A New Kind of Modern Airmanship for Fly-by-Wire

15 April 2023

Every student pilot learns about “airmanship” – an overarching concept including aviation knowledge, situational awareness, positive control, and prudent judgement. Good airmanship can be developed through training or practical experience, and it’s relentlessly pursued by professional aviators. Increasingly, many pilots find that both over-reliance on automation and lack of automation awareness threaten to erode their operational airmanship. 

Airbus A350 XWB with Fly-by-Wire Flight ControlsMost new aircraft use fly-by-wire control systems, but pilots of these aircraft can rarely find straightforward or comprehensive information about the fly-by-wire system they are using for control. The aircraft’s fly-by-wire control system is usually oversimplified during training or not explained in an easily understood way. Although the aircraft flight manual tells pilots exactly "what" to do, questions of "how it works" and "why it's designed that way" are unresolved. The information gap about this critical aircraft system is a significant contributor to lack of automation awareness, and creates a growing aviation safety problem.Today’s professional pilots need a new kind of modern airmanship!

Gulfstream GVIII-G700 Flight Deck with Test PilotsIn the last 100+ years of powered flight, aircraft technology developed rapidly – but the basics of controlled flight are unchanged. Deflecting control surfaces still causes the same effects, because of dynamic pressure, aerodynamics, and physics. Although our aircraft designs still have similarly-named flight control surfaces (elevator, ailerons, rudder, spoilers, flaps, etc)... no longer are these control surfaces physically connected to the cockpit. Because of fly-by-wire, control surfaces can automatically move in combination with each other, achieving better efficiency, better performance, or both! 

Key Concepts for Fly-by-Wire

There are two key concepts which must be embraced to understand fly-by-wire:

First: Fly-by-wire can move differently. Because there is no longer a direct mechanical connection between the pilot and the aircraft control surfaces, the control surfaces will not always, and do not necessarily need to, move at the same rate or even in the same direction as pilot input. Fly-by-wire systems will not have constant or proportional relationships between the pilot’s inputs and resulting control surface movements. This is because of something called “Control Laws”; and also because engineers tune the aggressiveness of the responses in terms of filters, blending, and "gain".

Second: Fly-by-wire fails differently. Although mechanically jammed control surfaces are much less likely, potential hardware and software failures or design errors must be expected and mitigated by the engineers. The best way to solve these problems is with redundancy, but developers also need to have substantial flight test campaigns to look for unintended/unexpected behavior. The most critical areas for testing are when the aircraft transitions from one state (phase of flight, configuration – gear up/down, or control law), to another. These transitions can often cause software and hardware issues during development.

Modern commercial aircraft designs increasingly abandoned conventional pushrods and cables in favor of fly-by-wire architecture, simply out of competitive necessity driven by performance and safety features. While fly-by-wire has many advantages, the design considerations and performance limitations are often hidden from its most direct user – the pilots. Pilots are provided with varying degrees of technical information about their aircraft’s fly-by-wire system, depending on the operation and the aircraft manufacturer. 

FlightSafety Training Center Classroom PerspectiveTraining center presentations on fly-by-wire flight control systems are usually limited to the minimum you “need to know”, and then quickly move on to reviewing any related normal, non-normal, or abnormal procedures in the Aircraft Flight Manual (AFM). Documents such as the Aircraft Operations Manual (AOM) or Flight Crew Operations Manual (FCOM) generally don’t discuss fly-by-wire systems. If pilots are provided with a Production Aircraft Systems document, the fly-by-wire system discussion is usually limited to the same level of information provided by the training center. Professional pilots don’t need to be able to build a fly-by-wire system in their garage, but there is clearly an information gap between their training documents and the aeronautical engineering textbooks.

Understanding Fly-by-Wire

Understanding fly-by-wire concepts gives professional pilots an advantage as they apply the flight manual procedures for their aircraft. But is it possible to describe how fly-by-wire control systems work, without going into engineering details? The math to design these advanced systems may be complicated, but the concepts underlying modern aircraft fly-by-wire designs are easily described and understood. Most pilots would like to understand how fly-by-wire systems are structured – but without digging into any math or complicated diagrams!

Daedalus Aerospace developed a short course to meet this need, designed to equip both professional captains and aspiring students with an understanding of fly-by-wire systems in plain English. Although fly-by-wire flight control systems are designed by engineers, the underlying concepts can be explained without complicated logic diagrams. The course is written and presented by an experimental test pilot that contributed to the design and certification of fly-by-wire systems. It is not an engineering course, although it touches on some technical concepts. There is no math, and it will not replace your aircraft flight manual. Rather than describe a particular aircraft’s design, the course explains fundamental concepts from a pilot’s perspective, applicable to any fly-by-wire system. Topics covered in the course include:

  • What are the problems/limitations with mechanical flight control systems?
  • What are the advantages and basic design elements of Fly-by-Wire flight controls?
  • Why are four computers better than one or two?
  • What are popular control laws for designers?
  • What sensors are needed, and why?
  • How do flight control designers mitigate risk?

Modern Airmanship

Fly-by-wire designs tend to be highly reliable, but pilots must be prepared to handle any contingency. The best pilots want to go beyond the minimum required knowledge. They want to understand how their specific aircraft works, both to get optimum performance and also to be prepared for when components inevitably malfunction. The “Introduction to Fly-by-Wire” course from Daedalus Aerospace helps build a new kind of modern airmanship. Including graphics, videos, a free eBook, and interactive instructional materials; this short course describes fundamentals of aircraft fly-by-wire designs in an approachable way for professional pilots, aviation enthusiasts, and aspiring aerospace engineers. This course fills the fly-by-wire knowledge gap with a manufacturer-agnostic, high-level overview of the basic fly-by-wire system design considerations. Daedalus Aerospace gives you what other training can’t: fly-by-wire training from the same people who help to develop this technology. Take the next step to develop your modern airmanship with the “Introduction to Fly-by-Wire Flight Controls” course!

About the Author

Instructor Test Pilot

David Kern

David Kern is a graduate of the US Air Force Test Pilot School, with experience planning and flying hundreds of flight test missions for civil aircraft certification and military projects. In 2011, he was the USAF F-16 project test pilot for the Collier Trophy-winning Automatic Ground Collision Avoidance System (AGCAS). In his USAF career, he served as Instructor Test Pilot and Director of Operations at the USAF Test Pilot School, teaching all parts of the multi-engine and fighter curricula. David is an Associate Fellow with the Society of Experimental Test Pilots, Member of the Society of Flight Test Engineers, and serves as a flight test pilot for the Aircraft Certification Service with the Federal Aviation Administration. He holds a Master of Science in Flight Test Engineering and B.Sci. Electrical Engineering with a minor in Mathematics. He also holds an Airline Transport Pilot certificate with seven type ratings, is an active Certified Flight Instructor for instrument conditions, and has logged piloting time at the flight controls of over 80 different types of aircraft. His publications include "Flight Test Techniques for Active Electronically Scanned Array (AESA) Radar", "Accelerated Development of Flight Tested Sensors and Systems", and “Introduction to Fly-by-Wire Flight Control Systems: The professional pilot’s guide to understanding modern aircraft controls.”