This Incredible Video Shows How F-15’s Variable-Geometry Air Intakes Work

Here’s a rare look at “magic” of the F-15 Eagle’s moving air intakes.

The video in this post is quite remarkable: shot during a recent rehearsals of the Gifu Air Base Air Festival (that will take place next weekend), it shows an F-15J of Flight Development and Experiment Wing of the JASDF (Japan Air Self-Defense Force), based at Gifu, during a series of pitch-up/pitch-down maneuvers whose purpose is to show the effect of the elevators.

The F-15’s air intakes are engineered in such a way the ramps can move up and down, so as to change their angle during flight and give the optimal air flow for the engines under the current combination of airspeed, altitude, and throttle setting. The air intakes also include a diffuser ramp and a bypass door that move not only to feed the compressor with the right amount of air, but also to slow down the airflow and make it subsonic before it reaches the engine, thus preventing shock/pressure waves on the compressor and avoid stalls.

Variable geometry air intake of F-15 pic.twitter.com/KvQBwmrAYh

— Harvey Blanquisco (@ChonkyBoi562) November 5, 2023

While you can find other videos of the air intake ramp pivoting up and down, you rarely get a chance to clearly watch it moving so fast.

By the way, you can watch one of the F-15J’s practice displays here.

About David Cenciotti

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David Cenciotti is a journalist based in Rome, Italy. He is the Founder and Editor of “The Aviationist”, one of the world’s most famous and read military aviation blogs. Since 1996, he has written for major worldwide magazines, including Air Forces Monthly, Combat Aircraft, and many others, covering aviation, defense, war, industry, intelligence, crime and cyberwar. He has reported from the U.S., Europe, Australia and Syria, and flown several combat planes with different air forces. He is a former 2nd Lt. of the Italian Air Force, a private pilot and a graduate in Computer Engineering. He has written five books and contributed to many more ones.