Implement MIL-HDBK-310 climatic data

**Library:**Aerospace Blockset / Environment / Atmosphere

The Non-Standard Day 310 block implements a portion of the climatic data of the MIL-HDBK-310 worldwide air environment to 80 km (geometric or approximately 262,467 feet geometric) for absolute temperature, pressure, density, and speed of sound for the input geopotential altitude.

The COESA Atmosphere Model, Non-Standard Day 210C, and Non-Standard Day 310 blocks are identical blocks. When configured for COESA Atmosphere Model, the block implements the COESA mathematical representation. When configured for Non-Standard Day 210C, the block implements MIL-STD-210C climatic data. When configured for Non-Standard Day 310, the block implements MIL-HDBK-310 climatic data.

The COESA Atmosphere Model block port labels change based on the input and
output units selected from the **Units** list.

All values are held below the geometric altitude of 0 m (0 feet) and above the geometric altitude of 80,000 meters (approximately 262,467 feet). The envelope atmospheric model has a few exceptions where values are held below the geometric altitude of 1 kilometer (approximately 3,281 feet) and above the geometric altitude of 30,000 meters (approximately 98,425 feet). These exceptions arise from lack of data in MIL-HDBK-310 for these conditions.

In general, temperature values are interpolated linearly, and density values are interpolated logarithmically. Pressure and speed of sound are calculated using a perfect gas law. The envelope atmospheric model has a few exceptions where the extreme value is the only value provided as an output. Pressure in these cases is interpolated logarithmically. These envelope atmospheric model exceptions apply to all cases of high and low pressure, high and low temperature, and high and low density, excluding the extreme values and 1% frequency of occurrence. These exceptions arise from lack of data in MIL-HDBK-310 for these conditions.

Another limitation is that climatic data for the region south of 60°S latitude is excluded from consideration in MIL-HDBK-310.

This block uses the metric version of data from the MIL-STD-310 specifications. Certain data within the envelope are inconsistent between metric and English versions for low density, low temperature, high temperature, low pressure, and high pressure. The most significant differences occur in the following values:

For low density envelope data with 5% frequency, the density values in metric units are inconsistent at 4 km and 18 km and the density values in English units are inconsistent at 14 km.

For low density envelope data with 10% frequency,

The density values in metric units are inconsistent at 18 km.

The density values in English units are inconsistent at 14 km.

For low density envelope data with 20% frequency, the density values in English units are inconsistent at 14 km.

For low temperature envelope data with 20% frequency, the temperature values at 20 km are inconsistent.

For high pressure envelope data with 10% frequency, the pressure values in metric units at 8 km are inconsistent.

[1] *Global Climatic Data
for Developing Military Products.* MIL-HDBK-310, Washington, D.C.: Department of
Defense, 1987.

CIRA-86 Atmosphere Model | COESA Atmosphere Model | ISA Atmosphere Model | Non-Standard Day 210C