Red dome or reading light
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Red dome or reading light
In the "human factors" section of most private pilot textbooks, it states that red lights preserve night adaptation the best, hence aircraft are fitted with red filters on reading lights.
The red light is almost ubiquitous on GA airplanes, but I haven't seen Airbus, Boeing or Douglas install a red light in the cockpit. Does anyone know why that is so?
The red light is almost ubiquitous on GA airplanes, but I haven't seen Airbus, Boeing or Douglas install a red light in the cockpit. Does anyone know why that is so?
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This has been a topic of discussion since after the war when a researcher concluded red light preserved night vision.
In the 1980s, it was discovered in nominally lighted airspace, (moon or light pollution near cities) coupled with the enhanced visibility provided by Strobe lights made the difference still measurable, but negligible on night adapted vision. Another factor is how red light makes focusing more difficult, contrast is lower, and eyestrain increases compared to cockpits lit with white light.
The final nail in the coffin of red cockpit lighting came about with the advent of glass cockpits, where it was discovered red cockpit lighting interfered with a pilot's ability to discern colors presented on the (then) new glass displays.
All that said and done, for airborne activities that require the absolute highest preservation of night vision adaptation, red is the preferred wavelength.
In the 1980s, it was discovered in nominally lighted airspace, (moon or light pollution near cities) coupled with the enhanced visibility provided by Strobe lights made the difference still measurable, but negligible on night adapted vision. Another factor is how red light makes focusing more difficult, contrast is lower, and eyestrain increases compared to cockpits lit with white light.
The final nail in the coffin of red cockpit lighting came about with the advent of glass cockpits, where it was discovered red cockpit lighting interfered with a pilot's ability to discern colors presented on the (then) new glass displays.
All that said and done, for airborne activities that require the absolute highest preservation of night vision adaptation, red is the preferred wavelength.
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In our 737s we had a detachable reading light at each pilot station that could be switched to red. However, quite honestly we rarely used it except if needed during approaches.
From my days peering into the night sky, red light did not destroy your adapted night vision that can take 15-20 minutes to acquire, whereas other colours did. Kind of like a dark room I guess.
In a 172 with steam driven instruments, a red light might useful. When there are several 8inch square multi colour PFD/ND displays in front of you I don't think your eyes are truly ever night adapted so a red light would be rather pointless IMHO.
In a 172 with steam driven instruments, a red light might useful. When there are several 8inch square multi colour PFD/ND displays in front of you I don't think your eyes are truly ever night adapted so a red light would be rather pointless IMHO.
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In the airline world, pilots seldom have to really land in the "dark". With all the approach and runway lights, normal (but dimmed) cockpit lighting works just fine, especially with the previously-mentioned multicolor displays.
OTOH, the pilot of a GA airplane with minimal instrumentation that is landing on a minimally-lit airfield will need night adaptation to safely land. The red cockpit lighting will be an advantage there.
When the Navy started using night vision goggles in the late 80s and early 90s, there was a LOT of RDT&E to get the right combination of color and intensity of [green] lighting to replace the old red lights - which were incompatible with NVGs - and retain safety for night carrier ops.
OTOH, the pilot of a GA airplane with minimal instrumentation that is landing on a minimally-lit airfield will need night adaptation to safely land. The red cockpit lighting will be an advantage there.
When the Navy started using night vision goggles in the late 80s and early 90s, there was a LOT of RDT&E to get the right combination of color and intensity of [green] lighting to replace the old red lights - which were incompatible with NVGs - and retain safety for night carrier ops.
Why have night vision if you never look out of the cockpit anyway.....?
In the middle of the night I prefer a bit of illumination in the cockpit and some conversation to keep me awake...
I think Boeing installed that very practical wander light in everything since the B17. If it ain't bust...
Hang the night vision... give me white anytime. Besides, you can wind them down so low they almost look red...
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Besides, you can wind them down so low they almost look red...
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When not focused on anything in particular the eyes naturally focus about 9" the other side of the windscreen.
The USAF did a lot of testing about night flying, including pre flight meals and rest and in flight cockpit lighting. Best combination to give best night sight during climb and descent was flight deck dimmed, during cruise the more light the better to reduce fatigue, measured at up 75% less in some cases.
The USAF did a lot of testing about night flying, including pre flight meals and rest and in flight cockpit lighting. Best combination to give best night sight during climb and descent was flight deck dimmed, during cruise the more light the better to reduce fatigue, measured at up 75% less in some cases.
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Thanks for the info guys. I flew one GA plane with white lighting. Much preferred it to the annoying red light. To preserve night vision, I just turned them down...
Agreed on lights on during cruise at night. Much easier to stay alert. We're not doing much "outside flying" at cruise anyway.
Agreed on lights on during cruise at night. Much easier to stay alert. We're not doing much "outside flying" at cruise anyway.
There are two issues for night vision, pupil size and retinal sensitivity. And it's only the second one that is really the night adaptation and is not affected by the red light.
First is pupil size. Bright lights shrink the pupil to let less light in. After a time in the dark your pupils expand to let more light in. Which is why when you turn the light off in your room at night you can't see much for a couple of minutes or so. And conversely why when someone turns the normal light on in the middle of the night it is wincingly bright. This is the pupil taking time to adjust. This process is just about the pupil trying to meter the strength and brightness of the light, nothing more.
Secondly is retinal sensitivity. After a few minutes of darkness, the proteins in the rods in the retina make it more sensitive to light, allowing more to be seen. This process to fully develop takes about half an hour. Exposure to long wavelength light (red) doesn't reset this process. So dim red light will preserve this night vision adaptation of your retina.
Turning your cockpit lights down will keep your pupil dilated and let a good amount of light in and help you see outside (the outline of a towering cu against the background of stars for example).
But if there are any wavelengths of light not in the red spectrum, (eg EFIS) then the rods in your retinae won't fully function in low light.
In practice pupil size gives a great improvement, the retinal sensitivity is the icing on the sake.
First is pupil size. Bright lights shrink the pupil to let less light in. After a time in the dark your pupils expand to let more light in. Which is why when you turn the light off in your room at night you can't see much for a couple of minutes or so. And conversely why when someone turns the normal light on in the middle of the night it is wincingly bright. This is the pupil taking time to adjust. This process is just about the pupil trying to meter the strength and brightness of the light, nothing more.
Secondly is retinal sensitivity. After a few minutes of darkness, the proteins in the rods in the retina make it more sensitive to light, allowing more to be seen. This process to fully develop takes about half an hour. Exposure to long wavelength light (red) doesn't reset this process. So dim red light will preserve this night vision adaptation of your retina.
Turning your cockpit lights down will keep your pupil dilated and let a good amount of light in and help you see outside (the outline of a towering cu against the background of stars for example).
But if there are any wavelengths of light not in the red spectrum, (eg EFIS) then the rods in your retinae won't fully function in low light.
In practice pupil size gives a great improvement, the retinal sensitivity is the icing on the sake.
727's 737's and 744's had detachable Red/White reading lights. I believe they were called Roving lights?
Maybe that was a name we used??
Anyway they were detachable and had a long cord like a telephone cord, they were quite handy to shine on the wipers to look for ice. ( saved pulling out the torch )
New Aircraft don't have them, so now the easiest and quickest thing to use is the iPhone torch
Maybe that was a name we used??
Anyway they were detachable and had a long cord like a telephone cord, they were quite handy to shine on the wipers to look for ice. ( saved pulling out the torch )
New Aircraft don't have them, so now the easiest and quickest thing to use is the iPhone torch
ACMS, as mentioned before that was the Grimes light.
Before the Sea King, all RN helicopters had red instrument lighting but the SK came with adjustable white lighting throughout the cockpit. True to military fashion, the standby compass, the E2B, was remustered as the E2C when the colour was changed!
Regardless, the carriers went to red lighting throughout for night flying and we continued to stumble around in the gloom until we got airborne and returned to normality. Being young and bulletproof it never seemed much of an issue, especially when returning to Mother in darken ship state only to see her from 25 miles away as an F4K lit up the reheat on the cat!
Before the Sea King, all RN helicopters had red instrument lighting but the SK came with adjustable white lighting throughout the cockpit. True to military fashion, the standby compass, the E2B, was remustered as the E2C when the colour was changed!
Regardless, the carriers went to red lighting throughout for night flying and we continued to stumble around in the gloom until we got airborne and returned to normality. Being young and bulletproof it never seemed much of an issue, especially when returning to Mother in darken ship state only to see her from 25 miles away as an F4K lit up the reheat on the cat!
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One of the reasons the USAF uses blue-green filters on their cockpit lights.
If you're used to red cockpit lights at night, the blue-green NVG lights take some getting used to. In some cases the rheostats may have to be replaced so the brightness can be adjusted better. Installing the NVG compatible light systems in all airplanes of a type would make the transition easier.
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I recall the red light was quite handy when flying the Twotter. The instruments lights could be dimmed to the right amount, but for doing anything else that looking at the instruments the red light fell in just fine. Nowadays on the bus I don't think of it as that necessary as it was on the Otter. The screens can be dimmed to the right amount and the light on the little coffee tray it's good enough to do everything else. If anything it's the newer LED tray lights that it's a bit annoying to use because they're so bright. I kinda like the conventional lights a bit better for night flying.
FWIW, in a clear/bright night, the night vision does serve me up a bit to combine my eye analysis with the radar to avoid an isolated CB or something like that. Sometimes it's not strong enough to get picked up by the radar but one can see it's shape and you can take a guess of how to avoid for mere turbulence-avoidance purposes
FWIW, in a clear/bright night, the night vision does serve me up a bit to combine my eye analysis with the radar to avoid an isolated CB or something like that. Sometimes it's not strong enough to get picked up by the radar but one can see it's shape and you can take a guess of how to avoid for mere turbulence-avoidance purposes