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 salmon culturally prized among certain Native American tribes. Many celebrate the first spring Chinook caught each year with "first-salmon ceremonies". While salmon fishing is still important economically for many tribal communities, the Chinook harvest is typically the most valuable. Chinook salmon were described and enthusiastically eaten by the Lewis and Clark Expedition. Lewis wrote that, when fresh, they tasted better than any other fish he had ever eaten. They did not particularly like dried or "pounded" salmon. Lewis and Clark knew about Pacific salmon, but had never seen one. The Western world had known about Pacific salmon since the late 18th