The Dangers of Automation in Airliners by Jack J Hersch

Author:Jack J Hersch
Language: eng
Format: epub, pdf
Tags: TRANSPORTATION / Aviation / Commercial
Publisher: Air World
Published: 2020-12-30T00:00:00+00:00

Chapter 33

Guardrails

Bernard Ziegler’s contribution to the A320 went beyond its fly-by-wire skeleton. He also espoused a first-of-its-kind computerized monitoring system that would oversee every control input by the A320’s pilots. Using the computers embedded within the plane’s wiring, every move pilots made would be supervised by software. If it caught them doing something dangerous to the plane and passengers, like banking too steeply, it would stop them. That is known as flight envelope protection. Ziegler called it ‘the biggest improvement in flight safety in history.’

That might not be hyperbole.

The flight envelope is the complete range of maneuvers a plane can perform without stalling or experiencing structural failure. By definition, a plane leaving its flight envelope is at least partially out of control. Military and aerobatics pilots might depart their flight envelope during certain maneuvers and are trained to get it back. But in commercial aviation, an airliner departing its flight envelope is unquestionably in trouble.

Airbus’s flight envelope protection software was, in a sense, a pilot babysitter.

This was revolutionary and breathtaking at the same time: it had never been tried before, and it changed the rules for pilots. No longer would they have the final word aboard their plane – computers would. Bernard Ziegler and Airbus could not be sure how pilots would react to something so radically different from what they were accustomed to – not having absolute authority over their aircraft. What if they needed to fly aggressively to avoid a mid-air collision? Would the system prevent them from turning sharply enough, or climbing or descending steeply enough?

Ziegler again replied in the negative. But he is biased. This time the real answer depended on who you asked, and it remains a point of contention today, more than thirty years after its introduction. Boeing eventually joined Airbus in producing a fly-by-wire commercial jet, the widebody Boeing 777, and installing computer software with flight envelope protection monitoring that airplane’s every action in the sky. The US company also switched to all-glass cockpits, though instead of sidesticks it opted to leave in place the yoke-and-column configuration its pilots had been using since the manufacturer’s earliest days.

The two companies also chose entirely different philosophies of how to implement flight envelope protection.

Every Airbus plane from the A320 on has what is called hard protection. Its onboard computers are guided by narrowly defined flight control laws dictating what they will, and will not, allow the pilot to do. For instance, the laws stop the pilot from taking the plane beyond a maximum angle of bank, and past a maximum number of degrees pitch nose-up or nose-down. If the pilot tries banking further or raising the nose higher than allowed, the plane simply won’t go there.

Ziegler compared it to guardrails on a sharp road curve. ‘The guardrail is not there to help you negotiate the curve,’ he said, ‘but rather to prevent your car from leaving the road should you not succeed in completing the curve.’

Like a car on that curve, within those guardrails Ziegler and Airbus let pilots ask anything of their plane.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.