VTOL Explorer

by Ran D. St. Clair | August 20, 2016 | (20 Ratings) Posted in Projects

VTOL Explorer Build Instructions


The VTOL Explorer (Vertical Take Off and Landing Explorer) is a “kit bash” project based on the Flite Test Explorer. It is designed to be easy and fun to fly in all flight modes from hover to Fast Forward Flight (FFF).

 As an airplane, the VTOL Explorer is very normal.  It does all the typical maneuvers you would expect of a trainer including inside loops, rolls, and inverted flight (barely).  It is a bit heavier and more complex than a typical trainer, and is not very fast.  The rate of climb is modest.  Flight times are about 7 minutes with a 3,300mAh battery and good safety margin.

As a quad-copter the VTOL Explorer is very easy to fly.  It is mostly auto stabilized by the onboard electronics.  I would not recommend it as your first quad-copter only because there are excellent, cheap, and extremely durable quad-copters that you can learn to fly in your living room.  If you can comfortably hover tail in, meaning the aircraft is facing away from you, then you will have no difficulty hovering the VTOL Explorer.

Transitions from hover, to SFF (Slow Forward Flight), to FFF (Fast Forward Flight), and back again, are as easy as flipping a switch and flying the plane.  SFF is the easiest flight mode, ranging from gentle cruising in airplane mode to a nose high hover.

The VTOL Explorer handles a modest amount of wind with ease.  It flies at any speed from slowly backwards to full forward flight. You can point the nose into the wind, match your airspeed to the wind speed, and hover for a takeoff or a landing.

A video of the VTOL Explorer in flight is available here:

The PDF file of the build instructions is too large to be included here. It, and all of the related files can be found here.  If the links don't open with a left click then try a right click and open in a new tab:  


 OpenAero-VTOL Support Thread. Get the latest firmware and ask your questions about the firmware here:


OpenAero-VTOL GUI Support Thread. Get the latest GUI (Graphical User Interface) and ask your questions about the GUI here. The GUI is not absolutely necessary, you can always enter the user parameters via the 4 button and LCD interface on the KK2 board. Recommended for users with more advanced PC skills:


The build instructions are based heavily on the excellent Flite Test build video located here:


The original build thread can be found here:



Weight ready to fly:  3.47 pounds with battery.

Weight without battery:   2.9 pounds

Wingspan:  56”

Wing Area:  398 sq. in.

C.G.:  5.25” behind the wing Leading Edge

Typical Flight Time: 7 minutes

Lift Motors:  Flite Test Power Pack D, (4) Emax 2213-935kv

Lift ESCs: (4) Emax BL Heli 20 amp XT-60

Lift Propellers:  Emax 10x4.5, (2) CW, (2) CCW

Forward Thrust Motor: Flite test Power Pack C, Emax GT2215/09

Forward Thrust ESC:  - Emax BL Heli 30 amp ESC

Forward Thrust Propeller:  9 x 6 EP, APC

Battery: 3.3Ah, 25-50C or better

Servos: (4)  Emax ES08A II 8.5g

Flight Controller:  KK2.1.5 or KK-mini

Flight Controller Firmware:  OpenAero-VTOL

Measured Power/Lift:

3.8W - All motors off

204W, 11.48V, 17.8A – Hover Power

450W, 10.98V, 41A – Full throttle, hover motors only

6.5 lbs. – Maximum Hover Lift

101W, 11.64V, 8.7A – Minimum forward flight at cruise, forward thrust motor only

225W, 11.43V, 19.7A – Full throttle, forward thrust motor only

Parts List

Most of these parts can be obtained from the Flite Test store, and equivalent parts are broadly available.  Some of the simplest and most common parts such as glue and tape are not listed. Obviously, you will need to make substitutions to match your radio.

FT Explorer Speed Build Kit, $39


Power Pack D (Standard Quadcopter), $120


Power Pack c (Fixed Wing Large), $65


FT Elements Simple Firewall , 4 each, $5 ($20 total)


 Female XT60 Connectors, $4.50


Male and Female Bullet Connectors, 3.5mm, 12 pairs, $5.25


Flite Test Water-Resistant Foam board by Adams (50 pack) , $80.00 (Need 1 sheet)


Turnigy nano-tech 3300mah 3S 25~50C Lipo Pack, $28.34


Hobbyking KK2.1.5 Multi-rotor LCD Flight Control Board With 6050MPU And Atmel 644PA. $19.99


ZYX-S S.BUS Connection Cable, $3.47


Orange Rx R620X V2 6Ch 2.4GHz DSM2/DSMX Comp Full Range Rx w/Sat, Div Ant, F/Safe & SBUS (Any size RX with S.bus and satellite capability will work), $20.64


OrangeRx R110X DSMX/DSM2 Compatible Satellite Receiver (Any compatible satellite RX will work) $12.79


USBasp AVR Programming Device for ATMEL Processors, $3.99


Colored Acrylic Packing Tape, 2” wide, $3.95 each


Amazing Goop, $8.00, Any hardware store


12 AWG Primary Wire, Any Color, $5.00, 1 foot, Any hardware store

18 AWG Primary Wire, Any Color, $5.00, 17 feet, Any hardware store

Terms of Use

The unique aspects of the VTOL Explorer design are offered freely for use by anyone, commercial or private.  If Flite Test wants to offer a speed build kit for the motor pods, etc. they are welcome to do so. 

The base Explorer design is the property of Flite Test. 

The KK2.1.5 and KK-Mini design are the property of HobbyKing.

The OpenAero-VTOL (OAV) Firmware is open source and subject to the terms and limitations in the OpenAero-VTOL User manual.

If FliteTest wanted to offer the KK2 pre flashed with OAV, and possibly even loaded with the specific user parameters for the VTOL-Explorer then I would be happy to work with them to make that happen.  Flashing the firmware is a significant entry barrier for many new users.


hugob33@gmail.com on August 27, 2016
I think this is an awesome improvement to the Explorer, I absolutely love to build one...saving my allowance for it...the only thing it is not mention is the transmitter radio type and set up, I have an DX6i which is probably good enough, although I wish some verify that. Thank you.
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sconner on August 27, 2016
Great video and article Ron! VTOL fascinates me.
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Ran D. St. Clair on August 27, 2016
"I have an DX6i which is probably good enough, although I wish some verify that."

A DX6i will work, it has 6 output channels and only 6 are needed. It is not ideal because it lacks a 3 position switch, and only has a 2 position switch. That means it would only be able to provide 2 output levels to drive the flight mode, presumably Hover and FFF (Fast Forward Flight). The intermediate mode, SFF (Slow Forward Flight) would not be possible unless you used various mixes to combine multiple switches to create 3 output levels (-100,0, +100) which is possible but a little messy. Also, when calibrating the inputs you really need the transition control output a 0% or neutral 1.5ms pulse, otherwise the FC (Flight controller) will assume neutral is whatever it happens to be putting out, when you push the calibration button. Once again, this can be done in various ways, including by temporarily programming that output to be neutral, but it is inconvenient. Bottom line, a DX6i is more than good enough except for the transition control output where it is less than ideal but still workable.
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Ran D. St. Clair on August 27, 2016
Correction, only 5 channels are needed, not 6. ( I wish there was an edit function so I could fix my mistakes....)
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Ran D. St. Clair on August 27, 2016
I just programmed it up on a DX6i using a combination of the Flap switch and the Gear switch. I set the flap switch to 100% for both the up and down switch position, and then I inverted the polarity of the channel 6 output. Then I used Mix 1 to mix in Gear at 100%. The net result is -100% out with both the flap and gear switches down. 0% with the Flap switch down and the Gear switch up, 100% with the Gear switch up and the Flap switch down, and something like 150% with both switches up. That last one doesn't matter because it will be seen as a +100% input by the KK2 running OAV so in fact there are only 3 possible states.

When calibrating it would be important to set the flap switch down and the gear switch up, the position that outputs a neutral 1.5ms pulse. Confirm proper functionality on the monitor screen.
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Ran D. St. Clair on August 27, 2016
Correction, that's 100% out with the flap switch up and the gear switch down.
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hugob33@gmail.com on October 15, 2016
Thanks again Rand.

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llharper on August 28, 2016
I have been away from flying for a while. This just might get me back in!! Great job!!

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fireshovel on August 28, 2016
Thanks for the great article Randy! Just ordered a couple "spare" KK boards, now I know what they are going into. Thanks again!
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steadfast4life on August 29, 2016
This is so sweet! I have been waiting for a VTOL for awhile. I'm gonna swing this! It is exactly what I was looking for and I will definitely be in contact. BRAVO!
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PeacePilot73 on August 29, 2016
Wow, amazing job! I wouldnt have thought of doing this, its a terrific idea.
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steadfast4life on August 30, 2016
Do you need all the same escs and motors? My questions relates to the pusher. Does it need to have the same motor and esc as the hover motors and escs?
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Ran D. St. Clair on August 31, 2016
The lift motors are the FT Power Pack D with 20A ESC's. The forward thrust motor is the FT Power Pack C with a 30A ESC. The links to both of these are in the article above. The full detailed build instructions are available here: https://www.dropbox.com/sh/njtenb8l0j5csb4/AAAj2RpwOic2kop3_YheUYuCa?dl=0
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ttprigg on August 30, 2016
Great job Ron- I think you have pushed me to the edge... I'm now excited about VTOL!
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Talsharf on August 30, 2016
This is a great article and an amazing project!
5 stars from me!
I really wish FT would take the opportunity and will make a kit out of this. People have been asking for VTOL kit for a long time.
Great job!
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Gravitysucks on August 31, 2016
Fantastic !! I have been waiting for FT to come up with a VTOL project that includes software and all but no show (unless i've missed it). But this is just great :D

I am a fixed wing guy but I'm fascinated of the drone technology so this project will definitely get me going. And since it has the beginner mode it looks perfect for a noob like me.

Excellent work. 5 star quality.

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oldjoe1931 on September 16, 2016
Great job Rand D St Clair! You helped me get a Flite Test Bronco VTOL flying. This looks much simpler without having to deal with the tilt mechanisms. This is my next project. You guys are great and so willing to share. I still have lots to learn..........this is the coolest stuff.........VTOL.

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hugob33@gmail.com on October 15, 2016
Looking at the (great) list of materials you provided, I notice that the build requires an additional sheet of foam board, which is not sold by the piece and I don't need 49 spare sheets of board or pay to $90.... could I replace that extra foamboard with a standard $1 DTFB?
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Ran D. St. Clair on October 15, 2016
Yes, standard Dollar Tree Foam Board should work fine. It won't be water resistant, and it will be white instead of brown, but structurally it makes no difference. Just make sure whatever you use is 3/16" thick, otherwise the template I provided won't work.

Some people have also made the motor pods out of a solid piece of wood. That is a better solution in some ways if you have the necessary tools. You can make them thinner and more rounded for better aerodynamic efficiency.


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Ran D. St. Clair on October 30, 2016
OpenAero-VTOL (OAV) V1.5 (the latest version) is now available pre-flashed on a KK2.1.5 board from Altitude Hobbies.


Several people have asked for this as it is sometimes difficult to get your PC configured with the proper drivers, application software, and of course you need the programming cable. You will still need to enter the parameters for your specific aircraft, but that is what the buttons and the LCD display are for.

If you are going to use OAV in a number of projects, then it is probably worth your time to learn how to flash the boards yourself, but if this is your first OAV project, then it is well worth it to just buy the board pre-flashed.

I should point out that this powerful firmware is useful for much more than just VTOL aircraft. It is a general purpose flight controller that can be used in all sorts of aircraft and for all sorts of purposes. People have even used it in cars to control oversteer. It can turn most any aircraft into an easy to fly trainer and is also a lot of fun in 3D aircraft that can be made to auto hover. I don’t recommend it for simple multi-copters as there are better and simpler dedicated flight controllers for that purpose, but it can fly multi-copters as they are often a part of VTOL aircraft. It has a general purpose and very flexible user interface that is not aircraft dependent. The user manual and supporting documentation are very complete and combine with the board to create an excellent educational lab for understanding the basics of flight stabilization.

Ongoing and free product support is offered via this RC Groups thread:


The user manual and other detailed documentation are available here:


If you want to use the Excel based GUI (Graphical User Interface) you will still need to set up your PC to flash the board yourself. Fortunately, the GUI is just a convenience and is not necessary. The on board buttons and LCD display are all you need. The GUI is available here:


Thank You to HappySundays for making all this possible.

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jimmyp39 on February 13, 2017
I have programmed everything and am doing a bench test. I have set up my 3 way switch to -100 in off position , 0 in the middle position and +100 in the third position. The transitions seem to be working as when I go to the middle position the forward motor starts to run slowly and the lift motors slow slightly. When I switch to the third position the forward flight motor ramps up more and the lift motors slow but not shut down completely. I need some help to figure out why this is happening.
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jimmyp39 on February 13, 2017
Actually with some further testing I can see that in quad mode the forward motor spins as I increase the throttle and in forward flight the quad motors spin slowly then increase in rpm as I increase the throttle stick. Neither one stops completely in either mode? Any suggestions?
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Ran D. St. Clair on May 10, 2017
It sounds like you need to do the receiver inputs calibration per the OAV user manual. Specifically the receiver input menu #3 needs to read -1048 when the switch is down and +1048 when the switch is up. if that is correct, then I suggest you calibrate your ESCs. The procedure for doing that is also in the OAV user manual as well as in the article I published.
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chrisrohrer@gmail.com on February 17, 2017
Thank you Randy for all the hard work.... VTOL has also been a dream of mine for years.... !!
Can you point me to the settings for the flight profiles... I found one that I think will work, but I am keen on saving all three to mess with.... I just ordered a FT Explorer, and all the parts to replicate the machine you made the video of... Again.. Thanks for all the hard work over the years.... I have followed your work for quite a while.. !!!
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Ran D. St. Clair on May 10, 2017
All the files you need can be found by clicking the first link in the article. The programming parameters are in the file, "OA_VTOL_Program_Template_V1.4_Eplorer.xlsx".
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SlingShotRC on May 12, 2017
Pretty slick. I now know where to go for a beginner VTOL project 8-)
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cmsrujan@gmail.com on May 12, 2017
can i have your Flight profile 1 settings and offset value of motors. I am trying from long its been very difficult to make my quadplane fly. It is unpredictable behaviour
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Ran D. St. Clair on May 25, 2017
The programming parameters are in the file, "OA_VTOL_Program_Template_V1.4_Eplorer.xlsx". As I recall, the motor offsets are 0, assuming that the ESCs are properly calibrated.
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NebuCat on May 25, 2017
Awesome and very comrpehensive build instructions! This will help me a lot with my own build project based on the KK2 :)
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Dutchie777 on June 1, 2017
Hi Randy
Tks for a great project and all the work that you have obviously put into it.

Just want to check with you first. Can I use a KK mini instead of a KK2.1.5. The mini has the 6060MPU and Atmel 644PA, but not sure about memory space etc. Yes the conections are a bit different.
Here in Australia can only get the mini from HobbyKing. Could go on Ebay and buy and pay a heap for one, but never sure what you are going to get from the chinese.

Tks Ken
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Dutchie777 on June 1, 2017
Randy......Sorry 6050 MPU
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Rondinele Brito on June 29, 2017
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