[perpetual]

Originally Posted by MDPilot

In over 30 years of military and civilian flying, a BS in Aerospace Engineering and a Master's in Aeronautical Science, I've never heard of JSA. Give me a reference to this concept.

Hiya MDPilot

The metorological information that I am looking at is mostly from JAA publications and is based on a measurement that existed prior to the establishment of the (ISA). From what I can see is that there are quite a few "different" atmospheric model (standards) that are used for specific engineering or testing. In addition these concepts are still being taught for ATPL level theory during ground school.

I have included an example of an ATPL test question below, involving the use of differing (JSA vs ISA) atmospheric modeling along with its answer.

__________________________________________________ ____________
Question:

1.) At FL430 the temperature deviation is given as ISA +3. Express this temperature as a deviation from the Jet Standard Atmosphere.
__________________________________________________ ____________
Given answer:

ISA Temperature (43,000 ft) = - 56.5°C
Deviation from ISA = +3°C
Ambient temperature (43,000 ft) = -53.5°C
JSA temperature (43,000 ft ) = +15°C - (43 x 2°C)
= +15°C - 86°C
= -71°C
JSA temperature deviation = +17.5°C
__________________________________________________ ______________

As you can see this is one of the questions that started me thinking about how to find a particular ambient temp for a related ISA FL in the isothermal region.

Below are some links to either records, publications, or engineering data for its' use.

http://www.naples-air-center.com/pdf...k%20sample.pdf

There is another atmosphere that became popular in the 1960's, that is the Jet Standard Atmosphere. In this atmospheric model, the conditions are the same with the exception that there is no tropopause, the lapse rate being a flat 2°C per 1000ft until the stratosphere.

Here's another that speaks of a non-tropopause containing atmosphere (to an extent )

http://www.ldeo.columbia.edu/~nili/HL1998.pdf

The Charney model has no tropopause and
has nonzero PV gradients in the troposphere.

I know the topic is completely theoretical at best at this point, it was simply the question of needing to find the deviation between each model that sparked my interest further.

Anyway, based on what I wrote the first time, am I at least in the ballpark so to say as far as trying to determine the actual ambient for the given flight level?

And in closing, if this thread gets too rediculous because of it's possible pointlessness, I'll just let my interest for it die

-Perpetual