AVIONICS Avionics System Ø AVIation electr ONICS

AVIONICS

Avionics System Ø AVIation electr. ONICS. Ø Electronics has been introduced in Aviation during World War II. Ø Avionics are the electronic systems used on aircraft, artificial satellites, and spacecraft. (Wikipedia) Ø Avionic System – Any system in an aircraft which is dependent on electronics for its operation. Ø Electro-mechanical elements – FBW.

FBW Flight Control System Basic components of a FBW flight control system

Avionics Industry Ø The avionics industry is a major multi-billion dollar industry world-wide. Ø Avionics equipment on a modern military or civil aircraft can account for around 30% of the total cost of the aircraft. Ø 40% in the case of a helicopter and 75% of the total cost in the case of an airborne early warning aircraft (AWACS). Ø Modern general aviation aircraft also have a significant avionics content – colour head down displays, GPS satellite navigation systems, radio communications equipment.

Need for Avionics and its major drivers Ø Avionic systems are essential to enable the flight crew to carry out the aircraft mission safely and efficiently. Ø A major driver in the development and introduction of avionic systems has been the need to meet the mission requirements with the minimum flight crew. Ø Other very important drivers for avionic systems are increased safety, air traffic control requirements, all weather operation, reduction in fuel consumption, improved aircraft performance and control and handling and reduction in maintenance costs.

Typical Avionics Systems Also Includes ATC transponder System, GPWS, TCAS

Display Systems Ø It provides the visual interface between the pilot and the aircraft systems – HUD, HMD, HDD. Ø HUD and HMD can project the display information into the pilot’s field of view so that the pilot can be head up and can concentrate on the outside world. HUD can also display a FLIR (Forward Looking Infrared) video picture. Ø The HMD enables the pilot to be presented with information while looking in any direction, as opposed to the limited forward field of view of the HUD. Ø Multi-function colour displays (HDD) provide the primary flight displays (PFDs) of height, airspeed, Mach number, vertical speed, artificial horizon, pitch angle, bank angle and heading, velocity vector and also engine data.

Display Systems – HUD Images

Display Systems – HMD Images

Display Systems – Primary Flight Display

Display Systems – HDD monitor HDD color CRT

Communication Systems Ø Need for reliable two way communication between the ground bases and the aircraft or between aircraft. Ø Essential for air traffic control. Ø The first avionic system – radio transmitter and receiver equipment. Ø Long range communication – HF (2– 30 MHz). Ø Medium range communication – VHF (30– 100 MHz), UHF (250– 400 MHz) – line of sight propagation systems. Ø Satellite communications (SATCOM) – World wide communication.

Aircraft State Sensor Systems Ø Air data systems and the inertial sensor systems. Ø Air Data Systems provide accurate information on the air data quantities (the altitude, calibrated airspeed, vertical speed, true airspeed, Mach number, etc). This information is essential for the control and navigation of the aircraft. Ø The Inertial Sensor Systems provide the information on aircraft attitude and the direction in which it is heading which is essential information for the pilot in executing a manoeuvre or flying in conditions of poor visibility, flying in clouds or at night. Ø Inertial Sensors – Gyroscopes (measures angular rotation) and Accelerometers (measures linear acceleration). Ø Attitude and Heading Reference System (AHRS).

Navigation Systems Ø Navigation – determination of position and velocity of a vehicle with respect to a reference. Ø Dead reckoning navigation – Inertial Navigation, Doppler Navigation. Ø Radio Navigation – VOR, DME, ADF, LORAN, etc. Ø Satellite Navigation – GPS, GLONASS. Ø Approach guidance – Instrument Landing System, Microwave Landing System.

Task Automation Systems Ø These comprise the systems which reduce the crew workload and enable minimum crew operation by automating and managing as many tasks as appropriate so that the crew role is a supervisory management one. Ø Navigation Management – It comprises the operation of all the radio navigation aid systems and the combination of the data from all the navigation sources to provide the best possible estimate of the aircraft position, ground speed. Ø Autopilot and Flight Management System (FMS) – grouped together.

Flight Management System Ø Flight planning. Ø Navigation management. Ø Engine control to maintain the planned speed or Mach number. Ø Control of the aircraft flight path to follow the optimised planned route. Ø Control of the vertical flight profile. Ø Ensuring the aircraft is at the planned 3 D position at the planned time slot; often referred to as 4 D navigation. This is very important for air traffic control. Ø Flight envelope monitoring. Ø Minimising fuel consumption.

Engine Control and Management System Ø It carry out the task of control and the efficient management and monitoring of the engines. Ø Engine control electronics is physically mounted on the engine. Modern jet engines have a full authority digital engine control system (FADEC). Ø FADEC automatically controls the flow of fuel to the engine combustion chambers by the fuel control unit so as to provide a closed-loop control of engine thrust in response to the throttle command. Ø The control system ensures the engine limits in terms of temperatures, engine speeds and accelerations are not exceeded and the engine responds in an optimum manner to the throttle command.

House Keeping Management System Ø Fuel management – This embraces fuel flow and fuel quantity measurement and control of fuel transfer from the appropriate fuel tanks to minimise changes in the aircraft trim. Ø Electrical power supply system management. Ø Hydraulic power supply system management. Ø Cabin/cockpit pressurization systems. Ø Environmental control system. Ø Warning systems. Ø Maintenance and monitoring systems.

Avionics System Requirements Ø Starting point for designing Avionics system is a clear understanding of the mission requirements. Figure: Requirements in system development

Avionics System Requirements Figure: Aircraft Functional Requirements

Avionics System Requirements Ø Preliminary design requirements. – What should be the size, weight, purpose, accuracy of the avionics system? – How many number of systems? – Electrical power specifications. – Environmental specifications – temperature range, acceleration, vibration, shock, electromagnetic interference (EMI)/electromagnetic compatibility (EMC). Ø Detailed design. – Selection of components/materials (software & hardware). – Development of algorithms, Simulation and Coding (software). – PCB design and Fabrication (hardware). – Mechanical design and chassis. Ø Testing, reliability check and acceptance.

Major ‘ilities’ of Avionics System Ø Capability. Ø Reliability. Ø Maintainability. Ø Availability. Ø Certificability. Ø Survivability (military). Ø Susceptibility. Ø Vulnerability.

Major ‘ilities’ of Avionics System Ø Capability – How capable is avionics system? – Can they do the job and even more? – Designer to maximize the capability of the system within the constraints that are imposed. Ø Reliability – Designer strives to make systems as reliable as possible. – High reliability = less maintenance costs. – If less reliable customer will not buy it and in terms of civil airlines the certificating agencies will not certify it. Ø Maintainability – Closely related to reliability – System must need preventive or corrective maintenance. – System can be maintained through built in testing, automated troubleshooting and easy access to hardware.

Major ‘ilities’ of Avionics System Ø Availability – Combination of reliability and maintainability. – Test runs and for sorties (military aircraft). Ø Certificability – Major area of concern for avionics in civil airlines. – Certification conducted by the regulatory agencies based on detailed, expert examination of all aspects of aircraft design and operation. – The avionics architecture should be straight forward and easily understandable. Ø Survivability – It is a function of susceptibility and vulnerability.

Major ‘ilities’ of Avionics System Ø Susceptibility – measure of probability that an aircraft will be hit by a given threat. Ø Vulnerability – measure of the probability that damage will occur if there is a hit by the threat Ø Weight and power – Minimize the weight and power requirements are the two fundamental concepts of avionics design. – So the design must be light weight and power consuming which is possible through the data bus and latest advancement of electronics devices.

Integrated Avionics Ø Need for system integration. Ø Combination of sub-systems. Ø Weapon system concept (mid 1950 s) Ø Naval strike aircraft systems. Ø Avionics architectures. (till today from early days) Ø Point-to-Point wiring. Ø Multiplexing (TDM) and Data buses.

Reference(s) (1) R. P. G. Collinson, Introduction to Avionics Systems, Third Edition, Springer Publications, 2011. (2) Cary R. Spitzer, The Avionics Handbook, CRC Press, 2001.