Military Flight Aptitude: Brush Up on the Metric System
So, what’s so great about the metric system? The answer is simple, just like the metric system itself. In the metric system, everything operates on a scale of ten, unlike the U.S. customary system — the system you’re probably used to — which is based on a scale of . . . well, who knows.
The simple fact is that most folks in the United States know little about the metric system. You were probably exposed to it during your high-school and college math and science classes, but if not, the following sections have you covered.
Units and abbreviations
Forget about feet, pounds, and Fahrenheit. The metric system uses a different system of units than you may be used to. The following list showcases some common metric units:
Seconds (s): The second is the main metric unit of time.
Meters (m): Meters are the main metric unit of distance.
Degrees Celsius or centigrade (ºC): These degrees are the metric unit of temperature in everyday use.
Note: It says in everyday use because temperature in the metric system is officially measured in Kelvin (K). You find the temperature in Kelvin by adding 273 to the temperature in degrees Celsius. Temperature in Kelvin is useful when describing things in term of absolute zero (0 degrees Kelvin is the coldest temperature possible).
Kilograms (kg): Kilograms are the metric unit of mass. The first time you order something from a deli that uses the metric system, be careful!
Hertz (Hz): The metric unit of frequency is hertz. If something happens once per second, it happens with a frequency of 1 hertz.
Joule (J): The Joule is the metric unit of work/energy.
Pascal (Pa): Pascals are the metric units of pressure. There are 101,325 pascals (101.325 kPa) in 1 atmosphere (1 atm). Regardless, inches of mercury is the standard measure of barometric pressure throughout the world aviation community. One inch of mercury is equal to 3,386.389 pascals at 0 degrees Celsius.
Taking the temperature: Going from Fahrenheit to Celsius and back
The degree Fahrenheit (ºF) is the U.S. customary scale of temperature measurement; the freezing point of water is 32 degrees, and the boiling point is 212 degrees. The formula for converting Fahrenheit to Celsius is
ºF = ºC x 9/5 + 32
The degree Celsius is an easy system of measurement with the freezing point of water at 0 degrees and the boiling point at 100 degrees. (Of course, pressure has some impact on these figures, but these base figures are for standard pressure.) The formula for converting Celsius to Fahrenheit is
ºC = (ºF – 32) x 5/9