How does a Cessna 172 at flight speed of 161 mph adjust for earth’s rotation speed of 1040 mph on at the equator?

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In Dallas, Texas latitude 32.7767° the speed of earth’s rotation is 863.8 mph compared to 537.4 mph at Olympia, Washington latitude 47.0379° N.  These different earth rotation speeds are determined from the fact that earth rotates 360° in a 24 hour time frame corresponding to the diameter of the earth at these respective latitudes.  In fact, there are 180° of latitudes resulting in earth’s multiple surface speeds ranging from 1040 mph at the equator to zero at the poles.

These multiple speeds are mathematically described as the Coriolis effect (Rotating Earth) for an object that becomes disconnected from earth. Described in “Long Range Shooting Handbook” by Ryan M Cleckner., military snipers have to adjust their sight targeting based on their latitude location as well as the angle of the sniper’s shot relative to his latitude location.

It gets complicated.  Degrees of latitude are parallel so the distance between each degree remains almost constant. Each degree of latitude is approximately 69 miles (111 kilometers) apart. Coriolis effect takes into account 180° of latitudes then each half mile, each quarter mile and so on with 360° of angles off each latitude.  Does a sniper’s rifle that requires precision targeting have precision GPS?  A .30-06 hunting rifle fired due north at the equator has to adjust for earth spin at 1,525 ft. per second. Usually these type rifles are used for taking 350 to 500 yard shots.

The Coriolis effect requires that airline pilots must adjust flight path to reach their target destination. The instrumentation used by airlines is Honeywell: Air Data Inertial Reference System (ADIRS) which includes an Alignment Calibration Module (ACM) for the Coriolis effect (e.g. multiple rotation speeds).

The Coriolis effect is further described and illustrated as an animation on Exploring Earth stating that pilots take the Coriolis effect into account so they do not miss their targets.  Exploring Earth states that the analysis is a collaboration with NASA/Goddard Space Flight Center and others (identified at the bottom of the animation web site).  View the animation and pay attention, it is misleading.  For the animation of south to north – Tierra del Fuego, Argentina directly toward Rio de Janeiro, Brazil – a flight taking an estimated time of five hours, the target destination would move 4,743 miles.  The Earths diameter is 7,918 miles.

Neil deGrasse Tyson has even commented that the spinning earth affects football games; that the Coriolis effect does have to be considered regarding the flight of the football on a field goal attempt.

Regarding these supposedly known facts, then for the objects that are disconnected from earth, the following must be true:

In Dallas Texas, latitude 32.78° N, rotation speed is 863.8 mph:

  1. Hover in a helicopter and you will arrive at your (same latitude as Dallas, Texas) Artesia, NM destination in 31 minutes or your San Diego California destination in one hour and 22 minutes.
  2. A parachute drop of 5,280 ft. (1 mile) descending at an average of 20 mph requires elapsed time of: 29.33 seconds. The target football stadium moves 7.04 miles.
  3. A field goal kicked from east to west that has a 2 second flight time has an increased distance of 15.01 yards.

In a Cessna 172 at 161 mph for a 300 mile flight for the same longitude of 102.07° W:

  1. Earth’s rotation speed at Stratford, Texas is 835.4 mph
  • Flying South to North, from Midland Texas to Stratford, TX; the target destination has moved 1,557 Miles.
  1. Earth’s rotation speed at Midland, Texas is 884.2 mph
  • Flying North to South, from Stratford, TX to Midland, TX; the target destination has moved 1,647 Miles.

In reality we know that light aircraft, such as a Cessna 172 that has air speed of 161 mph does not have to adjust its flight path to be on target to its destination, a helicopter cannot hover and reach its distant destination and a parachutist does not have to hit a moving target.  So, do these examples represent the utilization of Einstein’s Theory of Relativity to maintain a fixed relationship to the rotation of earth?

Science cannot be wrong, there surely must be an equation that reconciles between certain disconnected objects that are – or are not – subject to the Coriolis effect.  If you decide to search for the formula or create the formula, remember:

the earth’s multiple rotation speeds range from 1040 mph at the equator to zero mph at the poles and there are innumerable angles off each of the innumerable latitudes.

For this exercise, do not include the curvature of earth.  That can be worked on at a later time.


Honeywell: Air Data Inertial Reference System (ADIRS)

Determine point to point time and distance

Article by Kert Moore

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