The Fastest Chopper On The Planet By Sirkosky

I still remember my childhood when I used to come running all over leaving everything else aside only to see a helicopter in the clear blue sky.The choppers have always fascinated me even more than the normal aircraft. Since then, I used to wonder how these helicopters manage to fly at such great speeds with a fan overhead? Today I happened to read about this ultimate flying machine and I decided to put my thoughts into words.

A Helicopter is a machine which can save your life when you are in trouble. For instance, most of the rescue operations during floods, earthquakes are done by the choppers. It can standstill besides a mountain to track the lost mountaineers. Moreover it is used to supply food to the soldiers which are on the pinnacle of the mountains. A modified Westland Lynx in 1986 claimed the top speed of the helicopter as 400 km/ hour.  But today's working helicopters have a maximum speed of 270 km/hour. The Sikorsky Aircraft corporation, in 1970’s, decided to build a helicopter that would fly are a whooping speed of 480 km/hour without compromising the mechanical strength of the vehicle. It has been 40 years since then and Sikorsky is very close in achieving that goal.

The X2, a technology demonstrator, reached a speed of 435km/hour and broke the speed record unofficially in august 2010. Now as they have come this far in this journey, they claim to make choppers with the X2 technology. To beat the record, they had to resign the helicopter the reason for which is evident in the flying mechanisms of a plane and that of a helicopter. Air flows over the wings of a plane when it moves on a runway which provides the lifting thrust. Once the plane has taken off, the thrust depends upon the power developed by the engines. Basically the rotor blades make the design a bit complex. Each blade should be able to handle the rotational force. This force is much more than the force exerted by the weight of the chopper on one lade. So, now you can imagine how complex the mechanism is.

It requires a powerful engine with reduced speed of rotation so as to suit the large rotor blades. Take the example of a U.S. Army UH-60 Black Hawk. Its main engine shaft rotates at a speed of 20,900 rpm which is reduced to 258 rpm . This makes it a 81:1 ratio. This is huge! But the difficulty here is that the blades experience a strong varying force as the helicopter moves forward. If it is hovering, we can feel the wind coming at us with a speed of 800 kmph. When the blades move in the same direction as that of the helicopter a tremendous force is exerted on the blades. This force will be reduced when the blades are in the retreating phase.  So, when the helicopter has notched up to 150 km/hour, we will feel a wind speed of 950 km/hour in the advancing direction and that of 650 km/hour in the backward direction. The speed of the wind on the retreating side goes on reducing as the helicopter moves faster.

At a particular value of forward speed, the force in the advancing position of the rotor will be so huge than the retreating one, that a controlled flying pattern will be difficult to maintain. Moreover to worsen the situation, the speed of the  tips of the advancing blade may exceed the speed of sound producing shock waves which in turn produce a lot of noise and disturbance. This is the problem faced by Sirkosky and hence till today a speed of 435km/hour is possible.

I am quite sure that this problem will be dealt with after having a review of the chopper design. If this happens it would be another engineering marvel. So, people, hold your breath and fasten your seat belts!