The amount of power you have available to climb is the difference between the thrust line blue and the drag curve black. But, if you measure it, this doesn't happen at the lowest point of the curve! The largest space between thrust available and thrust required happens a little to the left of that point. Because of the slope of the thrust available line.
That's your Vx speed. Check out the animated GIF below:. To figure out where Vy is, you need to draw a power required curve. What's that? Power is work done per unit of time. So, you can compute power required by multiplying your total drag force required by your airspeed distance over time. In America, we use some wonky units for both force and power.
As pilots, we generally think of thrust in terms of pounds. On a reciprocating engine aircraft, we measure power in "horsepower. If you multiply the force required in pounds against your true airspeed in knots, you'll get an accurate, but unrecognizable, number for power required. To convert it to horsepower, you'll need to multiply it by roughly. Don't bother - we'll do it for you. Take a look at the diagram below - this shows power required for level flight at different airspeeds:.
Now let's add power available. To draw this line, do the same thing - multiply thrust available by airspeed by about. Take a look:. Vy is the speed where you have the biggest difference between power required and power available. But, again, it's not at the lowest point of the power required curve - it's a little bit to the right.
Because of the shape of the power available curve. Now you know! Vx is the speed where you have the most excess force thrust , and Vy is the speed where you have the most excess power horsepower.
Did you know that Vx and Vy change with altitude? And, they're the same at your maximum ceiling? We'll save that for another post, because too many charts all at once is never a good thing.
If an object is pointed at an angle, the motion is essentially the same except that there is now an initial vertical velocity Vyo. Review of the Basics. It allows one to climb to altitude within the shortest horizontal distance. It allows one to climb to altitude in the shortest time. At this altitude, the power available curve crosses through the lowest point of the power required curve.
Vx and Vy change as DA goes up and change with weight. The power required PR curve moves up and shifts to the right slightly. Find the point of maximum separation between the two newly shifted curves the vertical red line.
Best Angle of Climb speed Vx gets you the greatest altitude per unit of ground distance feet per mile. Climbing at this speed will yield the greatest height gain per distance traveled. Drag and Airspeed Parasitic drag increases with the square of the airspeed, while induced drag, being a function of lift, is greatest when maximum lift is being developed, usually at low speeds.
The diagram below shows the relationship of parasitic drag and induced drag to each other and to total drag. Induced drag is greater at lower speeds where a high angle of attack is required.
Conversely, parasite drag increases as the square of the airspeed. Thus, in steady state, as airspeed decreases to near the stalling speed, the total drag becomes greater, due mainly to the sharp rise in induced drag. Considering the induced drag equation, there are several ways to reduce the induced drag. Wings with high aspect ratio have lower induced drag than wings with low aspect ratio for the same wing area. So wings with a long span and a short chord have lower induced drag than wings with a short span and a long chord.
On the other hand, you may hit them at a slower airspeed. That nose-high attitude also blocks your view of potential landing sites. If your engine fails your hands will be full of airplane for a time until you get the airplane and yourself under control. Only then will you be able to take a breath, and look for a soft spot, your first opportunity to do so.
This limits your choices. This is no small matter, and may in fact be the single largest reason to use a more gentle approach! The Deakin Method. In the first place, the tailwheel is on the wrong end of the airplane! Variations exist! This will yield the performance illustrated above - approximately.
If true of the Bonanza, it may also be true of other types. This produces maximum performance, and minimum runway used. Varying from this precise technique can have catastrophic consequences — in swept wing jets! When young CFIs began using this term in Cessna s and the like, I thought it was a complete affectation and it made me want to throw up.
It still does, but now everyone uses it! My own oft-stated technique with any GA airplane is to allow the airplane to assume a takeoff attitude and let it fly when it wants to, just above the stall.
What is the takeoff attitude? With a high-wing, it can be judged by the angle of the lower surface of the wing against the horizon.
This works very well with any nose-dragger, but calls for a tiny bit say two tries of experience with the tailwheel on the proper end. Again, we turn to Dr. Rogers, and his plots of this:. Due to the early increase in speed, the aircraft never operates in that red circle. Engine temperature will be cooler after the climb.
The liftoff is virtually imperceptible, there is no sharp nose-up to hold Vx or Vy, and the ground just seems to slowly fall away. Say the actual engine failure occurs at 30 seconds after liftoff.
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