E-flite UMX ASK-21 BNF User Manual download pdf (Page 14)

Flying

We recommend ﬂ ying your E-ﬂ ite

UMX ASK-21

outside in no greater than moderate winds. Always

avoid ﬂ ying near houses, trees, wires and buildings.

You should also be careful to avoid ﬂ ying in areas

where there are many people, such as busy parks,

schoolyards or soccer ﬁ elds. Consult local laws and

ordinances before choosing a location to ﬂ y your

aircraft. For additional tips on ﬂ ying your ASK-21,

please refer to the product page at

horizonhobby.com.

Your UMX ASK-21 can ascend on thermals and other

updrafts to prolong its ﬂ ight far beyond the ﬂ ight

time one would expect. There are many ways to

stay aloft with a sailplane, such as ridge lifts and

thermals, but we will only cover the basic thermal

in this supplement. A thermal is simply a column

of rising warm air. Once you get your aircraft into

the air using the Hi-Start or aero-tow, watch your

aircraft for a response to thermals. In a full-size

sailplane, you would feel the lift of entering a

thermal as turbulence. In the same way, watch

your aircraft for movement or rising. If the airplane

randomly rolls on its own, it is likely that you only

ﬂ ew through the edge of the thermal, causing one

side of the airplane to rise, rather than the entire

airplane. Enter the thermal by turning your aircraft

directly into it, circling to stay in the center of the

thermal. Slow your forward speed by increasing

up elevator trim so that your aircraft is moving

just faster than stall (minimum sink speed). Make

easy banking turns to ﬁ nd the area of highest lift

(the thermal’s core). When you ﬁ nd the core of

lift, tighten your turns to stay near this position.

Sometimes thermals drift downwind. It is best that

you search for thermals upwind, so that you can

follow a thermal downwind if it is pushed downwind.

With practice, you will ﬁ nd it easier to locate and

anticipate the movement of thermals.

Although thermals cannot be seen, you can

see dust, insects or birds riding an updraft. Air

movement of a thermal may be felt, so movement in

an otherwise calm spot may show you the location

of a nearby thermal. A shift in the wind (in a light

breeze) can be airﬂ ow into a thermal. Thermals are

generated by the sun heating darker ground objects

more than surrounding surfaces. The dark object

absorbs the sun’s heat, becoming warm and heating

the air above it. The heated air rises and forms a

column or funnel. Usually the base of the thermal

is small. The updraft expands and decreases in

speed as the air rises and cools. There are usually

downdrafts around the updraft, as cooler air falls

or moves less than the warm updraft. Thermals

can vary in strength, rising at speeds from a few

hundred to over a thousand feet per minute. Cooler

downdrafts around a thermal are referred to as

“sink.” Your aircraft can be pulled down by these

downdrafts. Prevailing wind can aso bend or break

a thermal from its heat source

so that a warm air bubble travels

downwind as it rises with little or

no attendant downdrafts.

Landing

Be sure to land into the

wind. Due to the high lifting

efﬁ ciency of the sailplane design, landing requires

a large landing area clear of trees, buildings and

cars. While on your downwind leg, remember

that the sailplane glides much better than other

aircraft. You will need to setup for landing, lower

and with a more shallow decent than you may be

used to. As you are on approach for landing ensure

that the model is descending slowly, but also not

accelerating. If the model is accelerating, it is likely

that you will overshoot your projected landing area.

Maintain this descent and speed, and, as the model

nears the ground (approximately 6 inches (15 cm)),

slowly apply a small amount of up elevator. The

model should level out and ﬂ y parallel to the ground

and begin to decelerate. Be sure the model does

not climb. As it decelerates, keep ﬂ ying the model

parallel to the ground until it comes to rest gently on

the landing gear.

Low Voltage Cutoff (LVC)

Due to the aircraft having no motor and the small

power needs of the sailplane, you may not know you

have a low battery until controls fail. We recommend

setting a timer for 25 minutes.

Do not attempt to ﬂ y or operate any longer than

25 minutes on a battery.

Repairs

NOTICE: Crash damage is not covered under

warranty.

Repair this model using foam-compatible CA glue

or clear tape. Only use foam-compatible CA glue

as other types of glue can damage the foam. When

parts are not repairable, see the Replacement Parts

List for ordering by item number.

For a listing of all replacement and optional parts,

refer to the list at the back of this manual.

NOTICE: Use of foam-compatible CA accelerant on

your model can damage paint. DO NOT handle the

model until accelerant fully dries.

Flying Tips and Repairs

Wind

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E-flite UMX ASK-21 BNF User Manual Page 14

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