Increasing the Value of Airport Pavement Management

By Michael Gerardi

When you have been in one industry for 23 years, you have the opportunity to make some interesting discoveries – to have that “ah-ha” moment.  My ah-ha moment was discovering the benefit gained when you measure the true profile of a runway, and then years later measure that runway profile again.  When you compare that old profile data to a new set of profile data of the same runway, changes to the profile can be fairly evident.  This article describes the value airports receive when they incorporate runway profile monitoring into their pavement management practices.

Understanding that pavement management is proactive in nature, many world-class airports are adding a new tool to their pavement management program.  That new tool is runway profile monitoring.  Monitoring a pavement profile over time will reveal structural changes that take place over the life of the pavement.  As time passes these profile changes can begin to affect the ride quality of the pavement by increasing the aircraft’s response.  This, in turn, can be the start of a destructive and costly cycle of increased dynamic loading and localized pavement failure.  Increased aircraft response exerts dynamic loading on the pavement.  Each aircraft that responds to an area of roughness increases the loading environment on that localized pavement.  Increased loading, over time, reduces a pavement’s effective service life.  The old saying remains true; “smooth pavements last longer.” 

The answer to this problem is to monitor the pavement’s profile.  The key is to identify the change in profile shape and to quantify the effect those profile changes have on aircraft ride quality.  For example, once differential settlement is detected, implementing an effective set of metrics to determine its effect on aircraft response is important.  Once you determine that ride quality is deteriorating, repairs can then be planned.  This process allows early intervention when the affected area is smallest and least intrusive to correct.  The most effective way to monitor the pavement’s profile is to use a device or method that can measure the pavement’s true profile.  That method will enable the pavement’s profile to be measured initially establishing a baseline profile, and then comparing that baseline to subsequent profiles measured years later.

The following are two case studies that track differential settlement.  As you can see, as the settlement increases, so too does the aircraft response and the dynamic loading on to the pavement.

Table 1 below, lists specific information such as measured change in the profile for a specific event the predicted aircraft response for both case studies mentioned in this case.

This figure plots the deviations from a straightedge for that section of measured profile.  The green area plots the deviations when evaluating the 2007 profile data.  The red area plots the deviations when evaluating the 2011 profile data and the blue area plots the deviations when evaluating the 2012 profile data.  This chart helps illustrate the profile’s rate of change.  This rate of change information is important in determining when to make pavement repairs.

This figure depicts the same simulation (737-800 90-knot constant speed taxi test) only this time is conducted on the profile data measured in 2011.  You can see in the bottom trace that the dip is a bit deeper and that the aircraft response is now predicted to exceed the .40g threshold of acceptability.  This area is now considered to be rough.

This figure plots centerline profile measured at three different points in time; 2005 (top), 2010 (center) and 2013 (bottom).

This figure depicts a 90-knot constant speed taxi simulation of a Boeing 737-800 on the 2005 profile data.  As you can see, ride quality through the area of settlement is predicted to be within acceptable limits.

This figure show’s that by 2013 the dip has become dramatically deeper (bottom portion).  Both the pilot’s station and aircraft center of gravity predict that the aircraft response has deteriorated significantly since 2010.  Increased aircraft response means that dynamic loading is increasing as well.  Continued exposure to this loading environment will affect the localized pavement’s useful life.