so i binned my 5inch pretty hard into a concrete wall last weekend at the skatepark. my fault, was pushing too hard and misjudged a gap. anyway the obvious damage is M2 motor is completely seized, blade is shattered, and the arm on that corner has a visible crack running about halfway up. the arm didnt fully snap but theres definitely flex in it when i squeeze it that wasnt there before.

the motor itself im not too worried about, ive swapped motors plenty of times and i already ordered a replacement T-Motor F40 to match the other three. but im genuinely unsure if i should bother replacing the motor if the arm is compromised. like is a cracked arm a "replace the frame" situation or a "maybe it'll hold" situation. the frame is a TBS Source One v4 so replacements arms are at least easy to find, i just dont know if the crack is structural enough to matter at 5inch power levels.

also the stack seems fine, plugged it in on the bench and FC booted, ESC responding, motors 1 3 4 all spin on command. so at least i didnt fry anything expensive.

cracked arm is a replace it situation, full stop. i know it feels like it might hold but at the kind of vibration a 5inch generates you're just asking for it to finish cracking mid-flight, probably somewhere inconvenient like 30 feet up. Source One arms are like what, 8 bucks? just order two (always order two) and do it right while you've already got everything torn apart for the motor swap.

also while you have it open check the motor screws on the other three, crash vibration works screws loose in ways you don't always notice. i've had a motor come off mid-flight after a crash because i didn't check and the screws had backed out halfway.

yeah dont fly on a cracked arm man. had a similar thing happen with my old Armattan and i told myself the same thing you're thinking, the crack doesnt look that bad. frame gave out on the second flight and took the whole quad into a pond. lost the GoPro too which was the really painful part lol. arms are cheap, electronics are not.