...i did not get your point as how will the wheel assembly work as a blocker.
Please read what has been written so far, the landing gear causing the air intake to collapse when retracted is mere speculation on my part.
It is not so much the landing gear assembly itself but the compartment that the landing gear is stowed that protrude into the inlet duct that created a radar impediment, aka 'blocker'.
Radar engineers do not call those impediments 'blockers'. Anything that actually 'block' will reflect back and that is not what we want.
Forget about the jet engine for now, or at least the first compressor stage.
Look at the inlet ducting as a waveguide. All the positive things about waveguides as transmission conduits are negatives when it comes to RCS reduction. The result is the 'S' shape inlet ducting that either partially or completely remove the engine face from frontal view.
With the current 'stealth' fad, we have these types of inlet ducting systems:
1- Conducting where even though the inlet ducting system is materially complex, the surfaces of those materials actually assist the propagation of a radar signal, into and back out, aka 'backscatter', that greatly contribute the frontal RCS figure.
2- Lossy inlet ducting system where radar absorbing materials (RAM) covered the entire inlet ducting, covered the 'bullet' which is the nose of the jet engine itself and covered a set of fixed vanes that are angled
NOT at 90deg from where the incident signal enter the last segment of the conduit prior to engine face. The fixed vanes constitute the last line of radar defense for the engine.
3- Lossy inlet ducting system that incorporate a 'splitter' plate that serves dual purpose: to affect airflow to the first stage compressor and to create an additional radar deflection surface that further reduces the energy level of the incident signal as it bounces through the conduit. Plus RAM coverage per item 2 above.
Multi-spectral air inlet shield and associated inlet structure - US Patent 7159818 Claims
...said splitter is structured to suppress radar signal return or infrared radiation.
The splitter plate must span the inlet duct and its surface must be lossy, or RAM-ed.
Most fighters have inlet ducting type 1. Inlet ducting types 2 and 3 are used when the focus is on RCS reduction, at the expense of other engine/aircraft performance parameters if necessary. Inlet ducting type 3 is the most difficult to design and implemented. If a viewer is able to see a partial engine face, the first compressor stage, then this is about airframe design that made such allowance. At this point, it is up to 'The Man' in charge if it is possible to make the inlet ducting type 2 or 3.
For waveguide properties...The closer the signal's wavelength to the physical dimensions of the conduit, the better the transmission...
Waveguides : TRANSMISSION LINES
Waveguides are metal tubes functioning as conduits for carrying electromagnetic waves. They are practical only for signals of extremely high frequency, where the signal wavelength approaches the cross-sectional dimensions of the waveguide.
For a jet engine inlet ducting system, long wavelengths such as those in the HF/VHF/UHF bands are ideal transmissions when those meters long signals start entering the intakes. Remember...Anything that is good and desirable in a waveguide is a no-no in RCS reduction. We want the inlet ducting to be as bad a waveguide as possible.
Now...That thing called the 'coaxial labyrinth' looks like a creative assembly of splitter plates. If this is true then it is a complex solution to compensate, for lack of a better word, for an 'inferior' inlet ducting design because of an 'inferior' airframe design. I know this is going to raise the hackles of some people here but this is the laws of physics. We do not know its protection level for the engine but we do know that it adds weight and complexity to the engine.
