My favorite things

kids and planes

Knots are not nautical

“Why do we use nautical miles?” The student pilot and I were discussing cross country flight planning. I gave him the only answer I could. “I don’t know, but I will try to find out.”

It seems like we have quite a few words in aviation that refer to boats, so I decided to make a list of aeronautical terms. Stop right there: where did that word aeronautical come from? According to the Miriam Webster dictionary, the term aeronautical was first used about 1824 and is a combination of aero + nautical. Nautical: of, relating to, or associated with seamen, navigation, or ships was first used around 1552 and comes from Greek nautikos meaning sailor. Aero, comes from Latin avis, and has to do with birds (think aviary). Just like simple math, if we put them together it equals: of, relating to, or associated with airmen, air navigation, or airships.

When you have a new thing, sometimes you have to invent a new word. Two year olds are great at this. A two year old I knew invented the word flysmacker. Shakespeare kept on going after he was two and invented over 3000 words. . . including aerial, but that is another story altogether. Back in the 1800s when folks were getting serious about trying to leave the terra firma below, they had to invent some new terms. Since navigation by sea was doing quite well at the time, it made logical sense to go from the blue below to the blue above.

Here are just a few of the terms we use in aviation that were adapted from navigation:

Term	Nautical	Aeronautical
Abeam	On the beam, a bearing at right angles to the centerline of the ship's keel	Ninety degrees to the right or left of the aircraft track
Aft	Toward the stern or back of the ship	Toward the tail of the aircraft
Aloft	In the rigging of a sailing ship; above the ship's uppermost deck, high overhead	Above the ground; for example, winds aloft are forecast at altitudes from 3000 MSL to 39000 MSL
Beacon	A lighted or unlighted aid to navigation attached directly to the earth’s surface; a lighthouse is one example of a beacon	A navigation aid that emits flashes of white and colored light to indicate the location of an airport or landing area
Cabin	An enclosed room on the deck	The part of the aircraft that is enclosed for passengers, crew, or cargo
Chart	A map used in the navigation of the ocean and shorelines including hazards, currents and depths of the ocean floor	A map used in air navigation containing all or part of the topography, hazards, navigation aids, routes and airports
Pilot	A navigator; a knowledgeable person qualified to navigate a vessel through difficult waters, for example, a harbor pilot; the person who is responsible for the safety of the vessel	A knowledgeable person qualified to navigate an aircraft through the skies; Pilot in Command: the person who has final authority and responsibility for the operation and safety of the flight
Pitch	A ship's motion causing the fore and aft ends to rise and fall repetitively.	The movement of the aircraft around its lateral axis: the nose will pitch up and down along the flight path.
Port	1. A place where ships may ride secure from storms; usually sheltered from open water 2. The left-hand side of the ship facing forward: marked with a red light at night	1. Airport: A place where an aircraft lands and takes off; a place where an aircraft can be safely tied down or hangered 2. The aircraft has a red navigation light on the left wing tip
Rudder	A large blade or vertical surface at the rear of a ship which is connected to the helm and used to steer	A moveable vertical surface on the tail of an airplane used to control direction and yaw
Starboard	The right-hand side of the ship facing forward: marked with a green light	The aircraft has a green navigation light on the right wing tip
Trim	An advantageous set of the ship in the water or set of the sails in the wind	An advantageous balance of control forces in flight most commonly for pitch
Wake	Turbulence behind and below a ship in the water	Turbulence behind and below an aircraft whenever the wing is producing lift
Wash	The waves created by a ship.	The movement of air behind any airfoil, for example, upwash, downwash, prop wash
Yaw	A ship's rotational motion about the vertical axis, causing the fore and aft ends to swing from side to side through the water.	An aircraft’s rotational motion around the vertical axis, causing the nose and tail to swing from side to side in the air.

You may have noticed that the above list does not explain why we use nautical miles; which was the student’s original question. This subject took a little more research and includes two of our most well used terms in aviation. The nautical mile is approximately the distance across one minute of longitude when measured at the equator. It is a distance used by sailors who were going strong exploring the world in the 15^th and 16^th centuries. However the distance of 6076.12 feet or 1852 meters wasn’t standardized until the 20^th century.

Along come airplanes at the start of the 20^th century. First we flew over land. No problem, we can use a road map and statue miles or kilometers. But when we started flying over water, what to do? We had to use nautical charts and decide how long it would take us to get somewhere (without running out of fuel of course) using nautical miles.

Here is the very strange part. How do aviators measure the speed at which they fly those nautical miles? We measure in knots, which sounds like nautical, but is not. However knots and one of a pilot’s most useful records comes from the same device. Back to the 1500s. It might be useful to know how fast your ship is traveling through the big blue ocean. So you drop a piece of wood attached to a rope, or a “log” off the front of the ship and record in seconds or minutes or hours how long it takes for the ship, which is moving, to pass the log, which is just sitting there. Then a clever sailor thought: Why don’t we simply tie knots in our rope at evenly spaced lengths, throw the log off the back of the ship and see how often the knots go out to sea. The knots were 7 fathoms or 42 feet apart and time could be measured with a 30 second sand hourglass. The rest is history. Now sailors and pilots alike measure the speed of our craft in knots. Then the captain or first mate or Number 1 made the sailor keep a record of the log dragging the knotty rope out behind our ship. Our sailor needed a book to write down a record of the speed at which the log was being left behind, and presto, the logbook was born.

Finally, one more aviation term that does not come from the sea but from geometry. When inventors were hard at work trying to be the first to make powered flight, the term flying machine was quite popular. Hence the title of one of my favorite old movies, Those magnificent men and their flying machines. The airplane, in contrast to the popular balloon, referred to a thing that travels through the air at one level altitude or plane (think flat surface):

In Paris, M. Adar is said to have constructed a flying machine by which he has raised himself 60 feet in the air and flown about 900 feet in a straight line, his flying machine is a monstrous thing, approximately like a bat. . .M. Mouillard of Algiers claims to have flown short distances with his adjustable “aeroplane” a flat surface like the underparts of a bird when soaring with rigid wings. New York Times January 3, 1892.

Now, the cross country flight log is complete. The nautical miles are measured. The navigation lights are on. As you point the nose of your airplane up into the deep blue sky, remember what you owe to the sailors of the deep blue sea.