If a propeller is turning 3,000 rpm and is 48 inch pitch is the theoretical forward speed 136 mph? (3,000 rpm x 60 minutes x 4 ft / 5280 ft = 136.3636 mph)
Obviously drag and slip will reduce this.
I ask because then a 400 mph airplane would need at 3,000 rpm a prop with over 12 feet of pitch and I don't know if that is possible.
Just a curiosity.