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Cooperative extension tries out grass runways

Alaskan pilots accustomed to landing on a remote gravel runway and having their aircraft damaged by rocks may soon be able to make softer landings — on grass runways.
/ Source: The Associated Press

Alaskan pilots accustomed to landing on a remote gravel runway and having their aircraft damaged by rocks may soon be able to make softer landings — on grass runways.

To minimize expensive repairs to dinged propellers or holes in airframes and promote safety, the University of Alaska Fairbanks' Matanuska Experimental Farm recommends grass air strips, planted with hardy varieties. It's a softer surface, meaning longer takeoffs and landings, but it could save an expensive repair.

To make them work, pilots have to forget what they know about planting grass in their front yards.

"People try to establish runway grass like they establish their home lawns," said Stephen Brown, an agriculture and horticulture agent for the university's Cooperative Extension Service. "That will work, but it's much, much more expensive and you can end up with some problems, like soft spots."

The extension last year planted grass onto a gravel runway at Talkeetna. The results were so successful, Brown is touting the method for runways for Barrow, America's northernmost community.

Matt Freeman, Federal Aviation Administration project manager for the airports division, said Alaska has 327 private use airports registered with the agency. That includes sea plane bases and heliports, he said, but there are other landing strips not registered.

Freeman agreed there are more abrasions to airplanes from landing on gravel instead of asphalt or concrete.

"Landing gear pushes gravel into the belly of an airplane or wherever it may go," he said.

Brown, who holds a doctorate in environmental science, has been in Alaska for two years and is constantly on the prowl for putting research to use.

When the developer of a Talkeetna air park — a subdivision with an air strip that lets pilots taxi up to their homes — called to ask how much topsoil he would need to grow a grass on his gravel air strip, cooperative extension officials estimated it would cost him $50,000, then made him an offer he didn't refuse: planting hardy grass right on the gravel.

They planted last August and saw the results in June. "He's got the most beautiful runway you can imagine," Brown said.

There are no bare spots, just the occasional bear spot. "The grizzly bears love to graze on it," Brown said. A low pass by an airplane chases them off.

The keys to the operation are varieties of red fescue, a grass species found all over the world. One subspecies is Arctared Red Fescue, which Brown recommends for air strips in colder regions north of the Alaska Range. If left to go to seed, it grows about 12 inches tall — just enough to make it "really spooky" for pilots when landing, Brown said.

"You can't see what's under there," he said, and at that height, it may mean mowing.

South of the Alaska Range, he recommends Boreal Red Fescue, which grows only to about 8 inches but is less hardy. Red fescue grows in clumps and loves gravel.

"It's a very aggressive grass, and the way it grows, it forms its own sod as it grows," Brown said. Over time, it grows a thin layer over rocks.

"It's like putting netting down on the rocks as it matures," Brown said.

It's excellent erosion control, he said, and even slows or prevents the invasion of moose food, willow and alder, on the sides of runways.

At a workshop Tuesday in Palmer, about 50 people, including pilots, a landscaper and others, showed up to hear about grass runways.

Grass runways require initial landscaping, including a crown for drainage. If water puddles on the surface, grass will die in the freeze-thaw cycle, Brown said.

Brown distributed instructions for collecting soil samples and calculating the amount of seed and fertilizer needed. He gave instructions on how to grow healthy grass that covers a runway while being "slightly starved" so that it does not grow too fast.

"If you grow it the right way, it doesn't have to be mowed very often, if at all," Brown said.

Many rural air strips are inaccessible by road. Brown tailored his instructions to pilots who likely have access to a ubiquitous Alaska workhorse, the all-terrain vehicle. Gravel must be roughed up before planting grass. One method he recommended: dragging an old bed spring behind a four-wheeler.

There may be other applications for hardy Alaska grasses grown on gravel. Brown was expecting one pilot from Barrow and said a grass field might someday replace the artificial turf used by the high school football team.

"Our fantasy is that kids will no longer have to play on AstroTurf," Brown said.