Overall condition of the problem. The main causes of accidents are the people, aviation technology and the environment.
The process of aircraft operation is directly related to the interaction of the sun with the external environment. Because of the impact on the whole spectrum of the sun of the environment should be to identify those meteorological phenomena, under whose influence may cause the AP. They are called dangerous meteorological phenomena (OMYA), which include a strong atmospheric turbulence, wind shear (SV), icing sun, thunderstorms, electric shocks, heavy rains, snow, fog and the presence in the atmosphere of foreign objects (birds, probes, etc.). .
Dangerous meteorological phenomena affect the flight of the sun differently. In particular, atmospheric turbulence, wind shear and wake alter the forces and moments acting on the aircraft and the cause of his perturbed motion. The consequence of a collision with a bird or a lightning strike may be local structural damage to aircraft or its units. Phenomena such as fog and low clouds hamper aircraft navigation landing and perform other related functions of the crew running the Sun than provoke it possible missteps.
According to the ICAO, the total number of AP related to weather conditions. 62% due to the deterioration of visibility, 11% - thunderstorms, 11% - strong turbulence, 7% - icing, 9% - other reasons. Among other reasons, one of the first places occupied by cases of collision of aircraft with birds. According to the US Federal Aviation Administration (FAA), for the period of 2006 2011 years. recorded 16 949 cases of collision of aircraft with birds.
In order to identify the real impact of the environment on PD performed a statistical analysis of the AP on the basis of materials ICAO, FAA, the National Transportation Safety Board US (NTSB), the inspection bulletin BP Ukraviatrans.
Results of the analysis depending on the weather conditions the AP show that a significant number of accidents and serious accidents occur during takeoff, approach and landing aircraft. The main danger is limited visibility, due to the low altitude clouds, fog, snow and sharp wind shear as well as icing Sun and its engines. When the flight time are the most likely AP related to exposure to the sun in a thunderstorm, accompanied by hail, large convective turbulence, heavy rain and lightning.
The analysis described in the literature of the AP, which took place in the turbulence at heights, shows that in most cases they are manifested during thunderstorms or in close proximity to them. If we exclude these cases, the pure severe turbulence in clear air (of CAT) - a relatively rare phenomenon. At the same time it is recognized as dangerous for aircraft mainly because of the surprise effect on the aircraft. Therefore, many of the OMYA affecting the safety of the sun, consider the nature of storm formations of CAT and wind shear zone, and then briefly describe the methods and means of detection and protection from the effects of the sun these dangerous natural phenomena.
Thunderstorms and electric discharges. FAA Technical Center has conducted a statistical analysis of 800 reports of lightning strikes in the Armed Forces. Using a computer database allowed to group them according to certain criteria.
Types of aircraft flight modes, which were reported by the flight crew and the weather conditions were compared as a percentage of the total number of lightning strikes. Among them - height
flight, temperature, month of the year in which there was a lightning strike, the type of precipitation, the degree of turbulence of the atmosphere, the electrical state before and after a lightning strike, flight mode. Calculated histogram representing the information about the frequency of lightning strikes in the sun, depending on the conditions.
The histogram characterizing the effect of the time of year on the distribution of lightning strikes in the sun, it is shown that the greatest number of cases occurs in the spring (March, April, May). This finding is contrary to the prevailing opinion earlier that most cases occur in the summer.
A significant number of strokes is typical for the winter months (December, January), when the conditions for thunderstorms do not occur as often. Some of lightning strikes occurred during the flight the sun through the snow, due to the strong electrification of the atmosphere in a snowstorm. One of the reasons of frequent collisions with lightning in the winter months can be something that is more difficult to avoid such situations, as the appearance of lightning during a snowstorm define more complex than during the summer thunderstorms. The crew is relatively easy to set up and avoid summer thunderstorms associated with the presence of cumulonimbus clouds containing heavy rains and rising to a great height. Winter snowstorms are often associated with rain layered clouds that spread over large areas and do not have strong rain nuclei, easily fixed meteorological radars.
Confirming the findings that most lightning occurs at temperatures close to the freezing point of water, ie. E. By up + 5 -5 ° C.
More than 85% of lightning strikes in the sun takes place in a temperature range of up to -6 + 20 ° C.
On the number of lightning strikes affect altitude. According to the data, 36% sun was struck at altitudes below 3000 m and 87% - at altitudes sun to 4900 m. The fact that most lightning occurs at altitudes sun to 4900 m, shows the rare occurrence of lightning on high altitudes. We know that the storm clouds may extend to a height of 20 000 m and lightning occur throughout their volume.
The distribution of lightning strikes, depending on the altitude also affects the distribution of the phase of flight. As can be seen from the histogram, the most lightning strikes in the sun falls during the climb (37%) and approach (21%).
The results of the analysis of the AP and special studies show that the actual probability of a lightning strike in the sun in the active thunderstorm clouds is 102, t. E. Lightning strikes in the sun on average once in a hundred flights a thundercloud.
Wind shear. For a detailed statistical analysis of the AP caused by CB were used materials investigations NTSB, which according to US airspace for 1985 2005 years. 185 occurred accident, which killed 257 people. The most dangerous phases of flight from the point of view of the impact of NE are descent, approach and landing aircraft.
A large number of AP to the descent and landing phases due to the low-speed aircraft flight at these stages and their transience.
At AP amount also affects the absolute wind speed conditions NE, and on the sun light is greater than the heavy. As can be seen from the figure, heavy sun falls 16 AP, the lungs - 169. In addition, the unfavorable winds for the AP - 5. 10 m / s.
According to the ICAO, SV at low altitudes is the reason 20% of cases normally functioning rolling out the sun over the edge of the runway and the runway more than 10% of landings up to the edge.
These examples illustrate the hazards CB and the relevance of safety in these conditions.
The icing of aircraft. The most serious incident due to icing of the sun was a disaster ATP-72 (31 1994 October, in the area of Rozelaun, Indiana, USA) with the death of 68 people. This disaster was the reason for a number of new papers. In one of them made a detailed analysis of 149 accidents, including accidents 65 the total number of victims 1095 people. (1946- 1996 years.), Caused by icing, according to the Flight Safety Foundation.
The largest number of victims (256 people.) Has been a disaster in the sun DC-8 on takeoff at the airport in Gander (Canada, 12 1985 of December). In the Russian Federation, the icing was the cause of the crash of the Yak-40 at Sheremetyevo Airport in March 9 2000 city
A high percentage of accidents (43,6%) says that the ice is very dangerous factor in accidents.
On the number of AP caused by icing, influence of the year, phase of flight, as well as the mass of the aircraft.
The highest number of such cases occur in December and January - at 23.5%, approximately 15% - in February and March. Incidents related to icing occurred in May, July and August in the flight route. The latest AP no casualties from the sun BAE (Iowa, United States, 26 May 1996 g) en-route in icing conditions denied all four of the engine and the sun performed an emergency landing on only one engine running.
An analysis of the circumstances of the AP identified phases of flight, which begins the signs of icing. For example, the incident occurred at the stage of the climb, but there was still ice on the ground before takeoff. In this case, step occurrence of the incident taken the initial climb, as the beginning stage of icing - ground stage. Of the ten most severe AP caused by icing, 5 disasters (50%) occurred in the conditions of the initial icing sun on earth.
Most of the AP due to icing in flight characteristic of the sun, the maximum take-off weight50 not exceeding m. Thus, icing aircraft in flight, significantly affects the characteristics naletnye relatively small sun. Top of the icing on the ground led to the AP with large sun takeoff weight (two catastrophes BC DC-8 160 with takeoff weight tonnes).
Initial icing sun on the earth - the reason for the AP in step run-up, and all stages of the climb, which is based on the human factor, ie. E. Errors in the actions of the pilot, not following regulations, as well as the low level of education.
Expert assessments of meteorological phenomena pilots. Statistical data on the impact of specific meteorological phenomena on safety is interesting to compare with peer review pilots. Such estimates are obtained after processing special survey flight crews. Regardless of the length of service and functions in the crew interviewed experts unanimously recognize severe weather lightning. In the second place they put the hail, the third - the turbulence. Turbulence is determined as the most frequent meteorological phenomenon.
According to the generalized opinion of experts, meteorological phenomena at different stages of the flight are ranked according to their degree of danger. It will be appreciated that this list of wind shear at takeoff and landing included in the concept of turbulence. During the climb, and in particular, en route lightning and hail pilots recognized the most dangerous - 65,4% respectively and 74,4%. On takeoff and landing assessment of dangerous weather phenomena are distributed relatively evenly across all of their sources.
It is also important to evaluate how often they occur, or other meteorological phenomena in the practice of piloting. The sequence of weather phenomena, obtained by averaging the seats assigned to them in the classification of pilots OMYA frequency of meetings with them, is as follows: turbulence, lightning, strong winds, icing, NE, heavy rain, lightning, hail. More than 80% of those surveyed pilots indicated that most often affect the flight turbulence, storm and strong wind.
In phases of flight, these phenomena can be represented in the following sequence:
takeoff - turbulence, hail, lightning, rain, wind, and other;
during the climb - hail, lightning, turbulence, rain, wind, and other;
route - the lightning, hail, turbulence, rain and other wind;
during descent - hail, lightning, turbulence, rain and other wind;
during landing - turbulence, rain, hail, lightning, wind and others.
Statistics show that listed OMYA greatest impact on safety have icing, wind disturbance, atmospheric electrical discharges.
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