EXTENDING FLIGHT TIMES WHILE MAINTAINING BALANCE
by Ed Anderson
aeajr on the forums
Changing the type or capacity of your battery pack is typically done for one
of three reasons:
* You want longer flights
* You want to reduce weight.
* You want to do both
Here are some points to consider to get the most out of this change.
If you are currently flying NiCd packs, you can go to NiMh very easily. You
will gain about 40% in battery capacity at the same weight. The packs are
about the same size and shape so they fit easily and should not throw off
the plane's balance. NiMh and NiCd packs, NiXX for short, therefore can
typically be interchanged easily. I have eliminated virtually all my NiCd
motor packs and replaced them with NiMh packs.
If you go to lithium batteries you can either make your plane lighter or you
can maintain its weight but double, tripple or quadruple your battery
capacity. Lithium batteries have about 4 times the capacity per ounce as
compared to NiCd packs. Here are some steps to consider BEFORE you buy the
new pack:
Where is you battery pack located?
If your battery is forward of the CG, the balance point, then its weight is
helping to balance the plane. If you go to a pack of a different weight,
you MUST rebalance the plane or it won't fly well. For example, a lighter
pack will shift the CG toward the rear which may make the plane difficult or
impossible to fly. You must keep the plane in balance so that the CG,
center of gravity, the balance point, is in the right place.
This also applies to going to heavier packs as they will shift the CG
forward. A slight shift forward might not be a problem if you are adding
voltage as the more powerful pack will drive the motor faster which may mask
a slight change in balance and a more forward CG can make the plane more
stable. For Example I shift between 6 and 7 cell NiMh packs in my Aerobird.
The CG moves a little forward with the 7 cell pack but not enough to
seriously effect the way the plane handles. But optimally you want to keep
the CG in the same, the best location.
From here on I am going to assume you are going from NiXX packs to lithium
packs, as this is what many are doing and the one that takes the most
planning.
Before you buy that new pack:
* Weigh your current battery pack. A food scale or a postal scale is fine.
Many post offices in the US have self service scales. Great for weighing
stuff. Get it to the nearest .1 ounces. Write it on the pack so you won't
forget it.
* Now look at the space in the plane. Can the new pack go in the same or
almost the same place as your current pack? You can account for a location
shift by changing the amount of weight you add to the new pack.
Now decide on your goals based on what you can do in this plane and how much
money you want to spend.
1) Keep the weight the same and spend more money - Get a pack that fits in
the current space and weighs the same as your current pack - Now you can use
the new pack and your current packs interchangeably. Good deal! However
lithium packs are different sizes and shapes than NiXX packs so this might
be hard to do. If it is close, you might be able to modify the battery
space to allow the new pack to fit. A 600 MAh NiCd Pack weighs about the
same as a 2000 to 2400 MAh Lipoly pack, but the LiPoly may cost more.
Prices are dropping all the time and 4 times the flight time is definitely
cool!
2) Keep the weight the same and spend a bit less - Get a pack that is
lighter than your current pack and will fit in the same or close to the same
location, perhaps with minor mods to the plane. Maybe you go from a 600 MAh
NiXX pack to a 1300 MAh lithium pack rather than a 2400 MAh pack. This will
probably have a better chance of fitting where your NiXX pack fits. Great!
Add weight to the pack so it weighs the same as your NiXX pack. You can
still use both without serious modification to the plane. Good deal!
3) Make the plane lighter - If you can move stuff forward in your plane so t
hat a lighter battery can balance the plane, you can avoid the need to add
weight. Now you have a higher capacity battery pack AND your plane is
lighter. Lighter planes generally fly better. The only problem with this
approach is that your current "heavy packs" may not be able to be used
anymore unless you can leave space to adjust their position rearward.
If it won't fit, can you modify the space to make it fit?
If you remove foam, consider reinforcing the space with tape or glue and
light plywood as you have removed some of the structure of the plane. Can
you cut a hole in a former so the pack fits under it? Make sure you
reinforce to account for any cut away structure. By the way, tape, glue,
bals or plywood add weight so you so take these into account. Cut a little,
set some reinforcing in place but don't glue it. Position the pack and test
the balance of the plane; adjust accordingly. Be sure you pad the pack in
balsa or plastic planes so that a crash will not likely damage the pack.
Lithiums can not take the physical abuse that the NiXX packs tolerate.
If modifying the plane to move the pack forward won't get it done, then see
if you can move other things in the plane to shift their weight forward.
Some people have the receiver under the wings. Move it forward and it will
help to balance the plane and you won't have to add as much weight to the
lithium pack. Also see if you can move the ESC forward. Move any excess
wire that you have bundled to the forward area. Wire has weight.
If you have any components, like the receiver that sit behind the CG, moving
them forward will make a huge difference.
If you can move your electronics forward enough that you can balance the
plane without the battery pack, then you can set the battery directly over
the CG. Now it doesn't matter which battery pack you use as the weight of
the pack will not shift the balance of the plane. You can interchange packs
all you like.
When I rebuilt one of my sailplanes after a crash, I positioned my servos,
receiver and battery to more forward locations than the stock
recommendation. As a result I made the plane about 12% lighter with no
other modifications. That made a HUGE difference in how if flew.
I then made a removable motor for it and positioned it on a pod that sat
right over the CG so I could put it on or take it off without changing the
balance of the plane. Likewise I placed the battery right over the CG.
With the motor and battery mounted, the plane was much heavier, but it
stayed in perfect balance whether they were on or off the plane.
There are other considerations related to lithium batteries. You need a
special charger and charging procedures. You MUST protect them from damage
as they can not take the same abuse as NIXX packs. But these are covered in
other threads. This one is just about maintaining balance.
Clear Skies and Safe Flying!
* See if you can buy a lithium pack that is the same weight as your current
battery pack. If you can, and you can afford it you are all set and have
two to four times the flight capacity for longer flights.
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-22-2008, 10:31 PM
#10
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
BATTERY BASICS
by Ed Anderson
aeajr on the forums
Revised January 2007
All RC planes use battery packs to operate their electronics. On planes
that don't have electric motors we call these receiver packs as they power
the receiver and the receiver then distributes the power to the servos and
other electronics in the plane. However for electric planes, we also use
the batteries to power the motor. They are the chemical fuel tanks and
fuel pumps that store and deliver the energy we use to fly.
These battery packs are made up of cells which act as chemical storehouse
for electrical energy. When multiple cells are joined together we call this
a
battery or battery pack. There are a variety of battery types. Each has
advantages and disadvantages that we will discuss.
Battery Types
At the time of this writing, there are three commonly used rechargeable
types of cells. They vary by the chemical mix that is used to
hold and deliver the electricity.
Nickel Cadmium, NiCd, have been in around the longest.
Nickel Metal Hydride, NiMH came in to use later and are very popular today.
Lithium cells are typically lithium polymer, LiPoly or LiPo, and the less
commonly used Lithium Ion. These are the newest breed of chemical cells.
NiCd packs have the lowest power to weight ratio. That is to say that, for
a given electrical capacity they will weigh the most of the three types.
However they have the ability to be charged faster than the other two and
will give up their power fast. While still in common use, the are dropping
in popularity as the other two types are improving and gaining on NiCd's
advantage of quick charge and quick discharge. Each NiCd cell is rated at
1.2 volts.
Nickel Metal Hydride, NIMH, packs hold about 40-60% more capacity per ounce
than NiCds. So, for example, a 800 mah NiCd pack might weigh 6 ounces while
an equivalent capacity NIMH pack might be 4 ounces. Except for very high
performance, NIMH packs can't quite match NiCds for how fast they can
deliver their electricity or how fast we can charge them, but they are
catching up. There used to be a big
gap, but the gap is closing fast. NIMH are far more popular today then they
were just a few years ago, and probably have passed NiCd in usage. Each
NIMH cell is rated at 1.2 volts, the same as NiCd cells.
In many ways NiCd and NiMh cells are very similar in their application. So,
as a shorthand, I am going to start to refer to NiMH and NiCd as NiXX when
what I am saying applies to both. I hope this does not lead to confusion on
the reader's part.
Lithium packs are the lightest for their capacity. They typically hold 4 or
more times as much electricity per ounce as compared to NiCd packs. For
example a 6 cell, 7.2V 2100 MAh NiCd pack might weigh 12 ounces while a 2
cell 7.4V Lithium pack of the same capacity will be about 4 ounces.
Because much of our RC electronics have been based on 4-5 cell NiXX packs
they are tuned for 4.8-6V receiver packs. However Lithium packs are 3.7V so
one cell is a bit low and two cells at 7.4V is a bit high. So Lithiums have
not been in common use for receiver packs used in gliders or glow powered
planes. Some micro plane electronics systems have been designed for 1 cell
lithium packs and the newer generation of electronics for the rest of the
market are being retuned to accept 1-2 cell Lipo receiver packs.
As a result, Lithiums have been used primarily as motor packs. Up until
recently, Lithium packs have been slower to charge and slower to deliver
their power. The newest generation Lipos can now deliver high currents but
still need to be charged at 1/3 the rate of NiCd or 1/2 the rate of NiMH
motor packs. However over time they are improving. They are growing in
popularity as the charge/discharge rates improve and the prices come down.
Each Lithium cell is rated at 3.7 volts.
Pack Configuration
Unless stated otherwise, we join the cells into packs by joining them in
series. In series we add the voltage of each cell so that a 6 cell NiXX
pack will be rated at 6 X 1.2 volts or 7.2 volts. With lithium packs, which
are rated at 3.7 volts per cell, it would take two cells to create a
comparable 7.4 volt pack. When you hear people talk about 4 cell, 6 cell,
however many cells today, they are usually talking about NiCd or NIMH cells.
However, with the rise of Lithiums, you should ask to be certain that they
are not talking about lithium cells.
Clearly if your instructions say that your motor can use a 7 cell pack, it
would be important to know if that is 7 NiXX cells or 7 Lithium
cells as the voltages would be very different. A 7 cell NIMH or NiCd
pack would be 8.4 volts. A 7 cell Lithium pack would be 24.9 volts.
While it is unusual to combine NiCd or NIMH packs in parallel to increase
capacity, it is quite common with Lithium packs. This has spawned the xSyP
designation, were x is how many Lithium cells are connected in series and y
is how many groups of these cells are connected in parallel. So a
3S2P pack would have two groups of 3 cells. This allows us to deliver
higher amperages at the same voltage, or to provide more capacity for
longer flights at the same voltage. The xSxP designation is most commonly
used with Lithium packs. I don't recall ever seeing this used with NiXX
packs.
Battery Chargers
When charging your battery packs you MUST use the right kind of charger or
you will damage the cells. Using the wrong charger, especially with lithium
cells, can actually lead to a fire or an explosion. So be sure that you
have the right charger for the kind of cells you are charging. Some
chargers are specific to one kind of cell while some can charge two kinds
and
some can charge all three. Make CERTAIN you know before you charge or
you could put your model, your car, your home or your personal safety at
risk.
I hope this has been helpful. Below are some additional resources for
further reading.
Excellent overview and safety information on Lithium Batteries
www.rchobbies.org/lithium_battery_breakthrough.htmwww.rcgroups.com/forums/showthread.php?t=209187Lithium Battery Balancers and Chargers
www.rcgroups.com/forums/showthread.php?t=599287More on Batteries
www.modelaircraft.org/mag/FTGU/Part8/index.htmlA123 CELLS - This is an emerging cell for large
electric plane use.
www.rcgroups.com/forums/showthread.php?t=618071#post6636651The Battery Clinic
www.rcbatteryclinic.com/__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-22-2008, 10:32 PM
#11
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
LITHIUM BATTERY CHARGERS -
Balance chargers vs. external balancers
Lithiums are great, but they benefit from a little extra care. We have seen that packs
with two or more cells can get out of balance. That means that one cell tends to
rundown lower or tends to charge higher. Since charging through the power port
that connects to the ESC only reads the total pack voltage the charger will charge
the pack to the expected voltage. For Lipoly packs that would be 4.2V per cell.
Therefore, when charging through the power port, the charger will take a 3 cell Lipo to
12.6V, regardless of the individual cell voltages. But if one cell is low and one is
high, that could result in one cell perhaps being charged to 4.3V or one being charged to
4.1V, for example.
Over many cycles this difference will build up. The most benign outcome is a loss of
pack performance. A more serious outcome could be that the low cell will drop below
the critical 2.5V level on discharge and be damaged, rapidly degrading the pack.
The more serious issue could be that one cell gets seriously over charged getting
well above the desired 4.2V top charge. This can result in pack failure or can cause the
over charged cell to "vent with flame". This is ungood. :-O
Balancers
So, for the past 18-24 months we have seen a flood of pack balancers that will bring the
packs into balance to maintain an even charge across all cells. To use these balancers you
need a compatible balance plug on the pack. Assuming you have this arrangement,
a balancer can help prevent the above situation. If you are happy with your charger and
don't feel the need for a new one, a balancer is a good investment. They run from $20 to $50
with a variety of features.
The balancing benefit is significant but it need not be critical to every charge cycle. Packs
don't go out of balance THAT fast. It might happen over 10 cycles or 20 cycles and it builds
up over time. So using a regular charger that charges through the power plug is fine. If you
balance every few charges, that would be adequate. Just be sure to do it and you have to
have a way of being sure you are doing it across all your packs.
Note that a balancer can only drain power so it does reduce the overall charge level of the pack,
it does not bring up the low cells. But I don't think that is a big deal.
Balancing Chargers
There are two features being discussed here, charging and balancing.
Some are chargers combined with balancers. They charge the pack to the desired
level, then the built in balancer bleeds down the high cell and charging can continue.
This is a good combination. It saves you from having to do this with a separate device.
This type of charger provides the very significant value of keeping your packs in balance
automatically. This leads to longer life, and better performance. And it has some safety
benefits in that it prevents one cell from being over charged.
Balanced Chargers
Then there are balancing chargers that charge each cell individually during the charge
cycle. The CellPro 4S, for example, charges each cell individually during the charge cycle.
If one cell is a little slower than the others the charger compensates so higher rates can be
tolerated, or so the charger companies claim. The older CellPro 4S that I have has a safe
charge cycle that charges at up to 1.4C. This is a side benefit of the balanced charge process.
The newer Cell Pro 4S charges at up to 3C. If charging your packs faster,
safely, is important to you, then these types of balancing chargers are a good value. CellPro is not
the only one but it is a good example. So, from that respect, certain chargers, let's call
them balanced chargers, bring more benefits than just balancing.
Practical use
I have 5 lipo packs with CellPro balance taps. Most of the time I charge them on my CellPro
charger but I also charge them on my Triton charger and on an AC wall wart Lipo charger.
Only the CellPro balances, but the packs get on it every few cycles so they will be balanced
on the next charge cycle. And only the CellPro charges at the higher rate. The others are
limited to 1C and I will not push them.
Cold Weather Cycle
I don't know if this is a common feature but the CellPro 4S also has a cold weather cycle.
It actually detects the temperature of the surrounding air. If it is below a certain level, it only
charges the cells to about 95% of full charge. This has very little impact in practical use but
it provides a safety effect. If you were to charge a lipo pack at the field, say at 30 degrees,
then not use it and take it home, as it warmed the cell voltage would rise, potentially taking it
over the desired 4.2V level. I can not say how serious a concern this may be, but it seems
to make sense that it could present an unrecognized problem. This charger accounts for it
automatically. I am sure there must be others that do it as well.
I do feel the balancing chargers are better than balancers, BUT not enough that it should be a
big concern if you don't feel you want a second charger or the higher charge rates that some
of the newer ones can offer. But understanding the benefits of balancing IS important.
Other Reference Sources
CellPro discussion
www.rcgroups.com/forums/showthread.php?t=786192&page=2#post8863342Notes on Lithium Batteries
www.rchobbies.org/lithium_battery_breakthrough.htmThe Battery Clinic
www.rcbatteryclinic.com/__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgLast edited by AEAJR; 10-26-2010 at 04:18 PM.
AEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-22-2008, 10:33 PM
#12
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
This is not totally unique to electric flight, but since many new electric pilots are trying to self train, it sorta fits.
SIX KEYS TO SUCCESS
by Ed Anderson
aeajr on the forums
Whether you have a coach or you are trying to learn to fly on your own, you
will need to be mindful of these six areas if you are going to become a
successful RC pilot. After years of working with new flyers at our club,
and coaching flyers on the forums, there are a few things I have seen as the
key areas to stress for new pilots. Some get it right away and some have to
work at it. They are in no particular order because they all have to be
learned to be successful.
WIND
Orientation
Speed
Altitude
Over Control
Preflight Check
1) Wind - The single biggest cause of crashes that I have observed has been
the insistence upon flying in too much wind. If you are under an instructor's
control or on a buddy box, then follow their advice, but if you are starting
out and tying to learn on your own, regardless of the model, I recommend
dead calm to 3 MPH for the slow stick and tiger moth type planes. Under 5
MPH for all others. That includes gusts. An experienced pilot can handle
more. It is the pilot, more than the plane, that determines how much wind
can be handled.
The wind was around 10 mph steady with gusts to 12. That was strong enough
that some of the experienced pilots flying three and four channel small
electric planes chose not to launch their electrics. This new flyer
insisted that he wanted to try his two and three channel parkflyers. Crash,
Crash, Crash - Three planes in pieces. He just would not listen. Sometimes
you just have to let them crash. There is no other way to get them to
understand.
Many parkflyers can be flown in higher winds by AN EXPERIENCED PILOT. I
have flown my Aerobird in 18 mph wind (clocked speed) but it is quite
exciting trying to land it.
Always keep the plane up wind from you. There is no reason for a new flyer
to have the plane downwind EVER!
2) Orientation - Knowing the orientation of your plane is a real challenge,
even for experienced pilots. You just have to work at it and some adults
have a real problem with left and right regardless of which way the plane is
going. Licensed pilots have a lot of trouble with this one as they are
accustomed to being in the plane.
Here are two suggestions on how to work on orientation when you are not
flying.
Use a flight simulator on your PC. Pick a slow flying model and fly it a
lot. Forget the jets and fast planes. Pick a slow one. Focus on left and
right coming at you. Keep the plane in front of you. Don't let it fly over
your head.
FMS is a free flight simulator. It is not the best flight sim, but the
price is right and it works. There are also other free and commercial
simulators.
FMS Flight simulator Home Page
Free download
n.ethz.ch/student/mmoeller/fms/index_e.htmlParkflyers for FMS
gunnerson.homestead.com/files/fms_models.htmGetting Started with FMS
www.wattflyer.com/forums/showthread.php?t=3893The links below take you to sites that provide cables that work with FMS.
If your radio has a trainer port, these cables allow you to use the trainer
port on your radio to "fly" the simulator. This is an excellent training
approach.
www.allthingsrc.com/webshop/www.simblaster.com/www.customelectronics.co.uk/An alternative is to try an RC car that has proportional steering. You
don't have to worry about lift, stall and wind. Get something with left and
right steering and speed control. Set up an easy course that goes toward
and away from you with lots of turns. Do it very slowly at first until you
can make the turns easily. Then build speed over time. You'll get it! If
it has sticks rather than a steering wheel even better, but not required.
Oh, and little cars are fun too.
3) Too much speed - Speed it the enemy of the new pilot but if you fly
too slowly the wings can't generate enough lift, so there is a compromise
here. The key message is that you don't have to fly at full throttle all the
time. Most small electrics fly very nicely at 2/3 throttle and some do quite
well at 1/2. That is a much better training speed than full power. Launch
at full power and climb to a good height, say 100 feet as a minimum, so you
have time to recover from a mistake. At 100 feet, about double the height
of the trees where I live, go to half throttle and see how the plane
handles. If it holds altitude on a straight line, this is a good speed.
Now work on slow
and easy turns, work on left and right, flying toward you and maintaining
altitude. Add a little throttle if the plane can't hold altitude.
4) Not enough altitude - New flyers are often afraid of altitude. They
feel safer close to the ground. Nothing could be more wrong.
Altitude is your friend. Altitude is your safety margin. It gives you a
chance to fix a mistake. If you are flying low and you make a mistake ....
CRUNCH!
As stated above I consider 100 feet, about double tree height where I live,
as a good flying height and I usually fly much higher than this. I advise
my new flyers that fifty feet, is minimum flying height. Below that you better
be lining up for landing.
5) Over control - Most of the time the plane does not need input from you.
Once you get to height, a properly trimmed plane flying in calm air will
maintain its height and direction with no help from you. In fact anything
you do will interfere with the plane.
When teaching new pilots I often do a demo flight of their plane. I get the
plane to 100 feet, then bring the throttle back to a nice cruising speed. I
get it going straight, with plenty of space in front of it, then take my
hand off the sticks and hold the radio out to the left with my arms spread
wide to emphasize that I am doing nothing. I let the plane go wherever it
wants to go, as long as it is holding altitude, staying upwind and has
enough room. If you are flying a high wing trainer and you can't do this,
your plane is out of trim.
Even in a mild breeze with some gusts, once you reach flying height, you
should be able to take your hand off the stick. Oh the plane will move
around and the breeze might push it into a turn, but it should continue to
fly with no help from you.
Along this same line of thinking, don't hold your turns for more than a
couple of seconds after the plane starts to turn. Understand that the plane
turns by banking or tilting its wings. If you hold a turn too long you will force
the plane to deepen this bank and it will eventually lose lift and go into a
spiral dive and crash. Give your inputs slowly and gently and watch the
plane. Start your turn then let off then turn some more and let off. Start
your turns long before you need to and you won't need to make sharp turns.
I just watch these guys hold the turn, hold the turn, hold the turn, crash.
Of course they are flying in 10 mph wind, near the ground, coming toward
themselves at full throttle.
6) Preflight check - Before every flight it is the pilot's responsibility to
confirm that the plane, the controls and the conditions are correct and
acceptable for flight.
Plane - Batteries at proper power
Surfaces properly aligned
No damage or breakage on the plane
Everything secure
Radio - Frequency control has been met before you turn on the radio
A full range check before the first flight of the day
All trims and switches in the proper position for this plane
Battery condition is good
Antenna fully extended
For computer radios - proper model is displayed
All surfaces move in the proper direction
Conditions - No one on the field or in any way at risk from your fight
You are launching into the wind
Wind strength is acceptable ( see wind above )
Sunglasses and a hat to protect your eyes
All other area conditions are acceptable.
Then and only then can you consider yourself, your plane, radio and the
conditions right for flight. Based on your plane, your radio and local
conditions you may need to add or change something here, but this is the
bare minimum. It only takes a couple of minutes at the beginning of the
flying day and only a few seconds to perform before each flight.
If this all seems like too much to remember, do what professional pilots do,
take along a preflight check list. Before every flight they go down
the check list, perform the tests, in sequence, and confirm that all is right.
If you want your flying experience to be a positive one, you should do the
same. After a short time, it all becomes automatic and just a natural part
of a fun and rewarding day.
I hope some of this is useful in learning to fly your plane.
Other resources you may find useful:
Books on RC Planes and RC Flying
www.stevensaero.com/shop/product.php?productid=16645&cat=262&page=1www.amazon.com/gp/product/B00071VIGC/sr=8-1/qid=1140260256/ref=pd_bbs_1/103-2556298-8424625?%5Fencoding=UTF8www.amazon.com/gp/product/B0006PBE2M/sr=8-8/qid=1140260256/ref=sr_1_8/103-2556298-8424625?%5Fencoding=UTF8__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-22-2008, 10:33 PM
#13
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
THINGS TO CHECK ON AN RTF
by Ed Anderson
aeajr on the forums
I think ready-to-fly airplane packages are great. This is how I started flying.
If I had been required to build a kit to begin my flying experience I would
never have gotten into the air. Now, after thousands of flights and almost
years of flying, I have expanded to 20+ planes, multiple radios and all kinds of
tools and things. I am having a ball. But there are things I know today that
would have helped me with my first plane. Let me pass on some tips.
Regardless of the plane, RTF or not, it is the pilot's responsibility to insure
that the plane is flight ready. If you put a plane in the air without checking
it, without following the instructions, any problems that follow, any damage
that is caused is your fault and responsibility. It does not matter if the
plane is defective, if you did not check it, any damage that occurred is your
fault. I can't make it any clearer. No full scale pilot would takeoff without
checking everything. You should do the same.
READ THE INSTRUCTIONS!
There is a manual or instruction sheet that comes with your plane, read it! I
read the manual several times on anything I get. It took the manufacturer time
and money to create it. I contains important information. Some instruction
sets are poorly done and some are very good. In either case, READ! If there
is a video included, watch it. It was put there to help you. Take advantage
of that help.
If they have a web site about the plane or product you purchased, visit the
site. Sometimes there is an FAQ, frequently asked questions page. Sometimes
there are additions to the instructions that have been added since yours was
packaged and shipped. And sometimes there are coupons, or specials for owners.
Go, look and see, and benefit from the manufacturer's web site.
RTFM
I often post this in my notes on the forums, "RTFM". To put it politely, it
means, " Read The Friendly Manual".
I have read so many trouble reports by new flyers. They crash, they have
problems and are angry and upset. Why was this happening to them? Often, the
answers were all in the instructions.
We had one club member who used to buy RTF planes, show up at the field and ask
me how to get them set-up and flying. I would ask him for the instructions.
"Oh, I left those home." So I sent him home to get them. No matter how
experienced I might be, unless I have this plane, I check the instructions.
He brought a computer radio to a meeting and asked me to show him how to use it.
"Sure, where are the instructions?" He left them home. I could not help him as
I had never seen that radio before.
Needless to say, he crashed and crashed and destroyed things. Fortunately for
him he had the money to do this. But he occasionally created a safety situation
and we had to "advise" him to change his ways. He has yet to become a
successful flyer. He is still a nice guy and I hope some day he will be
successful, but he needs to follow instructions.
THINGS TO NOTE WHEN YOU READ THE MANUAL
1) Does the plane need to be balanced, or does the balance need to be checked?
2) Are there linkages to be connected? Do they need to be adjusted? How do you
adjust them?
3) Is there tape or glue to be added. Is there covering material to be removed?
4) Do the batteries need to be charged?
5) Do they recommend some kind of "break-in" procedure?
6) What is the proper range check procedure for the radio system?
7) What is the working range of your radio system?
8) How do you adjust the surfaces to get the plane to fly correctly? Are they
moving in the correct direction?
9) What is the proper placement of the battery and how is it moved to adjust
balance?
10) Is there a maximum recommended voltage that can be safely accepted by the
ESC?
11) What wind speeds are recommended for new flyers?
12) How much space is recommended to fly this plane?
13) Who do you call if there is a problem? Do you call the hobby shop or the
manufacturer? Is there a web site?
14) Are there repair tips? What kind of glue can you use? Where can you get
replacement parts?
15) What channel is your plane using and how do you avoid channel conflict?
ASSEMBLY TIPS
Often, in order to meet a packaging goal or to keep the shipping weight down,
the manufacturer will expect you to do something or to add something. These are
usually common household items like tape or glue. In some cases the plane's
balance has to be checked and/or adjusted. They may include weights, or you
may need to buy weights, but coins work too. A dime is about .1 ounces and a
quarter is about .2 ounces. Coins can actually be cheaper than buying weights.
It is common to have to mount the tail and the wing. Are there alignment marks
or procedures that you are to follow? Do you have to remove covering material
so the glue will hold properly? How many rubber bands are needed to hold the
wing properly? Don't use less than the recommended number of rubber bands.
My Great Planes Spirit 2M glider came RTF, including the radio system. This was
my second plane after my Aerobird. The Aerobird did not need to be balanced,
the Spirit did. If I had tried to fly it without balancing it first I would
likely have broken it badly on the first flight. It took four ounces of weight
in the nose to get to balance properly.
A friend's RTF was brought to the field so we could help him. Following the
instructions we did a range check and found there was a problem with the radio
system. No problem! He packed it up, took it to the hobby shop and they
exchanged it immediately. He was back at the field in an hour. It was clear it
had not been flown so there was no question of flight damage. If he had flown
and crashed it, they could have easily refused to replace it, and they would
have been right, as crash damage is not covered under warranty. It was the
pilot's job to make sure the plane was flight ready.
FLYING TIPS
Often RTFs come with flight instructions and tips. One of the most important to
follow is related to wind. Many planes, especially two channel planes, do not
handle wind very well, especially in the hands of an inexperienced pilot. If
you don't know this, you could loose your plane, or worse, you could hit someone
or cause damage. What wind speeds are recommended, especially for new pilots?
Sometimes the plane will "porpoise" or tend to roll, or want to dive. Is it you
or is it the plane? The instructions may tell you.
Once the pilot has become comfortable with the plane, there may be adjustments
that can be made to make the plane more responsive. Sometimes it is that switch
on the radio, or a button you need to push, that goes from mild to wild. Or
maybe you have to turn something on the linkage, or move the linkage to a
different hole. Go back and read the manual for the proper procedures to make
those adjustments.
SUMMARY
Just because the plane says ready to fly, don't take that literally. Compared
to a box of sticks and a tube of glue, it is ready to fly. However there are
often set-up procedures, or assembly steps that needs to be done. It is best
to read the instructions to see how to do them correctly. You will have a much
better flying experience and your plane will last longer.
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-22-2008, 10:34 PM
#14
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
Now its your turn. Post your articles, ask your questions, share your knowledge!
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-23-2008, 12:46 PM
#15
FlyWheel
Ochroma Pyramidale Tekton
FlyWheel's Avatar
Join Date: Jul 2007
Location: Clover, South Carolina
Posts: 3,033
Arrow
Sticky! Sticky! Sticky!!!
__________________
Associate with troublemakers, you'll be included with them.
When the troublemakers are restricted, you'll be included with them.
Still think I'm paranoid?
FlyWheel is offline Add Infraction for FlyWheel Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-23-2008, 04:17 PM
#16
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
Thanks! We will see if anyone agrees with you.
I have other article in the works. A more detailed discussion of the ESC will be next.
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-23-2008, 04:23 PM
#17
Rabbitcreekok
Community Moderator
Rabbitcreekok's Avatar
Join Date: Aug 2005
Location: McAlester, Oklahoma
Posts: 10,811
Default
Ed, this definitely needs to be a sticky in the proper forum so it is easy to find to and newcomers can be easily referred to the e-book.
Thanks for all the good work you do on WattFlyer.
__________________
Jim
AMA 735658
Rabbitcreekok is offline Add Infraction for Rabbitcreekok Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-23-2008, 05:06 PM
#18
FlyWheel
Ochroma Pyramidale Tekton
FlyWheel's Avatar
Join Date: Jul 2007
Location: Clover, South Carolina
Posts: 3,033
Default
Quote:
Originally Posted by AEAJR View Post
Thanks! We will see if anyone agrees with you.
Oh, I have little doubt about that. And I wouldn't worry about your "book" becoming obsolete either. Only products do that, and from what I've read so far, this mainly covers the basic rules of the game. Electronic formulas, aerodynamics, power. These are physical laws, if they become obsolete you won't be getting too many complaints, trust me!
__________________
Associate with troublemakers, you'll be included with them.
When the troublemakers are restricted, you'll be included with them.
Still think I'm paranoid?
FlyWheel is offline Add Infraction for FlyWheel Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-23-2008, 09:50 PM
#19
Dorsal
If it Flies, I love it!
Dorsal's Avatar
Join Date: Dec 2006
Location: Tracy, California
Posts: 548
Default
Ed, Great Job! This needs to become a sticky!
The one question every beginner wants to ask but won't voice is "Why do you guys pay so much for your RC equipment? You must just be crazy! Joe's Discount House of Junk will sell me a complete RC system, airplane, radio, motors and all for $10. Isn't that good enough?"
In other words, I think you should address the "cheap is not better for these reasons" kind of issues.
Oh, please feel free to delete this post after you've read it, so it won't clutter up your great "How To".
__________________
Dennis Fishback AMA# 162410 AKA# 120592
If it flies, I love it!
Dorsal is offline Add Infraction for Dorsal Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-24-2008, 12:00 AM
#20
Dick S.
New Member
Join Date: Feb 2008
Location: Northern Indiana
Posts: 8
Default
Thanks for all the work of writing the E-book. I'm just getting into Electric model planes and the timing of the article couldn't be better.
Another vote for a sticky! Thanks again.....Dick S.
Dick S. is offline Add Infraction for Dick S. Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-24-2008, 05:39 AM
#21
bigsi40
New Member
Join Date: Feb 2008
Location: Coventry u.k
Posts: 8
Thumbs up
Wow what a great read,Has really helped with my knowledge of things and with my RTF plane hopefully coming next week i will know now what to look for.
Another vote for this being sticked in the beginners section as well so it nice and easy to find
Bigsi
bigsi40 is offline Add Infraction for bigsi40 Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-24-2008, 05:52 AM
#22
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
OK, I have enough requests to make this sticky, but I am going to keep it in the general forum. There are plenty of sticky threads in the beginner section.
Beginners will find it here, but I hope non-beginners will find it useful also, so I would prefer it to be in the general section.
Note that I added an article on the ESC and placed it at Post 5 where it made more sense. I moved the BEC article to 23. I also added an article on First Planes and what to look for in terms of design and materials.
The table of contents has been updated.
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.orgAEAJR is offline Add Infraction for AEAJR Report Post IP
Edit Quote Multi Quote Quick Reply
Old 02-24-2008, 07:03 AM
#23
AEAJR
Community Moderator
Thread Starter
Join Date: Aug 2005
Location: NY, USA
Posts: 5,873
Default
THE ROLE OF THE BEC IN YOUR ELECTRIC PLANE
by Ed Anderson
aeajr on the forums
Updated 1/24/15
In the world of electric motors the electronic speed control, ESC, takes the
place of the throttle servo used on fuel powered planes. It regulates the speed of the
motor by pulsing the power to the motor to achieve the desired motor speed.
However most ESCs also have two other functions, the LVC and the BEC.
The LVC, low-voltage-cutoff circuit, will cut power to the motor and preserve
power to the radio system so you can land your plane safely when the motor
battery is getting too low. In the case of lithium batteries, the LVC, can also
save your battery packs by preventing them from getting too low. If you started
with NiXX packs and have switched to lithium packs, be sure your LVC is set
properly or you could damage your lithium packs.
The BEC, the battery elimination circuit supplies power to the receiver and the
servos. It is the BEC that will be the main focus of this discussion.
The name, battery elimination circuit, comes from the fact that, in the "old
days" of electric planes, you had a battery pack to power the motor and another
one to power the receiver. In order to save weight, the BEC was introduced to
eliminate the need for that receiver battery pack.
BEC, battery elimination circuit, is a generic term that applies to all circuits or
devices, whether in an ESC or as a separate device, that step the
voltage to the desired level. You could also call them voltage regulators.
They take the power from a battery pack and reduce the voltage to the level
desired. For example, an 11.1 V 3S lipo pack gets stepped down to 5V to run
your receiver and servos. Most are fixed but some can be set for the desired
output voltage.
There are two types of BEC in common use, linear and switching.
Whether you do it with a switching or a linear BEC the effect is about the
same. I am not aware of any reason to believe that one is more reliable than
the other or that an external BEC is in any way better than one integrated
into your ESC. The critical issue is the sizing of the BEC to meet the
amperage and voltage needs of your equipment.
It is worth noting that linear BECs are more commonly used with lower
voltage battery packs. That is because the linear BEC uses a resistance
process to drop voltage from, say 11V to 5 V and this generates heat.
Nothing to be concerned about but that is how it works. So once you get past
a 4S lipo or a 12S NiXX pack the step down becomes enough that most
manufacturers go to the switching BEC design. This uses the same type of
switch on/off process that your ESC uses to regulate the speed of your
motor.
There is nothing inherently more or less reliable in either design from a
practical point of view. It is just a matter of the most appropriate device for
the use case. I would have no hesitation to use a linear BEC
on any pack for which it is rated. Nor do I have a big preference for
external vs. internal BECs.
One thing to note is that linear BECs are rated for output based on input
voltage. So, a linear BEC might be rated for 3 amps output when used on a
2S pack but only 2 amps output when used on a 3S pack. Again, that is related
to the resistance method. The higher voltage drop generates more heat so
they derate the device for safety. But if you only need 1 amp, who cares?
The biggest issue we face when talking about BECs is that we really don't
know what we need in amperage. Do you know how many amps any given servo
draws? Did you know that the number goes up when the servo is under load?
And, of course, the total amp load goes up if you are moving more than one
servo. And a stuck servo's amp draw can go very high.
Typically we evaluate the size of be BEC based on the number of servos,
what has worked in other planes or what the MFG recommends.
As an example, the Radian Pro Bnf has 6 micro servos and a Spektrum receiver.
It was originally shipped with a BEC rated at 750 mah. Now, most people would tell you that
that is not a large enough BEC for 6 micro servos. But there were a LOT of
Radian Pros shipped with them and most flew just fine. Later they shifted
over to a larger BEC, 1.5 amps I think, to provide a greater margin for safety.
Note that the voltage rating for the ESC may be different than the voltage
rating for the BEC. Your ESC may be rated for 6S/22.2V but the BEC may have
to be disabled over 12 volts and you will have to power the receiver separately.
If you don't take note of this and pop in a 6S lipo, your ESC may be fine
but your BEC may be heading for a failure, resulting in a crash.
If you are flying an RTF or "receiver ready" model, you can be confident that the
BEC chosen is appropriate when used with the recommended battery pack. As
an example, the manufacturer of the plane may
designate that the plane takes an 8.4V pack. At that voltage the included BEC
may be fine. However, if you decide to pop in a three cell lipo, a problem may
only be a launch away. The BEC may do fine for a couple of flights, or maybe 5
minutes or may fail 100 feet out, and down you go.
We also have the variable of which servos are being used. Different servos draw
different amounts of current. If the current draw gets too high, the BEC will
overload causing a shutdown of the BEC. This protects the BEC and
prevents a fire, but cuts the voltage to the receiver. The net effect is that
you lose all power to the radio system and you lose control of the plane.
In the case of an overheated BEC, if there is enough cooling air going through
the plane, the BEC may come back quickly as it cools. This could look like a
radio glitch, but it could be the BEC operating on the edge of total failure.
If your ESC is very hot when you land, the cause could be the BEC operating at
the edge of its capacity. When we see these glitches, we often think the
problem is the radio system, but in fact the cause is power to the receiver.
When we were switching from 72 MHz radios to 2.4 GHz radios a lot of people thought
their 2.4 GHz receivers were failing but what was actually happening was that the
2.4 GHz receivers pulled more power, more amps, which overloaded the BEC in
the plane. If the BEC was just adequate for the 72 MHz receiver, which may have
only needed 20 mA and you put in a receiver that needed 100 mA then a BEC that
was just adequate for the 72 MHz receiver could cut out with the 2.4 GHz receiver.
We are more aware of this now and this has become less and less of a problem.
A CASE STUDY
This pilot was flying a new Spektrum 2.4 GHz system. All was fine till the plane
suddenly went dead and crashed. All sorts of speculation were offered about what
the cause could be and much of it was focused on the Spektrum 2.4 GHz system.
After the plane was recovered, everything seemed to work OK so it must have been
a radio hit, right? However, due to the diligent work of the pilot, it was
determined that the BEC had failed due to overload. You can read the actual
account at this link in posts 2986 to 3006.
www.rcgroups.com/forums/showthread.php?t=604621&page=200This is not the only account of this type that has been reported, but this was
one that was worked out over a short time with a very clear outcome. Note also
that the pilot had to run his test for several minutes before the failure
appeared. Thus, everything seemed fine at first; it seemed that the BEC was
handling the load. But over several minutes' heat built up in the BEC. Combine
this with the heat from the motor and the battery and, perhaps not enough
cooling airflow and the BEC shut down.
BE COOL FOOL!
With good airflow a BEC overload may be avoided. Regardless of what radio
system you are using, make sure you have enough cooling air going through your
electric plane. This is especially true of foam planes as the foam acts as an
insulator. You may have a cooling air vent in the front somewhere, but the heat
can't get out unless there is an exit air hole large enough to allow good
airflow. If you are pushing the limit on any part of your power or radio system,
not enough cooling air can cause damage or failure to your motor, ESC, BEC or
battery packs.
How you fly your plane can also cause heat build-up. For example, an Easy
Glider that has the motor run 1 minute to get to altitude then glide might have enough airflow
to eliminate the built up heat. But if you run the motor constantly for 10 minutes,
the heat build up could be enough to cook your BEC, your battery pack, or some
other part of the plane.
Be cool fool, and make sure you have enough airflow in your plane. If your
battery is very hot, or if your ESC is very hot, you may need more cooling.
OTHER CAUSES OF BEC PROBLEMS
You could be configured properly. Your BEC may be rated to handle your servo
count and you could have plenty of cooling air but still have problems. If you
have a servo push rod that is dragging or is otherwise placing a high load on
the servo, this can increase the amp draw of that servo. If that servo gets
stuck, the amp draw will go way up!
Servo loads are expected to be variable. A servo will move, put a load on the
BEC then come back to neutral and the current draw will drop. In between loads,
the BEC has a chance to cool. However a jammed servo will draw a lot of power
and that draw will be constant. You can see why it is very important that your
servos move freely, without binding. Check those control rods for kinks,
obstructions or things that could get in the way.
ENTER THE COMPUTER RADIO
In the past it was common to have 2 ailerons run off of one servo, so three
servos were typical of a 4-channel electric plane. With more and more people
using computer radios, there is a tendency to put 2 servos on the ailerons
meaning more load on the BEC.
Also, with a computer radio it is easy to add a little aileron to rudder mixing,
moving 3 servos at once. Now add a little up elevator in the turns and all four
servos are pulling power. Go to a full house electric sailplane, with flaps
following ailerons, rudder mixed in and a little up elevator in the turn and you
now have 6 servos, all moving at once. We begin to see how the BEC can become
challenged to keep up.
WHAT IF YOU NEED MORE?
If you need more power than the integrated BEC in your ESC can supply, or if
your motor battery voltage is higher than the BEC can handle, you will need to
disable the integrated BEC and put in a separate receiver pack or a separate
BEC. Many companies make after market BECs that can handle these higher
voltages or higher servo loads.
Remember there are two different types of BECs. Both work but they work
differently. Most, but not all aftermarket BECs seem to be switching BECs,
but be sure to read the instructions. If the amp output is different based on
battery voltage then it is a linear BEC. Nothing wrong with that, just be aware
of the rating for the voltage battery pack you plan to use.
Regardless of what type you have, follow the instructions carefully or risk
losing your plane. And be sure to provide plenty of cooling air.
Listed below are some examples of after market BECs.
Dimension Engineering has several BECs
www.dimensionengineering.comThe SMART BEC - Combines BEC and LVC that is Lithium aware
www.dimensionengineering.com/SmartBEC.htmSUMMARY
The ESC is the heart of your electric power system. The BEC is the part of the
ESC that powers your radio system. Keep it cool and make sure you read the
instructions so you don't overload it. Forget these tips and you may be
picking up pieces of your plane, wondering what caused that crash.
__________________
Long Island Silent Flyers
www.lisf.orgEastern Soaring League
www.flyesl.org 
