Browse Topic: Inspections
As part of a larger project aimed at gaining a better understanding of factors that affect the quality of test results using anthropomorphic test devices (ATDs), the FAA tested the effects of dynamic loading of an ATD pelvis. The ATDs required in the aviation regulations were initially developed for the automotive crash environment, which does not include a vertical testing component. One of the two dynamic tests is a vertical impact, with the principal measurement being the compressive load in the lumbar spinal column, with a regulatory limit of 1500 lb. The lumbar load cell is mounted to the pelvis, and data collected could be affected by the performance of the ATD pelvis. The ability to define a vertical calibration test could be used to determine if the pelvis is acceptable for initial use or to monitor in-service degradation. Three ATD pelvises were compressed in a high-rate load frame. The peak load and loading rate of the pelvis compression were selected to simulate conditions achieved in transport category aircraft vertical seat testing. The primary test objective was to measure changes to the rubber and foam cover of the metallic pelvis during high cyclic loading. Each pelvis was subjected to over 100 cycles. Static dimensional measurements, based on a manufacturing tolerance evaluation, were collected during testing. The high-cycle testing did not deform the foam and rubber covers enough to exceed the total dimensional tolerance of the pelvises (± 0.120 in.). The appearance of visual damage was closely monitored throughout the testing. Similar visual damage was seen for each pelvis and occurred at low cycles — 15 to 30. Results suggest the appearance of damage minimally changed the dynamic response of the pelvis. Force-deflection data were also collected from each test series. These data showed minimal change during testing, with the deflection at 2000 lb. changing approximately 0.100 in. across the 105 cycles. This value is similar to the manufacturer’s tolerance for the height of the pelvis. Based on this, the number of vertical sled tests that would precipitate replacement may be over 100 cycles. Due to the harsh environment of dynamic sled testing, other factors, such as cuts in the foam and rubber due to belt loading, may trigger the removal of an ATD pelvis from service prior to the pelvis reaching a defined number of cycles. Future FAA research will evaluate how this change in pelvis force-deflection affects lumbar load.
Inspecting the interiors of tanks and ships for defects involves accessing confined and elevated spaces. This can be difficult and hazardous for a person. Ducted aerial vehicles that can hover close to the object of interest can achieve this in a safer and more efficient manner. Such a vehicle is desired to be compact, to have a high hover endurance and to be protected from impact. This paper describes a design concept comprising ducted coaxial counter-rotating rotors with a compact swashplate mechanism for cyclic pitch input to the lower rotor. An experimental setup was used to investigate the effect of the duct. A numerical Blade Element Momentum Theory model was developed and validated to inform rotor selection. A prototype was designed and built with a hover thrust of 9.17 N, outer diameter of 350 mm, and height 173 mm. The duct provided a thrust benefit of 32% for this configuration for a given power. The prototype achieved stable controlled flight in hover and in passing near walls and surrounding obstacles. Some oscillations in attitude were seen in flight. Future work includes improving the control algorithm of the vehicle.
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