A CH-47's max allowable airspeed will vary with gross weight, altitude and air density, but the limitations chapter in the operator's manual specifies 170 knots (196 mph) as absolute maximum airspeed.
It's max speed is approximately 170 mph.
The Black Hawk is faster. Black Hawk is about 220 mph, while the Chinook is about 190. But, I have ridden in Ch47 Chinooks with a full complement of Marines, that had to slow down for the Black Hawk and Cobras to keep up. They are different aircraft for different jobs. All great aircraft.
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There are many different helicopter engines, most of them now jets
Primarily the large ones do, like the CH53 Sea-stallion and the CH47 Chinook. Those are large cargo choppers and they can taxi on the ground if they need to. Most of the smaller birds just have skids so they can just land and take off.
Cruising speed is about 150 mph.
The posted speed limit is the max speed.
About 170 mph.
The typical CRUISE speed of the formentioned two seat trainer style is about 90-105Mph. and the five seat turbine is about 130-145Mph. (as far as MAX speed, I have been to about 155Mph in a Bell 206).
The helicopter begins to fall because gravity is pulling its weight. As the helicopter accelerates, the air passing past the helicopter creates drag, as the helicopter continues to accelerate the drag Increases until the drag becomes equal to the weight, stopping it from accelerating. Even if the helicopter did not auto rotate it would still reach a terminal speed, however the terminal speed for the non auto rotating helicopter would be a lot higher and the helicopter would take longer to reach this speed.
It all depends upon which helicopter you mean: 1 knot ≈ 1.15 mph A Wessex helicopter had a max speed of 115 knots, meaning it could cover 93 miles in 93 ÷ (115 x 1.15) x 60 mins ≈ 42.16 mins A Wasp helicopter had a max speed of 120 knots, meaning it could cover 93 miles in 93 ÷ (120 x 1.15) x 60 mins ≈ 40.41 mins A Sea King helicopter had a max speed of 125 knots, meaning it could cover 93 miles in 93 ÷ (125 x 1.15) x 60 mins ≈ 38.79 mins A Lynx helicopter had a max speed of 160 knots, meaning it could cover 93 miles in 93 ÷ (160 x 1.15) x 60 mins ≈ 30.31 mins Those figures are from pre 1980. A Lynx in 1986 reached 249.1 mph, meaning it could cover 93 miles in 93 ÷ 249.1 x 60 mins ≈ 22.40 mins An unofficial record of 299 mph by a Sikorsky X2 (compound helicopter) in 2010 means it could cover 93 miles in 93 ÷ 299 x 60 mins ≈ 18.66 mins
They change the speed and angle of rotor, and speed of tail propeller.