1. ICAO SEMINAR ON AIRFIELD PAVEMENT MAINTENANCE AND SHORT COURSE ON AIRCRAFT /PAVEMENT INTERACTION SANTA CRUZ DE LA SIERRA, BOLIVIA 22 TO 27 JULY 2002

2. EXPERIENCE ON AIRFIELD PAVEMENT MAINTENANCE IN AFRICA V P
EXPERIENCE ON AIRFIELD PAVEMENT MAINTENANCE IN AFRICA V P. PERICLES Coordinator Airport Development in Haiti Project HAI/98/ Office National de l’Aviation Civile (OFNAC)

3. OVERVIEW OF AERODROME MAINTENANCE IN AFRICA
Organization of maintenance services.
Management of maintenance.
Priority given to maintenance services.
Maintenance programming /planning.
Maintenance methodology .
Maintenance technology.
Maintenance practices.
Aerodrome maintenance and safety
Relations with and assistance from international organizations
Personnel training.

4. AERODROME MAINTENANCE IN AFRICA
Historical Background
First workshop on this subject – Dakar, Sénégal, 8-12/03/1982
Second workshop on this subject – Dakar, Sénégal, 8-12/02/1988.
Third workshop on this subject – Dakar, Sénégal, 6-12/02/1992
Fourth workshop on this subject – Dakar, Sénégal, 5-8/12/1995.

5. Participation All African States, including States, accredited to the Cairo, Nairobi and Paris Offices were invited. Also invited, were international organizations concerned such as: IATA, ASECNA, IFALPA, AACC (ACI) and the FAA. Total participants: 51,66, 70 and 81, respectively, in the first, second, third and the fourth workshop. Indication of increased interest in the subject.

6. JUSTIFICATION FOR ADEQUATE MAINTENANCE
Continued expansion / construction of Airports in Africa.
Need for higher level and quality of service.
Increased investments made at these Airports.
Availability of best procedures, methods and equipment to ensure serviceability, safety and achievement of substantial savings.
Accomplishment of a high degree of operating reliability to assist in the safe and efficient movement during landing, take-off and taxiing maneuvers.
Need to ensure the establishment of effective maintenance programme

7. ORGANIZATION AND PROGRAMMED MAINTENANCE IN AFRICA
At the majority of the more than 170 Aerodromes in AFI, it exits some form of maintenance organization.
The programs observed (up to 1998) varies in scope, size and effectiveness.
In certain cases, these programs consist of sporadic unscheduled and unrecorded inspections and evaluation of the airport facilities.
There were also cases of well conceived comprehensive programmes with adequate planning, scheduling and well distributed responsibilities.

8. New and more sophisticated equipments and maintenance tools
Engineers had been trained and assigned to airports in the AFI Region the number is below the need. In other States, services were totally lacking, thus creating a vacuum which constituted then, permanent, serious concern for safety.

9. MAINTENANCE PRACTICES GENERAL
BASIC: Maintenance of all structures had been considered vital in order to prolong their economic service life, maintain their standard of appearance and ensure their capacity to operate properly throughout their expected life span.
African states agreed that lack of proper maintenance leads, inexorably, to problems causing undesirable expenses, even disasters.

10. This common concern of states in the AFI Region is not always translated into practice.
Some positive measures are in force today at the majority of international airports in Africa, but not with the desirable consistency and periodicity.

11. MAINTENANCE PRACTICES PRACTICES MOST OFTEN OBSERVED AT AFRICAN AERODROMES
Pavement repairs, cleaning and scaling
Removal of foreign objects (fob) from maneuvering areas.
Routine checks of pavement joints for repairs.
Cleaning of drainage system.
Repair of lighting aids.
Repainting of deteriorated pavement markings.

12. Control of vegetation growth.
Routine repairs of airport buildings.
Inspection and correction of defective sewage system.
Repairs of vehicles, with priority to emergency vehicles.
Routine checks of equipments (COM, MET, ATS …)

13. MAINTENANCE PERSONNEL PROGRESS HAS BEEN ACHIEVED IN AFRICA (1998) IN THIS FIELD
A Section or Department responsible for maintenance has been created at most aerodromes
It comprises a senior engineer who heads a group of engineers and technicians
The number of personnel is often related to the size and activities at the airport.
There continues to have shortage of trained technicians, primarily in the pavement, electrical and mechanical engineering fields.

14. Lately, the introduction of larger aircraft at many aerodromes in Africa and the advent of new technology (CNS, ATM), implies additional heavier burden on maintenance units. Thus, a need for more specialized equipments for maintenance and better organization.

15. SOLVING THE PERSONNEL PROBLEM
Different approaches by States in training and retention of personnel.
Trained personnel are lost to other employees due to lack of incentives and/ or competitivity, also career prospects.
Need to reverse current trend?
a) intensification of training
b) creation of incentives.
c) competitive salaries, career prospects to retain personnel.
d) funds derived from aviation and assistance (UNDP, bilateral arrangements) should be used to finance personnel training and recycling. Participation at this meeting is just but one example of wise investment in human resources.

16. PAVEMENT MAINTENANCE MANAGEMENT SYSTEM
Importance of preventive Vs corrective maintenance.
Periodical pavement evaluation for maintenance purpose.
Evaluation and identification of the pavement surface distress.
Evaluation of the hydroplaning risks of the pavement.
Runway roughness evaluation.
Collecting and reporting of pavement deterioration.
Monitoring of evolution of identified deficiencies.
Planning/programming of corrective intervention.
Financing.

17. STATES USING SUCH SYSTEM (1998 DATA)
South Africa– Integrated Airport Pavement Management Systems (IAPMS).
ASECNA States (16) Similar to JFK, la Guardia and Newark Intl
Ghana- Computer Assisted Management (CAM).
Morroco/Tunisia- use a monitoring system/condition survey
Results: Reduce frequency of large scale and costly intervention.

18. Note: the IAPMS is a self contained software package designed to run on an 1986 class desktop computer.
It assists the engineer or planner to make the kinds of rational predictions of future pavement conditions and performance that are essential for accurate budget forecasting and sound management. The net effect is the preservation of infrastructure through improved pavement performance and reduced maintenance and rehabilitation cost.

19. MAINTENANCE PRACTICES
Preventive maintenance
Routine maintenance
Major maintenance
Landscaping
Environment (protection)

20. Pavement maintenance General* Flexible pavement Rigid pavement
Unpaved surfaces*

21. FLEXIBLE PAVEMENT Preventive measures *Programming / scheduling
-.Routine evaluation
-.Technical evaluation
-.Planned intervention
Corrective measures
-.Short term
-.Long term, resurfacing (overlay)
-.Reconstruction

22. RIGID PAVEMENT (Practices/observation)
General surface texture condition
Structural condition
Pavement sealant and faults in joints
Growth of plants and fungus on pavement and in joints

23. NON CONVENTIONAL /RECYCLED MATERIALS
Fly Ash
Lime cement fly ash
Fibrous concrete
Sulfur asphalt
Shells
Silica sand asphalt

24. FLY ASH ( MAY 1969 )
Mixtures of fly ash from several Electrical Power Plants have been used for the construction of several runways repairs and construction at JFK and Newark Airports.
The Ashes came from the Central Heating Plants of Ravenswood and Astoria of Con Edison and from the Hudson and Mecer Central of the Electricity and Gas Public services of New Jersey.

25. - Sand is available in large quantity in Newark.
The decision to use fly ash for these runway pavements had been taken by the Port Authority of New York and New Jersey ( PONYANJ ) after three years of thorough experimental trials.
Condition that led to the decisions to use ash as a good, cheap material:
- Sand is available in large quantity in Newark.
- Lab experiments were conducted with several additives /mixtures (sand + ash, sand + ash +coke, sand +ash +sodium carbon with mixed results)

26. the adopted formula with respected weight was:
Fly ash – 14 %
Coke – 3.0 %
Portland cement 0,7 – 0.9 %
Sand – 84.5 %
Finally a small quantity of Portland cement was added to the above mixtures, and in each case a good strength was achieved after a reasonable duration of the solidification . In addition the cost was not too high

27. Called LCF (Lime Cement Fly ash) this material offered a strength of 56 to 100 bars in about 90 days at a temperature from 18 to 21 degrees Celsius. As necessary, 30 % of aggregates can replace sand. In which case a strength of 105 bars can be achieved.
The characteristics of the LCF (expansion , module of elasticity sensibility to freeze temperature freeze/defreeze) were determined with precision in the laboratory.
Experiments were conducted at Newark airport. Half millions us dollars were spent to demonstrate that the LCF was, by far, superior to the other formula.
Three contacts for a total of 20 millions USD were awarded for Newark. This program was to be repeated for JFK Airport.

28. As regards the cost
the sand for the Central Heating plants had to be
Humidifed with 16 to 18% of water to avoid spilling of five particles by the wind. Transport to the site costs 2 to 3 dollars/ton. The greasy coke delivered on site costs 6 to 18 $/ton and the cement 20 to 22 $/ton. The mixture operation costs 1 to 1.5 $/ton
Total cost for the runway was found to be half that of the highway and less than one third of the concrete of good strength. These costs do not include the sand which was available on the site.
The judicious use of fly ash for runway pavement permitted significant savings to the Port Authority as well as to the electrical power plants for several years

29. Sulfur asphalt (1973)
Saving from the use of abatement sulfur may help offset cost of pollution control (?)
Sulfur valuable natural resource
1973 abatement sulfur production was a small, 3.5 million tones (3.2 x 109 kg) or 15% of elemental sulfur produced by the West.
In 1975 the production of abatement sulfur exceeded 16.0 millions tones. No exact figure is available to us today
It can be assumed that since a large quantity of sulfur

30. is awaiting development of the technology that could create a useful outlet.
Estimate prepared by the U.S Federal Power Commission (FPC) indicated that abatement sulfur supply to reach 43 millions tones in the early, Figure to be verified
The use of elemental sulfur in sand asphalt-sulfur pavements is still foreseen in Africa (ASECNA, South Africa) as having one of the least potential for the use of this element. (Illinois Institute of Technology)
Shell Canada has developed material using elemental sulfur in asphaltic hot-mixes that permits greater flexibility in mix designs in the utilizations of either sands of minerals aggregates. Shell uses the term “Thermopave” to their sand asphaltic binder sulfur pavement

31. Other studies, US Bureau of Mines, Sulfur Institute, Texas Transportation Institute (TTI)
Final consideration is still dependant on availability of sulfur and cheap aggregates. All conditions considered, the potential for using sulfur asphalt mixture in pavement construction remains high (to be confirmed).

32. Maintenance generally conducted
UNPAVED SURFACES
Maintenance generally conducted
Under contract with nearby public or private companies including nearby farmers. Monitoring by authorized personnel (CAA) to ensure compliance with air traffic safety.

33. Visual and / or mechanical inspection Typical distress looked for: FLEXIBLE PAVEMENT
Cracking of the surfaces (Alligator cracks, random cracks, longitudinal cracking due to failure of underlying pavement layers.
Surface wear.
Loose materials (identification of their provenance)
Subgrade failure.
Deformation of surface
Channelisation of traffic
Localized failure due to overloading conditions.
Pumping.
Vegetation growth on the surfaces.

34. Deterioration attributed to jet fuel spillage and other contaminants (oil, rubber deposits dirt or leakage from cargo containers).
Erosion of pavement edges and shoulders
Surface erosion caused by wind.
Erosion due to poor drainage system.

35. IN SUMMARY FINDINGS 1995 Maintenance levels below required standards
Expensive facilities, specially pavement, being run down fast due to lack of preventive maintenance.
Civil aviation sector being wrongly construed to be a drain to the economy of the country.
Civil aviation considered in some countries as a source of founds.
Quality of services at the airports sometimes below minimum level.
Civil aviation staff demotivated leading to loss of qualified staff (to private sector)

36. ALLOCATION OF FUNDS BY CAA IN AFRICA
In general, allocation of funds for aerodrome maintenance in AFI region is reduced to a minimum.
Survey conducted in 1995 indicates that from the fifty three (53) African States, thirty seven (37) are known to make provisions for maintenance.
Among the States, nineteen (19) are from the Western and Central African Office.
In most of the thirty seven (37) States, the allocation is apparently not sufficient.
In five States, no funds are specifically reserved for maintenance works.
The service is provided but sporadically performed at times not until the affected areas constitute a threat to safety.

37. PAVEMENT MAINTENANCE IN AFRICA THE FUTURE
The problem is not how to design and build new pavement system for larger, heavier, greater frequency and magnitude of loading modern aircraft.
The dilemma is how to upgrade and provide remedial measures for existing pavement systems to meet current and future traffic demands.
Other dilemma, the required systematic team effort (Airport Authorities, the users and decision makers ) is complex and not successfully implemented in Africa

38. THE FUTURE WHAT IS REQUIRED?
a) Establishment of a well organized and thought pavement maintenance plan fully supported by the CAA and government authorities (coordination)
b) To ensure that the higher authorities do not consider civil aviation as a drain to the economy of the country.
c) Achievement the above (b) and remembering that civil aviation development projects are not popular with the providers of the material resources.
d) Provision of incentives to ensure that civil aviation staff are not demoralized, leading to brain drain
Implementation of the use of appropriate new technology
Planning ahead for the resources: financial, personnel, tools and equipments.

39. UNPAVED RUNWAYS IN AFRICA
1- Stabilized lateritic soils
2- Temperate soils
3- Grass Runways
4- Turf

40. UNPAVED SURFACES Problems -.Irregularities of the surface
-.Presence of foreign objects, rocks etc...
-. Pot holes
-.Mud and erosion after heavy rain
-.Vegetation growth on surfaces
-. Loss of bearing strength
Causing accidents due to
-.Loss of control of aircraft by pilots.
-.excessive tire wear.
-.Aquaplaning and loss of control over slippery surface.

41. Note: The ICAO ADREP contains data giving number of accidents which occurred on unpaved surfaces.

42. LATERITIC SOILS
Reddish brown silty clay and coarse to medium fine send with trace of medium to fine gravels.
It contains iron and aluminum oxydes. These soils are subjected to heat. Characteristics which are most intriguing and may explain why lateritic soils can be found only in the tropics.
Laterite available mainly in Central, Eastern and Southern Africa.
Lateritic soils used as sub-base material for construction of roads and runway / taxiway pavements.

43. Limited studies are available on these soils: Ghana Building and Road Research Institute, Study by Samuel A. Ola of Ahmadu Bello
University, Zaria, Nigeria ( A S C E Proc. Paper 10534, May 1974 ) and the study by G.A. Liantaud, Ingénieur en chef du Service Outre–Mer du C.E.B.T.P. France.
It has been demonstrated that less than 50% of the cement requirement for a temperature zone soil is required for efficient stabilization of a lateritic soil. This result demonstrates the need for determining the appropriate cement requirements for lateritic soils like those presented by the PCA for temperate zone soils, (Refer to ASCE Proc by Samuel A. Ola )