Introduction
A cross-country flight occurs when the pilot flies the glider beyond gliding distance from the local soaring site. Cross-
country flying requires more preparation and decision-making than a local flight. The pilot should determine if the glider,
equipment, and the pilot can maintain safely given the known and expected environmental conditions along the route of
flight.
Flight Preparation & Planning
If planning to use thermals, the pilot should consider the availability and strength of thermals, if they will remain active,
landing possibilities, and which airports along the course have a runway compatible with prevailing wind conditions.
The pilot should also consider what effect winds will have on gliding distance and the best speed to fly in sink between
thermals. While the main part of this chapter describes flying cross-country using thermals, increased preparation for
cross-country flights also involves other sources of lift, and this chapter provides a brief description of cross-country
soaring using ridge or wave lift.
Getting Ready for Cross-Country Glider Flights
Adequate soaring skills indicate pilot readiness for cross-country soaring. Until the pilot has flown several flights more
than 2 hours and can locate and utilize thermals consistently, the pilot should focus on improving those skills before
attempting cross-country flights.
Any cross-country flight could end in an off-field landing, so pilots planning to fly on cross-country flights should also
perfect their short-field landing skills. Pilots can practice these landings on local flights by setting up a simulated off-field
landing area at an airport or glider port. The first few simulated landings should utilize the services of an instructor, and
the pilot should practice several landings without using the altimeter. Pilots should try to avoid interfering with the normal
flow of traffic during simulated off-field landings.
In addition, the pilot should know what airspace exits along the planned route including different classes (B, C, D, E, G),
restricted areas, prohibited areas, and military operations areas. The pilot should understand implications of any airways
along the flightpath. Once comfortable with the sectional during ground study, pilots can locate landmarks and features
within a few miles of the soaring site from the air.
While short-field training can use a known area, site selection training involves selecting a landing site from the air. Using
a self-launching glider or other powered aircraft to practice landing area selection allows simulated approaches to different
selected areas in a condensed time frame.
Glider pilots can use an electronic or paper Sectional Aeronautical Chart to determine position along a route of flight
during cross-country flights. These charts publish with updates every 56 days and contain general information, such
as topography, cities, major and minor roads and highways, lakes, and other features that may stand out from the air,
such as a ranch in an otherwise featureless prairie. In addition, sectionals show the location of public, and some private,
airports, airways, restricted and warning areas, and boundaries and vertical limits of different classes of airspace. Charted
information on airports includes field elevation, orientation and length of all paved runways, runway lighting, and radio
frequencies in use. Each sectional features a comprehensive legend. A detailed description of the sectional chart is found in
FAA-H-8083-25, the Pilot’s Handbook of Aeronautical Knowledge. Figure 11-1 shows a sample sectional chart.
Chapter 11: Cross-Country Soaring
Figure 11-1. Excerpt from a Sectional Aeronautical Chart.
Pilots should spend a significant amount of time studying sectional charts on the ground. This includes flying some
“virtual” cross-country flights in various directions from the local soaring site. In addition to studying the terrain (hills,
mountains, large lakes) that may affect the soaring along the route, the pilot should study the various lines and symbols
and answer the following questions:
• What airports are available on course?
• Do any have a control tower?
• What do all the numbers and symbols for each airport mean?
• What do other chart symbols mean?
GPS navigation and moving map displays enhance awareness of position during flight or after an off-field landing, and
pilots should take advantage of this technology. However, pilots should practice verifying position with a sectional chart
while in the air in case the GPS fails.
Any cross-country flight may end with a landing away from the home soaring site, so pilots and crews should prepare for
that occurrence prior to flight. Sometimes an aerotow retrieval can take place if the flight terminates at an airport; however,
trailer retrievals occur more often. Both the trailer and tow vehicle should be in good operating condition before the pilot
departs on a cross-country flight, and the pilot and retrieval crew should discuss communication options prior to flight.
The pilot should obtain a standard briefing and a soaring forecast from an approved weather source. The briefing should
include general weather information for the planned route, as well as any NOTAMs, AIRMETs, or SIGMETs, winds aloft,
approaching front, or areas of likely thunderstorm activity. Depending on the weather outlook, inexperienced pilots may
find it useful to discuss options with more experienced pilots at their soaring site.
The pilot should contact a briefer or NWS-derived source for a current soaring forecast. As briefly discussed in Chapter
9, Glider Flight and Weather, certain NWS Weather Forecast Offices (WFO) issue soaring forecasts. These automated
forecasts primarily derive from the radiosonde observation or model-generated soundings. The content and format of a
soaring forecast vary depending on the NWS WFO providing the forecast and the needs of the local soaring community.
A soaring forecast issues once per day without continuous monitoring or updating after initial issuance. The content and
format of a soaring forecast as well as the issuance times are subject to change without prior notice. The following sample
soaring forecast came from the WFO in Salt Lake City, Utah [Figure 11-2]:
Soaring Forecast
National Weather Service Denver/Boulder, Colorado
645 AM MDT Wednesday August 25, 2010
This forecast is for Wednesday August 25, 2010:
If the trigger temperature of 77.3 F/25.2 C is reached...then
Thermal Soaring Index....................... Excellent
Maximum rate of lift........................ 911 ft/min (4.6 m/s)
Maximum height of thermals.................. 16119 ft MSL (10834 ft AGL)
Forecast maximum temperature................... 89.0 F/32.1 C
Time of trigger temperature.................... 1100 MDT
Time of overdevelopment........................ None
Middle/high clouds during soaring window....... None
Surface winds during soaring window............ 20 mph or less
Height of the -3 thermal index................. 10937 ft MSL (5652 ft AGL)
Thermal soaring outlook for Thursday 08/26..... Excellent
Wave Soaring Index............................. Poor
Wave Soaring Index trend (to 1800 MDT)......... No change
Height of stable layer (12-18K ft MSL)......... None
Weak PV A/NV A (through 1800 MDT)................ Neither
Potential height of wave....................... 14392 ft MSL (9107 ft AGL)
Wave soaring outlook for Thursday 08/26........ Poor
Remarks...
Sunrise/Sunset.................... 06:20:55 / 19:42:44 MDT
Total possible sunshine........... 13 hr 21 min 49 sec (801 min 49 sec)
Altitude of sun at 13:01:25 MDT... 60.82 degrees
Upper air data from rawinsonde observation taken on 08/25/2010 at 0600 MDT
Freezing level.................. 15581 ft MSL (10296 ft AGL)
Additional freezing level....... 54494 ft MSL (49209 ft AGL)
Convective condensation level... 13902 ft MSL (8617 ft AGL)
Lifted condensation level....... 14927 ft MSL (9641 ft AGL)
Lifted index.................... -3.4
K index......................... +9.7
* * * * * * Numerical weather prediction model forecast data valid * * * * * *
08/25/2010 at 0900 MDT | 08/25/2010 at 1200 MDT
|
K index... +4.0 | K index... -0.7
This product is issued twice per day, once by approximately 0630 MST/0730
MDT (1330 UTC) and again by approximately 1830 MST/1930 MDT (0130
UTC). It is notcontinuously monitored nor updated after its initial issuance.
The information contained herein is based on rawinsonde observation and/or
numerical weather prediction model data taken near the old Stapleton
Airport site in Denver, Colorado at
North Latitude: 39 deg 46 min 5.016 sec
West Longitude: 104 deg 52 min 9.984 sec
Elevation: 5285 feet (1611 meters)
and may not be representative of other areas along the Front Range of the
Colorado Rocky Mountains. Note that some elevations in numerical weather
prediction models differ from actual station elevations, which can lead to
data which appear to be below ground. Erroneous data such as these should
not be used.
The content and format of this report as well as the issuance times are subject
to change without prior notice. Comments and suggestions are welcome and
should be directed to one of the addresses or phone numbers shown at the
bottom of this page. To expedite a response to comments, be sure to mention
your interest in the soaring forecast.
DEFINITIONS:
Convective Condensation Level - The height to which an air parcel possessing
the average saturation mixing ratio in the lowest 4000 feet of the airmass,
if heated sufficiently from below, will rise dry adiabatically until it
just becomes saturated. It estimates the base of cumulus clouds that are
produced by surface heating only.
Convection Temperature (ConvectionT) - The surface temperature required to
make the airmass dry adiabatic up to the given level. It can be considered a
"trigger temperature" for that level.
Freezing Level - The height where the temperature is zero degrees Celsius.
Height of Stable Layer - The height (between 12,000 and 18,000 feet above
mean sea level) where the smallest lapse rate exists. The location and
existence of this feature is important in the generation of mountain
waves.
K Index - A measure of stability which combines the temperature difference
between approximately 5,000 and 18,000 feet above the surface, the amount
of moisture at approximately 5,000 feet above the surface, and a measure
of the dryness at approximately 10,000 feet above the surface. Larger
positive numbers indicate more instability and a greater likelihood of
thunderstorm development. One interpretation of K index values regarding
soaring in the western United States is given in WMO Technical Note 158
and is reproduced in the following table:
below -10 no or weak thermals
-10 to 5 dry thermals or 1/8 cumulus with moderate thermals
5 to 15 good soaring conditions
15 to 20 good soaring conditions with occasional showers
20 to 30 excellent soaring conditions, but increasing
probability of showers and thunderstorms
above 30 more than 60 percent probability of thunderstorms
Lapse Rate - The change with height of the temperature. Negative values
indicate inversions.
Lifted Condensation Level - The height to which an air parcel possessing the
average dewpoint in the lowest 4000 feet of the airmass and the forecast
maximum temperature must be lifted dry adiabatically to attain saturation.
Lifted Index - The difference between the environmental temperature at a level
approximately 18,000 feet above the surface and the temperature of an air
parcel lifted dry adiabatically from the surface to its lifted condensation
level and then pseudoadiabatically thereafter to this same level. The
parcel`s initial temperature is the forecast maximum temperature and its
dewpoint is the average dewpoint in the lowest 4000 feet of the airmass.
Negative values are indicative of instability with positive values showing
stable conditions.
Lift Rate - An experimental estimate of the strength of thermals. It is
computed the same way as the maximum rate of lift but uses the actual
level rather than the maximum height of thermals in the calculation.
Also, none of the empirical adjustments based on cloudiness and K-index
are applied to these calculations.
Maximum Height of Thermals - The height where the dry adiabat through the
forecast maximum temperature intersects the environmental temperature.
Figure 11-2. Sample Soaring Forecast.
In the sample soaring forecast depicted above, the line for Height of the -3 Thermal Index represents the difference
between the environmental temperature and the temperature at a particular level determined by following the dry adiabat
through the forecast maximum temperature up to that level. Increasing magnitude of a negative value indicates stronger
thermal lift. A value of -3 or below generally indicates thermal activity favorable for cross-country soaring. Soaring pilots
should consult with the NWS WFO in their soaring area for more information about the soaring forecast.
Finalizing plans
Pilots may have specific goals for their upcoming cross-country flight and should plan based on the area and different
weather scenarios. If planning for a closed-course 300 nautical mile (NM) flight, the pilot should consider several possible
out-and-return or triangle courses ahead of time. On the day of departure, the pilot can select the best pre-planned option
based on the weather outlook. Since numerous final details need attention on the morning of the flight, accounting for the
items used during flight should take place the day before.
Lack of preparation can lead to delays, which may not leave enough of the soaring day to accomplish the planned flight.
Even worse, poor planning leads to hasty last-minute preparation and a rush to launch, making it easy to miss critical safety
items.
Inexperienced and experienced pilots alike should use checklists for various phases of the cross-country preparation to
organize the details. When properly used, checklists can help avoid oversights, such as missed assembly items, sectionals
left at home, barograph not turned on before takeoff, oxygen status, drinking water in the glider, etc. Checklists can cover
the following:
• Items to take to the gliderport (food, water, battery, charts, barograph).
• Assembly in accordance with the Glider Flight Manual/Pilot’s Operating Handbook (GFM/POH), including
assembly check and any other items as needed.
• Positive control check.
• Prelaunch (charts, barograph, glide calculator, oxygen on).
• Briefings for tow pilot, ground crew, and retrieval crew.
• Pre-takeoff.
Being better organized before the flight leads to less stress during the flight and enhances flight safety.
Personal & Special Equipment
Many items not required for local soaring ensure pilot comfort on long cross-country flights. An adequate supply of
drinking water prevents dehydration. Some pilots use a backpack drinking system with a readily accessible hose and bite
valve. This system stows easily beside the pilot and allows frequent sips of water. Pilots should also have food onboard
since cross-country flights can last up to 8 hours or more. Pilots should also have a relief system on longer flights.
Several items carried onboard can assist in case of an off-field landing. (For more details, see Chapter 8, Abnormal and
Emergency Procedures.) For example, the land-out kit should include a system for securing the glider. The remaining
contents of a land-out kit depend on the population density and climate of the soaring area. A safe landing site may occur
many miles from the nearest road, and the land-out kit should include extra water and food for this contingency. Walking
shoes could prove valuable should the pilot need to hike to a structure some distance away. A mobile phone proves useful
for landings in areas with cell coverage. Some pilots elect to carry an Emergency Position Indicating Radio Beacon
(EPIRB) in case of mishap during a remote off-field landing.
Cross-country soaring requires some means of measuring distances to the next source of lift or the next suitable landing
area. Pilots can use a GPS system for measuring distances or a mechanical system such as a plotter and paper chart.
[Figure 11-3]
INSTRUCTIONS FOR USE
1. Place hole over intersection of true course and true north line.
2. Without changing position rotate plotter until edge is over true course line.
3. From hole follow true north line to curved scale with arrow pointing in direction of flight.
4. Read true course in degrees, on proper scale, over true north line. read scales counter-clockwise.
SECTIONAL CHART SIDE - 1:500,000 NAVIGATIONAL FLIGHT PLOTTER
350 170
190 10
40 230
50 240
NAUTICAL 5 MILES 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 NAUTICAL 85 MILES
0 STATUTE 5 MILES 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 9585 100 90
DEGREES
Figure 11-3. Navigational plotter.
Glide calculations take headwinds or tailwinds into account, as well as speeds to fly through varying sink rates as discussed
in chapter 5, Glider Performance. Tools range widely in their level of sophistication, but all account for the performance
polar for the glider. The simplest glide aid derived from the polar consists of a table showing altitudes required for distance
versus wind. Another option consists of a circular glide calculator as shown in Figure 11-4. The settings in Figure 11-4
indicate that a glide of 18 miles in an estimated 10 knot headwind takes 3,600 feet. Note that this only gives the altitude
required to make the glide. High-performance gliders often have glide/navigation computers that automatically compute
the glide ratio (L/D).
2 4
RATE OF
CLIMB (KTS)
SPEED TO FLY (KTS)
30 20 10 0 10 20 30
30 20 10 0 10 20 30
(KTS)
HEAD WING TAIL WIND
TAIL WING HEAD WIND
(KTS)
9 8
50 40
DISTANCE (NM
)
ALTITUDE (1000 FT)
Figure 11-4. Circular glider calculator.
Another method allows a pilot to compute effective L/D by utilizing a standard formula. Glide ratio, with respect to the air
(GRA) or L/D, remains constant at a given airspeed. For example, the pilot might know the glide ratio, and lift over drag
(L/D) being 30 to 1 (expressed as 30:1) for a speed of 50 knots in a specific glider. At 50 knots airspeed with an L/D of
30:1, a 10-knot tailwind results in an effective L/D of 36:1. [Figure 11-5]
Glider specifications
Glide ratio (L/D) = 30:1
Speed (GRA) = 50 knots
Tailwind component
Wind = +10 knots
50 + 10 = 60
60/50 = 1.2
1.2 x 30 = 36
Effective glide ratio (L/D) is 36:1
Headwind component
Wind = −10 knots
50 − 10 = 40
40/50 = 0.8
0.8 x 30 = 24
Effective glide ratio (L/D) is 24:1
GRA ± Wind
GRA
x L/D = Effective L/D( )
Figure 11-5. Glide calculation examples for a headwind and a tailwind.
In addition to a glide calculator, a flight computer or MacCready ring on the variometer gives the pilot the appropriate speed
to fly for different sink rates. Data such as windspeed and direction may be manually or automatically input depending on
the age and capability of the flight computer. Accurately flying the correct speed in sinking air can extend the achieved
glide considerably.
Many models of electronic glide calculators exist. Often coupled with an electronic variometer, they display the altitude
necessary for distance and wind as input by the pilot. In addition, many electronic glide calculators feature speed-to-
fly functions that indicate whether the pilot should fly faster or slower. Most electronic speed-to-fly directors include
audio indications, so the pilot can remain visually focused outside the cockpit. The pilot should have manual backups for
electronic glide calculators and speed-to-fly directors in case of a low battery or other electronic system failure.
Other equipment may verify soaring performance that allows a pilot to receive a Federation Aeronautique Internationale
(FAI) badge or to record flights. These include turn-point cameras, barographs, and GPS flight recorders. For complete
descriptions of these items, as well as badge or record rules, check the Soaring Society of America website for details.
Finally, pilots should consider using a notepad or kneeboard on which to make notes before and during the flight. Notes
prior to flight could include weather information such as winds aloft forecasts or distance between turn points. In flight,
noting takeoff and start time and time around any turn points helps gauge average speed around the course.
Navigation
Airplane pilots navigate by pilotage (flying by reference to ground landmarks) or dead reckoning (computing a heading
from true airspeed and wind, and then estimating time needed to fly to a destination). Glider pilots generally use pilotage
since they often deviate from a course line over a long distance and do not fly one speed for any length of time. At times,
glider pilots might use a combination of the two methods.
A Sample Cross-Country Flight
For training purposes, a pilot could plan a triangle course starting at Portales Airport (PRZ), with turn points at Benger
Airport (X54), and the town of Circle Back. The preflight preparation includes drawing the course lines for the three legs
using an electronic system or chart. [Figure 11-6]
Portales
Benger Airport
Bovina
Friona
Clovis
Clovis airport
Salt Lake
Needmore
Arch
Class D Airspace
Muleshoe
Muleshoe airport
Circle Back
Figure 11-6. Cross-country triangle drawn on the Albuquerque Sectional Chart.