Week 4

Doppler effect

The Doppler effect, also known as Doppler shift, is a phenomenon that occurs when there is a change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. This effect is commonly observed in sound waves, light waves, and other types of waves.

The most familiar example of the Doppler effect is related to sound waves, such as the change in pitch of a siren as it approaches and then moves away from an observer.

Free space path lost

The term you are referring to is likely “Free Space Path Loss” (FSPL), not “Free space path lost.” Free Space Path Loss is a concept in telecommunications and radio frequency engineering, describing the attenuation or reduction in signal strength that occurs as electromagnetic waves propagate through free space (a vacuum or air) without any obstacles or reflecting surfaces.

d is the distance between the transmitter and receiver (in meters),

f is the frequency of the signal (in hertz),

c is the speed of light in a vacuum (approximately 3×10^8 per second)

Phase noise

Phase noise is a phenomenon in signal processing and communications that refers to the short-term, random fluctuations in the phase of a signal. In simpler terms, it’s the instability or jitter in the timing of a signal. This phenomenon can affect the accuracy and precision of various systems, particularly in high-frequency communication systems, oscillators, and other applications where precise timing is crucial. Phase noise originates from imperfections and random variations in the components of electronic devices, such as oscillators and amplifiers.  Variations can lead to fluctuations In phase of the signal causing instability. In summary, phase noise is a critical consideration in systems where precise timing and stable frequency are essential. Engineers work to minimize phase noise to ensure the reliable performance of communication systems, especially those operating at higher frequencies or requiring high precision.


Fault Detection, Isolation, and Recovery (FDIR) is a systematic approach employed in intricate systems, especially in sectors like aerospace, automotive, and other safety-critical domains. The primary goal of FDIR is to ensure the resilience and dependability of a system by promptly identifying faults, pinpointing their origins, isolating the affected components or subsystems, and executing corrective measures or recovery strategies to sustain or restore the system’s functionality.

Breaking down the essential components of FDIR:

  1. Fault Detection (FD):
    • Objective: Recognizing abnormal conditions or faults within the system.
    • Methods: Monitoring diverse parameters, sensors, and system states to identify deviations from expected behavior.
    • Techniques: Employing redundancy, statistical approaches, or model-based methods to detect anomalies by comparing actual system outputs with anticipated values.
  2. Fault Isolation (FI):
    • Objective: Identifying the root cause and isolating the faulty component or subsystem linked to the detected fault.
    • Methods: Analysing system behaviour and utilizing diagnostic algorithms to narrow down potential fault locations.
    • Techniques: Deploying redundancy, analysing sensor data, or utilizing model-based reasoning to ascertain the source of the fault.
  3. Fault Recovery (FR):
    • Objective: Applying corrective measures to alleviate the effects of the fault or restore the system to regular operation.
    • Methods: Implementing predefined recovery strategies or reconfiguring the system to bypass or substitute the faulty components.
    • Techniques: Leveraging backup systems, switching to redundant components, adjusting control parameters, or restarting subsystems to recover from the fault.

The FDIR process operates continuously and iteratively, as faults can manifest at any point during system operation. The successful execution of FDIR necessitates a comprehensive comprehension of the system’s behaviour, potential fault scenarios, and the development of robust algorithms for fault detection, isolation, and recovery.


Full Authority Digital Engine Control (FADEC) stands as a cutting-edge electronic system employed in contemporary aircraft to govern and manage the functioning of gas turbine engines. This technology supersedes traditional mechanical and hydromechanical control systems, introducing a fully digital and computerized interface that ensures precise and optimal control of the engine’s performance. Let’s delve into the key facets of FADEC:

  1. Objective:
    • Enhanced Control: FADEC is designed to provide meticulous and optimal control of the aircraft’s engines throughout all flight phases, from ignition to descent.
    • Efficiency: By continuously monitoring and adjusting engine parameters, FADEC aids in optimizing fuel efficiency, overall performance, and emission levels.
  2. Components:
    • Electronic Control Unit (ECU): Serving as the central component of the FADEC system, the ECU is a computer responsible for processing data from various sensors and issuing commands to engine actuators accordingly.
    • Sensors: FADEC relies on an array of sensors to gather data on factors like engine temperature, pressure, airflow, and RPM (Revolution Per Minute).
    • Actuators: These components, such as fuel injectors, variable stator vanes, and variable nozzle systems, respond to commands from the ECU to adjust engine parameters.
  3. Modes of Operation:
    • Normal Mode: In standard operation, FADEC continuously fine-tunes engine parameters to maintain optimal performance and efficiency.
    • Alternate Mode: In the event of a FADEC system malfunction, an alternate mode may be available, enabling the pilot to manually control the engine using traditional backup systems.
  4. Advantages of FADEC:
    • Precision and Optimization: FADEC ensures precise control over the engine, optimizing both performance and fuel efficiency.
    • Reduced Pilot Workload: With automated control, pilots can focus on other aspects of flying, as FADEC manages the engine parameters.
    • Improved Reliability: FADEC systems are engineered for high reliability, featuring self-monitoring capabilities that can detect and respond to faults.
  5. Applications:
    • Aerospace: FADEC is widely utilized in commercial and military aircraft, helicopters, and unmanned aerial vehicles (UAVs).
    • Marine: FADEC technology has also found applications in marine propulsion systems for ships.
  6. Safety Features:
    • Redundancy: FADEC systems often incorporate redundancy measures to ensure continuous operation even in the face of component failures.
    • Built-in Diagnostics: FADEC continuously monitors its own performance and can provide real-time diagnostics to the flight crew.

In summary, Full Authority Digital Engine Control (FADEC) signifies a substantial advancement in engine control technology, introducing improved efficiency, reliability, and safety to aviation and other related fields. It exemplifies the integration of digital electronics to elevate the performance and control of intricate systems

The benefits of implementing these two techniques increases efficiency massively, due to an internal system being integrated will help reduce time having to find the problem manually.

In both cases, the integration of hardware and software is crucial for the effective functioning of these systems. The hardware collects data, processes information, and executes commands, while the software provides the intelligence and decision-making capabilities to achieve the desired control, fault detection, isolation, and recovery functionalities.

It’s important to note that the specific implementation details can vary depending on the application and the type of system. Aircraft engines commonly utilize FADEC for precise control, while FDIR systems are prevalent in safety-critical applications where fault detection and recovery are paramount, such as aerospace, automotive, and industrial control systems.

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