Helicopter rotor of gravity fore-aft. However, it requires the expense of two large rotors rather than the more common one large main rotor and a much smaller tail rotor. The Boeing CH-47 Chinook is the most common tandem rotor helicopter. Coaxial rotors are a pair of rotors mounted one above the other on the same shaft and turning in opposite directions. The advantage of the coaxial rotor is that, in forward flight, the lift provided by the advancing halves of each rotor compensates for the retreating half of the other, eliminating one of the key effects of dissymmetry of lift: retreating blade
Chinook (dog) occurs in about 10% of all male dogs. The Chinook owes its existence to one man: Arthur Treadwell Walden of Wonalancet, New Hampshire. The breed derives principally from one male ancestor born in 1917, named "Chinook", who was Walden's lead dog and stud. "Chinook" derived from a crossbreeding of husky stock from the Peary North Pole expedition with a large, tawny Mastiff-like male. Photos of "Chinook" show a drop-eared dog with a broad Mastiff head and muzzle. Walden's leader was bred to Belgian Sheepdogs, German Shepherd Dogs, Canadian Eskimo Dogs and perhaps other breeds; the progeny were bred back to