Evaluating Runway Designs

Evaluating Runway Designs

Evaluating Runway Designs

By Mike Freeman

Having been in this business for over twenty years, we have seen roughness issues of all kinds. Roughness can come from sub-grade problems, from a pavement’s age, or from poor quality construction. There is one kind of roughness though, that is most easily avoidable: roughness built into the design.

Roughness can creep into the design most often in areas of intersecting runways or when the design is being tied into existing grades. The following case explains the consequences of choosing not to perform a roughness analysis on a runway design.

The runway in question is at a major metropolitan airport in the southeast United States. This runway was designed, built, and opened before APR got the call. When we did get the call, the person explained that one of the first aircraft to operate on the newly opened runway nearly bottomed out the nose gear strut, causing the pilot to complain. As the days progressed, the airport quickly realized they had a serious problem, as several pilots had made their complaints known to the tower. The airport wanted to know two things from APR: What went wrong? Who is at fault?

Here, you can see that the “as is” profile has some dynamic profile changes associated with it. The design, in the lower portion of the plot, seeks to reduce those profile changes into something more consistent.

The dynamic profile of the ‘as is” profile doesn’t produce very good ride quality. Aircraft simulations predicted that when simulating a 737-800 conducting an 80-knot constant speed taxi operation, up to 1.0g of accelerations can be expected at the Pilot’s Station.

After making profile measurements using the Auto Rod and Level, we went to work determining the exact location and severity of the roughness. Once we determined that, we entered the design data into our evaluation software, and began comparing the “as-is” pavement with the design.

In the end, we determined that while the contractor did not meet the design perfectly, the design itself was flawed. Even in a perfect construction situation the pavement would likely still have generated pilot complaints based on the design.

Had the design been sent to APR before construction, the entire situation would have been avoided. APR would have been able to work with the designer to achieve an acceptable design while maintaining non-smoothness related concerns.

Here, APR is evaluating the proposed design data of the new profile. Using the same simulation parameters, you can see that the aircraft will have a much improved response once repaired.

We were, however, still able to offer significant cost-savings by determining the exact location of roughness. Instead of re-constructing the entire area, we were able to help them use a combination of panel removal and diamond grinding to alleviate the long-wavelength roughness. In addition, our conclusions helped the pavement owner, contractor, and designer come to an agreement and share the cost of the repairs. This saved potentially millions of dollars in litigation.

The bottom line is that it is much easier and more cost effective to make changes to a design in the office than to change an as-built pavement in the field. Pavement owners and designer must take every precaution to ensure that the design is acceptable before a project goes out to bid.

Evaluating Runway Designs

Evaluating Runway Designs

Roughness can creep into the design most often in areas of intersecting runways or when the design is being tied into existing grades. The following case explains the consequences of choosing not to perform a roughness analysis on a runway design.

After making profile measurements using the Auto Rod and Level, we went to work determining the exact location and severity of the roughness. Once we determined that, we entered the design data into our evaluation software, and began comparing the “as-is” pavement with the design.

In the end, we determined that while the contractor did not meet the design perfectly, the design itself was flawed. Even in a perfect construction situation the pavement would likely still have generated pilot complaints based on the design.

Had the design been sent to APR before construction, the entire situation would have been avoided. APR would have been able to work with the designer to achieve an acceptable design while maintaining non-smoothness related concerns.

The bottom line is that it is much easier and more cost effective to make changes to a design in the office than to change an as-built pavement in the field. Pavement owners and designer must take every precaution to ensure that the design is acceptable before a project goes out to bid.

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