What is the deal with tapes?

Dave Jacobowitz wrote:
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?

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.

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? 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.

Opinions?

-- dave j
-- jacobowitz73 --at-- yahoo --dot-- com

PS -- I work in high tech; I like computers a lot, I'm not a
luddite. I just wonder if there is real human-factors based
support for the tape representation, or if it's just a "cool"
factor thing.

I think its more about getting the maximum information in the
minimum space. Dials take up room, even on a virtual display.
Every study probally shows that simple digits are non-intuitive.
Tapes integrate well with lots of other things going on in the
display.

The long term goal seems to be to have two instruments, the HSI
and a "VSI" or Vertical situation indicator, which is what the
attitude gyro is evolving into.

I suspect dials are better if you have the room. They allow the
entire scale to be placed on the display at once.

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