Steam Gauges Are Safer..?
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The watch comparison is flawed in my opinion. On a digital speed tape you still do not look at digits but at the speed bug. So at a glance you know wether you are a few knots fast or slow in the same way as glancing at an analog watch.
You fly the bug, not a digit so the thought process stays the same wether you have a dial or a tape in front of you. In the 737-300 we had both, a steam gauge dial and a digital speed tape. I preferred the tape.
You fly the bug, not a digit so the thought process stays the same wether you have a dial or a tape in front of you. In the 737-300 we had both, a steam gauge dial and a digital speed tape. I preferred the tape.
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Yes, steam gauges are safer than the tapes, and in the wake of the crashes to Asiana 214, Colgan 3407 and Turkish 1951, I suspect that more and more aviation safety-related people are coming to that same conclusion.
In the days of the X-15 aircraft, NASA did a study on tape displays versus round gauges. The study wasn't on which was "safer", but rather, which resulted in the more accurate flight path.
Not surprisingly, the round gauges were found to give the more accurate flight path. No doubt, some would say this was because the pilots involved had been trained on the round gauges.
Wrong. Our brains work very differently when working with a needle moving around a round dial than they do with a tape. This is because, with the needle, provided we just want to make a quick assessment of the reading, it is a matter of just making a quick assessment of the ANGLE of the pointer.
Now it just so happens that humans are very, very good at working with angles. For whatever reason, evolution has made us highly proficient at recognising, estimating, assessing, remembering and repeating angles. It matters not whether you are an old pilot, a young pilot or a someone living in a cave.
When using the round dial to manage our airspeed throughout the approach to land, for example, we are predominantly just glancing at the angle of the pointer. We don't care what the exact reading of the airspeed is, we are just checking for the pointer angle to be "about right".
Consider what your brain is going through when using an analogue watch, as compared to an all-digital watch, for example. Let's say your lunch break is at 11:45 and you are hungry and are frequently checking the time on your watch.
With the digital watch, you must read the two minute digits and your brain must process them. And, the watch must be sufficiently close and the relative movement between your eyes and the watch must be minimal enough to allow the digits to be read.
With the analogue watch, however, you only need to glance at the angular position of the minute hand. The watch could be upside down, moving rapidly relative to the eyes or much more distant than the digital watch. In all cases, the analogue will rapidly give you an idea of how far from 11:45 the time is!
The brain has done a lot less work with the analogue than it had to do with the digital. To find the time on the digital, the eyes had first to be trained on the tiny space where the minute digits are, then the digits read and processed.
Under calm, low workload, low stress situations, this difference in workload is not noticeable. But in a high workload, high stress situation, with the brain close to saturation, the extra work demanded by the tape airspeed indicator can be too much for the brain. It will not even attempt to read the airspeed. There may as well be no airspeed indicator fitted to the aircraft at these times - the result is the same!
Just going back to those crashes I listed in my first paragraph. All of those aircraft stalled on final approach. All were glass cockpit types with a tape for airspeed. Stalling on final approach is a completely new way to crash an aircraft. In another thread, I invited participants to name a similar accident to a commercial airliner fitted with round dials.
Only one was identified (United 553, a 737-200 on approach to Chicago Midway on December 8, 1972), but that accident had a number of important differences to the three I have given (the main ones being that it was an unstable approach with the pilots apparently aware of the low/decaying airspeed).
In the days of the X-15 aircraft, NASA did a study on tape displays versus round gauges. The study wasn't on which was "safer", but rather, which resulted in the more accurate flight path.
Not surprisingly, the round gauges were found to give the more accurate flight path. No doubt, some would say this was because the pilots involved had been trained on the round gauges.
Personally, I have no problems with the standard glass setup, but I guess it's what you're used to or, perhaps more accurately, what you cut your teeth on...
Now it just so happens that humans are very, very good at working with angles. For whatever reason, evolution has made us highly proficient at recognising, estimating, assessing, remembering and repeating angles. It matters not whether you are an old pilot, a young pilot or a someone living in a cave.
When using the round dial to manage our airspeed throughout the approach to land, for example, we are predominantly just glancing at the angle of the pointer. We don't care what the exact reading of the airspeed is, we are just checking for the pointer angle to be "about right".
Consider what your brain is going through when using an analogue watch, as compared to an all-digital watch, for example. Let's say your lunch break is at 11:45 and you are hungry and are frequently checking the time on your watch.
With the digital watch, you must read the two minute digits and your brain must process them. And, the watch must be sufficiently close and the relative movement between your eyes and the watch must be minimal enough to allow the digits to be read.
With the analogue watch, however, you only need to glance at the angular position of the minute hand. The watch could be upside down, moving rapidly relative to the eyes or much more distant than the digital watch. In all cases, the analogue will rapidly give you an idea of how far from 11:45 the time is!
The brain has done a lot less work with the analogue than it had to do with the digital. To find the time on the digital, the eyes had first to be trained on the tiny space where the minute digits are, then the digits read and processed.
Under calm, low workload, low stress situations, this difference in workload is not noticeable. But in a high workload, high stress situation, with the brain close to saturation, the extra work demanded by the tape airspeed indicator can be too much for the brain. It will not even attempt to read the airspeed. There may as well be no airspeed indicator fitted to the aircraft at these times - the result is the same!
Just going back to those crashes I listed in my first paragraph. All of those aircraft stalled on final approach. All were glass cockpit types with a tape for airspeed. Stalling on final approach is a completely new way to crash an aircraft. In another thread, I invited participants to name a similar accident to a commercial airliner fitted with round dials.
Only one was identified (United 553, a 737-200 on approach to Chicago Midway on December 8, 1972), but that accident had a number of important differences to the three I have given (the main ones being that it was an unstable approach with the pilots apparently aware of the low/decaying airspeed).
PENKO - it's a wider discussion that speed tapes ..... but on speed tapes not sure you're right - for example, mini ground speed on an airbus gives you a continuously moving bug so actual awareness of what you are trying to achieve is limited and that's what this is all about ..... this would also take us to - just follow the FDs
When using the round dial to manage our airspeed throughout the approach to land, for example, we are predominantly just glancing at the angle of the pointer. We don't care what the exact reading of the airspeed is, we are just checking for the pointer angle to be "about right".
and then, horror of horrors, with a panic raised tone of voice, "-1" (jeez)Personally, I'm only good for +/- 10 kt
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The analogue dial derives from the clock face. The earliest clock faces had a revolving dial with a fixed pointer - somewhat like the tape display - but this was discarded in favour of a fixed single hand showing the hours. A couple of centuries later, the minute hand was added. The moving hand was easier to read because we can work well with angles.
FGD135
I am sure you are absolutely right, your analogy of the watch is a very good one. Many years ago I did some work with Boeing when they were evaluating PFD displays during the design stage for the 747-400. We had to fly several complicated procedures using various displays - some with tapes and some with round dials. Provided the scaling was right they were all flyable but I much preferred the old round dials, particularly for airspeed.
The problem I had was to try to decide how much of my preference was due to familiarity with round dials (which I had flown throughout my career) rather than the fact that they were better for the reasons FGD135 has stated.
I believe FGD135 to be correct.
I am sure you are absolutely right, your analogy of the watch is a very good one. Many years ago I did some work with Boeing when they were evaluating PFD displays during the design stage for the 747-400. We had to fly several complicated procedures using various displays - some with tapes and some with round dials. Provided the scaling was right they were all flyable but I much preferred the old round dials, particularly for airspeed.
The problem I had was to try to decide how much of my preference was due to familiarity with round dials (which I had flown throughout my career) rather than the fact that they were better for the reasons FGD135 has stated.
I believe FGD135 to be correct.
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Much to their surprise, the US Air Force has discovered that fighter pilots preform better on analog gauges... even the new generation of pilots who grew up on computers and video games do better on the old round dials. This is not, however, true of the weapons systems airmen. Their video game experiences are a plus.
There seems to be a growing consensus that it's simply an evolutionary aspect of humans that is currently, somewhat poorly understood.
There seems to be a growing consensus that it's simply an evolutionary aspect of humans that is currently, somewhat poorly understood.
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But we are no fighter pilots who accelerate from naught to Mach 2 in mere seconds. For those, a round steam gauge might be more useful. We are airline pilots who simply fly the bugged speed. That's why I'm still not convinced that round steam gauges are safer in our type of flying.
Furthermore, the digital speed tape provides a very clear picture, more intuitive than a steam dial can ever achieve. At a glance you know your minimum, maximum, bug and actual speed. It's all there in a neat package. There is no more mental processing required other than to follow the bug and avoid the red and yellow. Again, you are not flying digits, you match up the speed index with the bug...
Furthermore, the digital speed tape provides a very clear picture, more intuitive than a steam dial can ever achieve. At a glance you know your minimum, maximum, bug and actual speed. It's all there in a neat package. There is no more mental processing required other than to follow the bug and avoid the red and yellow. Again, you are not flying digits, you match up the speed index with the bug...
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Penko, after reading your latest contribution I re-read the article in the opening post. Nowhere does it mention the expression "airline pilot" 
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It's a General Aviation forum and most respondents give examples of 777's, 767's Airbus, Gulfstreams and the odd X-15, so...
PENKO - it's a wider discussion that speed tapes ..... but on speed tapes not sure you're right - for example, mini ground speed on an airbus gives you a continuously moving bug so actual awareness of what you are trying to achieve is limited and that's what this is all about ..... this would also take us to - just follow the FD
Last edited by PENKO; 17th Feb 2016 at 21:29.
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Noted. But the article refers to "TAA", technically advanced aircraft, which is a far wider subject.
PENKO
Very sorry about the terminology - after 12k+ hours on the Airbus (about 10k on Boeings etc etc too) including as a trainer and examiner you'd think I'd remember ....... the important stuff
!
Your obviously into airspeed - as for real world awareness I really don't agree - it's not about the flight envelope
- Thought we were talking about "steam gauges" ... Sorry about entering your GA forum - I'll leave you to it and I'll get back to the small G1000 powered ten seater I now fly.
Very sorry about the terminology - after 12k+ hours on the Airbus (about 10k on Boeings etc etc too) including as a trainer and examiner you'd think I'd remember ....... the important stuff
!Your obviously into airspeed - as for real world awareness I really don't agree - it's not about the flight envelope
- Thought we were talking about "steam gauges" ... Sorry about entering your GA forum - I'll leave you to it and I'll get back to the small G1000 powered ten seater I now fly.
Last edited by Good Business Sense; 18th Feb 2016 at 09:02.
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This, along the with other symbology, which is currently used on speed tape depictions, could easily be replicated in round dial form (analog) on an LED flat panel display.
Last edited by wanabee777; 18th Feb 2016 at 11:28. Reason: http://www.pprune.org/editpost.php?do=editpost&p=9273856
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The trend arrow on a speed tape is almost as good as a needle moving round a round gauge....
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I think it's because on a round display there is an angular change as well as a quantitive change.
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Good Business Sense, we will have to agree to disagree then.
The 737 NG has the option to show round dials in their otherwise full glass cockpits. Not many airlines use that option. Why?
As for the ground speed mini remark, I was not trying to be pedantic. As an Airbus pilot you will know yourself how much misinformation there is on this forum regarding the whole Airbus fly by wire concept. I was just trying to be precise.
The 737 NG has the option to show round dials in their otherwise full glass cockpits. Not many airlines use that option. Why?
As for the ground speed mini remark, I was not trying to be pedantic. As an Airbus pilot you will know yourself how much misinformation there is on this forum regarding the whole Airbus fly by wire concept. I was just trying to be precise.
PENKO
Have helped design elements of the A330 and A340 cockpit when seconded to Airbus at Toulouse back in the mid 90s I could tell you why and I could tell you what the process is but you would not believe it except to say that no line pilot, trainer or examiner had a say in it
The 737 NG has the option to show round dials in their otherwise full glass cockpits. Not many airlines use that option. Why?