Runway Pavement Evaluation

The evaluation scope is defined in consultation with the airport operator or AAI (Airports Authority of India), covering the runway, taxiway, and apron sections to be assessed. Airside access permits and security clearances are obtained. A testing schedule is coordinated with ATC (Air Traffic Control) to identify available windows — typically at night or during low-traffic periods — when the runway can be closed for FWD testing and coring. Historical pavement records, construction drawings, and previous evaluation reports are collected.

The pavement surface is divided into sample units per ASTM D5340, and each unit is inspected for surface distresses — cracking (longitudinal, transverse, alligator, block), rutting, ravelling, patching, bleeding, weathering, joint faulting (for rigid pavements), and FOD potential. Each distress type is measured and rated for severity (low, medium, high) and extent. The Pavement Condition Index (PCI) is calculated for each sample unit and an area-weighted PCI is determined for the entire feature. Rubber deposit accumulation in the touchdown zone is also assessed.

FWD testing is conducted during the approved runway closure window. The FWD applies a dynamic impulse load (40-70 kN for flexible pavements, 70-120 kN for rigid pavements) through a 300 mm loading plate, simulating an aircraft wheel load. Deflection is recorded by 9 geophones at prescribed radial offsets. Tests are conducted at 25-50 metre intervals along the runway centreline and at the wheel track offset positions. Pavement surface temperature and air temperature are recorded at each test point for temperature correction.

Pavement cores (100-150 mm diameter) are extracted at representative locations to verify layer thicknesses and material types against as-built records. Core samples are tested for bituminous content, density, and compressive strength in the laboratory. In the cored holes, a Dynamic Cone Penetrometer (DCP) is used to assess subgrade strength, which is correlated to <a href='/services/cbr-test'>CBR values</a> for back-calculation input. Cores are patched immediately with cold mix to maintain runway operability.

FWD deflection data is temperature-corrected to a standard reference temperature (typically 35 degrees C for India). Using software such as BAKFAA or ELMOD, the deflection basins are back-calculated to determine the elastic moduli of each pavement layer and the subgrade. The back-calculated moduli are compared with typical design values. Structural capacity is assessed by computing the allowable aircraft load repetitions using FAARFIELD or equivalent software. The PCN is determined using the technical evaluation method (T) based on back-calculated layer properties.

The PCN is computed and reported in the ICAO standard format: PCN value / pavement type (R for rigid, F for flexible) / subgrade category (A-D) / maximum tyre pressure category (W-Z) / evaluation method (T for technical, U for using aircraft). Where the existing PCN is insufficient for the design aircraft fleet, overlay thickness is designed using FAA AC 150/5320-6 methodology. For <a href='/services/rigid-pavement-design'>rigid pavements</a>, slab replacement or unbonded overlay options are analysed. Remaining structural life is estimated in years and cumulative departures.

The final evaluation report includes: executive summary, pavement inventory and history, PCI survey results with distress maps, FWD testing data with deflection basin plots, back-calculation results, PCN determination with full ICAO notation, remaining structural life analysis, friction test results (if conducted), overlay design recommendations with cost estimates, and a prioritised maintenance and rehabilitation plan. The report is formatted for submission to DGCA and AAI as required for aerodrome certification.