I personally am very much looking forward to the return of round dial-style flight instruments. In my opinion, they beat vertical tapes any day. Human factors experts agree. The round dial with needle presentation has been proven to convey the greatest amount of information to the human brain in the shortest amount of time. Vindication!
I'm a young guy, raised around computers and technological gizmos and gadgets. I was writing HTML code when I was twelve, and I had just about every video gaming system that came out during the 1990s. I'm definitely no stranger to technology and the Digital Age. I must confess, however, that I have some heavy criticism for glass panel Primary Flight Displays (PFDs) that are finding their way into General Aviation cockpits. Most pilots from younger generations transition with ease into glass cockpits, and I was no exception. I was raised on steam gauges in legacy airplanes, and I didn't lay eyes on a glass panel cockpit (at least, in an airplane I was flying) until after I became a commercial pilot. I didn't truly start flying glass panel airplanes regularly until after I became a CFII, so my skills foundation is built upon old fashioned analog instruments. I was reluctant to transition into "the glass" because I naturally felt more comfortable behind a steam gauge panel. Eventually, though, times changed and I was forced to change right along with them when the flight academy I rent from and formerly taught at transitioned to an all-glass line. I suppose that was for the best because glass is certainly the way of the future.
GA pilots might not be aware that glass panels have been around for quite some time in jets. It wasn't until the last decade or so that glass panels significantly started spreading their way into GA cockpits. Certainly there is an overwhelming amount of improvement glass panels bring to cockpits in terms of reliability and information supply. And, in general I'm a huge fan of glass cockpits. The mission of this post is not to bash glass panel systems, it's to pick a specific bone with one element of glass panel PFD displays. Virtually everything else about glass panels is, in my opinion, fantastic. Multi-function Displays (MFDs) offer a wealth (sometimes surplus) of information to a pilot and do wonders to enhance situational awareness in many areas (position, fuel, weather). And the gigantic display of attitude on most modern PFDs is fantastic for reducing spatial disorientation. The only problem I have with these systems is the tape instruments for airspeed and altitude data.
Glass panel historians may correct me if I'm wrong, but I believe vertical tapes for airspeed and altitude indications were born out of a space necessity. And by space, I literally mean there wasn't enough room on the panel for traditional round gauge displays. One of the early PFD manufacturers figured out they could squeeze airspeed and altitude indications into the display by changing the instruments' presentation style to vertical tapes. In my opinion, that was too great of a compromise because vertical tape displays simply don't send information to the brain as efficiently as round dials. The tapes were invented, though, and became mainstream. Pilots adapted (as humans will), and tapes are now the norm in glass panel systems.
In my last post I mentioned how I like to keep things simple. That's because I've learned a decent amount about how the human brain functions during the years I've spent working with my own brain and the brains of others as a flight instructor. The human brain is quite expert at taking seemingly complex information and breaking it down into simple pieces that it can effectively digest and put into use. This break-down process takes time, though, so the fewer steps which the brain must complete to organize and label a sensory input, the faster the reaction time and the less chance for error. When we look at a tape display, we must process a number we see on the screen and decide what that number means to us (i.e. too fast, too slow, too high, too low). This involves a microsecond or two of comparing the number we see with our eyes to a number in our memory which we understand to be the current desired value. Any difference in those two numbers initiates another thought process about whether or not the deviation is within acceptable limits. Put simply, that's too much thinking. With a round dial, we glance at a needle and see where the needle is relative to a general position on the gauge. I like to think of dial-style gauges as having "neighborhoods." I know the airspeed needle will be in this neighborhood or general area for cruise flight, and it will move to this neighborhood for the approach phase. With round gauges we benefit from a simple pictorial display of relative information. Tapes can't do that for us. Round gauges also don't involve processing digits and comparing those digits with other digits in our minds.
I find it difficult not to fixate on the numbers readout on a tape display. This can actually make my flying sloppier because I'm focusing too much on insignificant numeric deviations and not on simply sending the airplane to the appropriate place in space. I can and do overcome this, but it takes more effort, and for what? To save some space on the panel? That doesn't seem like a good enough reason to me. So, here's what I'm proposing: let's create electronic screen displays of round dial gauges. The PFD I fly already does this for RPM information, but I don't use it because it lags behind my engine control inputs by a second or two. It's just not as satisfying at looking at a physical needle responding instantly to power changes. This can be improved, though, and I'm confident that PFD designers can find space for round gauges somewhere on the screen. Round dials are simply more compatible with human brains, and because human brains are currently the only brains commanding airplanes, I think it makes sense to equip our panels accordingly. Tapes will get the job done, but not as efficiently as dials.
I don't think tape displays will stand the test of time. I think I'll live to see round dial-style gauges make a comeback, and I'll be one of the first to celebrate. In the meantime, I'll do my best to continue my adaptation to tape displays, but I'll still be a firm believer in the power of the dial.
