12/1/2023 0 Comments Coast rider desent angle![]() So now our fictitious ride is over, but it still leaves that gale force question: since the speed and direction of riders and the winds they encounter are infinitely variable, how can manufacturers say the sweep of yaw angles they’ve chosen for optimising the aero shape of their frames and wheels is the right one? It’s time to shoot the breeze with the experts. ![]() So speed affects yaw angle too: go faster and the yaw angle gets smaller. This now-stronger force pushes the thread back closer to the due south line of the rear wheel and makes the yaw angle smaller. Imagine you start down a steep descent, where your increased speed also increases the effective headwind you’re creating for yourself. For example, a few miles down the road in your hypothetical ride, the westerly wind could suddenly whip up and push even further to the east to open the yaw angle wider.īut that’s not all. So while lift (positive or negative) from angle of attack is a factor, it is only one of many.Of course, the wind, your speed and the relative direction of one to the other change constantly throughout a ride. ![]() The downward forces obviously include gravity, but could also include thrust from engines and negative lift from aerodynamic surfaces. ![]() The upward forces acting on any object descending through the air can include drag from air resistance, lift from aerodynamic effects, and thrust from engines etc. If the wings fell off your aircraft, you would still descend and you still wouldn't experience sustained freefall.ĭoes that mean the net downward force is not gravity, but less than gravity, due to certain lift acting at all negative angle of attacks? even if negative angle of attack is large.Īngle of attack is not actually relevant here. Aerobatic maneuvers can often result in zero or even negative G forces. The passengers on the vomit comet experience free fall even after the aircraft has peaked and has started to descend. Freefall just means falling at the same rate you would accelerate under gravity. When descending, an aircraft never goes in free fall, Note: For purposes of this answer, I'm defining 'lift' to be "the sum of all forces acting on the aircraft in the opposite direction of gravity" in order to keep things more simple. During a normal descent, angle-of-attack is always positive. Pitch angle (angle of the nose relative to the horizon) can be quite negative while still maintaining a positive angle-of-attack. As Jan Hudec's answer mentions, this is a necessary consequence of Newton's Second Law.Īs others have mentioned, remember that pitch angle and angle-of-attack are two totally different things. Any time when the rate of climb or descent is constant, the lift is equal to the entire weight of the aircraft. That is, when the aircraft changing its rate of climb or descent. The only times that lift is not equal to weight are the times when the aircraft is accelerating upwards or downwards. If the lift were less than the weight of the aircraft, then the aircraft would be accelerating downwards. In an aircraft that is descending at a constant rate, not only is there lift acting on it, but that lift is equal in magnitude to the aircraft's weight. in the Vomit Comet) and if it went negative, you'd raise from your seat as the aircraft would be accelerating downward faster than free fall, but you only have gravity pulling you down, so you'd lag behind it.īesides the above linked, you may also want to look at the chapter 2 Angle of Attack Awareness and Angle of Attack Management of the abovementioned How It Flies book, for detailed treatment of the relationship between Angle of Attack and pitch, and any other section too it does quite a good job explaining the physics related to flying. If it decreased more, you'd surely notice: if it decreases to zero, you'll feel weightless (e.g. However usually it only decreases by maybe 10–20%. The lift is only decreased when initiating descent, so the plane needs to accelerate downward in order to change direction. While drag is slanted slightly upward in descent, and thrust might be depending on the resulting pitch attitude, in normal descent the only force with large upward component is still lift, and therefore it must still be almost equal to weight to get the forces in balance. (Image from How It Flies, chapter 4 Lift, Thrust, Weight, and Drag) Now there are four main forces acting on an airplane: Therefore the sum of forces acting on it must be zero. In a steady descent, an aircraft is not accelerating, it is just flying with a constant velocity pointing obliquely downward. The Newton's second law of motion tells us that acceleration of object equals sum of forces acting on it divided by its mass.
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