Copyright © 1996-2005 jsd
Landings involve procedures and perceptions that are just a little bit different from those involved in other phases of flight. A few of them are discussed in this chapter. (Special procedures for forced landings are discussed in section 15.2.)
The approach checklist should cover three things: approach, landing, and go-around. At the point where you decide to perform a go-around, you will be in no mood to go looking for a checklist.
By the same logic, by the time you are established on downwind in preparation for landing, it is already too late to be reading the approach checklist. Therefore, the practical way to use the approach checklist is to review it before entering the traffic pattern. A few miles from the airport, read the checklist, think about it, and commit it to memory. Say it aloud several times if you like.1 Short-term memory is considerably more reliable than long-term memory. Remember that the checklist is not a “do-list”; you don’t have to do each item at the moment you read it on the checklist.
You probably want to make a pocket checklist, as discussed in section 21.6. Make sure you use a written checklist that applies to the airplane you are actually flying. That is, don’t bother trying to memorize some “universal” checklist. Different airplanes have different checklists.
In flight, you know you have to land sooner or later, but you should never allow yourself to get into a situation where you think you have to land on this runway right now. If you are approaching a soft, narrow, short runway with gusty crosswinds and the setting sun in your eyes, it might be a lot safer to land somewhere else. You might have to get a ride from the second airport back to the first, or you might just wait on the ground until conditions improve.
On approach and in the traffic pattern, be extra-careful to see and avoid other traffic. This is discussed in section 16.2.
A particularly risky combination is night VFR at an unfamiliar field. I recommend you don’t attempt this, unless you remove at least one of the risk factors.
See section 13.7.7 and section 21.4 for more discussion of these points. Don’t get complacent. You may know of dozens or hundreds of airports where obstacles are easy to avoid ... but sooner or later you will visit an airport where obstacles are a real threat, and you don’t want to run even a small-percentage chance of finding this out the hard way.
If the IFR approach procedure says “no circling southeast of the field” you should take it as a hint that maybe VFR circling isn’t a good idea either, especially at night.
Don’t descend below a safe circling altitude until you have a nice view of the green threshold lights. They should not be blinking or twinkling, as discussed in section 12.3.
Let’s consider how things are supposed to look on final approach. One important ingredient is to be correctly lined up left/right. The task of getting lined up with a far-away object, without any intermediate guideposts, is unfamiliar to most people.
Figure 12.1, figure 12.2, and figure 12.3 show how the runway looks if you are lined up too far to the left, perfectly on the runway centerline, or too far to the right (respectively).
The distinctions are easy enough to perceive, once you learn how. In all cases, one of the key ideas is to notice that point A lies directly above point B. That means you are lined up on the line from B to A. In particular, we see that in figure 12.1 and figure 12.3, you are exactly half a runway-width to one side. That is, you are lined up on one of the runway edge lines. If you continue with such an approach, you will mow down all the runway edge lights.
If while on final you perceive that you are lined up left or right of the extended centerline, you should not just fly directly toward the point of intended landing. Instead, you should fly over to the extended centerline now and then follow it to the runway. The objective is to be traveling in the right direction when you arrive at the runway.
You will not be able to see the runway centerline during critical parts of the flare, touchdown, and initial rollout. You need to maneuver to reference to the runway edge. You should start applying this skill on short final, while both the center-line and the edge-line are both in view. This is discussed in more detail in section 12.6.1 and section 12.11.1.
Even more important than having the left-or-right alignment is having the proper up-or-down alignment of the approach path. There are several ways to do this.
One of the worst ways is to use “local tricks”, such as passing over the pond at 1500 MSL and then passing over the old red barn at 1000 MSL. Such an approach procedure doesn’t work too well when you visit other airports.
The smart way to control the slope of the glide is to observe and control the slope angle directly. On an instrument approach, the electronic glideslope instrument defines a 3 degree angle for you. At some airports there is a visual aid such as a VASI to define the angle for you. At most airports, though, there is no such guidance, so you simply must learn to perceive angles accurately.
Most people are terrible at judging angles using the unaided eye. Therefore I recommend the following rule of thumb:
Specifically, the rule of thumb refers to the distance between the last joint and the end of the thumb, as shown in figure 12.4.
To use this rule, hold your thumb at arm’s length, and arrange it so your sight line over the end of the thumb extends to the forward horizon, as shown in the figure. Then the sight line over the last joint of the thumb will be four degrees below the horizon. If this sight line extends to your chosen aim point, you know you are on a nice 4 degree glideslope.
In order to make clear the geometry of the situation, figure 12.4 shows how your eye, your thumb, etc. will appear as viewed by your copilot. Figure 12.5 shows how it looks from your own point of view.
Note that for reasons discussed in section 12.7.3, the aim point is generally not the runway threshold.
Your thumb may not be exactly the same size as mine, but if your thumb is smaller your arm is probably shorter and the angle is probably close to four degrees. In any case, you should learn what angle is subtended by your own thumb2 — it comes in really handy.
Another application of this “rule of thumb” is to help perceive the destination of a power-off glide, as described in section 15.2.5.
The next question is, how do you know you are actually following the 4 degree glideslope, as opposed to merely passing through it? Answer: as long as you remain on that glideslope, the aim point will remain four degrees below the horizon.
This is the correct strategy: throughout the final approach segment, your chosen aim point should remain below the horizon by the desired number of degrees.3 To say it the other way, if the angle between the horizon and your aim point is changing, then your intended destination is not your actual destination.
If the angle from the horizon to the aim point is increasing, you are going to land long; if the angle is decreasing, you are going to land short — unless you somehow change what you’re doing. The logic of this is shown in figure 12.6.
The airplane in the figure is flying directly toward point X. It will overfly point A but land short of point Z. As the airplane moves from position 1 to position 2, the angle of A below the horizon increases to 90 degrees and beyond. The angle to point X remains constant, while point Z appears to move closer to the horizon.
If you are on final and perceive the aim point shrinking up toward the horizon, you probably need to add power. Conversely, if you see the angle growing (3 degrees... 3.5 degrees... 4 degrees...), you probably need to reduce power and/or increase drag.
Given that the angle shouldn’t change, what sort of angle is suitable? Within the reasonable range (three to six degrees) it usually isn’t critical which angle you choose. Here are the main considerations:
If you make a too-steep approach, it makes the flare maneuver more difficult and more critical. Also, some aircraft have so little drag (even in the landing configuration) that they have a hard time staying on a steep glideslope, unless they get help from a headwind.
Conversely, if you fly a too-shallow approach, you need to worry about running into obstructions. It also leaves you with fewer options in the event of an engine failure on final.
Generally, if the angle from the horizon to the aim point is less than three-quarters of a thumb (less than three degrees), you are flying a too-shallow approach. Conversely, if the angle is more than a thumb and a half (more than 6 degrees), you are flying an abnormally steep approach.
In all cases you should be extremely sensitive to changes in the angle, since that tells you whether you are going to land long or land short.
Now we come to the most critical task of all: you must control the angle of attack. This is important in all phases of flight, but especially so on final approach when you are intentionally rather low and slow.
One way to maintain a definite angle of attack is to carefully perceive and control both the pitch angle and glideslope angle, by use of outside references, as shown in figure 12.7.
As discussed in chapter 2, for any given flap setting the angle of attack depends on the difference between the pitch attitude and the direction of flight. Therefore if you maintain a definite value for those two angles, you are also maintaining a definite value for the angle of attack.
Trimming the airplane for the desired angle of attack and flying with a light touch on the controls is also exceedingly helpful in maintaining a definite value for angle of attack; see section 12.12.
To make sure the value in question is the correct value, you should look at the airspeed: indicator every so often, but that should constitute only 10% of your looking. The other nine looks out of ten should be directed toward the outside, such as the angles in figure 12.7. The pitch angle shown in figure 12.7 is one way – but certainly not the only way – of perceiving pitch, as discussed in section 2.5.
Controlling angle of attack is even more important than controlling the left-or-right and up-or-down alignment of the flight path. If you show up at the runway slightly misaligned, or slightly long, it is usually not tragic and it is usually obvious how to solve the problem (perhaps by going around). On the other hand, if you lose control of the angle of attack, your flying career could end quite suddenly.
For any given flap setting, there are three vertical angles of interest:
As discussed below, if you perceive and control any two of these angles, you automatically control the third.
Some pilots (especially students) try to oversimplify the landing procedure by worrying about only one of the three angles. This leaves the other two angles completely uncontrolled. Figure 12.8 shows three examples of what can happen if you control only one angle, namely the aim point relative to nose:
For a typical person in a typical airplane, on final approach you can easily see the aim point over the nose. If one day the nose of the airplane comes up and blocks your view of the aim point, you should notice immediately and be at least somewhat alarmed.
There are several possibilities. The most alarming ones are:
Less-disastrous possibilities include the following:
Note that the converse does not hold; maintaining a proper view of the aim point does not solve all the world’s problems, as was illustrated by figure 12.8. To control the airplane properly, you absolutely must perceive and control more than one angle.
In theory, you could concentrate on any two of these angles and let the third one take care of itself. On the other hand, it’s not really any extra work to keep track of all three, and each one is interesting for its own special reason:
Additional discussion of too-steep or too-shallow approaches can be found in section 12.3.
There is one more ingredient in this recipe: the wind. As we shall see, in the presence of wind your direction of flight relative to the ground is not the same as your direction of flight through the air. You need to be able to perceive both.
Suppose you are on a nice 3 degree glideslope, doing 90 knots in no-wind conditions. Your direction of flight is 3 degrees below the horizon and the relative wind is therefore originating 3 degrees below the horizon. Now suppose a headwind of 30 knots springs up. You add power to remain on the 3 degree glideslope. Your flight path relative to the ground is still three degrees below the horizon, but the flight path through the windy air is only two degrees below the horizon.
Figure 12.9 may clarify the situation. The approach commences from a point 1 mile from the runway and 300 feet up; this constitutes a 3 degree glideslope. In the absence of wind, the approach is flown as shown in figure 12.10. You have 90 knots of true airspeed (90 KTAS) and 450 fpm of descent rate. You will reach the runway in 40 seconds.
As shown in figure 12.11, in the presence of wind you have only 60 knots of groundspeed — two thirds as much as in the no-wind case. In order to stay on the 3 degree glideslope, you must descend at two thirds of the rate. This is why you had to add power.
At the reduced groundspeed, it will take you an entire minute to reach the runway. At the end of that minute, the small hot-air balloon that is in the middle of the runway in figure 12.12 will have been blown a half mile, and will meet you right at the runway threshold. Therefore your path through the air is not aimed toward the threshold, but is aimed toward the balloon. Your direction of flight through the air is only two degrees (not three degrees) below the horizon.
The relative wind is the reciprocal of the direction of flight through the air. The wing doesn’t care about your groundspeed; it only cares about the angle of attack, which depends on the relative wind. To maintain the proper angle of attack the pitch attitude will be one degree higher than in the no-wind case.
Conclusion: First, you need to perceive your direction of flight relative to the ground, so you can be sure you will arrive at the aim point as intended. Second, you need to perceive your direction of flight through the air, so you can know what pitch attitude is required to give the desired angle of attack. If you are descending into a headwind, you will need less rate of descent; in any situation where you have less descent you will need less nose-down attitude.
Note that the scheme of estimating the relative wind using the ratio of vertical speed to airspeed gives the correct answer even when nature’s wind is blowing. As shown in figure 12.13, you have a normal airspeed and a reduced VSI indication while plodding down the glideslope into the wind. See section 2.12, including figure 2.14, for some discussion of how this looks on the instruments.
Instruments: About one look out of ten, you should look at the airspeed: indicator on final approach. The other nine looks out of ten, you should look outside, judging the angles as described above. During the flare, you should definitely be looking outside, not at the gauges. You want to land the airplane at a very high angle of attack. You will have to perceive the angle of attack using outside visual cues. During the flare, the airspeed indicator doesn’t tell you anything about angle of attack (as discussed in section 2.13) or anything else you need to know. I once asked an experienced airline captain to tell me at what airspeed his airliner touched down. He said “I don’t know; I never looked. I always have more important things to look at”. That was a good pilot’s honest answer.
Wind drift: On the base leg, you should make it a habit to check your wind drift. Normally you are being blown away from the airport, meaning that after you turn onto final you will have a headwind. If you are being blown toward the airport, watch out! It probably means you are about to land with a tailwind.
Groundspeed: Obviously you should choose a runway that is headed into the wind, so you can land with a low groundspeed. However, beyond the choice of runway, you have little control over groundspeed. Your primary duty is to control airspeed, so you are pretty much stuck with whatever groundspeed results.
Also, it is hard to perceive groundspeed accurately. The perceptions will change according to
See section 12.7.4 for a long list of perceptions you can use to make sure you are landing into the wind at the right speed.
Your Pilot’s Operating Handbook should specify a “normal” landing procedure. It would probably be more accurate to rename it the “basic” landing procedure, for a simple reason: Many pilots are based at short, unpaved, or crosswindy airports. For them, the basic procedure is definitely not their “normal” procedure. The basic procedure should be thought of as the basis, the foundation on which other techniques are built.
In any case, here are the elements of the basic landing procedure: (1) the final approach, (2) the flare, and (3) the rollout.
The main aspects of the final approach were discussed in previous sections.
One more point: In the proper touchdown attitude (in most airplanes), the nose will block your forward view. You will not be able to see the runway centerline.
Therefore, on short final, guide the plane by reference to the runway edge. Otherwise, one of two things will happen: (1) If you manage to keep the centerline in view, you will touch down with much too low a pitch attitude and much too high a speed. (2) If you raise the nose anywhere near enough, you will lose sight of your reference and become an unguided missile.
Transfer your frame of reference to the edge-line while you are still on short final, while you have both the center-line and the edge-line in view. Do it before it becomes 100% necessary. It will be necessary during the latter part of the flare, the touchdown, and the initial parts of the rollout.
If the runway is 40 feet wide, you should say to yourself “I’m lined up 20 feet this side of the edge-line.... I’m lined up 20 feet this side of the edge-line...”. Some tricks for learning this skill are discussed in section 12.11.1.
Don’t fixate on the centerline — it will disappear during the flare.
The term flare refers to the part of the flight where you are raising the nose, from the nose-down attitude on final approach to the nose-high attitude at touchdown.
Note the contrast
|It is a common mistake to raise the nose stepwise, that is, to raise the nose a little bit, see what happens, and then raise it a little bit more, and so forth.||Good practice is to raise the nose smoothly and gradually. The flare is a process, not an event.|
|You should not ask yourself “How much should I raise the nose?”||Good practice is to ask yourself “At what rate should I be raising the nose?”|
At each point in the process, the goal can be thought of in terms of three timescales: how long is it until ...
Those are the three main dependent variables that are the result of the maneuver.
Correspondingly, the three key independent variables that you use to control the maneuver are
Typically you make the decisions in that order: First you pick an airspeed. That determines the height at which you must flare (the faster the speed the higher the flare). Then you adjust the rate accordingly.
In ideal conditions, you can schedule it so that all three goals are achieved at the same time. For any given airspeed, if you start your flare at the right height and raise the nose at the right rate, you can arrange that by the time you are a few inches above ground level, you are just beginning to fly horizontally, and your attitude is just right for touchdown.
If the altitude, direction of flight, and attitude are just right, they imply that your angle of attack, airspeed, and energy are just right, too.
In less-than-ideal conditions, you should not attempt this ideal three-way timing. This is because in the real world you need to worry about wind gusts. You don’t want a wind gust to come along and rob you of your airspeed while you are still several feet above the ground, in the round part of your roundout. Therefore, in real-world conditions you should arrange that items (a) and (b) happen at the same time, and item (c) happens later. That is, after combining goals (a) plus (b), the process for achieving those goals has two main parts:
This is shown in figure 12.14:
During the second part of the flare, you should keep skimming along, gradually raising the nose, until the angle of attack has increased to the point where you can land on the main wheels, with the nose wheel definitely in the air.6 To say it the other way, you should not make a flat, “three-point” landing, with all three wheels making contact at the same time. A three-point landing is proof that your angle of attack is much too low and your airspeed is much too high.
If you find that the skimming phase lasts longer than necessary, then you started with too much airspeed and/or you began the flare too late. If you had too much airspeed on final, next time get rid of it earlier. Trying to unload excessive speed during the skimming phase is not a good idea for two reasons: (A) there is relatively little aerodynamic drag in this phase, because you are in ground effect, and (B) you are spending unnecessarily large amounts of time near the ground where you are at the mercy of wind gusts that could cause you to balloon upward or drop downward.
You want the roundout to be nice and round.
In contrast, every so often I get a student who thinks it is a good idea to wait until the last possible moment and then raise the nose all at once. I call this a “square flare”. Even though you can get away with this under some circumstances, it is a bad idea for the following reasons:
There is no point in learning the square-flare technique (which will work in just a few airplanes, some of the time), when with the same amount of effort you can learn a technique that works in all sorts of airplanes, and gives a much greater margin of safety.
Remember, good pilots are judged on their smoothness, not their quickness.
If the stall warning horn comes on during the skimming phase, when you are flying horizontally a few inches above the runway, it is a good sign. You will be touching down shortly.
Conversely, if the stall warning horn comes on early in the roundout, when you are still several feet above the runway and descending, it is a bad sign. You should add power immediately. Adding power helps in two ways: (1) The power-on stalling speed is lower than the power-off stalling speed (because of the propwash over the wings). This might give you enough lift to arrest the descent. (2) The added power contributes to the energy budget, so you can rebuild your airspeed.
How do you recognize when it is time to begin the flare?
Let us begin by mentioning a few unhelpful answers to this question.
Here is something that actually helps: Use your sense of timing. At each moment on short final, ask yourself how much time t remains until you would, at the current rate, reach zero AGL. When this time t reaches the special value tF (about two seconds), start your flare. (The exact value of tF will depend on what sort of airplane you’re flying, and other factors.)
Of course the actual flare will take longer than tF — roughly twice as long. That’s because tF refers to what would happen if you forgot to flare. During the actual flare, your descent rate is reduced, so you take longer to descend.
This timing technique has some nice properties. It works on wide and narrow runways both. It works during daytime and nighttime both. It causes you to flare at a greater-than-usual height if you have a greater-than-usual vertical speed.
Now all you need is some way to perceive how much time t remains. You don’t need to know the height in feet or the descent rate in feet per second; all you need is some quantity that perceptibly changes as you approach zero AGL. Figure 12.15 shows one such quantity. The left side of the figure is what you should see when you are on final, at a definitely nonzero height. The letters ABCD and WXYZ represent landmarks along the side of the runway. In particular, for night landings you would use the runway lights as landmarks.
The important thing to notice is that the landmarks are not all colinear. In particular, BDZ is a triangle that covers nonzero area in your field of view.
Now, in contrast, imagine that you are on your hands and knees on the runway, so that your eye is just at the same height as the runway lights, about 12 inches AGL. Suppose that landmarks A and W are behind you, but you can still see the others. As shown in the right side of the figure, all the landmarks have become colinear. The erstwhile triangle BDZ has flattened out and now has zero area.
Of course you never actually fly with your eyes at zero AGL. Therefore you need to observe the rate at which triangle BDZ is gradually flattening out. By combining this rate perception with a sense of timing, you can decide when to begin the flare.
You can practice this perception indoors: Put a book on a table, then lower your head until the corners of the book-cover all line up.
Don’t land with the brakes applied. Of course your feet must be on the rudder pedals; just make sure you aren’t accidentally depressing the brake pedals even a little bit. Wait until there is plenty of weight on the wheels (i.e., after the nosewheel is on the ground) before applying the brakes.
At touchdown and thereafter, the airplane should be sufficiently well centered that the centerline is between the main wheels. On a narrow runway you have no choice, but on a wide runway you should land on the centerline anyway. See how close you can come. Make it a matter of self-discipline and pride.
The touchdown should be gentle enough that the nosewheel stays in the air during touchdown and during the first 50 feet of the rollout. This is a good way of proving to yourself (and to all the kibitzers in the airport lounge) that you were in complete control of the landing. To say it the other way, if you hit with a lot of vertical momentum, it will force the nosewheel down like a mouse trap. See also section 12.11.8.
Stay in control during the rollout. Remember, the flight isn’t over until the aircraft is tied down. The NTSB files are full of reports of pilots who made a decent touchdown and then (a quarter mile later) stopped paying attention and had an accident.
After you have taxied clear of the runway, perform the after-landing checklist. This will include items such as carburetor heat off, flaps retract, cowl flaps open, strobes off (for night taxiing, so you don’t blind everybody), boost pumps off, et cetera.
This section discusses the tradeoffs you must make when the field is short, obstructed, and/or plagued by gusty winds.
The key elements of a high-performance landing are:
Consult your Pilot’s Operating Handbook to see how much runway you will need, as a function of headwind, density, and other variables. Make sure your chosen runway is long enough. Include a safety margin, because the numbers in the book are based on perfect pilot technique, and you don’t want to put yourself in a situation where perfection is required. Also, for reasons discussed in section 12.7.4, even if you have a headwind, make sure you could safely land on the chosen runway without a headwind. And avoid landing with a tailwind!
While you’re at it, plan ahead. Do your short-field takeoff planning before landing at an unfamiliar short field, since in many airplanes it is quite possible to get into a field that you can’t get out of. Usually any runway that is good enough for takeoff is more than good enough for landing, for reasons discussed in section 13.7.4.
As discussed in section 5.5, extending the flaps has six main effects:
These influence the landing in various ways:
Also note that in many light aircraft, the last notch of flaps produces its full share of incidence and its full share of drag, but has only a small effect on the stalling speed. Therefore if you didn’t need the last notch for energy management on final, you’ve got very little reason to extend the last notch at all, unless the field is very short and you need to get rid of every last knot of stalling speed.7
A gusty wind or a strong crosswind is a good reason using less than full flaps. Compared to full flaps, reduced flaps has the following consequences:
Finally, while we are discussing configuration: extending the landing gear is an important part of the landing configuration. Please don’t forget this. Double-check it on short final.
In the presence of obstructions, a relatively steep approach will make more of the runway available to you: Consider for example a 50-foot tree quite close to the beginning of the runway. If you use a six-degree approach slope, it will block you from using the first 500 feet of the runway. If you were to use a three-degree glide slope instead, it would block twice as much of the runway. You can get information about obstructions from the Airport/Facility Directory and other sources. Also, whenever a runway has a displaced threshold you should suspect it is displaced because of obstructions.
If your airplane requires a 1000-foot landing roll, and you are landing on a 2000-foot runway, you should arrange things so that you use the middle two quarters of the runway. That gives you a safety margin at each end. It doesn’t make sense to put all your margin at one end or the other.
For an extreme short-field landing, your margins will be much smaller. In this case, your touchdown point will be beyond, but only very slightly beyond, the runway threshold. You must allow for the fact that your aim point will not be the same as your touchdown point, since the flare carries you forward several hundred feet beyond where the a straight-line extrapolation of your approach path would go. The correct procedure is to aim your approach path a corresponding distance short of the intended touchdown point. In extreme cases, the aim point may even be ahead of the runway threshold, as shown in figure 12.16.
On any runway, long or short, pick a definite touchdown zone and hit it as accurately as you can; don’t just land “somewhere” down the runway. This shouldn’t be any extra work; it should be a natural consequence of good aim-point control and good airspeed control, which you need for other reasons.
Pick a definite spot on the runway and land in the zone that begins at this spot and extends 100 feet or so beyond, in normal conditions. If you have unfavorable conditions (such as gusts, wind shear, and/or an inexperienced pilot), the zone will be larger. Make sure the far end of the zone leaves enough room for the rollout, plus a safety margin.
If the field is so horribly short that you need to choose an aim point that is near the threshold, or ahead of it, choose a glide slope that is steep enough that you can fly it without engine power. (Or, better yet, go find a more reasonable runway somewhere else. At any field where you can depart with reasonable safety margins, you should be able to land with considerable margin at each end. See section 13.7.4.)
At any field that is not horribly short, including any field where you make a normal power-on approach, you should not locate your chosen touchdown zone at the very beginning of the runway. There are a couple of reasons for choosing a zone farther down the runway: (a) it gives you more obstacle clearance, and (b) if you should ever have engine trouble on final, you would have a much better chance of being able to make a power-off approach to the very beginning of the runway.
I often fly at a rather short, obstructed field: 1700 feet after the displaced threshold. That’s short but not too horrible; with some skill and some headwind, you can land a Skyhawk using only half of the runway. Some people are overly worried about running off the far end. If you over-react to the possibility of an over-run, you might be tempted to make an extreme short-field approach, so you would have the largest possible amount of runway “left over” in front of you. However, that would be a bad idea, for the following reasons.
Much of flight safety depends on margins and on backup plans. At every phase of flight you should ask yourself how many things would have to go wrong at this point before you would run out of options.
So why put all the safety margin at the far end? What about the near end? Among other things, remember that hitting the ditch at the far end when you’re almost stopped is better than hitting the ditch at the near end at full flying speed.
So, a few years ago I decided that rather than using the first half of the runway, I would use the middle half of the runway. This reduced by half my margin against over-runs, but gave me vastly greater margin against under-runs.
Sure enough, a few months after making that decision, I was with a student who incapacitated the engine9 on half-mile final. At that point we were close enough and high enough that I could glide toward the weeds as shown in figure 12.16, flare, and land on the runway with several inches to spare.
If you land with too much groundspeed, you are in danger of running off the end of the runway. I’ve seen this done on several occasions. It tends to be embarrassing and expensive.
Excessive groundspeed can be due to a tailwind and/or excessive airspeed. Sometimes the one can lead to the other, if you don’t understand the basic principles of flight (chapter 7). Here’s the scenario: Suppose you have a tailwind on final, and you don’t realize it. Because the tailwind is carrying you along, if you don’t do something, you are going to land too far down the runway. To fix this, you unwisely push on the yoke and dive towards the aim point. You may think this solves the problem, but in fact it makes it worse. Now you’ve got too much airspeed (which contributes to a too-high groundspeed) and the tailwind is still there (further contributing to a too-high groundspeed).
Remember, it is OK to use the yoke as the up/down control provided you are on the front side of the power curve and you are willing to accept an airspeed excursion. On final approach, neither of those provisos is true. Using the yoke as the up/down control in such a situation is horribly improper pilot technique. See section 7.3 for more on this.
Nobody intentionally lands with a tailwind. Nobody intentionally lands with excessive airspeed. The problem is, all too often they just don’t notice. Here is a list of things you can notice so you can stay out of trouble. [AS] indicates airspeed cues, and [TW] indicates tailwind cues.
In an airplane that normally touches down at 50 knots, you will use up more than twice as much runway with a ten-knot tailwind than with a ten-knot headwind. Roughly speaking, the amount of runway consumed during rollout depends on the square of your groundspeed at touchdown.
If the wind is so variable that it might switch from headwind to tailwind at the last moment, make sure you have plenty of available runway.
Suppose you are flying at less than standard weight. For reasons discussed in section 2.13.4, the angle of attack will be the same but the indicated airspeed will be less. The percentage change in speed should be half the percentage change in weight. If you fly at the correct (lower) airspeed, you will use less runway. If you use the uncorrected POH airspeed, you will use more runway than POH tables indicate. The aircraft will tend to “float” more than it should, because you arrived with the wrong angle of attack.
Now suppose you are landing at a high-altitude airport, where the air density is less. For reasons discussed in section 2.13.3, the angle of attack will be the same and the indicated airspeed will be the same — but the true airspeed will be greater, the vertical speed will be greater, and the ground speed will be greater, by about 2% per thousand feet of density altitude. Because of the groundspeed, you will consume more runway, about 4% per thousand feet of density altitude. Your POH should contain a chart or table with more accurate information.
Note that in all cases, being able to accurately perceive the angles is a big help.
Proper management of your airspeed during a short-field approach is complicated and tricky. You have some difficult compromises to make. A low airspeed gives you the best short-field performance, but a higher airspeed gives you highly desirable protection against stalling if there is a gust or a windshear (or a lapse in pilot technique).
Your Pilot’s Operating Handbook should specify the speed to use for short-field landing. This is the indicated airspeed you want to have when you begin your flare. In ideal conditions, you could trim for this speed early in the final approach leg, and maintain this speed all the way to the flare. In real-world conditions, however, the wind makes speed management much trickier.
Therefore, you need to include the following steps when planning your approach:
On final (as always!) trim for the appropriate speed and fly with a light touch; this will greatly help you recognize when a windshear occurs, as discussed in section 12.12.
If your approach speed includes a gust allowance and the expected gust does occur, then you are in good shape. Assuming you are at the right altitude and assuming you are not expecting any further windshear, you can just raise the nose and retrim. You are now flying at the handbook approach speed just as if there had been no gust and no gust allowance. The rest of the approach should be straightforward. (You typically need to make a slight power reduction, because in the absence of the headwind you will arrive at the runway sooner, so staying on the glideslope requires less power.)
On the other hand, if the gust does not occur, you will arrive at the runway with too much airspeed. Fortunately, though, if you have followed all the steps above, the gust allowance is less than the headwind component, so your groundspeed is less than the calm-wind short-field groundspeed, and you if you proceed to land your rollout shouldn’t consume any more runway than it would in the calm-wind case.
The foregoing describes the correct procedure, in which you anticipated the windshear. Let’s now consider various situations that could arise if you have forgotten to include a gust allowance in your approach speed.
1) Suppose you are flying at the handbook’s short-field approach speed when a gust or windshear robs you of ten knots. If this happens on long final, several hundred feet above the ground, it is no big deal. You have lots of altitude and lots of time. You can regain your airspeed by diving about 60 feet, according to the law of the roller coaster (section 1.2.1). At this point you are on a new glide path which is 60 feet lower than the old one. This will take you to a point about 600 feet short of where the old one would have (assuming a 6 degree glide slope), but you can correct for this by increasing the power, re-intercepting the desired glide path, and then reducing the power.11
2) Now suppose you suffer a similar unanticipated loss of airspeed when you are only 50 feet above the ground. In this case you have a definite problem. At this point you are on (or below) the desired glidepath and below the desired airspeed. You have a critical energy shortage. You have nothing to gain by pulling back on the yoke; if you try it you are likely to wind up as a statistic — one more “unexplained” stall/spin accident. The proper way to deal with it is to apply full power, as discussed in section 1.4. Simultaneously, dive to regain airspeed. Dive as much as you can without hitting anything, and then proceed with a go-around. Do not attempt to salvage this approach. Instead, go around and set up a proper approach, including an allowance for the windshear.
To stop in the shortest possible distance, the procedure is as follows:
The reasons for these steps are as follows:
The amount of braking force that a tire can provide is directly proportional to how much weight is on the tire. As a consequence, you want to make sure there is as much weight as possible on the wheels before applying the brakes. If the nose is in the air, the wings are still supporting part of the weight of the airplane. Lowering the nose reduces the angle of attack. Retracting the flaps also reduces the angle of attack, since it reduces the angle of incidence.12
A skidding tire provides much less braking force than a non-skidding tire. You never have anything to gain by allowing the tire to skid. Furthermore, skidding can very quickly lead to loss of directional control. If you think the tires might be skidding, release the brakes so they stop skidding, re-establish directional control, then reapply the brakes.
In addition to the loss of braking effectiveness, skidding is very destructive to the tires — it quickly grinds away one part of the tire. The loss of rubber shortens the life of the tire, and the loss all from one place throws the tire out of balance. An out-of-balance tire tends to hop off the pavement, reducing braking and steering effectiveness.
The idea of pulling back on the yoke during braking is simple: it increases the weight on the main wheels (which is where the brakes are). The main wheels are now supporting their normal share of the weight of the airplane, plus whatever down-force is being developed by the elevator, plus whatever share was previously being supported by the nosewheel. The idea is not to lift the nosewheel off the ground, just to bring its share of the weight almost to zero.
See section 12.6.5 for additional discussion of the rollout, including the case of a not-very-short runway.
For a short-field landing (compared to the basic landing described in the previous section) ...
These points can be seen by comparing figure 12.16 to figure 12.14.
If the field is soft, it is important to touch down (1) as gently as possible, with the smallest possible vertical speed, and (2) with the lowest possible groundspeed. (In gusty-wind conditions, these two objectives are somewhat in conflict, and the first one should get priority. That is, it is better to touch down with a tiny bit of extra horizontal speed, rather than to risk “dropping” the airplane into the mire with any appreciable vertical speed.) If the field is bumpy but not soft, the priority goes to touching down at a low airspeed.
The key element of soft-field technique is to use engine power during the flare and touchdown. This helps in two ways: first of all, the propwash over the wings lowers the stalling speed, meaning you can touch down at a lower speed, and secondly, the power allows you to fly horizontally over the runway for an extended time, descending very slowly, gently “feeling for the runway”.
The approach to a soft-field is basically the same as a normal approach. The only differences are as follows:
On short final, after you are assured of reaching the field, you should extend the flaps to get the lowest possible stalling speed.
Fairly late in the flare maneuver, you should add a little bit of power, just enough to maintain level flight, or a little bit less. The required amount of power is remarkably small. You are in ground effect, so there is very little induced drag, and you are moving slowly, so there is very little parasite drag. If you add too much power, the airplane will speed up or climb, which is not what you want. You will be much too busy to look at the engine gauges during this maneuver, so use your ears: you can learn to recognize the right amount of power by its sound.
When the main wheels make contact with the ground, friction will cause the airplane to slow down, possibly quite rapidly. This friction will also create a torque that tends to slam the nosewheel into the ground, so you generally have to pull back on the yoke to prevent this. Also, you can anticipate that the speed-change will drive your body forward (relative to the plane) at just the moment where you want to be pulling back, so tighten your shoulder harness and brace yourself.
As soon as possible after touchdown, reduce the power to idle.
As always, when taxiing on a soft surface, keep the airplane moving. If you stop, the airplane might sink in, and you will be unable to get it moving again.
During the rollout, and during taxiing on rough surfaces, it is usually a good idea to pull the yoke all the way back. The remaining airspeed and/or the propeller blast acting on the tail helps to reduce the weight on the nosewheel. This is important because (1) the nosewheel is usually more vulnerable to damage than the main wheels, and (2) more importantly, if the nosewheel drops too heavily into a pothole it could result in a prop strike.
Here’s an advanced technique: if you are taxiing toward an abrupt bump, such as the edge of a piece of pavement, keep the yoke all the way back and apply a blast of power during the few feet leading up to the bump. If you do it right, in some aircraft the propwash hitting the tail will allow you to “pop a wheelie”, lifting the nosewheel almost (or perhaps entirely) off the ground. As soon as the nosewheel is over the bump, reduce the power back to idle.
If you are based at a paved airport, the ideal way to learn soft-field procedure is to fly somewhere that has a paved runway and an unpaved runway. Land on the paved runway, then practice soft-field taxiing and takeoffs before trying soft-field landings. This way your first experience with a soft bumpy runway comes at the lowest speeds rather than the highest speeds.
We can discuss crosswind landings with the aid of figure 12.17. Up to point B, the approach pretty much the same as any other approach. A lot of things have already gone well: You have the correct altitude, the correct airspeed, the correct direction of motion, the correct left/right position relative to the runway centerline, et cetera.
The main effect of the crosswind is the wind correction angle that can be seen at point B in the diagram. At this point, the airplane’s axis is aligned with its motion relative to the air. This is the alignment you want for ordinary, coordinated flight. However, alas, the axis is not aligned with the motion relative to the ground. This is absolutely not the alignment you want for landing.
If you touch down with the airplane’s axis significantly misaligned with the direction of motion relative to the ground, that’s a problem. It puts tremendous stress on the landing gear as a whole. It might knock the tires off the rims. Also, depending on where the landing gear is situated relative to the center of mass, it might cause a sudden yawing moment, which is a problem unto itself.
The usual technique for landing in a crosswind is to establish a slip, as shown at point D in figure 12.17. (A less-common alternative is discussed in section 12.9.5.)
At point D the airplane is still airborne. It is in a slip, banked toward the upwind side. To establish this slip, somewhere between point C and point D, you need to use the ailerons and rudder together as suggested by figure 16.7 so that you change the direction the airplane is heading without changing the direction it is going. This is a constant-course slip maneuver, as defined in section 11.5.1. Equivalently, it is sometimes called a forward slip maneuver, as discussed in section 11.5.1.
In figure 12.17, the crosswind is coming from the left. left. Early on final approach you observe that in order to keep the airplane’s motion aligned with the runway, the airplane’s heading is pointed a few degrees to the left. This is normal, coordinated flight; the airplane’s heading is aligned with the relative wind, i.e. aligned with the airflow. (For a general discussion of how wind affects groundspeed and direction of travel, see section 14.2.4.)
It is a very bad idea to touch down with the heading not aligned with the direction of travel over the ground. It will create a huge sideways force on the landing gear, and could knock the tires right off their rims. If the tires survive, they will create a sudden large force in the direction you are pointing. This will cause the airplane to scoot off the upwind side of the runway.13
The left/right alignment and positioning has three main goals:
To better understand why things are prioritized this way, let’s discuss what happens if these goals are not met. Let’s discuss them in reverse order:
To learn how to handle the airplane so as to achieve these goals, you can practice slipping along a road, as discussed in section 16.9. There is also some limited value in practicing constant-heading slips, as discussed in section 16.7.
The question arises: at what point should you make the transition from coordinated flight (on final) to slipping flight (for touchdown)? Some pilots prefer to establish the slip on short final or even earlier; the idea is to have time to get the “feel” of the slip. My recommendation, though, is to begin the slip at the about same time you are beginning the flare. The rationale is: (1) A strong crosswind is usually accompanied by a considerable headwind component, delaying your arrival at the runway, in which case an early slip is the last thing you need. It just creates drag which steals energy and aggravates the tendency to land short.14 (2) The winds near the ground are never the same as the winds aloft, so any slip established on final will have to be changed during the flare anyway.
Be sure to correct for whatever crosswind is actually there at each point, not the crosswind you were expecting. Crosswinds are notoriously variable. As you descend and as you travel down the runway, you move in and out of the lee of trees and buildings.
If the crosswind is really strong and/or variable, you might consider using less than full flaps, as discussed in section 12.7.2.
Consider the following scenario: You are all set up for a nice crosswind landing, but then the crosswind increases. What do you do next? Your first move should be to increase the slip angle, so that the airplane’s axis is aligned with its current direction of travel, whatever that may be.
If you are quick to notice the increased crosswind, increasing the slip angle is all you need to do. Problem solved.
On the other hand, suppose it takes you a while to notice the increased crosswind. At this point you have multiple problems: (a) Your left/right position is wrong: you have been blown to the downwind side of the centerline. (b) Your direction of travel is wrong: you have picked up a nonzero velocity toward the downwind side of the runway. (c) Your slip angle is wrong: you need to increase the slip angle so that the airplane’s axis becomes once again aligned with its direction of travel.
If problems (a) and (b) are large problems, your best option is to go around.
If you decide the problems are manageable, your highest priority is (as always) to increase the slip angle, so as to align the airplane’s axis with its current direction of travel. This fixes problem (c). This is the highest priority, for reasons discussed in section 12.9.2. This involves increasing the bank angle and increasing the amount of top rudder.
Your next move is to fix problem (b). That is, you need to change your direction of travel, so as to put yourself on a course that includes an intercept angle that will – nice and gradually – take you back to the centerline. This requires a further increase in bank angle (but no further increase in top rudder).
At the end of the turn, roll out the part of the bank that was used to make the turn. Keep the other part of the bank, the part needed to maintain the appropriate slip angle.
Note that the required turn is a plain old turn. Resist the temptation to solve problem (b) by putting in some “extra” slip so as to move the airplane sideways without changing its heading. This would be a so-called sideslip, and would be a bad idea for multiple reasons. As always, in this phase of flight, the goal is to have the airplane’s axis aligned with its direction of travel over the ground ... even if this direction includes an intercept angle relative to the runway centerline.
|You are now ready to touch down. Land on the upwind wheel. Land on the upwind wheel! Keep the ailerons and rudder deflected even after touchdown. Keep rolling along on one wheel for a while; as the airplane slows down you will need to apply more and more aileron deflection in order to maintain the bank angle. During this part of the maneuver you still need that bank angle to provide the force that resists the wind.||It is a common mistake among beginners to roll the wings level just before touchdown (even though they had been maintaining the correct slip up to that point) — perhaps to make it “look like” a normal no-crosswind touchdown, or perhaps to make it “look like” the sort of wings-level crosswind landing described in section 12.9.5 — but this is not recommened. It is more work, and produces a worse result.|
Only after the upwind wheel has considerable weight on it should you allow the downwind wing to settle. At this point the aircraft is no longer banked. The friction of the wheels on the runway is the only force resisting the sideways force of the wind. The amount of sideways friction a tire can produce is proportional to the weight on it, which is why you must not level the wings until there is plenty of weight on the wheel(s).
Do not neutralize the ailerons. The crosswind is constantly trying to flip the airplane over onto the downwind side. Keep the ailerons deflected to combat this. It doesn’t hurt to slightly overdo it, keeping a little extra weight on the upwind wheel. As airspeed decreases, you will need progressively more aileron deflection to create the required amount of force.
To reiterate, the overall sequence should be:
During this whole process you need to maintain pressure on the downwind rudder pedal, to counteract the weathervaning tendency (section 8.12). As soon as there is weight on the nosewheel, the nosewheel steering becomes effective, adding to whatever steering the aerodynamic forces on the rudder have been providing. Therefore at this point you can expect to suddenly need somewhat less pedal deflection.
Maintain appropriate aileron and rudder deflection during the rest of the rollout, and during taxiing as well. Remember, the flight isn’t over until the airplane is tied down.
There are some exceptional cases where landing on the upwind wheel is not recommended. An example is a late-model Boeing 737, which has a relatively narrow wheelbase, and huge engines mounted below the wing. You have to land with the wings level; otherwise the upwind engine would hit the ground. A similar situation arises with certain amphibian aircraft that have outrigger-type floats or sponsons far from the centerline.
You begin this maneuver by maintaining coordinated flight as long as possible. The direction of travel will be aligned with the runway, but the heading will not, until the very last moment. Then, use the rudder to align the heading with the direction of travel. The wings remain level throughout. Deft aileron usage is needed to keep the wings level during the yaw maneuver, because of the unequal wingip velocity. The remaining few seconds of flight will be a wings-level slip. At this point you are in a wings-level boat turn, but you hope not to turn very much. The idea is to touch down before the sideways force imparts any significant sideways velocity. Once you are on the ground, the wheels can develop a sideways force to counteract the sideways force of the wind.
Loosely speaking, this is sometimes called a “kick out the crab” maneuver, because you are moving the rudder pedal somewhat rapidly to get rid of the wind-correction angle (aka crab angle). However, you don’t want to kick anything in the literal sense. Even though this maneuver needs to be done somewhat quickly, you never want to yaw the airplane too quickly, because a snap roll could result. A snap roll is a definite possibility in this situation, because the airspeed is low.
Except in special situations, this technique is not recommended for typical general-aviation aircraft. Compared to landing in a slip, the wings-level crosswind landing is more work, and there are more things that can go wrong. You need to worry about stalling the downwind wingtip during the yaw maneuver, and if you don’t touch down soon after getting rid of the crab angle, the sideways velocity builds up quickly.
Before you begin the approach, at the time you review the landing checklist, be sure to review the go-around checklist.
There are many situations that call for a go-around. You should think about this in advance and establish guidelines for yourself so that you can begin a go-around immediately when the need arises. This needs to be a well thought-out decision, and the thinking needs to be done in advance.
If you need to go around, don’t wait until the last moment. If you are rolling toward the end of the runway and are worried about running off the end into the trees, attempting a go-around will only make it worse. It is better to hit the trees when you are almost stopped than to hit the trees with almost enough energy for a go-around. An early go-around is good, but a late go-around is worse than nothing.
Here are some guidelines. You can imagine exceptions; for instance if you are flying a glider it is hard to perform a go-around. So you should come up with guidelines adapted to your situation. The point is that you should think about the go-around decision in advance. The accident records contain many examples of people who got into trouble because they spent too long deciding whether or not to go around.
If ATC clears you to land, that does not prohibit you from going around. For instance, if your gear is not down, ATC would prefer to see you go around rather than land gear-up. Similarly, if ATC clears you to “land and hold short” of a runway intersection, they would prefer see you go around early rather than skid through the intersection at the last moment.
Energy mismanagement is the most-common reason for go-arounds. This is a good reason for evaluating your energy situation early and often. Ask yourself: are we high and fast, or low and slow? Fixing an energy problem is easy if you start early, but it is hard or impossible if you start late. Also remember:
When you begin the go-around, do it right. Don’t add “some” power; add full takeoff power.
In a Cessna 152, 172, or 182 with flaps extended, an increase in engine power will magically re-trim the airplane for a lower airspeed, as mentioned in section 2.3. This is annoying when you make small power adjustments on final approach, and downright dangerous when you apply full power for a go-around. Your first defense (which works in all airplanes) is to watch the pitch attitude; if the nose wants to pitch up, don’t let it. Push on the yoke as necessary to keep the pitch where you want it. This is sometimes quite a hefty push. (Practice simulated go-arounds at a safe altitude every so often, so you won’t be surprised.)
Take a look at the airspeed indicator. Raise or lower the nose as necessary to establish the proper airspeed for the go-around.
After you have done the right thing with the power and the angle of attack, start working on the configuration. If you are carrying full flaps, remember that the last notch contributes a lot of drag but doesn’t contribute much to the stalling speed, so you want to retract that notch fairly early in the process. Also, retracting the flaps part way will help with the trim problems. Don’t retract the rest of the flaps until you have a reasonable airspeed margin above the stall. To the extent possible, use the trim wheel to take the pressure off the yoke. (A yoke-mounted electric trim switch comes in very handy for this.)
Make sure you have established a positive rate of climb before retracting the gear. This rule arises because in some situations you may need to perform a “bounce and go” — that is, to touch down on the runway briefly before going around. It is much nicer to bounce on the wheels.
As mentioned in section 12.6.2 and section 12.2, in most airplanes, the pilot cannot see the runway centerline when the airplane is the proper attitude for touchdown. This comes as a shock to many student pilots.
Therefore, we want to land on the center-line by reference to the edge-line.
There are several good ways to learn to do this. Repeated out-of-control attempts to land the airplane are not the recommended way.
A trick that works beautifully in typical light Cessnas (150/152/172/182)16 is the following: taxi down to the end of a disused runway (e.g. the crosswind runway) or a long taxiway that resembles a runway. Taxi into “takeoff position” and shut down the engine. You remain in the left seat, while your instructor sits on the tail, raising the nose to touchdown attitude. You should sit there for several minutes contemplating the perceptions. Compare level attitude with touchdown attitude. You will note that in touchdown attitude, you will not be able to see the centerline or the right-hand edge of the runway, but you will be able to see the left-hand edge. Especially if you move your head a little toward your side of the airplane, you should be able to see the whole sideline — from the point abeam your position all the way to the far end.
You can study these perceptions during taxi. Fortunately, all landings are preceded by takeoffs. Especially in an unfamiliar airplane, you should consciously use the pre-takeoff taxi to practice taxiing on the centerline without looking at the centerline. That has a certain Zen ring to it, doesn’t it? The trick is to taxi by reference to the taxiway edge line on your side. If the taxiway is 40 feet wide, you should concentrate on taxiing 20 feet in from the left edge. The instructor may help by holding a chart in front of your nose, forcing you to control the airplane by reference to the sideline.17 Every ten seconds or so the chart will be moved aside so you can recalibrate your perceptions.
During taxi, you should also practice perceiving height. Ask yourself, “how far below me are the wheels?” You will need to know that when it comes time for landing.
Make sure you have an instructor with you, especially the first time you try this. At an airport with a nice long runway, taxi into position for take-off. Pull the yoke all the way back, as you would for a soft-field takeoff. Using full power temporarily, speed up until the nose comes up to the attitude that corresponds to stalling angle of attack or slightly less. Then retard the throttle almost to idle so that your airspeed does not increase any more. Do not let the pitch attitude or the airspeed get so high that you actually become airborne. Do not raise the nose so much that the tail hits the runway. Then just taxi down the runway in this configuration.
I call this roadrunner mode because a roadrunner, when running only moderately fast, will just scoot along on two legs, with his head very much higher than his tail.
Figure 12.18: Roadrunner Mode
Make sure you don’t run out of runway. One option is to close the throttle, stop, and taxi back. Another option is to add power while you still have plenty of room, take off, and fly away. Be careful to maintain constant pitch attitude as you increase the power. This may require releasing some of the back pressure on the yoke, since in most airplanes increasing the propwash will increase the effectiveness of the tail.
The purposes of this maneuver include:
High-speed taxiing is most easily practiced before takeoff, but can also be practiced after landing.
The traditional (but not the best) way to learn about landing the airplane is try it again and again until it comes out right.
Landing practice has its place, of course — but it is not the only thing, or the first thing, you should do. Especially if you are learning landings for the first time, or are learning to fly a new type of airplane, there is no point in practicing defective landings over and over. That just reinforces bad habits. Also, as Langewiesche (reference 1) pointed out, landings happen so quickly that there is very little time to learn anything.
Therefore, you should leave the traffic pattern. Go somewhere where you have more altitude and fewer other aircraft. Perform the familiarization exercises as described in section 16.11.
You want to spend a fair amount of time practicing slow flight. This is the sort of thing you really want to learn in the practice area, not during an attempted landing. Landing involves flying very slowly, right next to the ground. You’ve got no business trying to fly slowly at three feet above ground level (AGL) if you don’t know how to do so at three thousand feet AGL.
In slow flight, in the landing configuration, make a note of the angle of attack. This is the angle of attack you want to have when you touch down on the runway. Remember the pitch attitude that goes with this angle of attack. Observe the angle the cowling makes relative to the forward horizon, and observe the angle the wingtip makes relative to the lateral horizon. Since at touchdown you will be (I hope) flying purely horizontally (i.e. negligible vertical velocity), the pitch attitude tells you everything you need to know about the angle of attack (at any given flap setting).
You will probably discover that the angle of attack you want to have on final approach is halfway between the cruise angle of attack and the stalling angle of attack. This rule of thumb is related to the more widely known rule of thumb that approach speed should be about 1.3 times the stalling speed.18
This little fact (approach angle of attack is halfway between cruise angle of attack and stalling angle of attack) is more useful than it might seem. It means you can land the airplane — and I mean an on-the-numbers, short-field landing if necessary — even if your airspeed indicator has failed (or you just can’t see it because your lights have failed at night). You should not consider yourself properly “checked out” in an airplane until you know how to do this.
Table 12.1 shows some airspeeds and angles for a typical general-aviation aircraft.19
Airspeed (KCAS) Pitch Attitude Incidence Angle of Climb Angle of Attack cruise (clean) 115 0.0∘ 4.5∘ 0.0∘ 4.5∘ level VY (clean) 76 4.0∘ 4.5∘ 0.0∘ 8.5∘ level (flaps) 76 0.0∘ 8.5∘ 0.0∘ 8.5∘ slower (flaps) 70 2.0∘ 8.5∘ 0.0∘ 10.5∘ descent (flaps) 70 -2.0∘ 8.5∘ -4.0∘ 10.5∘ flare (flaps) decr. incr. 8.5∘ incr. incr. stall (flaps) 53 12.0∘ 8.5∘ 0.0∘ 20.5∘Table 12.1: Landing — Airspeeds and Angles
On approach, the angle of attack is distinctly not the same as the pitch attitude. Don’t be fooled; bear in mind that you probably have ten or a hundred times more experience in level flight than you do in descending flight. You’re not flying toward the horizon any more; you’re flying toward a point several degrees below the horizon. As you transition from level flight to a four degree descent, you need to lower the nose by several degrees in order to maintain the same angle of attack.
The following is a great way to learn some of the skills that you need for landing the airplane.
Choose a safe altitude (3000 feet AGL or thereabouts) and designate it as the altitude of a “virtual runway”. Starting at an altitude 500 feet or more above the virtual runway, set up a power-off glide in the landing configuration (gear and flaps extended) at the normal approach speed. Then, about 10 feet above the virtual runway, begin a flare, so that you wind up flying level, power off, at the virtual runway altitude. As the airplane slows down, keep pulling back, cashing in airspeed to pay for drag, maintaining altitude. Continue pulling back until the airplane stalls. Then make a normal stall recovery.
The point of this maneuver is to learn at what rate you need to raise the nose during the flare to maintain level flight.
As a variation of the above procedure, you can practice “soft field” landings on the virtual runway. After you have flown horizontally at the virtual runway altitude for a second or two with zero power, add enough power to sustain steady level flight. See also next section.
Practice recovering from evil zooms (section 12.11.9) and other types of defective flare (section 12.11.10).
As mentioned above, the landing flare lasts only a few seconds, and if you do a hundred landings you still have only a few minutes of experience handling a flaring airplane. Practicing slow flight at altitude is a tremendous help. Practice this. However, don’t expect it to do the whole job, because (a) the airplane handles slightly differently in ground effect, and (b) you need to learn to perceive alignment with the runway, altitude, descent rate, etc. very precisely, based on visual cues in the runway environment.
Before actually trying to land the airplane, go to an airport with a nice long runway and make a few low passes at a safe airspeed.
During these maneuvers, you will learn to judge your height above the runway, learn to maneuver the plane so that it is centered on the runway, and learn to use the rudder (and opposite aileron) to get the fuselage aligned with the direction of travel even in the presence of a crosswind.
Finally, after you know how to perceive and control what is happening in the runway environment:
Note that it is a very, very bad idea to fly 10 feet or even 5 feet above the runway at a low airspeed. It is OK to stall the airplane at 3000 feet AGL, and it is OK to stall it at 0.5 feet AGL, but it is definitely not OK to drop it in from 10 feet AGL.
After you are comfortable with high-speed flight in the runway environment, and with flaring the airplane at altitude, and handling it in the touchdown attitude, it is time for the most important exercise.
Fly the approach to a nice long runway. As you flare, advance the throttle a tiny amount. The idea is to generate enough power to allow you to fly down the runway in ground effect, a small distance above the ground. This is the soft-field landing procedure, but it works just fine on paved runways, too.20 Strive to maintain one foot of altitude. You should be able to hold this altitude within a few inches. As you become more proficient, try maintaining ever-lower altitudes with ever-finer precision.
The amount of power required is very small, perhaps only 100 RPM above idle. Because the airplane is in ground effect, induced drag is greatly reduced. Because the airplane is moving so slowly, parasite drag is very small.
Gradually raise the nose to the proper touchdown attitude, and keep flying down the runway at “zero point five AGL”. If a gust comes along and drops you the last six inches, it will be a perfect landing.
Remember to keep a careful watch on the runway edge; in the proper touchdown attitude you won’t be able to see the centerline and if you persist in trying to look out the front you will wander off to one side and mow down the runway lights.
Also, keep your wits about you — don’t fly the whole length of the runway and run into the trees at the end. Make a timely decision to add power and go around, or chop the power and land.
Take the time to look down at the runway, to double check your perception of height. Look at the lateral wingtip against the horizon. Get rid of the notion that the landing is something that happens at a point in time. Landing is a process that lasts a goodly amount of time.
After landing, the nosewheel is supposed to stay in the air for a while. For practice, you can make it stay in the air quite a bit longer by adding a tiny amount of power. That creates a situation analogous to the hesitation takeoff described in section 12.11.2.
Even if you don’t add power, try to keep the nosewheel off the ground for as long as you can (provided you’ve got enough runway). This has two advantages.
Another suggestion: You will sometimes (alas) touch down with a too-low nose attitude, so that the nosewheel hits almost immediately. If this happens, gently raise the nose to the proper attitude. Again, the purpose of this is twofold: aerodynamic braking plus a reminder of what proper touchdown attitude looks like. If this causes you to become airborne again, it means that your touchdown speed was much too high, which is a valuable lesson. Just stop raising the nose, wait half a second, and the airplane will re-land.
Consider the situation where you flare too much, too late. That is, you fly down quite near the ground and, while your airspeed is still several knots above the stall, you pull back on the stick quite a lot. The pitch attitude will become very much nose-up. If you allow this pitch attitude to persist, the airplane will zoom up a few feet and then stall. At this point, there is no way to prevent a crash. The usual stall-recovery procedure (diving to regain airspeed) will not work. You won’t be able to dive enough, because the ground gets in the way.
This is a common and very serious mistake. It is a particularly evil type of zoom. (Some other books call it “ballooning” but that seems like an insult to all the beautiful hot-air balloons and helium balloons in the world.)
Obviously you want to stay out of situations from which no recovery is possible. The solution in this case is simple: you absolutely must observe the pitch attitude. If you see a large nose-up pitch attitude, begin a recovery immediately. Do not wait to hear the stall warning horn. Do not wait to feel aerodynamic indications of a stall. Push the nose back down to the attitude that corresponds to slow flight (roughly 15 degrees nose up in typical airplanes) and apply full power immediately. You know that the airplane can fly level at full power in this attitude, so if you achieve that attitude and that power setting soon enough (before you have lost too much airspeed) you will be fine. It is important to practice this procedure, as discussed in section 16.21.6.
Do not try to salvage the landing. Go around!
You cannot recover from an evil zoom simply by reversing the process that got you into trouble. During the upward zoom and the downward “reverse zoom”, the airplane loses so much energy due to drag that you will not be able to arrest the descent in time for touchdown. To say it again: If you see a bad nose-up situation and try to recover just by pushing the nose way down, the airplane will dive right into the runway nose-first. This is an example of a pilot-induced oscillation, as discussed in section 16.4.
You can reduce your chance of falling prey to an evil zoom by thinking about the pitch attitude at all times. You need to control attitude in the short term, as a means of controlling altitude in the long term.
Nothing is perfect. Sometimes the flare is noticeably imperfect, yet not so bad that a go-around is required. The number of possible imperfections is enormous, so we can’t discuss them all, but it is worth discussing how to handle the most-common cases.
Remember that for any given airspeed on short final, there will be exactly one ideal altitude at which to begin the roundout, and one ideal rate at which to raise the nose.
Scenario #1: Suppose you begin the roundout a little bit too late, and/or raise the nose too slowly during the initial moments of the roundout. You can detect this by noticing that the ground is rushing up toward you and will reach you too soon.
Solution: Raise the nose at a slightly higher rate than usual, fast enough to arrest the descent in the available time. This results in an almost-nice roundout, just a little bit squared-off. At best, this salvaged flare will end at a point where you have the right altitude (a few inches) and the right vertical speed (zero), at the cost of having too much airspeed. If there is enough runway available, just skim along until the airspeed bleeds off, then touch down. On a short runway, don’t attempt to salvage this scenario. Go around — the sooner the better.
Scenario #2: Suppose you begin the flare at about the right time, but you raise the nose at too great a rate during the first part of the roundout. (This can be considered a very mild version of the evil zoom discussed in the previous section.)
Solution: If you notice this early enough, you can salvage the situation. You should temporarily stop raising the nose. Hold a constant pitch attitude for a few moments. This constant pitch attitude will not correspond to a constant airspeed, nor a constant angle of attack, nor a constant vertical speed. The airplane will lose energy, lose airspeed, and develop an ever-increasing rate of descent. You may think that lowering the nose is the “obvious” way to undo the error, but you should resist the temptation; by the time you have manage to lower it, you will be at too low an altitude with too great a descent rate. Therefore, just hold a constant pitch attitude. Adding a smidge of power (a) will keep things from happening too fast, and (b) means you will have more energy at the end of the roundout. (If you add too much power, then at the end of the roundout you’ll have more energy than you need, causing prolonged skimming as discussed in the previous scenario.) As you fly along at constant pitch attitude, at some point you will see a combination of airspeed and descent rate that you recognize from your previous normal landings. At that point, resume raising the nose at an appropriate rate.
Scenario #3: Suppose you begin the flare too early. Your first indication that something is wrong might be the following: You are flying a nice circular looping path that will be tangent to the ground; that is, you will reach zero altitude at just the time you reach zero vertical speed. However, alas, you notice that in order to do that, you are raising the nose at a rate that will lead to a stall before the roundout is completed.
Solution: Add a little bit of power. During the rest of the maneuver, raise the nose at a reduced rate. (Once again, if you add too much power, it could eat up a lot of runway.)
As discussed in section 2.7, it is vitally important to be aware of how much force you are putting on the yoke. This is good practice in all regimes of flight, but it is particularly important on approach. In particular, imagine you are conducting a short-field approach, which means you’ve got no excess airspeed. Suppose on long final everything is just right: the right direction of flight, the right pitch attitude, the right angle of attack, the right airspeed — and in particular, the right trim.
You can — and should — confirm that you’ve got the right trim by letting go of the yoke.21
Now suppose that on half mile final the airplane spontaneously pitches down.
The airplane is trying to tell you something! It is trying to tell you that it lost some airspeed — presumably because of a windshear. This is a very, very common thing to happen on final. You are presumably landing into the wind, and the headwind is almost certainly stronger at pattern altitude than it is on the ground. Therefore you are virtually guaranteed to encounter a decreasing headwind during the final descent. This will rob you of some airspeed. If you are lucky, it will happen so gradually that nobody notices. If you are not lucky, it will happen suddenly. A few knots will suddenly disappear from the airspeed indicator (which you may not notice) and the airplane will want to pitch down (which it is your duty to notice).
The all-too-common temptation is to pull back on the yoke, trying to maintain pitch attitude and (vainly) hoping to maintain constant angle of descent. This is not smart.
Remember: the airplane is trimmed for a definite angle of attack. If you pull back on the yoke, you are forcing the airplane to a higher angle of attack (and a lower airspeed). Since you were already trimmed for short-field approach speed, this is definitely not a good idea.
To reiterate: the yoke is not just a control carrying commands from you to the airplane — it is also a valuable sensor carrying information from the airplane to you.
With rare, brief exceptions, you should keep the airplane trimmed for the desired airspeed (or, rather, angle of attack). You should be aware of (and wary of) any force you apply to the yoke, forcing the airplane off its trim speed.
Additional discussion of airspeed management, including compensation for windshear, can be found in in section 12.7.
Some of my students learn faster than others. The ones that learn the fastest are the ones who have internalized a set of high standards (and even higher goals) and who have learned to critique their own performance. These folks give me a good feeling. I know that they will continue to get better even when I’m not in the plane — a pleasant contrast to those who get gradually worse when left to themselves, and depend on the instructor to get them back in shape.
The standards for a good approach and landing are reasonably easy to remember:
If you can do all those things, you don’t need an instructor to tell you it was a good landing.