350 QX Body Replacement


This write up is to help other with the replacement of a damaged 350 QX body. The body of the QX is the most fragile part (perhaps after the plastic props) and will most likely be damaged with a crash. I broke an arm off each of my two first bodies I had when I was learning and flew beyond my skill level. It's now been about two months since I did this procedure but the steps below are basic and should act as a tutorial.

Here is the documentation from the manual. I chose to post the new QX2 instructions because this shows the GPS in the correct location for the first gen. QX with the V2.0 firmware. LINK



Horizon Hobby Parts Finder Ė All Multirotors LINK

When tuning or doing repairs, always be sure to remove your props!

Now for my side of the story.    



The Props come off 1st. You may want to note which mount to each corner motor. Red in front and gray go on the rear. Each motor has a curved arrow on the them that matches the arror direction on the body arm next to the motors.

Next I took the 2 screws out of the legs but leave them mounted in the body. This helps you stand the QX up normally while working on it. Do not remove the compass that is screwed into the foot of one of the legs. If not damaged you'll unplug it from the main flight control (FC) board later.

Put a strong rubber band around each arm to hold it all together until the body screws are out. This is because you'll be turning the QX over to get to the body screws.

Remove the camera mount now. The four screws come out without taking the mount apart. The rubber balls can stay in place. You need to remove this mount to get to two of the body screws.

Now remove all the motor screws except one from each motor. Turn that last screw on each to loosen it just enough to break it free. Be careful to not damage the very small plastic posts that align the base. You are keeping it in so that the motor doesn't flop around while you handle the body.

Remove all the small 1.5mm body screws. Here is my list of each screw size where they go and how many. I also put them in half an egg carton bottom as I remove them.

Hardware Inventory:
Usage Qty.     Size
. Props 8      2.0mm w/blue thread lock
. Camera Mount 4      2.0mm
. Body Shell 32      1.5mm
. Motors 16      2.5mm w/blue thread lock
. Legs 2      2.0mm long
. Motherboard 4      Phillips small
. Compass 2      Phillips very small brass

Now set the QX on its legs right side up and take the rubber bands off. when you lift the top of the body off stop and take pictures of the internal components. You may want to reference them later.

Unplug the compass wire coming from up the leg where it plugs into the main board. I touched one end with a sharpie putting a dot on both the socket and plug before unplugging, helps later.

Almost apart. Now the difficult stuff. I use the smallest screw driver I have (tiny) and pry the covers off each of the motor pod lights, careful. Now the LEDs can come out, upward, looks easier that it is. Now to the rear flight mode light. Again with the tiny screw driver pry one of the tabs from above and pop off the clear cover. From below gently pry the tiny LED board off. It is stuck on with sticky foam. Notice that 2 very small posts from the body poke through this board, remember for reassembly.

OK, take the last screw out of each motor. When you lift a motor off you'll see tiny posts that align the motor base to the body. You'll need to put the motors back on allowing for these posts.

I have a first gen QX with firmware V2.0 so my GPS board is attached to the rear of the battery box with two sided sticky, pull it apart. Lift the battery box straight up it has 6 posts that connect it to the bottom body.

Now you can see the main board. Four tiny Phillips screws hold it down, remove them. Now I put the new lower body next to my old one on the table. Align them both the same direction, lift ALL the internal components up and over to the new body shell.

While it's open sight check everything. Is everything plugged in (except the compass)? Any visible damage? Turn the motors by hand are they OK?

Now reverse the process. When you have the screws in each motor you can plug in your LiPo and power on. Check for light and sound error codes. You can even bind and start the motors if you want to test them (very slowly). Check your props carefully if you crashed, I advise a new set. If this is the 1st time changing props it's a good time to balance them. If you have everything together and didn't pinch any wires you are almost ready to fly. But do ALL of the calibrations before going out. The videos are on the Blade site.

The three calibration instructions are here. LINK I've been told by HH support that if you have firmware V2.0 you should use the QX2 instructions for the accelerometer calibration. That is what I'm showing at this link. Notice that it does not mention using the TX trims to stabilize the hover. This is because the RTF QX2 comes with the DX4 which doesn't have trim tabs.

Well it happened. While trying to perform an accelerometer calibration I impacted the ground hard (feet down) which caused the QX to bounce and then flip over on to its props in short grass. I had damage to the body, mostly where it had been glued a prior time. I ordered a new body shell and purposely checked for the QX part number BLH7811. However I received the new QX2 part BLH7811A. Looking it over, it doesn't have the flat area on the bottom toward the front anymore. Also the inside of the rear arm that contains the GPS antenna seems to be cleaned up. It does have the new QX2 logo on the top just ahead of the battery door. I was led to believe this new body might be bigger/fatter and stronger. I'm not seeing either of those. Everything transferred over well and the fit seems fine. I'll redo each of the calibrations and be back in the air.


Good luck



Crashing: My brother-in-law was a very good snow skier when younger. One day I asked him if he fell much. He proudly said "Yes, I do.". But then added "If you're not falling you aren't trying hard enough.".

Tip: If you replaced an electronic speed control (ESC) board, located in an arm, you will get beeps and flashing codes. This is because you must do the motor assignment procedure. The ESC and motor assignment procedure is here. LINK

Tip: Remember my tip about using thread lock as applied to the prop and motor screws. LINK

Tip: When in trouble go up. Up is your friend, so if you lose sight of your quad or just orientation go up. Not only is it the direction where you'll be lease likely to hit something it also gives you time to think and recover. 4_Props



I'll be adding more detail to this draft. Sooner if I have to replace my 3rd body.





I plan on putting my 350 QX back together soon, getting ready for Spring. I'll post some pictures of the few modifications I've done on it here. Stay tuned.

Or you could just fully replace the plastic body with a carbon fiber one. As I've said before the body shell is very fragile. For the amount of $$$ I've put into replacement bodies I could have already had one of these. The CNC Aluminum/Carbon Fiber Quadcopter Frame Kit - BLADE 350 QX from MicroHeli.com. If you want to dress this frame up a little check this out. LINK You might get a better deal from Horizon Hobby if you have a discount code. Here is a great review of the CF frame from ap308 that he posted on RCgroups. Another frame is the Phoenix Flight Gear Blade 350Qx/Qx3 CarbonSpider Foldable 378mm Quad Frame. LINK Or even this one $72 eBay. LINK Be sure to look for the model GF-360V2 the V2 = Version 2. Then again some people, me included, are waiting to see if Rakon Heli will do a 350 QX body. LINK Look for it sometime in July.

And here is a flight test video. The 2nd half is at night and shows off the lights. Here is another video of the MicroHeli CF frame this one by JohnCC on RCgroups. LINK



He's another option - Blade 350 qx FPV Body Kit Freestlye Graphite Shielded w Antenna Mast LINK and Blade 350 qx 1 / 2 / 3 FPV Body Conversion Kit LINK



The new carbon fiber body from Rakon Heli has caught my eye. LINK and more images here LINK. I'm still waiting for a good build video or a pdf of the build manual to post. Here is what gayjuanbarty from HeliFreaks has to say about the kit. This video doesn't really show the body LINK You

I've already migrated the 350 guts to the new RakonHeli CF frame. I've learned my lesson after paying for all those 200QX replacement bodies. I've done a few test flights and everything is functioning properly so far. I'll swap out to CF props for testing in the future. I would rate the RakonHeli frame 4/5 stars. I deduct 1 star for providing only 1 battery strap (2 is really needed), designing a compass board that does not fit the QX3 compass (wasted my money on that), mounting the compass board on the body too close to the FC board (interference), and having only basic assembly instructions (need to plan your own transplant locations for components). Be aware that plugging the motors into the ESC leads can be a hassle as the motor leads a very short and must pass through the motor mount first. I couldn't figure out a way to insert the motors/ESC connected through the mounts and into the arm tubes.

To enhance visual orientation, I cut 2 strips from a fluorescent yellow index card and wrapped it around the front arms with clear tape. They are extremely effective, and the dark silhouette of the CF frame against the sky is easier to see than the stock white body. I fabricated landing skid mounts from a piece of 90-degree aluminum from Home Depot and cut lower, longer landing skids from 1.5mm CF plate. The 350 is now much more stable upon landing and the possibility of tipping over is pretty much eliminated. I ditched the GPS mast and added left/right navigation lights even though I don't fly at night. Overall, I like the kit and would recommend it over the fragile stock body.

Click images to enlarge, close new window or tab to return.
The 1st, 10th and 12th boxs are of other builds, note the Xtreme CF props and CNC prop caps. WOW! Box 11 has a YouTube of the green one. This does not show the NEW body cover, but the gold one has it.




The forums still have a lot of discussion on flyaway's. Many of the more experienced guys claim it's pilot error. I just can't buy that. Just way to many for this not to be a malfunctioning device. Whether or not it's RF interference from a mounted camera I'm not sure. But the DJI and other GPS guided quads like our 350 QX all seem to suffer the issue. I had hoped to get a number of replies to my poll question (below) as I had been picking up on a trend that most flew off to the North. At this point I just don't have enough data to follow up on this thought.

Truly superior pilots are those who use their superior judgment to avoid those situations where they might have to use their superior skills.

Any situation that any pilot may have successfully recovered from or any situation that was at least "in part" contributed through poor decision making is simply a pilot error. Not knowing how the 350 will react in certain situations because a pilot did not read the manual, or even did read the manual but did not confirm it through his/her own testing is not an excuse, it is just pilot error. At nearly every step of the way the pilot made a decision. Those decisions may look like the following.

  • How tough can it be, it says safe on the box so why read the instructions. Go for it.
  • Its just a toy.
  • Hey, after one successful flight, I am going for the altitude record.
  • I can't wait for the wind to die down. Gotta try it out now.
  • After opening the Christmas present, "Honey, hurry grab the camera, I am headed for the driveway."
  • What do you mean the batteries are not fully charged out of the box?
  • Well, I am sure I read somewhere or over heard someone saying the batteries are good for 25 minutes.
  • During flight, Hmmmm, better read up on that, so if I let go of the sticks, it will hold while I read page 16.
  • Had an orange flashing light, but I flew it anyway.
  • Only one nacelle was cracked after the crash so I flew again.
  • The guy without a battery checker, "but I charged them all last night."
  • I read it is better to fly without GPS, so why did it fly-a-way in the wind when I let go of the sticks?
  • After take off I followed the 350 around the trees and between the two houses, so why didn't the 350 land at my feet in RTH mode. It just took off on its own and I had no control!
  • It would not start when I advanced the throttle so I went online to find the answer (but didn't read the manual)
  • If the battery says 2200 on it, it should fly to at least 2150, right?
  • It flipped on take off, so I put it back on its feet and tried it again and it flipped again. It did it again the third time. Wait, you mean the props go on a certain way?
  • I crashed and cracked a prop, but it looked OK so I flew again.
  • The ticking noise from the one motor didn't sound that bad.

Then there are situations that you can't prepare for because you didn't even know what question to ask.

  • Ring Vortex State - Really, why didn't anyone tell me?

These are all examples of something actually reported on this thread. None the less, they are all examples of Pilot Error.

I could explain away most of the reported Fly-a-way's simply because the pilot reporting it didn't really understand the definition of a Fly-a-way. You stated it best when you used the phrase "explainable departure from expected operating behavior" is much different from a Fly-a-way. (I am gonna write that down somewhere) Your phrase is the reason the rate of report rejection was so high when I started the data base. Not every post of a fly-a-way can be explained. But I also discovered this. A report that was verbal and unexplainable would often be explained later after reviewing the video.

Sherman Knight (RCgroups post #24404 3/17/2015)
Team Horizon Hobby Sailplane.

A larger poll has been started HERE. Summary of responses LINK . Take a moment and fill it out even if you have not had any issue.

Flyaways are still being reported.
Please take my poll if you have experienced one.
Loading web poll...

This story isn't done. I was very happy with migrating the internals over to the new body shell. I did the pressure and compass calibrations, accelerometer delayed until a calm wind. I'm getting good at this and my few mods were done even better this time around. So out to fly it in the field. This was a test flight so easy does it. I took off in Smart mode and checked it out. Stick relativity was good so compass Ok. Flew a few large loops of the field at about 18MPH while changing direction and spinning with the rudder. Then brought it in with RTH and it did fine. The props stopped as they should and without turning off the QX or DX6 I initalized the props and lifted off again. I flew out about 150 feet and lost control. The QX was not responding to any right stick movement. It started flying back at me way faster than Smart mode speed (est. 50MPH). It went over me and was headed for a large building, I had very little time to react. I hit RTH as it had just worked. Nothing. The QX was in a downward flight path, I dropped the throttle and just before it hit the building I hit throttle cut. My QX had a lot of forward speed it ended up on its top in short grass just feet from the building. I check it over and no apparent damage was visible. I packed up everything and headed home.

Home I checked the obvious, battery OK, DX6 OK and switches all right. So I called HH Heli support and waited for a call back. When I got my call I went through it all, including the just finished body shell replacement and the rep. was stumped. He suggested I send it in for service. I agreed and opened a case on the HH website. Now I need to open the QX up again and remove my lights, Flytrex, and swap out my Xtreme props for "B" props. Monday I'm mailing it out.

There has been some interest in this event on the RCgroups forum. Here are some links that will provide data on the crash.

  • This is the Flytrex page for the flight. LINK
  • This is the Excel spread sheet with all the details. Download
  • Here is the file to use with Google Earth to better see the flight path. Download

    Please eMail with your comments.

  • USPS is slow as it's going to take until Saturday to get from Syracuse, New York to Champaign, Illinois. I've put my LiPo's into storage charge (3.85V). Told my story to LHS and they think I'll be covered by warranty and should expect a good ending to this tale. I have always heard GREAT things about HH support. This is one of the reasons I went with Blade and Spektrum when I selected my 350 QX & DX6. If I wasn't covered by HH I likely would have sent it out to Jeremy James at USdronerepair.com. (see below)

    I mailed my package out Monday, it's now Tuesday a week later and the USPS just reported it "delivered" in Champaign.     Now, a couple of hours later, I just received an email from HH service stating they have my 350 QX It's now Friday and two weeks have passed since I crashed and called HH support. Still no information about my 350 QX.

    3rd Monday:
    Well I just got an email from Horizon service stating that my 350 QX was being FedExíed back to me. I called and asked what had been found and how it was repaired. They said that it was opened up and looked at, nothing found. The calibrations all checked and all found to be OK. Next they test flew it and again it was fine. They tried a 2nd radio with no problems.

    Letter text:
    Inspected your Blade 350 QX Version 2 BNF sent in for service. Took the quad apart since it has been apart before and checked all the wiring and made sure everything was alright. Main board seems to be binding to my DX9 fine and didn't see any signal issues. Put the quad back together and test flew it and didn't have to make any calibrations or anything. Quad tested out perfect. GPS locked good and flew it in all modes. RTH and the safe circle feature all worked. Flew it a couple more times using different batteries and transmitters and had perfect problem free flights. Returning the quad to you at no charge. Hopefully the calibrations to the compass fixes whatever the problem was. If you have any questions at all, feel free to give our product support team a call.

    Thank you Horizon Service for checking out my model. And not even charging me anything was very nice.

    So bottom line no repairs done. Well now if I have a real flyaway and crash or lose it I have documentation Iíve had issues. I have it now and Iíll do a range test with my radio and activate some of the telemetry warnings. This doesnít give me a great feeling that Iím 100% good to fly. It also concerns me when thinking of adding another $300+ to its belly with FPV gear.

    So Iíve been grounded for 2+ weeks but it only cost me the shipping out to HH not to bad if it works. Iíll need to open it up and put my mods back on. The Flytrex unit has a firmware upgrade waiting to go on. I also have a Mobius firmware upgrade to test. I know I missed some great flying weather.

    The story now continues.

    I opened up the box my QX was shipped in and started to put my Flytrex back in. I was removing the props and noticed one motor was loose. So I fully removed the top half of the body. That one motor mount was damaged. three or the four posts that the 2.5mm screws go through were broken. I have to assume that this happened when I crashed when forcing down my flyaway. I had not noticed it before sending out my quad but then I never looked. I called HH support and talked to them and they said that they only checked the wiring when they opend it up. And it passed the test flights. I could send it back if I wanted if I were not able to swap a body myself. I passed on that. I called the LHS where I purchased my quad and radio and updated them to what I had found and what HH had suggested. They were surprised that Horizon didn't offer me a replacement body shell. They asked if I wanted them to call HH on my behalf. I said yes if they had anymore pull than I did. I got a call back shortly after that and they said HH wasn't taking any responsibility for the issues. I just ordered another QX body from the LHS. I got about 8 minutes of flight time out of that last one.

    One of the reasons that I went with the Blade 350 QX and Spektrum DX6 was because of Horizon Hobby's legendary support. I'm now questioning my decision. I love flying this quad. But I've been grounded so much, loosing many many days of flying that my enthusiasm is down. I'll get this next body and put it all back together and fly again but the season is almost over. I'll have the winter to follow the hobby and see what new directions are available in the spring.



    I mentioned my flyaway experience in the RCgroups forum and user 'burlbark' responded with this.


      You are showing the MPU-6050 symptoms. This component was improperly soldered onto the flight controller. Read pages 42-43 here.....

    I have repaired nearly a dozen now. It's always the same flyaway symptom, often after crashing you will get the error code and failure to initialize.

    I have to remove the component and scrub every last trace of solder off the board and component and flux the daylights out of it bringing the temperature down over 5 minutes.

    It shows itself either on start up as a accelerometer error or it shows up after you are up in the air and it decides to fly away. You should be able to cut throttle and drop it before its out of sight. It should go into lost tx mode and start to land but it may just stay ramped up because it is trying to level itself. Its all luck of the draw.

    This will become more prevalent as the boards begin to warp and the resin continues to cure causing stress upon the component. I did a little write up on it at my website that pretty much explains everything I just wrote. I hope the manufacturers can take note and fix this, it destroying our hobby...... Flyaway

    Jeremy James

    Well I've been sitting here (after heart surgery) and thinking about some of my flight issues. Now I'm thinking that perhaps a couple of my problems were not flyaway issues but rather range issues. Twice at more than 500 feet out my QX flew erratically/uncontrollable and crashed. Perhaps I'm pushing the range of the stock receiver antenna. The Original short antenna was replaced by a longer dual set of antenna wires in the QX2. I'm sure my DX6 is reaching 1,000+ feet OK. At this point I'm thinking I may send my FC Board out to Jeremy James and have a better/longer antenna installed and while he has it have him look at the MPU-6050 chip. The new antenna should give me up to 40% more range.

    Sent my flight control (FC) board out to Jeremy James at USdronerepair.com. I'm having him upgrade the receiver antenna and look the FC board over for any other issues that might exist (MPU-6050). I figured while it's winter and I'm not flying I would get this done. If I get into FPV flying the extra range will be good to have.

    Got my FC board back from Jeremy. It looks very good. Now I just need to connect it all back up.     Jeremy said that my board looked fine, better than most he has seen. No warping and no problems with the MPU-6050. He added heat sinks to the 54328 and the power management chips as he had seen these components get heat stressed and fail.

    I just picked up the 350 QX USB-Interface: Multi Rotor Programmer (BLH7840) from my LHS. I'll be able to plug this in when I reassemble the QX. I want to fly and test out everything before upgrading from FW V2.0 to V3.0. I may even put off the FW upgrade until Spring and see if HH puts out a newer version. Waiting for V3.01.