B-1, B-2 and KC-135 flight line maintenance time reduction via the development of Enduralock fasteners, self-aligning nut plates, and locking V-Band clamps as substitute components

Enduralock’s proposal is to improve flight line maintenance times on the B-1, B-2, and KC-135 aircraft by developing its mechanically locking, high vibration resistant fasteners, self-aligning nut plates, and locking V-Band clamps as component substitutions. In vibration testing, Enduralock fasteners survived 10x the aerospace requirement. They remain locked even with loss of preload (clamping force). Fasteners used in critical aerospace applications are often safety-wired together to reduce the chance of loosening with vibration, which is very labor-intensive and therefore costly. Alternatively, castle nuts with cotter pins are utilized to secure fasteners in critical applications, but this can also be very labor intensive. A mechanic can typically safety-wire 10 fasteners per hour at an hourly labor rate of $150. In that same period of time, over 300 of Enduralock’s Silver Lock fasteners could be installed. Castle nuts and cotter pins are frequently used in the landing gear assembly of aircraft. Being a critical application, a narrow range of torque is typically specified by the engineers. A castle nut only has 6 gradations of torque per revolution. If the mechanic attempts to apply the nut with the prescribed torque, and the slots of the nut do not line up with the pre-drilled hole in the bolt to place the pin, he removes the nut and tries another. He will continue this process occasionally for up to one hour for one bolt. Enduralock’s fasteners have 36 gradations of torque per revolution.  It is, therefore, likely that the mechanic will achieve the prescribed torque on the first attempt resulting in a significant reduction of maintenance time. V-Band clamps employ safety wire to lock them, but this is labor-intensive and costly. Enduralock will apply its fastener locking mechanism in the development of a V-Band clamp that mechanically locks and is high vibration resistant, which will reduce maintenance time and cost. Nut plates are used as the female receptacle for bolts attaching aircraft access panels. With current nut plates, there is radial flotation of the nut element, but the nut element will not “tip” to engage an off-axis bolt. This results in a significant amount of maintenance time for panels such as the fuselage fairing and leading and trailing wing edge panels, as mechanics need to line up all bolts in axis with their nut plates, before tightening the first. Bolts are captured to the panel with retaining rings that slide longitudinally on the bolt, but these can bind and break leading to foreign object debris (FOD). The nut element of Enduralock’s nut plate will “tip” to engage an off-axis bolt and then self-align, and it allows for a fixed position bolt retaining ring reducing FOD. It results in a significant reduction of maintenance time. In summary, by developing and testing Enduralock’s fasteners, nut plates, and V-Band clamps as substitution components, flight line maintenance times will improve for the B-1, B-2, and KC-135.