RAT 5
Absolutely spot on; and is true of all the magenta bug displays. Is the a/c white performance speed/hdg/alt lined up with the magenta cmd bug? Quick & easy to ascertain at a glance. In B732 I had to fly 210, 190, 170, 150kts etc for the various flap settings. Now on NG I just fly the green F bug which is high;lighted by the CMD bug. Simple easy. Am I + or - not a specific number.
Simple and easy, that is, but........
it is also a good example, how disconnected you might get. Not the numbers to be flown are remembered, but the correct composition of the display bug to bug to color to whatever. Developing trends like getting fast or slow are clouded by the perfekt working system, the autothrottle takes care of it. Actually there is no need to check it at all, as everything is fine day in and day out. You still remember the speeds it should show with different configurations? The thinking process has been replaced by limitless faith into the technical solutions implemented in those modern cockpits. That was the trap the Asiana crew ended up at last.
I sometimes wonder, why there are still switches, dials and other manual operated input devices available. Evverything goes to some input box first, before it is transfered to respective aircraft systems. When will the time come where you talk to the machine instead of making archaic manual inputs?
Back to the speed indication. There are several digital informations displayed in some analoge display form like some pressure gauges, the reason is? If the speed information would be considered as a vital information, or lets say if the autothrottle system would not jet have been invented and speeds would need to be manipulated manually, we would imho see normal analogue looking (but digital working) speed displays.
Then comes the day when the system is mishandled (Asiana) or goes on leave (AF447) to name two examples and nobody is able to mind the speed store anymore. To compare accident rates of different years and models is for no use at all, as the difference between a 1. generation 737 and a 737NG is not restricted to a different airspeed display. There are tons of other improvements leading to those low accident rates.
On the other hand the airspeed display of todays modern jets is not unsafe in itself, if training and proficiency reflect the inherent importance of monitoring the speed and enforce the knowledge, how those handles (stick and throttle) influence speed trends. But this speed display has been degraded from one of the few main instruments in the center of the crosscheck to a tiny speck of digital numbers on the edge of a display. What should we then expect from training?