The art of fine elevator adjustments
I'm a private pilot with about 200 hours and am having trouble making smooth landings in my airplane. It seems that during the landing flare, the airplane gently descends toward the runway, then suddenly drops. I often over-control and react by quickly pulling aft on the elevator control, sometimes resulting in a bounce. I've worked with an instructor to try to solve the problem but am having no success. Any suggestions?
Sincerely,
Mary
Greetings Mary:
Obviously you've rejected the immediate solution of finding an airplane with longer landing gear. On the other hand, you haven't told me what airplane you're flying, so I'll have to assume it's not the family's Boeing 777 or a Russian MiG. Different airplanes exhibit different landing characteristics, but one thing remains constant: Each is affected to some degree by ground effect during the flare. It sounds to me as though ground effect is having an adverse effect on your landings.
Here's something to try.
One of the reasons an airplane "drops" on you is that the nose tends to pitch downward in ground effect because the wing's downwash on the tail decreases. This makes it difficult to anticipate, much less control, a downward-pitching nose. It's as if the downward pitch of the nose sneaks up on you and doesn't allow much time for reaction, resulting in a hard landing.
There are many variables that affect the rate and degree to which the nose drops (weight, center of gravity, aircraft type, etc.). To compensate for this tendency (as well as one way to always make smooth landings) you need to keep the elevator on the threshold of immediate control. By that I mean that you want to manipulate the controls in such a way that when you pull back on the elevator you know the nose will immediately rise and not experience a delay before responding. Here's the technique for doing that.
After the roundout and during the flare, you'll apply continuous elevator back-pressure, but you'll apply it in small pull-and-release motions. Your objective is to pull aft far enough so that the nose would rise beyond the desired pitch if you pulled even a tiny bit farther. As you begin to release a tiny bit of elevator pull, you'll find a point where the nose would drop if you released any more pressure. I call this point the threshold of immediate control. It's the constant recalibration resulting from this pull-release motion that allows you to make the airplane's nose stay right where you want it to stay and allows you to retain immediate control of the airplane's attitude. This means that the airplane's nose won't pitch downward without your being able to immediately stop its motion. While it may seem like you're fishing for asphalt here, the pull-release motions are so small (if they're done correctly) as to be barely perceptible to anyone in the cockpit, much less outside the airplane.
Over the years, I've observed this technique being used naturally by pilots who've experienced a decline in their kinetic, visual, or tactile sense (perhaps because they've arc-welded without helmets and used jackhammers for recreation and relaxation). It took me a while to realize that what they were really doing was amplifying their sense of elevator response. In this way, they're seldom surprised by a sudden change in attitude be-cause they're continuously making micro control adjustments on the yoke, and continually sensing and compensating for the full effect of ground effect.
It's worth trying this technique on a few landings to see if it gives you a better idea of how to flare your airplane. Ideally, it's better to apply one continuous increasing pull on the elevator during landing. As you get to know your airplane by using this technique, you'll be in a better position to approach that ideal. On the other hand, some folks have a difficult time making landings any other way. That's fine. While they may never be the Muhammad Ali of landings, at least they don't float like a butterfly and land like a bee.
As an aside, this pull-release technique is frequently used by pilots operating deep in the region of reversed command while making extreme short-field landings. Slight forward and aft movement on the elevator lets them know how much (if any) aft elevator travel is still available, as well as how effective the elevator response is.
How a wing can stall from a skid
Dear Rod:
I'm a CFI and am having trouble explaining why an airplane will spin from a skid but not from a slip. Any help on the subject would be appreciated.
Thank you,
Larry
Greetings Larry:
First, remember that any time an aileron moves upward on a wing, it decreases that wing's angle of attack, while a downward-moving aileron increases that wing's angle of attack. That said, consider the following.
A skid causes one wing to descend, in the absence of aileron deflection. For example, start a shallow left turn, then apply more left rudder than is necessary for that turn. The inside (left) wing will descend without aileron application. The descending wing's angle of attack increases as a result.
Make the same shallow left turn, but now apply right rudder and left yoke deflection to hold the inside wing down. The inside wing is forced down and its angle of attack increases, but it doesn't increase that much. Why? Because the aileron on the left wing is deflected upward, diminishing the overall angle of attack on that wing.
The net result is that, in a slip, the angle of attack on both wings isn't that different. In a skid, however, one wing has a much larger angle of attack than the other. This means that if the airplane approaches a stall, the wing with the larger angle of attack (the left one in our skidding example) will stall first, resulting in a spin.
Waste not, want not
Dear Rod:
I have 60 hours and was departing a Class D airport. I was given instructions to "Move into position and hold, Runway 34" (a landing airplane still needed to clear the runway). This runway has a displaced threshold of 300 feet. I made the turn onto the runway/threshold, placed the airplane in the center, straightened it out where the centerline would be, and stopped. The tower (nicely) reprimanded me for not moving to the touchdown line and holding there. Since the threshold can be used for takeoffs, taxi, and run-out operations, why was I wrong to refuse to "burn" the extra 300 feet of runway for takeoff? Even though the runway is nearly 9,000 feet long, I still think it's safer to use the full runway for takeoff.
David
Greetings David:
As long as the threshold was displaced and not relocated, the area behind it can be used for taxi and takeoffs in either direction, or landings from the opposite direction. When you were told to taxi into position and hold, you did what most pilots would do, and that is to use the full length of the runway for takeoff, regardless of its length. If the threshold was relocated (which it might be for construction, structural, or other reasons), then you must use it according to the restrictions set out in the local notices to airmen. This may mean that the displaced portion of the threshold is completely unusable. This doesn't, however, sound like it was the case in your situation. Either way, you could contact the tower at a later time and ask for clarification.
Rod Machado is a flight instructor, author, educator, and speaker. A pilot since 1970 and a CFI since 1974, he has flown more than 8,000 hours and owns a Beech A36 Bonanza. Visit his Web site.
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