A process for estimating the vertical speed of a rotary wing aircraft may include integrating the sum of: a first component corresponding to a vertical acceleration measurement and a second component obtained from the difference between: a first value incorporating a barometric measurement and a second value incorporating a previous estimation of the vertical speed. Each package may comprise articles having absorbent article configurations appropriate for the stage of development of an infant, newborn, or toddler. The plumb rod is slidably received in an adjustable holding member.