The project was initiated to explore the development of a custom modular test rig to facilitate the safety, strength, and performance testing of aeroplane components to conform to industry-wide regulatory standards. The test rig concept was required to be flexibly configurable to enable the testing of multiple component parts (46 in total) upon a single rig structure within a small test area of 12m2. Prior to project outset across the aerospace industry, individual test rigs were developed for each part (e.g. wing, suspension) which necessitated considerable material utilisation and large testing areas. The development of a modular, universal test rig with the capacity to accommodate a myriad of component test sequences was seemingly unprecedented. The test rig was seen as an essential step towards gaining regulatory approval for the first electric-powered commercial business aircraft capable of reliably transporting business class clients between different business hubs in Europe, which was subject to significant clamour within the air travel industry to be the first to achieve it. The overall plane technology would be geared towards a significant innovation as it would facilitate vertical take-off and landing (the ability to hover on the spot, take off and land vertically without relying on a runway).
The Company faced multiple technical limitations in pursuit of the complex objective. For instance, information relating to part specifications was severely limited due to the aircraft being in development and its components therefore being subject to change. However, MedTec was informed of test criteria the rig must deliver, such as wing force loadings and oscillation (replicating in-flight air pressure conditions) and suspension safety procedures and metrics. The test rig therefore must be designed to simulate a range of forces and support rigorous and accurate testing processes across a range of modular configurations to enable engineers to obtain quantitative test data on which to evaluate part condition, stress limits and safety.
MedTec sought a rig design whose geometries, construction and modular features could be flexibly augmented to account for new plane parts. This would represent a novel concept as conventional test rig solutions were previously only designed to trial single parts, whereas the proposed solution would hopefully provide the means to test multiple part configurations and arrangements on a single piece of equipment.
An extensive period of iterative digital design was launched that was aided by specialist CAD software and multiple repetitive design sequences. In addition to a hydraulics system and other elements of the rig infrastructure, MedTec sought to develop an interfacing plates system incorporating tie beams, angle bracketry, and hole patterns etc. The Company hypothesised that the interfacing plates would enable the jig’s constituent parts to be consolidated and facilitate reconfiguration in-between component test phases. During the design workstream, several novel approaches and concepts were experimented with. For instance, plate infrastructure prototypes were designed to determine whether two frames could be bolted together and tested up to 100 kilonewtons across multiple axis, thereby negating the existing requirement for standalone test equipment.
In addition to stress test simulations, Finite Element Analysis (FEA) was undertaken to break down the jig into thousands of finite elements – such as little cubes – and mathematical equations were applied to predict the behaviour of each element against pre-determined criteria. The individual behaviours were subsequently aggregated to predict the behaviour of the holistic rig solution. MedTec determined that manufacturing rig sections from standard structural steel would produce major weaknesses that would not withstand test loadings. In response, the Company experimented by incrementally increasing material thicknesses and integrating strengthening plates to areas of vulnerability, as well as modifying bolted and welded gusset designs. Simulatory testing and design modification work was conducted iteratively which enabled MedTec to obtain the quantitative insights needed to gradually enhance rig robustness, modularity, and configurability.
MedTec undertook manufacturing trials alongside a fabricator with a view to determining whether the design drawings could be effectively manufactured. Design reviews were launched to resolve several fitment and alignment challenges and alternative materials were trialled to improve the robustness/strength of the rig and plate system. The process was aided by repetitive loading tests. After selecting EN24T hardened steel, manufacturing trials were conducted to evaluate whether machining tolerances (accuracy) could be satisfied while maintaining component strength attributes. A novel resolution was derived whereby the integration of adjustment bolts and grub screws enabled realignment prior to test sequences, thereby lowering the tolerances to a level that lessened the machining challenges faced.
MedTec installed and rigorously tested the prototype rig with view to evaluating performance against a myriad of criteria, including proof loading, alignment, configurability, strength, and testing efficacy. During the extensive period of analysis and redesign, the Company also rigorously tested the strength and condition of the welds to ascertain whether the structure could withstand stress loadings.
MedTec has developed a technologically advanced jig solution that has the capacity to test a wide variety of plane components within a confined space, without the requirement for dedicated individual testing apparatus. The Company has proven, by way of considerable trial-and- error experimentation, that developing configurable, modular testing rigs for next generation commuter jets is technologically feasible despite being complex to achieve and not readily deducible within the field of engineering design. This technological advance in aerospace engineering has the potential to advance the development, introduction, and critical maintenance of innovative plane technologies in the future, such as electric and vertical take-off planes.
