So in my little E project I have found several photos of the intakes on a downward angle. It looks like this is true to some extent on all F-15’s. Is it more so on the E’s. it looks like they must move up and down for some reason depending on the need. The intakes on my model are up fully so not sure if they need to be sloped down a little to be “correct”
I’m no Eagle expert, but I do believe that the intakes on the F-15s are designed to move during takeoff and landings in conjunction with the AoA (Angle of Attack) and to keep them relatively parallel to the ground as the F-15 has such a large wing surface area.
At least I think I remember reading about that somewhere back in the mid-80s when I was building them.
You are correct. The intake openings of the F-15 engines are movable and allow control of air entering the engine. The intakes can actually take in more air than the engines need and stall the engines. Someone more knowledgeable will have to chime in to confirm but I believe the intakes are computer controlled and based on engine needs and altitude. I also believe that all F-15s have the feature.
That would make sense to me. i just wanted to confirm it is the same among all F-15 variants.
On the ground with the engines not running the ramps will be full up. After engine start the ramps will drop restrictinjg air flow. At higher speeds the ramp will close and bleed air doors will open inside the intake venting air overboard to prevent compressor stall. The ramps are controled by the CADC (Central Air Data Computer) which uses TAS, IAS, temp, and pressure to controle the ramps in flight.
There are actually two separate “stages”.
The outer intakes move up and down according to airspeed/AOA. If I recall correctly, there are three positions - Up/down/Intermediate. These variable-angle intakes are present on every F-15 variant.
Secondly, air entering the compressor must be below a certain speed (subsonic?) regardless of the aircraft’s actual airspeed. To achieve this, there are a number of movable ramps inside the intake throat to adjust the airflow and/or redirect excess air out through vents in the top of the intake.