I don’t think the good old days were that good. I can still remember the sheer bloody effort spend learning about the errors and limitations of instruments. Just like a politician, not one of the wretched things ever told the truth and with the slightest provocation they told huge great porkies. That was if you could actually read the buggers. The “three pointer altimeter,” monochromatic dials, pointers the same colour as the displacement indicators and so on. They were difficult to read during day time. Reading them at dusk was virtually impossible as the instrument lighting was not bright enough. At night it wasn’t much better. I still remember my fingers being burnt by post lights when you had to swap them about during an approach at night in an F27. And then there’s the fuel trim indicators – a gauge with an arc length of something like 2.5 inches where you were expected to set something like 78.9%. And this little gauge was there to help you control up to 30% on the engine’s fuel flow. As for backup, you had to remember which engine the standby horizon was connected to. From what I can understand, this aircraft was typical for the period.
Then there’s the last generation of steam instruments, the ones fitted to jet transport aircraft just before the world went glass. I’m talking here about aircraft manufactured up to about 25 years ago. The legibility of these instruments was excellent as was their reliability if you compared them with previous generations. But they suffered from being incredibly complicated, very expensive and by modern standards inaccurate. First generation “glass” left these things for dust in the reliability stakes. Unfortunately, this stuff was fitted without the background knowledge we had with old fashioned steam instruments. We were told that these thing were accurate – even when the system knew it self that it wasn’t. The “magenta” line was always (and still is) a few pixels wide when these systems know that they may have an error of up to two miles. We weren’t taught how these things could be miss-programmed, could suffer from interference or in many cases even where the data came from. Surprisingly the data often came from the same “black boxes” that supplied the previous generation of steam instruments. And I remember being told that I didn’t have enough experience to fly an “all glass aircraft.” There were even more idiots around in training during this period.
Virtually all modern FBW digital aircraft now have solid-state transducers and a high degree of redundancy. They are reliable. But the worst case scenarios are not practiced with enough regularity. My own aircraft, one of the cheapest jets money can buy, still leaves you with a flight path vector if all ADC data are removed. If the screens capable of supplying that information go blank, I still have a battery driven attitude indicator. The engine data is capable of being displayed on three screens. Overall, I’d suggest that following a catastrophic instrumentation failure, you still have a flyable aircraft – but only if you were trained to use it. And I tell you what, we are. It is included in our type training and elements are practiced during bi-annual recurrent training.
Regarding modern flight decks, we face two big problems. Firstly is “mode awareness” – I have lost count of the amount of times I personally have been caught by my aircraft doing something I didn’t want it to do. Either I trap by error by noticing the untoward behaviour or my ever vigilant, normally thirty years younger colleague spots it. This is only possible in system where both seats respect each other as equals when it comes to flying. The fact that most F/O’s can fly better than me is not significant. The second is receiving training that exposes you mode and system failure at critical times and how this physically interacts with the aircraft. This has to be planned by imaginative trainers and be very type specific. I don’t think every airline does this nor are they aware of some of the nasty little surprises hidden inside the aircraft they every day. A crew of a 737 at BOH a few years ago received several nasty shocks as did the poor sods at AMS.
Solution? A free flow of information and training so that we can a) Recognise the early onset of source data supply problems, if any and b) Have a rapidly executable plan that will always allow an immediate escape using data that is reliable.
PM
Last edited by Piltdown Man; 8th Feb 2011 at 16:48.