Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Phillips Head Screws John Henry Phillips, of Mass. patented his double slotted screw in 1932. The very similar Reed-Prince screw is not approved for aircraft, whereas the Phillips is. The Reed-Prince head is an imitation Phillips that is designed to eject the screwdriver when pressure is sufficient to break the head of the screw. Inside the slots of the Phillips are some multiple ramp angles that will cause the screw driver to lift out before you can break off the screw head. The Phillips greatly increased production because the screw could be balanced on the screw driver prior to insertion. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM