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AIR SAFETY Pull UP, Terrain Ground Proximity Warning System could be the answer to the risks of CFIT related air accidents in Nepal By KESHAB POUDEL New Delhi bound cargo plane of Lufthansa collided with the high hill behind Chandragiri last year killing all crew members. A skyline twinotter collided at the hill of Makwanpur on its way to Kathmandu from Simara last year. Necon Air's Avro aircraft crashed at Ramkot village hitting the tower of Nepal Telecommunication Corporation (NTC) and RNAC's twinotter last month crashed in Dadeldhura after bumping into hill. Not only these three aircraft, almost all air accidents in Nepal including the crash of Thai Airways and PIA in 1992 was due to the failure in detecting the terrain in front at times of poor visibility. After about a dozen of air crashes due to Controlled Flight Into Terrain (CFIT) failure, the civil aviation authorities in Nepal at last seem to have realized their weakness. The recent experiments have shown that the installation of Terrain Awareness Warning System (TAWS) and Ground Proximity Warning System (GPWS) can significantly reduce the CFIT-related accidents.
Moreover, Civil Aviation Authority of Nepal (CAAN) has already asked the airline operators to install Flight Data Recorder (FDR) in their aircraft. As per the notice of International Civil Aviation Organization (ICAO), CAAN is also considering to make it mandatory for airlines to install TAWS or GPWS. CFIT working group formed by ICAO to find ways to reduce the accident rate recommended the installation of TAWS or GPWS. If the ICAO amends its clauses related to flight operation requirements, aircraft will not be permitted to fly without using TAWS or GPWS. The CAAN is also organizing seminar on November 9 and 10 to discuss the benefits concerning the installation of GPWS/TAWS. At present, Nepal has altogether 16 air operators currently flying domestic and international flights including helicopters. As Nepal's almost all domestic aircraft which operate in airports surrounded by high terrain are not equipped with such systems, air operations in these areas are always challenging. Nepal is a country filled with high terrain and is, therefore, vulnerable to accidents particularly in monsoon season when they have to fly in poor visibility condition based on Instrument Metrological Condition (IMC). As such, installation of GPWS can greatly benefit the pilot. As Honeywall - an American company manufacturing the EGPWS - has already manufactured EGPWS variants for light general aviation aircraft, Nepalese air operators need to install it. In most of the countries, it is mandatory to install GPWS to reduce accidents. With the introduction of new system, pilots can even fly aircraft to high altitude airports like Jomsom and Manang easily. The aircraft manufactured before 1970s did not have TAWS, Navigation Satellite Systems, Global Navigation Satellite System (GNSS), or Aircraft Collision Avoidance Systems (ACAS) but they do have it now. Although installation of such systems will increase the initial operation cost, it would go a long way in ensuring the air safety. "There must not be any lapses on issues of passenger safety. The government and airline operators must take the initiatives to install the system in the context of Nepal where the rate of CFIT accident is so high," said an aviation expert. "Along with the installation of TAWS or GPWS, CAAN could also help the operators to get the required Supplementary Type Certificate (STC) from the manufacturer and permit the airlines to install the equipment." The various investigations, too, have shown that the CFIT accidents in Nepal can be reduced by enforcing operators to install Enhanced Ground Proximity Warning System (EGPWS) or Terrain Avoiding Systems formerly known as GPWS. EGPWS makes the pilots much more terrain-aware and the likelihood of getting too close to the ground unintentionally is massively reduced.
"In a modern TAWS-equipped cockpit, the pilots are provided, on their navigation display, with color-coded terrain contours when the aircraft is 2,500 ft or less above the ground. The color coding changes according to the terrain's height relative to the level that the aircraft is at - whether it is above, at the same height, or below. In a "classic" cockpit, EGPWS would have its own display which can be integrated with the weather radar display, although the modes have to be selected one at a time," writes Flight International in its 18-24 July, 2000 issue. As Nepal's airline operators have to fly in difficult terrain, the installation of system like EGPWS can prevent almost all kinds of accidents with just a small amount of extra investment. A number of investigation committees were formed following the accidents in the country. But rarely did the accident investigation teams followed a systematic approach to deal with the problem. "The investigation must be based on systems going into the depth of inquiry finding actual cause and to avoid future accidents by suggesting corrective action," said an expert. Establishing airline safety management program, gathering and analyzing sufficient safety information received from mandatory reports, voluntary reports, inspection and audit reports and information on past accident from flight data records are also necessary to ensure the flight safety. Although the CAAN had declared the Year 2000 as a Zero Air Accident Air, an RNAC's twinotter aircraft crashed at Dadeldhura killing all the passengers aboard. Because of the findings of experts that CFIT is the leading cause of air accident worldwide, ICAO is considering to amend its annex 6 to make it mandatory for every aircraft to install TAWS formerly known as GPWS. This system warns the pilot by saying "Terrain, Pull Up, Pull Up" in case the plane is dangerously close to ground. "No person may operate a turbine-powered airplane unless that airplane is equipped with an approved terrain awareness and warning system that meets the requirements for class A equipment in Technical Standard," states the recommendations on TAWS for Nepal. According to the recommendations, the airplane must also have an approved terrain situational awareness display. "We are asking aircraft operators to equip their planes with modern equipment and trained manpower to reduce the risk," said Rajesh Raj Dali, General Manager of Tribhuwan International Airport (TIA). The CFIT accident continues to increase worldwide. According to the survey, in 1970s it increased by 3.6 percent per year, by 4.8 percent in 1980s and 6.4 percent in 1990s. Nepal witnessed some worst aircraft accidents in the last one decade. Interestingly, all air crashes were similar in nature and types. After the accident of RNA's twin otter aircraft at Dadeldhura, there has been a renewal in the focus on the air safety. But unless the government takes some bold decisions and enforces the modern systems, the Nepalese sky may have to bear more such accidents. |
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