The 1 kg falcon can slow down in a dive by increasing its parasite drag and the angle of attack of its wings. The falcon loses 60 m of altitude while pulling out of the dive, and lift and loss of altitude both decrease as the angle of the dive decreases. During pull out at top speed from a vertical dive, the 1 kg ideal falcon can generate a lift force 18 times its own weight by reducing its wing span, compared with a lift force of 1.7 times its weight at full wing span. The time and altitude loss to reach 95 % of top speed range from 38 s and 322 m at 15 degrees to 16 s and 1140 m at 90 degrees, respectively. An ideal falcon diving at angles between 15 and 90 degrees with a mass of 1 kg reaches 95 % of top speed after travelling approximately 1200 m. This value was measured for low-speed flight, and it could plausibly decline to 0.07 at high speeds. Given enough time, ideal falcons can reach top speeds of 89-112 m s-1 in a vertical dive, the higher speed for the heaviest bird, when the parasite drag coefficient has a value of 0.18. The top speeds reached during a dive depend on the mass of the bird and the angle and duration of the dive. Ideal falcons have body masses of 0.5-2.0 kg and morphological and aerodynamic properties based on those measured for real falcons. This study investigates the aerodynamic and gravitational forces on 'ideal falcons' and uses a mathematical model to calculate speed and acceleration during diving. Estimates of their top speed in a dive range up to 157 m s-1, although speeds this high have never been accurately measured. Some falcons, such as peregrines (Falco peregrinus), attack their prey in the air at the end of high-speed dives and are thought to be the fastest of animals.
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