Everything That Rises Must Get Down

Aug. 1, 2007
Safely landing a modern airplane is a complex task based on constants and variables. The constants are few but absolute. The variables are modest but numerous—in fact, virtually unlimited. The interaction of these two factors can make for a good landing or something less.

Every pilot has long accepted a cold fact: His technical reputation rides, to a considerable extent, on the quality of his landings. (Bravery and skill in combat are altogether separate categories.) The judgments are rendered by passengers, other crew members, other pilots, and even the pilot himself. With every poor landing, at least his ego suffers.

In the course of making hundreds of landings, every pilot generates a bell curve of performance. The curve ranges from, on the left, disastrous leaps, bounces, and crashes to, on the right, silent and smooth “grease jobs,” where the touchdown is imperceptible. The middle—the highest bulge of the curve—is where you find landings best described as average or ordinary.

Bad landings happen—all the time. To avoid them, the pilot must adhere religiously to the constants of landing an airplane while attending to each of the variables as they occur. They can’t always be avoided, though.

Maj. Gen. Frederick C. “Boots” Blesse, a great ace of the Korean War, also was the author of a useful flying book, No Guts, No Glory. In it, Blesse writes vividly of how the variables can affect a landing.

Blesse had flown about five hours in the F-51 fighter, but his first combat mission was at night, in a Mustang that was so heavily loaded with drop tanks and ordnance that it handled like a completely different aircraft. After dropping his ordnance, he was diverted to another airstrip. There, Blesse discovered firsthand how airfield configuration, layout, lighting, runway condition, and other factors can ruin a landing. In Blesse’s case, the variables kicked in with a vengeance; he encountered bad weather, poor lighting, slick runways made of Marston Mat (PSP or pierced steel plank), and a large truck on the runway. All of this resulted in a spectacular crash on landing.

Thirty minutes after he had been dug out from his inverted cockpit, Blesse was in another Mustang, taking off on his second combat mission, and hoping it would be more tranquil than his first. Fortunately for him, it was.

It is worthwhile to examine some of these variables first, since there is much interplay among them.

The most obvious variable in landing technique is the type of aircraft being flown. A Piper Cub, with its low-powered piston engine, high wing, and a fixed landing gear with tail wheel is rather simple in appearance. It is a demanding aircraft and hard to land, particularly in a crosswind.

Now, consider the F-15 air superiority fighter, a giant, powerful, and sophisticated jet aircraft equipped with a tricycle landing gear. One might assume that, compared to the Cub, landing it would demand much more skill. Yet no less an authority than retired Gen. Larry D. Welch, the former USAF Chief of Staff and commander of Strategic Air Command, voices a different view. He has said that flying and landing the F-15 deceives a pilot into thinking he has “good hands,” whether or not this is true. Much of the credit, said Welch, must go to the multiple computer inputs that are constantly moving the controls.

This emphatically is not to say that it is always more difficult to land a Cub than it is to land an Eagle, but, given pilots of equal proficiency, the F-15 pilot might be the one making consistently good landings, while the Cub pilot would generate an impressive list of bad ones.

The Cub and the F-15 are perhaps extreme examples of the differences in type, but even aircraft in the same class often require somewhat different landing techniques.

The Cessna 172 and the Piper Comanche are both tricycle-gear, four-seat monoplanes of approximately the same weight and size. Yet the wing placement—high on the 172 and low on the Comanche—results in differences in the way the pattern is flown, and in how the aircraft reacts in the flare because of the influence of ground effect just prior to touchdown.

Some airplanes are of such different configuration that their pilots must use polar-opposite landing techniques. Example: The contrast between the B-47 bomber and the V-22 tilt-rotor, which are at the two extremes of landing approach style.

The B-47 required a wide pattern, with a long, flat approach; that is because the bomber combined a relatively high approach speed, low drag, bicycle-style landing gear, and slow-to-accelerate engines. Accurate speed computation, based on the aircraft’s weight, was vital, and both an approach chute (to allow the engines to maintain a higher rpm) and a brake chute were employed.

Two Extremes

In contrast, the modern tilt-rotor V-22 can fly directly to threshold of the desired landing spot in its conversion mode (nacelles at a 60 degree angle), then increase the nacelle angle to 90 degrees and make a vertical descent to touch down at zero mph forward speed.

Almost every other airplane can be slotted between these two extremes.

The type of aircraft helps to determine the method of the approach, particularly the final phase. In a light airplane, with power reduced to idle, the pilot tries to make contact with the ground just as the forward speed of the aircraft declines to the point that the wing is no longer flying. He is, in effect, allowing the aircraft to settle on its own.

This is a delicate process. Any error in judgment can leave you higher than you wish to be—and perhaps out of airspeed.

In those cases, pilots will hear the stall warning horn sound and probably utter a few expletives as they begin the last few feet of the subsequent rapid descent to the pavement.

In contrast, in heavy aircraft, the pilot’s goal is to fly the aircraft, power on, right on to the runway.

This technique requires the use of milestones. One is the 50-foot radar altitude point, where a pilot brings back the power slightly, to gradually decelerate. Then, at the 20-foot point, he initiates back pressure to continuously cut the rate of descent to a minimum, so that, with perhaps half the power on, the main wheels roll smoothly onto the surface. The nose wheel is brought down gently, and the drag devices (spoilers, slats, etc.) are deployed.

Whatever the approach dictated by the aircraft type, the pilot also has to consider the variables within a given airplane, such as weight, center of gravity, and configuration.

Even in peacetime, some airports have hazards that are not easily perceived and that sometimes reveal themselves to the pilot only on approach. These can include the improperly parked truck, new construction, or obscured runway markings.

More subtle are runway imperfections to which local fliers may have become accustomed, but that can be startling on a first encounter. These range from sneaky berms that can cleave an undercarriage leg and abrupt drop-offs at either end to dips or rises in the center that alter a pilot’s depth perception.

Fundamental runway considerations, though almost always factored into take-off computations, sometimes get short shrift in the landing process. These include the length and slope of the runway, field elevation, and the outside air temperature. Many a pilot has flown from a sea-level airport in the East to a Colorado destination, only to be surprised by the effects of the thinner air on landing.

Weather is often the most important variable in landing. When he breaks out of stormy weather, the pilot almost instantly encounters challenges in landing. The pilot, making a transition to a visual landing process, must immediately integrate several factors: the aircraft’s position relative to the runway; the effects of the wind; airspeed; configuration; the possible presence of other air traffic; and the possible need to perform a go-around.

Crosswinds can be nefarious and can affect the airplane in the landing pattern, during the flare, in touchdown, and in rollout. Some conventional-gear aircraft, such as the T-6 or C-45, were particularly vulnerable to crosswinds, even while taxiing. The lightweight Predator UAV is piloted by remote control, but was nonetheless so vulnerable to crosswinds—18 mph was too much—that the Air Force had to build a cross-runway for the UAVs flying from Creech AFB, Nev.

The list of variables goes on and on, but one must also address the psychological considerations involved in a landing. These can range from hubris (“I’ll just tighten the pattern up a bit to show them how a hot pilot lands”) to fear of embarrassment (“If I drop this one in like I did the last one, I’ll run the landing gear up through the wing”).

Even so, most pilots conduct their approaches and landings with a high degree of confidence. The pilot in the cockpit is certain that his or her own experience and technique will result in a smooth touchdown. The good ones remember that, given the almost infinite number of variables, something can always go wrong.

There are many different kinds of approaches to which certain basic constant factors apply. For sake of argument, we will investigate a conventional light aircraft employing the standard 45-degree entry.

Perhaps the ultimate goal in the landing process is to attain a satisfying consistency. The pilot must have long since determined that he or she will fly the airplane—the airplane is not going to fly them. Therefore the pilot should perform each landing in as consistent and as exact a manner as possible. The term “exact” should be interpreted to mean keeping the airspeed, course, and altitude exactly as desired, with any minimum variation being quickly corrected.

On every landing, the pilot should go through the procedures in the same sequence and fly at the same altitudes, airspeeds, and distance from the field. One key to this is continually trimming (relieving control pressures by the use of trim tabs that manipulate the ailerons, elevator, and rudder) so that the aircraft maintains its current course and altitude hands-off. Consistent trimming is one of the keys to consistent landings.

Prior to entering the landing process, the pilot must possess full situational awareness of the condition of his aircraft, its configuration, the weather, the location of the airfield, the runway currently in use, the local traffic, and any surface activity in the immediate area of the runway.

When it is available, the pilot receives information from ground control and establishes contact with the tower for landing clearance. (Many light aircraft operate from fields without a tower, requiring the pilot to be even more vigilant.)

One of the first constants is the mandatory use of a checklist. To someone with hundreds of hours in an aircraft, this may seem unnecessary—but is not.

Getting Close

Inform the tower that you are entering the pattern. Either before or during your entry onto the 45 degree course to the downwind leg of the pattern, establish the aircraft in level flight at the correct altitude above the field for the type and at traffic pattern airspeed. (Assume for this example that you are going to fly at 1,000 feet above ground level and at 98 mph.)

Trim the aircraft so that it flies hands off, and continue doing this. In the landing pattern with so much happening so quickly, it is easy to forget to trim and instead maintain attitude, altitude, or direction with control pressures.

In the pattern, some new variables may be introduced. If there is a lot of traffic of varied types, you may be urged by the tower to increase your speed or to vary your pattern to accommodate local conditions. Some airfields are so busy that the instructions from the ground sound like a tobacco auctioneer’s spiel, so you must be alert to acknowledge and comply with all instructions.

At the appropriate point for the airplane, begin your turn to the downwind leg, check for other traffic, and align your aircraft the appropriate distance from the runway. A pilot familiar with the aircraft will have already selected some point on the wing or the strut which confirms that the aircraft is at the correct distance. If traffic permits, the tower will give you clearance to land. All turns should be carefully coordinated with yoke (or stick) and rudder.

Continue to use your checklist, making such adjustments as applying carburetor heat, and extending the first increment of your flaps, perhaps 10 to 15 degrees. Begin your turn to the base leg as you cross a line extended from the approach end of the runway, allowing the nose to drop, and trimming so that you maintain airspeed and a 300 to 500 foot-per-minute rate of descent.

Clear yourself visually during the turns, and remain alert for instructions from the tower. Observe the runway and the projected approach path, looking quickly both in the direction of the runway, and away from it, in order to detect someone making a long straight-in approach.

The wind will dictate where you begin your turn to final approach. Make a descending turn to the final approach, add an additional increment of flaps, and line up with the runway. Compensate for any crosswind, to maintain a straight flight path over the ground to the runway.

On final approach, add the final increment of flaps, keep your speed at 75 mph, stabilize your flight path and the rate of descent, trim, and quickly check trim for hands-off flight. There are many arguments about whether to use power to control altitude and pitch to control airspeed or vice versa. Probably both need to be used in concert, and if you have properly stabilized and trimmed the aircraft, you’ll not be obliged to use much of either.

Even at this point, be prepared to go around if things do not look correct to you. There is no shame in a go-around.

There is considerable shame in not going around when you should have.

Now, on short final, and given that you have flown a smooth, consistent, well-trimmed approach, the whole question of executing a smooth touchdown depends on your quick assimilation of a series of visual cues. You will have already picked your desired touchdown point, well after the numbers, and you can now look ahead at the far end of the runway to establish a field of vision that will permit your depth perception to function.

As the aircraft approaches the runway surface, keep looking down the field and gently bring the nose up and the power off, maintaining a straight flight path using rudder and aileron. Just above the pavement, do as William K. Kershner, the late great king of instructors suggests: Look out about 100 feet ahead of the aircraft and try to keep it flying as long as possible.

As flying speed falls off, the wheels will touch down ever so softly. Keep the stick or the yoke coming back, allowing the nose to slowly fall until the nose wheel gently reaches the ground. Continue to keep the yoke or stick full back, then, if required for a turn-off, selectively use brakes to slow down.

You may then taxi over to the cheering throng of admiring fellow pilots.

Easier said than done. Walter J. Boyne, a former director of the National Air and Space Museum in Washington, D.C., is a retired Air Force colonel who accumulated more than 5,000 flying hours in various USAF aircraft. He has written more than 40 books about aviation topics, the most recent of which is Soaring to Glory. By his own admission, the author says that he has made some of the worst landings in recorded history, and a few good ones too.