We use the Auto Rod and Level (AR&L) profiler to measure the airfield pavements. The AR&L captures elevation data with respect to mean sea level in one foot increments. Typically three lines of survey are measured; one of the runway’s centerline and two offset the centerline 12 to 20 feet (4 to 6 meters). By measuring three lines of survey, the ride quality of each wheel track can be evaluated. In addition to evaluating the pavement’s ride quality, these longitudinal profiles will serve as historical references for any future ride quality analyses as well as for pavement repair considerations.

Using two aircraft types, a narrow body and wide body type, a velocity sweep, or VSweep analysis is conducted on all three lines of measured profile. This ensures that the entire measured pavement profile is assessed for ride quality. The results of this analysis are then organized into 500-foot (150-meter) sections to clearly indicate the ride quality of each section. Following the VSweep analysis, takeoff and landing or taxi simulations are conducted using the same two aircraft types. These simulations quantify the pavement’s ride quality during conventional aircraft operations. The takeoff simulations begin 50 feet (15 meters) into the measured pavement profile and the landing simulations indicate nose gear “touch down” 1,500 feet (460 meters) into the measured profile. Aircraft type, taxi speed, takeoff start, and touchdown point can all be changed to meet the specific operations at your airport. The simulations are conducted on each line of survey from both ends, and the results of these simulations are plotted and included with the final report.

A series of straightedge analyses are conducted to assess the pavement for short wavelength and long wavelength roughness. The short wavelength events are identified with a 16-foot (5-meter) or 3-meter (10-foot) straightedge analysis as described in existing criteria such as the FAA’s Advisory Circular 150/5370-10A or the ICAO Annex 14 aerodrome pavements guide. Either analysis effectively evaluates the pavement for short wavelength events.

To identify deviations that affect aircraft ride quality, we use a longer straightedge. The 100-foot (30-meter) straightedge more accurately reflects the length of the wheel base of the aircraft that use the pavement. The short straightedge and the long straightedge evaluations are performed on each line of measured survey. The results are plotted and put in the final report.

Over time, APR has developed a way to quantify roughness on a runway to make it easier for management to make informed decisions about runway maintenance. This quantification is called a Pavement Smoothness Index (PSI). The runway is analyzed as a whole and then in 250 to 500-foot (75 to 150-meter) sections. There are four main tools that go into assigning the PSI number to each section:

-A visual analysis of the pavement profile
-A velocity sweep (VSweep) of each section flags rough areas. Takeoff and landing simulations help to determine the probability of possible rough areas being encountered at sensitive speeds.
-A straightedge analysis is used next to verify suspected roughness.
-The final factor in the analysis is engineering judgment. Experience enables APR to take into account things such as aircraft type, airport specifics, threshold locations, etc, in assigning a PSI number to each section.