Mintra Line / Appleman study

The Appleman study and the MINTRA line information was never designed to predict how long a trail lasted in the sky(1).
The MINTRA line came into existence from the desire of pilots to fly war planes in stealth during WW2.
The best scientists looked at the problem and realised that it was the cold air that froze the water vapour coming from the exhaust that caused the trails.
They examined the effect at different atmospheric pressures and worked out all of the parameters that are responsible for the freezing of the water vapour.
They took into account temperature, pressure and humidity because all of these factors are responsible for finding the threshold height that trails can from.
The scientists discovered that the height can vary if any one of these parameters was changed in any way.
They then produced the height that planes should not fly above for fear of making a trail. These trails will always form if the plane flies above the hight of the MINTRA line. These calculations do not consider how long a trail will last in any way whatsoever. That was not in the remit of the study as it was immaterial. Any trail was too much for this purpose. Any trail would mean the death of the pilot from enemy gunfire. Even a very small little trail that lasted a second behind the plane would mean death to the pilot.

The Appleman study (1953) also does not cover anything other than the formation of a trail(2).
It has 5 lines on the graph to show the temperature that trails can form. You have to choose the correct line according to the humidity for that day. When you have the correct line of the 5 you can then use it to find the hight that trails will always form.
These trails will always form if the plane flies above the hight of the MINTRA line because it will be cold enough.
The study stops there as this was the requirements of this study and no more.
If you wish to discover how long the trail will last in the sky when you fly your aeroplane higher than the MINTRA line, you will have to do another calculation that is only mentioned in passing near the end the "Appleman Tutorial". It says~
~"[Teachers: Advanced students could use the humidity data to forecast whether persistent contrails can form.]"~
This means:-
To predict how long a trail should last in the sky you must only consider humidity and not temperature as in the Appleman chart or the MINTRA line instructions.
The humidity must be above 100%RHice (roughly 70%RH) for a trail to last at all.
The humidity needs to be >125%RHice for a trail to spread out and thicken into cloud.
It is extremely important to get this absolutely correct as you will be legitimising dodgy chemtrails if you don't. Without doing the full calculations you will be getting the wrong answers and your calculations will always prove trails could last in the sky.

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