Photo Gallery
Some photo of Wind Electricity project.
 

Smallest Airplane

Smallest Airplane
     
       
High altitude aircraft need to pressurize their cabins (pack more air in) in order to offset the decreased air density (and consequently the decreased amount of oxygen in the air) at the higher altitudes so passengers and crew can continue to breathe without the need for supplemental oxygen. The way they do this is by compressing the outside air and forcing it into the aircraft cabin thereby increasing air density and oxygen concentration. The increased pressure of this compressed air can create a force against the inside of the aircraft cabin, and windows, of up to around 8 pounds per square inch (though some newer airplane designs, such as the Boeing 787, use a slightly higher level of pressurization). The greater the surface area of a window, the greater the force of the cabin air pressure pushing against it and, consequently, the greater the likelihood of breaking out a window. By decreasing the surface area of the window, aircraft designers decrease the possibility of rupturing a window and losing cabin pressure. Hope that helps.

     The size and shape of the windows can weaken the fuselage structure. The first British jet airliner, the de Havilland Comet, began to experience sudden crashes from high altitude. After many tests, the engineers discovered that the large windown with square corners could cause a fatigue crack to develope in the sharp corner of the window. Fatigue was an unknown science at that time. They redesigned the windows to make the smaller with large round corners and the aircraft didn't have any more dramatic crashes.

How Does Helicopter Fly

How Does Helicopter Fly.

The rotor blades of a helicopter act in the same manner as the wings of a plane, creating lift by forcing air above and below a curved airfoil. The air moves faster over the top of the blade, reducing the pressure there. The air below pushes upward with greater pressure, lifting the rotor and the attached frame and cabin. At the same time, the blades can be angled in any direction, allowing it to move in any direction by using the blades like the propellers on an airplane. Jet helicopters also generate some forward speed from their turbine exhaust.
The main rotor is the set of blades on the top of the craft, driven by the engine (piston, jet turbine, etc.). By turning the blades, which are airfoils and like a narrow "wing" in shape, we move them through the air. And by "tipping" the leading edge of the blade up (increasing the pitch) as it moves, the blade will have a positive angle of attack. It will bite into the air and force that air down. This forces the blades up, and the rotor will provide lift. Lift causes the craft to defy gravity.


        The torque (rotational motion) of a single rotor blade will have to be offset, and the tail rotor does this. Additionally, the tail rotor (or air turbine in the NOTAR helicopter) will also allow the craft to be turned and "pointed" in another direction. The pedals control the tail rotor or air turbine. By pushing the stick to the side (and adding a bit more pitch with the cyclic), the blades can be controlled to allow a bit more lift on one side to tip or bank the chopper and turn it. (A bit more pitch is added to offset the slight loss of lift.) The pedals will also be used in conjunction with the stick. By pushing the stick left, the blades will have a bit more pitch as they come around on the right side and a bit less as they come around on the left side. This will bank and turn the helicopter.
Pushing the stick forward causes more pitch to the blades as they come around the back of the circle they make around the craft. This lifts the back of the craft. And it will make for a bit less pitch in the front for a bit less lift in front. This tips the craft forward. Often when we see a helicopter take off, it rises a bit, tips forward (now that the rotors will clear the ground), and accelerates forward as it continues to rise. The pilot has pulled up on the collective (to increase the pitch of the main rotor blades). That provided lift. He also has to push forward on the cyclic to tip the helicopter forward to begin to gather forward airspeed.

(for more information see the related links below)

A helicopter can take off and land vertically (straight up and down). It can fly in any direction, even sideways and backwards. It can also hover or hang in the air above a given place.

A helicopter gets its power from rotors or blades. When its rotors are spinning, a helicopter doesn't look much like an airplane. But the rotor blades have an airfoil shape like the wings of an airplane. So as the rotors turn, air flows more quickly over the tops of the blades than it does below. This creates enough lift for flight.

Additionally, helicopters avoid areas close to storms. The reason is that the helicopter requires a careful balance of the air supporting it. Downdrafts or turbulent winds can drastically affect control of the helicopter.

Automatic solar tracking system

Sunlight has two components, the "direct beam" that carries about 90% of the solar energy, and the "diffuse sunlight" that carries the remainder - the diffuse portion is the blue sky on a clear day and increases proportionately on cloudy days. As the majority of the energy is in the direct beam, maximizing collection requires the sun to be visible to the panels as long as possible.

The energy contributed by the direct beam drops off with the cosine of the angle between the incoming light and the panel. In addition, the reflectance (averaged across all polarizations) is approximately constant for angles of incidence up to around 50°, beyond which reflectance degrades rFor example trackers that have accuracies of ± 5° can deliver greater than 99.6% of the energy delivered by the direct beam plus 100% of the diffuse light. As a result, high accuracy tracking is not typically used in non-concentrating PV applications.

The sun travels through 360 degrees east to west per day, but from the perspective of any fixed location the visible portion is 180 degrees during an average 1/2 day period (more in spring and summer; less, in fall and winter). Local horizon effects reduce this somewhat, making the effective motion about 150 degrees. A solar panel in a fixed orientation between the dawn and sunset extremes will see a motion of 75 degrees to either side, and thus, according to the table above, will lose 75% of the energy in the morning and evening. Rotating the panels to the east and west can help recapture those losses. A tracker rotating in the east-west direction is known as a single-axis tracker.

The sun also moves through 46 degrees north and south during a year. The same set of panels set at the midpoint between the two local extremes will thus see the sun move 23 degrees on either side, causing losses of 8.3% A tracker that accounts for both the daily and seasonal motions is known as a dual-axis tracker. Generally speaking, the losses due to seasonal angle changes is complicated by changes in the length of the day, increasing collection in the summer in northern or southern latitudes. This biases collection toward the summer, so if the panels are tilted closer to the average summer angles, the total yearly losses are reduced compared to a system tilted at the spring/fall solstice angle (which is the same as the site's latitude).

There is considerable argument within the industry whether the small difference in yearly collection between single and dual-axis trackers makes the added complexity of a two-axis tracker worthwhile. A recent review of actual production statistics from southern Ontario suggested the difference was about 4% in total, which was far less than the added costs of the dual-axis systems. This compares unfavourably with the 24-32% improvement between a fixed-array and single-axis tracker.