Black or White?
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Black or White?
I'm about to have an argument with someone about aircraft fuselage colours. Before I foolishly start offering to bet money on the matter, can anyone explain the significance of Concorde's white fuselage versus the black fuselages used by other (military) high-speed aircraft?
What are the advantages of painting the fuselage black (a better emitter of heat) against white (a better reflector) ?
Does the heat generated by skin/air friction have to be considered at all?
Thanks
What are the advantages of painting the fuselage black (a better emitter of heat) against white (a better reflector) ?
Does the heat generated by skin/air friction have to be considered at all?
Thanks
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I think the military adopted black as this aids conspicuity, something more significant for low-flying jets and trainers, than a commercial transport aircraft.
But I'll stand corrected......
GQ
But I'll stand corrected......
GQ
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Could'nt agree more GQ. The military used to paint their training A/C yellow but changed a few years to black as no body could see them.
Often see Hawks flying around looking tres cool in Jet Black.
Often see Hawks flying around looking tres cool in Jet Black.
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The only plane that can compete in a pissing contest with Concorde is the SR-71. It's black surface helps reduce temperature and maybe helps reduce radar returns. Maybe Concorde could use a bit of cooling but not at the expense of looking non-cool on the ground.
It's black surface helps reduce temperature
Stealth aircraft (including the SR-71) are painted black because they fly around at night (you are not as stealthy if people can see you.) Training military aircraft are painted in hi-vis paint, operational aircraft are painted in low-vis paint. The decision for what constitutes those standards are probably made by some beancounter who can get a cheap deal of 20,000 litres of "midnight black".
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.. at the risk of starting a punchup, I have to concur with the earlier post by TES ...
Energy absorption and radiation has to do with electron activity .. that incomprehensible quantum mechanics thing with which we confused ourselves mightily as undergraduates ...
The basic consideration is one of electron mean free paths ... in a material with short distances between atomic level interactions there will be a more effective energy transfer between radiation and lattice energy - both ways. It follows that a material which is a good absorber of EMR will also be a good emitter. In the final analysis, black is both the best absorber and emitter ...
If you are really into brain strain (PPRuNe physicists and mathematicians excluded - and we do actually have a few), dig out a physics textbook and wade through the stuff on blackbody radiation curves. Names like Maxwell, Planck and Wein figure prominently .... as will lots of exponential and quantum equations .... all good fun .. I guess ...
Energy absorption and radiation has to do with electron activity .. that incomprehensible quantum mechanics thing with which we confused ourselves mightily as undergraduates ...
The basic consideration is one of electron mean free paths ... in a material with short distances between atomic level interactions there will be a more effective energy transfer between radiation and lattice energy - both ways. It follows that a material which is a good absorber of EMR will also be a good emitter. In the final analysis, black is both the best absorber and emitter ...
If you are really into brain strain (PPRuNe physicists and mathematicians excluded - and we do actually have a few), dig out a physics textbook and wade through the stuff on blackbody radiation curves. Names like Maxwell, Planck and Wein figure prominently .... as will lots of exponential and quantum equations .... all good fun .. I guess ...
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Black surfaces absorb heat - they are most definitely not "a better emitter" of heat!
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Entering dodgy ground here but here goes....
I thought black was both a good heat absorber and emmitter.
White is a heat reflector. It neither absorbs or emmits heat as efficiently as black.
Concorde is painted white to reduce heat buildup. It must be fairly critical because when the BA fleet was repainted in that Grey and blue scheme they couldn't do concorde that colour (perhaps Bellepheron can confirm this). But as I write I am reminded they painted an airfrance concorde in Pepsi colours (blue). Did it fly??
Coincidentally gliders are painted white because it reduces the breakdown of the gel coat by the sun. They reckon if they painted them black they would degrade quicker. Wing tips usually have red flashes on them to make them easier to spot but they are limited in how much they can apply.
As for conspicuity black does seem to work well. You can see the hawks much more clearly both against sky and ground. Its ironic the RAF have taken that long having gone through all of the raspberry ripple, blue/yellow, silver/yellow colour schemes to come up with black. The only catch is the plane gets incredibly hot after standing in the sun.
Hope this helps.
I thought black was both a good heat absorber and emmitter.
White is a heat reflector. It neither absorbs or emmits heat as efficiently as black.
Concorde is painted white to reduce heat buildup. It must be fairly critical because when the BA fleet was repainted in that Grey and blue scheme they couldn't do concorde that colour (perhaps Bellepheron can confirm this). But as I write I am reminded they painted an airfrance concorde in Pepsi colours (blue). Did it fly??
Coincidentally gliders are painted white because it reduces the breakdown of the gel coat by the sun. They reckon if they painted them black they would degrade quicker. Wing tips usually have red flashes on them to make them easier to spot but they are limited in how much they can apply.
As for conspicuity black does seem to work well. You can see the hawks much more clearly both against sky and ground. Its ironic the RAF have taken that long having gone through all of the raspberry ripple, blue/yellow, silver/yellow colour schemes to come up with black. The only catch is the plane gets incredibly hot after standing in the sun.
Hope this helps.
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BA did indeed leave the Concorde fleet white due to heat buildup penalties. From what I remember at the time BA had no issue with dark colours on the upper surfaces, but dark colours underwing and on the lower fuselage were a definite no no.
The AF Pepsi Concorde did indeed fly, but had heavy speed penalties (don't think they were actually allowed to go over Mach 1) applied due to overheating concerns.
The AF Pepsi Concorde did indeed fly, but had heavy speed penalties (don't think they were actually allowed to go over Mach 1) applied due to overheating concerns.
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Although the Hawk can just get supersonic (in a Hawker Siddely shallow dive) I hardly think it counts in the 'high speed' area Konkordski is asking about, an area about which I know nothing.
However, I recall that it took a very clever psychologist to convince the forces that dark was a better colour for conspicuity. So, while I am almost as synical as checkboard, the black colour was used on training aircraft as it is proven to aid conspicuity and one can achieve visual contact at longer range.
Akin the glider argument, there was some discussion whether the Slingsby Fireflys would overheat in the sun on the ground and cause damage to the composite structure, but they must have sorted it as I have seen these black as well (unless the weather in Lincolnshire made that argument defunct as well!).
Regards.
av8er
However, I recall that it took a very clever psychologist to convince the forces that dark was a better colour for conspicuity. So, while I am almost as synical as checkboard, the black colour was used on training aircraft as it is proven to aid conspicuity and one can achieve visual contact at longer range.
Akin the glider argument, there was some discussion whether the Slingsby Fireflys would overheat in the sun on the ground and cause damage to the composite structure, but they must have sorted it as I have seen these black as well (unless the weather in Lincolnshire made that argument defunct as well!).
Regards.
av8er
TMFKA & DW11
I had no involvement with it, but I've read that the Pepsi Concorde did go supersonic, and that limits only applied above Mach 1.7.
You can click here if interested in further information.
ORY-LGW-DUB-ARN-CDG-BEY-DXB-JED-CAI-LIN-MAD-ORY was not a typical trip line on the Concorde fleet!
Regards
Bellerophon
With acknowledgements to Alain Mengus for information from his articles
I had no involvement with it, but I've read that the Pepsi Concorde did go supersonic, and that limits only applied above Mach 1.7.
You can click here if interested in further information.
ORY-LGW-DUB-ARN-CDG-BEY-DXB-JED-CAI-LIN-MAD-ORY was not a typical trip line on the Concorde fleet!
Regards
Bellerophon
With acknowledgements to Alain Mengus for information from his articles
Hmm, I typed in the original comment thinking about the absorbtion of black surfaces, and that a black surface will absorb more radiation than a white one, so I wasn't really thinking about what I was saying. Mea Culpa! I stand corrected. 
Here is how Encyclopedia Britannica puts it:
Here is how Encyclopedia Britannica puts it:
...The rate at which a body radiates (or absorbs) thermal radiation depends upon the nature of the surface as well. Objects that are good emitters are also good absorbers (Kirchhoff's radiation law). A blackened surface is an excellent emitter as well as an excellent absorber. If the same surface is silvered, it becomes a poor emitter and a poor absorber.
