Okay, I've been watching the transition to glass cockpits
in GA aircraft.

Clearly, the cost savings and simplification that comes from
integration is neat, and the reliability of an all-electrical
system is (probably) going to mean more safety for all of us.

But one thing bugs me -- the tapes.

I can't for the life of me figure out what all the manufacturers
have opted to provide flight information in these electronic
tape formats. Has this been proven to be more effective, more
ergonomic, easier to interpret, etc?

Many man-centuries of effort has been expended in the research of flight
instrument presentation, and I won't pretend to be an expert in all of it,
but I do have some knowledge and experience in the area. No its not
conclusively better, but does has some advantages and disadvantages. Your
instrument scan is smaller with tapes, but its harder to see trend movement.


My impression is that it is just the opposite, and I thought
that there was some research out there to back me up -- that
seeing the position of a needle, or in the case of a straight-
and-level flight or any stabilized maneuver, noticing movement
of a needle seems a lot easier to me than reading a tape,
understanding the number it displays, and thinking about whether
that number is the same as the last time you looked at it, etc.

Yes, but years of flying with tapes in business jet, regional, and air
transport should tell you something too. It's an acceptable way to present
the information, and the pilot can be trained to effectively use it.


I don't think it's a huge problem of course; it's totally
reasonable that a pilot will remember his altitude from one
moment to the next, but I do think there is some delta there.

I've noticed also, that the AI is drawn like an AI, mostly, and
that HSIs are drawn like HSIs -- an analog representation if
there ever was one. Engine instruments mostly are presented as
analog dials, with digits underneath them.

It's really only the airspeed, altitude, and vsi that suffer
this fate.

Why don't they just draw pictures of the round dials? Or at
least give the pilot the option?

Certification cost, development effort, desire to minimize menu selection
and install options.

I suspect that back when
these displays were new, there wasn't room for round dials.
But with 10+ inch hi-res displays, there sure is now.

Actually that's not true. The reason they are tapes is because attitude is
the most important instrument and its presentation needs to be the most
emphasized. There is simply not room to have the big attitude indicator and
round dial pitot static instruments. Minimizing display clutter is
important too, and some vendors have chosen to minimize the impact of the
ASI and altimeter on the attitude indicator by using tapes. Even the tapes
themselves can be translucent so you see right through them to the attitude
indicator colors. To make up for the deficiencies of tapes, there are
features like trend indicators, colors, prominent V speed markings, and
others. Compare Avidyne's and Garmin's to some that do have round dials
like this one http://www.rogersonkratos.com/mfd.html or the Collins MFD-268
and see how either attitude indicator shape is affected or has to be
smaller.

GA pilots generally don't like tapes as much at first, but can and do get
used to them.