Electronic Instrumentation — Page 540, Lesson 645

I want to walk you through the world of electronic instrumentation for engine and airframe systems control. This is where we move away from the traditional round dials and gauges and into the world of screens — Cathode Ray Tube, or CRT, and LCD type displays. These have become a standard feature on many aircraft types, just as they have in flight instrument systems. The display units you'll see form part of two principal systems. The first is the Engine Indicating and Crew Alerting System, which we call EICAS. The second is the Electronic Centralized Aircraft Monitoring system, which we call ECAM. These two systems were first introduced on specific aircraft: EICAS on the Boeing 757 and 767, and ECAM on the Airbus A310. Now, when these systems were first introduced, there were differing views on how to approach things like flight deck layouts and the crews' controlling functions. There was debate about how much normal, alerting, and warning information should be displayed. And in particular, there was a key question: should engine operating data be displayed for the whole of a flight, or only at various phases? Let's look at how each system answered that question. In respect of EICAS, engine operating data is displayed on screens, which eliminates the need for traditional instruments. So on the Boeing 757 and 767, you don't have the old round engine gauges — it's all on the screen. But here's an important point: this data, as well as data relevant to other systems, is not necessarily always on display. However, in the event of malfunctions occurring at any time, the flight crew's attention is drawn to them by an automatic display of messages in the appropriate colours. So the system watches everything, and when something goes wrong, it automatically brings up a message in a colour that signals the severity. The ECAM system, on the other hand, takes a different approach. It displays systems' operation in checklist and schematic form. This was a concept based on the view that engine data needed to be displayed during the whole of a flight. Because of that philosophy, traditional instruments were retained in the Airbus A310. So even though ECAM gives you checklists and schematics, the A310 kept its conventional engine gauges as well. It's interesting to note, however, that in subsequent types produced by this manufacturer — for example, the A320 — the ECAM system was developed to include more. The excerpt cuts off there, but you can see the direction: ECAM evolved as the manufacturer refined the concept. Let me make sure you've got the key contrasts clear. EICAS: engine data on screens, no traditional instruments, data not always displayed but malfunctions trigger automatic coloured messages. ECAM: checklist and schematic displays, based on the view that engine data should be shown for the whole flight, so traditional instruments were kept in the A310. And the two systems came from different manufacturers — Boeing for EICAS, Airbus for ECAM. Now, let's look at some of the hardware behind these systems. I have a figure here showing a capacitance tank unit — that's . This is the kind of sensor that measures fuel quantity in the tanks. It works on the principle that the capacitance of the unit changes as the fuel level changes, and that change is converted into a reading. Then there's , which shows the pointer in the fuel quantity system. The key point here is that this system measures fuel by volume — and the question is what that reading is directly related to. That's a fundamental distinction you need to understand: volume versus mass, because fuel density changes with temperature. And finally, shows a typical fuel flowmeter with a remote signal transmission system. This is how the flow of fuel to the engines is measured and transmitted to the display. So to tie it all together: EICAS and ECAM are the two big display systems, each with its own philosophy about when to show engine data. And behind those displays, you have sensors like the capacitance tank unit for fuel quantity and the fuel flowmeter for fuel flow. These are the building blocks of modern electronic instrumentation.