A jet, cruising at 26,400 feet, begins its descent into JFK Airport, when it is 96 miles away. Another jet, cruising at 31,680 feet, is 120 miles from JFK when it begins its descent. Which of these two paths of descent is steeper? Is a linear model reasonable to use in this situation? Explain.

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  first jet is steeper; not unreasonable

Step-by-step explanation:

The slopes in feet per mile for the two jets are ...

  (26,400 ft)/(96 mi) = 275 ft/mi

  (31,680 ft)/(120 mi) = 264 ft/mi

The descent of the first jet is steeper.

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The path a jet will follow depends on a number of factors, including weather and other air traffic. It is not unreasonable for a jet to follow a linear glide path to an airport from these altitudes and distances. JFK is sufficiently busy that air traffic control may dictate other-than-linear descent paths.

Final approach is typically done on a 3° glide slope, about 277 ft descent per mile.

Additional comment

Studies have been done to test the feasibility of linear descent paths into some of the busiest airports in the world. The conclusion is that fuel burn could be improved and air traffic management made simpler by such flight paths. However, current jet autopilots are not equipped for direct input of such flight routes. Pilot workload would be slightly increased until software could be updated. There appears to be no current plan to change the way terminal area control is done.

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