Sapper number 24 was the last Aveling and Porter engine to be called a steam sapper. It was used by the newly formed Balloon Corps in 1885. The locomotive and another one ordered shortly afterwards were used to haul "balloon trains". Each train consisted of five wagons carrying gas cylinders, a water cart, and a wagon for the balloon, basket and winch. Balloons were normally employed as elevated observation platforms and as such were tethered though observers were trained in how to handle free flight in case the balloon broke away.