# Complex Method of Airfield Pavement Condition Evaluation Based on APCI Index
## 4 PSI Method  
In the Air Force Institute of Technology, a different method of pavement evaluation was developed, in which the measure of the usage value of airfield pavement is called the Present Serviceability Index calculated from the Equation (9) [27; 28]:  
\[PSI=5.0-S_{w}-0.3\cdot\sqrt{Z+N}-0.22\cdot S_{p}^{2}, \tag{9}\]  
where: \(PSI\) is a present serviceability index [-]; \(S_{w}\) is the average longitudinal evenness measured with a lath of 4.0 m length [cm], \(S_{p}\) is the average transversal evenness measured with a lath of 1.2 m length [cm]; \(Z\) is damages indicator [%]; and \(N\) is repairs indicator [%]. The serviceability of airfield pavement to perform air operations by aircraft evaluate is as follows: \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{3}{*}{\begin{tabular}{c} **Pavement** \\ **Technical** \\ **Condition** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Pavement** \\ **Class** \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} **Damage** \\ **Indicator** \\ **Z** \\ **[\%]** \\ \end{tabular} } & \multirow{3}{*}{\
\begin{tabular}{c} **Pavement** \\ **Friction** \\ **Z** \\ **[\%]** \\ \end{tabular} } & \multicolumn{3}{c}{**Technical**} & \multirow{3}{*}{
\begin{tabular}{c} **Repair** \\ **Indicator** \\ **\(R_{L}\)** \\ **[mm]** \\ \end{tabular} } \\  & & & & **[mm]** & & **CC** * & **AC** \\ \hline Very good & Class I & \(Z\leq 10\) & \(\mu>0.57\) & \(R_{L}\leq 4\) & \(D<1.0\) & \(D<1.0\) & \(N\leq 1\) \\ \hline Good & Class II & \(10<Z\leq 15\) & \(\mu>0.54\) & \(4<R_{L}\leq 6\) & \(1.0\leq D\leq 1.5\) & \(1.0\leq D\leq 2.0\) & \(1<N\leq 2\) \\ \hline Medium & Class III & \(15<Z\leq 22\) & \(0.50<\mu<0.54\) & \(6<R_{L}\leq 8\) & \(1.5<D\leq 2.0\) & \(2.0<D\leq 3.0\) & \(2<N\leq 3\) \\ \hline Moderate & Class IV & \(22<Z\leq 25\) & \(0.47<\mu<0.50\) & \(8<R_{L}\leq 10\) & \(2.0<D\leq 2.5\) & \(3.0<D\leq 4.0\) & \(3<N\leq 4\) \\ \hline Bad & Class V & \(25<Z\leq 80\) & \(0.43<\mu<0.47\) & \(10<R_{L}\) & \(2.5<D\) & \(4.0<D\) & \(4<N\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: A set of parameters qualifying the condition of the airfield’s functional element pavement [27; 28]. \begin{tabular}{l l l} \(PSI\geq 4.5\) & - & very good, \\ \(4.5>PSI\geq 4.0\) & - & good, \\ \(4.0>PSI\geq 3.5\) & - & fair, \\ \(3.5>PSI\geq 3.0\) & - & sufficient, \\ \(3.0>PSI\geq 2.5\) & - & critical, \\ \(2.5>PSI\geq 2.0\) & - & insufficient, \\ \(2.0>PSI\geq 1.5\) & - & bad, \\ \(PSI<1.5\) & - & very bad. \\ \end{tabular}   
The critical condition means that there is a need for maintenance treatments or the repair of the pavement. In the insufficient state of use, the surface may be the reason for damage to jet aircraft, therefore the general overhaul should be considered. A bad condition of the surface means that the surface is not suitable for use and a general refurbishment should be carried out. In the case of a very bad technical surface, the surface is not suitable for use and a thorough reconstruction is necessary. Attention is drawn to the fact that the value of the Present Serviceability Index was determined based on testing and measurements of the following properties of the airfield pavement:  
* The area of damages,
* The area of repaired pavements,
* Longitudinal evenness,
* Transversal roughness. For pavement condition evaluation, when qualifying for the general renovation, parameters describing the condition of load capacity and friction of the assessed pavement were not taken into account. Documenting the technical condition is performed in detail and the inventory of the airfield's functional element pavement is provided. This is a very important process and at the same time a labor-intensive task that requires high knowledge and experience from the expert. Therefore, obtaining a reliable description is a fundamental matter to the reasonable planning of renovation works.