By Chris Broadie
We’ve long known that higher launch and lower spin is a powerful combination for generating consistently long and straight tee shots. A key factor in optimizing launch conditions, one often overlooked, is angle of attack. Improved diagnostics and trajectory modeling shed new light on the importance of angle of attack in maximizing driving performance.
In the graph above, with a 167-mph ball speed, carry distance is optimized with a 17° launch angle and a spin rate between 2,000 and 2,500 rpm. Players with slower ball speeds may need a little more spin to keep the ball in the air to maximize carry. The net effect stays the same, though: very high launch and relatively low spin optimize distance.
In 2018, the highest average launch angle on the PGA Tour belonged to Sam Saunders at 14.7°. If a 17° launch angle maximizes distance, why does no one on the PGA Tour launch their driver that high? The answer is angle of attack.
To explain why, we first need to understand ball-flight laws. Ball-flight laws determine, for a given angle of attack and loft presented at impact, how high the ball will launch. If launch angle was determined entirely by the club face, then the ball would launch with exactly the presented loft at impact (100% toward the face). If launch angle was determined entirely by the path of the club, then the ball would launch along the angle of attack (0% face). As a sanity check, we know that a negative angle of attack does not launch the ball into the ground, so launch angle should be primarily determined by the loft at impact (>50% face). In fact, according to research conducted at the PING Proving Grounds, on a driver the ball will launch 85% toward the face.
According to Trackman, PGA Tour golfers have an average angle of attack (AoA) of -1.5° on a driver. For a -1.5° AoA and desired launch of 17°, the delivered loft at impact needs to be 20.25° in order to satisfy our 85% ball-flight laws. (Explanation: The presented loft is 21.75° greater than the AoA, the ball launches 85% of the way toward the face (21.75° * 85% = 18.5°), which results in a 17° launch (-1.5° + 18.5° = 17°).
However, this simply isn’t practical for a PGA Tour golfer. Hitting a ball at a “glancing” angle of 21.75° (20.25° delivered loft minus -1.5° AoA) reduces ball speed and would likely result in 4,500 rpm of spin. Therefore, the recommendation would be to try less loft, as this can result in a lower launch angle, less spin and greater ball speed. This now becomes an optimization problem to find the perfect loft. Through impact modeling and ball-flight simulation, we can evaluate all the potential lofts and pick whichever loft maximizes distance.
In our simulation, the launch conditions range from 171.3 mph ball speed, 3.8° launch angle, and 980 rpm spin at the lowest loft, 168.1 mph ball speed, 10.4° launch angle, 2,760 rpm spin at the optimal loft, and 157.2 mph ball speed, 20.5° launch angle, 5,450 rpm spin at the highest loft. Interestingly, the projected optimal launch angle of 10.4° and back spin of 2,760 rpm closely matches the actual PGA Tour averages of 10.9° launch angle and 2,686 rpm spin rate. The best golfers in the world, naturally, have gravitated toward the launch conditions that optimize performance for their given attack angle.
