Originally Posted by
FGD135
how poorly the airspeed is communicated via the tape.
Just a minute here...
Originally Posted by
DozyWannabe
What was interesting about the original 1949 Grether study was that the experiments used a control group of non-pilots - so if we look at the summary:
You can see that round dial type "D" and tape display type "G" are roughly comparable in terms of percentage error and interpretation time (in fact the tape display seems superior to the dial in terms of percentage error). The interpretation time is interesting to compare because the non-pilots interpreted both in the same amount of time, but the AAF pilots interpreted the dial marginally faster. From this one could argue that the pilots' prior experience with the dial might have skewed the results.
I'll say that again.
Round Dial "D":
Percent error - 0.7 (pilots), 0.7 (non-pilots)
Interpretation Time - 1.7s (pilots), 1.9s (non-pilots)
Tape Display "G":
Percent Error - 0.3 (pilots), 0.4 (non-pilots) [Note both figures are superior to round dial "D"]
Interpretation Time - 2.3s (pilots), 1.9s (non-pilots) [Pilots take slightly longer to interpret this one by 0.6s, but non-pilots interpret as quickly as they did the dial].
How is the tape display poor or inferior?
With the overspeed, alpha and stall zones clearly marked alongside the tape as well as the speed bugs, this satisfies the "proximity" perception as well, plus with the PFD you can use colour changes to alert pilots to developing abnormalities in a way you cannot with analogue gauges.
I'm well aware of the psychological studies you're talking about, but as far as I can see all of the potential issues have been addressed. You may prefer the old gauges, but to say they're objectively "better" is incorrect.
Originally Posted by
Gretchenfrage
However: The underlying problem with this accident is the switch between moving throttles and fixed ones. The same findings apply: Pilots can get used to fixed ones, but perform better with moving ones. The real problem is when they were trained on one and then switch to the other design. It takes a long time to get the new one under your skin, especially when moving from fixed to moving.
Turkish 1951 says otherwise (i.e. three pilots who'd flown with nothing but moving thrust levers missed them rolling back too far). As with FGD - it's absolutely fine to have your own personal preference, but it's intellectually dishonest to state that your preference is fundamentally better with no significant proof. "Everyone knows..." just doesn't cut it.