Performance mapping of Cessna 172 SP amphibian float take-off condition on calm water

Purpose This study aims to determine the aerodynamic and hydrodynamic characteristics of the Cessna 172 SP Amphibian float during calm-water takeoff and to identify the angle of attack at which the float begins to generate positive lift. The study addresses the absence of explicit takeoff angle-of-attack guidance in the operating handbook and provides a practical reference for pilot training and water-takeoff procedures at the Indonesian Civil Pilot Academy Banyuwangi. Design/methodology/approach Steady-state two-phase computational fluid dynamics (CFD) simulations were performed using Ansys Fluent 19.1 to evaluate the Cessna 172 SP Amphibian float under calm-water takeoff conditions. The simulations were conducted at a fixed free-stream velocity of 26 m/s for six prescribed angles of attack, a = 0°–5°. The initial float submersion was set to 24 cm to represent a minimum-load takeoff scenario. The analysis focused on aerodynamic drag, hydrodynamic drag, lift coefficient, lift-to-drag ratio, pressure distribution, vorticity and free-surface wave patterns. Findings The results show that hydrodynamic drag dominates the resistance during the investigated takeoff condition. At a = 5°, the lift coefficient becomes positive, while hydrodynamic drag remains approximately 5.7 times greater than aerodynamic drag. This indicates that a = 5° may be used as an initial positive-lift reference for water-release transition under the simulated 24 cm submersion and minimum-load condition. Research limitations/implications This research was performed on a Cessna 172 SP Amphibian Floating Device, primarily during takeoff on calm water. Practical implications This study is based on the conditions of use of the Cessna 172 SP Amphibian Floating Device owned by the Indonesian Civil Pilot Academy in Banyuwangi, but it can be applied elsewhere under similar conditions. Social implications This research is useful as a pilot reference for determining the right angle of attack to exit the water surface. Originality/value The study provides an applied CFD-based assessment of the Cessna 172 SP Amphibian float under calm-water takeoff conditions and offers a condition-specific reference attitude for pilot training. The findings are particularly relevant because the operating handbook does not explicitly specify an ideal float attitude or angle of attack for initiating water release during takeoff.