Home > Technology > > Engines > Air Inlets
Air Inlets Print E-mail
(18 votes, average 4.00 out of 5)
Written by Sabc   
Article Index
Forum Discussion
Related Articles

inlet_imageSince the F-15E being a twin engine fighter, each of the engines have its own air induction system. These systems work independently of each other. Each of these systems consist of three variable ramps, a variable diffuser ramp and a variable bypass door to control airflow from the point of entering into the inlet duct to the point of entering the engines. See the following figure.



- First Ramp
- Second Ramp
- Third Ramp
- Diffuser Ramp
- Bypass Door
- Engine

The goal is to provide the engines an airflow as smooth and optimal as it can be. The variable ramps provide air at optimum subsonic flow to the face of the engine fan inlet within a wide range of aircraft speeds. The bypass door is used to relieve excess pressure in the inlet duct by driving excess air to the airflow otside of the aircraft if necessary.

The position of the ramps and the bypass door are controlled by the air inlet controller ( AIC). The AIC uses inputs as angle of attack ( AoA), aircraft speed and other outputs from air data systems and moves the ramps and the bypass automatically to their momentary optimal positions. As a simple rule of thumb is that the first ramp (as the only ramp that is visible from the outside) always should be parallel to the airflow (this means the ramp is in its up position at high speeds and the ramp is in its down position at low speeds, thus high angles of attack). Ramps movement is done by using hydraulic pressure provided by the F-15E's hydraulic power system.

If the engine is not running, the first ramp is locked in its full up position. During engine start once the engine becomes online, the ramp intensively slams to its full down position.

The AIC system can be turned off in case of emergency. This is done by the inlet ramp switch (one switch for each inlet ramps). These are lever locked switches, located on one of the foremost panels on the pilot left hand console (see figure below).


1 - Left Inlet Ramp Switch 2 - Right Inlet Ramp Switch

The switch has two positions, AUTO and EMERG. In the AUTO position the AIC system is turned on. In the EMERG porisiton the AIC system if turned off and ramps and bypass doors move to their emergency positions: that is ramps ar full up and door is closed. In case of a hydraulic power loss, the airloads force the ramps and bypass door to their emergency positions.


  • F-15E Flight Manual TO 1F-15E-1 (courtesy of
  • The F-15E Strike Eagle Forum (SEF)

Forum Discussion

You can discuss this article in the Strike Eagle Forum with the latest posts appearing here below as well. Clicking on the 'Discuss' button takes you to the SEF, while clicking on the 'Quick Post' text enables you to make a post here right away.

Article discussions are available for registered users only!

Last Updated on Wednesday, 06 October 2010

You need to login or register to post comments.