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I stumbled upon the Appleman-chart, that makes it possible to predict the formation of contrails.

How do I use this chart?

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  • 5
    $\begingroup$ This is so good it deserves to be a self-answered question 👌 $\endgroup$ – ymb1 Jan 21 '18 at 12:10
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    $\begingroup$ A well researched question. $\endgroup$ – mins Jan 21 '18 at 15:15
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    $\begingroup$ Very nice! Thank you for sharing this useful procedure and the sources used. Something more on my agenda -- a contrail predictor program or map. $\endgroup$ – not2qubit Feb 6 '18 at 13:30
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    $\begingroup$ @not2qubit Yeah, it's an incredibly interesting topic. But just be aware of one thing: During my further research, it came out, that the Appleman-chart is made for low-bypass-engines. Jeffrey Peters has made new charts for high-bypass-engines. Here is his work. The new charts begin on page 20 (Chrome), respectively page 14 of the document. $\endgroup$ – Noah Krasser Feb 6 '18 at 13:47
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    $\begingroup$ @Pilothead Didn't know this happened, I moved it. $\endgroup$ – Noah Krasser Jun 4 '18 at 20:36
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First of all, the Appleman-chart itself:

Appleman-Chart

Source

Now, let's say we want to know if contrails can form at FL340 at my position, a pretty standard cruise flight level. Because flight levels are standard pressure, we can easily look up the pressure, corresponding to the flight level.

100 ............................................ F530 
150 ............................................ F450 
200 ............................................ F390 
250 ............................................ F340 
300 ............................................ F300 
400 ............................................ F240 
500 ............................................ F180 
600 ............................................ F140 
700 ............................................ F100 
850 ............................................ F050 

Source

Ok, we've got the pressure, it's 250 hPa.

Now we need the temperature at this flight level. I am using a winds aloft chart for this.

Winds aloft chart

Source

Let's just take a value from what's nearest to my position, -56 degree Celsius in this case.

Now we can look this up on the chart.

Appleman-Chart

Ok, looks like we've got contrails to see. But am I missing something?

I quickly tried to check the result, by looking out of the window. I expected following:

  • Contrail existing
  • Very short contrail. I looked up relative humidity for that flight level as well. It's very low, only 3 to 1 percent. And the lower, the humidity, the faster a contrail sublimes and fades away.

Here's the data for the humidity:

-------------------------------------------
PRES   HGHT   TEMP   DWPT   RELH   MIXR   
hPa     m      C      C      %    g/kg    
-------------------------------------------
258.0   9699  -54.9  -79.3    3   0.00 
250.0   9900  -54.3  -80.3    3   0.00   
222.0  10665  -52.1  -82.1    2   0.00   
200.0  11340  -52.9  -83.9    1   0.00   
198.0  11404  -53.0  -84.0    1   0.00  
185.0  11839  -53.4  -84.4    1   0.00  
150.0  13180  -54.7  -85.7    1   0.00  

Source

So, I first looked on flightradar to search a plane I could possibly spot from my position.

flightradar24

Picture from flightradar24.com

UAE72 is at FL390, what is a standard pressure level of 200, so we've got a relative humidity of 1%.

Now the look out of the window:

UAE72

As we can see, it's exactly as expected.

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