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40 mid-air collisions averted in Pakistan in 2007
Monday, June 23, 2008
By Abdul Sattar Khan
LAHORE: The countrys airspace is increasingly becoming unsafe as the radar system currently being used to cover the Pakistan airspace brought almost 40 commercial flights on a collision course during 2007.
It was the sheer luck coupled with timely application of senses on the part of pilots and the air traffic controllers that on 20 occasions, these 40 flights were prevented from colliding in the skies, an event which in aviation jargon is known as an Air Miss.
Official spokesman for the Civil Aviation Authority (CAA), Pervez George, however, claimed that the airspace of the country was completely safe though the CAA was considering upgrading the existing system or totally replacing it with a new one.
We are considering the financial factor and cost-effectiveness of the proposal to determine how much each option would cost George maintained. But the spokesman conceded: The CAA will opt for a new system only if upgrading of the existing system is not workable for 15 years.
Confidential documents available on the issue revealed that on time performance and in-flight safety were suffering and the potential for a catastrophic accident will continue to persist since the number of Air Miss (near collisions) had increased from just three in 2006 to 20 in 2007.
The Air Navigation Services (ANS) have been asked to lower the Air Miss rate to a maximum three in 2008, sources said. In the CAA terminology, an Air Miss, Near Miss or Near Collision is an unplanned event that did not result in injury, illness, or damage but had the potential to do so. Only a lucky break in the chain of events prevents an injury, fatality or damage. Although, human error is common in any such event, a faulty system invariably permits or compounds the harm.
This is an alarming rise and needs a serious consideration, revealed a document pertaining to this issue. Many reports were prepared on the issue yet an inquiry report relating to one such air miss between a PIA Hajj flight from Jeddah to Peshawar and an Indian Airlines Airbus 320 going from Delhi to Dubai, brought on surface not only the causes of the Air Misses but exposed faults in the radar system of the country.
Both airliners had come as close as 3-4 miles (head-on), while flying on reciprocal tracks at the same altitude of 34,000 feet. Experts say the upgrading of the present radar system is no more a solution. Acquiring new radar system is the only option left since the upgrading of radar will be good only for three to four years.
Pakistan airspace is divided into two portions known as Flight Information Regions (FIR). Karachi FIR is divided into three sectors West, East and North, while Lahore is divided into two sectors East and West.
The integrated radar system, comprising various modes of radars, navigational and communication equipment, is installed at Karachi, Lahore and Islamabad while three more points, including Pasni, Lakhpas and Rohjan, are working as relay stations.
The Primary Surveillance Radar (PSR), which provides raw material with no identification marks as only the image appears on screen of which the coverage area is 98 NM (175 kms), and the Secondary Surveillance Radar (SSR), which displays all sorts of identification marks of the aircraft, which includes flight level, speed, predicted position and call signs along with the coverage area of 200 NM (380 kms), are the two most important modes.
Highlighting the severe safety hazards in the countrys airspace, reports identify a significant portion of the airspace between Zahidan and Qalat, (covering 231 NM), and Zahidan and Panjgur (covering 226 NM) is virtually blank as it does not fall in the line of sight of the remotely connected SSR transmitters and Extended VHF (Very High Frequency) radio transmitters at Pasni and Lakpass points.
Moreover, effective radar surveillance and VHF communication is not available at the northern part of Pakistan airspace due to line of sight problems. For instance, the traces of aircraft entering the Pakistani airspace from seven transferring points both between Afghanistan-Pakistan and China-Pakistan are mostly not available on the radars installed at Lahore FIR.
In such a situation, handing over and taking over the air traffic, particularly from Afghanistan, carries more risk. Moreover, this part of the airspace is also more difficult to be tackled as the Pakistan airspace using a system called Reduced Vertical Separation Minima (RVSM) is maintaining vertical separation of 1,000 feet between the opposite direction aircraft and 2,000 feet between the same direction aircraft.
The Afghanistan airspace is maintaining 2,000 feet between the opposite direction aircraft and 4,000 feet between the same direction aircraft.
During the first week of June, there were 513 east-bound flights, which entered the Pakistan airspace from Afghanistan, while there were 669 west-bound aircraft, which were transferred from Pakistan to Afghanistan.
The situation is also alarming at the four conflicting points (conversion and diversion). These points are D I Khan, Zhob, R Y Khan and Panjgur, where there is substantial international transit traffic converges.
Similarly Karachi Area Control West is the largest but perhaps the worst designed portion of the Pakistan airspace. The report suggested installation of satellite-based surveillance and communication systems such as Automatic Dependant Surveillance (ADS) and Controller Pilot Data Link Communication (CPDLC) to effectively solve surveillance and communication problems, not only in the northern part but also elsewhere in Pakistan.
Redesigning of airspace structure into upper and lower and restructuring of route structure to minimise the track congestion is proposed in one such report. Redesigning of the airspace into upper and lower would allow two air traffic controllers to handle the aircraft one for below 29,000 feet altitude while the second for above 29,000 feet flight level.
The performance of Extended VHF Communication System is of very low quality, with excessive background noise resulting in repeated radio calls to communicate, which increases stress and fatigue for pilots and controllers.
This problem has also been highlighted by the VVIP flight Pakistan-2. Lahore-Delhi (DSC) Direct Speech Circuit contact mostly remains unserviceable, leaving behind the only choice of High Frequency (HF) facility, which does not qualify for spontaneous coordination.
Such connection between Lahore-Delhi remained non-operative for 1850 hours during the first four months of the last year. Similarly, Lahore-Kabul International Standard Dialing (ISD) line is completely unserviceable for the past two years.
In Lahore sector, the display of primary tracks of aircraft is poor within 5 NM (9 kms) below 2,000 feet while all radar data and maps vanish whenever radar scope is kept in standby (bypass) mode for longer durations.
Frequent un-serviceability of radar antennas at Pasni, Lakpass and Rojhan, non-availability of weather information within 5 NM of Karachi PSR, non availability of PSR after 60 NM at Karachi, Lahore and Islamabad are very common. While most of the time, the Islamabad radar is working on single diversity channel.
The reports say safety features like 'Conflict Alert', and Colour Coding of the targets, features built in a modern radar surveillance system, are not available in the existing system. Even the main weapon against the rising risk of midair collision, called the TCAS (Traffic Collision Avoidance System), offers no guarantee against collisions although it may have averted many incidents.
In majority of the cases, TCAS, an on-board computer display, does not advise turning in any direction because it has no bearing information on the potentially conflicting traffic. Mid air collisions in India in 1997, in Germany in 2002 and in Brazil in 2006 could not be averted by the TCAS.
Monday, June 23, 2008
By Abdul Sattar Khan
LAHORE: The countrys airspace is increasingly becoming unsafe as the radar system currently being used to cover the Pakistan airspace brought almost 40 commercial flights on a collision course during 2007.
It was the sheer luck coupled with timely application of senses on the part of pilots and the air traffic controllers that on 20 occasions, these 40 flights were prevented from colliding in the skies, an event which in aviation jargon is known as an Air Miss.
Official spokesman for the Civil Aviation Authority (CAA), Pervez George, however, claimed that the airspace of the country was completely safe though the CAA was considering upgrading the existing system or totally replacing it with a new one.
We are considering the financial factor and cost-effectiveness of the proposal to determine how much each option would cost George maintained. But the spokesman conceded: The CAA will opt for a new system only if upgrading of the existing system is not workable for 15 years.
Confidential documents available on the issue revealed that on time performance and in-flight safety were suffering and the potential for a catastrophic accident will continue to persist since the number of Air Miss (near collisions) had increased from just three in 2006 to 20 in 2007.
The Air Navigation Services (ANS) have been asked to lower the Air Miss rate to a maximum three in 2008, sources said. In the CAA terminology, an Air Miss, Near Miss or Near Collision is an unplanned event that did not result in injury, illness, or damage but had the potential to do so. Only a lucky break in the chain of events prevents an injury, fatality or damage. Although, human error is common in any such event, a faulty system invariably permits or compounds the harm.
This is an alarming rise and needs a serious consideration, revealed a document pertaining to this issue. Many reports were prepared on the issue yet an inquiry report relating to one such air miss between a PIA Hajj flight from Jeddah to Peshawar and an Indian Airlines Airbus 320 going from Delhi to Dubai, brought on surface not only the causes of the Air Misses but exposed faults in the radar system of the country.
Both airliners had come as close as 3-4 miles (head-on), while flying on reciprocal tracks at the same altitude of 34,000 feet. Experts say the upgrading of the present radar system is no more a solution. Acquiring new radar system is the only option left since the upgrading of radar will be good only for three to four years.
Pakistan airspace is divided into two portions known as Flight Information Regions (FIR). Karachi FIR is divided into three sectors West, East and North, while Lahore is divided into two sectors East and West.
The integrated radar system, comprising various modes of radars, navigational and communication equipment, is installed at Karachi, Lahore and Islamabad while three more points, including Pasni, Lakhpas and Rohjan, are working as relay stations.
The Primary Surveillance Radar (PSR), which provides raw material with no identification marks as only the image appears on screen of which the coverage area is 98 NM (175 kms), and the Secondary Surveillance Radar (SSR), which displays all sorts of identification marks of the aircraft, which includes flight level, speed, predicted position and call signs along with the coverage area of 200 NM (380 kms), are the two most important modes.
Highlighting the severe safety hazards in the countrys airspace, reports identify a significant portion of the airspace between Zahidan and Qalat, (covering 231 NM), and Zahidan and Panjgur (covering 226 NM) is virtually blank as it does not fall in the line of sight of the remotely connected SSR transmitters and Extended VHF (Very High Frequency) radio transmitters at Pasni and Lakpass points.
Moreover, effective radar surveillance and VHF communication is not available at the northern part of Pakistan airspace due to line of sight problems. For instance, the traces of aircraft entering the Pakistani airspace from seven transferring points both between Afghanistan-Pakistan and China-Pakistan are mostly not available on the radars installed at Lahore FIR.
In such a situation, handing over and taking over the air traffic, particularly from Afghanistan, carries more risk. Moreover, this part of the airspace is also more difficult to be tackled as the Pakistan airspace using a system called Reduced Vertical Separation Minima (RVSM) is maintaining vertical separation of 1,000 feet between the opposite direction aircraft and 2,000 feet between the same direction aircraft.
The Afghanistan airspace is maintaining 2,000 feet between the opposite direction aircraft and 4,000 feet between the same direction aircraft.
During the first week of June, there were 513 east-bound flights, which entered the Pakistan airspace from Afghanistan, while there were 669 west-bound aircraft, which were transferred from Pakistan to Afghanistan.
The situation is also alarming at the four conflicting points (conversion and diversion). These points are D I Khan, Zhob, R Y Khan and Panjgur, where there is substantial international transit traffic converges.
Similarly Karachi Area Control West is the largest but perhaps the worst designed portion of the Pakistan airspace. The report suggested installation of satellite-based surveillance and communication systems such as Automatic Dependant Surveillance (ADS) and Controller Pilot Data Link Communication (CPDLC) to effectively solve surveillance and communication problems, not only in the northern part but also elsewhere in Pakistan.
Redesigning of airspace structure into upper and lower and restructuring of route structure to minimise the track congestion is proposed in one such report. Redesigning of the airspace into upper and lower would allow two air traffic controllers to handle the aircraft one for below 29,000 feet altitude while the second for above 29,000 feet flight level.
The performance of Extended VHF Communication System is of very low quality, with excessive background noise resulting in repeated radio calls to communicate, which increases stress and fatigue for pilots and controllers.
This problem has also been highlighted by the VVIP flight Pakistan-2. Lahore-Delhi (DSC) Direct Speech Circuit contact mostly remains unserviceable, leaving behind the only choice of High Frequency (HF) facility, which does not qualify for spontaneous coordination.
Such connection between Lahore-Delhi remained non-operative for 1850 hours during the first four months of the last year. Similarly, Lahore-Kabul International Standard Dialing (ISD) line is completely unserviceable for the past two years.
In Lahore sector, the display of primary tracks of aircraft is poor within 5 NM (9 kms) below 2,000 feet while all radar data and maps vanish whenever radar scope is kept in standby (bypass) mode for longer durations.
Frequent un-serviceability of radar antennas at Pasni, Lakpass and Rojhan, non-availability of weather information within 5 NM of Karachi PSR, non availability of PSR after 60 NM at Karachi, Lahore and Islamabad are very common. While most of the time, the Islamabad radar is working on single diversity channel.
The reports say safety features like 'Conflict Alert', and Colour Coding of the targets, features built in a modern radar surveillance system, are not available in the existing system. Even the main weapon against the rising risk of midair collision, called the TCAS (Traffic Collision Avoidance System), offers no guarantee against collisions although it may have averted many incidents.
In majority of the cases, TCAS, an on-board computer display, does not advise turning in any direction because it has no bearing information on the potentially conflicting traffic. Mid air collisions in India in 1997, in Germany in 2002 and in Brazil in 2006 could not be averted by the TCAS.
