The runway at an airport has a specific purpose — to present a surface amenable to consistent takeoff and landing; things get complicated when the surface itself isn’t so consistent. If you happen to find yourself en route to an airport that has a grass strip, yesterday’s… and even last week’s… weather can become hugely important. This time of year, that can mean taking special note of rain and extra special note of temperature changes that can bring the ground out of the frost stage or melt standing snow into it.
THE SETUP — You are taxiing out for departure at your home airport on an unusually warm winter day. On the far end of Runway 9 is a small turnaround area. As you get closer, you see that the winter has been less than friendly to the aging runway, and that thousands of little stones are now loose on the ground. That gives you pause, since you know that if your prop sucks one or more of these rocks up, it will leave nasty and expensive dings in your blades… and anything else the pebble might hit when your prop encourages it to depart the area.
TO STAY AWAY FROM THE ROCKS, you go off the end of the paved strip, and into the grass strip beyond it. You edge up the power, but your progress slows down as you start your turn back to the asphalt. In a moment, your progress drops to zero. You are stuck in the mud — caught by the frost coming out of the ground and snow that has melted into it!
Getting out of the plane, you find your wheels mired — up to the axles — in mud and you’re going nowhere fast. You jump back in, start up, and try jockeying the power around for nearly five minutes before giving up and calling the local airport operator. With a tractor attached to the tail tie down point, the airport operator will be able to carefully (it won’t look pretty) pull the plane backwards out of the mud, and onto the runway.
WHAT HAPPENED — The sensible intent to avoid chipping up your prop, overlooked the fact that the weather change had invited other changes. The ground had been frozen and snow covered, but the top of the ground had thawed during a spell of warm spring-like air. Since only the top five inches were thawed, there was no place for the melted snow to drain to, so the ground became a saturated mush. All it needed was an airplane to move on to it and prove that for the world, sucking in the landing gear and delaying the pilot, but hastening his learning curve.
SELF-DEFENSE: Before you taxi out on to a grass strip or consider using the grass next to a taxiway for any purpose that involves your aircraft, step on some grass at the airport. If you feel the ground give, or if moisture wells up, or if you hear a sucking sound when you pull your foot up, chances are that the ground is saturated with water. While largely a spring-time concern, this can happen at any time of year — for example, you can find these conditions following a few days of major rainfall, as well as during changes in outside air temperatures — like the one much of the east saw over this past winter weekend.
STICKY STRATEGIES: If you get stuck in the mud, power down and get help. Some planes are not equipped with beefy landing gear. Powering up in an attempt to get out can result in a collapse of the landing gear, and a prop strike. Such a turn of events quickly transforms an embarrassing situation into an expensive headache.
BOTTOM LINE: Err, on the side of caution. Our pilot in the above case could have avoided this little life-lesson by turning ahead of the turnaround area and staying on the paved surface. While the option would have required a tight turn he could have found a spot that didn’t include the loose rocks that prompted his concerns in the first place, and still kept the plane on the pavement. Inspect the ground on grass fields and taxiways, and you will avoid getting stuck in the muck!