The objective of the work presented herein is to study the influence of dynamic ground effect on the longitudinal stability of airplanes during un-power landing by numerical simulation. A method was developed to design a landing control system which considers dynamic ground effect by the inclusion of the h derivatives in the longitudinal equations of motion. A case study was presented to illustrate with an example the influence of dynamic ground effect on the longitudinal stability using the Unmanned Airplane for Ecological Conservation. Open-loop flight simulations were performed considering dynamic ground effect using a program written in FORTRAN language. When the vehicle achieved heights lower than 2.5935 m during the simulations, an unstable response appears. A landing control system was designed using the methodology presented in this paper, and close-loop simulations were completed using a model created in Simulink. The control system drove the airplane to the runway, only when the h derivatives were included in the equations of motion. The unstable response produced by the dynamic ground effect has a strong influence in the flare manoeuvre, and for this reason, in the design of a landing control system, the h derivatives must be included in the longitudinal equations of motion.