• Pilot 1 sets the ring to 6 knots for the anticipated strong climb under the large cumulus, but the aggressive approach
has the glider on the ground before reaching the cloud.
• Pilot 2 sets the ring for 2 knots and climbs under each cloud until resetting the ring to 6 knots after climbing under
the third weak cumulus, in accordance with strict speed-to-fly theory.
• Pilot 3 is conservative and sets the ring to zero for the maximum glide.
• Pilot 4 calculates the altitude needed to glide to the large cumulus using an intermediate setting of 3 knots and finds
the glider can glide to the cloud and still be within the height band.
By the time pilot 4 climbs under the large cumulus, the pilot sits well ahead of pilots 2 and 3 and can relay retrieval
instructions for pilot 1. This example illustrates the science and art of faster cross-country soaring. The science comes from
speed-to-fly theory, while the art involves interpreting and modifying the theory for the actual conditions.
Tips & Techniques
The height band changes during the day. On a typical soaring day, thermal height and strength often increase rapidly during
late morning, and then both the strength and height remain somewhat steady for several hours during the afternoon. The
height band rises and broadens with overall thermal height. Sometimes a base of cumulus clouds limits the top of the height
band. The cloud base may slowly increase by thousands of feet over several hours, during which time the height band also
increases. Pilots should stop traveling and thermal when at or near the bottom of the height band. Pushing too hard for
distance can lead to an early off-field landing or lead to lost time spent climbing inefficiently at lower altitudes. Thermals
often “shut off” rapidly late in the day, and pilots should consider staying higher late in the day. [Figure 11-14]
Altitude (feet)
Time of day (military)
10 11 12 13 14 15 16 17 18
8,000
7,000
6,000
5,000
4,000
3,000
2,000
Thermal strength
Height band
Figure 11-14. Thermal height and height band versus time of day.
Another way to increase cross-country speed involves a technique known as “dolphin flight,” which covers surprising
distances with little to no turning or circling. The idea involves diving to speed up while in sink and slowing down and
climbing in lift while maintaining a straight course line. This technique utilizes closely spaced thermals, as occur along a
cloud street. The speed to fly between lift areas depends on the appropriate MacCready setting.
As an example, assume two gliders start at the same point and fly under a cloud street with frequent thermals with weak
sink between the thermals. Glider 1 uses “dolphin flight” by flying faster in the sink and slower in lift. Glider 2 conserves
altitude and stays close to the cloud base by flying best L/D through weak sink. To get to the next cloud, the pilot of glider
2 flies faster in areas of lift. At the end of the cloud street, one good climb quickly puts glider 1 near the cloud base and well
ahead of glider 2. [Figure 11-15] The best-speed-to-fly decreases time in sink and therefore decreases the overall amount
of descent but produces the best forward progress. Being slower in sink increases time descending and slows forward
progress. Being fast in lift decreases time in lift and altitude gained.
Fast flight Slow flight
Glider Using dolphin flight, achieves a greater distance
Glider Straight high-speed glide achieves less distance
Figure 11-15. Advantage of proper speed to fly under a cloud street.
On an actual cross-country flight, the pilot can use a combination of dolphin flight and classic climb and glide. In the
example above the pilots decided not to stop and circle in the weak closely spaced thermals, but they could stop and circle
if finding areas of strong lift.
Special Situations
Course Deviations
Pilots might consider deviation on a soaring cross-country flight as the norm rather than the exception. Even with fair
weather cumulus evenly spaced across all quadrants, the pilot might decide to deviate toward stronger lift. Deviations of
10° or less add little to the total distance and pilots should not hesitate to fly toward such better lift. Even deviations up to
30° may work well if they lead toward better lift or avoid suspected sink ahead. The sooner the deviation starts, the less
extra distance the glider will cover during the deviation. [Figure 11-16]
1 2 3 4
A A A A
B B B B
C C
D or extra distance
1. Visualization of increase in
distance
2. Comparison: increase
caused by same-size
detour closer to goal
3. Unnecessarily large
increase by returning to
original course too soon
4. Unnecessarily large
increase by recognizing
need for detour too late
Distance increase caused by
detours (A straight line from A
to B equals the direct course.
= increase)
- Course distance
- Total flight distance
- Extra distance flown
(A2 + B2 = C2 to calculate
distance as the navigation
triangle develops with the
deviation distance)
Figure 11-16. Effects of starting course deviations at different times. Red arrows show extra course distance and indicate the benefit of
early course deviations.
The pilot might use deviations of 45° or even 90° to avoid poor conditions ahead. Areas to avoid could include a large
cloudless area or a shaded area where cumulus have spread out into stratus clouds. Cloud development can shade the earth,
decrease surface heating, and decrease lift. A pilot could deviate more than 90° to return to active thermals after venturing
into stable air.
Generally, glider pilots encountering a large area of stable air or sinking air will end up landing before VFR conditions
disappear. Thermalling ceases as the sky becomes cloudy and shades the earth’s surface. However, pilots should deviate
or have an option for landing rather than fly into lowering ceilings or rain showers ahead. Ridge lift might remain, but
cloud bases can obscure that source of lift as well. Thunderstorms along the course can generate outflows and affect
surface winds for many miles surrounding the storm. The pilot should avoid landing anywhere near a thunderstorm.
Thunderstorms ahead often warrant large course deviations of up to 180° (i.e., retreat to safety).
Lost Procedures
A working GPS system makes it almost impossible to get lost. However, GPS systems can fail, and pilots should have a
backup plan if that should occur. The following actions increase the likelihood of reorientation without using GPS.
If lost after some initial searching, the pilot should remain calm and make certain a suitable landing area exists within
gliding distance. The pilot should then try to find a source of lift and climb. Even weak lift can provide more time to
look for landmarks. Thermalling and climbing while searching has the added advantage of allowing a wider area to scan
while circling. The pilot should estimate the last known position, the course flown, and any possible differences in wind
at altitude. Maybe the headwind was stronger than anticipated, and the flight did not progress as far along the course as
expected. The pilot can try to pinpoint the present position from an estimate of the distance traveled for a given time from
a known point and confirm it with visible landmarks on an electronic or paper chart.
Once locating a known landmark on the chart and on the ground, the pilot can confirm the location by finding a few other
nearby landmarks. For instance, if seeing a specific town below, an adjacent highway should curve like the one shown on
the chart. Airports and airport runways provide valuable clues if sighting an airport, which include runway orientation and
markings or the location of a town or a city relative to the airport. If still lost and near a suitable landing area, the pilot
should stay in that area until certain of the location. If previous efforts fail, a radio call to other soaring pilots in the area
with a description of what lies below and nearby may bring help from another pilot. Finally, a safe landing provides the
opportunity to figure out the location on the ground.
Cross-Country Flight in a Self-Launching Glider
Although more complex and expensive, a self-launching glider can give the pilot additional freedom. First, a self- launching
glider allows the pilot to fly from airports without a towplane or tow pilot. Second, the pilot can use the engine to avoid
off-field landings and extend the flight. In theory, when low in a self-launching glider, the pilot simply starts the engine and
climbs to the next source of lift. However, this practice has risks of its own and has led to many accidents due to engine
failure or improper starting procedures.
Overreliance on the engine can lead pilots to glide over terrain unsuitable for landing. If the engine fails, the pilot has no
safe place to land. Some accidents have occurred when the pilot rushed to avoid a landing and forgot a critical task, such
as switching the ignition on. Other accidents have occurred in which the engine did not start immediately, and the pilot
flew too far from a suitable landing area while trying to troubleshoot. For a self- launching glider with an engine that
stows in the fuselage behind the pilot, the added drag of an extended engine can reduce the glide ratio by 50 to 75 percent.
[Figure 11-17]
Figure 11-17. Effects on the glide ratio of the engine being extended but not running.
The engine starting procedure in a self-launching glider increases the critical decision height to commit to an off- field
landing. The time needed to start the engine and extra drag during the starting process can add anywhere from 200 feet to
500 feet of altitude lost to extend and start the engine. Whereas a pure glider may commit to landing at 1,000 feet AGL, the
pilot of a self-launching glider probably opts for 1,500 feet AGL, depending on the glider and landing options should the
engine fail to start. In this sense, the self-launching glider becomes more restrictive during cross-country flying.
Cross-country flight can also be done under power with a self-launching glider, or a combination of powered and soaring
flight. For some self-launching gliders, the most efficient distance per gallon of fuel uses a maximum climb under power
followed by a power-off glide. Pilot should check the GFM/POH for recommendations.
Another type of glider features a sustainer engine. Although this type of engine does not have enough power for self-
launching, it can keep the glider airborne if lift fails. However, sustainer engines can only produce enough power to
overcome the glider’s sink rate. Higher sink rates can overwhelm the capability of many sustainer powerplants. Sustainer
engines typically eliminate the need for a time-consuming retrieval at the end of a cross country, and they operate with less
complexity than their self-launching counterparts. Pilots flying a glider with a sustainer engine have similar concerns as
pilots flying self-launching gliders regarding unsuitable terrain and altitude decision heights.
High-Performance Glider Operations & Considerations
Extended cross-country flights have been made in relatively low-performance gliders. However, on any given soaring day,
the same pilot can fly a glider with a 40:1 glide ratio farther and faster than one with 20:1 ratio.
Glider Complexity
The experience required to fly a high-performance glider does not necessarily depend on a pilot’s total glider hours. Pilots
should consider the types of gliders flown (low and high performance). Most high-performance gliders have a single
seat. The pilot should obtain some instruction from an authorized flight instructor in a two-seat high performance glider,
if available, before attempting to fly a single seat high-performance glider for the first time. Before flying any single-
seat glider, pilots should thoroughly familiarize themselves with the GFM/POH, including important speeds, weight and
balance issues, and all systems in the glider.
Many high-performance gliders have flaps. Pilots can use a few degrees of positive flap when thermalling, 0° for
relatively low-speed glides, and negative flap settings for glides at higher speeds. The GFM/POH and glider polar provide
recommended flap settings for different speeds, as well as maximum speeds allowed for different flap settings. A few high-
performance gliders have no air brakes and use large positive flap settings for landing.
Water Ballast
Water ballast can maximize average cross-country speed on a day with strong thermals. The gain in speed between thermals
outweighs the lost time due to slightly slower climbs with water ballast. Pilots should not plan to use ballast on a day with
weak thermals. If strong thermals become weak, the pilot can dump the water ballast.
Water expands when going from the liquid state to the solid state. The force of the water ballast freezing can split composite
wing skins. If anticipating flying on a cross-country flight and spending time at levels with temperatures below 0 °C, the
pilot should add the GFM/POH recommended antifreeze to the ballast before departure.
Cross-Country Flight Using Other Lift Sources
Ridge or wave lift provides more consistent lift than thermals, allowing long, straight stretches of hundreds of miles at
high speed.
Pilots with little experience using ridge lift on a cross-country flight should plan for a day with ideal wind and weather.
On relatively low ridges, (e.g., in the eastern United States), ridge lift may not extend very high. The best lift often sits
very close to the ridge crest in turbulent air, and pilots might end up flying close to terrain in rough conditions for hours
at a time. If the pilot loses lift, maneuvering for an off-field landing might occur with little notice. In milder conditions,
the cross country might require thermalling to gain enough height to cross any ridge gap. If cumulus spread out to form a
stratus layer shading the ground and eliminate thermals, the pilot might need to use a wind facing slope to maintain soaring
flight while waiting for the shade to dissipate. Unless the sun returns and generates the thermal needed to gain sufficient
altitude, the pilot would need an alternate plan.
Wave lift can also provide opportunities for long or fast cross-country flights. Most record flights have been along mountain
ranges; flights more than 2,000 kilometers having been flown in New Zealand and along the Andes. In the United States,
speed records have been set using the wave in the lee of the Sierra Nevada Mountains. In theory, long-distance flights
could also occur by climbing high in a wave, then gliding with a strong tailwind to the next range downwind for another
climb. The pilot needs to consider physiology (cold, oxygen, etc.) and airspace restrictions for cross-country flights using
wave lift.
Convergence zones can also enhance cross-country speed. Even if the convergence does not form a consistent line and acts
only as a focus for thermals, dolphin flight could occur. When flying low, awareness of local, small-scale convergence can
help the pilot find thermal triggers and enable a climb back to a comfortable cruising height.
A pilot might find a combination of ridge, thermal, wave, and even convergence lift during one cross-country flight.
Optimum use of the various lift sources requires mental agility and makes for an exciting and rewarding flight.
Chapter Summary
Pilots should begin planning cross-country flights carefully and within their capability and that of the glider. Planning
includes a consideration of weather forecasts, possible routes, what to carry, airspace, and potential landing sites. On the
day of a planned flight, the pilot can choose from plans and routes considering the existing environmental conditions.
The pilot should brief any ground crew and complete all preflight checks without rushing. Pilots who make cross-country
flights know how to maximize the available lift to increase the average speed of the flight. They also understand and follow
sensible height restrictions to stay safe. They can divert when necessary and know when to commit to an off-airport landing
if lift becomes less than needed to continue. Pilots who fly powered gliders know that they commit to landing procedures
at safe altitudes and that they could encounter a situation where their engine does not start.