Design and experimental verification of the USB flap panel structurefor NAL-STOL research aircraft

S the USB flap of the NAL STOL research aircraft is one of the primary design modifications of the original C 1 transport aircraft an acoustic fatigue test of substructural models at an elevated temperature was conducted to verify the safety of the flap structure during the planned flight evaluation program Five structural models were provided and the following test items were carried out: 1) detection of the thermal buckling temperature 2) vibration tests and 3) acoustic fatigue tests at elevated and room temperatures The conclusions reached in the experiments are summarized as follows: 1) thermal buckling occurred on test panels 2) resonant frequencies of the flap test panels fall in the range between those of clamped and simply supported plates and 3) throughout the prescribed fatigue test period all structural models have proven to be strong enough to resist both acoustic and thermal loading In addition to the laboratory verification analytical determination of response has been obtained and the fatigue life has been estimated based on the assumption that the flat test panels were uniformly loaded by heat and noise