More TECHNICAL Details
AUTOMATIC FLAP POSITIONING, with or without
STEP & PROPORTIONAL MODES
OPERATES ON +12V & +24V SYSTEMS
COMPATIBLE WITH MOST MOTORS
* Set-Up is FULLY user PROGRAMMABLE!
ONE BUTTON PROGRAMMING
NO LIMIT SWITCHES TO INSTALL
A little BACKGROUND
You are coming in for a
landing. You slow your bird down and add your first notch of flaps. The first
thing you notice is that you have to hold a bit more pressure on your elevator
control stick or yoke to keep your bird on the same glide path. In order to
relieve this back pressure you manually crank in a bit of elevator trim. This
is repeatedly done for every notch of flaps that you crank in, all the way down
to the runway. We constantly trim, trim, and re-trim to get this stick back
pressure to zero. It happens more or less the same, for every landing and
take-off. This is a very repeated task.
Also picture yourself doing a
touch and go. When you finally land, you may have quite a bit of elevator trim
cranked in to compensate for your full flap position. You land, roll out, then
retract the flaps and add full power to take-off again. The elevator trim you
cranked in on landing, now has to be adjusted for your take-off attitude. This
is usually done in the air while you are fighting the elevator back pressure and
while doing other tasks.
Just think how nice it would
be to never have to touch your elevator trim. If this were the case, your bird
would never be out of trim and your elevator stick back-pressure would feel
great, all the time, take-off or landing, . . thus, . . . the proverbial
perfectly trimmed airplane! For example, when you put in a notch of flaps, your
bird would not change its glide path. It would simply slow down. You wouldn’t
notice any stick pressure difference. You would say to yourself, “Now, this is
what a plane should feel like!”
Up until now, "we the
homebuilders", didn’t have a choice for a system to automate this trimming task.
With the FPS-Plus, you can program specific flap positions, and associate
elevator trim positions with each different flap setting. It is
easy. After this is accomplished, the FPS-Plus will not only give you perfect
flap control, it will also automatically adjust your elevator trim with every
different flap position that you crank in. This dramatically decreases the
pilot’s workload if he or she enjoys doing those go-arounds or touch and goes.
For those of you that don't
like the thought of pressing a button and automatically going from flap stop to
flap stop, . . . the FPS-Plus can also be operated in the proportional mode
(mode 2). The automatic elevator trim will also be adjusted for every
flap position even if you want to operate your flaps manually. This gives
you the same accurate trim positioning that you would operating in the "flap stop to
flap stop" mode (mode 4 or 6).
My personal story and experimental aircraft
The reason I designed, built,
and tested this device in my aircraft, is because when I lowered my flaps, I had
to also crank in a good amount of elevator trim to keep the nose of my aircraft
from diving. I believe that the "more forward center of gravity
characteristic" of my aircraft contributes to the more exaggerated attitude
change when I change its flight configuration by adding a notch or two of flaps.
I really have to pull back on the control stick with a good amount of pressure
to keep the nose of my bird in the air. I need full up elevator trim to
compensate for a full down flap setting when landing to eliminate my elevator
Like many other homebuilders,
my aircraft turned out a little nose heavy. YES, I stuffed a large engine
under the cowling, and on the end of it, there sits a heavy constant speed prop!
And no, I didn't put my large battery in the baggage compartment either. I
put it where the plans suggests, right near the firewall.
One thing I must say for my critics,
. . is that my aircraft "is" within the center of gravity limits published by
the airframe manufacturer, Van's Aircraft, even with all variations of pilot,
passenger, and baggage loads.
Most experimental aircraft
companies strive to design their aircraft around the perfect design, but
sometimes "we homebuilders", pack too many goodies in there and forget about the
balance and the flight characteristics until the very end of the project.
When we finally find out the balance is not quite as good as it could be for a
perfect flying aircraft, it's too late to change the major items. We just
live with the way the bird finally flies, and sometimes we have to trim, trim,
Even if you are lucky, and
your bird turns out perfect in the weight & balance arena, your particular
aircraft's flight characteristics may also cause you to add a good bit of
elevator trim when you change your bird's flight configuration.
I found out early on, that
when I landed my aircraft, and I had full flaps in, I always had FULL up
elevator trim as well. I needed to do this to relieve the stick
back-pressure on final approach. This happened on every landing, every time, and
very repeatable. Because of this, I never really did many touch & goes
because of this characteristic. My manual electric flaps & electric trim
was too difficult to manipulate in this situation. I had to fly the plane,
talk on the radio, fight the crosswind, and hold in the flap and elevator trim
buttons, while waiting for the flaps to retract, and waiting until the stick
back pressure went away, so I could take-off again! YES, touch & goes were a
thing of my past now, at least on breezy/gusty days. I sure loved doing
those touch & goes and aborted landings just for fun. Oh well, . . .
Keeping all of this in mind, I
think you can identify why I spent my spare time thinking of a way to solve this
problem. Well, I'm an engineer, so I solved this problem by developing the
FPS-Plus. I hope you enjoy it as much as I do! Flying now is so much more
enjoyable. When I add a notch of flaps now, the aircraft just slows down.
No dropping of the nose is ever noticed. I regularly do touch & goes, . . just
for fun! It has been 5 years since I really felt comfortable doing it in my
seemingly nose heavy bird. The second time I flew with my FPS-Plus, I did many
touch & goes. I even did one with a 60° climb out with little effort on
the control stick from touch down to climb out. It's is now a blast flying with
the FPS-Plus! Everything happens so much faster and effortlessly. I don't
even use my elevator trim anymore, well, . . only to trim out a cruise leg.
The FPS-Plus has four modes
of operation, and two modes for programming.
installation, it will be up to the user to decide which one of the four modes
that the FPS-Plus will operate. There are different advantages and
characteristics to each. Below is a summary.
MODE 1 - (Proportional manual flap operation
Flap moves only
when flap button is pressed. You must keep holding the button for the flap to
MODE 2 - (Proportional manual flap operation,
with associated elevator trim following)
Flap moves only
when flap button is pressed. You must hold the button down for the flap to move.
moves with each associated flap position. This mode is a little unique. The
elevator trim will move proportionally between your programmed elevator trim
positions, as the flap also moves between its preprogrammed positions, thus, . . .
fully proportional flap and elevator trim control is achieved!
MODE 3 - (Automatic step flap mode)
Flap moves from
programmed flap stop to flap stop. One press less than 1 second (Short Press)
begins the movement, up or down. Hold the flap button for more than 1 second
(Long Press), and the flap will go all the way to its end stop. The direction
will be towards the button pressed, flap up, or flap down. If the flap is
moving, to stop it, simply press the opposite command. The flap movement will
MODE 4 - (Automatic step flap mode, with
associated elevator trim following)
Mode 4 operates
the same as mode 3 for the flaps. The elevator trim moves to its associated
elevator trim position for each flap position.
MODE 5 - (Used for programming all flap stops.)
MODE 6 - (Used for programming associated
elevator trim positions with every flap stop.)
One Touch Operation
In the fully automatic modes,
(modes 3 & 4), a “one button touch”, commands the flaps and/or elevator trim to
move. This “one touch command” moves the flap from one programmed flap stop, to
the next programmed flap stop. Holding the button down for more than 1 second
commands the flap to go to either the full up, or the full down positions. If
you decide to abort going to a flap position after you gave a command to do so,
just give it an opposite command. The FPS-Plus will stop the control surfaces
from further movement.
Installation is easy!
The only items you'll need, is the FPS-Plus, a flap motor assembly, an elevator
trim motor assembly, and two position sensors. If you want the position of
the flaps and elevator trim to be displayed on your panel, you'll need two
You can utilize most motors,
position sensors, and position indicators that are on the market today. If
you want to retrofit the FPS-Plus to your already flying aircraft, you may.
You don't have to install any limit switches to your flap system. The
FPS-Plus utilizes the output from your "already existing" flap & elevator trim
position sensors. Some motor assemblies, like the
Ray Allen Company's
motors, already have built-in position sensors.
Installing Position Indicators with the FPS-Plus:
want to use a position indicator with the FPS-Plus, please read on.
Position indicators that are presently sold by various companies, have very
different input signal requirements. Some companies have two or more
different input ranges. It is unfortunate that no standard exists for
these indicators. In order to utilize the wide variety of position
indicators with the FPS-Plus, Aircraft Extras, Inc. has developed a small add-on
pc board that will also be supplied with each FPS-Plus, at no extra charge.
Click the PIC to see how
others have mounted the
flap position sensor.
Programming is easy.
There are NO limit switches to play around with. Just put the
FPS-Plus in mode 5. Position your flaps where you want them, and press the
program button. You may store from 1 to 10 intermediate flap positions. It is your choice.
The end flap positions will be there by default.
no flap positions, will automatically give you the full up, and full down
positions by default.)
Now, change to
mode 6. You will notice that pressing the flap up/down button, now moves
the flap from your programmed flap stop to programmed flap stop. To
program the appropriate elevator trim position associated with each flap stop,
simply step thru each flap stop, then manually adjust your elevator trim where
you want it, and press the program button. You can even do this in the air
to more accurately choose the correct automatic elevator trim positions.
The system will
operate on +12Vdc or +24Vdc systems.
for each motor, 10A.
(overall) 3" x 5.75" x 1.25"
Footprint 3 x
Mounting 2 holes
in bottom flanges, 0.156" dia, 5.375" apart
What else do I need to complete the FPS-Plus
Does this system come complete with control motors,
position sensors, or position indicators?
the good news is; you can connect it up directly to most small aircraft that are
flying today, or design it into your present aircraft project. The
Ray-Allen Company's systems and other flap motor actuators systems from
Vans Aircraft are all
Can I use the FPS-Plus even though I do not have a servo
motor installed for my elevator trim?
YES - There are
selectable modes of operation that do not require the elevator trim. You may
also add a servo for the elevator trim control at a later date if you desire.
If never want the elevator trim feature, there is a version of the FPS-Plus that
does not have the elevator trim feature (FPS-Plus-nt). You cannot up-grade
it later though, so be sure before you purchase that version.
Can I adjust my elevator trim manually?
YES, if you need
to fine tune the elevator trim after the FPS-Plus has finished adjusting the
elevator trim automatically, you can do it manually. Just wait for 2 seconds
after the elevator trim stops moving.
Are the Ray Allen Company’s servos and position sensors
compatible with this system?
YES - The servos
even have a potentiometer built into them for position sensing.
Are the Ray Allen Company’s position indicators
compatible with this system?
YES - We provide
a small PC board that is used to interface between the FPS-Plus, and the
position indicators. One
board will drive two position indicators. See the explanation under
Can I use the FPS-Plus-nt on non-clutch driven flap
motors with limit switches?
YES - You will
need to connect it to the flap motor a little differently. The following
schematic should help for pre-planning.
Schematic for non-clutch flap
Can I retrofit my flying plane with the FPS-Plus?
YES - This might
take a little rewiring, but is WELL worth the effort. Probably your biggest
challenge, is to find another place to install a redundant flap switch, if you
don’t have one already have one installed in your bird.
Can I use the FPS-Plus with the TCW Safety Trim?
YES! If you purchase one extra relay board and wire it as in
the diagram below.
WIRING DIAGRAM -
FPS-Plus and Safety Trim
Can you use the FPS-Plus and the "Auto Pitch Trim
Option" for Trutrak autopilots. Are they compatible?
YES! The way the two systems work is as follows. When the autopilot
"Auto Pitch Trim Option" is turned on or engaged, it will drive the elevator
trim motor to ensure you have perfect trim. This is the case even when you
crank in a bit of flaps. The FPS-Plus will try to drive the trim motor, but it
will sense that the "Auto Pitch Trim Option " has control. The FPS-Plus will
then continue to drive the flaps, and stop its output to the elevator trim
motor. No damage will be done because the "Auto Pitch Trim Option" disconnects
all other inputs to the elevator trim motor when it is turned on or engaged.
When the "Auto Pitch Trim Option" is not engaged, the FPS-Plus will drive the
elevator trim servo motor as intended.
The way you need to connect the two systems together is simple. Just connect
the autopilot "Auto Pitch Trim Option" last. In other words, connect the "Auto
Pitch Trim Option" just before the wires go into the elevator trim servo motor.
The FPS-Plus and manual trim motor switches will be connected in series just
before going into the "Auto Pitch Trim Option".
Can I install the program button on my instrument
panel, operate the FPS-Plus in mode 6 all of the time?
I would like to store new automatic elevator
positions at any time during flight?
YES, . . . but Aircraft Extras, Inc.
does not desire to take any liability of recommending this method of operation.
Please read on.
HOWEVER, . . We
have personally flown the FPS-Plus in mode 6 in our aircraft since January of
It has functioned beautifully without a glitch. We love it. Operating the FPS-Plus in
this manner gives the advantage of being able to change your elevator trim
programming if your load changes significantly from flight to flight.
Most of the time we never need to do this, but if we load "lots of baggage", and
take a long trips with that same load, it is an advantage to be able to change
the automatic trim position any time you wish. We routinely do it during flight. If
your automatic elevator trim position isn't adjusted quite right after the flaps are
positioned, all you need to do is manually adjust your elevator trim, then simply
press the programming button. This stores another automatic elevator trim setting
in the FPS-Plus memory. It works great!
predict or control how any of
our products are used by the end customer. Every aircraft is
experimental. It is up to the builder to apply and test each and every
system in his or her aircraft. If you are going to operate the FPS-Plus in
mode 6, here are a few things to think about. I would mechanically limit
the elevator trim (if needed) so that the aircraft can be flown safely with any
trim setting. Another thing to think about would be to put the programming
button in a place where it can't get accidentally bumped by you or another
passenger. You might also
put it under a small safety door, or put another on/off switch in series with
Good luck, and
please Fly Safe!