I recently had a small crash when the P3P flipped onto its front 2 rotors while landing. No obvious signs of damage and all was fine. I cashed it again from about 1.5m off the ground when it clipped a bush in thick forest, again no obvious signs of damage and it all worked fine. However, we noticed a very slight change in the pitch of the sound when it took off next, we flew it for another 2 or 3 hours over the next couple of days without problems and it all seems fine. I can't help having concerns about what is causing the tiny change in sound. I have tried listening to the engines carefully, and I cannot hear any difference between the engines. No obvious sounds of bearing or other problems. Could it be just the minor scratches to the rotor blades themselves that made the change? I have a spare set of carbon fiber rotors but I figure they could sound different anyway so not sure what to do. All seems fine. Anyone with any thoughts on this?