Woops, I just realized that that link was to a specific website. I thought it was directing me to google.
I read that article over and over again, and added it to my collection of AC, and aerodynamic articles, before I posted my question on here. The school I am with that are preparing me for my CPL checkride are requiring me to explain WHY everything happens. And that article doesn't answer it. I agree with how the second to the last paragraph is misleading.
So my question is, why does Vx continue to increase with altitude? Is it because of increasing TAS as you continue to climb, decreasing the prop efficiency? And increasing the speed changes your angle of attack and allows you to produce the same amount of lift at for example 5,000 than at 1,000, by permitting more air over the wing? Or maybe it’s because you’re trying to fulfill the second part of the definition of Vx: for a given horizontal distance? If you maintain the same speed of Vx at 5,000 when it’s designated for sea level, that given horizontal distance would change (talking in calm air conditions of course). It would get shorter. I have a hunch it's really the second answer, but am not sure.
Vy is simply based off of excess power. The higher you climb the amount of thrust decreases due to decreasing prop efficiency because of relative wind. The part I don't understand is WHY. Rods article, however, says it is the greatest deflection on the VSI, which confuses me and makes me think that your trying to climb as fast as possible, implying that that speed should be used for short field takeoffs on the initial climb. So I just blacked out that sentence on the printed article in my binder. Doesn’t Vx give you the greatest needle deflection? Does Vy decrease because while your climbing, TAS is getting greater, which increases your Total Drag (Power required), and Power available decreases? That doesn't really explain why your IAS would decrease though.
Finally, TAS increases with altitude due to air density decreasing and more airflow required to fly over the wings in order to produce the same amount of lift at higher altitude, correct?
Your help is much appreciated gentlemen.