Week 1 Tasks True Airspeed from Indicated Airspeed Calculation


(Airspeed formulas)

(link 1)

Using this code below to open up the True airspeed indicator calculations on simulink

  • open_system(‘aeroblk_calibrated’);
  • snapshotModel(‘aeroblk_calibrated’);
True airspeed (TAS) is the airspeed that we would read ideally (and the airspeed value easily calculated within a simulation). However there are errors introduced through the pitot-static airspeed indicators used to determine airspeed. These measurement errors are density error, compressibility error and calibration error. Removing these errors from indicated airspeed (IAS) will result in true airspeed

For errors referring to, Correcting Calibrated Airspeed for Compressibility and Density Errors, Compressibility Error, Density Error and Simulate Model to Display Airspeeds.

Mach to knots

the temperature and density of air decreases with altitude, which means so does the speed of sound, hence given a true velocity results in a higher Mach number at higher altitude.
airspeed is a very generic term and and is instead broken down into 6 different airspeeds-
  1. Indicated airspeed (IAS)- The reading obtained from the Airspeed indicator is incorrect if there is a variation in atmospheric density, installation error, or instrument error. “The Airspeed Indicator (ASI) measures the difference between the static pressure from the aircraft’s static ports, and the ram pressure (dynamic + static) from the pitot tube. This difference is the dynamic pressure, which translates into a reading.”  normal use as a basis for aircraft performance.
  2. Calibrated Airspeed (CAS)- This is used to correct installation error and instrument error. Has to be calibrated for each plane due to variations in parameters.
  3. True Airspeed (TAS)-  “True Airspeed is Calibrated Airspeed (CAS) corrected for altitude and nonstandard temperature. 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.”
  4. Ground speed (GS)- Ground speed is the speed of the airplane over the ground which is the true air speed adjusted for wind.
  5. Equivalent Airspeed (EAS)- “Equivalent Airspeed is Calibrated Airspeed (CAS) corrected for the compressibility of air at a non-trivial Mach number. It is also the airspeed at sea level in the International Standard Atmosphere at which the dynamic pressure is the same as the dynamic pressure at the True Airspeed (TAS) and altitude at which the aircraft is flying. It’s mainly used for structural calculations and testing.”
  6. Mach Number (M)- “The Mach Number is the ratio of the True Airspeed (TAS) of the aircraft to Local Speed of Sound (LSS) displayed on the Machmeter. M varies depending on atmospheric conditions, air temperature, and density.”


Development and evaluation of a new airspeed information system utilizing airborne Doppler LIDAR

(link 2)

Interesting points

  • The former shows the predicted airspeed typically ten seconds ahead based largely on the aircraft’s acceleration or deceleration, while the latter displays a target speed computed by the flight management system or set by the pilot. During the approach and landing phase, the pilot sets the target approach speed taking into account airport wind information provided by air traffic control and/or ATIS (Automatic Terminal Information Service) broadcasts. Although the autothrottle system controls airspeed using the target speed and acceleration information, satisfactory speed control performance might not be achieved when wind is changing rapidly because the control system assumes steady or slowly changing winds. Sudden changes in wind speed and direction (windshear) can force pilots to execute a go-around maneuver.

Avionics hardware and software-based systems and their architecture

  • Hardware“Every physical component of a device is hardware. You can reach out and touch hardware, you cannot touch software. Hardware includes all of the physical devices in a computer, like a motherboard, RAM, or processors. For devices like computers, hardware has a heavy influence on performance. Higher performance hardware tends to cost more and requires more resources. Powerful video cards or a CPU, for example, may require a lot of electricity and more cooling than weaker internal components. Most computer components perform better at cooler temperatures Hardware is limited in what it can do on its own. Hardware enables the technology to run, software is what is actually running. A good analogy is with a book. Hardware is the paper, binding, and ink. The primary purpose of hardware for most use cases is to allow the device to run software. Most users won’t have to worry much about computer hardware. Businesses often buy prebuilt desktop computers or laptops. This lets them leave most hardware considerations to professionals, from power supply to output devices. In hardware-related product categories like rack servers, vendors provide hardware and software so that users have a nearly out-of-the-box solution.”
  • Software“Software is all of the programs and code that runs on top of hardware for additional functionality. Software programs range from application software like MS Word or Photoshop to operating system software like Windows. Simple programs make computers able to be used by normal consumers. Unlike hardware, software is a nonphysical component of devices. Software, to continue the book analogy, is the illustrations and other content. Still, hardware is necessary for using software. More complex software may require more powerful hardware. Activities like rapid, complex calculations or highly detailed image rendering can have stringent hardware requirements to run correctly.  Weaker hardware can run less demanding software like PowerPoint or basic Excel functions.”

How do these interlink- Hardware and software both are interdependent on each other. Each of them should work along to form computer produce a helpful output. The software can not be used if there is no support of any hardware device. When there is no proper instructions given, the hardware cannot be used and is useless.

Research the overarching framework associated with avionics design for certification.

(link 3)

The Overarching Properties are intended to define a sufficient set of properties for making approval decisions.

This document is written in a conversational style, unlike the more formal styles usually employed in standards and guidance documents. Two reasons motivate the choice. One, a conversational style is more likely to facilitate understanding by actively engaging the reader than is a formal style. Two, using a different writing style helps emphasize the fact that the Overarching Properties approach is substantially different in at least some respects from current approaches.

ED-79 and ARP-4754 are standards in the aviation industry that offer guidance for certifying and developing aircraft systems, with a specific emphasis on safety and integration. ED-79, published by EUROCAE, is titled “Guidelines for the Certification of Aircraft Systems.” It serves as a reference document, providing recommendations on the certification processes for aircraft systems. The focus is on ensuring safety and reliability, with an emphasis on systematic hazard identification and mitigation.

ARP-4754, an Aerospace Recommended Practice by SAE International, is titled “Guidelines for Development of Civil Aircraft and Systems.” This document offers guidelines for the development of civil aircraft, emphasizing a systems engineering approach. ARP-4754 outlines processes for system-level requirements, architecture, design, verification, and validation. The primary goal is to ensure that civil aircraft and their integrated systems meet stringent safety and performance requirements throughout the entire development life cycle. Adhering to these guidelines is critical for maintaining the safety and airworthiness of aviation systems.

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