Originally Posted by
squawk
1) What kind of computation does an FMC do? Do these tasks vary significantly between different (sub)-types of aircraft, families of aircraft, or even individual airlines? I assume there are lots of 'keeping the plane running' tasks that are involved – e.g. balancing fuel between tanks, handling conflicts between information from redundant sets of equipment, etc.
2) What kind of hardware and software do FMCs run? Presumably they need to be specially hardened and certified, but how 'current' are they, given the long lead time between designing and certifying the plane, it entering service, and the lifetime of the airframe itself?
3) How involved is BA/BA engineering in the specification of such FMCs, or is it 'standard' from the aircraft manufacturer (linked to Q1 above).
1.) Generically the FMC/Flight Management System started out life to assist with navigation of the aircraft. Years and years ago, the aircraft was navigated from radio waypoint to radio waypoint using fairly simple instruments in the cockpit. As inertial navigation systems become more sophisticated, aircraft could be navigated to predetermined latitude/longitude, aka waypoints. It then snowballed thereafter - lists of waypoints could be entered, diversions, lists of nearest airports, altitude constraints, standard departure/approach routes, company routes etc. Along with this functions got added on to calculate performance airspeeds (take-off/rotate, climb, cruise, landing speeds), engine power ratings, aircraft weight and balance management, etc. So to answer your question, it typically handles everything related to route planning, navigation, and aircraft performance management. Years ago the FMS was a standalone box (which connected to lots of other aircraft sensors and systems), whereas with modern aircraft it's much more of a central computer/app type architecture (non-federated).
2.) The whole thing is highly regulated - but what you tend to find is a PowerPC chipset or similar surrounded by some very high integrity hardware (qualified to extremes of pressure, temperature, vibration, power supply spikes/poor quality). The software level tends to run on something like Ada. The software validation process is huuuuuge, and is highly fault tolerant/resistant. It's quite variable, but you're probably looking at a 3 to 5 year development cycle from key requirements to certified system. The hardware development tends to be fairly incremental, with the clever work happening at the software level.
3.) This is really variable! Tends to be a given that the hardware is identical, but the changes occur at the software level. Some airlines are content to pick from a menu - so typically Boeing/Airbus et al will have some baseline packages available. More mature airlines will see value in specifying particular features that make their day-to-day business more efficient or safer. Truly bespoke features are v. v. expensive, so it tends to come down far more to user interface, menu structures, style of presentation etc. So for example, I used to work in business jets, and one particular customer wanted some features very specific to operations in to and out of Aspen. Rather expensive, but it gave them improved levels of safety and ability to get in during bad weather, for which they had a market edge.