DOSSIER

 

The Bridge: A Systems View

 

You’re an experienced airline pilot, comfortable with the plane’s equipment and procedures. Takeoff went smoothly, and your passengers are settling in. Without warning, the plane nosedives. You follow the procedures, try to level out, but the control system fights you.


by Nic Gardner MNI, Nautical Institute Automation Technical Advisory Group

You override the control system, but it turns back on a few seconds later. In desperation, you leave your co-pilot to try to fly the plane while you read the manual, hoping to find some way to disconnect the faulty system. Just 13 minutes after takeoff, you, your co-pilot, your plane, and 157 passengers plunge into the ocean. No-one survives. This was the reality for the pilots of Lion Air 610 in 2018. Just a few months later, the story repeated with Ethiopian Airlines flight ET602, another Boeing 737 Max, which survived just 12 minutes after takeoff. The problem? A faulty sensor, and a secret safety system.

 

What is a system?

Systems rule our lives: safety management systems, human bodily systems, propulsion and sewage systems, personal computer systems and more. The system on Lion Air 610 is actually a system intended to improve safety, but it caused a disaster. 

Well-designed systems make all our lives considerably easier, and the ship’s bridge is no exception. But what is a system?

For our purposes, a system is a set of components that work together to turn inputs into outputs via processes.

 

A simple system

In a closed system such as a cup of hot chocolate with a lid, mass cannot enter or leave the system, even if energy (heat) can. In contrast, an open system takes inputs from outside the system, then turns them into outputs that return outside the system. Most systems are open systems.

Take your body as an example: you input food and drink. Your digestive system processes the food, and outputs energy and waste products. The energy enters other systems as an input, and is processed, along with other inputs, to create other outputs and – if it’s working properly – keep you alive. 

As in so many systems, one of the outputs of the digestive system — energy — becomes an input to other systems. In turn, these other systems process the energy – their input – to create more outputs such as movement and breathing. Your body is a system of systems.

When you’re injured, you expect the medical professionals to consider your body’s systems as a whole, not just treat the obvious symptom. For example, if you have a terrible headache, painkillers might help; however, if someone doesn’t look more carefully at the system as a whole and address the twistlock embedded in your skull, it will end badly for you.


Why should you care? 

But what does this have to do with a ship’s bridge? Actually, quite a lot. How many bridge watchkeepers have complained because the same alarm goes off every few minutes? Like the headache above, the alarm is the symptom, not the problem. If you silence the alarm without fixing the problem, of course it will keep going off. But to fix it, you must understand what the alarm is telling you: you have to understand the system, including its inputs, processes, and outputs.

 

 

 

  LMB-BML 2007 Webmaster & designer: Cmdt. André Jehaes - email andre.jehaes@lmb-bml.be