Is there a more specific term than 'flight line' for straight lines flown during flight?

I work for a small software startup, where its just my boss and I. Prior to this job, I had no experience with aircraft. We have a client that uses our software to fly a pattern over an area, where they fly straight for a while, turn around, and fly back over an adjacent area. They do this so that they can canvas an entire area. I sketched out what this looks like below.

      (start) ---------------------> (turn around)
)
(turn around) <---------------------
(
---------------------> (turn around)
)
(turn around) <---------------------
(
------------>    (and so on)


My boss refers to one of these straight flights as a "flight line". When I looked up the term "flight line" though, I found that it has a few different meanings all related to where the aircraft is parked or serviced on the ground.

So my question: Is there a more correct term than "flight line" that describes the patterns our client flies, which are these sets of straight lines?

• – Manu H May 13 '20 at 20:27
• Do you know what the customer calls it? Or can you ask? The pattern is specific to surveying, so it only has a name in that specific domain. – Jan Hudec May 14 '20 at 6:00

Although my aviation knowledge is not all encompassing, I would argue that you, your boss, and your software company may want to know your audience as well as possible. The same terminology can mean different things to different segments of society. For instance, uncontrolled airspace/airfield would mean something totally different to a pilot than it would mean to the media or general public.

A quick search of the Federal Aviation Regulations/Airmen’s Information Manual, the Pilots Handbook of Aeronautical Knowledge , and the Airplane Flying Handbook only garners results describing specific areas of an airfield and the personnel working there. My experience in civilian aviation and in the military is consistent with this usage. When pilots, ATC, and others in the aviation field describe an aircrafts path, they use terms such as the following:

1. Route
2. Return route
3. Round-robin route
4. Great circle route
5. Flight path
6. Leg
7. Direct leg
8. Course
9. Direct course
10. Track

The term you are probably looking for is Transect pattern consisting of transect lines.

Someone more knowledgeable might have a better term.

• Nothing technically incorrect with this answer, but for a software guy who admits to having little aviation knowledge, do you think mentioning (but not defining) great circle route does anything to answer the specific question or enhance his understanding? And when have you ever heard a pilot say that they were flying a “transect line”? – Michael Hall May 13 '20 at 22:49
• I appreciate all the terms you listed! In all fairness, my boss is pretty damn smart / knowledgeable; he definitely knows his audience. I was just wondering on my own if there was a better term. – Max May 13 '20 at 23:01
• Definitely not "flight line" though! In fact it is a timeworn joke on newbies to ask them to get you a bucket of prop wash and 10 feet of flight line. Your boss's credibility will definitely take a hit if he sticks to that term! – Michael Hall May 13 '20 at 23:19
• @MichaelHall I once heard a story of a clever boot involving a request for 100 yards of flight line, an old Seabee storehouse, Marston mats, and a forklift. – chrylis -cautiouslyoptimistic- May 14 '20 at 7:14

The correct term is a Route Segment. CFR 14 part 1 describes a Route Segment as

a portion of a route bounded on each end by a fix or navigation aid (NAVAID).

If the flight is in a straight line from one point to the next, it is said to be "Direct". From a common usage standpoint, DJClayworth is correct in that a "leg" is used to describe a section of a route. However, a leg may contain multiple waypoints or, from a commercial operator's standpoint, an entire flight between airports.

I am unaware of a standard aviation term for the multiple parallel segments, but as the operation in a type of survey, I think Dan F.'s "transect" description is appropriate.

The term "Flight Line" is only used, to my knowledge, to refer to the parking and servicing portion of the airfield apron.

The term "Flying the Line" is often used to describe a pilot or crew which is actively and frequently scheduled to fly the unit's or company's sorties.

Hope this helps. (Current Active Duty USAF pilot flying for 20 years)

Addition - I have worked with units and contractors whose mission was ground mapping and sensing using airborne LIDAR (Light Distance and Ranging). Their sortie profiles were very similar to the one you described. The USDA published guidance for data collection from aerial LIDAR platforms (https://www.fs.fed.us/pnw/pubs/pnw_gtr768.pdf). I have posted their graphic with their names for the various patterns.

• Welcome to Aviation! I've edited your answer a bit to make it more readable and to use quote formatting for the quote. Thank you for serving our country! – FreeMan May 14 '20 at 17:33
• The straight legs of a search grid pattern are not bounded by navaids. Also, you said that the correct term was route segment, then later agreed that transect is appropriate. (I know, i used two similar yet different terms in my answer too!) – Michael Hall May 14 '20 at 18:52
• Thanks for the assist FreeMan. – John Kelley May 14 '20 at 18:52
• Michael Hall - Yes, the original question is a hard one to answer comprehensively. That said, a route segment can be bounded by a fix or NAVAID. A fix can be described by a visual reference point, a NAVAID radial/DME or radial/radial intersection, a standard RNAV (Area Navigation) or DAFIF (Digital Aeronautical Flight Information File) point, or any other reference which can be use to identify a specific location. The straight portions between fixes are route segments, but the overall pattern of parallel segments doesn't have a standard aviation name that I know of. – John Kelley May 14 '20 at 19:09

In the world of idealized navigation, a journey consists of flying a straight line from your departure point to another location, making a turn and flying a straight line to a different point, and so on until you reach the point that is your destination. Reality is a bit more complicated, but it's a useful approximation.

The points are called "waypoints" and the straight lines are called "legs". Although your flight path is a bit different from this, the term "leg" might well apply.

• Leg is not a bad term, but I think it’s more appropriate to a cross country flight like you describe. Just an opinion though... – Michael Hall May 13 '20 at 22:51
• I'd think "LEG" is a good term. It matches up with what each straight segment is called in a Flight Management System. – Ralph J May 14 '20 at 0:32
• At least in airline terminology a ‘leg’ is take-off to next landing, as a ‘flight’ might have intermediate landings. – Jan Hudec May 14 '20 at 6:31
• The term leg matches with general non-aircraft navigation as well. – trognanders May 14 '20 at 15:52

Without delving into too much detail, the most appropriate pilot terms for the straight legs of the search grid you describe would be “track”, or “course”. Both terms are essentially interchangeable, and are often modified to “ground track” and “true/magnetic course” for clarity.

• These describe the direction you are flying, not the act of flying straight for a while. – Jan Hudec May 14 '20 at 5:57
• Yes, you normally have to fly straight for a while to maintain a direction. (With minor adjustments for wind on longer segments) – Michael Hall May 14 '20 at 15:33

From the description of your situation, I would call the entire pattern a "grid sweep" and reffer to each line as a "grid line". Gotta mention I have nothing to do with aviation :)

I have little knowledge of aviation but the idea reminds me of scanlines as they are used in computer graphics as described here: https://en.wikipedia.org/wiki/Scanline_rendering Maybe scanline is a more appropriate term.

• Welcome to Av.SE. Good brainstorming idea! – Ralph J May 14 '20 at 13:34
• Interesting answer. I have little knowledge of computer graphics, so I would probably avoid going on a computer graphics Q&A board and propose using aviation terms. But that’s just me... – Michael Hall May 14 '20 at 15:36