Electronics Guide

Flight Control Systems

Flight control systems translate pilot inputs into aircraft movements. Traditional aircraft used direct mechanical linkages between cockpit controls and flight surfaces, but modern aircraft increasingly employ fly-by-wire systems where electronic signals control hydraulic or electric actuators. Fly-by-wire offers numerous advantages including reduced weight, improved handling characteristics through electronic stability augmentation, envelope protection to prevent dangerous flight conditions, and the ability to optimize aircraft design without constraints imposed by mechanical control runs.

Primary flight control computers process pilot inputs, sensor data, and aircraft state information to generate appropriate commands to control surface actuators. These systems incorporate multiple redundant channels with dissimilar hardware and software to ensure continued operation even in the presence of failures. Flight control laws programmed into these computers provide the desired handling qualities, stability augmentation, and flight envelope protection that characterize each aircraft type.

Navigation Systems

Navigation systems enable aircraft to determine position, plan routes, and fly precisely to destinations. Modern navigation relies heavily on Global Navigation Satellite Systems (GNSS), primarily GPS, which provides position accuracy within meters anywhere on Earth. Inertial navigation systems using accelerometers and gyroscopes provide continuous position updates independent of external signals, essential for operations where satellite signals may be unavailable or jammed.

Area navigation (RNAV) and required navigation performance (RNP) systems combine multiple navigation sources to enable aircraft to fly any desired path with defined accuracy. These capabilities support performance-based navigation procedures that improve airspace utilization and enable curved approaches that reduce noise and fuel consumption. Flight management systems integrate navigation with performance calculations to optimize routes, speeds, and altitudes throughout the flight.

Communication Systems

Aviation communication systems enable voice and data exchange between aircraft and ground facilities. VHF radio remains the primary voice communication medium for most aviation operations, with HF radio providing long-range communication over oceanic and remote areas. Satellite communication systems offer global coverage for voice, data, and internet connectivity on modern aircraft.

Data link communications have become increasingly important, enabling digital exchange of clearances, weather information, and flight plan updates between aircraft and air traffic control. Controller-pilot data link communications (CPDLC) reduce voice channel congestion and improve communication accuracy. Aircraft Communications Addressing and Reporting System (ACARS) provides automated data exchange for operational and maintenance information.

Display Systems

Modern cockpits feature glass cockpit displays that have replaced traditional analog instruments with digital screens presenting flight information in integrated formats. Primary flight displays (PFD) show essential flight instruments including attitude, airspeed, altitude, and heading in a unified presentation. Navigation displays (ND) provide moving map presentations with route, weather, and traffic information. Multifunction displays (MFD) present system status, checklists, and additional information as needed.

Head-up displays (HUD) project flight information onto a transparent screen in the pilot's forward field of view, enabling continued outside visual reference while monitoring instruments. Enhanced vision systems (EVS) use infrared sensors to penetrate darkness and obscured conditions, presenting imagery on the HUD to improve situational awareness during approach and landing. Synthetic vision systems (SVS) generate computer-rendered terrain displays using onboard databases.

Traffic Collision Avoidance System

The Traffic Collision Avoidance System (TCAS) provides the last line of defense against mid-air collisions. By interrogating transponders on nearby aircraft, TCAS determines their range, altitude, and closure rate. When collision threats are detected, TCAS provides traffic advisories alerting pilots to nearby aircraft and, if necessary, resolution advisories commanding specific vertical maneuvers to ensure separation. TCAS coordination protocols ensure that conflicting aircraft receive complementary commands.

Ground Proximity Warning System

Ground Proximity Warning Systems (GPWS) and Enhanced Ground Proximity Warning Systems (EGPWS) protect against controlled flight into terrain, historically a leading cause of aviation accidents. These systems use radar altimeters to measure height above terrain, combined with aircraft state data and terrain databases, to detect dangerous approach conditions. Warnings include excessive descent rate, terrain closure, altitude loss after takeoff, unsafe terrain clearance during approach, and excessive deviation below the glideslope.

Weather Radar

Airborne weather radar enables pilots to detect and avoid hazardous weather. X-band weather radars transmit pulses and analyze returns to display precipitation intensity on cockpit displays. Modern systems include turbulence detection capabilities that identify dangerous clear air turbulence by detecting wind shear patterns. Predictive windshear systems provide warnings of dangerous low-altitude windshear conditions during takeoff and landing.

Flight Data and Voice Recorders

Flight data recorders (FDR) and cockpit voice recorders (CVR), collectively known as black boxes, capture flight parameters and cockpit audio for accident investigation. Modern FDRs record hundreds of parameters continuously, while CVRs capture crew conversations and cockpit sounds. These systems must survive extreme conditions including impact forces, fire, and deep water immersion. New technologies include deployable recorders that automatically eject and transmit location during accidents.

Avionics Architecture

Modern avionics employ federated or integrated modular avionics (IMA) architectures. Traditional federated architectures use dedicated computers for each function, connected through standardized data buses such as ARINC 429 or MIL-STD-1553. While proven and well-understood, federated architectures result in multiple boxes with duplicated processing and memory resources. IMA architectures consolidate functions onto shared computing platforms, reducing weight, power consumption, and cost while improving flexibility.

The ARINC 653 standard defines partitioning requirements for IMA systems, ensuring that functions hosted on shared platforms cannot interfere with each other. This partitioning enables certification of individual applications independently, simplifying the certification process for complex integrated systems. Modern commercial aircraft like the Boeing 787 and Airbus A350 employ IMA extensively.

Data Bus Standards

Avionics data buses enable communication between system components. ARINC 429, the dominant civil aviation standard, uses unidirectional point-to-point links with simple protocols but limited bandwidth. Military aircraft typically use MIL-STD-1553, a bidirectional multiplex data bus that supports command/response protocols. High-bandwidth applications increasingly use ARINC 664 (AFDX), based on Ethernet technology, which provides deterministic timing and redundancy for safety-critical applications.

Power Systems

Avionics require reliable, clean electrical power. Traditional aircraft use 28V DC and 115V 400Hz AC power systems, with more electric aircraft adopting 270V DC for high-power systems. Power quality is critical since voltage transients, frequency variations, and electromagnetic interference can disrupt sensitive electronics. Avionics incorporate extensive filtering and protection circuits, while aircraft electrical systems include multiple generators, batteries, and distribution paths to ensure continued power availability.

Safety Certification

Avionics must be certified by aviation authorities before installation in aircraft. In the United States, the Federal Aviation Administration (FAA) oversees certification, while the European Union Aviation Safety Agency (EASA) performs this role in Europe. Certification demonstrates that systems meet applicable airworthiness requirements and will perform their intended functions safely throughout the aircraft's operational life.

Software certification follows DO-178C, which defines development processes based on the software's criticality level. Hardware development follows DO-254 for complex electronic hardware. These standards do not mandate specific design approaches but require documented, traceable development processes with verification activities appropriate to the design assurance level. Level A, the highest criticality, requires the most rigorous processes including complete structural coverage testing.

Environmental Standards

RTCA DO-160 defines environmental testing requirements for airborne equipment, covering temperature, altitude, vibration, humidity, electromagnetic interference, and numerous other conditions. Equipment must demonstrate acceptable performance across the environmental conditions it will encounter during normal operations and specified abnormal conditions. Military avionics follow MIL-STD-810 for environmental testing and MIL-STD-461 for electromagnetic compatibility.