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posted: 5/19/2014 11:28 AM

Airplanes, helicopters both fly, but in different ways

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  • Adler Park School students watch as a United States Army National Guard Blackhawk helicopter lands in Libertyville as part of a Veterans Day event at the school.

       Adler Park School students watch as a United States Army National Guard Blackhawk helicopter lands in Libertyville as part of a Veterans Day event at the school.
    Paul Valade | Staff Photographer, NOVEMBER 2012

 

You wanted to know

"Why is a plane faster than a helicopter," asked Grayslake Library patrons attending the "Novel Detectives" class.

If you wanted to enjoy the newest ride at Tokyo Disneyland, you'd book a seat on an airplane. But if there was a call to stage a rescue operation when backpackers were stranded on a mountain, you'd jump into your helicopter and lift off, maneuvering close to the rocky peaks so you could relay the climbers back home.

"While airplanes and helicopters both travel through the air, they have very different characteristics and purposes," explained Kevin Cassel, associate chair, Mechanical, Materials, and Aerospace Engineering Department at Chicago's Illinois Institute of Technology.

Cassel said airplanes are the workhorses that transport for the long haul.

"Airplanes are designed to travel long distances quickly between airports made for this purpose. Other than during takeoff and landing, they typically travel at relatively constant speeds in nearly straight lines between airports.

"This allows aerospace engineers to design them to be very effective -- fast, quiet, comfortable, large cargo or passenger capacity -- and efficient regarding fuel consumption for long range flights."

Planes need lift, thrust, force and drag in order to lift off and fly. Speed links together the four needed principles.

"An airplane must be moving at sufficient speed in order for the wings to generate the vertical lift force necessary to get and keep it in the air. This is why runways must be so long, in order to give the plane enough time during takeoff to reach sufficient speed for flight," Cassel explained.

Japan Airlines' fleet includes the new Boeing 787 Dreamliner, which can fly to an airport near the newest Tokyo Disneyland rides using 20 percent less fuel than previous commercial airplane models.

"The new Boeing 787, for example, normally flies at 570 miles per hour and has a range up to approximately 9,000 miles," he said.

The big difference between planes and helicopters is how they create lift.

"A helicopter generates lift simply by spinning its rotors very rapidly; it does not need to be moving in order to generate lift," Cassel noted.

"Whereas an airplane is designed to always be moving forward and can only make gradual turns, a helicopter can move in any direction, including forward, backward, up, down, right, and left, once again leading to its versatility."

Because of its design, helicopters can perform very specific duties.

"Once in the air, helicopters can carry out a wide variety of missions. They can hover at a particular spot to observe a building fire or traffic incident. They are ideal for transporting medical patients to hospitals. They are used extensively in the military," Cassel said.

A common helicopter seen in Chicago used by news stations, police, and hospitals has a maximum speed of about 140 miles per hour and a range of approximately 400 miles.

Whereas the Boeing 787 could fly from Chicago to Los Angeles in three hours, the helicopter would take more than 12 hours, not counting the four stops it would need to make along the way to refuel."

Cassel, his colleagues and students are working on several research projects using their area of expertise -- fluid dynamics.

In one project with the U.S. Air Force, the team is exploring methods to enhance the maneuverability of small, unmanned and micro-air vehicles.

As the principles for flight are similar to those used to operate certain medical equipment, his team also is developing a model to examine effects of blood flow on a heart valve.

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