Short- and soft-field takeoffs can be fun to practice—especially considering the images of mountain flying and scenic landscapes they may evoke. The techniques you practice on a long asphalt runway for the checkride will be only a baseline to help prepare you to venture to pastoral grass strips, backcountry destinations, and remote airfields. To really get out there you’ll need some additional instruction, starting with whether or not you should even go.
A mnemonic to help answer the go/no-go question is the PAVE checklist: Pilot, Airplane, enVironment, and External pressures. This checklist is used to identify and manage several risk factors associated with each flight and to help develop a pilot’s own set of personal minimums.
John Baglien, chief pilot at McCall Aviation in McCall, Idaho, uses the PAVE checklist before each flight and teaches it when he can. He said it’s important for students to establish personal minimums.
“This checklist will be one of the focal points of our Part 135 recurrent pilot training for McCall Air Service this spring.” he said. “Making the go/no-go decision is the most important skill a student pilot should develop when taking off from this type of field, and this checklist is critical in making that decision.”
As part of the PAVE checklist, you’ll need to consider how your airplane will perform in the current conditions. Factors such as field length, slope, high grass, soggy conditions, and density altitude affect your aircraft’s ability to take off and climb over any obstacles. Tables in your airplane’s pilot’s operating handbook (POH) can help you calculate takeoff distances, but there is one thing you should know about these distances: They’re not accurate. Why? The airplane you’re flying isn’t new, and its maximum performance has decreased with age. You’re also not a trained test pilot like those whose flight testing was used to generate the POH performance numbers. And no two conditions are the same. Think of it like a new car that is advertised to get 40 mpg. You might get close to that, but you’ll probably come up a little short. That’s the last thing you want when you’re taking off.
“Know and use your POH tables for calculating takeoff distances for your aircraft, particularly considering aircraft weight and density altitude,” Baglien said. “But don’t overlook footnoted adjustments regarding runway grass, slope, and/or tailwind.”
Adding a buffer can increase your safety margin. “I prefer to take distance to clear a 50-foot obstacle as my minimum runway length for an unobstructed runway,” Baglien said. The AOPA Air Safety Institute recommends adding 50 percent to the POH takeoff or landing distance over a 50-foot obstacle.
If you’re concerned that you don’t have an adequate safety margin, don’t take off. Wait for a change in weather conditions that will provide the margin you need to take off safely.
In fact, it’s best to plan your departure from a backcountry airport before you even touch down. Many aircraft can safely land on runways from which they cannot easily depart. Backcountry airports often are in mountainous terrain, where density altitude soars far above the field elevation on summer days. And tall grass—which can help you to decelerate on a grass strip—will decrease your acceleration when it’s time to depart.
Even if the weather is good and all of your minimums have been met, your takeoff should have an abort plan. Pick a spot along the runway at which the airplane should be airborne or a minimum speed established. If it’s not, abort the takeoff. “If I’m not at 70 percent of rotation speed by midfield, I abort. I always make sure I’m fully committed to that plan. Halfway down the runway is not the place to evaluate contingencies,” Baglien said.
Short fields. You’ve decided to go. Now you have to use the right technique. For takeoff from a short field, the airplane should be lined up on the runway as close to the threshold as possible. Extend flaps before starting the takeoff roll; the specific amount of flaps will be found in the POH. Apply full throttle while holding the brakes to obtain maximum power before beginning the takeoff roll—sometimes. “This technique works well if you’re taking off from a paved runway,” Baglien said. “But applying full power while holding the brakes on dirt or gravel backcountry airstrips causes prop-tip vortices to kick dirt and gravel up and into the prop. Because of the increased risk for damage, on rough fields like these it’s important to make a rolling start—as you would for a soft field.”
During the takeoff roll, the elevator control should be kept in a neutral position until the target rotation speed is reached. This airspeed is specified in the POH. Then, apply back-pressure to lift off. Accelerate the airplane in ground effect—within about one wingspan above the runway—until you reach the desired climbout airspeed. This will be for either the best rate or best angle of climb.
“This may be a very brief acceleration to best angle or rate as you climb through ground effect at sea level, but will be a more prolonged flight at high density altitudes to allow the airplane to accelerate,” Baglien said. Care should be taken to avoid climbing out of ground effect prematurely—the airplane may establish a shallow climb before sinking back down onto the runway. The best-angle-of-climb airspeed should be chosen if there are obstructions at the end of the runway. This airspeed produces the greatest elevation gain in the shortest amount of horizontal distance. If the greatest elevation gain in the shortest amount of time is desired, the best-rate-of-climb airspeed should be established.
Soft fields. Before departing from a soft field, take a walk down the runway, especially if it’s an unfamiliar field. You may spot that one large hole or rock in the ground that could damage your airplane if you hit it on the takeoff roll.
The objective during a soft-field takeoff is to get the nosewheel out of the mud, snow, or tall grass as soon as possible. Back-pressure should be applied to the elevator control immediately. The flaps should be extended as recommended by the POH and full power applied, without braking. As the airspeed increases, the nose will try to come up. As the elevator becomes more effective, less and less back-pressure will be necessary to keep the nosewheel above the ground.
Because soft and hard spots are mixed in with uneven terrain, keeping the nose in a constant attitude can be very difficult. “Soft-field takeoffs tend to be more difficult because they require developing a feel for the tradeoff between the angle of attack that most quickly raises the nose out of the mud and that which allows the best acceleration to takeoff speed,” Baglien said. “It requires relaxing the initial heavy back-pressure as you accelerate.” Developing a good feel for the amount of back-pressure required to maintain the desired attitude can be honed on long, paved strips.
Once the airplane becomes airborne, gently lower the nose and fly in ground effect until your desired climbout airspeed is reached. Take care not to lower the nose abruptly, so that the airplane doesn’t touch down on the runway. It’s also critical not to climb out of ground effect too early or too steeply, because this will also result in falling back into the mud.
Now go out there, grab an instructor, and have some fun.
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