Great Planes GPMA17 User Manual

WARRANTY

Great Planes®Model Manufacturing Co.guarantees this kit to be free from defects in both material and workmanship
at the date of purchase.This warranty does not cover any component parts damaged by use or modification.In no case
shall Great Planes’ liability exceed the original cost of the purchased kit. Fur ther, Great Planes reserves the right
to change or modify this warranty without notice.

In that Great Planes has no control over the final assembly or material used for final assembly, no liability shall be
assumed nor accepted for any damage resulting from the use by the user of the final user-assembled product.By the act
of using the user-assembled product, the user accepts all resulting liability.

If the buyers are not prepared to accept the liability associated with the use of this product,they are advised
to return this kit immediately in new and unused condition to the place of purchase.

READ THROUGH THIS INSTRUCTION MANUAL
FIRST. IT CONTAINS IMPORTANT INSTRUCTIONS
AND WARNINGS CONCERNING THE ASSEMBLY
AND USE OF THIS MODEL.

GPMZ0228 V1.1 For GPMA17** Entire Contents © Copyright 2002

P.O.Box 788 Urbana, IL 61801 [phone]

[e-mail]

INSTRUCTION MANUAL

™

IMPORTANT SAFETY PRECAUTIONS . . . . . . . . . . . . . 2

PREPARATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Building Supplies and Tools . . . . . . . . . . . . . . . . . . . . 3

Optional Supplies and Tools . . . . . . . . . . . . . . . . . . . . 3

Other Required Items . . . . . . . . . . . . . . . . . . . . . . . . . 3

General Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Important Building Notes . . . . . . . . . . . . . . . . . . . . . . . 3

Metric Conversions. . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Metric/Inch Ruler . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

REPLACEMENT PARTS . . . . . . . . . . . . . . . . . . . . . . . . 4

ASSEMBLY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Wing Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Tail Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Wing Dowel Installation. . . . . . . . . . . . . . . . . . . . . . . . 6

Radio Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Balance The Model . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Checking For Warps . . . . . . . . . . . . . . . . . . . . . . . . . . 7

PREFLIGHT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Batteries. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Find a Safe Place to Fly . . . . . . . . . . . . . . . . . . . . . . . 8

Range Check Your Radio . . . . . . . . . . . . . . . . . . . . . . 8

AMA SAFETY CODE (EXCERPT) . . . . . . . . . . . . . . . . . 8

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Radio Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

FLYING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Trim Flights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

First Flights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Thermal Flying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Facts About Thermals. . . . . . . . . . . . . . . . . . . . . . . . 10

Thermal Soaring. . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Pointers for Contest Flying . . . . . . . . . . . . . . . . . . . . 11

FLIGHT LOG . . . . . . . . . . . . . . . . . . . . . . . . Back Cover

Your SPECTRA™SELECT is not a toy, but rather a

sophisticated, working model that functions very much like a
full-size sailplane. Because of its realistic performance, the
SPECTRA SELECT, if not assembled and operated

correctly, could possibly cause injury to yourself or
spectators and damage property.

To make your R/C modeling experience totally enjoyable,
we recommend that you get experienced, knowledgeable
help with assembly and during your first flights.You’ll learn

faster and av oid risking your model before you’re truly ready to
solo.Your local hobby shop has information about flying clubs
in your area whose membership includes qualified instructors.
You can also contact the national Academy of Model
Aeronautics (AMA), which has more than 2,500 chartered
clubs across the country.

Through any one of them, instructor training programs and
insured newcomer training are available. Contact the AMA at
the address or toll-free phone number below.

Academy of Model Aeronautics

5151 East Memorial Drive

Muncie, IN 47302-9252

Tele. [phone]

Fax [phone]

or via the Internet at http://www.modelaircraft.org

1. Build the plane according to the plan and instructions.Do
not alter or modify the model, as doing so may result in an
unsafe or unflyable model. In a few cases the plan and
instructions may differ slightly from the photos. In those
instances the plan and written instructions are correct.

2.Take time to build straight, true and strong.

3. Use an R/C radio system that is in first-class condition,
and a correctly sized motor and components (batteries,
etc.) throughout your building process.

4.You must properly install all components so that the model
operates properly on the ground and in the air.

5.You must check the operation of the model before every
flight to ensure that all equipment is operating and that the
model has remained structurally sound. Be sure to check
nylon clevises or other connectors often and replace them if
they show signs of wear or fatigue.

Remember:Take your time and follow directions to end
up with a well-built model that is straight and true.

Please inspect all parts carefully before starting to
build! If any parts are missing, broken or defective,or if
you have any questions about building or flying this
airplane, please call us at:

[phone]

or e-mail us at:

[e-mail].

If you are calling for replacement parts, please
reference the part numbers and the kit identification
number (stamped on the end of the carton) and have
them ready when calling.

Note:We, as the kit manufacturer, provide you with a top

quality kit and great instructions, but ultimately the quality
of your finished model depends on how you build it;
therefore, we cannot in any way guarantee the
performance of your completed model, and no
representations are expressed or implied as to the
performance or safety of your completed model.

PRO TECT YOUR MODEL,YOURSELF

& OTHERS...FOLLOW THESE

IMPORTANT SAFETY PRECAUTIONS

TABLE OF CONTENTS

2

The SPECTRA SELECT is a very stable and predictable
aircraft, allowing pilots of differing skill levels to enjoy it.It is
easy to build, flies great, and would be a great selection as
your first R/C airplane.

These are the building supplies and tools that are required.
We recommend Great Planes brand accessories.

❏ Phillips Screwdriver
❏ Pliers
❏ Great Planes Pro

™

Threadlocker (GPMR6060)

❏ Top Flite

®

Sealing Iron (TOPR2100)

❏ Top Flite Hot Sock

™

Iron Cover (TOPR2175)

❏ Top Flite Heat Gun (TOPR2000)

❏ 8-AA Alkaline Batter ies
❏ Charger for 7-cell, 2100 mAh NiCd Battery.

Remove the fuselage, wing panels, rudder assembly and
stabilizer assembly from their individual bags. Inspect all
items closely to check for any damage. If any damage is
found, contact the place where your SPECTRA SELECT
was purchased, or Hobby Services, to obtain a
replacement for your damaged items.

Your SPECTRA SELECT is covered using Top Flite

®

MonoKote®covering. Eliminate any wrinkles you find in the
covering by shrinking them away with a heat gun. Then,
apply pressure to the area with a covering iron and a
hot sock. This will securely bond the covering to the wood

so the wrinkles will be less likely to reappear in the future.

Several times during construction we refer to the “top” or
“bottom” of the model or a part of the model. It is
understood that the “top” or “bottom” of the model is as it
would be when the airplane is right side up and will be
referred to as the “top”even if the model is being worked on
upside-down.

Important Building Notes

General Inspection

Other Required Items

Optional Supplies and Tools

Building Supplies and Tools

PREPARATIONS

3

1/64" = .4 mm
1/32" = .8 mm
1/16" = 1.6 mm
3/32" = 2.4 mm

1/8" = 3.2 mm
5/32" = 4.0 mm
3/16" = 4.8 mm

1/4" = 6.4 mm

3/8" = 9.5 mm
1/2" = 12.7 mm
5/8" = 15.9 mm
3/4" = 19.0 mm

1" = 25.4 mm
2" = 50.8 mm
3" = 76.2 mm
6" = 152.4 mm

12" = 304.8 mm
18" = 457.2 mm
21" = 533.4 mm
24" = 609.6 mm
30" = 762.0 mm
36" = 914.4 mm

Metric Conversions

4

8
9

10

11
12

13

1
2
3

4

6

7

5

Key # Description Qty

1 TRANSMITTER.................................1

2 RIGHT WING PANEL ........................1

3 BATTERY...........................................1

4 CANOPY............................................1

5 SPINNER/PROPELLER....................1

6 RUBBER BANDS ..............................4

7 WING DOWELS ................................2

8 STAB & ELEVATOR ...........................1

Key # Description Qty

9 FUSELAGE........................................1

10 LEFT WING PANEL...........................1

11 WING JOINER...................................1

12 PLASTIC WING DOWEL CAPS........4

13 METAL HARDWARE

PARTS LIST

REPLACEMENT PARTS

If needed, replacement parts for your Spectra Select are available through your hobby supplier.

GPMA2340......Wing Kit

GPMA2341......Fuselage

GPMA2342......Tail Set

GPMA2343......Motor

GPMA2344......Battery

GPMA2345......ESC

GPMQ1690.....Propeller

❏ 1. Locate the wing joiner and insert it into the r ight wing

joiner pocket as shown in the above picture.

❏2.Insert the other side of the wing joiner into the left wing

joiner pocket and slide the wings together.

❏ 3.Completed wing

❏ 1. Find and open the holes in the stabilizer covering for the

attachment bolts. Attach the stabilizer to the fuselage using
two 2mm x 15mm bolts, two 2mm nuts and four 2mm

washers.
Use thread lock on the nuts to prev ent loosening.Note: The fin
was removed on these images for clarity.

❏ 2.The fin comes pre-installed on the Spectra Select, but

you should check that the hex nuts are tight. Also, you
should use some Great Planes Pro Threadlocker to prevent
the nuts from coming loose.

❏ 3.Verify that the rudder clevis is attached to the 4th hole

from the inside of the rudder’s control horn.Also, make sure
that the silicone retainer is properly installed on the clevis.

Tail Assembly

Wing Assembly

ASSEMBLY

5

❏ 4. Completely undo any antenna knot. Gently extend the

antenna and let it dangle freely out the end of the aft
fuselage. Connect the elevator clevis to the elevator control
horn at the 4th hole from the inside. Note: Never cut or
shorten the antenna wire.

❏ 1. Install the wing dowels into the wing dowel holes as

shown. Be sure that the smaller dowel (7mm x 90mm)
should be installed into the aft holes.Note: The canopy was
removed in this image for clarity.

Tur n the transmitter switch on. Install the motor battery in
the airplane under the speed control and connect it to the
receiver.Turn the receiver switch on.Mark the “ON” position
of the switch. Note: The position of the receiver switch and
safety button may vary slightly from what you see in the
above image.

Center the surfaces using the trims on your radio
transmitter. Use the sketch above to make sure the control
surfaces are moving in the correct directions.

The control throws are as follows:

UP DOWN

Elevator 1/2" [13mm] 1/2" [13mm]

LEFT RIGHT

Rudder 1-1/2" [38mm] 1-1/2" [38mm]

Radio Settings

Wing Dowel Installation

6

To star t your Spectra Select motor you need to follow this
procedure:

• Make sure the motor ratchet on the transmitter is in
the “Off” position.

• Move the prop away from any objects.

• Switch on the transmitter.

• Connect the motor battery and switch on the receiver.

• Press the safety switch once.

• The motor is now armed. If you move the motor
ratchet to the right, the motor will turn on.

Note: This section is very important and must not be
omitted! A model that is not properly balanced will be

unstable and possibly unflyable.
The C.G.–Center of Gravity–range for this airplane is

located 2-3/4" to 3-1/2" [70mm to 88mm] from the LE.If your
model balances anywhere within this range, it will fly fine.
Generally if the C.G. is in the forward part of the range, the
model will have e xtra stability b ut its o v erall perf ormance will
decrease slightly and the stall speed will increase. If the
C.G.is in the aft side of the range, the sailplane will be more
agile with a lighter and “snappier” feel. The aft C.G. also
improves the Spectra Select’s response to air currents.The
downside of the aft C.G.is that it makes the Spectra Select
less stable and it can cause the model to “tuc k under”or

dive

when its flying speed increases. Do not fly the

Spectra

Select with the C.G. outside the recommended range.

To balance your model, attach the wings to the fuselage with
the rubber bands included.The model should now be ready
to fly, with all parts installed. Make two marks on the
underside of each wing 2-3/4" and 3-1/2" [70mm and 80mm]

from the leading edge. Pick up the model with your fingers
under the wing within the C.G. range. Move your fingers
under the wing (always within the C.G. range) until the
stabilizer of the Spectra Select stays horizontal when you
pick it up.If your model balances within the C.G.range, then
you are safe to fly.If you need to pick up the model at a point
outside the C.G. range, then you need to add weight to the
nose or to the tail to get it to balance. Moving the radio
components inside the fuselage may help too.

DO NOT ATTEMPT TO FLY WITHOUT FIRST ACHIEVING
THE PROPER BALANCE.

This is a very important step and should be done
occasionally throughout the flying season. A sailplane’s

wing is most efficient when it is not twisted or warped at all.
“Washout” (wing trailing edges twisted up at the tip) helps
make a poor wing design fly better by adding some stability
(preventing stalls) at slow speeds but it cuts down on the
wing efficiency at normal speeds.The Spectra Select’s wing
is designed to fly well at slow speeds without any washout,
and therefore we recommend you check to make sure the
wings are “flat” using the following procedure:

Set the wing so an inner panel is resting on a flat surface.
Any warp (twist) will show up by causing a corner of the
panel to rise off the work surface.

To remove the warp, gently twist the wing in the opposite
direction while a helper glides an iron or heat gun over the
covering on both the top and the bottom of the panel to re­shrink the covering. Hold the twist until the covering cools
and then recheck for warps. It may take several tries to get
a warp out but it is worth it as you will end up with a
sailplane that flies straight and true and responds to air
currents like a high performance sailplane should.

Follow the same procedure to check all four wing panels
and then go back and double check them. Sometimes you
put a warp in one panel while trying to fix another. You
should also look at the tail surfaces as they too can warp.

The radio supplied with the Spectra Select uses non­rechargeable dry batteries.We recommend you to use good
quality Alkaline batteries for better performance.The motor
battery supplied with the Spectra Select is a 7-cell 2100
NiCd battery. You should use a charger adequate for
charging this battery. Follow the charger’s instructions to
charge the motor battery.

Batteries

PREFLIGHT

Checking for Warps

Balance the Model

RATCHET

7

The best place to fly your R/C model is an AMA (Academy
of Model Aeronautics) chartered club field. Ask your hobby
shop dealer if there is such a club in your area and join.Club
fields are set up for R/C flying which makes your outing
safer and more enjoyable. The AMA can also tell you the
name of a club in your area. We recommend that you join
AMA and a local club so you can have a saf e place to fly and
also have insurance to cover you in case of a flying
accident. (The AMA address is listed on page 2 of this
instruction book).

If a club and its flying site are not available, you need to find
a large, grassy area at least 6 miles away from any other
R/C radio operation and away from houses, buildings and
streets. A schoolyard may look inviting but it is usually too
close to people, power lines and possible r adio interf erence .

If you are not thoroughly familiar with the operation of R/C
models, ask an experienced modeler to check to see that
you have the radio installed correctly and that all the control
surfaces do what they are supposed to.

Wherever you do fly, you need to check the operation of the
radio before every time you fly. This means with the
transmitter antenna collapsed and the receiver and
transmitter on, you should be able to walk at least 100 feet
away from the model and still have control. Have someone
help you. Have them stand by your model and, while you
work the controls, tell you what the various control surfaces
and your motor are doing.

Read and abide by the following Academy of Model
Aeronautics Official Safety Code excerpts:

1. I will not fly my model aircraft in competition or in the
presence of spectators until it has been proven to be airworthy
by having been previously successfully flight tested.

2. I will not fly my model aircraft higher than approximately
400 feet within 3 miles of an airport without notifying the
airport operator.I will give right of way to, and avoid flying in
the proximity of full-scale aircraft. Where necessary an
observer shall be utilized to supervise flying to avoid having
models fly in the proximity of full-scale aircraft.

3.Where established, I will abide by the safety rules for the
flying site I use, and I will not willfully and deliberately fly my
models in a careless, reckless and/or dangerous manner.

1. I will have completed a successful radio equipment ground
check before the first flight of a new or repaired model.

2. I will not fly my model aircraft in the presence of
spectators until I become a qualified flyer, unless assisted
by an experienced helper.

3.I will perform my initial turn after takeoff away from the pit,
spectator and parking areas, and I will not thereafter
perform maneuvers, flights of any sort or landing
approaches over a pit, spectator or parking area.

First of all, if you are flying with other modelers check
to make sure they are not flying or testing on the same
frequency as your model.

Try to find an experienced pilot to help you with your first
flights.Although the SPECTRA SELECT is very easy to fly, an

experienced pilot can save you a lot of time and possible
aggravation by helping you get your model in the air smoothly.

It is a good idea to do a couple of trim flights, without the
motor running, before each flying session to make sure the
plane is still in trim and the radio is working properly. The
model will survive a hard landing from 5 feet much better
than it will one from several hundred feet.The first few trim
flights should be done over a grass field. The longer the
grass the better (more cushion).

Turn on the transmitter first and then the receiver. Hold the
SPECTRA SELECT under the wing with the nose pointed
slightly down and directly into the wind.Do not run the motor for
these test flights.It is very important that you launch the model

Trim Flights

FLYING

Radio Control

General

AMA SAFETY CODE (

EXCERPT

)

Range Check Your Radio

Find a Safe Place to Fly

8

with the wings level and the nose pointing at a spot on the
ground about 50 feet in front of you.Have a friend stand off to
the side of you and tell you whether the nose is pointing up or
down. Show your friend the previous picture so he will know
what to look for .If the SPECTRA SELECT is launched with the
nose up or launched too hard it will climb a few feet, stall and
fall nose first straight down.With the nose pointed down slightly
the sailplane will accelerate down until it picks up enough flying
speed, then level off and glide forward. The plane should be
launched with a gentle push forward.With a little practice you
will be able to launch it at just the right speed so it soars straight
ahead in a long and impressive glide path. Adjust the elevator
and rudder trims on your transmitter to get the plane to fly
straight ahead in a smooth glide path.

Once you get the hang of launching it you can try turning the
plane during the trim flights by gently applying a “touch” of
right or left rudder.You can also try “flaring” the landings by
slowly applying a touch of up elev ator (pull the stick bac k) as
the plane nears the ground. The SPECTRA SELECT will
continue to fly just a few inches off the ground for a
surprisingly long distance. It is important you don’t “over­control” the model. Make any control inputs slowly and
smoothly rather than moving the transmitter sticks abruptly.

Find a BIG, OPEN field for your first flights.The bigger the
better as you won’t have to worry about where you need to
land. Ground based objects (trees, poles, buildings, etc.)
seem to attract model airplanes like a magnet. Again, we

would like to recommend that you find an experienced
pilot to help you with these first flights.

Note: You need to remember that your radio control
responds as if you were sitting in the cockpit.When you
push the transmitter stick to the right,the rudder moves
to the plane’s right! This means that when the plane is
flying towards you it may seem like the rudder controls
are reversed (when you give “right” rudder the plane
turns to your left–which is the plane’s “right”). It is

sometimes easier to learn to fly the plane if you always f ace
your body in the direction the plane is flying and look over
your shoulder to watch the model.

Turn on your transmitter and then your receiv er and hold the
model as you did for the hand launched test flights. Hold it
firmly and move the throttle stick up to test the motor
operation.When satisfied that everything is responding as it
should, launch the model straight into the wind just as you
did without the motor running. It is important that you do not
throw the airplane up or it may stall and hit the ground.If you
launch it level or slightly down the airplane will accelerate
and start climbing on its own.

Don’t worry about accomplishing very much on your first
flights. Use these flights to get the “feel” of the controls and
the SPECTRA SELECT’s flying characteristics.For the first
few seconds of the flight allow the airplane to gently climb

straight ahead. Try to keep the plane upwind and just
perform some gentle “S-turns”(always turning into the wind)
until it is time to set up for landing.Have a helper adjust the
trims on your transmitter (a little at a time) until it has
reached a comfortable soaring altitude (200' - 300').Turn the
motor off and allow the SPECTRA SELECT to soar around,
keeping the airplane upwind of yourself. When you feel it’s
getting too low, turn the motor back on and climb back to
altitude. It can be very hard for a beginner to fly a plane
straight towards him as he would have to do if the plane
were downwind. While the SPECTRA SELECT is gliding
have a helper to adjust the trims on your transmitter (a little
at a time) until the plane will fly straight and level with the
transmitter sticks in their neutral position.

When you can hear the motor starting to die off and/or the
plane does not want to climb anymore it is time to shut off
the motor for the last time (especially if you have BEC.) It is
important to remember that you no longer have enough
power to climb out again, so you only get one chance at
landing.When it is time to land, just continue performing the
gentle “S-turns” upwind and let the plane glide onto the
ground. Don’t worry about where the plane lands–just miss
any trees, etc. If you need to “stretch” a landing you can
switch the motor back on but do not expect it to be able to
carry you very far. When NiCd batteries start going dead,
they really go dead in a hurry. An alternative to allowing the
battery to become weak before shutting the motor off for
good is to time the motor runs so you can leave enough
“juice” in the battery for a couple of “go arounds” if needed.

Practice flying directly into the wind (upwind of yourself)
without letting the plane get off course, and then turn and
come downwind until the plane is even with you and try it
again.When you are comfortable with flying directly into the
wind, start letting the plane go behind you (downwind) a
little before you start back upwind. Continue this until you
can fly directly towards you from downwind without getting
disoriented.At this point you can start to establish a “landing
pattern” and bring the sailplane in for a landing from
downwind. Always land into the wind. This enables the
plane to be flown as slowly (ground speed) as possible for
accurate and damage free landings.

It is probably not a good idea to try and fly around at a low
altitude with the motor on during your first flights. This will
cause the airplane’s speed to increase and make the
controls more responsive which is just what a beginner does
not need.

Note: BEC is a system offered by most modern speed
controls that allows you to get rid of the radio battery and
use the motor battery as the means for supplying power
to the radio. The BEC will cut power to the motor when
the motor battery is low on charge but it will still give the
modeler enough power to use the radio normally for a
short time until landing. Keep in mind that while there is
still enough charge to use the radio the motor battery is
low, so you should land within 10 to 15 minutes of motor
cut out time.

First Flights

9

The SPECTRA SELECT will climb to altitude several times
on a single charge allowing you to have flights well over ten
minutes without finding any “lift.” You should be able to get
two full climbs above 500' on a single charge although there
are many factors that figure into this.

Thermal soaring is one of the most intriguing of all aspects
of flying and the SPECTRA SELECT was designed to excel
at thermal soaring even in the hands of a novice. It can be
hard for the average person to understand how a plane can
fly for a long time and gain altitude without a motor!

Thermals are a natural phenomenon that happen outside, by
the millions, every single day of the year. Thermals are
responsible for many things including forming several types of
clouds, creating breezes, and distributing plant seeds and
pollen.If you have e ver seen a dust de vil (which is nothing more
than a thermal that has picked up some dust), you have seen
a thermal in action.Their swirling action is very similar to that of
a tornado but of course much gentler. Most thermals have
updrafts rising in the 200 – 700 feet per minute range but they
have been known to produce updrafts of over 5,000 feet per
minute (that’s over 50 miles/hour straight up!) These strong
thermals can rip a plane apar t or carry the plane out of sight
before the pilot can get out of the updraft.

Thermals are formed by the uneven heating of the earth and
buildings, etc. by the sun. The darker colored surfaces
absorb heat faster than the lighter colors which reflect a
great deal of the sun’s energy bac k into space.These darker
areas (plowed fields, asphalt parking lots, tar roofs, etc.) get
warmer than the lighter areas (lakes, grassy fields, forests,
etc.). This causes the air above the darker areas to be
warmer than the air over the lighter areas and the more
buoyant warm air rises as the cooler, denser air forces its
way underneath the warmer air. As this warm air is forced
upward it contacts the cooler air of the higher altitudes and
this larger temperature difference makes the thermal rise
quicker.The thermal is gradually cooled by the surrounding
cooler air and its strength diminishes.Eventually the thermal
stops rising and any moisture contained in the once warm
air condenses and forms a puffy cumulus cloud. These
clouds, which mark the tops of thermals, are usually
between 2000 and 5000 feet high.

It takes a lot of concentration to thermal soar effectively. An
electric sailplane can fly along the edge of a thermal and
unless the pilot is carefully watching the model he may not
realize the opportunity to gain some altitude. Because most
thermals are relatively small (a couple hundred feet in

diameter or less at 400' altitude) compared to the rest of the
sky, the sailplanes will rarely fly directly into the thermal and
start rising. Generally, the electric sailplane will fly into the
edge or near a thermal and the effects the thermal has on
the plane may be almost unnoticeable. As the electric
sailplane approaches a thermal, the wing tip that reaches
the rising air first will be lifted before the opposite wing tip.
This causes the plane to “bank” and turn away from where
we would like the plane to go.

When you are thermal soaring, try to fly as smoothly and
straight as possible. Trim the plane to fly in a straight line
and only touch the controls when you have to. Watch the
electric sailplane carefully and it will tell you what it is
encountering.When the electric sailplane flies directly into a
thermal it will either start r ising or stop sinking. Either case
is reason enough to start circling (especially in a contest
where every second counts). Fly straight ahead until you
feel like you are in the strongest lift, fly a couple of seconds
farther (so your circle will be centered in the strongest lift)
and then start circling in a fairly tight but smooth turn.When
the electric sailplane is low the turns have to be tighter to
stay in the strongest lift. As the plane gains altitude, the
turns can be larger and flatter.The flatter the turn, the more
efficient the plane is flying, but don’t be afraid to really
“crank” it into a steep bank when you are low. If you see the
plane falling off on one side of the turn, move your circle
over into the stronger lift. Thermals move along with the
wind so as you circle you will be swept along with it. Be
careful when thermaling, that you don’t get so far downwind
you can’t make it back to the field to land.

If the electric sailplane is flying along straight and all of a
sudden turns, let the plane continue to bank (you may have
to give it some rudder to keep it banking) until it has turned
270-degrees (3/4 of a full circle). Straighten out the bank
and fly into whatever turned the plane. If you encounter lift,
and you won’t every time, start circling just as you did when
flying directly into a thermal.

Thermals are generated all day long, but the strongest
thermals are produced when the sun is directly overhead.
10:00 am – 2:00 pm seems to be the best time to get those
“killer” thermals. Some of these thermals can be very large
and you may find it hard to get out of them. If you find
yourself getting too high, don’t dive the plane to get out of
the lift. Sailplanes are very efficient aircraft and they will
build up a lot of speed and could “blow up” in the rough air
of a thermal. The easiest way to lose altitude is to apply full
rudder and full up elevator.This will put the plane into a tight
spin that will not over stress the airframe but it will enable it
to lose altitude very quickly. This is especially helpful if the
sailplane gets sucked into a cloud or it gets too high to see.
The twirling action will give the sun a better chance of
flashing off of the wing and catching your attention. When
you are high enough and want to leave the thermal, add a
little down trim to pick up some speed and fly 90 degrees to
the direction of the wind.If you are not real high and want to
find another thermal, you may want to look upwind of the
last thermal.The same source that generated this thermal is

Thermal Soaring

Facts About Thermals

Thermal Flying

10

probably producing another. Just watch out for “sink” which
is often found behind and between thermals.

As you might expect, with all this air rising, there is also air
sinking.This air is the electric sailplane pilot’s nightmare that
can really make soaring challenging.“Sink” is usually not as
strong as the thermals in the same area, but it can be very
strong.Down drafts of many hundreds of feet per minute are
common on a good soaring day. These down drafts can
make a sailplane look like it is falling out of the air.Because
of this, it is important that you do not let the sailplane get too
far downwind.

When encountering sink, immediately turn and fly 90
degrees to the direction of the wind (towards you if
possible). Apply a little “down elevator” and pick up some
speed to get out of the sink as fast as possible. Every
second you stay in the sink is precious altitude lost.

Pay Attention! – Pay close attention to the electric
sailplanes flying before you, watch them and try to establish
where and when the thermals are being formed. Thermals
are often formed in cycles and can be fairly regular , so if you
keep track of the time intervals you will have a pretty good
idea of when and where a thermal may be generated.

Watch The Birds! – Thermals suck up small insects that
many birds love to eat.A bunch of swallows flying around in
one area may indicate a thermal. Soaring birds (hawks,
vultures, eagles etc.) are the best thermal indicators. They
not only show you where the thermal is but they also show
you where the center is. These “Masters of the Sky” will
often fly right along with electric sailplanes.

Practice Those Landings! – Most thermal contests are
won or lost during the landing. Establish a particular landing
pattern and try to stick to it for all landings. Learn to shift
your pattern to account for the wind and the particular flying
field characteristics.

Concentrate – Keep your eye on your electric sailplane
during your contest flights. Have a helper or your counter
watch the other planes in the air. Sometimes your electric
sailplane will wiggle so quickly or gently that you may miss
it if you are not paying close attention. If you find a
productive thermal, don’t leave it because your helper tells
you that someone else has found a different one.

Know Your Electric Sailplane! – Learn what your electric
sailplane will and won’t do and fly within this envelope.This
will allow you to ride thermals downwind while knowing
when you have to head back to make your landing safely.

Learn From The Wind! – Keep track of which way the wind
is blowing.If the wind suddenly shifts, there is some thermal
action fairly close to you. The air is probably being either
sucked up into a thermal or falling out of some sink.In either
case it is often a good idea to fly in the direction the wind is

blowing if your sailplane is in the general area.This will take
you towards a thermal if there is one or away from the sink,
both of which are desirable.

Have a ball! Remember to always stay in control and fly
in a safe manner.

Great Planes Spectra ARF

The all-wood, preassembled, 2-meter Spectra ARF arrives
expertly covered with Top Flite®MonoKote®film.An included
Goldfire 550 motor and 8 x 4 folding prop quickly carry it to
soaring altitudes following an easy hand-launch. The wing
features a triple taper planform and semi-symmetrical airfoil
that increases stability for smooth, forgiving flight.Required
are a 3-channel radio, NiCd battery and charger .

GPMA1050

Great Planes Spirit™Select

The 78.5" span Spirit sailplane offers the ultimate in flying
ease and enjoyment! Its all wood airframe has control
surfaces built-in. Once the slide-together wing and bolt-on
tail are in place, it’s ready to fly. Plus, it’s covered with Top
Flite MonoKote, with stripes on the wing bottom to make
orientation easy. It’ll delight first-timers with its slow, steady
flight, and competitors with its thermal chasing abilities.The
Spirit Select RTF comes complete with a 3-channel Hitec

®

Focus 3 SS radio, with servos and foam-wrapped receiver
preinstalled – only a dozen “AA”cells are required!

GPMA16**

OTHER ITEMS AVAILABLE FROM

GREAT PLANES

Pointers for Contest Soaring

11

BUILDING NOTES

Kit Purchased Date: _______________________

Where Purchased: _________________________

Date Construction Started: __________________

Date Construction Finished: _________________

Finished Weight: __________________________

Date of First Flight: ________________________

FLIGHT LOG