Optimization and Simulation Help Designing Safer, Lightweight Aircraft Seating Systems

Altair has been a leader in technology and expertise to develop safer automobiles and reducing potential injury to passengers.  That experience now is helping Altair create safer seating systems for airplanes.  Altair recently presented some of its work for the CompositesWorld Aircraft Interiors Conference in Seattle, an event that is covered in a recent blog entry.

Altair’s optimization technology is being applied to the design of the seat frame.  We all have seen the seat frames that connect the seat to the floor beams.  The seat frame must withstand the static load of the passenger weight but also be able to withstand dynamic loads in case of a hard landing, extreme turbulence or a water landing.  Generally, the seats are required to withstand 14-g and 16-g loads.

Altair continues to develop the technology to use dynamic loads as input to topology optimization in OptiStruct.  This is important in the automotive crash field, and Altair is making tremendous progress here.  As this technology continues to develop, these methods will be available for the design of aircraft seating systems.  The main benefit to the aircraft manufacturers and the airlines is that optimized seat frames will weigh less while meeting the requirements for impact and safety.  Saving even 1 percent of the weight of an individual seat can lead to significant weight savings on the airplane.  Lower weight means the airline can carry more passengers or cargo, fly a longer distance or reduce fuel consumption,  all of which are important for the commercial aviation business.

Optimization process applied to an airplane seat structure (image courtesy of B/E Aerospace)

Topology optimization methods in OptiStruct can be used to design the seat frame for the static load condition.  Designing for the dynamic loads is more difficult, but using the recently developed Equivalent Static Load Method (ESLM), static loads can be estimated from the dynamic loads and these can be used for the topology optimization, which requires static loads as input. Another option is to use an explicit analysis code, such as RADIOSS, and then use the morphing tools available in HyperMesh (HyperMorph) combined with HyperStudy to do size and shape optimization on the structure.  The combination of topology optimization using ESLM in OptiStruct to get the basic shape and then using RADIOSS with HyperMorph and HyperStudy to do the final shape optimization is a good method that has been used successfully many times.

Occupant simulation is another important area for Altair engineers, who have been very active in the development of occupant simulation models and methods for aircraft, using RADIOSS.  Occupant simulation is well developed in the automotive industry and has been instrumental in designing safer vehicles, more robust restraint systems and vehicle interiors that reduce the risk of injury for passengers.  This technology now is being applied to the design of aircraft seating and restraint systems.  The load conditions required for aircraft seating are different from those for automotive seating systems, so adjustments need to be made to the models and methods when applied to airplanes.  Altair is actively working with test labs, research institutes, and the U.S. and European certification agencies in developing these models and modeling methods.

Validation of an aero dummy model (60°pitchNIAR testwith 2 points belt & 14-g acceleration)

One area of active development is with the HUMOS model.  The HUMOS model is designed to accurately model the human anatomy.  With it, the human skeleton, muscular system and vital organs are modeled.  The material properties of all of these systems are the subject of intense research at many facilities in the U.S. and Europe.  This is in contrast to more traditional occupant models that are designed to model the test dummies that are used in physical tests we’ve all seen on TV.  These tests and the corresponding models are good for predicting accelerations and loads on the human body, but the goal of the HUMOS model is accurately to predict potential injury from the impact event.  By accurately modeling the human anatomy, we will be better able to design seating and restraint systems that protect passengers from severe injury.

Human Model for Safety (HUMOS)

The HUMOS model has been developed over the last few years with contributions from many individuals and research labs.  Altair is taking a leadership role in modifying the HUMOS model for use with aircraft-seating load requirements.  Since the impact loads are a different intensity and, more important, a different angle from automotive-seating load conditions, the model is being fine-tuned to predict the loads on the human skeleton and vital organs accurately for aircraft seating requirements.  We are comparing model predictions with available test data and coordinating with the certification agencies to ensure we have robust procedures and defined best practices for occupant simulation for aircraft seating.

Results of HUMOS 2 vs. standard Hybrid II dummy in aero sled tests 

Altair’s significant experience in automotive occupant simulation coupled with our experience in the optimization of aerospace structures puts us in a unique position to make significant contributions in this area.  Although the requirements are different, the underlying technology reflects many similarities between automotive and aerospace.  We hope to continue these efforts and create a safer experience for airline passengers and more assurance that they will not be injured in situations of a hard landing, extreme turbulence or a water landing.

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