48 research outputs found

    Tests of a Gust-alleviating Flap in the Gust Tunnel

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    Tests were made to determine the effectiveness of a long-period dynamically overbalanced flap in reducing airplane accelerations due to atmospheric gusts. For two gust shapes, one gust velocity, one forward velocity, and one wing loading, a series of flights was made with the flap locked and was then repeated with the flap free to operate. The records were evaluated by routine methods. The results indicate that the flap reduced the maximum acceleration increment 39 percent for a severe gust but with a representative gust shape (a sharp-edge gust), the reduction was only 3 percent. The results also indicate that the flap tended to reduce the longitudinal stability of the airplane. Computations made of the effectiveness and the action of the flap were in good agreement with the experimental results

    Effects of airplane flexibility on wing bending strains in rough air

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    Some results on the effects of wing flexibility on wing bending strains as determined from flight tests of a Boeing B-29 and a Boeing B-47A airplane in rough air are presented. Results from an analytical study of the flexibility effects on the B-29 wing strains are compared with the experimental results. Both the experimental and calculated results are presented as frequency-response functions of the bending strains at various spanwise wing stations to gust disturbances. In addition, some indirect evidence of the effect of spanwise variations in turbulence on the response of the B-47A airplane is presented

    A correlation of results of flight investigation with results of an analytical study of effects of wing flexibility on wing strains due to gusts

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    An analytical study of the effects of wing flexibility on wing strains due to gusts has been made for four spanwise stations of a four-engine bomber airplane, and the results have been correlated with results of a previous flight investigation

    Sacral dome resection and single-stage posterior reduction in the treatment of high-grade high dysplastic spondylolisthesis in adolescents and young adults

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    OBJECTIVE: The description of the operation technique and retrospective review of 15 consecutive patients who were treated by posterior sacral dome resection and single-stage reduction with pedicle screw fixation for high-grade, high-dysplastic spondylolisthesis. MATERIALS AND METHODS: All the patients had high-grade, high-dysplastic spondylolisthesis L5 and were treated by posterior sacral dome resection and posterior single-stage reduction from L4-S1. The average age at the time of surgery was 17.3 (11-28) years. The average follow-up time is 5.5 (2-11.6) years. Clinical and radiological data were retrospectively reviewed. RESULTS: Spondylolisthesis was reduced from average 99% preoperative to 29% at the last follow-up. L5 incidence improved from 74° to 56°, the lumbosacral angle improved from 15° kyphosis to 6° lordosis, lumbar lordosis decreased from 69° to 53° from preoperative to the last follow-up. While pelvic incidence of 77° remained unchanged, sacral slope decreased from 51° to 46° and pelvic tilt increased from 25° to 30°. Clinical outcome was subjectively rated to be much better than before surgery by 14 out of 15 patients. Four out of 15 patients had temporary sensory impairment of the L5 nerve root which resolved completely within 12 weeks. There were no permanent neurological complications or no pseudarthrosis. CONCLUSION: The sacral dome resection is a shortening osteotomy of the lumbosacral spine which allows a single-stage reduction of L5 without lengthening of lumbosacral region in high-grade spondylolisthesis, which helps to avoid neurological complications. This is a safe surgical technique resulting in a good multidimensional deformity correction and restoration of spino-pelvic alignment towards normal values with a satisfactory clinical outcome
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