University of Minnesota Driven to Discover

Briefings

Current issue | Past issues | Subscribe | Download #

2019 Vol. 19, No. 2

Clearing obstructions from your airport

hay bayles

Airport obstructions can interfere with aircraft flight, contribute to turbulence, and attract wildlife—all valid reasons to remove them. An obstruction is any object that penetrates an imaginary surface (FAR Part 77 surfaces that extend out beyond an airport’s runway) or a terminal obstacle clearance area, explained Matt Wagner with Mead & Hunt. These include trees, buildings, cell towers, terrain such as drainage ditches, crops, and construction cranes. With so many potential obstructions, it’s no surprise that most Minnesota airports have had them at some point, Wagner said.

Airport manager Bill Towle shared his experience dealing with obstructions at St. Cloud Regional Airport—specifically, trees. The airport had a professional survey conducted to precisely identify the area, its size, and any environmental concerns (which in this case involved long-eared bat habitat). Towle also engaged the neighboring landowner, and together, they came up with a “win-win” plan, identifying trees that they would take out and others they would only top, he said.

Towle emphasized the importance of daily airport self-inspections as a first step in identifying obstructions. “This is really where it starts...where you should see these things coming, like construction on or near the airport, vegetation, or trees,” he said.

Kathy Vesely (presenting on behalf of Rick Braunig) of MnDOT Aeronautics described the different levels of surveys for identifying obstructions. The ALP survey is the most thorough and accurate, but it’s expensive. An Airport Obstruction Management Plan survey is effective at identifying close-in, recurring obstructions such as brush or volunteering trees off the ends or sides of the runways. Most consultants would be able to assist with this type of survey, as would agencies with survey capabilities, she said.

A 5010 airport inspection (named for FAA Order 5010, which created the Airport Safety Data Program) is conducted by MnDOT every three years to verify that airports meet federal safety standards and Minnesota airport licensing standards. The goal of the 5010 inspection is to find no obstructions, Vesely said. If the inspection does find obstructions, they will only be the nearest or tallest objects. “So once you remove one obstruction, there’s probably another one behind it, and another one behind that,” she said. For that reason, airports shouldn’t rely on the 5010 inspection to identify all their obstructions.

A NPIAS airport with obstructions is at risk of violating its grant assurances, but non-NPIAS airports may still have licensing concerns with obstructions, Vesely said. Obstructions listed on 5010 inspection reports are seen by MnDOT engineers and FAA ADO project managers, potentially influencing project funding for the airport. And pilots see this information and may choose to use an alternate airport. “So you could actually lose business because of it,” Vesely noted.

airplane over forest

Photo: Shutterstock

MnDOT expects airports to take prompt action to remove obstructions and will work with airports on a plan to do so. Once obstructions are removed, someone—typically a consulting engineer—needs to certify that action. The information must also be submitted for the Airport Master Record by someone with credentials the FAA recognizes. This can take months, Vesely cautioned.

“The best plan is to remove obstructions before the 5010 inspection,” she said.

No obstructions means less work for inspectors and eliminates the need to hire an engineer to certify that obstructions were properly removed. Addressing obstructions before an inspection also means pilots are never aware that you had a problem.

Trees and brush grow at a predictable rate, Vesely said. MnDOT recommends cutting at least 10 feet below the maximum height to allow three years of growth before re-trimming. And removing trees in the winter is easier, as wet areas may not be accessible in the summer and bats are not an issue.

Obstructions tend to show up in the same locations year after year, Towle added. “You know where your trouble spots are, or which trees grow faster.” But if you’re new to your airport, look at past inspection reports to see where the trouble areas are, he added. Since MnDOT inspects airports every three years, airports can plan ahead.

For more information:

AirTAP | University of Minnesota | Minneapolis, MN 55455 | Location & Contact Information