Rob, I love your programs but this doesn't answer WHY, it answers how. The reason why is much much simpler. Your excess thrust decreases as altitude increases, resulting in less "excess thrust" which in turn requires you to lower your AOA eventually it will be the same as Vy. VY will have to decrease for the same reason.
Greetings Ron: Yes, you are correct. I should have named it, "How" not "Why." Nevertheless, I did indeed want to answer "how" since this, to me, was the far more interesting question. Thanks for that input. Best, Rod
@@Flight-Instructor this is more or less what I meant in my comment that I just wrote - as engineering students, the why is the more interesting question (because we should understand how it works, obviously). Nonetheless, this "how" was new to me as well. Many thanks for the quality video.
@@mrsmith8224 Im confused by your statement. Pilots Handbook Aeronautical Knowledge Pgs 11-7 and 11-8 say this. Vx depends of Excess Thrust. Vy depends on excess power. Thrust measured in pounds. Power is the amount of work, thrust is creating in a moment of Time.
the convergence of best angle and climb rate to the ceiling was a new concept to me that I had missed before! thank you for the clear explanation on the curves. In future, could you go more into depth physics wise? showing the governing equations, for example, that make the ROC curves, just to help mesh together all the concepts (they are still not perfectly connected in my mind, I am working on it). I ask for this not as a pilot in training, but as an aerospace student. Thanks again!
By now, you can probably explain it to us. It's complicated. That's why they collect tons of data for these performance charts. This is computer-simulation territory, not something you can do by hand, on the back of an envelope. Thrust is easily derived from net power and airspeed, but net power (after efficiency losses) varies as a function of density altitude and airspeed. Not only does engine performance vary with rpm and density altitude, but the efficiency of a fixed-pitch propeller varies greatly with airspeed.
Thanks for the video. But why is meeting point of Vx and Vy has to be the service ceiling? In other word, what is service ceiling to do with Vx or Vy? And one more question. Is Vy always bigger than Vx? I feel like it is but can’t explain why
I’m not rod mochado, but I believe Vx is associated with higher AOA, higher induced drag, and lower parasite drag. While Vy is lower AOA, lower induced drag, but higher parasite drag.
Found this 3-page response dating back to 2005 about the same question, answered by none other than Rod Machado. As a ground school instructor, one of my students asked this question too, as to the why of the matter. Really good question. This video, combined with the attached link to said response, is a really good answer and has shored up this particular hole in my own understanding on the matter. cospilot.com/documents/Why%20Vx%20and%20Vy%20Change%20with%20Altitude.pdf
This is amazing. Could anyone please elaborate on the tangent line to the VS vs TAS graph, and why those tangent lines define the best angle of climb speed? I understood the statement, but not the why that is.
Tangent line gives the highest slope of the line intersecting the zero point and the graph. Slope has unit of FPM/KTS which gives the ratio of the vertical distance traveled over horizontal distance travel (over a given amount time). This ratio is directly correlated to angle since angle is Tan-1(Vertical/Horizontal). Hence Vx: best angle of climb :)
Rob, I love your programs but this doesn't answer WHY, it answers how. The reason why is much much simpler. Your excess thrust decreases as altitude increases, resulting in less "excess thrust" which in turn requires you to lower your AOA eventually it will be the same as Vy. VY will have to decrease for the same reason.
Greetings Ron:
Yes, you are correct. I should have named it, "How" not "Why." Nevertheless, I did indeed want to answer "how" since this, to me, was the far more interesting question. Thanks for that input.
Best,
Rod
@@Flight-Instructor this is more or less what I meant in my comment that I just wrote - as engineering students, the why is the more interesting question (because we should understand how it works, obviously). Nonetheless, this "how" was new to me as well. Many thanks for the quality video.
To be technical correct use term power instead of thurst as we are talking GA piston aircraft
@@mrsmith8224 Im confused by your statement. Pilots Handbook Aeronautical Knowledge Pgs 11-7 and 11-8 say this. Vx depends of Excess Thrust. Vy depends on excess power. Thrust measured in pounds. Power is the amount of work, thrust is creating in a moment of Time.
i realize I'm kinda randomly asking but does anybody know a good website to stream newly released tv shows online ?
the convergence of best angle and climb rate to the ceiling was a new concept to me that I had missed before! thank you for the clear explanation on the curves.
In future, could you go more into depth physics wise? showing the governing equations, for example, that make the ROC curves, just to help mesh together all the concepts (they are still not perfectly connected in my mind, I am working on it).
I ask for this not as a pilot in training, but as an aerospace student.
Thanks again!
By now, you can probably explain it to us. It's complicated. That's why they collect tons of data for these performance charts. This is computer-simulation territory, not something you can do by hand, on the back of an envelope.
Thrust is easily derived from net power and airspeed, but net power (after efficiency losses) varies as a function of density altitude and airspeed. Not only does engine performance vary with rpm and density altitude, but the efficiency of a fixed-pitch propeller varies greatly with airspeed.
Thanks for the video. But why is meeting point of Vx and Vy has to be the service ceiling? In other word, what is service ceiling to do with Vx or Vy?
And one more question. Is Vy always bigger than Vx? I feel like it is but can’t explain why
Really like your videos. What is the relationship between angle of attack and Vx/Vy?
I’m not rod mochado, but I believe Vx is associated with higher AOA, higher induced drag, and lower parasite drag. While Vy is lower AOA, lower induced drag, but higher parasite drag.
V(NE) how to explain how and why it changes?
very nicely explained!
this will be very helpful when i enter the flight academy in july!
thanks rod! ;)
keep up the amazing work
Alfa .Flyer how did it go?
Found this 3-page response dating back to 2005 about the same question, answered by none other than Rod Machado. As a ground school instructor, one of my students asked this question too, as to the why of the matter. Really good question. This video, combined with the attached link to said response, is a really good answer and has shored up this particular hole in my own understanding on the matter.
cospilot.com/documents/Why%20Vx%20and%20Vy%20Change%20with%20Altitude.pdf
Thanky you, Gavin. I sure do appreciate the thoughtful comment.
Best,
Rod
THANK YOU SO MUCH, AMAZING.
This is amazing. Could anyone please elaborate on the tangent line to the VS vs TAS graph, and why those tangent lines define the best angle of climb speed? I understood the statement, but not the why that is.
Tangent line gives the highest slope of the line intersecting the zero point and the graph. Slope has unit of FPM/KTS which gives the ratio of the vertical distance traveled over horizontal distance travel (over a given amount time). This ratio is directly correlated to angle since angle is Tan-1(Vertical/Horizontal). Hence Vx: best angle of climb :)
Great video, but make this very complicated
talk about the guy in Denver who over loaded his plane in the summer heat..
Actually, I already have a video on that fellow. Good point.
Best,
Rod
Rod Machado what a shame it happened...
thank you Rod
Thanks.
I believe that speaking about TAs can really confuse you. What really pilot is checking is the ASI. Rod anyway has the best video on line!!
Or just follow the POH.