Radio Control Jets - 2009/08

I OBTAINED A valve system that I like for
actuating gear doors. Through the years,
I’ve tried many solutions to program geardoor
actuation, from air-bleed timed
systems to electronic. Some were of good
quality and some were questionable—you
know, the ones that let you down on the test
flight?
A new actuation system, which I greatly
appreciate so far, is on my bench. It is an
AirPower Smart Multi-function Valve
EVSD-5U-PRO. I got the unit with a
Skymaster ARF; the company is licensed to
sell these systems with its products.
This valve unit is electronic and
programmable, with air valves that are built
in for the landing gear retraction and gear
doors. There is also a separately
programmed output channel to which you
can attach a servo and valve.
One more thing: the brake valve is built
into this unit. All our pneumatic systems in
one block—sweet!
The EVSD-5U-PRO is housed in an
aluminum case that weighs a healthy 166
grams (approximately 6 ounces) with the
mounting bracket, air fittings, and servo wires
attached, which is not much different from the
weight of the three servos and valves it
replaces. The unit is 23/4 inches long, 2 inches
wide, and roughly 11/4 inches tall. It’s compact
for what it does.
The system has a 13/8 x 3/4-inch LCD for
program information and only three input
buttons for programming. Four LEDs indicate
which valve is open during the sequence, to
aid in programming. Operating voltage is 4.8-
6.0, and it can draw up to 650 mA maximum.
So what does the EVSD-5U-PRO really
do? Let’s start with the gear door functions:
its main purpose. The unit has four basic
operating modes.
Mode 1 is for the basic gear-door open
with struts extended. So the gear-extension
sequence is gear doors open, gear extends,
and gear doors remain open. The Mode 1
retract cycle is to retract the gear and then
close the gear doors.
Mode 2 is for all gears doors closed with
gear struts extended. The sequence for gear
extension is gear doors open, gear extends,
and gear doors close. The retract sequence
then is gear doors open, gear retracts, and
then gear doors close—basically what is
used on an F-86 Sabre.
Mode 3 is a combination of Mode 1 and
Mode 2, and this is when you need to add a
servo and valve plugged into the Mode 3
port. Mode 3 can simplify the setup on
multifunction door setup, such those on the
F-18; all timing and sequence are handled in
one place.
Mode 4 is even more flexible and is
intended for the user to customize the setup
to an even greater degree.
The EVSD-5U-PRO walks you through
all programmable values with each push of
the setup/enter button. You set the values of
each parameter in up and down increments.
These values are displayed on the LCD on
the front face of the unit; the active
parameter for adjustment blinks.
Another EVSD-5U-PRO retract feature is
a programmable pressure setting at which to
extend the landing gear before you run out of
air. The default setting is 50 psi (pounds per
square inch), but you can change it to suit
your needs. And since the unit is monitoring
air pressure, it shows the pressure on the
LCD screen for both the brake and landing
gear system.
The system also prevents gear up when
the transmitter is turned on, keeping those
embarrassing moments to a minimum. The
values can be set up to display in one of
three modes: psi, kg/cm2 (kilograms per
square centimeter), or bar (a unit of
pressure).
The brake function is the pulse type,
which is an alternative to air-pressure
regulators and has proven to be acceptable.
My BobCat has a traditional pressureregulator
valve on the brakes, and my T-33
uses a pulse brake-function actuator.
I prefer the pressure-regulator valve,
because it uses less air when light braking is
applied, but that alone hasn’t motivated me
to change out the T-33 valve, and that jet has
many seasons of flying on it. Pulse-type
brakes work exceedingly well when set up
properly.
The EVSD-5U-PRO solves the ongoing
problems we create for ourselves as we
complicate our aircraft. Whether you fly
turbines or propeller models, this item is worth
checking out; it is a cool way to set up your
airplane.
Craig Gottschang flies a large, gorgeous,
Scale A-10. He lives in Georgia, so how he
found time to build such a beauty with all that
warm flying weather is beyond me, but he did.
His A-10 is from a wonderful Mibo
Generation 3 kit, and he loaded it with detail.
Craig is uniquely qualified to know the details
of an A-10; he flew the full-scale version 20
years ago.
Craig finished his model in the colors of
“Killer Chick,” as Kim Campbell flew in
Baghdad, Iraq, in April 2003 in Operation
Iraqi Freedom. Craig’s attention to detail
needs to be seen to be appreciated.
The big smoking gun that the A-10 is built
around looks great sticking out of the nose,
ready to light them up. Craig flies his jet with
ordnance in place hanging from the wings; this
model is ready to do battle. The cockpit is
another work of art; it is complete, full depth,
and looks incredible.
Craig’s A-10 is powered by two JetCat
P120-SE turbines: big power for a big aircraft.
The model weighs 55 pounds empty, which
qualifies it for the Experimental Radio
Controlled Aircraft class. This is where it gets
interesting.
Our AMA opened up the Experimental
class to include turbine-powered models, so
now these aircraft that weigh more than 55
pounds ready to fly can be piloted at any
AMA sanctioned model event when certified.
The Mibo A-10 is marginally close to
weighing less than 55 pounds, but once it is
fully detailed, large turbines are installed, and
ordnance is added, it won’t quite stay under
the limit, so the Experimental class is the way
to go. Craig shared with me some of his
knowledge about flying in this category.
He applied for the Experimental-class
waiver with all the documentation required.
He put all of it in his aircraft-documentation
book, so reviewing it with him was a great
education.
This book is a great help to CDs when he
shows up at an event to fly; many of us are
unfamiliar with the Experimental waiver and
what information we should be checking.
Craig’s documentation is complete; it includes
his flight log, aircraft waiver, and other items
that are required to obtain and maintain the
waiver.
The details of applying for an
Experimental waiver, documentation
requirements, and aircraft requirements are
covered in AMA Document 520. Turbines are
specifically covered under Appendix A.
Read that information carefully if you
intend to build a turbine-powered model to
operate within the Experimental class. These
aircraft have different airframe requirements,
pilot-experience necessities, general setup
requirements, and required documentation,
including calculated servo power necessary for
each control surface.
A turbine-powered model is allowed a
heavier wing loading—up to 100 ounces per
square foot. But the maximum takeoff weight
is limited to 75 pounds, so don’t get carried
away.
The maximum power-to-weight ratio is
limited to less than 1-to-1. Depending on the
model, you might be left in a marginal
situation for power—especially on a twinturbine
setup when one engine shuts down.
This twin-turbine power-to-weight ratio is
normally okay for straight-wing jets, but some
of those Scale models with highly swept LEs
and low-aspect-ratio wings expect a handful
when one turbine shuts down and you have to
bring it home.
Kudos to Craig Gottschang for the
professional job he is doing operating his A-10
in the Experimental class. I hope he motivates
others to follow suit. Let’s get some big jets up
there! MA
Sources:
Jet Pilots’ Association
(904) 318-7171
www.jetpilots.org
AirPower Models
+886-2-2989-7631 (Taiwan)
www.airpowernet.com
Skymaster USA
www.skymaster-usa.com