AASC qualifies and delivers first Trac-A Radome
09/01/2002
AASC completed the qualification static load test on the Trac-A redesigned radome.
AASC completed the qualification static load test on the Trac-A redesigned radome. The ultimate load test involved applying the standard proof load weights and superimposing lead shot bags on the upper shell and pushing up from the rear of the reflector with a pneumatic load cell.
The ultimate static load test purpose was to demonstrate the rotodome can withstand the critical symmetrical flight condition C 2 without evidence of yielding and failure.
The loading condition simulated the critical symmetrical flight condition C 2 with 46,738 lbs of vertical shear and 4,648,260 inch-lb moment.
The loading condition was applied to two orientations of the rotodome: aft section and transverse beam. AASC measured surface deflections to ± 0.01 inch tolerance at 14 locations across rotodome surface.
For this test, the basic approach was to utilize the existing proof test loading mechanism (designed in the early 1960's) with additional lead shot weights and a hydraulic force to obtain a loading equal to 115 percent of the ultimate C 2 flight loads. The additional loads were distributed onto the three separate surface areas.
Briefly, the proof test loads can be described as a series of massive metal blocks that apply a distributed load onto the upper and lower surfaces of the outboard leading edge of the dome. The upper surface weights rest against the dome and apply an average downward pressure of 2.5 psi. The lower surface weights are held in place with a vacuum system that applies a 1.25 psi. downward pressure. The additional downward loads required for this test plan are obtained by stacking 25 lb. lead shot bags onto the proof load metal blocks over the upper leading edge area and also additional lateral upper surfaces. The upward thrust load on the rear of the dome was accomplished by a hydraulic pressure against the lower surface, using a hydraulic pressure bag capable of sustaining an maximum internal pressure of about 3 psi. with an appropriate design safety factor.
Approximately 200 strain gauges were applied and documented during the test. AASC utilized their new static load test data acquisition system to track and record the strain gauge measurements. Correlation between Northrop Grumman's test predictions and the test was extraordinarily precise, within 10% on all critical gauges.