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Q:

I assume that a jet engine reaches maximum thrust at take-off and lift to cruising elevation and reduced thrust while landing. At what percent of maximum thrust at ideal flight conditions does the engine deliver?

A:

The maximum cruise thrust as a percentage of maximum takeoff thrust varies depending on the engine. In actual practice, the cruise thrust will vary depending on the plane and atmospheric conditions.

 

On the CFM56-7B engine, used on Boeing 737 Next Gen airplanes,  the maximum cruise thrust ranges from 20%-30% of the maximum takeoff thrust. Cruise thrust doesn't vary much from model to model since thrust only needs to equal drag. The takeoff thrust does vary as that needs to be bigger to get more massive airplanes off the runway in time.

 

Interestingly enough, the maximum climb thrust is only slightly higher than the maximum cruise thrust ranging from 21%-32% of the maximum takeoff thrust.

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