The forecast shows the expected base of the cumulus at 11,000 MSL, and the winds aloft indicate 320° at 10 knots at 9,000
MSL and 330° at 20 knots at 12,000 MSL during the flight. The pilot should take note of the winds aloft for reference during
the flight. For instance, the first leg has an almost direct crosswind from the left; the second leg has a weaker crosswind
component from the right; the final leg has an almost direct headwind. For this reason, the glider pilot may decide to fly the
course in the opposite direction. In this example however, the pilot accepts a headwind on the final leg. The forecast shows
the expected base of the cumulus at 11,000 MSL, and the winds aloft indicate 320° at 10 knots at 9,000 MSL and 330° at
20 knots at 12,000 MSL during the flight. The pilot should take note of the winds aloft for reference during the flight. For
instance, the first leg has an almost direct crosswind from the left; the second leg has a weaker crosswind component from
the right; the final leg has an almost direct headwind. For this reason, the glider pilot may decide to fly the course in the
opposite direction. In this example however, the pilot accepts a headwind on the final leg.
During preflight preparation, the pilot should study the course line along each leg for expected landmarks and possible
alternate landing sites. For instance, the first leg follows highway and parallels railroad tracks for several miles before the
highway turns north just due south of Clovis. The town of Clovis should become obvious on the left. Note the Class D
airspace around Cannon Air Force Base (CVS) just west of Clovis. If better soaring conditions exist north of course track
and with the northwesterly wind, the glider might cross the path of aircraft on a long final approach to the northwest-
southeast runway at the air base. Knowing the courses and the approximate heading for each leg helps keep the pilot from
getting lost even when making deviations toward the best lift. During the flight, if the sky ahead shows several equally
promising cumulus clouds, choosing the one closest to the course line keeps the flight distance to a minimum and makes
the most sense.
The pilot should see the Clovis airport (CVN) next and check for traffic operating in and out of the airport. After Clovis,
the towns of Bovina and Friona can serve as landmarks for the flight. The Texico (TXO) VOR, a VHF Omnidirectional
Range station near Bovina serves as approach aid to the Clovis airport, and the pilot should remain alert for more powered
aircraft traffic as a result.
The pilot can locate the first turn point easily because of good landmarks, including Benger Airport (X54). [ Figure 11-7]
The second leg has fewer landmarks. After about 25 miles, the town of Muleshoe and the Muleshoe airport (2T1) should
appear. (See Figure 11-6). The town should appear on the right and the airport on the left of the intended course.
Figure 11-7. TEXICO VOR and Benger Airport (X54).
Next, the course enters the Bronco 1 Military Operations Area (MOA). The dimensions of the MOA appear on the sectional
chart, and the pilot should determine the active times of this airspace. Approaching the second turn point, the pilot could
confuse the towns of Circle Back and Needmore. [ Figure 11-6] The relative position of an obstruction 466 feet above
ground level (AGL) and a road that heads north out of Needmore provide clues for identification. Landmarks on the third
leg [Figure 11-8] include power transmission lines, Salt Lake (possibly dry), the small town of Arch, and a major road
coming south out of Portales.
Figure 11-8. Circle Back and Needmore.
The flight can begin after a final check of the weather, a thorough preflight of the glider, and after stowing all the appropriate
equipment. Once in the air and on course, the pilot can try to verify the winds aloft while using pilotage to remain as close
to the course line as soaring conditions permit. If making course deviations, the pilot should remain aware of the location of
the course line to the next turning point. For example, a Cu directly ahead may indicate lift, but one 30° off course indicates
possibly even more lift. The pilot chooses whether to proceed toward the larger lift while accepting a longer distance to fly,
or to accept lesser lift with a smaller off-course deviation.
Sometimes a pilot determines an approximate course while in the air. Assume a few miles before reaching the town of
Muleshoe, on the second leg, the weather ahead has deteriorated—a shower developed at the final turn point (Circle Back).
Rather than continuing, the pilot can cut the triangle short and return directly to Portales. The pilot determines that Portales
is about 37 miles away on an estimated heading of about 240° true or about 231° magnetic after accounting for magnetic
variation. The pilot adjusts for the northwesterly wind at almost 90° across the new course and uses a 10° or 20° crab to the
right, allowing for some drift in thermal climbs. With practice, a pilot can manage an inflight course change with relative
ease.
The sky towards Portales indicates favorable lift conditions. However, the area along the new course includes sand hills, an
area that may not have good choices for off-field landings. The pilot decides to take time to gain altitude in thermals until
beyond this point and until within gliding distance of suitable landing sites.
Navigation Using GPS
A GPS system makes navigation easier. A GPS unit displays distance and heading to a specified point, usually found by
scrolling through an internal database of waypoints. Many GPS units also continuously calculate and display ground speed.
Given TAS information, the GPS can calculate the headwind component.
When using a GPS unit, the pilot should continue focusing on flying the glider, finding lift, and scanning for traffic. Like
any electronic instrument, a GPS unit can fail, and the pilot should have a backup system.
Cross-Country Techniques
For safe cross-country soaring, the pilot should always stay within glide range of a suitable landing area. The landing area
may be an airport or other suitable spot to land out. If following this practice, even with high sink rates between thermals,
the pilot should never need a thermal to obtain the range to a suitable landing area.
Before venturing beyond gliding distance from the home airport, the pilot can practice thermalling and cross- country
techniques using small triangles or other short courses. Figure 11-9 shows three examples. The length of each leg, typically
between 5 and 10 miles, depends on the performance of the glider. The pilot does not need excellent soaring conditions to
fly these short courses, but conditions should not make it difficult to stay aloft. On a good day, the pilot can fly the short-
course pattern more than once and can also practice switching communication frequencies and listening to transmissions
from aircraft or controllers at nearby airports. While progressing along each leg of the triangle, the pilot should frequently
cross check the altitude needed to return to the home airport and abandon the course if needed. Setting a minimum altitude
for arrival at the home site of 1,500 or 2,000 feet AGL adds a margin of safety. The pilot should make every landing at the
conclusion of a soaring flight an accuracy landing to keep the pilot’s attention focused until the conclusion of the flight.
5 NM
5 NM5 NM
4 NM
7 NM
8 NM
5 NM
10 NM
10 NM
10 NM
Figure 11-9. Examples of practice cross-country courses.
Some flight computers automatically calculate the winds aloft while other GPS systems estimate winds by calculating
the drift after several thermal turns. When flying with GPS, the pilot can determine a headwind component from TAS by
simple subtraction of groundspeed while maintaining a particular heading. Determining winds aloft without either system
can prove difficult. A first estimate comes from winds aloft forecasts. Once aloft, the pilot can estimate windspeed at cloud
level from the track of cumulus shadows over the ground. However, the winds at lower levels can differ from those at cloud
level. On cloudless days, the pilot can estimate wind by noting drift while thermalling. If losing more height on glides than
expected, the pilot should increase the headwind estimate.
A common flight planning technique involves drawing 5 and 10 nautical mile radius circles around alternate landing sites
along the planned route. This helps the pilot visualize the altitude needed to safely reach an alternate site should thermal
activity be insufficient to continue the cross-country. Alternatively, a pilot using a glide calculator or computerized tool
can quickly determine the altitude needed to glide a specific distance. For instance, while on a cross-country flight and
over a good landing spot, the next good landing site appears 12 miles distant into a 10-knot headwind. [ Figure 11-10] A
glide calculation shows that the glider will lose 3,200 feet during the glide, and the pilot should add at least 1,500 feet to
allow for setting up for a landing, which makes the total altitude needed to make the glide as 4,700 feet. While not high
enough to accomplish the 12-mile glide, the 3,800 current foot altitude allows the pilot to start along the course provided
the pilot remains within gliding distance of the landing spot where the glide began. After two miles with no lift, the glider
has descended to an altitude of almost 3,300 feet. While not high enough to glide the remaining 10 miles, the pilot can still
glide back to the landing site two miles behind. After almost 4 miles, the pilot encounters a 4-knot thermal at about 2,700
feet and climbs to 4,300 feet.
Feet AGL
NM
0 1 2 3 4 5 6 7 8 9 10 11 12
6,000
5,500
5,000
4,500
4,000
3,500
3,000
2,500
2,000
Wind 10 kt
Flight profile
Effective glide ratio
4,300 feet
2,700 feet
1,500 feet AGL
3,800
4,700
Figure 11-10. Example of a flight profile during a cross-country course.
The glide calculator or computer accounts for the glider’s calm air rate of descent, which the pilot can adjust for headwinds
and tailwinds. However, any vertical currents (sink) can drastically affect these calculations and distort the results. Areas
of good thermal lift exist with areas of strong sink, and a glider pilot should read the sky to find the lift and avoid or pass
through the sink as quickly as possible. A competent glider pilot understands the polar curves of the glider and the effects
of different conditions of lift, sink, and winds.
During the climb in the example above, the downwind drift of the thermal moves the glider back approximately a half mile.
The pilot would like to glide almost 9 miles to the next landing spot, and a check of the glide calculator indicates 2,400
feet needed plus 1,500 feet at the destination, for a total of 3,900 feet. The pilot has 400 feet above the altitude needed
for the glide with a margin to plan the landing. In the previous example, had the thermal topped at 3,600 feet (instead of
4,300 feet) the pilot could continue on course in hopes of finding more lift before needing to turn downwind and back to
the previous landing spot. Any cross-country soaring flight involves dozens of decisions and calculations such as this. In
addition, a pilot should plan for increasing the altitude safety margin if conditions might cause a lower effective glide ratio.
For example, other pilots reporting heavy sink along the intended course would alert a pilot to increase the safety margin.
On any soaring flight, a critical altitude exists where a decision must be made to cease attempts to work thermals and
commit to a landing. Cross-country flights can have landings in unfamiliar places and feature additional pressures like
those discussed in Chapter 8, Abnormal and Emergency Procedures. In the event not reaching a planned landing site, a
reasonable procedure involves choosing a general area by 2,000 feet AGL, picking a landing site by 1,500 feet AGL, and
committing to landing by 1,000 feet AGL. The exact altitude where the thought processes should shift from soaring to
landing preparation depends on the terrain. In areas where numerous fields suitable for landing may exist, the pilot can
delay field selection to a lower altitude. In areas with landing sites spaced by 30 miles or more apart, the pilot’s focus on
committing to a landing spot should begin at much higher altitudes above the ground.
Attempts to thermal in the pattern may lead to a stall or spin accident. Therefore, once committed in the pattern, the pilot
should not try thermalling. When over a safe landing spot, the pilot should perform the prelanding checklist.
A common first cross-country flight consists of a 50-kilometer (32 statute miles) straight distance flight with a landing
at another field. The pilot can fly this distance at a leisurely pace on an average soaring day. The pilot should review
the planned course carefully, research all available landing areas along the way, arrive early, and complete all preflight
preparations. Once airborne, the pilot should take time to get a feel for the day’s thermals. If the day looks good enough
and the glider gains adequate altitude, the pilot can set off on course.
Pilots gain cross-country skills through practice but should also continue to review theory while gaining that experience.
A theory or technique that initially made little sense takes on a lot more significance after several cross-country flights.
Postflight self-critique, which can occur at any time before the next flight, also improves pilot skills.
Soaring Faster & Farther
An average cross-country speed of 20 or 30 miles per hour (mph) seems adequate for a 32-mile flight, but that average
speed does not accommodate longer flights. Flying at higher average cross-country speeds allows for increased soaring
flight distance.
In the context of cross-country soaring, flying faster means achieving a faster average groundspeed. The secret to faster
cross-country flight lies in spending less time climbing and more time gliding. This occurs when using better thermals and
spending more time in lifting air and less time in sinking air. MacCready ring theory and/or speed-to-fly theory determines
the optimum speeds between thermals. Proper use of the MacCready speed ring or equivalent electronic speed director
displays the appropriate speed.
Height Bands
On most soaring days an altitude range called a height band describes where maximum thermal strength exists. Height
bands give the optimum altitude range in which to climb and glide on a given day. For instance, a thermal may have 200
to 300 fpm lift between 3,000 and 5,000 feet AGL which then weakens before topping out at 6,000 feet AGL. In this case,
a 2,000-foot height band exists between 3,000 feet and 5,000 feet AGL. Staying within the height band gives the best
(fastest) climbs. On a long cross-country flight, the pilot should thermal while within the height band and avoid stopping
for weak thermals unless needing additional altitude at that moment.
On another day, thermals may be strong from 1,000 feet to 6,000 feet AGL before weakening, which would suggest a
height band 5,000 feet deep. In this case, however, depending on the thermal spacing, terrain, pilot experience level, and
other factors, a height band would run from 2,000 feet or 3,000 feet up to 6,000 feet AGL. Pilots should avoid gliding to
the lower bounds of strong thermals (1,000 feet AGL) since the thermal could dissipate and commit the pilot to a poorly
planned landing. [Figure 11-10]
Altitude (feet AGL)
Thermal strength (fpm)
0 100 200 300 400 500 600 700 800
6,000
5,000
4,000
3,000
2,000
Height
Band
Figure 11-11. Example of the height band.
Note: METARs give cloud levels as AGL, while PIREPS report clouds using MSL. Graphical Area Forecasts (GFA)
give clouds as MSL. Pilots should interpret the reported cloud heights with care. This interpretation takes on added
significance when glider pilots travel to higher elevation airports and subtract field elevation from MSL reports to ensure
cloud clearances.
Determining the top of the height band depends upon personal preference and experience, but a rule of thumb puts the top
at an altitude where thermals drop off to 75 percent of the best achieved climb. A pilot who finds 400 fpm as the maximum
thermal strength in the height band might leave when thermals decrease to 300 fpm for more than a turn or two. Pilots
can also compare the current climb with average climb achieved to determine the height band top. If the climb falls to 75
percent or less of the average climb, the pilot should consider leaving the thermal. Many electronic variometers have an
average function that displays average climb over specific time intervals. Another technique involves simply timing the
altitude gained over 30 seconds or 1 minute.
Theoretically, the pilot can achieve the highest average speed on a cross-country flight when setting the MacCready ring,
if available, for the rate of climb within the height band. To do this, the pilot rotates the ring so that the index mark lines up
with the rate of climb (for instance, 400 fpm) rather than at zero (the setting used for maximum distance). [ Figure 11-12]
This setting optimizes the time distribution between climbing and gliding. If flying slower than the MacCready setting,
the pilot consumes more time between thermals than can be saved during shorter time in strong thermals. If flying faster
than the MacCready setting, the pilot loses too much altitude between thermals and uses more than the optimum amount
of time to regain the altitude.
Figure 11-12. A MacCready Ring set for an expected 4 knot climb in the next thermal. With current sink of a little over 2 knots, the
MacCready ring suggests 65 knots as the speed to the next thermal.
MacCready ring theory assumes that the next thermal has at least the same strength as that set on the ring, and the glider can
reach the next thermal with sufficient altitude. The pilot should judge whether actual conditions support adherence to the
numbers. Factors that may require departure from the MacCready ring theory include terrain (extra height needed to clear
a ridge), distance to the next suitable landing spot, or deteriorating soaring conditions ahead. If the next thermal appears to
be out of reach before dropping below the height band, the pilot should climb higher, glide more slowly, or both.
To illustrate the use of speed-to-fly theory, assume there are four gliders at the same height. The scenario includes three
weak cumulus clouds each produced by 200-fpm thermals followed by a larger cumulus with 600 fpm thermals under it,
illustrated in Figure 11-13.
Figure 11-13. Example of glides achieved for different MacCready ring settings.