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Wake vortices are a natural by-product of lift generated by aircraft. An aircraft exposed to the wake vortex circulation of another aircraft can experience an aerodynamic upset which it may or may not be able to easily correct with its control authority, especially when the aircraft is adjacent to the ground. For this reason, numerous Air Traffic Control (ATC) separation standards include consideration of wake vortex behaviour, defining the separation at which operations can be conducted without a concern for a wake vortex hazard. These separation standards have served us well. There has never been a fatal accident in the U.S. due to wake vortex when instrument flight rules (IFR) separations are being provided. Wake vortex behaviour is strongly dependent on ambient weather conditions. In certain conditions, such as calm winds without turbulence, they linger and last longer. Separation standards and ATC procedures have been designed for the worst conditions with respect to wake behaviour. For this very reason, however, it has long been believed that there may be room for enhancing ATC procedures if wake vortex behaviour were known more precisely. Over the years, there have been several efforts in the U.S. and abroad to develop technologies that provide improved knowledge of wake behaviour based on environmental conditions, and to implement ATC procedures utilizing this improved knowledge. Some of these efforts are beginning to produce successful results. The U.S. has deployed a procedure called Simultaneous Offset Instrument Approaches (SOIA). Depending upon the runway geometry, the SOIA procedure can require specific wake vortex related features. SOIA is in the implementation phase at San Francisco (SFO and St. Louis (STL). Several other procedures have been considered over time and some are incorporated in the FAA/NASA Wake Turbulence Research Management Plan (RMP). The RMP has been developed jointly by the FAA and NASA to direct current and future efforts. Numerous wake vortex research and implementation efforts are underway in Europe. The German ATC provider Deutsche Flugsicherung (DFS) has developed the High Approach and Landing System (HALS), which has been tested at Frankfurt, Germany, since June 2001. DFS is also developing a Wake Vortex Warning System (WVWS), which appears to have a good outlook for implementation. The current research and development efforts in the U.S. and Europe are being coordinated through the FAA/Eurocontrol Cooperative R&D Action Plan 14.1. An aircraft exposed to the wake vortex circulation of another aircraft can experience an aerodynamic upset, which it may or may not be able to easily correct, especially when the aircraft is （ ）.
The decision to provide a stopway and/or a clearwayas an alternative to an increased length of runway will depend on the physical characteristics of the area beyond the runway end, and on the operating performance requirements of the prospective aeroplanes. The runway, stopway and clearway lengths to be provided are determined by the aeroplane takeoff performance, but a check should also be made of the landing distance required by the aeroplanes using the runway to ensure that adequate runway length is provided for landing. The length of a clearway, however, cannot exceed half the length of take-off run available. The aeroplane performance operating limitations require a length which is enough to ensure that the aeroplane can, after starting a take-off, either be brought safely to a stop or complete the take-off safely. Let’s suppose the runway, stopway and clearway lengths provided at the aerodrome are only just adequate for the aeroplane requiring the longest take-off and accelerate-stop distances, taking into account its take-off mass, runway characteristics and ambient atmospheric conditions. Under these circumstances there is, for each take-off, a speed, called the decision speed; below this speed, the take-off must be abandoned if an engine fails, while above it the take-off must be completed. A very long take-off run and take-off distance would be required to complete a take-off when an engine fails before the decision speed is reached, because of the insufficient speed and the reduced power available. There would be no difficulty in stopping in the remaining accelerate-stop distance available if action is taken immediately. In these circumstances, the correct course of action would be to abandon the take-off. On the other hand, if an engine fails after the decision speed is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available. However, because of the high speed, there would be difficulty in stopping the aeroplane in the remaining accelerate-stop distance available. The decision speed is not a fixed speed for any aeroplane, but can be selected by the pilot within limits to suit the accelerate-stop and take-off distance available, aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions at the aerodrome. Normally, a higher decision speed is selected as the accelerate-stop distance available increases. A variety of combinations of accelerate-stop distances required and take-off distances required can be obtained to accommodate a particular aeroplane, taking into account the aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions. Each combination requires its particular length of take-off run.5. decision speed, the take-off must be abandoned if an engine fails.
The decision to provide a stopway and/or a clearwayas an alternative to an increased length of runway will depend on the physical characteristics of the area beyond the runway end, and on the operating performance requirements of the prospective aeroplanes. The runway, stopway and clearway lengths to be provided are determined by the aeroplane takeoff performance, but a check should also be made of the landing distance required by the aeroplanes using the runway to ensure that adequate runway length is provided for landing. The length of a clearway, however, cannot exceed half the length of take-off run available. The aeroplane performance operating limitations require a length which is enough to ensure that the aeroplane can, after starting a take-off, either be brought safely to a stop or complete the take-off safely. Let’s suppose the runway, stopway and clearway lengths provided at the aerodrome are only just adequate for the aeroplane requiring the longest take-off and accelerate-stop distances, taking into account its take-off mass, runway characteristics and ambient atmospheric conditions. Under these circumstances there is, for each take-off, a speed, called the decision speed; below this speed, the take-off must be abandoned if an engine fails, while above it the take-off must be completed. A very long take-off run and take-off distance would be required to complete a take-off when an engine fails before the decision speed is reached, because of the insufficient speed and the reduced power available. There would be no difficulty in stopping in the remaining accelerate-stop distance available if action is taken immediately. In these circumstances, the correct course of action would be to abandon the take-off. On the other hand, if an engine fails after the decision speed is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available. However, because of the high speed, there would be difficulty in stopping the aeroplane in the remaining accelerate-stop distance available. The decision speed is not a fixed speed for any aeroplane, but can be selected by the pilot within limits to suit the accelerate-stop and take-off distance available, aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions at the aerodrome. Normally, a higher decision speed is selected as the accelerate-stop distance available increases. A variety of combinations of accelerate-stop distances required and take-off distances required can be obtained to accommodate a particular aeroplane, taking into account the aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions. Each combination requires its particular length of take-off run.4. What can we learn from Para. 4?
The decision to provide a stopway and/or a clearwayas an alternative to an increased length of runway will depend on the physical characteristics of the area beyond the runway end, and on the operating performance requirements of the prospective aeroplanes. The runway, stopway and clearway lengths to be provided are determined by the aeroplane takeoff performance, but a check should also be made of the landing distance required by the aeroplanes using the runway to ensure that adequate runway length is provided for landing. The length of a clearway, however, cannot exceed half the length of take-off run available. The aeroplane performance operating limitations require a length which is enough to ensure that the aeroplane can, after starting a take-off, either be brought safely to a stop or complete the take-off safely. Let’s suppose the runway, stopway and clearway lengths provided at the aerodrome are only just adequate for the aeroplane requiring the longest take-off and accelerate-stop distances, taking into account its take-off mass, runway characteristics and ambient atmospheric conditions. Under these circumstances there is, for each take-off, a speed, called the decision speed; below this speed, the take-off must be abandoned if an engine fails, while above it the take-off must be completed. A very long take-off run and take-off distance would be required to complete a take-off when an engine fails before the decision speed is reached, because of the insufficient speed and the reduced power available. There would be no difficulty in stopping in the remaining accelerate-stop distance available if action is taken immediately. In these circumstances, the correct course of action would be to abandon the take-off. On the other hand, if an engine fails after the decision speed is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available. However, because of the high speed, there would be difficulty in stopping the aeroplane in the remaining accelerate-stop distance available. The decision speed is not a fixed speed for any aeroplane, but can be selected by the pilot within limits to suit the accelerate-stop and take-off distance available, aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions at the aerodrome. Normally, a higher decision speed is selected as the accelerate-stop distance available increases. A variety of combinations of accelerate-stop distances required and take-off distances required can be obtained to accommodate a particular aeroplane, taking into account the aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions. Each combination requires its particular length of take-off run.3. If an engine fails after the is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available.
The decision to provide a stopway and/or a clearwayas an alternative to an increased length of runway will depend on the physical characteristics of the area beyond the runway end, and on the operating performance requirements of the prospective aeroplanes. The runway, stopway and clearway lengths to be provided are determined by the aeroplane takeoff performance, but a check should also be made of the landing distance required by the aeroplanes using the runway to ensure that adequate runway length is provided for landing. The length of a clearway, however, cannot exceed half the length of take-off run available. The aeroplane performance operating limitations require a length which is enough to ensure that the aeroplane can, after starting a take-off, either be brought safely to a stop or complete the take-off safely. Let’s suppose the runway, stopway and clearway lengths provided at the aerodrome are only just adequate for the aeroplane requiring the longest take-off and accelerate-stop distances, taking into account its take-off mass, runway characteristics and ambient atmospheric conditions. Under these circumstances there is, for each take-off, a speed, called the decision speed; below this speed, the take-off must be abandoned if an engine fails, while above it the take-off must be completed. A very long take-off run and take-off distance would be required to complete a take-off when an engine fails before the decision speed is reached, because of the insufficient speed and the reduced power available. There would be no difficulty in stopping in the remaining accelerate-stop distance available if action is taken immediately. In these circumstances, the correct course of action would be to abandon the take-off. On the other hand, if an engine fails after the decision speed is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available. However, because of the high speed, there would be difficulty in stopping the aeroplane in the remaining accelerate-stop distance available. The decision speed is not a fixed speed for any aeroplane, but can be selected by the pilot within limits to suit the accelerate-stop and take-off distance available, aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions at the aerodrome. Normally, a higher decision speed is selected as the accelerate-stop distance available increases. A variety of combinations of accelerate-stop distances required and take-off distances required can be obtained to accommodate a particular aeroplane, taking into account the aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions. Each combination requires its particular length of take-off run.2. Which of the following statements is true?
The decision to provide a stopway and/or a clearwayas an alternative to an increased length of runway will depend on the physical characteristics of the area beyond the runway end, and on the operating performance requirements of the prospective aeroplanes. The runway, stopway and clearway lengths to be provided are determined by the aeroplane takeoff performance, but a check should also be made of the landing distance required by the aeroplanes using the runway to ensure that adequate runway length is provided for landing. The length of a clearway, however, cannot exceed half the length of take-off run available. The aeroplane performance operating limitations require a length which is enough to ensure that the aeroplane can, after starting a take-off, either be brought safely to a stop or complete the take-off safely. Let’s suppose the runway, stopway and clearway lengths provided at the aerodrome are only just adequate for the aeroplane requiring the longest take-off and accelerate-stop distances, taking into account its take-off mass, runway characteristics and ambient atmospheric conditions. Under these circumstances there is, for each take-off, a speed, called the decision speed; below this speed, the take-off must be abandoned if an engine fails, while above it the take-off must be completed. A very long take-off run and take-off distance would be required to complete a take-off when an engine fails before the decision speed is reached, because of the insufficient speed and the reduced power available. There would be no difficulty in stopping in the remaining accelerate-stop distance available if action is taken immediately. In these circumstances, the correct course of action would be to abandon the take-off. On the other hand, if an engine fails after the decision speed is reached, the aeroplane will have sufficient speed and power available to complete the take-off safely in the remaining take-off distance available. However, because of the high speed, there would be difficulty in stopping the aeroplane in the remaining accelerate-stop distance available. The decision speed is not a fixed speed for any aeroplane, but can be selected by the pilot within limits to suit the accelerate-stop and take-off distance available, aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions at the aerodrome. Normally, a higher decision speed is selected as the accelerate-stop distance available increases. A variety of combinations of accelerate-stop distances required and take-off distances required can be obtained to accommodate a particular aeroplane, taking into account the aeroplane take-off mass, runway characteristics, and ambient atmospheric conditions. Each combination requires its particular length of take-off run.1. The aeroplane takeoff performance determines .
Most bird strikes on aerodromes involve a small range of species: primarily gulls (especially black-headed and common gulls), waders (mostly lap wing, but also golden plover and oystercatcher), pigeons, corvids, starling, skylark, swift, swallow and martins. There is a clear relation between bird mass and risk that the aircraft will be damaged: small birds (less than 100g) cause damage on less than 3% of occasions when they are struck; medium-sized birds (101g-1000g) -12%; and large birds (over 1000g) - nearly 23%. There is also a strong relation between bird numbers and the chances that the aircraft will be damaged: single birds cause damage on 8% of occasions; small flocks (2-10) - 14%; and larger flocks (11-100 birds) - 40%. Thus, species which are larger than 100g or occur on aerodromes in flocks are most likely to cause damage to aircraft. Gulls, waders, pigeons, corvids and starling all occur commonly on aerodromes, are responsible for the majority of bird strikes and are most likely to cause damage. However, they also respond well to habitat management and active dispersal techniques and are, therefore, controllable. These birds can be classed as the Priority Group for control. Many other species, most of which are less susceptible to available control measures, are involved in aerodrome bird strikes. Total numbers of bird strikes are not very useful in assessing an aerodrome＇s bird hazard or performance in controlling it. However, a more detailed breakdown can provide useful insights, as follows: ? Priority group species. If a high proportion of an aerodrome＇s bird strikes involve priority group species, then the hazard level is probably high and control standard low. ? Multiple strikes. If there are multiple strikes with priority group species, it is an indication that flocks are permitted to build up and remain on or close to runways. Bird strikes, especially multiple strikes, with these species commonly cause damage and, even if the reporting standard is low, these incidents cannot be suppressed. Thus, the hazard is obviously high and there are problems with controlling it. ? Small birds. All aerodromes have many small birds which are inevitably involved in strikes: Skylarks all year but especially in autumn; finches in winter; and swifts, swallows and martins in summer. If the common small birds are absent from an aerodrome＇s strike statistics, it can be assumed that the true situation is not reflected: the reporting standard must be suspect. ? Less common medium-sized and large species. The significance of the occurrence of these species in an aerodrome＇s strike records can only be properly interpreted with a detailed knowledge of local conditions. By adopting priorities of minimizing strikes with: (1) the greatest potential for serious accidents (multiple strikes with large birds); (2) priority group species; and (3) controllable species, and by using the prevalence of strikes with small birds as a check of reporting standard, the data can provide indicators of hazard level and performance which are independent of comparison with other aerodromes.5. Which of the following statements is true?
Most bird strikes on aerodromes involve a small range of species: primarily gulls (especially black-headed and common gulls), waders (mostly lap wing, but also golden plover and oystercatcher), pigeons, corvids, starling, skylark, swift, swallow and martins. There is a clear relation between bird mass and risk that the aircraft will be damaged: small birds (less than 100g) cause damage on less than 3% of occasions when they are struck; medium-sized birds (101g-1000g) -12%; and large birds (over 1000g) - nearly 23%. There is also a strong relation between bird numbers and the chances that the aircraft will be damaged: single birds cause damage on 8% of occasions; small flocks (2-10) - 14%; and larger flocks (11-100 birds) - 40%. Thus, species which are larger than 100g or occur on aerodromes in flocks are most likely to cause damage to aircraft. Gulls, waders, pigeons, corvids and starling all occur commonly on aerodromes, are responsible for the majority of bird strikes and are most likely to cause damage. However, they also respond well to habitat management and active dispersal techniques and are, therefore, controllable. These birds can be classed as the Priority Group for control. Many other species, most of which are less susceptible to available control measures, are involved in aerodrome bird strikes. Total numbers of bird strikes are not very useful in assessing an aerodrome＇s bird hazard or performance in controlling it. However, a more detailed breakdown can provide useful insights, as follows: ? Priority group species. If a high proportion of an aerodrome＇s bird strikes involve priority group species, then the hazard level is probably high and control standard low. ? Multiple strikes. If there are multiple strikes with priority group species, it is an indication that flocks are permitted to build up and remain on or close to runways. Bird strikes, especially multiple strikes, with these species commonly cause damage and, even if the reporting standard is low, these incidents cannot be suppressed. Thus, the hazard is obviously high and there are problems with controlling it. ? Small birds. All aerodromes have many small birds which are inevitably involved in strikes: Skylarks all year but especially in autumn; finches in winter; and swifts, swallows and martins in summer. If the common small birds are absent from an aerodrome＇s strike statistics, it can be assumed that the true situation is not reflected: the reporting standard must be suspect. ? Less common medium-sized and large species. The significance of the occurrence of these species in an aerodrome＇s strike records can only be properly interpreted with a detailed knowledge of local conditions. By adopting priorities of minimizing strikes with: (1) the greatest potential for serious accidents (multiple strikes with large birds); (2) priority group species; and (3) controllable species, and by using the prevalence of strikes with small birds as a check of reporting standard, the data can provide indicators of hazard level and performance which are independent of comparison with other aerodromes.4. Which of the following is the best title for the text?
Most bird strikes on aerodromes involve a small range of species: primarily gulls (especially black-headed and common gulls), waders (mostly lap wing, but also golden plover and oystercatcher), pigeons, corvids, starling, skylark, swift, swallow and martins. There is a clear relation between bird mass and risk that the aircraft will be damaged: small birds (less than 100g) cause damage on less than 3% of occasions when they are struck; medium-sized birds (101g-1000g) -12%; and large birds (over 1000g) - nearly 23%. There is also a strong relation between bird numbers and the chances that the aircraft will be damaged: single birds cause damage on 8% of occasions; small flocks (2-10) - 14%; and larger flocks (11-100 birds) - 40%. Thus, species which are larger than 100g or occur on aerodromes in flocks are most likely to cause damage to aircraft. Gulls, waders, pigeons, corvids and starling all occur commonly on aerodromes, are responsible for the majority of bird strikes and are most likely to cause damage. However, they also respond well to habitat management and active dispersal techniques and are, therefore, controllable. These birds can be classed as the Priority Group for control. Many other species, most of which are less susceptible to available control measures, are involved in aerodrome bird strikes. Total numbers of bird strikes are not very useful in assessing an aerodrome＇s bird hazard or performance in controlling it. However, a more detailed breakdown can provide useful insights, as follows: ? Priority group species. If a high proportion of an aerodrome＇s bird strikes involve priority group species, then the hazard level is probably high and control standard low. ? Multiple strikes. If there are multiple strikes with priority group species, it is an indication that flocks are permitted to build up and remain on or close to runways. Bird strikes, especially multiple strikes, with these species commonly cause damage and, even if the reporting standard is low, these incidents cannot be suppressed. Thus, the hazard is obviously high and there are problems with controlling it. ? Small birds. All aerodromes have many small birds which are inevitably involved in strikes: Skylarks all year but especially in autumn; finches in winter; and swifts, swallows and martins in summer. If the common small birds are absent from an aerodrome＇s strike statistics, it can be assumed that the true situation is not reflected: the reporting standard must be suspect. ? Less common medium-sized and large species. The significance of the occurrence of these species in an aerodrome＇s strike records can only be properly interpreted with a detailed knowledge of local conditions. By adopting priorities of minimizing strikes with: (1) the greatest potential for serious accidents (multiple strikes with large birds); (2) priority group species; and (3) controllable species, and by using the prevalence of strikes with small birds as a check of reporting standard, the data can provide indicators of hazard level and performance which are independent of comparison with other aerodromes.3. It can be inferred from the passage that （ ）.
Most bird strikes on aerodromes involve a small range of species: primarily gulls (especially black-headed and common gulls), waders (mostly lap wing, but also golden plover and oystercatcher), pigeons, corvids, starling, skylark, swift, swallow and martins. There is a clear relation between bird mass and risk that the aircraft will be damaged: small birds (less than 100g) cause damage on less than 3% of occasions when they are struck; medium-sized birds (101g-1000g) -12%; and large birds (over 1000g) - nearly 23%. There is also a strong relation between bird numbers and the chances that the aircraft will be damaged: single birds cause damage on 8% of occasions; small flocks (2-10) - 14%; and larger flocks (11-100 birds) - 40%. Thus, species which are larger than 100g or occur on aerodromes in flocks are most likely to cause damage to aircraft. Gulls, waders, pigeons, corvids and starling all occur commonly on aerodromes, are responsible for the majority of bird strikes and are most likely to cause damage. However, they also respond well to habitat management and active dispersal techniques and are, therefore, controllable. These birds can be classed as the Priority Group for control. Many other species, most of which are less susceptible to available control measures, are involved in aerodrome bird strikes. Total numbers of bird strikes are not very useful in assessing an aerodrome＇s bird hazard or performance in controlling it. However, a more detailed breakdown can provide useful insights, as follows: ? Priority group species. If a high proportion of an aerodrome＇s bird strikes involve priority group species, then the hazard level is probably high and control standard low. ? Multiple strikes. If there are multiple strikes with priority group species, it is an indication that flocks are permitted to build up and remain on or close to runways. Bird strikes, especially multiple strikes, with these species commonly cause damage and, even if the reporting standard is low, these incidents cannot be suppressed. Thus, the hazard is obviously high and there are problems with controlling it. ? Small birds. All aerodromes have many small birds which are inevitably involved in strikes: Skylarks all year but especially in autumn; finches in winter; and swifts, swallows and martins in summer. If the common small birds are absent from an aerodrome＇s strike statistics, it can be assumed that the true situation is not reflected: the reporting standard must be suspect. ? Less common medium-sized and large species. The significance of the occurrence of these species in an aerodrome＇s strike records can only be properly interpreted with a detailed knowledge of local conditions. By adopting priorities of minimizing strikes with: (1) the greatest potential for serious accidents (multiple strikes with large birds); (2) priority group species; and (3) controllable species, and by using the prevalence of strikes with small birds as a check of reporting standard, the data can provide indicators of hazard level and performance which are independent of comparison with other aerodromes.2. What can we learn from Para. 1?
