Chapter 5: In-Flight Decisions

5.1 Introduction

The crux of soaring cross country is decisions. Many are crucial but none are more crucial than those made while in flight. Some very important decisions must be made prior to takeoff, such as those of task selection and pre-flight planning discussed in earlier chapters. This chapter will concentrate on decisions made after release and before landing. Those discussed here may overlap somewhat those discussed in the Landing Away chapter.

First, we must make one thing clear. This is a racing sport. Don't kid yourself that it's not. Any cross country soaring flight, with few exceptions, is a race against time. This is true of distance flights as well as speed tasks. Maximizing distance means maximizing speed in the fixed time available for the flight.

You should, therefore, keep well in mind that all in-flight soaring decisions, other than safety decisions, are based on covering the most ground in the shortest time; conserving the most number of seconds, etc. Any good soaring pilot becomes very time conscious early in the game. This is an absolute necessity for success in this game. We are, of course, discounting the rare pilot who is satisfied to soar around the airport on Sunday afternoons at the tops of thermals. Since the subject of this book is soaring cross country, we assume that you pilots are no longer challenged by just staying up. You, presumably, wish to taste this cross country part of the sport and now realize wherein lies the real challenge and the real fun.

5.2 Decisions Just Off Tow

The first decision you must make in the air is to decide not to release early regardless of being towed through a big boomer. Of course, you should mentally mark these thermals but, in general, almost all experienced pilots agree that there is hardly ever any instance where it is not in your best interests to take the full 2000 foot tow. This is doubly vital in a contest because landing back at the airport usually means waiting at the end of the takeoff line. It can throw your timing off for the day and cost you valuable points.

The second major and important decision that you should make in the air immediately after release is to stay with any lift you have when you are below 2000 feet unless, of course, you are drifting out of airport range.

The third major decision is to decide not to leave the airport until you are sure you can stay up. We realize that you can never be absolutely sure but in this case we mean at least 95 percent sure. It is always a good idea to get the feel of the air and watch other ships carefully before getting brave in this respect.

5.3 Height Band

The next series of decisions will be those extremely important ones made while enroute soaring cross country. You must try to form, continually revise, and relate to your position at any instant, a mental picture of your overall flight as it relates to the accomplishment of the predetermined task. The height band is an important consideration in the progress of your flight. Let us start with a definition.

The height band is the attitude range within which you should fly. It extends from a safe low level up to cloud base or to a height at which the lift has weakened and to where it is not in the best interests of the flight to continue climbing. Later we will discuss in depth how to determine the lower an upper limits of this band. The limits of the height band are influenced not only by the strength of the lift which is, in turn, a function of the time of day, weather, etc., but also by the terrain, clouds, visibility, task length, and other factors which will be detailed later.

5.4 When To Go (Top Of Height Band)

The biggest mistake of beginning cross country soaring pilots is staying in a thermal too long, that is, after it is no longer efficient to do so. This is a natural mistake since the first thing that any glider pilot learns is to climb as high as he can, period. This is not wrong when a pilot is learning in fact, it is very important for a soaring pilot to know how the top of a dry thermal feels and how to identify it.

A big and important step, however, is to learn to leave a thermal when it is still "good" but not good enough to maximize your speed.

Let's get specific now and give a general rule of thumb about the top of the height band, or, in other words, what is involved in making the decision to go or when to leave the thermal. In the middle of a good day, on a medium task, when the thermal tops or cloud bases are, say, at least 4000 to 6000 feet above the ground, you should leave a thermal when you are in the upper part and the lift drops to about 70 or 80 percent of the maximum value for more than a turn or two. You had better re-read the last sentence a time or two and let it sink in.

This is, admittedly, a general rule but at least it should be put down in writing so that you will have some guideline for a beginning. However, we must immediately say that many variables influence this 70 to 80 percent figure. It is based on the assumption that you can move at your best speed to fly to the next thermal and contact and maintain the maximum lift again. This percentage figure would be modified down (maybe drastically) if:

1. Cloud pattern ahead did not look as good.

2. Overcast ahead.

3. Thunderstorm or cu-nim shadow ahead.

4. Rougher or higher terrain ahead.

5. Wet terrain ahead.

6. Turnpoint ahead.

7. Time to start final glide.

On many days with cumulus clouds, the thermal strength increases up to and into the base of the clouds. In this case the top of the height band then becomes the cloud base. Of course, we feel compelled here to mention that you should observe the legal vertical proximity to clouds which the F.A.R. will allow.

In deciding how much the seven above mentioned items influence the top of the height band is a matter of judgment depending on each individual case. This judgment is developed with experience. In general, the less experience a pilot has, the more conservative he is. If things look different ahead, the pilot with less experience will tend to fly higher before he makes the decision to go. This is correct and natural. The judgment that is involved here is usually the separating factor between champions and almost champions. We have more to say about these influencing factors later.

5.5 Height Band Vs. Time Of Day

The time of day influences many important parameters of a sailplane flight, not the least of which is the height band. So that we might better improve our mental picture of how these important parameters vary with time of day, a few sketches might be in order.

[Figure 5.1]

Figure 5.1

First, study Fig. 5.1 which shows how the lift may vary with time of day on a good day. The specific numbers for lift are not particularly important. What is more important is that you develop a feel for the fact that lift will increase rather abruptly once it starts in the morning and will end rather abruptly once it starts to quit at the end of the day. Notice in Fig. 5.2 that not only does the thermal strength vary with time of day but so does the thermal height, that is, the tops of the thermals vary with the time of day. We see in Fig. 5.2 that the tops may be only 2000 to 3000 feet when the thermals first start in the morning and slowly rise until the middle of the day at which time they generally stay rather constant until the end of the day when they quit. Many times when you can find that last late evening thermal, the top is often as high as any have been all day.

[Figure 5.2]

Figure 5.2

Remembering that these figures represent a typical good day not influenced by any sudden air mass changes or other abrupt factors. Let us look at Fig. 5.3, which is a typical plot of the height band vs. time of day. Notice carefully that the solid line represents the tops of the thermals vs. time of day and the upper dashed line indicates the top of the height band which, of course, is some percentage below the tops of the thermals as we indicated earlier.

[Figure 5.3]

Figure 5.3

Again, let us remind you that these figures are rather qualitative in nature and the specific numbers on the curves may not be valid but the overall figure does show typical trends. This figure assumes no clouds because the top of the height band is limited by cloud base on many days.

A fact emphasized by Fig. 5.3 is that if you should have reason to fly at the very, beginning of the day such as you might on a distance task, notice the height band is very narrow at that time and the top is practically at the top of the thermal. As the day gets better and the lift increases, the thermal tops get higher. The height band, therefore, broadens and the difference in height between the thermal top and the height band top also broadens. Another important consideration is that toward the end of the day when conditions begin to "soften up," the top of the height band again goes to the top of the thermal, the bottom of the height band moves up rather rapidly and you become more conservative. There is no substitute for being high at the end of the day!

Remembering that Fig. 5.3 is time of day vs. height, let us look at Fig. 5.4, which is time of day vs. climb rate. Do not confuse the vertical axis (climb rate) with the height in feet in Fig. 5.3 or the thermal strength shown in Fig. 5.2.

[Figure 5.4]

Figure 5.4

Climb rate is related to thermal strength in that we try to make our climb rate as high a percentage of the thermal strength as possible. This is a function of our ability to utilize the thermal most efficiently. It is very important to get a good mental picture and a good physical feeling for the true climb rate. Many pilots actually use a stopwatch to time their altitude gain over a period of one minute, to determine their net climb rate. It is difficult to watch the variometer and do an accurate mental averaging computation.

We tend to think that our net climb rate is the maximum that the variometer reads at any time during the last several circles. This gives an erroneously high estimate of the net rate of climb. Some sophisticated variometers have an integrating circuit which totalizes the variometer readings and gives a net climb rate readout directly. Let's assume that we do not have one of these goodies so we have to make some sort of intelligent estimate. Now back to Fig. 5.4 for some concentrated study. The upper curve is the maximum climb rate that we can achieve in a thermal at any specific time of day (the specific time of day is indicated by a vertical dashed line). The bottom curve represents the rate of climb at which we should decide to leave the thermal or the minimum acceptable rate of climb. In other words, how much must the lift drop off in a thermal before we make a decision to leave? This gets back to the big decision we referred to in the previous section. In the case of this figure, and for the purposes of our study here, we are assuming that things took good ahead and this decision is not influenced by any of the seven parameters mentioned in the "When to go" section (5.4).

Fig. 5.4 shows that at the beginning of the day when the thermals are just starting, our net climb rate is very low and the two curves are together, so we should decide to be patient and leave the thermal at the top. In the middle of the day when the lift is strongest, we make our decision to leave the thermal when the lift drops to about 3/4 of the maximum. At the end of the day we again should make the decision to stay in the thermal all the way to the top as the two curves are together and the net climb rate is again quite low.

A few other very important observations can be made from studying these figures. Study them carefully and see if you can understand why during the early part of a distance day, a turn or two at zero sink at the top of a thermal may be called for but such a thing later in the day would be wasteful and therefore intolerable.

Tasks such as speed triangles and out and return can be assumed to require a fixed length of time. Considering the meteorological and other conditions, an estimate should be made of how long the particular task should take and, after adding a little margin, this length of time should then be fitted on the time of day scale of the above figures. As an example, the length of time between the two dashed vertical lines in Fig. 5.4 would be a typical assumed task time. It would be obviously prudent to utilize the strongest portion of the day for your task. On such a day, first climb to the top of a thermal to check the thermal height and the loss of lift at the top. This is commonly done in competition before going through the starting gate. It is not uncommon in contests or on speed record attempts to take off an hour or so before the anticipated start time. This hour is spent evaluating the thermal height and size as well as how the lift varies in the thermals.

From a study of the figures, notice that from middle to late afternoon we should be on guard for "softness" in thermals and a little less "character" to the clouds. When this condition is suspected, we ease the height band up (both the top and the bottom of the band) and as conditions continue to fade, we narrow the band upward all the way to the top. This would be true on a distance day then, hopefully, at the end of the day you would be at the top of the last afternoon thermal and ready to start a final glide at maximum L/D speed. An important and well proven axiom in soaring is: "Stay high at the end of the day" (if you can!).

5.6 When To Stop And Climb (Bottom Of Height Band)

We have discussed the major decision of when to leave a thermal and also should by now have some feeling for how the height band decisions would vary with the time of day. Let us now think about the equally important decision of when to stop and climb. This might better be called how to keep from flying into the ground. There is no more sickening feeling than to realize, too late, that you should have stopped and circled about a mile or two further back and 500 feet higher. This great decision has caused gray hair to appear on many a soaring head. We wish there were some magic answer we could give which would set a specific number that you could memorize and to which you could always adhere; but as you have no doubt guessed, such a pat answer does not exist. All we can do is discuss the influencing parameters and conditions and attempt to help you make better judgments.

Without beating around the bush any longer, we will go out on a limb with a general rule of thumb, as follows: In the best part of a good day, with numerous thermals looking good ahead (terrain, clouds, etc.), don't stop for any thermal (of course slow down while going through) if you have descended only a few hundred feet (or maybe 1000 feet) below the altitude, you left the last thermal. An exception would be if the lift in the thermal core, as measured by your well compensated (total energy) vario, tells you that it is significantly stronger (at least 150 percent) than the last core you worked. Now, go back and read the last two sentences several times and meditate carefully about it.

Suppose it is not a good day, or suppose it doesn't look too red hot ahead. Then, the influencing, factors raise their ugly heads and we must become more cautious. The altitude to stop and thermal then depends on:

1. Clouds ahead (good cu vs. dissipating cu vs. overcast, etc.).

2. Terrain ahead (available landing places).

3. Terrain ahead (likelihood of good thermal sources).

4. Turnpoint or goal ahead.

5. Time of day.

In summary, the decision as to when to stop and start climbing depends on your chances of getting back up or landing safely. Some pilots have rules such as working any lift below 2000 feet or maybe later in the day work anything below 3000 feet. Such a rule would be unthinkably conservative for top ranked competition pilots in some areas of the country under strong conditions on a good day. Of course, in other parts of the country on a lousy day, these figures may be somewhat rash.

5.7 When To Hold

In the normal progression of a cross country soaring flight, a rhythm is usually set up whereby one climbs and penetrates, climbs and penetrates, and this continual progression of events tends to get a groovy feeling about it which experienced soaring pilots refer to as the rhythm of a flight. When things are going well, this rhythm is unbroken, but more often than we like to think about, something, comes up to break this rhythm. Sometimes it is a poor decision at the bottom of the height band which gets us into a low scrape from which it takes time to recover (and, of course, from which we sometimes don't recover, and land away) and this breaks the rhythm. Sometimes for some reasons we choose to break the rhythm at the top of the height band and this is what we refer to as a hold. This is also when we move the height band up abruptly and it usually has to do with what things look like further along the course.

The only excuse for holding is the belief that conditions ahead will improve. Inexperienced pilots sometimes hold at the top of a thermal while making a decision. We are not referring here to this type of hold. The experienced sailplane pilot makes his decisions about the next cruise leg while he is climbing. The type of hold we are referring to is a waiting process In anticipation of conditions improving ahead.

To hold means to mark time. It means losing valuable seconds, which in turn means to either lose distance or speed for the day. That is why you should never hold unless you feel it will save you time in the long run, or that it will enable you to get more distance for the day.

Practically, the only reason for holding is to await a change in the weather. Weather conditions which might possibly warrant consideration for a hold would be an overcast, a blue hole, a thunderstorm, or, perhaps, a front. It is generally better to consider a detour instead of a hold if the detour will maximize your measured distance or minimize your time. Generally, the sooner a detour decision can be made, the better.

As previously stated, an experienced pilot will make this decision to detour while he is climbing. Pilots holding at the top of a thermal while in the thinking process can take a long time deciding. This is an intolerable waste of time if there is an opportunity of moving on and continuing the flight by means of a detour. A detour may be necessary for reasons other than weather, such as wet terrain ahead as in the case of irrigation areas or bad terrain features such as complete lack of landing areas.

If the weather ahead blocks the progress of the flight, then, a climb to absolute maximum possible height is in order so there may be no great haste in leaving the top of the thermal and starting a final glide. If bad soaring weather is moving toward you then a rapid climb as high as possible should be made and the penetration into the poor weather for maximum distance should be begun as soon as possible. By penetration into bad weather we don't mean into cloud or into gusty surface winds that would make landing dangerous.

Let us repeat here, again, that this is a racing sport and all of these in-flight decisions will be based on how it will influence maximizing distance and minimizing time.

5.8 Climbing Technique Vs. Altitude

We assume that you have learned general climbing techniques in training and from practice. So it is in order now to make a few comments about how this climbing technique may vary with altitude.

In most instances the diameter of a thermal will increase with altitude. When you are low in the bottom portions of the thermal, it is usually necessary to fly at steeper angles of bank. For safety, of course, it will be necessary to increase the air speed at these greater angles of bank, especially at low altitudes. When the cores are small, it is quite common to use 45 to 60 degrees of bank to maximize the climb rate. Lest we give the wrong idea, we must emphasize quite strongly that you should always use the minimum angle of bank possible to stay in the core. The less the angle of bank, the more efficient the sailplane and the lower the stalling speed. The angle of bank may be quite shallow near the cloud base where the thermal diameter is larger.

Incidentally, here is a good place to reiterate the fact that you should not become left-handed or right-handed in soaring. All good soaring pilots are ambidextrous; that is to say, they can circle with equal case either to the right or to the left. If you are more one sided this way, then you should make special efforts to practice the other way. Your in-flight decision as to which way to turn upon entering the thermal should be dictated entirely by the direction that will more quickly center you in the core and yield the best climb rate.

5.9 Finding Lift

Unfortunately, many sailplane pilots seem to think that the best way to find lift is by radio (asking others). Believe us when we say that this is "Sunday afternoon around the airport" stuff. It is very, very rare indeed that the pilot soaring cross country is able to get any help on the radio. It is against the rules in contests and soaring for records, and there are few other times when this type of help is available. It is best just to forget about this form of radio aid.

Cumulus clouds are still the best overall soaring indicators. When you are high, that is, within a thousand or two feet of the cloud bases, then you can use the clouds more directly for finding lift. It is important to learn to recognize growing cumulus clouds, as opposed to decaying cumulus.

All soaring pilots have at one time or another been frustrated by flying to a beautiful-looking cloud only to have it decay and become useless upon their arrival. It always behooves a cross country soaring pilot to study the clouds, particularly their growth patterns. Cumulus clouds start with a wisp, and it is generally much better to go toward a beginning wisp in search of lift rather than toward the full grown cu. If you notice a big blue area ahead, then study this area very carefully for evidence of beginning of wisps. Blue holes are not always bad in soaring. If they contain any inkling of a wisp, then they probably won't remain blue holes long. They are actually areas which should attract you in your search for lift. The final stage of a decaying cu is also a wisp so you must be careful to go for the starting wisp and not the ending wisp!

Which side of the cloud to go to? Upwind? Downwind? Sunny side? The answers to these questions vary with many conditions, for example, the particular type of air mass, the season, the terrain, time of day, surface wind, etc. About the only thing that you can say for sure is that it won't always be the same each time. The best advice is to experiment. If you click once, then do the same thing or go to the same general area of the cloud again, and as long as you are successful, don't change your pattern. Most experienced pilots agree in general that you should try under the darkest area of the bottom of a cloud first.

Remember that thermals may slope considerably from the ground up to where they start to form the cloud. If you are very much below the cloud base, then it's quite reasonable to assume that the thermal may not be directly below the cloud, especially if the winds aloft are appreciable. Here, again, we must-conjure up a mental picture of where the thermal is with respect to the cloud, and as is so often the case in soaring, we continually adjust this mental picture till we find success. Since the thermal tends to slope downwind, then you should search upwind of the cloud if you are much below it.

Not all clouds are good for finding lift in cross country soaring. The sun must get through to heat the ground. Cumulus can overdevelop and shut out the sun. In searching for lift, even up high, study the ground. If the cloud shadows begin to cover too high a percentage of the ground-WATCH OUT! High cirrus clouds can thicken seemingly without warning and shut out the sun. Keep an eye out for this condition in your search for lift.

Another common means for finding lift is the utilization of other sailplanes. Most championship pilots say emphatically that gaggles are bad. A gaggle is defined as a group of sailplanes in one thermal. For the less experienced cross country pilot, we would suggest that gaggles are not always bad but should be used with discretion. If you are in search of lift and see a high performance sailplane ahead making tight circles with a steep angle of bank, you can bet that he probably has a good core centered and there is no reason whatsoever that you should not share his good fortune, particularly if you know and respect the pilot. It is a well-known fact in competition circles that most pilots memorize and some actually make lists of the most competent pilots and their ship numbers so they will know which ships to follow. I think that we are making the point quite obvious when we say that if you, while soaring cross country, should come across a ship with a large number 2 or with XX on the tail, then it would be a good idea to watch it closely. Chances are he will show you some lift. In case you didn't recognize these championship numbers, they belong to America's two World Champion pilots A. J. Smith and George Moffat, respectively.

Other sailplanes can be especially helpful on a blue day with no clouds. A good trick utilized by many pilots is to follow along behind and several span widths to the side of a good ship and watch when he bobs up (an indication that he is slowing down in lift). When he does, then you move over and fly through the same good air that he has just been through. When he bobs down, indicating that he is going through bad air, then you move farther out and avoid this down area.

Pilots often discuss in detail the different aspects of team flying when looking for ways to improve their cross country soaring performance. The more experienced pilots generally agree that team flying is extremely tricky and will usually slow one of the participants down considerably.

This is not to say that it hasn't been utilized effectively at times, but it requires a great amount of experience and practice and, of course, identical equipment.

We have spent the last few paragraphs discussing how to find lift when you are up high. In these cases there is less anxiety in finding lift. Now let's discuss some aspects of finding lift when you are low. It is an understatement to say that soaring does have its anxious moments. There is no time more anxious than when you are down low and need to find lift badly to prevent a landing. As you sink from the middle altitudes to the lower altitudes, anxiety has a way of increasing exponentially. When you have trained yourself properly and have gained some experience, you can think more intelligently during this time of utmost stress.

The lower you drop away from cloud base, the less help clouds will be in finding lift. Cloud areas in general are still a good idea but, again, it should be remembered that thermals bend downwind and, therefore, you should generally look upwind from the clouds. As you drop from the middle altitudes, you should realize that generally high ground is better for thermal sources. When low, finding lift is a matter of identifying and utilizing thermal sources. Usually forest areas, woods, lakes, and such are not the best sources. Plowed areas, cultivated fields, and big paved areas are generally better. Towns or other areas that may have absorbed a lot of heat during the day are particularly good later in the afternoon. Big airport runways and interstate highways can be good sources. Oftentimes it takes a disturbance in an area where a good source may exist to trigger the thermal. For example, a truck on a superhighway can oftentimes kick off an excellent thermal.

Always watch for leaves rustling, which can be seen easily because the backs of the leaves appear a much lighter color; and when the leaves are blown, you can see color changes in the trees. Grain or tall grass waving in a swirl in a cultivated field is an indication that a thermal is coming up from that spot. Small dust or trash devils, even in the Eastern United States, are not uncommon and should be watched for.

The sunny side of hills and ridges are good thermal sources. Any terrain that catches the direct rays of the sun is likely to be better. It's better to stay on the upwind side when at or about ridge height level. Ridge lift is always a good possibility and has saved many a flight. If you have a ridge near your airport, it is excellent experience to practice ridge soaring. If there is a soaring site with a ridge anywhere close to your area, it is worth the trip just to get ridge soaring experience.

Circling birds can be helpful in locating lift. Don't, however, assume that all birds are brilliant or that they are climbing. They do sometimes circle in sink! They will suck you into the sink with them if you let them. Take care. However, if you are low and desperate, a hawk or a buzzard is a very good gamble. Remember that they can circle in a much smaller thermal than you, and you may not be able to stay with them down low. Soaring birds such as hawks and turkey buzzards have about the same sink rate and L/D at about 50 mph as a 1-34 or maybe a 1-26. They are, of course, more maneuverable and may be able to out climb you. Any of the new glass ships can leave them at above about 50 or 60 mph when penetrating, in spite of their variable geometry wings. Most birds do not usually attack a sailplane unless it is close to their nest or in their restricted territory (e.g., eagles). The study of the relationship between birds and soaring is much too broad a subject to cover here. We suggest you go to other references for more details of this fascinating subject.

Smoke is a soaring pilot's friend (assuming it's outside the cockpit). Always watch for smoke when you are in the middle altitudes and on the way down. This is for two reasons: Smoke is the best surface wind indicator and also represents a likely thermal source. Polluters of the atmosphere have at least one friend, the soaring pilot. Be on the lookout for smoke stacks and don't be afraid to thermal with your wing pointing right in the stack. However, you should be very conscious of the danger of fumes. These can be of any sort and can quite possibly be toxic. It is a good idea for a soaring pilot, when making a save over a smoke stack, to don his oxygen mask for a few minutes when circling in the smoke. Any time you don't feel well when circling in smoke, get out fast even if it means a landing. The toxic effect of industrial smoke can be a real danger.

Other types of smoke sources such as trash fires, brush fires, or forest fires should be watched, for and utilized when possible.

Before we end this section a few general comments about flying low should be emphasized. Soaring is nice when you are high. The temperature is much lower, you are more comfortable, less anxious, etc. But when you get low, the temperature is much higher and just when the time arises that you should be able to concentrate most efficiently, you will be most uncomfortable and anxious. It all adds up to the fact that one is in a less safe condition when flying low. Therefore, a good pilot forces himself to be more conservative and more careful under these conditions. In summary: The number one consideration, when down low, is landing safety; and locating lift is a poor second.

5.10 How Fast?

Another important in-flight decision which causes a great amount of difficulty and even more discussion is how fast to fly between thermals. A whole science has grown up around this subject and many theories are set forth from which the pilot may choose. Most theories point toward determining an optimum speed for maximizing overall cross country speed. These are generally based on assumptions of the ratio of up air to down air and are presented as speed to fly vs. variometer reading, assuming that conditions ahead will be the same as those just encountered. For the serious pilot who is interested in the details and derivations of these theories, we will give a few references here for your further study:

1. Articles by Dick Johnson and Wil Schuemann in the Proceedings of the 1972 Symposium on Competitive Soaring, Soaring Symposia 1973.

2. Chapter 3 in New Soaring Pilot by Ann Welch, Lorne Welch and Frank Irving, John Murray Publisher, 1968.

3. Article by Paul McCready in Soaring Magazine, January-February 1958.

4. Article by Weinberg in Soaring Magazine, June, 1967, page 20.

5. Chapter 3 in 7he Theory of Modern Cross Country Gliding by Weinholtz, translation published in New Zealand, 1969.

6. Chapter 6 in American Soaring Handbook by Dick Johnson, published by SSA.

7. Chapter 28 in Gliding by Derek Piggott, Adam & Charles Black Publishers, London, 1958.

How much of the detail in these references should the average non-technical cross country soaring pilot try to absorb and utilize? We feel that the serious pilot should be familiar with the McCready speed ring and if you cannot buy one for your sailplane-variometer combination, you should at least study the article by McCready or one of the other references fully enough to be able to construct a ring or table by yourself, or with the help of a technically minded friend.

The speed-to-fly ring on your variometer is a great inflight decision maker. You must make the decision as to how conservatively or how optimistically to set the ring, but once it is set the ring makes the speed-to-fly decision for you. Even a ring that may not fit the polar of the sailplane exactly is better than no ring at all. just to indicate to you that our opinions are not unanimous, some of America's top soaring pilots do not even use a speed-to-fly ring. Dick Schreder, for example (who incidentally is a many-time U.S. National Champion), uses no ring but suggests a rather simple rule of thumb which you might like to consider. He says, "Fly with your variometer at a down setting equal to your last average climb rate." This means that you should adjust your speed so that the vario reads down to the same magnitude as its average up reading was during the last climb. If you leave a 300 ft./min. thermal, then adjust your speed so that, your variometer reads 300 ft./min down on the average. Another easy rule for pilots who fly club, rental, or other less sophisticatedly instrumented ships is to increase your speed to an average of about 20 percent greater than the best L/D speed. Faster than this would be called for in good conditions and slower in poor conditions.

Regardless of which rule or ring you use, your in-flight decisions on speed should be tempered with good judgment, and in all cases you should speed up in sink and slow down in lift. This last statement sounds very simple, but it is one of the most difficult things for a new cross country pilot to learn. It is not so hard to slow up in lift, but forcing yourself to speed up in sink is difficult. This is necessary so that you decrease the amount of time you spend in bad air and increase the amount of time you spend in good air. This rule applies regardless of altitude; however, your average speed between thermals should be reduced with lower altitude.

When you reach an altitude where it is obvious you should accept any lift to prevent landing, your average speed should be reduced to best L/D speed to enable you to search the greatest area for lift. The whole game here is to increase the probability of finding lift. If this is not already an automatic reaction with you while soaring, then by all means remember this very important soaring axiom: SPEED UP IN SINK-SLOW DOWN IN LIFT!

5.11 Entering, Centering, And Leaving

It is not our intention here to go through a detailed analysis and procedure of exactly how a thermal should be flown. Most of the references listed in the previous section have chapters devoted to this subject. We don't hold much to the idea of memorizing rote procedures for centering in lift. Our discussion here will be more on basic philosophy, a few pertinent comments thereon, and a few hints which relate this subject to the aspects of cross country soaring.

Our philosophy is simple. First: Forget all the rote theories and procedures you have read about and think in terms of your mental picture of the size, shape, and location of the thermal and your position and heading in reference to this mental picture. We now assume that your manipulations of the controls are automatic and that you can keep the yaw string in the center without continual concentration. The only thing left for you to concentrate on is taking the feedback information that you get from looking outside and listening to your vario and using this information to vary your mental picture. You should update this mental picture all the time as to thermal size, shape, and location while varying your circle (position and heading) to coincide with it.

A few points of emphasis are in order. Never assume that the cross section of the thermal is circular or that its diameter is the same as the last one in which you flew. Another very, very common mistake in centering thermals is flying through the same bad air twice. Experienced pilots never cease to be amazed when beginners persist in doing this. It should be considered an unforgivable sin in soaring. To make the point even more strongly, we feel that each soaring pilot should be forced, at gun point, to sign a sworn statement saying that he hereby swears that he will never, ever, fly through the same bad air twice. Of course, if you are continually updating your mental picture as you should, you will have shifted your circle so that this would not ever happen to you. It is forgivable to fly through new bad air after revising your circle, but this soaring axiom is worth tattooing on some visible part of your body . . . NEVER FLY THROUGH THE SAME BAD AIR TWICE! A corollary to this might be that you should always fly through really good air as many times as possible and your changing mental picture should help you to do this.

Thermals may be oblong. There may be two or more cores in close proximity and you should keep an open mind as to strange shapes. Lift is where you find it. Lift may be in long continuous lines and you may not need to circle to climb. This may be due to cloud streets (with or without the clouds), waves, ridge lift, etc.

If you are circling with another sailplane in the same thermal at the same altitude, watching him is often better than watching your vario. Of course, it is better if you are listening to your audio vario while you are watching him. Feedback from what is happening to his ship win help you to adjust 'your mental picture. It is quite noticeable, by watching him, when the "down" side of his (and your) circle occurs and when the "up" side occurs. This is valuable information to utilize.

Before leaving this topic, a word or two about entering and leaving thermals is in order. The answers were surprising to many pilots when the question of entrance procedure into a thermal was discussed at a symposium on competition soaring by several of the world's top soaring pilots. It was found that they each do it somewhat differently.

First we state the problem: You are penetrating at inter thermal speed between thermals and you make the in-flight decision that you are at an altitude at which you feel you should take the next good thermal and climb back. What is your exact procedure? Do you slow down to thermaling speed at the first hint of lift on the vario? Do you fly all the way through the thermal and identify it before slowing down then turn around and come back and find it? Most of the more experienced pilots do not do much slowing down until they are sure that they are well into the core of the thermal.

Often there is heavy sink near the edges of a core and you want to keep your speed up through such areas. The direction you turn should not be determined until this time and the decision of which direction will be dependent upon which wing is kicked up the most or any other such evidence that makes you feel the thermal will be stronger one way or the other. The next step is a beautiful chandelle one way or the other and after one-half, or at most, one full turn, you should be stabilized at your thermaling speed in the proper configuration (flaps down perhaps) and exactly in the core. This little maneuver sounds easy; and if properly done, is one of the most exhilarating happenings in soaring. If you miss the core, and, believe me, we all do more than we like to admit, you will make the chandelle and slow down and watch to your horror as the vario sinks to the down side. Of the many frustrating experiences in soaring, this rates near the top and is unfortunately one of the most common and aggravating.

Perfecting this entering maneuver takes practice, practice, practice. It is difficult or impossible to consistently do this correctly without a well compensated total energy variometer system. Otherwise, the instant you begin to slow down, the vario will be lying to you. The absolute necessity for a well compensated system will be emphasized in later chapters. If you miss on the entering chandelle maneuver and find yourself at thermaling speed in sink, then you are faced with another of soaring's more agonizing decisions. What do you do now? Do you make another circle with a variation in the direction your mental picture tens you the thermal may be, or do you give up and drop the nose again and move on for a fresh try at a new thermal, having written off the valuable seconds that the frustrating sink circle has cost you? We wish we had some good specific advice to give for this common predicament. This is one of the places where soaring judgment built by experience must dictate your decision. We can add, however, that here is a good place to remember not to fly through the same bad air twice.

Leaving a thermal is usually not so difficult if the thermal is good, as it is likely to be when you have climbed up to where you are ready to leave, assuming that you have established yourself quite well in the core and are able to stay there. When you have decided to leave, first check for other ships at your altitude then make another circle during which time you build up your speed from thermaling speed to your inter thermal speed or higher, and then when you are heading away from the direction which you want to go, tighten up your turn and cut back across the center of the thermal as you roll out on the departure heading, then leave the center of the thermal at your inter thermal speed or higher. This is really a delightful maneuver and does not involve much of an in-flight decision once you have decided when to leave.

A much more common case of leaving a thermal is when the thermal seems to die out before you arc as high as you feel you should be or if the thermal weakens appreciably for some unknown reason (which we all know is not infrequent!). In this case, the important in-flight decision is whether to try another circle with a variation or to move on. Unfortunately, there is no pat answer here either. This depends on the confidence you have in your mental picture of where the lift or core is. You will find many times that the lift defies figuring out and it is practically impossible to form an intelligent mental picture. Here again, your judgment and experience are the only things upon which you can rely in deciding to stay or to go. The higher you are, the more the tendency to go. The lower you are, the more the tendency should be to stay. One thing is for sure here. NEVER FLY THROUGH THE SAME BAD AIR TWICE!

5.12 Gaggles

We will end this chapter with some additional comments about gaggles. We mentioned gaggles previously in relationship to finding lift, but here we would like to discuss some in-flight decision aspects of the actual flying techniques in gaggles.

It is not bad to fly with another sailplane at the same altitude in the same thermal, especially if you have an audio vario, but when you are at the same altitude in a thermal with three or more ships it is not only potentially dangerous, but you will not be doing your most efficient job of climbing. This is because your safety decisions dominate and you must keep track of every other sailplane at your altitude. Therefore, it is not good to fly in crowded gaggles if there is any other alternative. If you know and trust the other pilots, it is somewhat safer, but regardless of how well you know and respect the pilots, you should never let them out of your sight and never for one instant assume that they see you.

It goes without saying that it is unthinkable to fly extremely close to another aircraft if:

1. You are very low, say below 1000 feet, or

2. If you are not wearing a parachute.

Don't mix it up close unless you KNOW you can handle your ship perfectly at low speeds. Beginners often spend too much time staring at the vario rather than looking out. If there is any question in your mind about whether or not you have this habit, then make certain you break it before you fly in gaggles.

In overall summary it should be emphasized that the priority for in-flight decisions is unquestionably safety first. Maximizing speed and distance is an important but relatively poor second!

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