June 1, 2007
Julie K. Boatman
We had pilot reports from the day before, and the weather had been dry for several days. But with a backcountry air-strip you never know.
We approached the strip at Cabin Creek, near Big Creek in the Frank Church River of No Return Wilderness in central Idaho, with a special technique in mind — but one borne from a combination of short-field and soft-field practices.
That the runway was short, well, that was clear from the callout on the Great Falls sectional: 1,700 feet, more or less. That the strip had the potential for a "less than hard" surface was also noted: by the open magenta circle.
From surveying up above, we knew how to prepare ourselves. The meadow grass in the clearing was slashed by water bars and bisected by a pack trail. Water runs through it, and so do horses and mules. A potential soft field, indeed!
We usually think of short-field takeoff and landing techniques as reserved for those times when we need to get out of a tight place (a short runway, with obstructions, perhaps), and of soft-field techniques for when we need to extricate ourselves from a sticky place (a grass runway after the rain).
A short-field takeoff minimizes your overall takeoff roll and maximizes your angle of climb by shortening the distance you cover over the ground to climb to a certain height above it. You accomplish this by continuously and smoothly applying maximum takeoff power, accelerating the airplane to V X, and rotating at that speed and maintaining it for the first segment of your climb, until you clear any obstacle.
At the other end of the flight, a short-field landing configures the airplane and its descent such that you maintain a relatively steep angle to the runway, and touch down positively at the slowest airspeed possible (with a margin for safety) so that your ground roll is as short as it can practically be.
But short-field procedures are more properly called "maximum performance takeoffs" and "maximum performance landings." That's because they come in handy in situations other than takeoffs and landings into your local "aircraft carrier" or tree-lined hole of an airport.
One scenario that effectively lowers your available takeoff or landing distance is operation at a high density altitude — you want to maximize your performance, such that it is. Another may occur if part of your runway is closed, or if only part of the runway has been cleared of ice or snow — cases in which you want to land on the clear area and be as slow as possible, and under control, by the time you come to the messy part (or avoid that part altogether).
You might also use a short-field takeoff to maximize your height above the ground once you get beyond the airport boundary fence. You can reduce your noise signature simply by being higher at this point; you may also feel better about reducing prop rpm (a great noise-reduction tool) at an earlier point in your climb if you're higher.
Like their max-performance brethren, soft-field takeoffs and landings are specialty procedures that address a different need. The goal on takeoff is to get the airplane off the ground as quickly as possible and away from the drag caused by a soft surface. This is achieved by holding the airplane in a nose-high attitude during the takeoff roll and allowing it to lift off at a lower-than-normal airspeed — but promptly reducing the angle of attack so that the airplane does not climb farther and leave ground effect until you've reached V Y or an appropriate speed depending on if you have obstacles ahead.
You typically set up for a soft-field landing when making an approach to a runway surface that is "less than paved" (for example, many grass runways) and possibly questionable. The procedure helps you to touch down as smoothly as possible. You keep some power in to boost airflow over the elevator control surfaces — this gives you the ability to manage your touchdown with greater finesse (and also can keep you in ground effect while you ascertain the condition of the surface from a few feet above it). You're also a little closer to your go-around power setting if the conditions appear less than favorable.
As with short-field takeoffs and landings, flap use varies by your aircraft model, and it's based on increasing the lift in some instances (soft-field takeoff) and maximizing drag in others (short-field landing). Flaps can make a dramatic difference in the angle of climb you achieve. For example, in a late-1970s-model Piper Archer, the flap setting for both short- and soft-field takeoffs is 25 degrees, or the second notch on the mechanical flap lever. If you try to maintain V X (64 KIAS) with no flaps, it's a bit of a struggle, and you don't seem to get much out of it — but it's easy with the flaps in. The airplane feels like it's going up on an elevator (as much as that's possible in the old Archer, valiant aerial soul that it is).
You can also use soft-field techniques on a variety of surfaces, such as snowy or slushy runways, when the grass is wet (even if the ground underneath isn't soaked and muddy), or if you make a beach landing (planned or not).
You should opt for a soft-field landing when landing off airport (unless the area is restricted; then you have a choice to make) if you have power available. One additional technique to use in an emergency off-airport landing: If you're flying a retract, plan on keeping the gear up unless you know you're landing on pavement or another very firm surface. A gear-up landing on just about any surface does far less damage to the airframe and engine than a landing in which the airplane flips over — very likely on a truly soft or rough surface. And, more important, the chance of damage to you is much higher if you dig in the wheels and turn turtle.
The next round goes to pilots who can make a combination of the two — doing it short and soft. I was asked to perform a short-and-soft landing on a checkride once; it was a favorite maneuver of the examiner's. So what does this creature look like?
A couple of techniques used in each procedure seem to cancel each other out — can you really land as slowly as possible with some power still in, or have as much elevator authority? And transitioning from the steep approach required in the short-field landing (typically power off) to the addition of power just before touchdown takes a practiced touch. But that's the challenge, and it can be done. And if you think about it, the two complement each other — and they have to. A lot of grass strips are relatively short. The transition from soft-field to short-field takeoff starts with a liftoff into ground effect, and a continuation of the climb when you reach V X, rather than speeding up to V Y. A simple change that makes sense.
After circling above the special figure-8 traffic pattern at Cabin Creek, we set up for a short-field landing, with a soft-field power management style.
Once past the point of no return (after which go arounds are not an option), we use trees to the left for alignment to Runway 2 — this one-way strip still hides from us — and keep the airspeed tightly in check. Soon we have our aim point in sight; the runway looks firm enough close up, just as it did from altitude. With a smooth initial touchdown, we bounce through our rollout over the rough ground. And I think to myself, "soft" is a relative term.
E-mail the author at firstname.lastname@example.org.
Here are a couple of exercises that will hone your skills in short- and soft-field takeoffs and landings.
If you don't have an actual soft field to work with, establish the point on the taxiway at which you consider the soft area to begin. Then, from that point, keep the airplane in motion while you line up on the runway and initiate the takeoff roll. Lift off into ground effect when able, level off, and climb out once you hit V X.
Upon entering the traffic pattern, configure the airplane for a short-field landing — typically with full flaps, though you may want to save extending the flaps all the way until you're on final.
Maintain a steep enough descent angle to clear the hypothetical (or real) 50-foot obstruction near the runway end. Once clear of the obstacle, begin your transition to a soft-field touchdown, shallowing the descent angle by adding a little power.
Keep a slow airspeed (roughly 1.3 V SO) with just a touch of additional power through your level off, reserving any further power increase for cushioning your touchdown. — JKB
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