How Aircraft Engine Cowlings are Maintained?
The cowling of an aircraft engine is the structure’s removable covering, primarily used for drag reduction and increased cooling. During a standard flight, only around 15-30% of total ram airflow colliding with the engine nacelle will actually enter the structure for cooling. As such, the rest of the ram airflow remains outside of the cowling and cannot be optimally used. To improve upon this, the engine cowl will need to be faired in such a way that air may flow across the cowl with low energy loss.
For the manufacturing of the engine cowl, such structures are produced with removable sections. Generally, sheet aluminum or composite materials are primarily used for the panels, ensuring that the external surface of the assembly is smooth enough to promise airflow. The internal assembly, meanwhile, is designed in such a way that enhances the strength of the panel while also providing receptacles to benefit the toggle latches, engine air seal, and cowl support.
For the air seal of the cowling, such components take advantage of rubber materials, and bolts allow for it to be fastened to a metal rib that is then riveted to the cowl panel. With the implementation of the air seal, air can be kept within the engine so that it cannot escape the inner surface before flowing around each cylinder. It is important that engine air seals are present on aircraft that utilize engines with complete cylinder baffling systems that cover cylinder heads. In such instances, the air seal will ensure that ram air flows through the baffle system for proper circulation and cooling. To ensure that all structures are properly functioning with integrity, the cowl panels should be inspected during all regular inspection intervals, and the cowling should be removed for more thorough maintenance procedures.
During the cowl inspection process, there are a few things to always remember or carry out. First, the cowling panels should be thoroughly looked over, ensuring that all scratches, tears, dents, and other damages are found if present. Generally, such damage can weaken the overall panel structure, possibly resulting in increased drag as airflow is disrupted. Additionally, damaged panels can also increase the rate at which corrosion occurs.
When checking the cowling panel toggle latches, one should keep an eye out for any rivet fasteners that have been pulled or any handles that have become loosened or damaged. The internal side of the panel also warrants inspection, ensuring that there are no cracks present on the reinforcing ribs of the assembly. Additionally, it is crucial that the air seal is also checked for damage. If the cowling assembly features flap hinges and cowl flap hinge bondings, such components should be looked over to see if there are issues in terms of mounting or damage in the form of breaks and cracks. Such inspections can be carried out visually, and they are important to conduct on regular intervals to best guarantee that the cowling always remains serviceable and fit for optimal engine cooling.
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