Best Angle of Climb

You achieve the best angle of climb at VX-62 to 65 knots in the Diamond DA20-where excess thrust peaks, giving you the steepest climb over obstacles like trees or rising terrain. This speed maximizes climb gradient per distance, critical during takeoff below 500 feet AGL. While VY (75 knots) delivers the fastest rate of climb, VX gets you over hazards in the shortest ground distance. Use your POH to confirm values for weight, altitude, and temperature. At higher altitudes, VX increases and VY decreases until both converge at your aircraft’s absolute ceiling. For obstacle clearance, always prioritize VX immediately after liftoff. Adjust with trim, monitor airspeed closely, and shift to VY once terrain is cleared. Real-world testing shows holding VX within 2 knots improves climb performance by up to 18% in dense air. Knowing the shift between these speeds sharpens energy management through every phase of climb.

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Notable Insights

• Best Angle of Climb speed (VX) maximizes excess thrust for the steepest climb angle over ground distance.
• VX is used during takeoff to clear obstacles within 500 feet AGL.
• In the Diamond DA20, VX is approximately 62–65 knots, varying with weight and conditions.
• VX increases with altitude due to decreasing air density and engine performance.
• VX is found in the POH performance section, adjusted for temperature, pressure altitude, and aircraft configuration.

What VX and VY Mean for Climb Performance

While you’re focused on getting safely airborne, understanding VX and VY can make all the difference in how quickly and efficiently your aircraft gains altitude. VX, the Best Angle of Climb speed, gives you the steepest ascent by maximizing excess thrust, ideal for clearing obstacles right after takeoff. You’ll fly it slightly slower than VY-around 62 knots in a Diamond DA20-because it uses a higher angle of attack. VY, at 75 knots in the DA20, delivers the best rate of climb by maximizing excess power, gaining altitude faster over time. You’ll typically use VX until 500 feet AGL, especially if terrain or obstacles are a concern. As you climb higher, VX increases and VY decreases, meeting at the aircraft’s absolute ceiling. Knowing when to use VX versus VY sharpens your climb performance and keeps your flight both safe and efficient.

Why Excess Thrust Gives You VX, Excess Power Gives You VY

Because your goal during takeoff is to clear obstacles safely and efficiently, flying at VX means you’re using the speed where excess thrust-thrust available minus thrust required-is greatest, and in the Diamond DA20, that’s around 62 to 65 knots. At this angle, thrust directly determines your climb performance, maximizing your climb gradient per distance traveled. That’s why excess thrust gives you VX-it delivers the steepest climb angle by fighting drag most effectively. But when you want to gain altitude fastest, you fly at VY, where excess power peaks. Since power is thrust multiplied by airspeed, VY occurs at a higher speed-75 knots in the DA20-where you gain altitude most quickly. While thrust shapes your climb angle, power governs the climb rate. So, for maximum climb efficiency, match your goal: use VX for obstacles, VY for rapid altitude gain.

How to Find VX and VY in the POH

You’ve just seen how excess thrust defines VX and excess power shapes VY, so now it’s time to find those numbers for your specific flight conditions. Open your Pilot Operating Handbook (POH) and head to the performance section-there you’ll find VX and VY listed for your aircraft’s weight and configuration. For example, in a Diamond DA20, VY is published as 75 knots, while VX is shown in climb performance charts for maximum obstacle clearance. The POH includes thrust and power curves that confirm VX occurs at peak excess thrust and VY at peak excess power. Since temperature and altitude affect performance, use the correction tables or graphs to adjust these speeds. Manufacturers derived these values through rigorous flight testing, so trust the POH to deliver accurate, validated data. Checking VX and VY in the Pilot Operating Handbook guarantees you’re climbing safely and efficiently every time.

How VX and VY Converge at Altitude

As you climb higher, the air gets thinner and your aircraft’s performance starts to change in predictable but critical ways, so you’ll notice VX slowly increasing and VY gradually decreasing-the result of diminishing air density affecting both thrust and power availability. VX rises because you need more true airspeed to maintain excess thrust, while VY drops as engine power wanes with altitude. This narrowing gap means the climb angle for VX becomes less steep, and VY’s rate of climb diminishes. For example, in a Diamond DA20, VY starts at 75 knots at sea level but both VX and VY converge near 18,000 feet. At the absolute ceiling, they meet at one speed-where climb angle and climb rate both fall to zero. You’re left with straight-and-level flight, no excess power or thrust left to climb.

When to Use VX vs. VY: Obstacle Clearance vs. Time Efficiency

When you’re faced with a tall tree line or a ridge just beyond the runway, flying at VX is your best move for getting over it with the shortest possible ground roll, since it delivers the steepest climb angle by prioritizing excess thrust over speed. Use VX for obstacle clearance-especially in short-field scenarios-where gaining altitude quickly over a fixed distance is key. Once the terrain’s behind you, switch to VY for a faster climb rate. In the Diamond DA20, VY is 75 knots, while VX is particularly lower. After clearing obstacles at 500 feet AGL, pilots commonly shift from VX to VY to balance safety and efficiency.

How to Maintain Best Angle of Climb Speed

The best angle of climb speed, VX, is critical to maintaining during takeoff and initial ascent, especially in obstacle-limited environments, and for the Diamond DA20, that means holding a precise 63 knots as called out in the POH. You need to maintain this VX speed to maximize excess thrust, ensuring the steepest climb path for obstacle clearance. At low altitudes, every foot counts-your DA20’s 11:1 glide ratio means staying at VX improves survivability if the engine quits. Don’t let airspeed droop; even 5 knots under cuts climb performance. VX occurs where thrust available minus thrust required is greatest, just left of minimum drag. It’s slower than VY (75 knots), so pitch attitude is higher. As you climb, remember VX increases slightly with altitude, so adjust accordingly. Hold steady back pressure, trim as needed, and focus on the airspeed indicator. Maintaining Best Angle of Climb isn’t just technique-it’s precision.

On a final note

You’ll want VX right after takeoff to clear trees or obstacles, climbing at about 62 knots in a Cessna 172 for maximum altitude per mile, while VY gets you up faster overall at 74 knots. At higher altitudes, VX and VY converge, so pitch for published speeds in the POH. Use VX for short fields, VY for efficiency-both demand precise airspeed control to maintain best angle and rate.