18
LEARNING TO USE FLAPS WITH THE CESSNA 170
The Cessna 170 was designed from the ground up to be the most
versale and fun-ying aircra possible. Pilot workload has been
greatly reduced thanks to its nely tuned aerodynamic design, and
the pre-set conguraon of the Aura 8 Advanced Flight Control
System. Pilots of all skill levels will quickly nd the Cessna 170 is a
forgiving airplane, in many dierent atudes and ight regimes.
Sharpening Your Skills & Understanding How Flaps Work
Obviously, before aempng to y with aps, you should be procient at
ying an airplane, and be comfortable ying the Cessna 170 in various
atudes.
As a short aerodyamics explanaon, aps essenally change the airfoil or
cross-secon shape of the wing, and have two primary goals or funcons
depending on the model. One, to add li (by changing the airfoil shape)
and two, to increase drag. A high-li airfoil is typically at boom, or
undercambered (boom wing prole curves in similar direcon to the
top prole). By adding ap deecon, the wing transforms into a parally
undercambered airfoil, generang more li, and more drag as a by-
product. Due to this addion of li, variances in airspeed can cause pitch
changes in the aircra when the aps are deployed. Typically with a high
wing model like the Cessna 170, the addion of ap input will cause a
pitching-up moment, as the model is not "trimmed" for that amount of
li at that parcular speed. To combat this, many experienced pilots will
use "ight mode trims" that change elevator trim with ap posion, or a
ap to elevator mix, so that this pitching up moment is automacally
compensated for. Note that it is virtually impossible to eliminate this
pitching moment at all airspeeds, but can be compensated for in the
most common airspeeds the pilot will use the aps. Quique's ap to
elevator mixing recommendaons are in the chart to the right for your
reference.
It is important to understand that this pitching moment when the aps
are deployed is normal. It is also normal for this pitching moment to vary,
depending on airspeed.
First Flights with Flaps
For rst ights, it is recommended to have two ap posions, a half
ap seng, and a full ap seng. It is also helpful to have the ap
speed slowed to about 1.5 seconds. As with learning anything new,
altude is your friend. Start at a safe altude, several mistakes high,
and begin to slow the model down. It is best if you move the
throle to the o or idle posion, and let the airplane stabilize in a
slight descent. Once the model has stabilized at a slow airspeed
and slow decent, move the ap switch to the half ap posion.
Note that the model may pitch up slightly, but quickly will stabilize
into a shallow descent again. Once the aircra has stabilized in the
half ap posion, move the ap switch to the full posion, nong
that the model may pitch up once again. Full ap, depending on
airspeed, may require a small amount of down elevator pressure to
keep it from pitching up. Note that the higher the airspeed, the
more the model will pitch up when aps are applied. It is always
best to deploy the aps at slower airspeeds unl you are
comfortable with how the model acts when the aps are deployed.
As you become more comfortable with the aps, you'll soon realize
how much they aid in short-eld takeos and landings!
My Cessna Rolls When I Deploy Flaps!
This is typically caused by ap travels that are not traveling the
same amount. This can be xed by adjusng ap linkage length,
and/or servo arm posion on the spline of the servo. Consult our
Cessna wiki page for more detailed informaon:
hp://wiki.exinnovaons.com/wiki/Cessna170
ADVANCED "3D" CESSNA SETUP
Mix %
Flap Deecon
1-9/16-inches (40mm) Flap Deecon
15% Down Elevator
24% Down Elevator
The Cessna comes with addional ap pushrods that are longer than the stock (installed) pushrods. This allows the aps to travel in both the up and down
posion, much like ailerons. With this capability, you can mix the aps with the ailerons and have much greater aileron authority in slow speed "high-alpha"
ight, and also mix in "crow" or speed brake funconality as well. Also, the aps are in the roll axis gyro loop, which allows them to correct along with the
ailerons for changes in roll. This adds extra stability at slow speeds, including landing, and 3D ight.
Should you choose to install these pushrods, you will need to re-program the Aura 8. A new Aura Cong le pre-programmed for this advanced setup is
located on the Aura Wiki page. To install, download the Aura 8 Cong Tool, and download the Advanced Cessna Setup. Follow the direcons on the wiki
page to program the Aura 8 with this cong le. Both the cong le, and Aura Cong Tool can be found here:
hp://wiki.exinnovaons.com/wiki/Cessna170
It is important to note that this advanced setup is not compable with PWM Aura connecon types. If you sll want similar capability with a PWM setup,
mixing in your transmier is required. Consult your transmier manufacturer or manufacturer's manual for further assistance.
Reference the informaon below for a basic understanding of each Flight Mode with the Advanced Cessna setup.
Flight Mode 1 - Crow
Low dual rate aileron, high dual rate elevator/rudder
Low gyro sensivity for aileron, high gyro sensivity for elevator/rudder
Rudder to aileron mix and rudder to elevator mix is OFF
Crow" with ailerons up, and aps down. Mixed to throle so that crow is removed as throle is advanced.
Throle to elevator mix to compensate for crow eects
Flaps are in the roll axis gyro loop
Aileron dierenal set with Aura
Flight Mode 2 - Sport Aerobacs
Low dual rates on all surfaces
Low gyro sensivity on all surfaces
Standard ap funcon
Rudder to aileron mix and rudder to elevator mix is ON
Flaps are NOT in the roll axis gyro loop
Aileron dierenal set with Aura
Flight Mode 3 - 3D Aerobacs
3D dual rates on all surfaces
High gyro sensivity
Flaps mixed to work with ailerons in roll
Rudder to aileron and rudder to elevator mix is ON
Flaps are in the roll axis gyro loop
Aileron dierenal set with Aura
2-3/4-inches (70mm) Flap Deecon
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