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 Point was designated a National Historic Landmark in 1961. Chinook Point is a hilly promontory on the north bank of the Columbia River, roughly east of its actual mouth, which is marked on the north by Cape Disappointment and the south by Point Adams. The point is fortified with the remains of Fort Columbia, which include thirteen buildings erected in 1902, and three artillery emplacements installed between 1897 and 1900. The mouth of the Columbia River, the major river of the northwestern United States, was almost discovered several times before Captain Robert Gray spotted it in 1792. Spanish explorer Bruno de