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nuckolls.bob(at)aeroelect
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 Posted: Sun Jan 30, 2022 1:45 pm Post subject: Wiring Best Practices? (An anecdotal follow-up) |
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| Quote: | The second was at Beech on a Hawker 800 where a host of warning
annunciators were triggered by the energizing of a 400Hz, AC
blower motor in aft cabin. |
This problem was a combination of TWO cases where
the designers stubbed their toe . . .
The motor power wiring was poorly laid out and installed
but the real ace-kicker was that sense wires from various
monitored systems in the aircraft were NEVER qualified
to modern (post 1975) EMC compatibility practices.
Those sense wires had ZERO protection from fast-rise-
time, low energy events. I.e. they were literal
'antennas' connected to dozens of 'receivers' in the annunciator
system just waiting around for an insulting event to
happen. That annunciator system was the recipient of
dozens of band-aid hacks to work around false warnings.
I only had occasion to wrestle with one such event.
The second incident was a real hand wringer, again Hawker 800,
where the HF transceiver would cause all three generators
to shut down during transmission . . . this was discovered
about Dec 15 on a group of airplanes that were slated for delivery
on or before Dec 31 to meet certain financial expectations.
That turned out to be a combination of two issues. (1)
the generator controllers were all solid state designs with
rather old pedigrees. Again, NEVER qualified to
contemporary EMC compatibility requirements . . . and
(2) somebody decided that an airplane like the Hawker
really looked shabby with that open wire HF antenna strung
from vertical fin to the top of cabin. So Collins came
to the rescue and offered an antenna tuner that would
make a wad of bailing wire and a 55-gallon drum 'look'
like an efficient antenna.
Hawker engineering insulated the leading edge cap
on the vertical fin from the rest of the skin and
structure. The antenna tuner would excite that strip
of metal to the satisfaction of the HF transceiver
but . . .
The ground return system for that 'antenna' was never
designed for such service. A result was that the interior
of the hell-hole behind the pressure bulkhead became
RF 'hot' like you wouldn't believe. Combine this with
the out of date generator controllers and guess what?
Nuckolls and crew spend some panic driven days down in
Little Rock trying to figure out how to deliver these
airplanes.
I posted a photo array of the bubble-gum-n-baling-wire
solution at https://tinyurl.com/ybsl2zsq
I didn't know which of the signal wires to the GCU
were vulnerable . . . no time to go to the lab
and measure anything. Sooo . . . put capacitors on
EVERY possible wire. So after a trip to the warehouse
and an overnight from Digikey, we built a number of
'filtered harnesses' to insert between ship's wiring
and the vulnerable GCU's. They built up 3 or 4 ship-sets
of these things and got them bought off.
We were modifying a harness which was a Beech
fabrication, NOT a GCU which was a 'qualified' supplier
product, so it seems I could stuff a wad of bubble gum into
a connector and nobody cared . . . just don't
mess with a PMA/TSO device . . . you need god's permission
to do that.
I never did like that 'fix' but my boss was happy.
Just a few Tales from the Crypt to emphasize the need
for skepticism when you read about practical
imperatives for doing things to your airplane.
The question that is always good to ask, "Has
anyone conducted repeatable experiments and documented
the recommended practice deduced with data from those
experiments?"
Folks who pass along various and sundry admonitions
for 'avoiding problems' are offering the ideas
in good faith. But it can be difficult to separate ol'
hangar tales and legends from good physics. There
are plenty of talented engineers and technicians
who are victims of poor advice propagated in the
name of safety and good performance.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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user9253
Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan
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| Posted: Mon Jan 31, 2022 8:05 am Post subject: Are Red Cockpit Lights Better at Night? |
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| Quote: | Folks who pass along various and sundry admonitions
for 'avoiding problems' are offering the ideas
in good faith. But it can be difficult to separate ol'
hangar tales and legends from good physics. There
are plenty of talented engineers and technicians
who are victims of poor advice propagated in the
name of safety and good performance. |
That makes me think of using red cockpit lights at night.
Every pilot knows that red light does not ruin night vision as much as white light, right?
But is that really true? Are builders installing red lights for naught?
Is this another old wives tale that never dies?
Dim red lights are used in camera film dark rooms. So if red lights are good for film, they must be good for our eyes too, or so the reasoning goes.
What are the physics?
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Joe Gores |
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rv8iator
Joined: 11 Apr 2006
Posts: 143
Location: Newberg, OR
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| Posted: Mon Jan 31, 2022 9:39 am Post subject: Wiring Best Practices? (An anecdotal follow-up) |
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For very low levels of intensity (scotopic vision), the sensitivity of the eye is mediated by rods, not cones, and shifts toward the [url=https://en.wikipedia.org/wiki/Violet_(color)]violet[/url], peaking around 507 nm for young eyes; the sensitivity is equivalent to 1699 lm/W[9] or 1700 lm/W[10] at this peak. (wikipedia)
For low light illumination ideally we would illuminate with a source of 507 nm.
[img]cid:ii_kz2z4pkr1[/img]
...Chris
On Mon, Jan 31, 2022 at 8:12 AM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
> Folks who pass along various and sundry admonitions
> for 'avoiding problems' are offering the ideas
> in good faith. But it can be difficult to separate ol'
> hangar tales and legends from good physics. There
> are plenty of talented engineers and technicians
> who are victims of poor advice propagated in the
> name of safety and good performance.
That makes me think of using red cockpit lights at night.
Every pilot knows that red light does not ruin night vision as much as white light, right?
But is that really true? Are builders installing red lights for naught?
Is this another old wives tale that never dies?
Dim red lights are used in camera film dark rooms. So if red lights are good for film, they must be good for our eyes too, or so the reasoning goes.
What are the physics?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505856#505856
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C. Stone (RV8iator) |
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david(at)carter.net
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| Posted: Mon Jan 31, 2022 10:40 am Post subject: Wiring Best Practices? (An anecdotal follow-up) |
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This older thread on VAF https://vansairforce.net/community/showthread.php?t=64051&page=3 mentions interesting findings from the Air Force Night Vision Research Lab.
Key points:
Cool White: White was preferred by 2 of the experts, the 3rd chose green 1st and white 2nd. Cool white encompasses the scotopic (night vision)sensitivity peak of 507nm while providing the benefit of full color readability on maps etc. The Air Force has established cool white as a MILSPEC for ambient cockpit lighting due to emergency procedure concerns. Dimmed down low everyone said that cool white would be fine for night vision.
Green lights: Scotopic (night vision) is most sensitive to light of 507nm wavelength which is an aqua green. This means that with green light you can dim the lights to a greater degree while still perceiving objects. Practically this means better night vision, maintaining pupil dilation and reduced reflections in our cockpit.
Red/orange: The old red goggle adage has lost its fame. Yes red minimizes the bleaching of rodopsin which is important for night vision. But Red lighting is another matter because we lose red on charts etc. Green minimizes rodopsin bleaching while maximizing sensitivity.
Blue: This was unanimously the worse color choice. Blue also messes with reds/orange making them shades of grey. But Blues greatest detractor is that as the shortest wavelength of visible light it is easiest to refract. This means those with corneal scars from PRK/LASIK or scratches on glasses will aggravate glare under blue light. This also means the possibility of increased reflections as we need to have them turned up alittle higher than the other colors or white.
Wavelength of 5050 LEDs by color:
Cool white ? 6,000k-7000k which encompasses all vivible spectrums
Blue ? 465-470nm
Red ? 625-630nm
Green ? 515-520nm
---
David Carter
david(at)carter.net (david(at)carter.net)
On Mon, Jan 31, 2022 at 12:40 PM Christopher Cee Stone <rv8iator(at)gmail.com (rv8iator(at)gmail.com)> wrote:
| Quote: | For very low levels of intensity (scotopic vision), the sensitivity of the eye is mediated by rods, not cones, and shifts toward the [url=https://en.wikipedia.org/wiki/Violet_(color)]violet[/url], peaking around 507 nm for young eyes; the sensitivity is equivalent to 1699 lm/W[9] or 1700 lm/W[10] at this peak. (wikipedia)
For low light illumination ideally we would illuminate with a source of 507 nm.
[img]cid:ii_kz2z4pkr1[/img]
...Chris
On Mon, Jan 31, 2022 at 8:12 AM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
> Folks who pass along various and sundry admonitions
> for 'avoiding problems' are offering the ideas
> in good faith. But it can be difficult to separate ol'
> hangar tales and legends from good physics. There
> are plenty of talented engineers and technicians
> who are victims of poor advice propagated in the
> name of safety and good performance.
That makes me think of using red cockpit lights at night.
Every pilot knows that red light does not ruin night vision as much as white light, right?
But is that really true? Are builders installing red lights for naught?
Is this another old wives tale that never dies?
Dim red lights are used in camera film dark rooms. So if red lights are good for film, they must be good for our eyes too, or so the reasoning goes.
What are the physics?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505856#505856
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user9253
Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan
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| Posted: Mon Jan 31, 2022 1:09 pm Post subject: Re: Wiring Best Practices? (An anecdotal follow-up) |
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The link in the above post takes one to the thread.
This link below takes you to the specific post about Air Force night lighting research:
https://vansairforce.net/community/showpost.php?p=479679&postcount=23
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cluros(at)gmail.com
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| Posted: Mon Jan 31, 2022 4:21 pm Post subject: Wiring Best Practices? (An anecdotal follow-up) |
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It really depends on what you want to see. If you're dealing with paper checklists and especially paper maps, you're far better off with white since you'll need less light to see clearly. On the other hand if you are using a tablet for mapping and an EFIS for flight and engine instruments, then red light will be better for night vision while identifying switches, finding lost pens, etc.
On our Super Rebel we went with white light under the lip of the dashboard to provide flood lighting for reading maps and checklists and also illuminate panel switches. Testing revealed that even at the dimmest setting there was far more light than desirable. I didn't think it would be a problem since we can just turn the lights off when not needed and turn them on again when flipping switches but then I couldn't find the bloody dimmer switch in the dark. Might place some glow in the dark tape or something around that switch or reduce the number of lights.
Also do yourself a favour and place as bright a light as possible in the baggage compartment for loading and unloading. Don't place it on the battery bus.
On Mon, Jan 31, 2022 at 1:15 PM user9253 <fransew(at)gmail.com (fransew(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>
The link in the above post takes one to the thread.
This link below takes you to the specific post about Air Force night lighting research:
https://vansairforce.net/community/showpost.php?p=479679&postcount=23
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=505865#505865
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="noreferrer" target="_blank">https://matronics.com/contribution
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