Hi All

It's been a while since I was on here but gained some great help when building a heavyweight battle bot a few years back so thanks for that. My next daft project is to build a terminator style Hunter/Killer aircraft with no moving control surfaces The last time I flew an RC aircraft it was a box of balsa with wings and a petrol engine and the word 'Drone' didn't exist, MUCH HAS CHANGED!!!!!!! if give a rough outline of what I'm trying to achieve would someone please advise on the best thread to post a more detailed question???

HOVER MODE
I'm planning on an aircraft that uses 3 EDF motors (one on each wing tip and one in the tail) so it takes off using a flight control board like a tri-copter drone (all motors thrusting down) so take off is achieved simply by increasing thrust (HOVER MODE). The left stick Y-axis (vertical) controls all 3 motors in tandem so back = swing thrust forward resulting in backward motion, forward = turn thrust aft resulting in forward motion. Right stick X-axis connected to a rudder on the tail EDF motor so when hovering left/right spins the aircraft left /right (in flight mode it works the same as a plane rudder)

FLIGHT MODE
Left stick Y-axis all the way up puts all motors into horizontal rear thrust thus moving from reliance upon downward thrust for lift to forward motion aerodynamic lift of the wings. Left stick X-axis counter rotates the wingtip motors (so where a port aileron would go up and starboard go down the same motion is achieved by redirecting wingtip thrust in those directions). So far in flight mode we have ailerons, thrust and rudder covered leaving elevators, this is where right stick Y-axis comes in, forward = wingtip motors tilt thrust slightly up and tail motor shifts thrust slightly down - causing dive. Right stick Y-axis backward does the reverse causing climb.

THE BIG QUESTION
The rudder is simple - right stick X-axis = rudder left right BUT¬
Tail tilt servo has 2 inputs - Left & right stick Y-axis
Wingtip tilt servos have 3 inputs - Left stick X & Y axis + Right stick Y-axis

HOW???????? HELLLLLP! Using a Skyfly T6 controller BTW but thinking I'm going to have to mix Arduino with standard RC kit which scares me a bit

Cheers

 

It does not have to be that complicated. I have designed, built and flown many R/C planes over the last fifty years, of all sizes and configurations including gas and electric. I only ever used the rudder control to counter motor torque during take off and to do do fancy maneuvers like stall turns and snap rolls. I made turns by simply using the ailerons to roll the plane and applying up elevator. In your case that would be by using the wing tip motors tilt to roll and the tail motor tilt to change the pitch. If you really wanted to just change the yaw of the plane to do some very sloppy skid turns, you need to change the relative thrust of the wing tip motors.
Be aware that there is a much larger problem to overcome. That is the transition from vertical to horizontal flight.
Regards,
Keith

 

It does not have to be that complicated. I have designed, built and flown many R/C planes over the last fifty years, of all sizes and configurations including gas and electric. I only ever used the rudder control to counter motor torque during take off and to do do fancy maneuvers like stall turns and snap rolls. Turns are made by simply using the ailerons to roll the plane and applying up elevator. In your case that would be by using the wing tip motors thrust to roll and the tail motor tilt to change the pitch.
Be aware that there is a much larger problem to overcome. That is the transition from vertical to horizontal flight.
Regards,
Keith

Cheers Keith
I'm looking to achieve something like this but about 2.5 times the size with 3 electric jets rather than 2 rotors

Am looking to achieve something like this but about 2.5 times the size using 3 electric jets rather than 2 rotors

 

Good luck! It took a lot of time and research for them to get one working. The vertical take-off/landing Experimental (JVX) aircraft program started in 1981. The V-22 first flew in 1989, and began flight testing and design alterations; the complexity and difficulties of being the first tiltrotor for military service led to many years of development.
The US Marine Corps began crew training for the MV-22B Osprey in 2000, and fielded it in 2007.

 

Good luck! It took a lot of time and research for them to get one working. The vertical take-off/landing Experimental (JVX) aircraft program started in 1981.

Even earlier than that.
https://en.wikipedia.org/wiki/Bell_XV-3

 

Cheers Keith
I'm looking to achieve something like this but about 2.5 times the size with 3 electric jets rather than 2 rotors

Am looking to achieve something like this but about 2.5 times the size using 3 electric jets rather than 2 rotors

2.5 times the size of an Osprey with electric? How many billions do you have to waste on development?

 

You need to start with exactly what it is that you want .........
Is this a serious machine with a well defined purpose ?
Is this just a really cool play toy ?
Does this aircraft need to have a particular "Look",
( you mentioned "wings" and "VTOL" and "jets" in the same description, they don't work well together ).
If you can VTOL, you don't need any wings, they just complicate matters.

4 Motors/Props work better than 3, and 6 is even better than 4, and even 6 is easy to do.

Most RC "Jets" are actually "Ducted-Fans" that merely "look-like" a jet engine on the outside,
because real Jet engines are just stupid expensive, and extremely hard to control.
Small Ducted-Fans are, unfortunately, very inefficient.
Huge 2-bladed props are way more efficient, and bigger diameter is always more efficient.
3+ blades on a prop will always reduce its efficiency.

A regular old "Quad-Copter" can easily be built to do ANY maneuver, and can fly over 60mph, with no wings.
A purpose-built quad can do well over 100mph, and pull 5-G's of vertical acceleration.

GPS is a thing now, in both quads and planes, which can have position/altitude hold,
return to home, or a pre-programmed point to point flight path.

What type of flight times do you want ?
Flight times "can be" much longer if you use wings, because less total power is required.
Long flight times with a Quad, (more than ~5 minutes), usually means a larger, more "efficient" model,
this is comparing a tiny indoor quad, ( a "woop" ), with a "Camera-Platform",
with 6 to 8 huge props, which might comfortably loiter around for 1.5 hours.

"Tilt-Rotors" are incredibly complex as far as getting them to actually fly,
and transition smoothly between flight modes, it has been done though.
Tilt-Rotors are virtually required for VTOL on anything with wings,
neither Props nor Wings like perpendicular air flow,
that's why most "practical" RC helicopters have twin rotors, but that's a whole different bucket of worms.
ALL military aircraft are flown by a powerful and very sophisticated computer system, ALL of them,
they can not be flown manually by a pilot,
and things just get worse when you scale the whole thing down, and everything happens 10X faster.

Unless you are dead-set on a particular "Scale Look", I would recommend a 4 or 6 Rotor Drone.
If you want something impressive, step up to an "X-Class" Drone, (have your wallet well stocked with cash).
You can also create a light weight shell around a drone to make it "look-like" almost anything.

 

Cheers Keith
Am looking to achieve something like this but about 2.5 times the size using 3 electric jets rather than 2 rotors

Electric ducted fans are not very efficient. They are not too bad at high speeds but don't have much thrust at low speeds. You would have much better results with a two bladed prop in an annular ring.
Keith

 

You need to start with exactly what it is that you want .........
Is this a serious machine with a well defined purpose ?
Is this just a really cool play toy ?
Does this aircraft need to have a particular "Look",
( you mentioned "wings" and "VTOL" and "jets" in the same description, they don't work well together ).
If you can VTOL, you don't need any wings, they just complicate matters.

4 Motors/Props work better than 3, and 6 is even better than 4, and even 6 is easy to do.

Most RC "Jets" are actually "Ducted-Fans" that merely "look-like" a jet engine on the outside,
because real Jet engines are just stupid expensive, and extremely hard to control.
Small Ducted-Fans are, unfortunately, very inefficient.
Huge 2-bladed props are way more efficient, and bigger diameter is always more efficient.
3+ blades on a prop will always reduce its efficiency.

A regular old "Quad-Copter" can easily be built to do ANY maneuver, and can fly over 60mph, with no wings.
A purpose-built quad can do well over 100mph, and pull 5-G's of vertical acceleration.

GPS is a thing now, in both quads and planes, which can have position/altitude hold,
return to home, or a pre-programmed point to point flight path.

What type of flight times do you want ?
Flight times "can be" much longer if you use wings, because less total power is required.
Long flight times with a Quad, (more than ~5 minutes), usually means a larger, more "efficient" model,
this is comparing a tiny indoor quad, ( a "woop" ), with a "Camera-Platform",
with 6 to 8 huge props, which might comfortably loiter around for 1.5 hours.

"Tilt-Rotors" are incredibly complex as far as getting them to actually fly,
and transition smoothly between flight modes, it has been done though.
Tilt-Rotors are virtually required for VTOL on anything with wings,
neither Props nor Wings like perpendicular air flow,
that's why most "practical" RC helicopters have twin rotors, but that's a whole different bucket of worms.
ALL military aircraft are flown by a powerful and very sophisticated computer system, ALL of them,
they can not be flown manually by a pilot,
and things just get worse when you scale the whole thing down, and everything happens 10X faster.

Unless you are dead-set on a particular "Scale Look", I would recommend a 4 or 6 Rotor Drone.
If you want something impressive, step up to an "X-Class" Drone, (have your wallet well stocked with cash).
You can also create a light weight shell around a drone to make it "look-like" almost anything.

Hey LQC

Tx for the feedback, I get that EDF's are just fans that look like jets but its part of the look I'm after (see pic) and I really dont want to get into the complexities and power of real jets (plus recharging batteries is way simpler in North Wales than getting hold of highly volatile jet fuel). Stub wings as shown in the pic and as also found on high speed helicopters 'help' with lift but are still very reliant on downward thrust from single or a number of rotors, my plan is to elongate the wings (around 1.5m) I'm currently building a mini mock up to test for lift in forward flight, as for hovering the 3xEDF's will give just over 9Kg's of thrust which would be more than enough for VTOL. The 2 things I'm really needing help with is the 'fly by wire' part which you touch on in your post saying that advanced VTOL aircraft need computers. Here's what I think I need from a parts perspective, GPS so it always comes back to where it took off, 3 axis accelerometer with compass, air speed meter (GPS will give speed over ground but won't take into account head, tail and side winds) and then all the standard RC stuff such as bats, receiver, ESC's, servos and motors. What I think I also need is a way to hook in an Arduino board that can manage the fly by wire stuff and can act as an interface between the servos and ESC/EDF motors so that A- I dont fly the thing into the ground and B- the angles and thrust of the EDF's are modified to optimum levels

 

Observations ........
I would not even try to make this Model fly with actual Wings,
I think the wider Wings would detract from the overall look you are going for,
and unless you seriously increase the surface area of the wings,
and design-in a legitimate high lift airfoil shape,
they are not going to provide ~5kgs of lift at any speed under ~80k per hour.
On the other hand ............
you can make the Wings shorter, and make the Ducted Fans somewhat larger in diameter, lets say, 100mm,
and maybe only ~25mm long, now you are firmly into Tri-Copter handling, which I will get in to later.
And keep in mind that, if you use black Props,
you can't see them when they are spinning,
so you could make "Motor Covers" that look exactly like a Jet Engine,
but from a distance, there are no visible Props.
The Tail Motor could be mounted up-side-down, in a "Pusher" configuration,
but this might put it in danger of contacting the ground, unless the Tails are wide enough,
and extend low enough, to keep the Prop clear of the ground.

The problem with actual Flying on a Wing is that
the Center of Gravity MUST BE located within the front 1/3rd of the Wing Chord,
so since the Tail Motor can't instantly reverse, and doesn't have variable pitch like a helicopter Tail Rotor,
the Model MUST BE MADE TAIL HEAVY in order for the Tail Motor to have something to push against,
otherwise you would just have to "turn it off", and then raise the "Point of Thrust" of the Wing Motors to
a position located above the Center of Gravity so that the weight of the Model can
stably "hang" or "balance" below the Thrust of the Motors,
but of course you "could" mount the Wing Motors well forward of the "Center of Lift" of the Wing,
but this probably wouldn't achieve the "look" you're going for.
A "Tail-Heavy" Airplane is a crash looking for a place to happen,
that is, if you can get it to fly in the first place.

Now the good news ...........
With 3- ~100mm Fans, YOU DON'T NEED A WORKING WING THAT PROVIDES "LIFT",
a standard Tri-Copter setup will fly it with no issues.

Now comes the tricky part ........
You may not care for the "look" that you get when you shove the Stick Forward,
the Model will go "Tail-High" to accelerate forward at high speed.
This might be just all fine and excellent, it's your call, after you see how it responds.
Try this FIRST, without tilting the Fans, it may be totally acceptable to you.

If this is not acceptable flight behavior then ..........

The Fix for this is probably built-into your Flight Controller Receiver, (or at least it is on mine),
the "TBS CrossFire Diversity Receiver" has plenty of un-used PPM Outputs which you can setup to
operate Servos by way of the Mixing Setup Functions in your Transmitter,
then you can have the "Pitch Control" rotate the Wing and Tail Motors with Servos,
in "some" proportion to the amount of Pitch Commanded,
this will tend to "flatten-out" the Pitch attitude of the Model,
and keep it more "level", when making quick moves, forward or back.
But, I would not attempt to rotate the Motors more than ~45 degrees, in either direction, away from from flat,
if you do this, the Flight Controller may get confused and act in a strange manner, or crash.
The "Roll Control" will not need compensation.

If I remember correctly,
the Tail Motor will need 2-Servos if you want to retain Yaw Control on a Three-Motor setup.
But then there is the "Mixing Solution" again,
You could "mix-in" opposing tilts on the Wing Motors for Yaw Control.

An alternative arrangement could be .........,
instead of only one Motor out back, you could run one on each side of the Tails,
( or have 3-Motors, with the center one being a fake ),
both still mounted up-side-down, and both Tilted with a Single Servo,
this would eliminate the need for the second rear Servo for Yaw Control,
and would mean that your Model will automatically have the ability to fly exactly like any other Quad,
then, after you have a stable, controllable platform, that you can actually fly without crashing,
you can then work on tweaking things to make it act more like you may prefer.

Some interesting notes ........
As long as the Flight Controller Board stays on the same plane level as the Props, it will fly perfectly.
When You move the Sticks on your Transmitter,
you are commanding a change in the attitude of the Flight Controller Board,
NOT NECESSARILY THE BODY OF THE MODEL,
The Flight Controller Board will then do whatever is necessary to comply with your demands.
There is no "Forward Stick", only tilt left-right, tilt front to rear, rotate in a circle, and, go up or down.
But you can set up a 3-position switch to tilt all Motors to 2 different forward angles,
this may provide the "illusion" that the Model is flying straight and level on wings,
when it is not really "flying" at all,
it's "hoovering" and "sliding around" in what ever direction you choose.