In 1956, a mid-air collision between a DC-7 and a Lockheed Constellation killed 128 people aboard. In 1978, 144 people were killed when a Boeing 727 and a Cessna 172 collided over San Diego. In 1986, a DC-9 and a single engine piper collided and killed 97 people. The congress finally passed the Airway Safety Expansion Act after this accident, and the act requires all civil air carrier to equip Traffic Alert and Collision Avoidance Systems (TCAS). Although no air carrier aircraft have involved in mid-air collisions after TCAS was introduced, the possibility of collision still exists. All pilots need to be alert to the potential for mid-air collision. Regardless of whether the pilot is conducting a flight under instrument flight rule (IFR) …show more content…
This is a very small part of vision and is where the vision is most sharp. Although the normal vision of field is 135 degree vertically (60 degree up and 75 degree down), and 160 degree horizontally (per eye), fovea is the only part that can perceive and send a clear and sharp image to the brain. However, fovea can perceive information in only one degree of horizontal and vertical direction. Moreover, if the object is outside of foveal field, pilot can see only about one-tenth of what he or she can see within the foveal field. For example, a pilot can see an aircraft that is ten miles away from him or her by using the foveal field, however; if the pilot uses peripheral vision, the aircraft has to be one mile away for he or she to recognize the traffic. We can see a lot more than one degree, but the detail we absorb outside of foveal cone is …show more content…
Pilot should divide the sky into blocks, each of 10 to 15 degree of the horizon, and scan each block for couple seconds. Human eyes need one to two seconds to adjust and refocus when the sight picture is changed, so sweep of the eyes could blur the vision. The common block scan techniques are the "side-to-side" scan and "front-to-side" scan. Although the block scan is an effective way to avoid traffics, it has limitations. Most mid-air collisions occur when an aircraft tries to overtake another aircraft, yet the scanning area for block scan technique does not include the area behind the aircraft. Therefore, pilots should look behind the aircraft as well particularly during approach and