Does it fly?
Not yet. We require additional funding to construct the model that will incorporate all of our accumulated research and knowledge from the past two years into our final version that we believe will fly.
A brief synopsis:
Since May of 2011, we have been researching and building platforms in a concentrated effort to build a human powered helicopter that is simple, reliable, and has the potential for practical recreational use. Having worked arduously over the past two years to reduce the amount of energy required for human powered vertical flight, we have found that the fundamental aspect of human powered flight is the efficiency of the rotor. We are now confident that we can build a flying human powered helicopter.
Why is the rotor design so important?
Most engine powered helicopters use a symmetrical airfoil for the rotor which produces no lift a zero degrees angle on attack, and thus requires an increase in the angle of attack to create lift. In our evaluations we have found that for any airfoil, an angle of attack over zero degrees even when an airfoil is not stalled, produces massive amounts of trailing wake vortices (these are not the same as the well known wingtip vortices). Essentially, the rotors are traveling in the wake of the preceding rotor thus creating a turbulent airflow for the succeeding rotor. Trailing wake vortices are unavoidable with a rotor that operates at an angle of attack greater than zero. However, trailing wake vortices can almost be eliminated by using a cambered airfoil at or near zero degrees angle of attack.
The taper of a rotor is also crucial, not just because a strong taper reduces the well-known wing-tip vortices which consume a lot of energy, but also because a properly designed rotor can equalize the lift and drag along the span of the rotor, essentially giving the rotor a straight line lift curve, without the curve.
What makes the rotor so efficient?
The S1223 airfoil has a lift coefficient of 1.1 at 0 degrees angle of attack and drag coefficient of .02. (It is among the highest lift to drag ratios among single element airfoils)
-The Pitch/Angle of the Rotor
The rotor will be set at 0 degrees angle/pitch. This eliminates most trailing wake turbulence. This is crucial because the rotors are no longer rotating into the downwash of the of the preceding rotor, which creates a huge swirling airmass that drastically increases the energy required. (This is why the rotors of other human powered helicopters must rotate so slowly, to give the swirling airmass time to dissipate before a rotor encounters the downwash of the preceding rotor)
-The Taper of the Rotor
The rotor has a taper that produces the same amount of lift and drag along the entire span at any given point. This is very important because the speed of at the tip of a rotor is much greater than at the root. With rectangular rotors, the lift, and thus the drag, is highest at the tip which builds up and prevents the inner portion of the rotor from reaching its maximum efficiency. This taper also minimizes wingtip vortices as well.
So what does the rotor look like?
We believe that we have designed a helicopter that is so efficient that we can lift 300 pounds on 300 watts or less. This is less than half of the 750 watts required by other human powered helicopters.
How do you calculate your lift and verify it?
We use an Excel spreadsheet to calculate the lift by using Blade Element theory. Simply put, we divide the rotor into one inch segments and calculate the lift for that 1-inch segment. We need to do this because the speed increases at each segment of the rotor as it spans outward, vastly different from the wing of an airplane which has a constant speed over the wing along the span.
We verify our lift calculations by using digital automotive scales which show a decrease in the gross weight of the helicopter as lift increases.
What should the finished Helicopter look like?
Why two sets of rotor?
We use two sets of rotors, also called a co-axial configuration, because a tail rotor consumes approximately 20% of the energy of a helicopter and so with this design we are able to direct all of the pilots energy towards generating vertical lift without the tail rotor. This design also places the pilot directly below the rotors which allows the the greatest amount of stability.
How will you control it?
This model will be controlled by shifting the weight of the pilot. We are currently designing a cyclic control system for precision directional control.
Do you intend to compete in the Sikorsky Competition?
Yes, we do intend to. However, there are several other teams actively competing for the Sikorsky Prize, so we will still finish our project even if the prize/competition is already won before we finish. The primary focus of this project is to create a practical human powered helicopter that almost anyone can fly, not just to win a prize.
What is the Sikorsky Competition?
The Sikorsky Competition is a monetary prize of $250,000 to be awarded to the first team to build and fly an human powered helicopter under these conditions:
1. Fly for 60 Seconds
2. Make it 9.8 feet above the ground
3. Stay within a 10-Square meter area
More detailed information can be found here:
Risks and challenges
Almost all of the work for this project will be completed in Eastman, Georgia at the Aviation Campus of Middle Georgia State College, We have a minimal reliance on external resources to complete this project. All equipment that is needed is in the campus facility and for those few parts that we will have to order, we have multiple suppliers to select from should one be unable to supply us with the materials that we require.Learn about accountability on Kickstarter
- (30 days)