The invention is a slot-type accessory mounting 10 and process for quick attach-detach mounting an accessory 4 to an engine gearbox 2. The accessory mounting 10 includes a flange 1 which is provided with a plurality of circumferentially spaced axially protruding studs 7 attached to the gearbox 2 by screws 12. Slotted collar 3 is rotatably secured to accessory 4 by retaining ring 5 which is attached to the accessory 4 by stud nuts 21. The narrow end of slots 6 in collar 3 engage the studs 7 and the entire assembly is held together by nuts 9. Retaining ring 5 is provided with an alignment pin 22 which fits into bore 23 of flange 1 assuring proper alignment of the accessory 4 and gearbox 2. The process of mounting accessory 4 to gearbox 2 is carried out by aligning pin 22 and bore 23, bringing the flange 1 and retaining ring 5 together, passing the nut 9 carrying studs 7 through the larger end of slots 6 in collar 3 rotating collar 3 to secure studs 7 in the narrow end of slots 6, and torquing the nuts 9 to tighten the assembly. The quick detach process is carried out by loosening nuts 9 and rotating collar 3 so that studs 7 and nuts 9 align with the larger end of slots 6 in collar 3 allowing axial movement of accessory 4 of relative to gearbox 2.