Help! Who can solve the mystery of this Carbon Cub S+ crash?

[Douglas]

Man, I am so bummed. My Carbon Cub S+ is the second plane I have owned. My first four or five flights with this plane were great. But on my penultimate flight, it was cruising around in beginner mode and suddenly it started losing altitude for no apparent reason. I was giving it full up elevator and full throttle, but it continued on it's slow descent into a tree. Two days later, the wind blew it down from the tree. When I did my repairs the right aileron did not function so I ordered a new aileron. When I removed the old aileron, I noticed that it was warped as if it overheated or something.

So the new parts arrived today and I installed everything. I usually don't use the GPS feature, but for whatever reason I left the SAFE and GPS features on for this last flight. I tested all all servos and everything was working properly. Neutral on the transmitter sticks returned everything to neutral position. Elevator, rudder, ailerons were all working properly before take off. CG was fine.

The grass was long so I had a friend help me with a hand launch. I powered up 100% and he gave it a gentle toss. Immediately the plane started to dive and I gave it full up elevator with 100% throttle. It started to climb gently, but I said "oh man this just wants to dive; it's going to crash." Holding full up elevator and 100% throttle, I'd say it climbed to about 100 feet or so. I told my friend I just want to get the plane down in one piece, but the moment I let off the elevator just a smidgen (I was still probably at 75% up elevator), it just nose dived and the plane is ruined.

While this was much more dramatic than the crash I described in the first paragraph, essentially the same thing happened a second time. Below are pictures of the plane looking just as it did when I picked it up at the crash site. As you can see the elevators are in the full down position (admittedly, the momentum of the crash could have caused that, but the plane did nose dive so it's likely that that was the actual position of the elevator when it went into that dive...but again it was nearly at full elevator on the transmitter when it when into that dive).

I don't know the names of any of the electronic parts on this plane, but the second picture (noseshot.png) is taken from the front of the plane and I notice there is a black wire that appears to have been dislodged from its slot in whatever the hell it was supposed to be plugged into. Did that happen at the time of the crash, or could the dislodged wire have had something to do with the crash? I don't know. The shot titled blackwire, is the other end of that blackwire. What was it supposed to be plugged into? Could that have caused this crash?

This is a complete mystery to me. I dumped about $1,000 into my first foray into RC planes, and while I would like to continue in this sport, I'm not keen on investing in all the necessary repairs to this plane (if it even can be repaired) only to have it happen again on my next flight. I really want to know why this plane crashed, and I would be grateful for any thoughts.

I am happy to send along additional pictures as requested.

 

[OliverW]

Man, I am so bummed. My Carbon Cub S+ is the second plane I have owned. My first four or five flights with this plane were great. But on my penultimate flight, it was cruising around in beginner mode and suddenly it started losing altitude for no apparent reason. I was giving it full up elevator and full throttle, but it continued on it's slow descent into a tree. Two days later, the wind blew it down from the tree. When I did my repairs the right aileron did not function so I ordered a new aileron. When I removed the old aileron, I noticed that it was warped as if it overheated or something.

So the new parts arrived today and I installed everything. I usually don't use the GPS feature, but for whatever reason I left the SAFE and GPS features on for this last flight. I tested all all servos and everything was working properly. Neutral on the transmitter sticks returned everything to neutral position. Elevator, rudder, ailerons were all working properly before take off. CG was fine.

The grass was long so I had a friend help me with a hand launch. I powered up 100% and he gave it a gentle toss. Immediately the plane started to dive and I gave it full up elevator with 100% throttle. It started to climb gently, but I said "oh man this just wants to dive; it's going to crash." Holding full up elevator and 100% throttle, I'd say it climbed to about 100 feet or so. I told my friend I just want to get the plane down in one piece, but the moment I let off the elevator just a smidgen (I was still probably at 75% up elevator), it just nose dived and the plane is ruined.

While this was much more dramatic than the crash I described in the first paragraph, essentially the same thing happened a second time. Below are pictures of the plane looking just as it did when I picked it up at the crash site. As you can see the elevators are in the full down position (admittedly, the momentum of the crash could have caused that, but the plane did nose dive so it's likely that that was the actual position of the elevator when it went into that dive...but again it was nearly at full elevator on the transmitter when it when into that dive).

I don't know the names of any of the electronic parts on this plane, but the second picture (noseshot.png) is taken from the front of the plane and I notice there is a black wire that appears to have been dislodged from its slot in whatever the hell it was supposed to be plugged into. Did that happen at the time of the crash, or could the dislodged wire have had something to do with the crash? I don't know. The shot titled blackwire, is the other end of that blackwire. What was it supposed to be plugged into? Could that have caused this crash?

This is a complete mystery to me. I dumped about $1,000 into my first foray into RC planes, and while I would like to continue in this sport, I'm not keen on investing in all the necessary repairs to this plane (if it even can be repaired) only to have it happen again on my next flight. I really want to know why this plane crashed, and I would be grateful for any thoughts.

I am happy to send along additional pictures as requested.

Don't panic! This can easily be fixed. You get water to boil, and take it off heat for a minute or two until the boiling stops. You then put the water over the areas with wrinkles in the foam to make it smooth and wrinkle-less. And you use hot glue to glue it back together. And if you dont want to repair it, you can take the internals out and use them in a flite test plane which you can scratch build. Then if you crash your only out a few dollars

 

[Douglas]

Don't panic! This can easily be fixed. You get water to boil, and take it off heat for a minute or two until the boiling stops. You then put the water over the areas with wrinkles in the foam to make it smooth and wrinkle-less. And you use hot glue to glue it back together. And if you dont want to repair it, you can take the internals out and use them in a flite test plane which you can scratch build. Then if you crash your only out a few dollars

Okay, but I really want to know why this crashed. Whether I spend 3 days of spare time building a flitetest plane or $200 and two days rebuilding the mess I have, I don't want to go through the very same thing on the next flight.

 

["Corpse"]

Okay, but I really want to know why this crashed. Whether I spend 3 days of spare time building a flitetest plane or $200 and two days rebuilding the mess I have, I don't want to go through the very same thing on the next flight.

I flew a friends beginner safe plane, and it was doing some really funky things. It wouldn't let me push the nose down at all, and kept stalling. Maybe that's what's happening with yours. As soon as I took off SAFE, it flew great! I agree with @SquirrelTail , try scratch building! If you build every part of your plane you can easily repair the whole thing!

 

[OliverW]

Okay, but I really want to know why this crashed. Whether I spend 3 days of spare time building a flitetest plane or $200 and two days rebuilding the mess I have, I don't want to go through the very same thing on the next flight.

Definetly disable the GPS. My friend Carl had his fly away due to the GPS freaking out. The safe also may he having some issues

 

[Hondo76251]

Hard to say exactly, but ive had similar glitches with many types of stabilizers, including SAFE. I think Its basically confused about the attitude that the plane should be flying at. This can be for many reasons, hard to determine exaclty without having seen the plane and witnessing the flight... id repair the plane if i were you. It may sound suprising if you havent seen it done but a little gorilla glue and patience can bring some pretty spectacular wrecks back to life.

Id also suggest getting something simple to fly, either a Flite Test build or cheap foamie and work on the muscle memory of flying itself without the SAFE. Once you have that skill all the stabilizers are is icing on the cake. Ive found that a lot of people that start with stabilization have a hard time getting good flying skills.

Fly first, stabilize later imho...

 

[varg]

The first crash sounds like low voltage protection cutoff. I suggest flying with one of those battery screamers that plugs into the balance lead and beeps loudly when cell voltage gets below a set point, when I was new I set it to 3.7V so that when it started beeping at me during normal flight I had plenty of battery left to make several missed approaches. The second crash; I don't have any firsthand experience setting up SAFE planes, I never used the feature in my Timber X before I replaced the receiver with a FRSky unit, but don't they want to be placed in a level orientation after the battery is plugged in to initialize properly? It seems to me that if it was allowed to initialize in a nose down position, and left in self leveling mode, it could "think" it is in a steep climb when it is actually flying level. I could be way off base, level orientation might be set during initial programming like when you set up a quadcopter flight controller. I think you would have detected that before taxiing out because the elevator would have been deflected down when the controls were centered. Did the elevator move throughout its full range and center properly before flying? The connector with the black wires was probably dislodged in the crash and I believe is of no consequence to you, I read that it was a connector for programming the flight controller in situ.

SAFE with GPS is a good tool for beginners but I have seen two crashes caused by misuse of planes equipped with it. Most recently a plane like yours flew into some trees some 125yds away from the flight line on GPS hold or return mode because of misapplication of the home position. Luckily a storm blew it out of the very tall pine tree that day for the owner with minimal damage because it was too high for stick and rope throwing to work. Previously one was unable to autoland due to high winds and crashed itself.

Remember to always check your C.R.A.P.
Control surfaces - directions and neutral positions
Rips and tears - especially at control surface hinges
Angles - tail and wings for twist due to being installed incorrectly or damaged
Power system - motor condition and battery voltage

 

[PsyBorg]

Im with Varg on this one. First time sounded just like low voltage cutoff.

I also think he is on to something about the board initializing in a not level state. Some of the Flight controllers for quads will lose orientation as to what level is after hard crashes and have to physically be reset thru the computer and not just set level when plugging in. I noticed this when trying to use auto level when flying line of sight and getting too far away from myself. When I turn on auto level to reestablish orientation the quad would suddenly drop a corner as soon as I enabled the auto level but would go back under control as soon as it was shut off.

 

[Douglas]

Re: low power was the reason for the first crash--and I agree that's what it sounds like from the way I described it. I had just unplugged the battery from charging from a steady green light and this was only about 1-2 minutes into my flight.

Maybe I don't understand when SAFE kicks in. I thought it kicked in when the plane was too far away or when I press the button that sends the plane into a holding pattern, or if I'm doing an auto-landing. But this plane took a dive immediately upon hand launch when I was at full power. I gave it full up elevator and held full up elevator just to make it slowly ascend to about 100 ft. And as I said, the moment I let off full up elevator even a little bit it went into a straight nosedive.

Clearly, the elevator or something else was doing everything it could to push the nose down, while I was doing the opposite. And since I had a few moments of success fighting what the plane was trying to do, we know I didn't have the controls reversed or anything. So I guess the question is, if the plane was fighting me this badly, could the culprit have been anything other than SAFE? I checked CG and I know that was okay. But having said this, what the hell is it in SAFE that could have even been doing something right after hand launch??

I know the CRAP acronym and I checked it. I know for a fact that the rudder and elevator and ailerons were in neutral position at takeoff because I was extra worried about having a crash right away out of the gates.

 

[varg]

Is it possible the flight controller or servo was knocked loose during the previous crash?

SAFE has several modes; angle limit/autolevel, and the GPS modes. Which it was in at the time is not something any of us will be able to tell you unfortunately. Auto leveling/angle limit could fight you if the plane thinks it is not level when it is, i.e. level position not set correctly or flight controller knocked loose.

 

[Douglas]

Is it possible the flight controller or servo was knocked loose during the previous crash?

SAFE has several modes; angle limit/autolevel, and the GPS modes. Which it was in at the time is not something any of us will be able to tell you unfortunately. Auto leveling/angle limit could fight you if the plane thinks it is not level when it is, i.e. level position not set correctly or flight controller knocked loose.

The picture titled "noseshot" shows a disconnected wire. I don't know what a flight controller is, or what that empty slot in that photo is showing us. Could that be the flight controller? Yes, something could have been disconnected either in the first crash or before the first crash.

 

[varg]

Yeah the main unit that all the wires plug into in this plane is a flight controller, the receiver is the box with the 3 wires going to it and two antennas sticking out of it, then there's a GPS unit which is a little bigger and has 6 wires going to it. If the flight controller is not solidly attached to the fuselage it can cause all kinds of havoc since it needs to know the precise orientation of the airplane.
https://www.rccanada.ca/rccforum/attachment.php?attachmentid=1575124&d=1537312406

 

[Douglas]

Yeah the main unit that all the wires plug into in this plane is a flight controller, the receiver is the box with the 3 wires going to it and two antennas sticking out of it, then there's a GPS unit which is a little bigger and has 6 wires going to it. If the flight controller is not solidly attached to the fuselage it can cause all kinds of havoc since it needs to know the precise orientation of the airplane.
https://www.rccanada.ca/rccforum/attachment.php?attachmentid=1575124&d=1537312406

What is that braid of black wire coming out of the controller? When I picked up the pieces of my plane, neither end of that wire was connected to anything, although it could have been yanked out in the crash.

 

[varg]

As linked in a previous reply, it seems to be a programming port.

 

[Douglas]

As linked in a previous reply, it seems to be a programming port.

Ah, thank you. I missed that the first time around. Well, I haven't arrived at any conclusions as to what caused this crash, but I'm learning quite a bit here.

I tell you though, the more I read, the more I'm inclined to think that I should avoid SAFE until I'm a good enough pilot that I know when it is causing problems. I think the pilot of all the RC Saylors videos is the model. He's good but relatively new to the hobby, and employs SAFE not as an emergency feature but as a support in certain maneuvers. SAFE is a tool for the intermediate/advance pilot. It gets beginners into trouble (although I used it to my benefit on my first ever flight), and it is probably of little or no interest to the advanced or expert pilot.