On Wednesday, January 16, 2013 5:47:44 AM UTC+1, Eric Greenwell wrote:
On 1/15/2013 7:48 PM, Bill D wrote:

On Tuesday, January 15, 2013 5:15:40 PM UTC-7, Craig R. wrote:

If I remember correctly, studies were done on the ability of the

brain to interpret and understand data quickly using either an

analog or digital readout. Time and speedometer readouts were the

main emphasis of the study. The study showed that the brain

interprets the analog display quicker and with greater accuracy.

Besides the issue of running out of power, it appears that the

analog display is superior to digital for information gathering and

execution. Something to consider in going to an all glass panel.

Perhaps someone that is up on this subject could elaborate?



That study was done very early in the digital age - 1960's IIRC.

Current studies show that while it remains easier to detect a trend

with an analog needle, a discrete value is easier to read in digits.

Few would use an altimeter to detect a trend so it works best as a

numeric display which is why few high performance aircraft use 3-hand

altimeters anymore - in fact they're pretty much relegated to gliders

which means they're probably going to disappear. Not many "little old

Swiss watchmakers" left to fix them these days.



After a year or so of getting my 302, the first instrument I had with a

digital altimeter display, I noticed I used it instead of the 3-hand

"clock". No effort was made to learn or do that - it just happened.



The analog airspeed still seems to be better than a numeric one, but I

don't have a numeric ASI to see if that's true. The airspeed is quite a

different quantity than altitude, and maybe that's why digital might not

be a good choice for it: airspeed has the same "right" and "wrong"

positions during the flight, regardless of your location; the "right"

altitude varies constantly during the flight.

Erik, once you have flown with a properly designed digital airspeed indicator, you will hate going back to an analog one. We are trained to think in terms of discrete, specific airspeed values, and while yes you can glance at your airspeed indicator and (if you have flown with it a lot) can get an idea of your speed ("3 o'clock is a safe pattern speed, 2 o'clock is getting slow"), if you are aiming for a specific speed you still have to compare the needle to the scale, interpolate, and decide what speed it is indicating. With a big number, it's just there. If I want 63 knots on final, I look at the panel, see 61, and immediately know that I'm 2 knots slow. Ditto when cruising - my nav computer says optimum Mc speed is 102 knots (yeah, it's a good day out west ;^), I accelerate to what I think is right judging by nose position on the horizon, then a glance see 106 and ease the nose up a bit.

One of the jets I'm working on now (a brand new advanced trainer) has a neat featu a bug next to the flight path vector that shows your airspeed trend based on attitude and thrust setting - if it's above the FPV, you will accelerate. So when you reach the speed you want, you ease the throttles back until the bug is next to the FPV, and your speed will stay the same. Makes instrument flying so easy it's ridiculous! For gliders, you could use the same idea to indicate your airspeed trend in the pattern (based on pitch attidude/AOA and accelleration) so at a glance could see if you are slowing down or speeding up.

Fun stuff

Kirk