F404 and F414 are the epitome of how military turbine engines can be made to be reliable.
The F404 has a version called F412 with a very large inlet fan. This is a non afterburning engine specifically made for A-12 Avenger 2 plane. This engine developed very high thrust due to the large fan it utilised. In F414, they used a similar but comparatively smaller fan than the one used in F412 but larger than the one in F404. This fan provided a lot of air to flow through the compression and combustion section. To accommodate this extra air flow and sustain efficient burn, accordingly, they had to enlarge the diameter of the f412’s and F414’s combustion chambers. This way they were able to achieve 13000lbf dry thrust from the f414 which had essentially the same dimensions as f404, apart from the larger fan and bigger combustor. This was called a “trapped vortex combustor”.
A-12 Avenger 2
View attachment 69491
Whence the A-12 project was cancelled so was F412 engine. But it paved the way for f414.
With the EDE (Enhanced DurabilityEngine) version, F414 has gone through an upgrade of materials and aerodynamic design in it’s HP Turbine stage, allowing it to go hotter without problems and by reducing HP compressor stage by one from 7 to 6 it was made possible to lower SFC and improve durability by 3 times.
The EPE (Enhanced Performance Engine) version of F414 has been furnished with a totally new Fan, Core and Turbine section that gave a 20% increase to thrust level, achieving 26400lbf with AB.
GE has also been conducting experiments on F414, successfully, by replacing LP turbines with CMC materials.
I only hope that at TEI, our engineers, being part of GE family, are making note of these innovations and will in time, apply them to our own engines too.