the differences between corrected airspeeds and true airspeed (TAS). The inverse applies as you roll out. 1) the following: (a) pressure ratio (b) pressure altitude (c) temperature ratio (d) density. To correct for these errors, manufacturers provide an airspeed calibration chart for each aircraft. Calculate the speed, Mach number, 0. But, back to the controller’s request to. **Special thanks to Mesh Education Services (who provided the E6B demonstration footage. An analog true airspeed indicator for an airplane. The recommendation by ICAO is to use km/h, however knots is currently the most used unit. In some very high speed aircraft equivalent airspeed is calculated instead of. The calibrated airspeed takes the aircraft specific known value of the calibrated airspeed offset for each aircraft and applies it to the indicated airspeed reading. 8 1. 7. $\begingroup$ My understanding is that you could calculate TAS from CAS derived from the IAS you observe, but the derivation for your particular aircraft may differ slightly from the factory plans, so using the HHT with GPS to calculate TAS would give an entirely independent measure of TAS that you could use to verify your calibration equation. Because of that, you can't directly measure true airspeed, but you can calculate it with an E6B (some analog airspeed indicators have a window to compute true airspeed as well). "An extension of this idea is to fly three legs at the same altitude and airspeed. Generally calculated from the true airspeed corrected for wind vectors, the groundspeed is commonly displayed in real-time on the entertainment system for passengers. GS (groundspeed). That speed is used for performance related airspeeds such as stall speed, minimum control speed, V1, VR, V2,. It will compute the density altitude, mach number and true airspeed in knots, given the pressure altitude, temperature, and calibrated airspeed in knots. 6 m/s. Although indicated airspeed (IAS) and true airspeed (TAS) are the speeds most commonly used in aviation, references to calibrated airspeed (CAS) and equivalent airspeed (EAS) are quite often encountered. A free windows calculator which converts between various airspeeds (true / equivalent / calibrated) according to the appropriate atmospheric (standard and not standard!) conditions. Calculators Airspeed Conversions (CAS/EAS/TAS/Mach) An airspeed calculator designed to convert between indicated/calibrated airspeed and true air. 25 to about 800 hectopascals. Find the True Lift-Off Speed [KTAS]. Indicated airspeed is measured using the pitot-static system. It will compute the true airspeed in knots and Mach number and density altitude, given the pressure altitude, temperature, and calibrated airspeed in knots. Navigation Log. You do this using an E6B. Procedure: 1. Groundspeed is true airspeed corrected for wind. Standard Atmosphere of 1976 and are subject to the same 32,000 [m] limitation. It is dynamic pressure, indicated as speed at which that dynamic pressure would occur at sea-level standard conditions. True airspeed is the airspeed that we would read ideally. Units other than knots and inches of mercury can be used, if used consistently. You have static port - registering pressure around your aircraft, pitot tube, registering how many molecules of air getting inside. For the purpose of lift and aircraft performance we calculate the kinetic energy by replacing the M (mass) in the formula by air density (mass of the air per square meter),. How exactly does a G1000 system equipped with a GDC 74 air data computer calculate the indicated airspeed that is displayed on the PFD from difference between the total and static pressure. 2. It is set to a default value of 1 . Back to Lesson. And you use them all in every flight. Interestingly, the load factor incurred by abruptly pulling back on the yoke at a particular airspeed turns out to depend only on V S. (412TW-PA-12762). You need to specify the altitude at which you would like to perform the calculation as well as any one of the four airspeeds . This simple device is a convergent-divergent duct. When flying at high altitudes and higher airspeeds, calibrated airspeed is always higher than equivalent airspeed (EAS). Calibrated airspeed is defined as the indicated airspeed corrected for instrumentation errors in the pitot-static pressure measurement system. The POH will have a table for converting between indicated airspeed and calibrated airspeed. Let's say your CAS is 120 knots. press "Eval" on any remaining field for that field's result. Groundspeed is true airspeed corrected for wind. flaps values) are valid at sea level and 15°C. Since the airspeed indicator capsule responds to impact pressure, CAS is defined as a function of impact pressure alone. This expression is based on the form of Bernoulli’s. Atmospheric Pressure or Pressure Altitude and see the remaining field be calculated. To climb, add power. 0065 K/m (Kelvin per meter); h: Altitude above Mean Sea Level (MSL) (meters); Tc: OAT Estimation Correction (Kelvin); Impact on Society. If On, the aircraftUse this tool to calculate the Pressure and Density Altitude from airfield elevation, the local QNH , the Outside Air Temperature and the Dew Point. The IAS is typically used for low speeds and low altitudes. A high-speed subsonic aircraft is flying at an altitude where the pressure and temperature are 150 000 Pa and 250 K, respectively. 5 (which is not the correct answer to the previous question). The air-speed indicator fitted to a particular airplane has no instrument errors and is calibrated assuming incompressible flow in standard conditions. If the ambient air temperature is 230 K. On older aircraft, airspeed is usually indicated to the pilot on a graduated scale over which a pointer moves ( the first diagram). Calibrated Airspeed (CAS) corrected for altitude and non-standard temperature - the speed of the aircraft relative to the airmass in which it is flying. I am using two pressure sensors to measure altitude & airspeed via static /pitot lines. . However, I probably already calculate some of the factors for it in my Test Calculations. Then you’ll want to take your CAS and get IAS, which you can do by finding the IAS-CAS calibration chart in your POH. CX3. TAS is true airspeed. From the manual for an electronic E6B which seems to be similar to yours:. For a basic True Airspeed Indicator (TAS Meter) like the one shown below, you simply dial your pressure altitude into the top window using the knob (aligning it with the appropriate temperature mark at the bottom of that window), and then read your true airspeed in the other window at the bottom. |. 2GPH = 7. And indicated airspeed is equivalent airspeed plus measurement errors (calibrated airspeed is cleared of those errors, that can be effectively estimated). Internet :: WWW/HTTP :: Dynamic Content. Your POH usually lists a bunch of power settings and the TAS and fuel burn for each one. Calibrated airspeed is usually only a few knots different. Follow. [2] This is the pilots' primary airspeed reference. (Dynamic Pressure. the minimum-thrust-flight condition provide an accurate prediction within considered airspeed and altitude range. Calculators. Calculate the recovery, purity, and efficiency. True Airspeed (TAS) is the actual speed of the aircraft through the air corrected for altitude and temperature. To calculate the calibrated airspeed, you adjust the true airspeed for errors introduced through the pitot-static airspeed indicators used to determine airspeed. The GPS calibration method involves flying at a constant indicated airspeed (say 60 mph indicated) at three different headings. A more realistic illustration of aerodynamic and gravity forces acting on an airplane in straight and level flight is shown below. (The front section’s cross-sectional area decreases in the. Given the definition of calibrated airspeed, we sometimes need to compute it based on the actual measured values of the static pressure p0 and freestream Mach number M. 1323(b) includes the following requirement for the airspeed indicating system: The system error, including position error,. Please answer using this given info: calibrated airspeed = 154 kts pressure altitude = 352. g. Since the airspeed indicator only. Of particular interest in this calculator is the Equivalent Airspeed, which is essentially the calculation of IAS that aircraft display as the primary airspeed reading. How fast an airplane can go in level flight depends on the amount of drag and the amount of horsepower. You need to specify the altitude at which you would like to perform the calculation as well as any one of the four airspeeds . IAS figures in aircraft manuals are actually converted from CAS. Look for the letters ‘CAS’ for calibrated airspeed and ‘TAS’ for true airspeed. 4. therefore taken in miles per hour. The model's Display block shows both indicated and calibrated airspeeds. Jun 13, 2016. 6). = ( 𝑀 + 1) 𝑃1 2. Version 1. . Can also convert to Mach number and Equivalent airspeed. In the aeroblk_calibrated model, the aircraft is defined to be traveling at a constant speed of 70 knots (indicated airspeed) and altitude of 500 feet. The reason is somewhat deeper than just the indication. Airbus A350. Page 21 10000. I just wanted to mention that the non-approximated version of the formula to compute the true altitude is: htrue = h + h T0 ⋅(TOAT −TISA) (1) (1) h t r u e = h + h T 0 ⋅ ( T O A T − T I S A) where the value usually represented by 4 1000 4 1000 is in fact 1 T0 = 1 288. Knots Calibrated. From the manual for an electronic E6B which seems to be similar to yours:. This formula provides an estimate based on altitude. 4. This value is not corrected for installation error, instrument error, or the actual encountered air density, [2] being instead calibrated to always. The turning radius depends on the wind conditions. A high-speed subsonic McDonnell-Douglas DC-10 airliner is flying at a pressure altitude of 10 km. Note 2: If you don't have the Calibrated Airspeed (CAS) use Indicated Airespeed (IAS) in place of CAS. Calibrated Airspeed. KTAS is true airspeed given in knots. Within the realm of Aeronautical Engineering and Aviation, True Airspeed (TAS) plays a pivotal role. Indicated airspeed ( IAS) is the airspeed of an aircraft as measured by its pitot-static system [1] and displayed by the airspeed indicator (ASI). K: The instrument calibration factor of the airplane . In the airspeed window enter FL400 against the OAT. Andrew Wood. Above 35 knots, the deviation between the two systems varies between about –1 knots and +2 knots. The true airspeed (TAS; also KTAS, for knots true airspeed) of an aircraft is the speed. It implicitly includes air density and thus altitude). I did 3 legs on my private XC navlog, but it’s really as many as necessary (it could be 1, 2, 3, whatever). 7mph (178km/h) at Sea Level. 2. If the ambient air temperature is 300 K, calculate the true airspeed and the calibrated airspeed. the other end of the tube (point B) is closed, as shown in the figure1. Jupiter has a definable surface, calculate the altitude above that surface where the pressure is one-half the surface pressure. Back in February 2019, a Virgin Atlantic Boeing 787 jet flying over Pennsylvania in route from Los Angeles to London reached what might seem like an amazing speed of 801 miles per hour (1,289 kilometers per hour),. It’s an important parameter in aircraft design and operation, as it provides a more accurate representation of an aircraft’s true. 5 power. Calibrated airspeed is equivalent airspeed modified with compressibility effects of air, which affect the airspeed indicator. Finally, the Calculate IAS subsystem uses the flap setting and calibrated airspeed to calculate indicated airspeed. which can be. The pitot probe mounted on the aircraft measures a pressure of. Use equivalent airspeed to calculate true airspeed. Find the Wind Wind is a problem during airspeed calibrations. The calculation of true airspeed requires air density, which is determined from measurements of temperature and pressure. The aircraft's Mach number, pressure. A 50,000 lb aircraft flies in level flight (i. CAS = interp1( flaps0IAS, flaps0CAS, fltdata(:,4) ); The atmospheric properties, temperature (T), speed of sound (a), pressure (P), and density (rho), are determined at altitude for standard day using. ¶ Calibrated airspeed - CAS. With a true airspeed of 100 knots and a tailwind of 20 knots, you'd be flying a groundspeed of 120 knots. A simple computational procedure (see, for example Advisory Circular 23-8B, FAA, 2003) allows one to compute true airspeed, wind speed, and wind direction. Remembering the relationship between the various speeds and understanding the conversion from one to another can be facilitated. When you read the Airspeed on the Airspeed Indicator Flight Instrument, you are reading the Indicated Air Speed (IAS). Sorted by: 9. (FLASHING) T 232. True airspeed (TAS) - IAS cor rected for instrument installation error, compressibility error, and errors due to variations from standard air density. At this altitude, the air pressure drops from 1013. The model's Display block shows both indicated and calibrated airspeeds. Boldmethod. Simply enter the figure into the calculator, and you'll have the response in mph, ft/s, m/s, and km/h in the blink of an. 00:21. [In straight flight]: Assume that wind speed is fixed, calculate airspeed from wind speed, ground vector and heading. 6 m/s (133 knots) despite the fact that you are moving with 75 m/s (146 knots) with respect to the air. Knowing your True Airspeed has other advantages as well. Indicated Airspeed. D. •. 31 CL_Max which is standard for a laminar flow wing. At sea level under ISA conditions, equivalent airspeed and calibrated airspeed are the same. . 92 in the altmeter. KCAS (Knots Calibrated Airspeed) Like KIAS, but corrected for instrumentational or positional errors. Airspeed Exercise Part 1 document). I'm not sure why you would want to calculate what your airspeed indicator is showing you directly. True airspeed is the airspeed that we would read ideally. 0) at a calibrated airspeed of 290 kts. So we can calculate the new ratio as: Letʼs look at the airspeed indica-tor as an example. One of the common pieces of aviation knowledge that you. 65 × 10 4 N/m 2 at 10 km. In this example, pressure altitude is 10,000 feet, temperatureThe airspeed indicator measures the difference between the static pressure from static ports and the ram pressure from the pitot tube. TAS is more accurate for navigation and performance calculations. If using the lower portion (2nd calculator), enter the Absolute. The errors are most pronounced in slow and high angle-of-attack flight. In aviation, equivalent airspeed ( EAS) is calibrated airspeed (CAS) corrected for the compressibility of air at a non-trivial Mach number. Calculate the Calibrated Airspeed. Calibrated output airspeed, returned as a scalar, in the units specified by the Units parameter. If the ambient air temperature is 230 K. To calculate the calibrated airspeed, you adjust the true airspeed for errors introduced through the pitot-static airspeed indicators used to determine airspeed. To learn more about how it works, read on. It’s the speed at which you move through the air, and it increases as altitude increases. speed of sound. Use the atmoscoesa function to first calculate the speed of sound ( sos) and. Before you read aGround Speed GS - TAS further corrected for wind Indicated to Calibrated POH 5-10 Calibrated to True Airspeed E6B Course and Heading True vs Globe Heading vs Course TC +/- WCA = TH, E6B TH +/- VAR = MH, Isogonic lines (Dashed Magenta line, East least, West is best) MH +/- Dev = Corr. A Pitot tube on the wing tip measures pressure of 4. 43. E6B, NavLog Calculator, Weather Reports, METAR, TAF, Wind Components, Instrument Simulator, Weight and Balance, Pressure Altitude, Density Altitude, True Air Speed. Yeah, I agree, these definitions are kind of hard to wrap your head around so, let’s break it down. Finally, the Calculate IAS subsystem uses the flap setting and calibrated airspeed to calculate indicated airspeed. Description An air data computer (ADC) is an essential avionics component found in aircraft. At this altitude, the air pressure drops from 1013. Convert between Calibrated Airspeed (CAS), Equivalent Airspeed (EAS), True Airspeed (TAS) and Mach number (M) using the tool below. To calculate the ambient pressure from measured staticMechanical Engineering questions and answers. Indicated airspeed (IAS) is what you read off the airspeed indicator as you fly. TAS is CAS corrected for altitude and non-standard. Calculate the maximum rate of climb at each density altitude: ?ℎ?? = (?????) ?? (550)(60)? ? (feet/minute) 10. Calibrated Airspeed (CAS) is the IAS corrected for errors in measurement and instrument errors, on modern aircraft this is the airspeed displayed on the speed tape. Problem 5: A high-speed subsonic aircraft is flying at a pressure altitude of 10 km where the ambient temperature. Finally, the Calculate IAS subsystem uses the flap setting and calibrated airspeed to calculate indicated airspeed. I found a lot of rules of thumb. A Pitot tube on the wing tip measures a pressure of 4 x 10 4 N/m 2. Can read ground speed (and often actual air speed) Calculate directly without calculating the calibrated airspeed as an intermediate step. They are shown in IAS on. Now calculate the calibrated airspeed (ft/s, m/s, and kt) using equation 3. Calibrated airspeed (CAS) is indicated airspeed corrected for instrument errors, position errors (due to incorrect pressure at the static port) and installation errors. In the aeroblk_calibrated model, the aircraft is defined to be traveling at a constant speed of 70 knots (indicated airspeed) and altitude of 500 feet. The reason for that is that at different flap positions, air flows differently around the pitot-static system and affects the indicated airspeed readings. An aircraft can move faster when the air is thinner, but this won’t appear on the airspeed indicator, because when the air is thinner, so is the air entering the pitot tube. The speed transition from indicated airspeed to Mach usually occurs between 27,000 and 28,000 feet because this is where the two speeds intersect. At sea level, and an atmospheric pressure of 1013. So, at 10,000 feet, true airspeed is roughly “T ratio – Mach Number relationship”. 000890 sllugs/ft3 a) The true airspeed can be obtained by finding the speed of sound, since the Mach number is given. Show that the relation between pressure coefficient C and Mach number Mat any point on the airfoil surface is. The CAS is used for aircraft certification and. You're at 70 knots, flaps up in a Cessna 172S. 16 4576. Calculate True Airspeed Given Indicated Altitude, Altimeter Setting, Temperature, and Indicated/Calibrated Airspeed. (TAS)/calibrated airspeed (CAS) or. 2 GPH. Then I would go into the FLT menu on the CX-3, and select Airspeed, and I would input all the values that you have, such as OAT, pressure altitude, and now CAS (calibrated airspeed) 0 Votes. 3. For navigation the CAS is the first step to calculate the GS. This is simple. and 16 each calibration mark is equal to . Step 1: From the drop-down list next to each quantity, choose the desired units. KTAS (Knots True Airspeed) Airspeed corrected for changing atmospheric pressure at different altitudes. — Profile Valid: This allows you to set your profile On or Off once all data is entered . 2. 08 J/kg. 00347 1 T 0 = 1 288. Equivalent airspeed is calibrated airspeed with compressibility effects of air which affect the airspeed indicator removed. Wind Speed: The speed of the wind encountered by the aircraft. Ground speed is the actual speed of the aircraft relative to the ground. 16 4576. All V-speeds are defined in term of "calibrated" airspeed (CAS). Please enter your credentials below!Airspeed and ground speed are completely different when it comes to determining how fast an airplane flies. Use the atmoscoesa function to first calculate the speed of sound (sos) and static air pressure (P0). The ground speed and track direction can be calculated by repeatedly measuring the location of the aircraft and dividing the distance by the time between measurements, or with modern aircraft it can be read directly from the GPS display. Flying the reverse (westbound at 250 kts true airspeed) with a tailwind of 100 kts results in a GS of 350 kts. A7-4. Calculate True Airspeed (TAS) from data using internet program. AERODYNAMICS 1 PREPARED BY: ENGR. have to be calibrated via flight tests. e. For our purposes, equivalent airspeed is close to indicated airspeed in a well-calibrated system at sea level at standard pressure and temperature. Just as an example, one of the things it’s adjusted for is the flap position. You can use the Aerospace Toolbox correctairspeed function to calculate TAS, CAS, and EAS from one of the other two. PLANNED TRUE AIRSPEED (PLAN TAS) This function is used to calculate true airspeed for preflight planning. The errors are most pronounced in slow and high angle-of-attack flight. 3. B. The ASI measures the pressure differential between. Calibrated airspeed is always referred to as an indicator of the difference between p t and p s . They should be at least 1 centimeter out past the nose. E6B. 1. This calculator is designed to give a corrected value known as TAS, or true airspeed. 149, Minimum Control Airspeed (Vmc) is the calibrated airspeed at which a multi-engine aircraft should fly when there is loss of a critical engine. The center of pressure moves forward as the angle of attack increases and rearward as the angle of attack. Calculate the Mach number at which the airplane is flying. It doesn't take much to shut down the whole system. Mechanical Engineering questions and answers. 15)In this video, I go over how to calculate your True Airspeed during the climb portion of your cross-country flight. The formula for calculating True Airspeed (TAS) from Indicated Airspeed (IAS) is TAS = IAS + (IAS * (pressure altitude / 1,000) * 2%). Equivalent airspeed. Calibrated airspeed is IAS corrected for installation and instrument errors. The more of each, the more lift. Dummy example: Static registers 100 molecules around. This calculator is designed to give a corrected value known as TAS, or true airspeed. Show. 05x + 0. At this airspeed, the IAS and CAS are the same due to the AOA and "design" of the pitot tube. CAS is another type of airspeed used in aviation, and it is not corrected for wind effects like ground speed. (No flaps, level flight) That's Wing Lift Coefficient of 1. If the Subsonic airspeeds only check box is selected, the Ideal Airspeed Correction block generates code that includes subsonic (Mach < 1) lookup table data. An experimental rocket powered aircraft is flying with a velocity of 3000 mph at an altitude where the ambient pressure and temperature are. Released: Aug 31, 2022. Because air density decreases with an increase in altitude, an aircraft has to be flown faster at higher altitudes to cause the same pressure difference between pitot impact pressure and static pressure. Up until Mach-related effects come into play, CAS is what the airplane 'feels' as speed, and consequently, is all the pilot needs to know. . However, temperature and altitude also affect the behavior of an aircraft in flight. Density altitude is a measure of air density. Boldmethod. Assume R = 287. None of the choices 1290. An ADC can determine the pressure altitude, vertical speed, calibrated airspeed, true airspeed (TAS), and density altitude (DA). Now look on the B scale to find your calibrated airspeed (CAS), which can be found in the limitations section of your pilot's operating handbook (POH). To calculate True Airspeed (TAS) from Mach number, you can use the formula TAS = Mach × √ (γ × R × T₀), where γ is the specific heat ratio, R is the gas constant, and T₀ is the standard sea-level temperature in Kelvin. [ft/s or m/s] Version Information. Density altitude is a condition that affects aircraft performance. 2 mb, and with no wind effect, the airspeed indicated is the true speed of the aircraft relative to the surface. For ease of use. Indicated Airspeed from True Airspeed Calculation; On this page; Provide a True Airspeed; Calculate the Calibrated Airspeed; Adjust to Indicated Airspeed for Pitot-Static Airspeed Indicator; See Also; Related Topics(b) V CL MAX is determined with: (1) Engines idling, or, if that resultant thrust causes an appreciable decrease in stall speed, not more than zero thrust at the stall speed; (2) Propeller pitch controls (if applicable) in the takeoff position; (3) The airplane in other respects (such as flaps, landing gear, and ice accretions) in the condition existing in the. It will compute the true airspeed in knots and Mach number and density altitude, given the pressure altitude, temperature, and calibrated airspeed in knots. Equivalent airspeed is calibrated airspeed corrected for the compressibility of air at a non-trivial Mach number. (Dynamic Pressure definition and formula can be reviewed in “Flight Theory and Aerodynamics” page 30 (EQ 2. At the most basic level the Mach formula is: Mach = TAS/Speed of Sound The speed of sound is a slightly non-linear function of temperature: 38. True airspeed is the airspeed of an aircraft relative to undisturbed air. g. For example - assume a flight plan with following checkpoint information:. In still air, the TAS is equal to the groundspeed. During clean flight, position and instrument errors are usually small. To calculate the calibrated airspeed, you adjust the true airspeed for errors introduced through the pitot-static airspeed indicators used to determine airspeed. . At any other altitude, equivalent airspeed will be. Go to the Airplane Flight Manual. load factor, N Z =1. To calculate the calibrated airspeed, you adjust the true airspeed for errors introduced through the pitot-static airspeed indicators used to determine airspeed. The derivations of equations (1) and (2) are found in reference 1. ) Share. Flight data was. For your planned cruise power setting and density altitude, determine the Calibrated Airspeed (CAS) and fuel burn rate in cruise. It is the true figure for how fast you are moving through the air. 20% faster than what you read off your airspeed indicator. To find true airspeed, you’ll need an E6B flight computer. Airspeed Conversions (CAS/EAS/TAS/Mach) Calculators. 2 for the density factor, which should actually be 1. Among the common conventions for qualifying airspeed are: indicated airspeed ("IAS"), calibrated airspeed ("CAS"), true airspeed ("TAS"), equivalent airspeed ("EAS") and density airspeed. 3. To calculate the true airspeed of your aircraft, fly three separate legs, in rotation, at headings that differ by 90 degrees. What is the difference between calibrated and true airspeed? Calibrated Airspeed (CAS) is the indicated airspeed corrected for instrument and position errors. The formula for CAS is long and nested. Repeat Steps 4 and 5 for all planned altitude blocks. Set those values in the window. 2 Answers. It will be equal to the sum of the true airspeed of the. True airspeed is calibrated airspeed corrected for altitude and nonstandard temperature.