Bird Bellows designs and manufactures metallic bellows and bellows flexible seal assemblies for a range of applications in aircraft propulsion systems which include engine sensor shielding, where metallic bellows seal assemblies provide long life flexible protection to mechanical sensor systems, and engine zone penetration seals that offer flexible pressure sealing where it is necessary for cabling or other components to pass through a pressure bulkhead. Bellows and bellows assemblies are also supplied for use in engine build-up duct sub-assemblies and APU air intake and exhaust systems which can experience a high degree of relative movement between the airframe and the turbine assembly.