Taking the CFM56-7B (Boeing 737 NG) as an example. This engine has a single stage HPT and a 4 stage LPT. There is a larger space ahead of the LPT stage 1 vanes, though I'm not sure this is this rather small gap size which attracted your attention. **Overall view of HPT and LPT** Rotors (blades): [![CFM56-7B, turbine rotors and stators][1]][1] <sup>CFM56-7B, turbine rotors and stators</sup> Each rotor is preceded by stator (nozzle). The role of the stator vanes is to convert pressure into velocity and turn the flow more perpendicular to the rotor blades surface (this is opposite to the compressor stages where the vanes are downstream of the blades to convert added velocity into pressure and straighten the flow). **Small gap** Everything is globally continuous, though there is a small gap forward of the LPT stage 1 nozzle which is located in the HPT casing: [![CFM56-7B, small gap before LPT Stage 1 vanes][2]][2] <sup>CFM56-7B, small gap before LPT Stage 1 vanes</sup> This gap makes room for an extended inner platform and outer shroud lip: [![CFM56-7B, HPT shroud and LPT stage 1 nozzle assembly][3]][3] <sup>CFM56-7B, HPT shroud and LPT stage 1 nozzle assembly. Source: CFMI Engine manual</sup> The reason of seeing a (small) gap here could be because the flow is more turbulent behind the HP turbine rotor or for thermal management purpose, giving more room for HPT active clearance control system (the 3rd/rear manifold) and the LPT nozzle cooling ducts, or a mix of both. Just a guess. **Bearings** Regarding the possible problem with a bearing or a bearing support in the way, the bearings are really smaller than the stages: [![CFM56-7B, location of rear bearings][4]][4] <sup>CFM56-7B, location of rear bearings</sup> - The No 4 bearing is within the HP shaft. - The No 5 outer support is within the oil collector shown above, and the bearing itself is within the its support. [1]: https://i.sstatic.net/JQdmz.png [2]: https://i.sstatic.net/8RjFY.png [3]: https://i.sstatic.net/5ezze.png [4]: https://i.sstatic.net/nGFcr.png