This crack originates in the radius where the spar cap angle flange ends, and propagates towards the second bolt hole. Although a crack at the second bolt hole is important, the spar cap angle need not be replaced if this crack is found. Cracks in this location are much more serious, and could result in wing separation. Further, imprinting on the doubler plates of aircraft with cracked spar cap angles confirms that torsional stress is applied to the spar assembly. The difference in the failure rate of the lower spar cap angle is presumably due to gross weight and brake strength differences between the two models.
Renegades are heavier and have more powerful brakes.
Although none of the affected Lake models have a history of in-flight wing separation, the cracks discussed above have the potential to result in wing separation in due time. Aircraft that do not comply with the AD within the specified time become grounded. The final AD requires that the spar doubler plate be inspected visually, which can be accomplished without removing or disassembling the wing. If cracks are found in the spar doubler plate, the part must be replaced, which effectively means replacing the entire wing. Installation of the kits does not require wing removal.