Friday, June 03, 2005


Gauge-Reading Problems

David Megginson's recent Analog Flying post reminded me of a problem I had during the first few hours of flight instruction: I would often read the gauges incorrectly. For example, the instructor would ask "Check your airspeed," I'd say "I'm at 65," he'd say "Check again," and I'd say "Oh, I'm at 55—I'd better speed up." This happened repeatedly.

There is nothing wrong with my eyesight, and I don't suffer from dyslexia or reading disabilities, so I was stumped as to why I was always misreading the gauges. One day while driving home, I figured it out. Automobile speedometers and tachometers generally have zero in the lower-left quadrant, so the needle moves up and then to the right as the reading increases. That's what I've been seeing on gauges for the last twenty-something years: up and to the right means an increase. (Anyone who has sat through a sales pitch or read an investment prospectus is familiar with this pattern.)

Airplane gauges are oriented differently. They have zero at the top of the gauge, and the needle is generally in or near the lower-right quadrant of the gauge, so the needle is usually moving down and to the left as the reading increases.

This is why, as in the example given in the first paragraph, if I saw the needle "above" the 60 mark, I'd think the airspeed was sixty-something, when in fact it was fifty-something. It's oriented the same way as a clock, so it shouldn't be too hard to get used to it, but for me it was. Maybe it's easier for people who haven't been driving cars for a couple of decades.

This is usually not a problem for me anymore. I still occasionally misread the gauges when I want to read an exact number, but I'm usually just looking at the angle of the needle, as described in Analog Flying, or checking whether the needle is within one of the color-coded arcs. I'm trying to get used to thinking of the needle moving clockwise (increase) or counter-clockwise (decrease) instead of up/down/left/right.

I have nothing against the "steam-gauge" cockpit instruments, but I think a little digital LED/LCD display in the center of each gauge would be a helpful feature.


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