Problems with FT Bushwacker

[sethonmeth]

I recently picked up an FT Bushwacker because it looked like a great plane in the videos and seems really well received all around. But my experience has been significantly less than spectacular.

I picked up my first one and put it together just like the one in the videos with similar parts to Power Pack C. It flew really amazingly, just like in the videos, and I was really happy with it until the fourth flight where it developed a problem where it would suddenly try to dive and spin. The problem happened extremely rapidly. I had one instance where the plane started to dive and I caught it. So I tried to line it up for a landing and it just spun into a death spin. I was full throttle and was definitely going in the right directions with my sticks but it did nothing and it crashed.

So I do some research online and deduce that the crash must have been caused by the rubber bands losing their elasticity in the cold weather, something which I did not know could happen. And also this is something I consider a massive oversight in design. Anyway, I fix my plane and put a piece of wood on the wing so I can put the rubber bands on tighter. I fly it again and it flies really great again but very quickly develops the same problem as the first one and I absolutely destroy this one. It seems like pulling the rubber bands tighter makes them lose elasticity faster and this time the rubber bands had noticeably lost their strength.

So I get another Bushwacker and I go all out and make wood pieces to attach the wing to the fuselage with carbon fiber rods, reinforced everywhere with carbon fiber rods, reinforced all control surfaces so there would be no flex or give in them, I pretty much cut no corners structurally. Also I put in a Power 15 motor, 45 amp esc, digital servos. Tied and glued carbon fiber to the control rods. Went to town and took every precaution so that I wouldn't have such a catastrophic failure on that level so early in the plane's life. Total weight was a little over 2lb.

It flew really amazingly until the third flight, where it had some sort of catastrophic failure mid flight and crashed in exactly the same way both previous ones did. The plane just started to spiral down and I could't roll back to flat or pull up or rudder out. I still have no idea what the problem was. It just started coming down and even though I'm 100% I was going the right way with the sticks it did nothing. And wind was extremely calm at around 5mph. Anyway the plane made 2 loops around so that was every direction in the wind checked off twice. It just stopped responding. I looked the plane over and all control horns and rods are still fine, all servos work fine, wing attachment apparatus still attached and working perfectly. I made sure to tape up my receiver wires and ran one up through the straw that comes in the kit at a 90 degree angle to one another (crash happened within 100ft of me anyway). Plane was squared up well and nothing was crooked. Battery had not slipped out of place. No problem with motor. Power pod did not fail. Battery still at 11.9v, had only discharged 500 of 2200mah in 2:30 where this plane can do 7 minute flights. I'm out of reasons as to why my plane could have failed.

I'm pretty exhausted with the whole experience. But it seems to me like with this plane it's just a matter of time before your plane develops this exact problem mid flight and is destroyed. To say I'm disappointed with my experience would be such a massive understatement. It just kills me because I really like the way this plane flies; it's exactly what I'm looking for. But it seems like 100% of these will end in this same way and in a similar amount of time. I'm interested to see how many other people had this same problem. It seems like it should be extremely common.

Maybe some of you on here can think of some reason as to why my plane would be flying amazingly one second and then in a death spiral the next. Because I don't know why I would fix this thing up if I can't figure the problem out. Was it ever the rubber bands losing their elasticity at all? The problem was identical this time to when I thought it was the rubber bands. I really was not amused any of the times that happened so far and am not looking for another such experience.

I don't want to talk trash on Flite Test. I like your guys' attitude. But %$^* me was this plane a nightmare. Have you guys looked at redesigning it? If I had known this was the case with this plane I would have just sought out to make my own design completely from scratch.


TL;DR Keep having the same fatal problem with Bushwackers. Cannot figure it out.

 

[Bricks]

Have you done range checks? You could have a receiver or radio issue. The plane itself is not the issue to many of them have been built and flown has to be something in the electronics.

 

[makattack]

Welcome to the FT forums, and sorry to hear you've had such a trial with your Bushwacker! Have you been using the same radio system (RX and TX) with each build? I wonder if you've put the same RX in all the rebuilds, that RX might be suspect? What are the specific models of those components? Do you also know the amperage output limits of the BEC on your ESC? If you're using that to power your servos, and you have 4 digital servos, another possibility is that you're experiencing a brownout situation where the servos draw too much current from your ESC's BEC. With digital micro servos, I sort of plan for 1A for each servo, so I would minimally want at least a 5A BEC for 4 servos and most likely want a bit more just to be safe.

Here's an example of a 45A ESC with a 5A BEC: https://hobbyking.com/en_us/aerostar-advance-45a-esc-w-5a-bec.html

Some info on servo loads:
http://homepages.paradise.net.nz/bhabbott/Servo.html

 

[sethonmeth]

Welcome to the FT forums, and sorry to hear you've had such a trial with your Bushwacker! Have you been using the same radio system (RX and TX) with each build? I wonder if you've put the same RX in all the rebuilds, that RX might be suspect? What are the specific models of those components? Do you also know the amperage output limits of the BEC on your ESC? If you're using that to power your servos, and you have 4 digital servos, another possibility is that you're experiencing a brownout situation where the servos draw too much current from your ESC's BEC. With digital micro servos, I sort of plan for 1A for each servo, so I would minimally want at least a 5A BEC for 4 servos and most likely want a bit more just to be safe.

Here's an example of a 45A ESC with a 5A BEC: https://hobbyking.com/en_us/aerostar-advance-45a-esc-w-5a-bec.html

My Esc has a 6amp SBEC.

Here is a link to where I bought it: http://www.headsuphobby.com/Sky-Power-45A-ESC-with-Switchmode-BEC_p_2212.html

I'm also running 2 analog servos for flaps.

I'll have to do some testing on this receiver to figure out if it's broken. But it didn't go through that much at all honestly. Even the worst crash did destroy my plane, but it was a pretty mild impact. And I checked all the controls and surfaces before and after the last crash and everything checked out and worked perfectly.

I ran tests on this last iteration where I did 3 full battery drains doing 1/2 to full throttle while constantly moving all control surfaces. Never had any noticeable droop even when holding very long at full throttle. Actually I would say the servos became more smooth and responsive after warming up. Power stayed consistent until over 1500mah had been dischaged at well under 11v every time. Made it past 5 minutes every time.

 

[sethonmeth]

Have you done range checks? You could have a receiver or radio issue. The plane itself is not the issue to many of them have been built and flown has to be something in the electronics.

I haven't done range checks. I didn't think reception was the issue because they all happened within 150ft of me. The furthest I flew out was maybe 250ft. It may have been reception or a problem with the receiver's hardware. But in all of the testing I've done the receiver has worked perfectly. It never exhibited this kind of behavior. And I think I've had it plugged up running tests on the ground far longer than the amount of time it's been in the air.

I'll do range checks and further testing on it and see what I can come up with. Right now I'm leaning towards the receiver being the most likely cause because it is a common element in all 3 crashes. But I haven't seen it act up at all otherwise.

Edit: Just ran a range check and it worked at over 100ft in range check mode. As far back as I could tell it was working, it was. Played around with the receiver some more. Can't find any issues whatsoever with it. I'll have to do some research and see if there is a diagnostic I can run on it or something.

 

[Brett_N]

It's either interference or Power issues.

And before this all happened, what type of flying were you doing? Just cruising around? Inverted? hardcore 3D? Take the prop off, power it up on the bench, and wiggle all of the wires at the battery, ESC and RX. Almost sounds like a cold-solder joint on the ESC BEC coming loose and causing the RX power to cut in and out.

 

[sethonmeth]

It's either interference or Power issues.

And before this all happened, what type of flying were you doing? Just cruising around? Inverted? hardcore 3D? Take the prop off, power it up on the bench, and wiggle all of the wires at the battery, ESC and RX. Almost sounds like a cold-solder joint on the ESC BEC coming loose and causing the RX power to cut in and out.

I got this plane as a park flyer and I'm not really interested in 3D. But I can fly inverted almost as well as I can right side up. I can do some 3D but I have problems with getting the rudder direction right with knife edges when things get hairy. But that's about the only thing holding me back from doing rolling harriers and the works with 3D. Never even did a loop with this plane. Was still just checking it out and doing very simple take offs and landings when it crashed. I literally never even pulled flaps up is how mild of flying I was doing.

One of the solders on the XT60 on the ESC was weak, well not extremely weak but definitely imperfect. It was still fully connected and didn't wiggle loose ever. I ran tests and bent it around until it snapped off while moving controls around and I had no problems with controls until it was completely detached.

Everything else on ESC is soldered well.

I won't have a soldering iron until Thursday so I can't reattach this properly right now. But this definitely seems like it could have been the culprit of at least my most recent crash. Even though it doesn't make that much sense I don't think I can rule this out as a possible cause until I've soldered it back up and tested it. This is some excellent sleuthing guys.

I never lost power to the propeller so it never cut out power completely. But maybe some funky stuff was happening with the current because of this bad solder.

The more and more I reflect on the crashes the more it seems like it must be some kind of power failure or BEC failure.

 

[Brett_N]

Hey at least the electrics is about 1000X less frustrating than the old gas / nitro stuff!!!

I've had a couple inexpensive (ok, cheap) ESC's crap out on me. One actually melted through the bottom of a plane on one flight :applause:

Oh - and also check the voltage on the BEC if you can. I had an ESC that was putting out something like 9V - servos don't like that too much.

 

[Tench745]

One point to note, your servos will draw more in flight that on the bench. In a bench test there are no loads on the control surfaces like there are in the air. When flying the air is pushing harder than you'd think on the control surfaces.
With your flaps full down, that's two servos drawing about the most they will. Add aileron and elevator inputs with flight loads, and your current draw can spike significantly.
With a bad solder connection and apparently quite cold weather your battery's ability to deliver necessary power suffers.

It's hard to get a good bench test because you'll never want your prop on with the motor running drawing full power. But grabbing a control surface or two to add some load will give you a better idea.

 

[sethonmeth]

One point to note, your servos will draw more in flight that on the bench. In a bench test there are no loads on the control surfaces like there are in the air. When flying the air is pushing harder than you'd think on the control surfaces.
With your flaps full down, that's two servos drawing about the most they will. Add aileron and elevator inputs with flight loads, and your current draw can spike significantly.
With a bad solder connection and apparently quite cold weather your battery's ability to deliver necessary power suffers.

It's hard to get a good bench test because you'll never want your prop on with the motor running drawing full power. But grabbing a control surface or two to add some load will give you a better idea.

I did check the surfaces like this during one of the tests. There was plenty of power there and no droop when all surfaces moved at once. I know it's not a good idea to run full throttle bench tests with your prop on, but I wanted to get a really good idea of how the whole system would handle full throttle for extended periods and be on top of my battery life.

I think I've got a good idea of what the possible causes are at this point. I've got a spare receiver and I'm going to resolder this ESC, rebuild my power pod, get a new motor for it because my motor got broken in the last crash, and fly this bad boy again. Plane is otherwise almost completely undamaged. So there's definitely that to be happy about. I'll try and report back with a video if I can actually get it flying without any failures.

 

[LongIslandNY]

Hey. I know this thread is pretty old, but did you ever find out what the issue was with your bushwacker?

 

[KarlBormanAZ]

I don’t mean to sound snarky, but I would say it has to be something with your RX/TX system. I have built 2 Bushwackers, one exactly to the build video and one beefed up one and never had any flight characteristics issues. To your point, initially all your planes flew great. If it was a design flaw of some sort, they would have exhibited the bad tipstall characteristics from the first.
I hope you have gotten to the bottom of the issue by now. I would definitely try another TX and RX in your next build and see what happens. Sounds like you are a solid builder and that it has got to be something in the electronics.
Hang in there. FT designs are pretty solid and tested by hundreds if not thousands of RC enthusiasts. Not all FT designs fly as well as others, but I’ve built and have hundreds of flight hours on many different designs and I’ve never experienced a fatal failure like you are describing that was based on anything other than component failure (servo, ESC) or pilot error. I’m not suggesting BTW that your particular issue was pilot error. It sounds more like component failure or partial/intermittent failure.