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EFFECTS OF VISIBILITY ON AIRCRAFT MISHAPS IN NIGERIA
Efe, S. I.
Geography and Regional Planning Department
Delta State University, Abraka.
This paper is an assessment of the effects of weather on aircraft mishaps in Nigeria. This was investigated with the aid of data collected from the Meteorological Service Office, Oshodi and the use of questionnaire. The data were analyzed with the aid of mean and multiple regression models. Results suggest that poor visibility (less than l000m) have a significant effect on aircraft mishaps in Nigeria, other casual factors of aircraft. Old age of the aircraft, lack of safe landing equipment amongst others factors of aircraft mishaps.
There have been several cases of air transportation problems due to poor aviation weather at both international and national airports worldwide. For example, in U.S.A. the weather is responsible for about 33 percent of all aviation accidents while thunderstorms are the commonest cause of flight delays (26 percent). Also, unfavourable winds and wind shear are responsible for 19 percent of flight hold-ups (Hayward and Oguntoyinbo, 1987). But Critchfield (1966) and Smith (1975) have noted the effects of poor visibility on flight operation. For instance. Smith (1975) opined that despite the increasing sophistication of automatic landing equipment, poor visibility from fog and low cloud ceilings is probably the major impediment to air operation throughout the world. In Nigeria, there has been a series of aviation accidents related to poor weather. But the worst aviation fatality occurred in November 1973, when 183 people died in an air crash at Kano airport during the landing approaches of a pilgrim flight from Jeddah as a thick dust haze persisted. Also Nigeria airways, suspended its flights for one week in January 1983, due to widespread dust haze, and was reported to have lost about 15 million U.S. dollars as a result (Adefolalu, 1984). Studies in this area have been neglected over the years, rather there are concentrations of studies on Harmattan dust haze as seen in the works of Biglestone (1958), Burns (1961), Ireland (1962), Samray (1974), Adefolalu (1968 and 1984); and Dear and Bokop (1996). Even the study by Adefolalu (1984) which appeared more recent in Nigeria only focused on the Bioclimatological aspect of Harmattan dust haze in Nigeria to the neglects of the effects of visibility on flight operations in Nigeria,. In fact, while vagaries of poor visibility on flight operation in Nigeria continued unabated, as highlighted in the Nigerian Guardian November 1996, December 1998 and the Comet February 2000. There are a dwindling number of studies in this area. The reason is not unconnected with the paucity of visibility data as well as inadequate records of flight accidents, delays and cancellations in most Nigerian airports and Meteorological services departments. Even when available, exorbitant fees for their purchase scare researchers away. Thus, there is dearth of information in this aspect of climatology. This study is therefore carried out in Nigeria that is located at the intersection of latitude 4°N and 14°N, and between longitude 3°E and 15°E. It is characterised with wet and dry season. However, in the coastal belt of Nigeria, wet season spans for 11 — 12 months.
OBJECTIVES OF THE STUDY
This study is aim at assessing the effects of visibility on aircraft mishaps and identifying other factors that causes aircraft mishaps in Nigeria and recommend ways of reducing aircraft mishaps in Nigeria.
CONCEPT AND METHODOLOGY
The study is based on the concept of visibility. Visibility is the highest distance an individual can see with an unaided Hayward and (Oguntoynibo, 1987). However, in the context of the aircraft operation, it is the highest distant a pilot can see on board (airborne) when taking off with the aid of an unaided eye. Visibility is said to be poor to aircraft operation, when it 100 metres and below (Efe, 1997). There are probably two main source areas for dust harmattan haze that precipitated in poor visibility in West Africa and Nigeria in particular. One is the plains between Bilma and Fays Largeau in Niger and Chad, where fine dust particles are fed to the area by seasonal streams from the Tibesti upland replenishing the dust that is stripped from the surface by the winds. The second originates west of the Ahaggar massif, Tonezrouft in Algeria. From the ‘former’ source is derived the haze that may extend across Nigeria (Hayward and Oguntoyinbo, 1987). It reaches the Nigerian border about 24 hours after leaving the Fays Largeau source Region (Burns, 1961).
Reduction of horizontal visibility invariably marks the onset of a spell, which lasts up to 3 — 5 days (Adebayo, 1980). But some spells may persist for up to 10 days, when the adduction of dust is from a “line” rather than a “point” source. In such a situation, clearance of the haze may be delayed to an extent that the arrival of another dust spell is not obvious. Persistence of dust haze for more than two weeks may be classified as due to only one spell whereas it could have been due to overlapping spells. This pattern of occurrence is more conspicuous in the southern limits of the dust “front” which according to Adefolalu (1968), is a feature of Harmattan dust to the South of the Inter-Tropical Discontinuity (ITD). The in-flight observation on four trips between Kano and Lagos made by Adefolalu showed that the dust layer is shallower but thicker in the extreme north (where visibility is poorer) and coastal parts of Nigeria. But higher to the south of the surface ITD where dynamic instability associated with the monsoon trough (Adefolalu, 1983), at about the 900mb level leads to rising motion which help to distribute the dust within a deeper layers.
Over the greater part of Nigeria, however, especially north of the forest zone, the prevalence of mist, most noticeably in the dry season, cannot be explained with reference to atmospheric moisture. In fact, it is more accurate to refer to haze rather than mist, the former term being used to describe visibility impaired by presence of solid aerosols, not liquid. In West Africa, particularly during the pre-rains period, such aerosols may be contributed by bush fire (Crozat et al, 1978), but by far the greater proportion of atmospheric pollutants is dust from the north, associated with the harmattan. The influence of this dust-laden north — easterly airflow, reaches even the Guinea Coast in the period December to February.
The data used for this study were extracted from the archives of the Accident Unit of Murtala Mohammed Airport, Ikeja, Lagos, (1987 — 1998) and the use of questionnaire. For this data collection, 1000 metres visibility upper limit is used as visibility induce for aircraft operation, the reason being that visibility higher than 1000 metres though affect aircraft operation, but its effect will not bring the desired delays, cancellation and accidents of aircraft in Nigeria. In Nigeria, there are a total of 14 airports, out of which the Murtala Mohammed Airport Ikeja formed the Central collating centre of aircraft accidents, delay and cancellation. This gave the impetus for the choice of the Ikeja Airport. Other reasons for the choice of Ikeja airport, and the years 1987 — 1998 include reliability, consistency; continuity of records and long range of data. For each year, the total daily, monthly and annual aircraft accident as well as those accidents that are weather related was scrutinized. The seasonal occurrence of aircraft accidents was adopted by dividing the months of the year into Wet (April-September) and Dry (October — March) seasons.
A total of 14 questionnaires were administered to the 14 accident units of the 14 major airports in Nigeria. This was done to elicit information responses on the major causes of aircraft mishaps in Nigeria. One questionnaire each was therefore, posted to the 14 airports and same number was filled, returned and used for the study.
The multiple regression analysis is used to determine the effects of poor visibility on aircraft mishaps, while line graph was used to depict the seasonal pattern of aircraft accidents in Nigeria.
DISCUSSION OF RESULTS
The result of aircraft accidents from 1987 — 1998 are presented and discussed below.
From the table above, a total of 89 cases of aircraft accidents were reported, out of which 45 were weather related; and the total number of casualties were 498. During the period under investigation, the year 1988 recorded the highest rate of aircraft accidents of 14 cases, out of which 9 were caused by poor visibility. This was followed by 1992 (10 cases), 1990, 1991 and 1995 (9 cases each), 1998. (8 cases), 1989 (7 cases); and the lowest rates of accidents occurred in 1993 and 1977 (3 cases), poor visibility was the major causes of 2 cases in the year 1997. Over these years, poor visibility was known to be an inducement of these accidents as shown in the weather related column of table 1. In 1988, the 9 weather related cases of accident out of the 14 total cases reported. occurred during the dry season when the hamattan dust haze was said to be highest in the country. Fog, mist, rain, and strong winds are other weather factors that have contributed to the accident rates over the years. Most especially those that happened during the months of April — September, are as a result of foggy and misty weather that could sometimes reduce the visibility to 50m in the morning. For instance as a result of foggy and misty weather on June 26th and 11 July 1991; the Nigeria Airway “Airbus 310” and Ashaka Cement Cessna Citation 550” crash landed at Murtala Mohammed Airport Lagos, and Company Al — 1. Airport in Bauchi respectively. Causalities were said to be 4 and 261 respectively. This was the worst aviation mishap during the period of this study.
It was gathered that 5 airports (Sokoto, Kano, Kaduna, Bauc1ñ, and Lagos) have reported cases of visibility — related accidents. This gives 36% percent of the 14 Nigerian airports. Sokoto recorded the highest accident records of 28 cases, while Lagos with 8 cases, recorded the lowest accidents during the period of study.
Looking at the casualty trends, 1991 recorded the highest (267), this was followed by 1996 (168), 1995 (26), 1988 (14), 1993 (9) 1997 (7), 1998 (5), and 1989and 1992 (1 each) being the lowest. However, no casualty was recorded in 1990 and 1993 though there were reported cases of 9 and 3 aircraft accidents. The ADC B727 airline that crashed into the Ejinrim water on November 6, 1996, claiming the lives of 146 passengers and crew recorded the second worst casualties during this period. Experts say fears of blackmail or sanction; poverty and fear of being accused of trying to sabotage the airline and government are part of causes of such dare devil attempts that propel a pilot to fly an aircraft when he knows it is unsafe to do so.
Other factors that led to these high accidents rate include mechanical problems pilot errors, faulty landing facilities in our airports; absence of floodlights; and unreliable air control facilities. In fact the control system is so poor that sometimes pilot have to communicate (relate) to each other on weather (visibility and wind speed) situation instead of using the control tower.
The result of the correlation analysis model showed that there is a high relationship between poor visibility and aircraft accident reported during these period of study. This is evident from a calculated value of 0.85 (72%) and critical table value of 0.51 at 0.01 Confidence level. Hence one can now say that poor visibility did not only inhibit aircraft operation, but has resulted in most of the aircraft accidents recorded in Nigeria as shown from the 72% explanation of the correlation. While the rest 28% is accounted for by human errors; and unreliable air control facilities and Mechanical problems.
Figure 1 depicts the Seasonal Occurrence of aircraft accident from 1987 — 1998. While there were double maximum of aircraft accident occurrence (13) in the month of April and September there is no accident recorded in the month of May. The concentration of fog and mist in the lower surface during the morning hours, in July — September, at times reduces visibility to 50m in Bight of Guinea and Coastal areas (Hayward and Oguntoyinbo, 1987), Human errors form the explanation to the highest accident recorded in the season. However the concentrations of aircraft accidents are more in the dry season (October — March). This is evident in 9, 7, 6, 8, 9 and 5 recorded during this season. In fact while there is virtually no month during the dry season that has less than 5 cases of accidents, there is in the wet season (April — September). This is evident in 13, 0, 4, 6, 9, and 13, recorded during this season. The highest cases of 13 occurrences of aircraft accidents were in the month of September. It is attributed to poor visibility related to heavy rainfall.
Causes of Aircraft mishaps in Nigeria
Table 2 shows the number of responses to the major causes of aircraft mishaps in Nigeria. Out of the 14 respondents interviewed, all the respondents indicated that poor visibility is a regular cause of aircraft mishaps in Nigeria. This indicates 100% of the respondent. Thus, this is a conformation of the earlier result which show that poor visibility have a significant effects on aircraft accident in Nigeria other factors in decreasing order of responses areas. Lack of regular maintenance (12 respondents); old age of the aircraft (10 respondents); lack of safe landing equipment (9 respondents); human errors (6 respondents) improper reporting system (5 respondents) and fear of blackmail (4 respondents) this showed that all these factor are the major factors that causes aircraft’s mishaps.
The result of the multiple regression analysis shows that poor visibility induced 72% of aircraft mishaps in Nigeria. The effects of poor visibility on each of the 5 airports however show that the highest effect was at Sokoto airport with calculated r-value of 0.68, and thus representing 47%. Banchi Kano, Kanduna and Lagos airports, with r-values of 0.67. 0.49 and 0.48, followed this respectively. These shows that poor visibility has exerted 45%, 37%. 24% and 23% effects on the prevalence of aircraft mishaps at Banchi, Kano, Kaduna and Lagos airports respectively. However, summary of ANOVA from the multiple regression analysis shows that poor visibility has strong significant effects on aircraft mishaps in Nigeria during the period of study. This is evident from a calculated F value 4.98 that is greater than the critical table value of 4.39, with 5 under 6 degree of freedom at 0.05 significant level (see table 3).
CONCLUSION AND RECOMMENDATION
The study revealed that poor visibility has significant effect on aircraft mishaps in Nigeria over the period of study. Apart from poor visibility, other causal factors of aircraft mishaps identified are lack of regular maintenance, old age of aircraft, lack of safe landing equipment, human errors, improper reporting system and fear of blackmail of the pilot.
Viewing the monumental loses from aircraft accidents; accident prevention should be a goal sought by everyone in the aviation industry, as well as by the government.
The Meteorological Services Department of the Federal Ministry of Aviation should continue to recognise the enormous impact of weather on flying operation, particularly civil and general aviation, and provide services tailored to meet the specific needs of this important part of the aviation sector. Increasing reliance should be placed on automated systems, as opposed to face-to-face briefing services, to deliver meteorological information for flight planning and pilot documentation.
It is also essential that up-to-date training and educational material be made available to enable pilots to enhance their knowledge and understanding of aeronautical meteorology and aeronautical meteorological services, so that they can use that information to fly safely and efficiently.
Government should encourage the aviation industry by creating an effective incident-reporting programme. This is done by having reporting systems both at the local (i.e. airline, air traffic facility etc.) and national levels, with the local sources forwarding information to the national system. For a more co-ordinated level of operating the Nigerian National Voluntary Incident Reporting System (NNVIRS) should share information at a global level.
The modern instrument landing system (ILS) should be installed in major airports in Nigeria. The 19 new Distance Measuring Equipment (DME), very high Omni-directional radio range (VOR) on Doppler VOR and locator Beacons installed at two run ways of the Lagos airports should also be installed at all Nigerian domestic and International airports to boost domestic and international flights. Also, routine maintenance of aircraft should be carried out as and when due.
Accidents hardly ever happen without warning. The combination or sequence of failure and mistakes that causes an accident may indeed be unique, but the individual failure and mistake rarely are. Hence poor visibility was identified as a major casual factor that was responsible for the above aircraft accidents in Nigeria. Other contributing factors include; Human error, absence of safe landing equipment, fear of blackmail and lack of regular maintenance of aircraft before they embark on any journey or flight. Finally, it is recommended that accident prevention should be the responsibility of everyone in the aviation industry.
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