So, I flew a x-c last year in the middle of summer. I was in the clouds for maybe half an hour on the way there. When I returned to my FBO and was paying for the flight the guy there commented "You know it's not legal to fly that airplane in IMC, it doesn't have pitot heat" Stating that if I were to have a ramp check I would've been busted. It's a piper cherokee and it indeed does not have pitot heat. I went home that night and tried to find a reg about it, but I can't for the life of me. For 135 ops (135.163) it is required to carry passengers, does anybody know is it required under part 91? This is the only plane (IFR) I've ever flown, that didn't have pitot heat.