In the interest of shortening the training time needed to earn the private pilot certificate, most flight schools don't introduce students to landing on grass. Some of the reticence to give such training stems from their lack of insurance coverage if the airplane is landed on an unpaved airport. This is unfortunate, because you may want to use such an airport later in your career, and if you don't know what to expect you could be in for some nasty surprises.
That's not to say that your training won't include the soft-field techniques needed for a grass strip. It's just that the training will be conducted on virtual grass (see "Accident Analysis: Soft Realities," August 2007 AOPA Flight Training). The theory is taught, but without any laboratory work to prove it, the point is missed entirely. There's much more to know about using a private grass airport than just how to make a full-stall landing or a minimum-airspeed takeoff. Before you attempt to land on a grass strip after you become a certificated pilot, avail yourself of additional instruction from an instructor who's familiar with some of the local unpaved airports.
What's the difference?
To operate safely from a grass strip requires an understanding of the changing characteristics of the runway surface. With pavement, one day is like every other day; the runway is hard, level, and free of clinging contamination. Each paved airport is pretty much like the all the others, thanks to runway design and construction standards. That's not true with grass. Last month's visit may have found the strip firm and solid, while the same runway a month later could be soft from recent rains, overgrown with grass, and freshly adorned with potholes.
| You must understand the changing characteristics of the runway surface to operate safely from a grass strip. Airports like Misty Isle Farms (top), near Seattle, Washington, and one near St. Petersburg, Florida (above), have one runway. |
| Poplar Grove Airport, east of Rockford, Illinois, offers two grass strips--and a paved runway. Expect the condition of a grass runway to change between visits. |
Grass strips are not all the same. Most have had little earthmoving done, and if they are for the owner's private use, he or she may be comfortable with a narrow track and rough spots to be avoided. The FAA only requires notification of the establishment of a private-use landing area; it does not regulate things like obstructions, slope, or size. An acquaintance of mine flies his Cessna 182 in and out of a backyard grass runway only 1,000 feet long; it's enough for him, and he's the only one who uses it.
And so, if you're going to use a grass airport you need to make sure it's suitable for your airplane and your skill level. Ascertain the usable length, the obstructions in the approach and departure areas, and the condition of the surface. This may mean a ground visit or a trial run accompanied by someone familiar with its quirks. Has it been used by an airplane similar to yours? Is it maintained and used regularly? Don't land there if you can't assure yourself that the runway is in good shape.
Even if you've made other trips into the field and know that it's had regular use, look it over carefully before each landing. This may mean a pass over the runway at an altitude of 300 feet or so, checking for puddles, washouts, tall waving grass, and ruts. As you make your approach, be prepared to go around if anything looks suspicious at the last second. Last night's three-inch rain may have rendered it unusable. You can trust a paved runway, but not a sod one.
Don't plan a first-time flight into a charted grass runway without verifying that it is active; the FAA takes no responsibility for removing private airports from the chart unless notified by the owner. If that person is deceased, the symbol remains on the chart indefinitely. You also need to be sure you're landing on the actual airport; many owners don't mark their strip's boundaries, and with little traffic one part of the pasture can look like all the others.
What will it be?
The "unpaved" symbol on the chart doesn't exclusively mean a verdant, manicured expanse of greensward. The surface can be something other than grass, like sand, gravel, cinders, or just plain dirt. Paved strips shorter than 1,500 feet also rate a bare circle. Sod runways vary considerably; the "grass" can be native plant life supplied by nature, on land undisturbed since the glaciers retreated, or it may have been planted and nurtured after the soil of the airport has been "put to grade" by shaping and compacting it with machinery.
Drainage is vital for a grass airport; rather than being perfectly flat, the surface should slope away from the center crown so it won't trap standing water. To keep the turf thick and even, so it will shed water and keep the soil in place, requires frequent clipping--not with a brush-whacking rotary mower, but with a finishing mower that can keep grass height down to a couple of inches. This encourages spreading growth that heals the wounds of traffic.
Most important, frequent compaction with a heavy roller is needed to flatten the underlying soil and restore ruts, mole runs, and damage from landing planes. Avoid ranch strips frequented by cattle; hoof prints leave a rough surface, and the droppings can do as much damage as small boulders. As you can see, maintaining a good grass strip takes a lot of effort, much more than asphalt pavement. Private strips don't always get what they need, so you must learn each one's individual characteristics.
Performance changes
Don't plan on the usual level of takeoff and landing performance when using a grass runway. Cessna pilot's operating handbooks specify adding 15 percent to the takeoff roll, but that's just an average of widely varying runway conditions. If you're sitting in tall grass higher than the wheels, you may need twice the book's distance to stagger into the air--and then only after beating down a path with repeated runs. (If you're thinking that might be a runway that grass novices should avoid, you'd be right.) Much depends on the density of the grass; thick stands of high grass will create a maximum-power terminal velocity short of liftoff speed.
Stopping distance is affected by the chance of sliding on wet, juicy grass acting as a dandy lubricant under the tires; pump the brakes and try to slow down without locking the wheels. Listen for the change in rolling rumble that signals locked brakes. However, diminished friction is offset by the drag of the grass brushing against the tires; in general, landing distance on grass is affected less than takeoff performance.
Your first off-road experience will be a shock. The noise of small airplane wheels rattling and banging over clumps of grass sounds like your aircraft is being torn apart, which it may with continued use of rough runways. It will take much more power to keep the airplane moving on sod, a precursor to the slow acceleration of takeoff. Avoid running up on bare spots where the propeller can become pitted by sucking up bits of sand, and check the air cleaner frequently for seeds and stems. Exposed brake calipers can be obstructed by torn-off grass.
The stress and strain of frequent grass-strip operation is better left to light taildraggers; retractable-gear and multiengine airplanes should use only the best-maintained unpaved strips. The secret of survival is to minimize the deleterious effects by using the slowest possible liftoff and touchdown speeds.
Take it easy
A proper soft-field takeoff requires a flap setting that produces maximum lift, usually the first or second increment of the handle or indicator. As soon as full power is applied, attempt to raise the nosegear clear of the grass, which cuts the drag by one-third. Be careful not to drag the tailskid and be sure to use extra rudder pressure to hold a straight path, since you're steering with aerodynamics alone. From paved-runway practice, you've learned the minimum unstick speed at which your airplane is capable of lifting off. If it's slow to arrive, consider chopping the throttle and braking to a halt while there's runway left. The airplane will probably signal its readiness to fly by making a few hops over uneven ground.
Once off, level out immediately to take advantage of improved acceleration in ground effect; stay within 10 feet of the ground if you can. If obstructions are ahead, leave the flaps in place and climb away at VX or the POH's recommended speed, retracting flap only after clearing the trees.
Landing requires an approach speed appropriate to the runway length, remembering that stopping distance on grass may be a little longer than normal. Your goal is to prevent the touchdown until as much energy has been dissipated as possible. Keep holding off by steadily moving back the yoke or stick until you reach the up-elevator stop. In some airplanes, it's advantageous to add a touch of power just before touchdown to achieve a slightly lower stalling speed. Keep the stick back after the wheels hit, to keep the nosegear off and add weight to the braking wheels. Unlike your paved-runway practice, you'll find that the nosegear comes down quickly from the drag of the soft sod.
Proper grass-strip courtesy demands that you tamp down any displaced sod you create during taxiing and parking; avoid heavy braking to turn around and don't lock a wheel, which tears up the turf. You don't want to leave a hazardous rut or hole for other pilots.
There's no finer landing surface than a smooth grass strip. Touching down on turf is like walking barefoot on carpet, and the screeching and lurching of burning rubber against asphalt is replaced by the whisper of sod. Treat a grass strip well and it'll expand your options.
LeRoy Cook has been an active flight instructor since 1965 and has had more than 1,350 articles published. He is the author of 101 Things to Do With Your Private License.
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Links to additional resources about the topics discussed in this article are available at AOPA Flight Training Online.
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