JazzRoc says the chemtrail era will end

Mick West

Administrator
Staff member
While it's quite plausible that it will end in this manner, I don't really think it's entirely imminent. We are probably talking at least ten years before anything like that could happen.
 

TWCobra

Senior Member.
Hmmm, unless contrails can be shown to have severe negative consequences, why would I re-route hundreds of miles around humid air?
 

Jay Reynolds

Senior Member.
Even if contrails were reduced to a minimum, predictive ability isn't perfect, so some would still occur. When they became rarer, a chemtrail believer would find them all the more unusual, and start the crybaby routine all over.
 

TWCobra

Senior Member.
Another reason why I have doubts is that humidity or even relative humidity has no appreciable bearing on the performance of a jet. Hence it is not measured on the aircraft and a good reason would have to be put forward to install such equipment.
 

Billzilla

Senior Member.
Another reason why I have doubts is that humidity or even relative humidity has no appreciable bearing on the performance of a jet. Hence it is not measured on the aircraft and a good reason would have to be put forward to install such equipment.

Correct, it has no real effect.
 

Lee Wilson

New Member
Hmmm, unless contrails can be shown to have severe negative consequences, why would I re-route hundreds of miles around humid air?


Another reason why I have doubts is that humidity or even relative humidity has no appreciable bearing on the performance of a jet. Hence it is not measured on the aircraft and a good reason would have to be put forward to install such equipment.


Correct, it has no real effect.


Humidity affects the way an airplane flies because of the change in pressure that accompanies changes in humidity. As the humidity goes up, the air pressure for a given volume of air goes down. This means the wings have fewer air molecules to affect as they are pushed through the airmass. Fewer molecules = less lift.
The other problem is that jet engines do not like humidity either. Jet engines are built for cold, dry air, and humid air has fewer oxygen molecules to burn per unit volume. Therefore the engine combusts a little bit less and puts out slightly less thrust. There are four factors that decrease the performance of a jet airplane - heavy, hot, high, and humid. Notice that three of those factors all have the net effect of lowering the density of the air.
So there you have it. Humidity decreases the performance of most aircraft, not only because of it's effect on the wings, but also the effect on the engines.
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http://www.physlink.com/education/askexperts/ae652.cfm
 

Lee Wilson

New Member


I doubt this would kill off the conspiracy theory, the theory's advocates will simply believe this is part of a plot to cover up the 'chemtrailing' . . . "They knew we were onto them, so they've made the chemtrails invisible . . . !"

You need to make enormous allowances for a self-sustaining worldview, a lack of evidence has rarely been a hindrance to magic thinking.
 

Mick West

Administrator
Staff member
The reason it might happen is a simple form of geoengineering. Contrail cirrus cool the earth during the day, and warm it during the night. So once a more automated ATC is in place it's quite plausible to use it as a way of modulating solar radiation forcing.

To do this, they would attempt to control contrail formation using a variety of forecasting techniques, including simply Pilot Reports of where contrails are forming, or not. If there's some on-plane humidity measurement, then that adds to the data, but it's not necessary.

Of course it's plausible that we might use this to create MORE contrails, especially in the early morning, and less only in the evening and at night.

It's a great tool (if it works) as it can be used to experiment with solar forcing in a very safe and immediately reversible manner.

But a more likely use of computerized ATC is simply to make flights more efficient, hence saving money and reducing carbon emissions.

http://www.guardian.co.uk/environment/blog/2011/dec/12/climate-change-carbon-emissions

Wouldn't it be nice if there were an easy way to slash global carbon emissions by more than 40m tonnes each year? That's a serious saving – about as much as the entire Danish economy.

What if the total impact on combatting climate change was twice as much as that figure suggests, because all that carbon would have been emitted – along with a cocktail of other pollutants – at high altitude? And what if the plan would also save huge amounts of time and money?

If that sounds too good to be true, then you probably have't met David Parkinson, the inventor and engineer on a one-man mission to drag air-traffic control (ATC) into the digital era. Parkinson believes that using computers to calculate perfectly smooth trajectories for planes could painlessly cut 8% of aviation emissions.
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It would be great if such a system could be designed with a contrail modulating capability built in, so we could at least try the experiment.
 

Billzilla

Senior Member.
Humidity affects the way an airplane flies because of the change in pressure that accompanies changes in humidity. As the humidity goes up, the air pressure for a given volume of air goes down. This means the wings have fewer air molecules to affect as they are pushed through the airmass. Fewer molecules = less lift.
The other problem is that jet engines do not like humidity either. Jet engines are built for cold, dry air, and humid air has fewer oxygen molecules to burn per unit volume. Therefore the engine combusts a little bit less and puts out slightly less thrust. There are four factors that decrease the performance of a jet airplane - heavy, hot, high, and humid. Notice that three of those factors all have the net effect of lowering the density of the air.
So there you have it. Humidity decreases the performance of most aircraft, not only because of it's effect on the wings, but also the effect on the engines.

With the effect being so small that no-one has ever noticed the difference.
 

Lee Wilson

New Member
With the effect being so small that no-one has ever noticed the difference.

No one has ever noticed ?

Type "humidity effect on aircraft performance" into Google and take a quick look through a few of the 300,000+ results . . . . oddly counter to your notion people do seem to have noticed the effect of humidity effect on aircraft performance.

In fact the general tone seems to be that the effect is 'significant', 'pronounced' and/or 'dramatic'.

You might want to share your ideas with the engineers who build longer runways in humid climates.

:)
 

solrey

Senior Member.
No one has ever noticed ?

Type "humidity effect on aircraft performance" into Google and take a quick look through a few of the 300,000+ results . . . . oddly counter to your notion people do seem to have noticed the effect of humidity effect on aircraft performance.

In fact the general tone seems to be that the effect is 'significant', 'pronounced' and/or 'dramatic'.

You might want to share your ideas with the engineers who build longer runways in humid climates.

Did you actually read any of those articles? I mean the link at the top of that search says:

Humidity also plays a part in this scenario. Although it is not a major factor in computing density altitude, high humidity has an effect on engine power. The high level of water vapor in the air reduces the amount of air available for combustion and results in an enriched mixture and reduced power.

When they say the effect is significant, they're lumping humidity together with temperature and pressure. Density Altitude, something all pilots know about, is based on temperature and pressure, humidity is not even a variable in the formula used to calculate DA. Humidity does have an effect on reducing engine performance because water vapor displaces some of the air but water vapor is at most only 4% of the atmosphere by volume so even in the worst case scenario it only reduces horsepower by a few percent. Airplanes routinely fly through rain after all and they seem to do just fine. Humidity is really only a factor when the aircraft is near it's max. takeoff weight. I think the main reason for longer runways in humid climates is because those climates are also generally hot, and heat is the primary factor in dramatically reducing lift so the plane needs more time to build up more speed before it can takeoff.
 

Trigger Hippie

Senior Member.
Shouldn't the effects of humidity on engine performance be more "pronounced" and "dramatic" at lower altitudes (where they build runways) because the air is warmer, and less so at cruise altitudes (where contrails are formed)?
 

Lee Wilson

New Member
When they say the effect is significant, they're lumping humidity together with temperature and pressure. Density Altitude, something all pilots know about, is based on temperature and pressure, humidity is not even a variable in the formula used to calculate DA. Humidity does have an effect on reducing engine performance because water vapor displaces some of the air but water vapor is at most only 4% of the atmosphere by volume so even in the worst case scenario it only reduces horsepower by a few percent. Airplanes routinely fly through rain after all and they seem to do just fine. Humidity is really only a factor when the aircraft is near it's max. takeoff weight. I think the main reason for longer runways in humid climates is because those climates are also generally hot, and heat is the primary factor in dramatically reducing lift so the plane needs more time to build up more speed before it can takeoff.

I'll bow to your better knowledge on the subject, my point was that people seem well aware of the effect, however small it may or may not be.
 

solrey

Senior Member.
No need to bow Lee, every day presents new opportunities to learn new things. I had to refresh my memory on a couple of details because it's been many years since I flew or turned a wrench on an airplane. Pilots should be keenly aware of the conditions they're flying in at all times, especially when they're at the edge of performance capabilities. Sometimes humidity can be a contributing factor to bad things happening. While I was in Liberia, on this one hot and very humid morning, a Russian cargo jet slid off the end of the runway resulting in some major structural damage but there were no injuries... except for the flight crew's pride. Turns out that the plane was at or slightly over it's max. takeoff weight and the pilots thought they barely had enough runway available based on density altitude but the slight loss in power resulted in them not quite making takeoff speed before the abort point.
 

Billzilla

Senior Member.
You might want to share your ideas with the engineers who build longer runways in humid climates.



When they say the effect is significant, they're lumping humidity together with temperature and pressure.

That's what aeroplanes 'notice' - density altitude - not humidity.
I never noticed the difference that humidity made in the twenty five years I flew.
 

TWCobra

Senior Member.
Guys, the effect of humidity on an airliner is negligible. We don't account for it at all in our performance calculations.
 

Alhazred The Sane

Senior Member.
It's been some time since I visited this forum, and the contrail-science site. Mostly because the site is so packed with nutjobs that I end up despairing of human intelligence. The nutjobs I refer to are, of course, the chemtrail lunatics - not the reasonable people who dance the dance with them. How Mick has managed to retain his level of civility is beyond me, unless he's a Buddhist. Which might explain a lot.

I should visit more. This one thread has been an education for me.

Well done gentlemen. You are bastions of sanity in a mad world world, and are to be congratulated.
 

Jazzy

Closed Account
Mick, I really liked the idea of using the effect positively. I wouldn't be surprised if we are actually using this fifty years from now. Well, I would. :)
 
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