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Commercial aircraft are large vehicles. The
777-200 has a gear spacing, the distance as measured from the nose landing gear to the center
of the main landing gear, of 84 feet 11 inches (26 meters). Additionally, commercial
aircraft operate on runways at high rates of speed; 133 knots for a 777-200 takeoff
(rotation) speed. Considering the length and speed associated with these vehicles, the
wavelengths that they respond to can become quite long. To evaluate the pavement for
these long wavelengths, APR uses aircraft
simulation that can predict how the aircraft will respond to the measured
pavement profile.
In addition to aircraft simulation, APR can also emulate any straightedge length necessary. Typically, APR will
use a 100-foot (33-meter) long straightedge using a 1-inch (25mm) allowable
deviation. This tool helps pin-point events that are likely to cause unwanted
aircraft response.
The California Profilograph is a common tool used for pavement acceptance and, with
it's 25-foot (7.6-meter) length, does a good job at identifying short wavelength
roughness. However, it has limitations when assessing a pavement for roughness that will
affect aircraft response. Only grade control will help eliminate long wavelength roughness
events.
Got questions? We've got answers. Please contact us.
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