What is the difference between a PFD and an MFD?

The Primary Flight Display (PFD) presents the essential flight parameters a pilot needs continuously — attitude, airspeed, altitude, heading, and vertical speed — replacing the traditional "six-pack" of round-dial instruments in one integrated display. The Multi-Function Display (MFD) is a shared, reconfigurable screen that shows navigation maps, weather radar, engine data, or system synoptic pages depending on what the pilot selects, letting one physical display serve many roles.

What does a flight management system actually do?

A flight management system (FMS) combines a navigation database, a performance model of the aircraft, and multiple sensor inputs to automatically compute the optimal route, altitude, and speed for a flight, then guides the autopilot and autothrottle to fly it. It manages lateral navigation (LNAV) along programmed waypoints and vertical navigation (VNAV) through climb, cruise, and descent profiles, continuously updating position from GPS and other navigation sensors.

What are CNS systems in aviation?

CNS stands for Communication, Navigation, and Surveillance — the three functional categories of avionics that let aircraft talk to air traffic control and each other, determine their position, and be seen by others. Communication includes VHF, HF, and datalink; navigation includes GPS/GNSS, VOR, DME, and ILS; surveillance includes the transponder, ADS-B, and TCAS. Together they form the technical backbone of the air traffic management system.

Why do avionics systems use so much redundancy?

Because a failure of a flight-critical system in flight can be catastrophic and there is no roadside to pull over to, avionics architectures use multiple redundant computers, sensors, and power sources so that no single failure — or even a small combination of failures — can cause loss of a critical function. Higher criticality functions get more redundancy: flight control computers on fly-by-wire airliners are commonly triplicated or quadruplicated, often using dissimilar hardware and software to guard against common-mode faults.

What is DO-178C and why does it matter for avionics software?

DO-178C is the internationally recognized standard for certifying the software inside airborne systems. It assigns each software component a Design Assurance Level (DAL) from A (catastrophic failure condition) to E (no safety effect) based on the severity of what happens if it fails, and mandates increasingly rigorous requirements, traceability, and testing as the level gets more critical. Nearly every line of code in an avionics box that can affect flight safety is developed and verified under this framework.

Engineering·13 min read·July 12, 2026

🖥️ Avionics Systems Overview

An overview of aircraft avionics — flight instruments, autopilot and flight management systems, communication, navigation and surveillance (CNS), glass cockpit architecture, and redundancy philosophy.

📖Aerospace Engineering Handbook (Full Access)

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Avionics: The Aircraft's Nervous System

Avionics — the electronic systems used on aircraft — have grown from a handful of simple dial instruments into the majority of a modern aircraft's cost and complexity. They sense the aircraft's state, help the crew navigate and communicate, automate routine flying tasks, and increasingly make decisions that once required a human pilot's judgment. Understanding how these systems are organized is essential to understanding the modern flight deck.

Topics covered

avionicsflight instrumentsautopilotflight management systemFMSCNS systemsglass cockpitADS-BTCASARINC 429redundancyDO-178Cprimary flight displayintegrated modular avionics