This might be an interesting feature to model in PSX if it's not too difficult. Sorry about the bumps. We were getting thrown around pretty good.
https://www.youtube.com/watch?v=PXRTA1OqUNQ
Great!
Thx for sharing!
Actually, (and I know I will take flak for this) that isn't quite the same thing as St Elmo's fire, although it seems to have drifted into common use.
Historically it was seen on anything pointed that was in a static environment, like church steeples, or telegraph poles. I believe it was seen on early sailing ships in the rigging in storms.
The static on the windshield is often seen and a product of the plastic and metallic elements in the windscreen coating, but it's certainly a pretty, if slightly unnerving sight.
I have only seen the "real" thing n a very few occasions. On one occasion it looked as though we had a light in the nose - with a ghostly light spreading out many yards ahead of the aircraft, and I have also seen it at the front of the engine intakes on one occasion.
Nice video!
Peter.
Thanks, Peter. I didn't know what else to call it. I've always thought it was some sort of electrical discharge generated by the moisture passing over the windshield. We were in icing conditions at the time. Are you suggesting that the lightening-type discharge is actually occurring inside the glass as opposed to occurring on the outer surface? If so, I'm glad I posted this because I learned something too.
I'm not sure where it discharges. Maybe between the layers of glass. You can't "lead" it down with your fingers as you probably know...it's still static of some sort so there must be some sort of external interaction..
Peter.
It would have been interesting to see what the discharge wicks were doing at the time (if anything).
Fascinating stuff - thanks for posting video. Atmospheric electrical phenomena have been studied since at least the time of Ben Franklin and it's still a complex and evolving scientific field (the American Geophysical Union has a special section just devoted this discipline!). I'm no expert in this area myself but I think Peter is basically right that what's shown in the video is due to charge build-up in the glass-laminate layers discharging internally to the metallic framework. The nose and engine intake glows mentioned may be related effects influenced by shocks in the air flow.
Cheers,
Torrence
Addition: I'll have to see if I can show this to some of the guys at the lab who do material testing on spacecraft cables etc. - they also do public education shows with things like huge Tesla coils (very impressive on a dark night).
T
It's on the outside of the aircraft, at the interface between the oncoming air and aircraft skin surface. If you could step outside, it extends over the aircraft skin, as well as the windows, but you can only see it at the windows because they're unable to discharge via the static wicks, so they eventually discharge onto the window when the potential is great enough.
The aircraft skin is designed to dissipate the static electricity around the fuselage rather than conduct it, so it doesn't build and start arcing.
If you could see the electric field around the wicks at the time, it would look like a stream of smoke.
It occurs because the aircraft flying through the air acts like a huge flying vandagraph machine. The light you see is actually plasma discharge.
If you listen to the radios, you can sometimes hear it, too. :) It sounds like a ringing sound. On HF you'll probably hear it as increased static.
Thanks for the detailed explanation. I had assumed the diffuse outside glows were plasma phenomena of some sort, but wasn't sure what caused the more intense window discharges.
Cheers
Torrence
Thanks to all for the explanations.
This reminded me of the part in Bob Buck's "North Star Over my Shoulder", where he flew a modified B17 during WWII to research static discharges.
Great book!
Which parameters and what values need to be used to enable this (randomized) effect?
We have:
OAT on ground
OAT at aircraft
TAT
flight deck internal temperature
windshield heat on/off
in-cloud yes/no
below-cloud yes/no
above-cloud yes/no
between-clouds yes/no
aircraft altitude
icing status wings
icing status nacelles
IAS
EAS
TAS
lat/lon
etc.
|-|
Hi Hardy,
I don't see this too often, so I'm not sure what the optimum conditions would be for it. If you look at the radar, we were paralleling a line of weather about 30 miles to the west -- Not super-strong weather, but with a lot of moisture. The winds aloft were pretty strong. I think I see 300/95 and probably blowing a lot of that moisture in our direction. We were at M.76 and FL330. I don't remember the temperature but we had nacelle A/I on so we were definitely below +10 TAT. We were not in the "clouds" but there was definitely visible moisture and I think the temperature was well above ISA. I don't normally use wing A/I unless I do so per the CF6 AD (ice crystal icing), requiring the wings to be on if in icing conditions (even below -40SAT) when at FL220 or below.
I took the video on 11/3 at about 0500Z, between KDFW and KCVG. As you can see from the ND, we were approaching PXV. Maybe there's a way to go back to the weather charts for that period and get the data. I don't know.
Jon
Another interesting thread on the same theme, and a nice conclusion at the end ( last post ).
http://www.airliners.net/forum/viewtopic.php?t=737177
Everyone concludes in that string that it is St. Elmo's fire. I think Peter is technically right here -- It's really not St. Elmo's, but easily and commonly mischaracterized as such. So what do we call it? Plasma?
Quote from: Hardy Heinlin on Sat, 11 Nov 2017 17:01
Which parameters and what values need to be used to enable this (randomized) effect?
Given the comments and the various links, Hardy, you might be able to model this relatively realistically by just associating the window electrical display with the existing weather model. Here's one possible list for a WXR page setting:
Static discharge on aircraft ("St. Elmo's Fire") possible [y/n]
Required conditions
Thunderstorm activity in the vicinity
Between cloud layers with visible moisture
Probability of occurrence (similar to other items like go around or holding probabilities - randomized)
Low
Medium
High (for demo purposes)
I think that covers most of the characteristics of what pilots report. I've only experienced one 'event' as a passenger. We were descending to land at LAX going through turbulence and clouds with lighting flashes in the vicinity when there was loud BANG and a bright light outside the left windows. I thought initially of some engine problem, but - after a long 10 secs or so, the pilot came on the speaker and said there was no problem, but we had had a 'static discharge' off the nose of the aircraft. I don't know exactly what it looked like in the cockpit, but they sounded impressed. [Note added: This may have been in the category of a lightning strike for all I know - wasn't able to inspect the aircraft after landing.]
Cheers,
Torrence
Note - I'm of the school that thinks that the existing weather model/radar/native scenery is already very realistic and immersive. There's enough complexity and randomly varying parameters the overall effect is quite convincing (leaving aside debates about how you can set it to reproduce 'exactly' what you see outside your window for a given METAR report)
T
Thank you, Torrence.
I'd like to make this effect completely automatic, i.e. not user controlled by additional switches on the WX page. So the main parameters, as you're suggesting, are:
• Thunderstorm activity in the vicinity
• Between cloud layers with visible moisture
(I wouldn't call it "St. Elmo's Fire".)
Unfortunately, I'm now seeing a cosmetic problem: When thunderstorms are in the vicinity, PSX already simulates bright random zigzag lines on the windshield, appearing for just a fraction of a second. Now, if I add such windshield discharging effects like in the video, they will look very similar to regular lightning lines (like reversed tree branches), and within these fractions of a second the PSX users won't notice the difference between regular lightning effects and windshield discharging effects. So I fear my idea to implement this effect is not worth the effort ... I'm not sure yet ...
Cheers,
|-|ardy
Hmmm, not being an expert here and being aware that PSX is primarily a trainer:
Thunderstorm in the vicinity:
Shouldn't this be rather very diffuse "flashes", i.e. the whole coulds illuminate for a fraction of a second.
E.g. like a more intense "flashing landing light" while being within the clouds.
Windshield dischgarge/St Elmo's fire:
From the videos this appears to be more sharp-edged tree-like "flashes".
Also colour could be used to differentiate between real "lighning in the vicinity" and "windhield discharges".
I was always wondering when to use the storm lights.
Are we discussing training scenarios for when to use storm lights in this thread?
Just some amateur thoughts.
Regards, Holger
Holy Heinlin fire :-)
(I'm not holy, I'm evil.)
These are still just nuances, Holger. But I think lightning in PSX is only visible when you are below the clouds (unless it's lightning caused by volcanic ash). That's a good point. The plasma effects may then only be visible when you are at high altitudes.
Regards,
|-|ardy
Maybe this helps:
https://science.howstuffworks.com/nature/climate-weather/atmospheric/st-elmo-fire1.htm
I think that article is about "St. Elmo's Fire", i.e. that steady "corona" at the tip of pointed objects.
Hi Hardy,
In addition to Holger's comments, it occurred to me that there are other things that distinguish the 'discharges' from lightning as modeled. I've spent some time comparing Jon's discharge video with the default situ, which is a great example of lots of lightning, turbulence etc. in PSX. The discharges look different because they are clearly on the windows, in the aircraft frame of reference and move when the aircraft does, while the lightning is 'outside' tied to the scenery frame of reference (i.e. they will be partially hidden behind window frame structures when banking etc.). I don't know enough of all the magic you did with the native scenery vs inside the cockpit view to be sure, but could you do something with the 'discharges' that is just a series of momentary bright patterns *tied to the aircraft frame of reference". If that could be done, along with Holger's points re altitude and low frequency of occurrence they wouldn't be mistaken easily for lightning.
Cheers,
Torrence
On the subject of lightening, this is a view out the left window as I was deviating around some weather. https://youtu.be/Eq7H1S_Ak88
Take a look at the amount of activity out there only 20-30 miles away and compare that to the lack of red returns on the ND (over CDS). I couldn't get any red returns to display no matter what tilt setting I used until I went to MAX on the gain. We were above most of this stuff, but I decided to deviate around the south side anyway.
This is a good example of why I don't like to leave the radar gain in AUTO or CAL (calibrated) and let it do its thing -- I don't trust it. This is especially true on our -400s. In the case of this video, you couldn't miss the lightening, but I've hit towering CBs at night at FL360 over India that had no lightening and weren't even painting on the radar while it was in AUTO/CAL. It was quite a surprise to go from glass-smooth air to severe turbulence in a split second. So, I'm a big fan of playing with the gain and tilt quite often during cruise if it's a dark night or if I suspect there could be weather ahead.
Nice shot, Jon :-)
Hi Torrence, yes I would refer to the aircraft frame, but still crop it at the window edges and would not display it for more than three time frames (minimum 40 ms). Within that short time the aircraft can't significantly change its attitude to demonstrate the different references. But the good point is that PSX only shows thunderbolts when the aircraft is below the CB, so they would never occur when those plasma effects only occur above the CB. A blueish color would also help to distinguish the effects. I'm thinking of these conditions:
aircraftAlt > CbTop
AND aircraftAlt < ( CbTop + 5000 )
AND lateralDistanceToCb < 50 nm
AND nighttime
AND randomizerSaysYeah
Cheers,
|-|ardy
Quote from: emerydc8 on Tue, 14 Nov 2017 07:24
On the subject of lightening, this is a view out the left window as I was deviating around some weather. https://youtu.be/Eq7H1S_Ak88
Take a look at the amount of activity out there only 20-30 miles away and compare that to the lack of red returns on the ND (over CDS). I couldn't get any red returns to display no matter what tilt setting I used until I went to MAX on the gain. We were above most of this stuff, but I decided to deviate around the south side anyway.
This is a good example of why I don't like to leave the radar gain in AUTO or CAL (calibrated) and let it do its thing -- I don't trust it. This is especially true on our -400s. In the case of this video, you couldn't miss the lightening, but I've hit towering CBs at night at FL360 over India that had no lightening and weren't even painting on the radar while it was in AUTO/CAL. It was quite a surprise to go from glass-smooth air to severe turbulence in a split second. So, I'm a big fan of playing with the gain and tilt quite often during cruise if it's a dark night or if I suspect there could be weather ahead.
Very interesting thank you Jon.
Another interesting source of info:
https://jpcvanheijst.com/blogs/2017/06/574544-st-elmo-s-fire-4-minute-read
But actually, even sandstorms, for instance in Africa, combined with sufficient convective activity, can bring particles to the higher levels of the troposphere, causing enough "static source" for this type of effect to take place, without the presence of TS.
They all call it St. Elmo's Fire. I think it is correct. The steady glow is certainly St. Elmo's Fire, and the occassional sparks are just another side effect of it, even though they are sparks and not a steady glow. St. Elmo's sparks, so to speak ...
|-|
It's also caused by flying through precipitation, or cirrus. TS in vincinity just makes it more likely.
For reference, some other examples:
https://youtu.be/P1luqXNqC1c?t=2m23s
https://youtu.be/ZX7t4t_UPk8?t=1s
https://youtu.be/zyWX3VRsk38
https://youtu.be/qQiFBTDPhrs
https://youtu.be/NUYr0DPU3uM?t=12s
https://youtu.be/TxGPrlrgn34
https://youtu.be/Py5mkrrcLPU?t=16s
https://youtu.be/gILe7KAIAHY?t=39s
I now think St. Elmo's Fire is the purple glow on the aircraft nose, not the static discharge. In the above videos there is no purple glow, just static discharge.
|-|
Quote from: Hardy Heinlin on Sat, 18 Nov 2017 23:12
I now think St. Elmo's Fire is the purple glow on the aircraft nose, not the static discharge. In the above videos there is no purple glow, just static discharge.
Many years ago I did a lot of research on electrostatics, I would concur with your assessment that the static purple glow is St. Elmo's Fire (though I would just call it 'corona discharge'). Wikipedia shows a nice example. (https://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/Corona_discharge_1.JPG/1200px-Corona_discharge_1.JPG)
It's a continuous effect; a glow that may have fine spark discharges inside it.
Your list of youtube videos are, like you said, just straightforward static discharges.
Edit: though I hesitate to assume Wikipedia is authoritative, it does state "The phenomenon known as St. Elmo's Fire was, and is, a common occurrence of corona discharge". Article here. (https://en.wikipedia.org/wiki/Corona_discharge)
I'm changing my opinion on this every day :-) Today I think again that both the glow and the spark is St. Elmo's Fire. It's just a name of something that perhaps sailors invented some centuries ago; a name for a certain glow that is often accompanied by sparks. A debate about this name is actually a debate about an answer to the question: "What did those sailors see?" They probably saw both: glow and sparks.
It's similar to the question "the region up there between the two oceans, is that the USA or America?" It's not really America because America is the entire continent, not just a fraction of it. No, it's definetely America because it belongs to that continent. No, it's just the USA, not the entire continent. No, it's both.
}{ardy
In Meteorology we cal all of those phenomena the same - St. Elmos fire is the common, non-scientific, designation though...
Hi all,
for a random discharge flash I now set these conditions which are checked in an infinite loop:
IF ( aircraft is in volcanic ash OR ( any CB is within 77 nm
AND aircraft is above CB base
AND ( aircraft is between two cloud layers OR in cloud OR below ( cloudTop+2345 ft ) ) ) )
AND ( almost or total nighttime OR in cloud )
AND TAS > 342 kt
AND randomizer says yes
|-|
Well then ... when you see something rare like this, it's not a lightning strike in the scenery; it's a static discharge on the windshield :-)
(http://aerowinx.com/assets/pics/psxStaticDischarge1.jpg)
|-|
Pretty!
Does it go towards your finger if you put it against the window? :-D
Hoppie
It's so fast; you can't even hit the Pause key before it disappears :-)
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Very nice, Hardy!
Jon
I believe you found an excellent graphic representation.
Thank you!
Kind of you! It's a cool feature! :)
Discharge flashes are now modeled in PSX 10.14:
http://aerowinx.com/board/index.php?topic=4191.0
|-|ardy
A friend at UPS just experienced a static discharge on a 748 out of ICN last week. He said it was really dry air on the ground and he noticed that even getting out of the van he could see static discharges coming off his clothes as he slid across the van seat. As they were climbing out at around 1500' they saw a large flash and loud pop that appeared to be about 50' in front of the nose. It was so loud that the guys in back came up to ask about it. Maybe it was all that friction caused by a two-week-old airplane.
Can't wait to see this in action. Thanks, Hardy!
You'll need a lot of luck :-) They appear seldom and last for just a fraction of a second ...
Hmmmm ... Could you give a 'ball park' estimate of how long one might need to orbit inviting CB's to experience an instance?
Cheers, and Super Solstice to everyone (traditional astronomers' seasonal greeting and applicable to most cultural groups :) )
Torrence
It's too complicated for a ball park summary, but I guess the probability is nearly as low as in real life. So better don't wait for it. It might appear when you're not expecting it :-)
Cheers,
|-|ardy
I'll keep a 'weather eye' out for it. It's a nice semi-Easter egg. I still get surprised sometimes by radar interference around Groom Lake and Area 51.
Cheers,
Torrence