The Need for Speed
Knots, Longitudinal Lines & Paper Maps
I get geeky about math stuff. Flying an airplane is basically math in motion. Four forces constantly interact on an aircraft in flight. They are thrust vs drag and lift vs gravity. With high-performance combat aircraft flying, a pilot uses these forces to accomplish the mission or win a dogfight. But those forces are not the point of today’s post. I want to talk about speed and how it gets measured.
To paraphrase a line from a Bill Cosby skit…. “What’s a knot?”
A knot is shorthand for nautical mile per hour. A nautical mile is about 6,076 feet (officially 1,852 meters), which is about 15% longer than a statute mile. According to Wikipedia, a nautical mile is one minute of latitude at the equator. I was taught that it was one minute of longitude anywhere. A longitudinal line goes through both poles and is divided into the 360 degrees of a circle. All longitudinal lines have the same length. A minute of longitude is one-sixtieth (1/60) of a degree.
Paper Maps
In my flying days, this was actually of practical value. Flight planning was done on paper maps. You could quickly measure the distance between two points by laying the edge of a piece of paper to connect the points, mark them on the edge of the paper, and then lay the paper along a longitude line on the map.
The scale of maps we used had the minutes of longitude marked. Our ground attack tactics consisted of a low-level ingress route to the target, with a popup attack to drop conventional bombs and not frag ourselves. The flying was very similar to what they did in Top Gun: Maverick.
Low-Level Routes
A low-level route consisted of 15 to 20 nautical mile legs with recognizable turn points. With the mapped-out ground references, a low-level route could be flown even if the onboard GPS lost its way. The routes were flown at 300 feet above the ground (AGL).
A low-level route would be flown at 480 knots ground speed. That maths out to eight miles a minute, allowing us to quickly do a backup check on the map strapped to my leg. The final leg, IP to target, would be flown at 540 knots, or nine miles a minute.
The details are a topic for another day, but all ground attack missions were flown with two or four-ship formations.
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