AN INVESTIGATION OF TROOP SEAT TESTING METHODOLOGY USING MADYMO MODELS

摘要

Energy-absorbing troop seats can save lives and mitigate injury in many military aircraft mishaps. Several designs are currently in the field and research continues to provide additional improvements. When it comes to evaluating performance, however, troop seats raise some issues that normally do not occur for pilot seats. Pilots have hand and foot controls that dictate the logical position for manikins in laboratory tests. The same cannot be said for troop seats, but positional variations can have significant effects on some test results. The first part of this study uses computer modeling with the Mathematical Dynamic Model (MADYMO) simulation program to examine the sensitivity of test outcome to troop seat occupant position. The vertical component of the lumbar load, a key performance parameter for troop seats, serves as the principal variable in case comparisons. For some types of seat energy absorbers (Eas), it is shown that changes in arm and leg position can produce lumbar load differences which exceed those that might be expected from normal test-to-test variability. These results point to a need for standardization so that tests of a given seat design, as well as tests of differing designs, can be compared directly. The second part of this paper considers an issue that arises in the testing of both troop and pilot seats: the method chosen to deliver the crash impulse. The two most common methods are a drop tower (DT) test and a horizontal accelerator (HA) test. In the latter, the seat is rotated 90o to vertical so that the seat's Z-axis is aligned with the laboratory X-axis. This leads to questions about the influence of gravity on the test results. Once again, MADYMO simulations are employed to study test result sensitivity, and to determine whether gravity compensation is called for in the form of an HA pulse adjustment or a small forward pitch of the HA seat. The results indicate that the compensation required depends on the test configuration and the relative importance of the measurements taken.