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
1978 Iranian Chinook shootdown damaged helicopter and opened fire with GSh-23L 23-mm gun, spending a total of 72 rounds in two passes and hitting the starboard engine of the CH-47C. The Iranian pilot was lucky enough to manage a landing near the Soviet border post at Gjaurs. All four crew members survived, but were subsequently captured by Soviet border guards. The remaining two Chinooks escaped, crossing back into Iranian airspace. Despite a severe loss of life for the IIAF, the incident was played down by both sides, and the Soviets subsequently permitted the damaged Chinook to be repaired by Iranians and flown back to