Getting Started: Help for RC Plane Newbies

Getting Started: Help for RC Plane Newbies
GETTING STARTED
HELP FOR RC
PLANE NEWBIES
Hangar 9 Alpha powered by an OS 46 SX 2-stroke.
Mike French photo.
Compiled by Pat Rose, Servo Chatter Editor
Oct. 19, 2007
Hello RC Plane Newbie,
Greetings to all of you that are new to the radio controlled airplane hobby. While meeting new
or prospective new members at the SCCMAS field, I often found myself referring to articles
found in past issues of our club newsletter Servo Chatter. So to make things easier for everyone, I started this project with a list of contents, thinking I would simply pass out the list, referencing past issues of the newsletter. After making my list, I got ambitious and decided to put
this document together with the contents reflecting subjects that would be helpful to the RC
newbie. I borrowed heavily from the works of Mike French, Tim Jones and Michael Luvara; not
all the contents having been previously published in Servo Chatter.
Hopefully the contents of this publication will help you overcome some of the hurdles to becoming an accomplished RC pilot.
Enjoy,
Pat Rose
Editor, Servo Chatter
Table of Contents
What I learned in my SCCMAS Primary Flight Training……………………..………...3
Lessons for a new RC Flier…………………………………………………………….…5
RC Plane Control Inputs…………………………………………………...……………...6
Preflight Model Aircraft Inspection Criteria & Guide………………...………………….8
Recommended Equipment……………………………………………………………....10
More Lessons for Veteran Beginners…..…………………………..…………………..11
Don‘t aim it at the Plane………………………………………………...………………..12
2.4 GHz Radio Introduction…………………………………………...…………………15
Trimming a Sport Plane………………………………………………...…………...…...17
Reliable Engine Operation and Flight Trimming Notes…………………...…………..20
Getting Started Help for RC Plane Newbies is published by the SCCMAS “Tomcats” radio control club located in
Morgan Hill, CA. Views expressed are those of the writers. They do not necessarily represent the views of the
club, its members, or officers. Mention of any product, material, or service shall not, nor is it intended to, imply
approval, disapproval, or fitness for any particular use. The SCCMAS is a non-profit organization. Permission is
granted to reproduce anything printed in here as long as the source and author are credited.
2
What I learned in my
SCCMAS Primary Flight
Training
By Anand Phatak
To fly a model airplane was something I had always wished since the time I saw a model air
show back in my school days. It took me 20 years,
however, to actually get into it. A tiny electric plane
purchased by a friend inspired me to finally pursue
this childhood dream. I started researching the
clubs in the area and discovered SCCMAS on
Google. One of the clubs benefits was free training. It had not occurred to me until then that this
hobby needs a good amount of training. I picked
up the phone and called the club. I was expecting
a voice mail but actually got to speak with the
president! He gave me good advice to visit the
club and to see everything in person to get an idea
of what to expect. I drove to the club and was very
happy to see this wonderful facility. People were
friendly and guided me as to how to obtain an airplane and contact the club's instructors. I called
Mike French, the director of flight instruction He
willing agreed to become my instructor.
off and land on it. But I was dead wrong. I had
never expected that flying R/C plane was quite so
challenging and involved many safety precautions.
I didn't know each plane has a "personality" which
you need to get accustomed. I didn't know altering
small settings to the control surfaces could have
such a big impact on the flying characteristics. I
didn't know how to deal with wind speed, wind
gusts and direction. An untrained R/C pilot can be
a big threat to his plane, to himself, to others and
their planes on the field. I was about to discover
and learn all this throughout my training.
Mike had emailed me an aircraft-readiness check
list prior to the first training day. I followed the instructions, prepared my NexStar trainer to the best
of my ability, and was quite happy with the result.
Having a Mechanical Engineering degree, I
thought that this would piece of cake.
On each instruction day, I learned something new.
Mike explained each aspect in great detail: The
importance of "TRACK" - a model pilot's preflight
check acronym - (which helped me detect a big
flaw in my plane at a later date which undoubtedly
saved it from crashing), battery voltage checks,
checks on the linkages, cracks, importance of
not spilling fuel on the field, sensitivity of the controls, recovering from disorientation... the list went
on.
I met Mike at the field on the first day. I was all too
eager to get my plane into the air and do my first
aerobatic maneuver. We started by inspecting my
aircraft. My plane went through serious scrutiny.
He pointed out at least 10 hazards to flight with my
plane. That came as a shock! And I thought my
plane was fit enough to carry live passengers. But
I couldn't disagree with anything he had noted. He
explained everything to me in great detail and I
agreed (fo) go back and make the repairs. We
didn't however discard my machine completely as
we flew my plane‘s maiden flight that day.
What I Learned continued on page 4.
I had thought it would take me 3 to 6 lessons to
become a good pilot. After all, it is just child‘s play,
isn't it? I had bought a flight simulator. I could take
3
What I Learned continued from page 3.
learning curve. When you learn to how to take off
and land, maintain your plane, know how to save it
from disasters (most of the time) and fly it safely,
there is a great deal of fun here! When you do
your first aerobatic maneuver, land your plane with
style, save it from a dead-stick landing, you suddenly discover the treasure. It's all fun after that.
But what good training could give you is a life-long
ability of sustaining and enjoying this great sport.
Learning it right the first time is the best way. I am
grateful to SCCMAS and Mike French who has
given me that opportunity. - AP o
Sure, at times I was too eager to fly and start
seeking fun from this new exciting hobby, rather
than practicing the essential details. But soon I
started to realize the unforgiving nature of our
sport. You cut corners and you lose your plane.
Worse, your plane could be a threat to others on
the field. All this started becoming clearer with
each session. So where was the fun factor in leaning to fly models you might ask? After all
we pursue hobbies because they are sources
of great pleasure. I learned that in this hobby the
fun part arrives after you pass the first part of your
4
Lessons two and three lead to a whole new book
of lessons. These lessons include propeller replacement, application of band aids and sometimes an enhancement to one‘s vocabulary of
word you don‘t say around mom. Also included
are impromptu lessons in small wood parts fabrication and reinforcement. Lessons in gluing these
fabricated and reinforced parts together. Lessons
in removing one‘s glued fingers from these glued
parts assemblies. Lessons in applying covering
material. These may be large or small lessons,
depending on your share of gravity for the previous day. I‘ve seen some lessons demonstrating
techniques in tree climbing of all things! The possibilities for lessons for the beginner are endless.
Lessons For a New RC
Flier
By Tim Jones
This hobby, or sport if you will, has just been a
kick for me. I‘m fairly new to flying Radio Controlled model aircraft. I‘d built and destroyed several control line planes as a youngster. The most
recent when I was 22, a youngster compared to
my present age.
Getting into this hobby at the RC flying level was a
bit of a jump. When I was a youngster, Radio Control was the ultimate plateau. Now I‘m in it. I
started hanging around the SCCMAS field around
the early part of 2002. Done playing with hot rod
cars, my kids nearly grown, my house virtually
rebuilt, I was looking for something to entertain
me. I tried golf. It‘s entertaining at the time I‘m
playing the game, but, that‘s about all. Hunting
took too much planning, preparation and driving. I
decided the flying field was it. I was buying a
plane, an AMA card and a club membership.
One of my personal favorites is the lesson of sharing your learning experiences with a group of new
friends and enjoying a good laugh with these
friends sometimes at your own expense. Damn,
this is fun. And we won‘t even go into the first introduction to racing. That can make you laugh
hard enough to hurt yourself.
I‘d like to see a few lessons presented at a group
level, such as a club meeting or a notified day at
the field. I‘d like to see some beginner lessons
presented. Examples? How about a demonstration for beginners for the uses of various glues
and accessories. Like glues or bonders if you will,
debonder, accelerator or kicker. Epoxies and additives for fillers and strengtheners. Cleanup tips for
both. How about a little talk for propeller selection.
Balancing of propellers. Differences or effects of
pitch, diameter and blade profile selection. Glow
plugs? What‘s the difference? Battery care?
Maybe a covering demonstration. How about adding trim and detailing to your covering. Balancing
of planes. How about a demonstration at the field
for various maneuvers to learn?
From that day on, I‘ve had a great time. My choice
was a Hobbico Avistar. I ordered everything at the
same time, on the same day. Ready to Fly airplane, AMA membership (by Fax), and a club
membership. I scared up some of my old glow fuel
supplies and went to Sheldon‘s to get a few more.
When my plane arrived, I was as excited as the
day I got my learner‘s permit to drive. This was
going to be great. I had my AMA faxed confirmation, my new untried club card and a new airplane.
The lessons were about to begin.
The first lesson I learned, those who fly model airplanes will teach someone else to fly model airplanes. All those who fly have their own way of
teaching others. All are helpful.
These are just a few thoughts I have. I‘ve gotten a
few answers. I‘ve shared a few discoveries. I‗m
still working on that gravity thing. I sense more
laughter coming. From one beginner and maybe
several others, thanks for the lessons Tomcats,
and keep sharing. o
The second lesson, gravity is constantly working
against you. I personally feel that gravity is unfairly
biased against the new flier. (Reggie doesn‘t get
his fair share of gravity.)
Third lesson, propellers are very hard on human
flesh. A starting stick of any kind is better than
your finger. And of course, the electric starter is
the best way to go.
5
RC Plane Control Inputs by Pat Rose
Figure 2. Left stick moved forward by
RC pilot. This throttle input powers
the plane forward. Guest does not
touch left stick unless directed by RC
pilot.
Figure 1. Controls at engine idle
(left stick) and neutral (right stick).
Figure 4. Right control stick pushed
forward—plane pitches down.
Figure 3. Right control stick pulled back—
plane pitches up.
6
Figure 5. Right control stick moved left.
Plane banks left.
Figure 6. Right control stick moved
right. Plane banks right.
Note: Figures 2 thru 6 show control movement exaggerated. Only small movements
(1/16 to 1/8 inch) are usually needed.
To gain altitude, see Figure 3.
To lose altitude, see Figure 4.
To turn left, bank left (Figure 5), neutralize controls (Figure 2), pitch up (Figure 3),
neutralize controls (Figure 2), bank right to level wings (Figure 6), neutralize controls
(Figure 2).
To turn right, bank right (Figure 6), neutralize controls (Figure 2), pitch up (Figure 3),
neutralize controls (Figure 2), bank left to level wings (Figure 5), neutralize controls
(Figure 2).
Have fun!!!!!!
7
Preflight Model Aircraft Inspection Criteria & Guide
By Mike French
The following document is an unofficial guideline to serve as a basis for inspecting aircraft for safety and
other operational needs prior to flight. This list is not offered as being all-inclusive but attempts to cover the more
common problems found on aircraft that come to fly at the SCCMAS field for the first time. Preliminarily inspect
your aircraft while checking off the boxes. Bring this completed checklist when you come for your aircraft inspection and orientation session.
Internal Antenna
The aircraft antenna should be placed internally to the aircraft and not attached to the tip of the vertical stabilizer. The reason is to allow free access
to the empennage by a tie down rope which will be required for operation in
the startup area. Antenna should exit the A/C at bottom rear.
Nose Wheel Drag
The nose wheel must NOT rotate freely. Drag is needed on the nose wheel
to inhibit the aircraft from taxiing at optimum engine idle RPM. Thin fuel
tubing on either side of the nose wheel works well.
No Single Point Failures
Post control horn attachment provided in many current trainers secure the
push rods with only one set screw. Either replace the posts with a clevis pin/
adapter combination or secure the set screw/push rod with a light coating of
Loctite.
Gas Tank Security
Some trainers do not properly secure the gas tank in the aircraft. The gas
tank must be rigidly attached to the fuselage. Glue plywood strips to the fuselage with foam separating the tank from the strip to prevent abrasion.
Main Wheel Collars
Some trainers secure the main wheels to the landing gear with a brass collar
secured only by a setscrew. At a minimum Loctite the collar and setscrew.
Recommend that the collar be removed and replaced with a length of fuel
tubing on either side of the main wheels.
Battery Charger Port
We recommend that a battery charging port be installed on the opposite side
from the muffler such that the battery voltage can be monitored prior to each
fight instruction session without the removal of the wings. A three flight
training session would proceed if battery voltage at the start of the session
exceeds 5.0 Volts. No individual flight should start with less than 4.8 Volts.
Bands Around Clevis Pins
All Clevis pins should have a thin band of fuel line surrounding the part to
prevent loss of linkage with the control horn.
Secure Control Surfaces
All control surfaces should move without slack to their control servo. We see
many instances of control surfaces not well attached to the aircraft.
Minimum Length Fuel Line
Keep fuel line length to an absolute minimum. No arching curves of fuel line
between the tank and carburetor.
Secure Engine Mounts.
Engines should be directly fastened to the aircraft’s engine mounts. Engine
clamps are to be discouraged. Drill holes in the engine mount and use an
appropriate tap to create threads. 6-32 bolts 1 ½ inches long work well for
engines of .51 cu in or smaller.
Preflight Model Aircraft Inspection continued on page 9.
8
10 or 11 / 4 or 5 Props
Trainers are not flown for speed. Keep the propeller’s pitch low as what is
needed is torque and not speed. Bigger engines require longer props.
No Floating Electronics
Some trainers secure the receiver and battery with Velcro tape. This is discouraged as Velcro has a tendency to unhook in flight. Batteries particularly
need to be properly secured to the aircraft. Use a cable tie if necessary but
directly secure both the receiver and battery to the aircraft.
Labeling
The pilot’s name, address, phone numbers and AMA number need to be
placed permanently both on the aircraft and the transmitter prior to brining
the aircraft to the field.
Channel Numbers
The channel number for the transmitter should be easily seen on the antenna.
Be sure that your channel numbers are secured to the transmitter’s antenna.
Tie Down Rope
Be sure that you have a 5’ tie down rope with a clip to attach it to the fence
such that the aircraft can be started without fear of it moving.
Label Support Equipment
Engine starters, glow plug starting batteries and fuel kits should have your
name on each item. We collect too many nameless support items.
Needle Valve Extension Wire
Fabricate from a 1/16” wire a 1½ “ extension to the needle valve of your
engine. Most engines have a hole drilled in the end of the needle valve with
a right angle Allen head set screw to secure the wire. Add a 90º ¼” bend and
then place a little epoxy [JB Weld] on the end of the wire to prevent a hazard
from stabbing yourself while attempting to adjust the mixture setting on a
vibrating engine. The extension helps keep fingers from being prop sawed.
Closed Loop Fueling
When you fill the gas tank of your aircraft, there must be a return line from
the aircraft overflow back to the gas container. When the aircraft tank is
filled, we do NOT want to find gas has been splattered on the asphalt. The
caps to gas tank fueling systems have a return port. Be sure that yours is connected and operational.
Exhaust Port To Vent Over Wing
Rotate the exhaust port vent such that the exhaust gases and oil are throw
AWAY from the fuselage and OVER the top of the wing as much as possible. The object here is to minimize the oil-laden gases from seeping under
the wing into the chamber containing the electronics and servos.
Adjust Throttle Linkage To Cut Off Adjust the throttle servo and engine linkages to effect complete cut off with
the throttle lever at minimum and throttle trim at it’s bottom most travel.
Cutoff occurs when ALL the arc of the rotating throttle assembly is hidden.
Buddy Box Cable
Be sure that you have a Buddy Box Cable for/with your transmitter.
SCCMAS has a few cables that might serve in a pinch. But like your
toothbrush, it is best to have your own that matches your particular transmitter. SCCMAS has plenty of Buddy Box Transmitters that can be used by the
student. The student transmitter has the standard round ended connector for
the cable.
Preflight Model Aircraft Inspection continued on page 10.
9
Flight Simulator
There are many good flight simulators for your PC. The best one that I have
used is produced by Great Planes, Inc. Real Flight, Generation 2 (G2) is excellent. Look at http://www.realflight.com/g2_main.html. I have had good
success with it. It is a little bit pricey but it is worth it. A flight simulator will
reduce your training time by more than half and have uses after you pass
your solo pilot’s test. I still use mine from time to time.
Equal Nose Gear Deflection
The nose gear control arm must not be parallel with the firewall. It must be
connected to the main gear at roughly a 30º angle so that control rod can
deflect the nose wheel equal angles about the A/C center line.
Fuel:
Recommended Equipment
Condensed from Michael
Luvara‘s Manual
Fuel comes in many brands and types. Please see
what your particular motor manufacturer recommends. In general, 5% to 15% (percentage
is amount of nitromethane in fuel) is commonly
used in regular sport motors. Fuel is composed of
methanol, nitromethane, and a mixture of synthetic
or castor oil for a lubricant. Please avoid spillage of
excess fuel onto any area of the field and use an
overflow bottle to collect excess fuel and protect
the asphalt. In the course of a day’s flying, you can
save a tank or more of fuel.
Aircraft & Kits:
With today’s ever changing Radio Control market,
there are many kits and almost ready to fly (ARF)
aircraft available. We recommend any .40 to .60
size high wing trainer which has a flat bottom or
semi-symmetrical wing.
Engines:
Radios:
In purchasing an engine, there are two types - two
stroke and four stroke. We recommend a two
stroke. They are available with ball bearing or
bushing supported crankshafts. The ball bearing
versions put out more power, and are somewhat
more expensive than the bushing versions, but either work fine, provided they are the right size for
your airplane. Engines must be equipped with mufflers. Those using gas engines at any time should
carry a fire extinguisher with them to the field.
Selecting a radio can be a confusing part of entering the Radio Control hobby. There are many
brands available and everyone likes a different one
for one reason or another. Radios must have
trainer cord capability.
Field Equipment:
Glo plug ni-starter (1.5 volt battery used to ignite glo
plug)
Chicken stick or electric starter
Propeller/glo plug wrench
Extra propellers
Misc tools (screwdrivers, wrenches, pliers)
Glue (for small field repairs)
Extra glow plugs
Fuel pump (manual or electric)
Overflow Fuel container
Cleaner for hands and airplane
Field box to hold all of the above.
Propellers:
APC is the most common propeller used for training. This is because the props are made of glassfilled nylon and can take some abuse from hard
landings. Wood props are a lot safer when being
used, but will break on a bad landing. Propeller
sizes will be outlined with your motor’s manual.
Use a spinner or propeller safety nut on your motor.
10
Wendy.)
More Lessons for Veteran Beginners
I‘ve learned that it is not uncommon to have several spare engines, airplane ARF kits, servos and
receivers, just in case the urge hits you to put
something together. I‘ve learned that if you have
several of the same spare prop, they will be with
you at the field in your box. But if you have only
one spare for the plane you took with you on any
given day to the field, it will be at home on the
bench. If, while you‘re driving to the field, you
wonder if you remembered your transmitter, you
have a fifty – fifty chance that you have it with
you. If, however, you think about it and are sure
you remembered it, you will have to go back
home to get it or enjoy the day ―Hangar Flying‖.
By Tim Jones
I‘ve been learning lessons, as I‘ve written earlier,
from the moment I gave serious consideration to
giving this hobby a shot. So, I‘ve been having fun
with this for a couple of years now. As I‘m still a
beginner in many aspects of this hobby and I‘ve
got a couple of years now, I consider myself a bit
of a veteran and a beginner. So, ―Veteran Beginner‖.
I‘ve learned that there is always a deal somewhere at the swap meet. These deals will often
present the opportunity to work that talent for the
twisted justification for bringing another project
home. I‘ve learned that E-bay and Tower Hobbies are not good places to browse around when
you have idle time. You‘re much better off using
that time to assemble one of the kits you already
have, or repairing one of the planes you‘ve set
aside to repair another day. I‘ve learned that if
everything you have is repaired or built, your
computer internet connection will be down, so
you can‘t browse for another project. So, you
have to buy something while you have the opportunity, just in case.
The basic beginner lessons are still there. I‘ve
improved on them. I haven‘t dinged my finger
with a prop in a long time now. But I do continue
to glue my fingers to balsa wood. I continue to
see that veterans enjoy and helping a beginner.
But if a ―Veteran‖ of any caliber, messes up a
take off, steps on his antenna, flies off with the
glow driver still hanging on his plane or snags a
bowling ball in the safety net, there is no mercy in
nominating him for Dumb Thumb. I‘ve gotten several dumb thumbs already. I feel ―Accepted‖. I
consider Dumb Thumb a badge of honor. Every
Dumb Thumb has a good time attached to it. I‘ve
improved my talent for applying covering. But my
choices for color section have a ways to go. I
continue to enjoy sharing laughs at the field. The
more time I spend at the field, the more I get to
laugh, often at myself. The trees at the south end
are still taller and closer than they appear. The
weeds are often taller than they appear. Sometimes, the runway is shorter than it appears.
These are some of the lessons learned in the
very beginning. They continue to be very valuable lessons.
Overall, all of the lessons are fun. Helping a new
flier at the field get signed off and watching him
smile when he successfully completes his first
one hundred percent solo flight is one of the most
rewarding experiences in the hobby. I‘ve found
that there is no word that can truly describe the
feeling of a greased tail dragger landing on the
mains and flying the tail down the runway for a
soft tail set down and taxiing back to complete a
flight.
Now for the more lessons part. I‘ve learned that
there is some truth in the saying that you can‘t
have too may planes. Though this is a debatable
statement and hard to defend, it appears to be
true. Somehow, I always have some twisted justification in buying another plane. I‘ve learned to
work different angles in explaining this justification to my wife, although, it is getting tougher to
do. I‘ve learned that the dining table is not a
place to store parts, assemblies or materials, or a
convenient place to work on propeller balancing
or fitting engine mounts. (That one was for
I‘m learning more lessons. I‘m getting into racing.
I‘ve got twelve points on the series so far. But,
that‘s another list of lessons.
Stay tuned……………………..o
11
Don’t aim it at the plane! By Walt Jellison
The following article copied from Peak Charge, the
monthly newsletter of the Silent Electric Flyers of San
Diego, March 2006 issue.
Did you know that the thirty-to-forty inch (quarter
wavelength) antenna on our radio radiates essentially ZERO radio energy in the direction pointed?
Maximum energy from a quarter wavelength antenna occurs at a right angle (90 degrees) from
the axis of the antenna. There is an almost
straight line relationship between energy transmitted (or received) and the angle from the antenna
axis. It starts at zero output in the direction of the
antenna‘s axis, then it goes up to a maximum at
90 degrees from that axis.
Ever had the situation where your plane is flying
just fine and you are coming in low for a landing
when all of a sudden the plane does something
really weird….totally out of your control? You
probably thought your plane received a radio interference ―Hit.‖ More than likely, you caused the out
-of-control situation by pointing your transmitter‘s
antenna at the plane.
Just last week, at our flying field I saw a fellow
totally destroy a beautiful pattern plane when it
violently augered into the ground. The plane had
been flying low, toward the pilot, and the pilot was
pointing his transmitter antenna at his plane.
Since the plane‘s receiver antenna was basically
streaming along the plane‘s centerline, both transmitter and receiver antennas were, for the moment, pointed at each other resulting in total loss
of communications...and of course, any control of
the plane.
So now when you are flying, especially when coming in on a low approach for landing, be sure to
position your antenna at a right angle (or at least
45 degrees—ed) to the plane. Do this every time
and you will likely never again be plagued by a socalled radio ―Hit.‖
Following photos by Pat Rose. I‘ve been meaning to put together something like this for some time,
and Walt‘s article got me started. Walt gives an excellent explanation of this antenna aiming subject.
Figure 2
Figure 1
Here the transmitter antenna is pointed directly at the departing and arriving plane, with the plane‘s
antenna (in the fuselage) in a similar pointing arrangement. This is the worst possible situation.
12
(Antenna aiming, continued from page 12.)
Photo 4
Photo 3
Photos 3 and 4 illustrate at least one antenna (receive or transmit) at 45 degrees to the other.
This situation is better than photos 1 and 2.
Photo 6
Photo 5
Photo 5. A transmit antenna position better
than photos 1 and 2.
Photo 7
Photo 6. Antennas oriented for maximum received
signal, just like photo 7. Best arrangement.
Photo 8
Photo 7: Antennas oriented for maximum received
signal, just like photo 6. Best arrangement.
(Continued on page 14.)
13
Photo 8: Here the transmitter antenna is pointing
above the plane, a preferred position relative to photos 1 and 2. Aiming below would be equally good.
(Antenna aiming continued from page 13.)
There is one more characteristic about antennas
that needs explanation. Just as Walt explains that
pointing the transmitter antenna at the plane cancels the transmitted signal towards the plane,
there is a characteristic described as polarity that
can have a similar effect. Photos 6 and 7 illustrate
what is called horizontal polarity for both the transmitter and plane antennas. Maximum signal is
received by the antenna in the plane when both
the transmit and receive antennas are similarly
polarized; both horizontal or both vertical.
pointing up, down, right and left. From one range
check to another, keep the plane oriented at a
similar angle to the transmitter for consistency.
Also, if you experience a ―Hit‖ while flying your
plane, immediately reorient your transmit antenna
(I know, things happen real fast). You just may
be able to save it. One more thing. If you have a
large plane, run the receiver antenna both vertically and horizontally as space allows. For instance, straight back through the fuselage and up
into the vertical fin.
PR o
The bottom line is this: When performing a range
check, move the transmitter antenna around—
14
2.4 GHz Radio Introduction
By Pat Rose
(This message leverages heavily from Mike Luvara‘s article The 2.4 GHz Phenomenon in the
May 2007 issue of Servo Chatter.)
What is frequency, and BTW what is a radio?
Think of a grandfather clock which has a pendulum that swings back and forth at a rate of one
swing to the right followed by one swing to the left
in one second. This clock‘s pendulum is operating at a frequency of 1 cycle per second, also
known as 1 Hertz. So, let‘s assume we have an
electronics circuit that operates at 72,000,000
Hertz—we‘ll call this 72 Mega Hertz or 72 MHz.
This happens to be a frequency of operation to
which we can connect an antenna and transmit
electromagnetic energy into space. To receive the
transmitted frequency, it helps to have a receive
circuit that is tuned to the same frequency as the
transmit frequency. A transmitted signal operating
at 72 MHz or higher is considered a ―radio frequency‖, because it takes a radio with tuned circuits to transmit and receive the signal.
Digressing a bit, assuming you are using a 72
MHz transmitter and you forget to extend the antenna—what you have is an antenna set to the
wrong length for the frequency. Therefore much
less of the signal strength is transmitted and you
end up with a plane that is out of control soon after
take off.
Digressing even further, see the July 2006 issue
of Servo Chatter for an explanation of signal
strength versus antenna orientation. The same
principles apply to the 2.4 GHz radios.
Our 72 MHz radios transmit between Channel 11
(72.010 MHz) and Channel 60 (72.990 MHz) - we
usually choose the frequency when we purchase
the radio. Note that these conventional radios
transmit on one and only one frequency. If two
transmitters are turned on simultaneously with the
same frequency, ―Houston, we have a problem.‖
The receivers installed in both airplanes are confused by the two simultaneous identical frequency
signals and communication fails.
Radio frequency emissions have a characteristic
wave length that is inversely proportional to frequency*. In other words, the higher the frequency,
the shorter the wave length. A 72 MHz signal will
have a wave length of about 402 centimeters, contrasted with a 2.4 GHz signal with a wave length of
12.5 cm. (2,400,000,000 Hz = 2.4 GHz). It turns
out that antennas for our RC radios work well to
transmit their signal when built to 1/4 wave length.
So a 72 MHz antenna would be about 100 cm and
a 2.4 GHz antenna would measure about 3.1 cm.
This explains the differences in antenna lengths
used between the conventional 72 MHz radio and
the newer 2.4 GHz radios.
The 2.4 GHz ISM frequency band includes all frequencies between 2.4 and 2.5 GHz, a span of 100
MHz. This band is wide open and is utilized by
such applications a microwave ovens, telephones,
WiFi, and model airplane control. There is literally
a ―storm‖ of products using this frequency spectrum. There are two main frequency utilization
schemes in use today in the RC hobby. First,
there is the technique which finds two unused frequencies, then locks on these two frequencies.
One frequency is used for the primary control of
the model, and the second frequency is used if
interference is encountered on the primary channel.
It turns out that the receive antenna follows the
same rules as the transmit antenna, so you will
notice that the 72 MHz receiver antennas are
much longer than the new 2.4 GHz receiver antennas.
Notice in the photo of the Futaba radio how short
the transmitter antenna is compared to one of our
usual 72 MHz radios.
2.4 GHz Radio Introduction continued on
page 16.
15
2.4 GHz Radio Introduction continued
from page 15.
field are seldom seen using them; it would be a
tough sell to enforce this rule.
One more final note: You will notice the 2.4 GHz
receivers have at least two antennas. As explained earlier in the July 2006 issue of Servo
Chatter, there is a difference in received signal
depending on how the transmit and receive antennas are oriented. This effect gets worse as frequency increases. To work around this issue, the
2.4 GHz receivers use at least two different receive antennas with the goal that one of them will
have a better orientation relative to the transmit
antenna. O
The second scheme in use is the spread spectrum
technique which uses only one frequency - this
frequency changes every 2 milliseconds (0.002
Sec) within the 2.4 GHz ISM band. Therefore frequency conflicts are short lived and there is essentially no signal
interruption. (Disclaimer:
spread spectrum technology is diverse and constantly changing.)
Since the operating frequency is constantly changing, it makes no sense to use frequency pin control for these radios. However, the AMA recommends that a 2.4 GHz pin is used when flying with
these radios. Even though the AMA recommends
2.4 GHz frequency pins, RC pilots at the Tomcat
2.4 GHz Receive Antenna Orientation
Now that I have your attention relative to frequency
versus antenna length, I might touch on one more item.
Just as the Earth can shade the moon from the Sun’s
light rays and cause an eclipse of the moon, a similarity
can be imagined with the 2.4 GHz radios. With the
orientation of the RC plane pointed directly at the
transmitter, toward the pilot, the engine (a big hunk of
metal) or other electrically conductive parts (as in retracts or carbon fiber) can “shade” the receiver antenna
(s) from the transmitter signal and possibly cause temporary loss of control. No doubt the radio designers
have spent countless hours working around the issue of
received signal strength. Anyway, as soon as the plane
changes direction because of this loss of control, the
receiver antenna(s) is once again exposed to the RF
signal and control is regained.
With the small size of the 2.4 GHz receive antenna, it is
especially important to keep them away from other
conductive material such as servo wiring, the battery,
etc., or at least orient the antenna at 90 degrees to the
nearby wiring. O
16
Trimming a Sport Plane (assumes you are using a computer
radio)
By Pat Rose
I use the following procedures to trim my planes.
By ―trim‖ I mean making adjustments to the plane
and transmitter that make the plane easier for me
to fly (goes where I point it) and has fewer bad
habits. Hopefully, you may find some value in my
experience, so here goes. The sequence of making the trim adjustments does matter. The following is typical of the trims I have used on my 46
size U-Can-Dos (I‘m building my fourth one), 90
size 3D Mayhem, 90 size Cub, and most recently
my 60 size Edge. It is always suggested that flying adjustments be made on a calm day, but since
mother nature seldom cooperates, you‘ll just have
to do your best. The following assumes that a first
flight has been made and control response and
neutrals have been adjusted.
nant heavy side. My Edge required about one half
ounce on the left wing tip, the tip opposite the
weight of the engine.
Battery placed here
to achieve proper
CG. Balsa box constructed to hold battery.
CG
The first ―trim‖ adjustment on a plane is the CG.
Try to achieve CG balance by moving the battery,
receiver, servos, and etc. without adding any
weight to the plane. These adjustments can require a lot of creativity to come out right. I would
recommend the plane builder (ARF or kit) to use
the CG recommended on the plans. In the case
of my recently completed Edge, I put the CG right
in the middle of the recommended range. Move
the CG past the rear limit of the recommended
range and watch out, your plane may have some
nasty snap habits. I‘ve done this once by mistake
and wound up performing a snap on landing.
Ouch! The plane landed upside down. On my UCan-Do, the CG is near the rear limit as explained
in the manual and flies well, snapping and rolling
on demand, but still landing easily.
Dynamic Balance
This step checks the planes‘ balance during flight.
Take the plane up high, chop the throttle and put
the plane in a dive. Pull the plane level at a convenient height and watch for a wing to dip. Perform this check several times before adding or
deleting the stick on lead weights. With my Edge,
this step was not needed as the plane was balanced.
Engine Up/Down Thrust
A plane that is not properly adjusted for up/down
engine thrust will have some exciting habits on
landing when the throttle is adjusted back. To
check for engine up/down thrust, fly the plane in
the up wind direction from left to right or right to
left with full throttle. Just before the plane is directly in front of you, chop the throttle to idle. The
plane should continue to fly without pitch change.
My last U-Can-Do had a nasty engine down thrust
built into it so that on landing, with engine adjusted
to idle, the plane would balloon up and I would
have to fight the plane and apply down elevator.
It was obvious that engine down thrust was holding down pitch; when the throttle was cut, the
plane‘s trim flew the plane up. To solve the problem, I loosened the screws that hold the engine
Lateral Balance
This is the adjustment I believe that most new
builders forget to make. A plane that isn‘t balanced will dip a wing (among other things) on
landing. The wingtip of the plane that is the heavier side is continually getting scuffed and torn up
on landing. I make both a static balance adjustment described here and later check balance with
the plane in the air. To check the lateral balance
may require two people. One person supports the
rear of the plane in the rudder hinge area and the
other person balances the front of the plane on the
prop nut. Lift the plane and watch the heavy wing
dip. Add stick-on lead weight in small increments
to the light wing tip until there is no longer a domi-
Trimming a Sport Plane (continued on page
18)
17
also a yaw to the right. Aileron differential is
achieved by making adjustments to your radio,
assuming each aileron is on a different channel.
The up direction aileron is left at the recommended movement, and the down direction aileron is adjusted for less than 100% movement
compared to the up aileron. To see the adverse
yaw, do one of the following: (1) Fly the plane upwind and when in front of you, roll the plane left or
right with aileron, or (2) Fly the plane upwind and
when in front of you, pull up at about a 30 degree
angle and then roll the plane left or right. My Sig
Mayhem required almost no differential while my
Edge required about 70% down aileron (30% differential) (I‘m still not sure this is right, but the
plane tracks well.) My Cub required about 60% on
the right aileron and 70% on the left aileron.
Trimming a Sport Plane continued from page
17.
mount to the firewall enough to slide in small
pieces of 3 x 5 card stock between firewall and
lower engine mounts. To achieve multiple layers,
accordion fold the paper. Some people use metal
washers. The U-Can-Do required several attempts
at this adjustment because the plane was built
with way too much down thrust. Don‘t forget to
use a small drop of blue thread locker on the engine mount screws to keep things from coming
apart.
Engine Right/Left Thrust
Flap Trim (wing incidence)
If you have followed the above adjustments in sequence, the plane is starting to show well behaved
tendencies. Now fly the plane downwind, turn
around and ease into the knife edge. Ideally the
plane will track straight and true. However, it is
common for the plane to pull towards the canopy
or push toward the landing gear, both situations
can be a little exciting to correct with the elevator.
Now fly the plane upwind and make the same observation. If the plane pulls, land and adjust both
ailerons up by one half turn on its clevis. If the
plane pushes, adjust both ailerons down. Make
this adjustment carefully as all my planes have
required less than two turns of the clevis. Expect
the need to trim the elevator for level flight each
time you make this adjustment. Surprisingly, my
Edge required no adjustment here; while my UCan-Dos all required some adjustment.
Note spinner offset to right.
This adjustment assumes an engine thrust to total
weight ratio of 1 or better which allows unlimited
vertical climb performance. Fly the plane up-wind
until just in front of you and pull up elevator for
vertical flight. Make one or two quick adjustments
so the plane is flying with its canopy towards you
and straight up. Now watch. My Edge started to
pull left immediately and required a lot of right rudder trim. Adjustments to the plane are made in a
way similar to engine up/down thrust with card
stock but to the left or right motor mount. Three
layers of card stock were installed under the left
mount, the rudder trim set to zero, and once again
into the air. I‘m flying now with five more layers of
card stock for a total of seven layers of right thrust.
Rudder to Aileron Mixing
To view the negative aspects of flight without this
mix, fly upwind and when the plane is just in front
of you, apply rudder to accomplish a large circle
turn flowing away from you. Usually, instead of
just turning the plane with the wings held level, the
plane starts the turn and begins to dive into the
turn. To fix this, activate a mix in your radio to
apply opposite aileron with rudder. When adjusted well, instead of the plane diving with application of rudder, it just turns level. Right now I‘m
at about minus 7 percent on both left and right
rudder for the Edge. This adjustment greatly
helped my landings when application of rudder is/
was needed to correct for the runway.
Aileron Differential
This ―differential‖ has to do with the ailerons having more up movement than down. The down aileron has more drag than the up aileron, so the
planes fuselage yaws against the turn. A plane
without correct differential (especially a high wing
plane) will exhibit adverse yaw – applying left aileron yields not only a left rolling movement, but
Trimming a Sport Plane (continued on page
19)
18
Trimming a Sport Plane continued from page
18.
Rudder to Elevator Mixing
Although I have not tried this mix, it seems reasonable and is on my list to try. Perform the knife
edge as explained above, but since Flap Trim
has made coarse adjustments to the ailerons,
only minor adjustments are made with a rudder to
elevator mix.
CG
Per building instructions
Lateral Balance
Balance plane by spinner
and rudder.
Dive plane (at engine idle),
pull level.
Fly level, chop throttle.
Dynamic Balance
Engine Up/Down Thrust
Engine Right/Left Thrust
Fly vertical up, rudder correct.
Aileron Differential
Fly level, pull up 30 degrees, roll left or right.
Flap Trim (wing incidence)
Fly knife edge.
Rudder to Aileron Mix
Fly level, rudder turn.
Rudder to Elevator Mix
Fly knife Edge.
19
Move battery and servos to
adjust. Use lead as last
resort.
Add weight to light wing tip.
Add weight to light wing tip.
If plane dives, add down
thrust. If plane climbs, add
up thrust.
Rudder left, add left thrust.
Rudder right, add right
thrust.
Model‘s nose moved opposite the roll, increase differential. Model‘s nose
moved in direction of role,
decrease differential.
If dive, move down both
ailerons. If pull, move up
both ailerons.
Use opposite aileron to
keep wings level.
If dive, use up elevator. If
pull, use down elevator.
proved the plane to enter hover quite easily.
think the CG is just about right.
Funtana 90
Reliable Engine Operation and
Flight Trimming Notes
I
Engine Up/Down Thrust
To check for engine up/down thrust, I flew the
plane in the up wind direction from right to left with
full throttle. Just before the plane was directly in
front of me, I chopped the throttle to idle. The
plane continued to fly without pitch change. No
changes were needed.
By Pat Rose
My original flight trimming article appeared in the
January 2006 issue of Servo Chatter. If you are
interested, this issue of Servo Chatter is still
posted in the newsletter archive at our web site.
The engine I am using is a new Saito 120 that has
been sitting on the shelf for many years, just waiting for a plane. The Funtana 90 was purchased at
20% off from San Antonio Hobby when they were
going out of business. Finally, engine meets
plane this past spring and it is time to get this
plane in the air.
Engine Right/Left Thrust
I flew the plane up-wind until just in front of my
position and pulled up elevator for vertical flight.
The Funtana started to pull left immediately and
required a lot of right rudder trim. Eventually about
5 degrees of right rudder were needed after several vertical ascents. See photo 2. A few degrees
of right thrust were added to the motor mount using folded card stock. See Photo 3. Further test
flights proved this offset was just right. The plane
tracks straight up with very little correction
needed. O
The engine was broken in per Saito instructions
with the engine on the plane and the cowl off, and
the plane tied to the fence. After several tanks of
fuel were run through the engine, the high end
needle valve was adjusted and then the low end
needle valve was adjusted. The high end needle
was peaked using a tachometer then rotated
counter clockwise (towards rich) to slow the engine by about 800 RPM. I have found the best
way to adjust idle needle is to mount the glow
driver and adjust the idle needle for maximum
RPM. When the glow driver is removed, there
should be little or no loss of RPM. This high end,
low end process was repeated several times. The
cowl was mounted and the first flight was made.
Oops. The engine sagged at full throttle. I
thought the engine may have over heated so a
baffle was added in the cowl and the cowl exhaust
opening was enlarged. No luck. The engine
would not hold a high end needle setting. The
engine coughed when the needle was moved
slightly rich. I‘m using a 16-4w prop and some
bystanders suggested I needed a bigger prop.
The glow driver was mounted and the problem
stopped. I suspected the glow plug had gone
south. The glow plug was changed to an OS F
and the tuning problem was cured. The second
flight was made and the plane has unlimited vertical.
Figure 1
Figure 2
CG and Lateral Balance
I placed the CG as per the plans by the location of
the battery inside the fuselage. Lateral balance
required about ¾ ounce of lead on the left wing
tip. Dynamic balance showed the right wing tip a
little heavy, so ¼ ounce of lead was added to the
left wing tip. See Photo 1. Further test flights
20
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement