Mastering Cruise Descents

Lets fire up the Wayback machine and set it for high school physics class. As an aircraft climbs, it burns fuel (and by extension, money) to provide kinetic energy. That energy is used for climb performance and airspeed (countering that demon drag in the process). Once the aircraft is tucked away at a cruise altitude, some of that formerly-kinetic energy is available as potential energy due to the force of gravity acting on the aircraft. Potential energy can be converted back into kinetic energy by initiating a descent, which you can observe as increasing airspeed (all else remaining equal).

Editorial Staff

Wednesday, December 03, 2014 at 12:00 AM ET

Verified

Key Takeaways:

Optimizing aircraft descents by leveraging stored potential energy at altitude, rather than immediately reducing power, significantly improves efficiency in higher-performance aircraft.
Effective descent management involves planning for cruise power descents or gradual power reductions, using simple mental math to determine the descent start point and maintaining a consistent rate (e.g., 500 FPM).
Properly executed descents save time, reduce fuel consumption, lower operational costs, and can contribute to better engine health by avoiding shock cooling.

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Let’s fire up the Wayback machine and set it for high school physics class. As an aircraft climbs, it burns fuel (and by extension, money) to provide kinetic energy. That energy is used for climb performance and airspeed (countering that demon drag in the process). Once the aircraft is tucked away at a cruise altitude, some of that formerly-kinetic energy is available as potential energy due to the force of gravity acting on the aircraft. Potential energy can be converted back into kinetic energy by initiating a descent, which you can observe as increasing airspeed (all else remaining equal).