Re: V_x and performance takeoffs - POH discrepancy
Posted: Wed Dec 26, 2012 3:39 pm
Wow.. this is one messed up thread! I really hope people don't come here to learn anything.
Vx is not maximum endurance and Vy is not maximum range! The difference in power settings will affect the speed to fly for maximum performance.
Then there is talk about an airplane at a standstill producing no power. The airplane that is stationary on the runway while at full throttle is producing lots of Brake Horsepower but the Thrust Horsepower is zero. I didn't see THP mentioned anywhere in that discussion... maybe I missed it.
Vx increases with altitude so I'm curious about the numbers Cessna published as quoted in the first post on this thread.
Vx is based on excess thrust and Vy on excess power - if you don't understand that intimately then I'd stop there and figure it out. There was a snippet from Aerodynamics for Naval Aviators that was posted here which had a portion of the section explaining that. If you understand everything about what they mean when they say "thrust" and "power" in the case of Vx and Vy, you'll also understand right away why a stationary airplane at full throttle is producing zero THP.
Vx is not maximum endurance and Vy is not maximum range! The difference in power settings will affect the speed to fly for maximum performance.
Then there is talk about an airplane at a standstill producing no power. The airplane that is stationary on the runway while at full throttle is producing lots of Brake Horsepower but the Thrust Horsepower is zero. I didn't see THP mentioned anywhere in that discussion... maybe I missed it.
Vx increases with altitude so I'm curious about the numbers Cessna published as quoted in the first post on this thread.
Vx is based on excess thrust and Vy on excess power - if you don't understand that intimately then I'd stop there and figure it out. There was a snippet from Aerodynamics for Naval Aviators that was posted here which had a portion of the section explaining that. If you understand everything about what they mean when they say "thrust" and "power" in the case of Vx and Vy, you'll also understand right away why a stationary airplane at full throttle is producing zero THP.