What went wrong?

[Cache Flyer]

Hello, new member here. Today was both confusing and unfortunate. I just finished putting together my E-flite Twin Otter BNF and took it on its maiden flight. After a satisfactory check of the flight controls and SAFE mode, I took off without issue. During the first two minutes of flight the plane would roll wings level when I let go of the stick but it didn't not want to hold altitude very well, so I kept having to apply elevator input to keep it going. It just didn't look right for being in safe mode. Before I could bring it back to land it took a sharp nose dive that I had no control over. No amount of elevator or throttle input changed that flight path. Sadly it crashed nose first resulting in a nice gouge out of side of the nose which appears to only be cosmetic, another part of fuselage has a crack all the way through the foam and about half way down the fuselage from top to bottom. The worst damage though, was to the wings. The rear part of the center, that holds the mounting thumb screw completely separated, and the left wing also completely separated, only to be held on by servo wires. The right engine nacelle detached from the wing in two pieces as well.

My biggest questions are, what are your ideas on how this happened, and is it worth repairing or should I get new parts?

I am waiting to hear back from Horizon Hobby on their thoughts and what if anything they can do for me. I am a fairly new rc pilot, this is my second plane, the first being the Aeroscout. I thought I had a pretty good idea what I was doing at the time. I would be happy to provide more details about the incident or provide pictures if it will help. Any ideas or comments are appreciated. Thank you!

 

[BlockerAviation]

Hello, new member here. Today was both confusing and unfortunate. I just finished putting together my E-flite Twin Otter BNF and took it on its maiden flight. After a satisfactory check of the flight controls and SAFE mode, I took off without issue. During the first two minutes of flight the plane would roll wings level when I let go of the stick but it didn't not want to hold altitude very well, so I kept having to apply elevator input to keep it going. It just didn't look right for being in safe mode. Before I could bring it back to land it took a sharp nose dive that I had no control over. No amount of elevator or throttle input changed that flight path. Sadly it crashed nose first resulting in a nice gouge out of side of the nose which appears to only be cosmetic, another part of fuselage has a crack all the way through the foam and about half way down the fuselage from top to bottom. The worst damage though, was to the wings. The rear part of the center, that holds the mounting thumb screw completely separated, and the left wing also completely separated, only to be held on by servo wires. The right engine nacelle detached from the wing in two pieces as well.

My biggest questions are, what are your ideas on how this happened, and is it worth repairing or should I get new parts?

I am waiting to hear back from Horizon Hobby on their thoughts and what if anything they can do for me. I am a fairly new rc pilot, this is my second plane, the first being the Aeroscout. I thought I had a pretty good idea what I was doing at the time. I would be happy to provide more details about the incident or provide pictures if it will help. Any ideas or comments are appreciated. Thank you!

Sorry this happened, the otter is such a nice plane. It sounds like it's defective airplane, but I'm not sure. I believe that horizon has fairly robust fail safe so I don't think it would have been a signal loss. @sprzout , @The Hangar what do you guys think? Anyways, Keep us posted on what horizon says and I hope that your future flight end with the airplane in one piece!

 

[BlockerAviation]

Sorry this happened, the otter is such a nice plane. It sounds like it's defective airplane, but I'm not sure. I believe that horizon has fairly robust fail safe so I don't think it would have been a signal loss. @sprzout , @The Hangar what do you guys think? Anyways, Keep us posted on what horizon says and I hope that your future flight end with the airplane in one piece!

Ohh and it's completely worth repairing! I've repaired a few airplanes that had been written off by other club members and have had a lot of fun doing it. It sounds like your repair will be fairly straightforward, best of luck to ya!

 

[Cache Flyer]

Sorry this happened, the otter is such a nice plane. It sounds like it's defective airplane, but I'm not sure. I believe that horizon has fairly robust fail safe so I don't think it would have been a signal loss. @sprzout , @The Hangar what do you guys think? Anyways, Keep us posted on what horizon says and I hope that your future flight end with the airplane in one piece!

My thoughts were signal loss, signal interference from near by drones, or possibly a CG issue.
The fact that it didn't want to hold altitude in safe mode, along with the nose dive makes me think CG, which is the only thing I did not check during preflight. The manual does not give a clear enough way to check CG like the Aeroscout did. But it was still able to fly in safe mode with additional elevator correction.
I am also leaning towards signal loss and or interference because there was no response to any control inputs during the nose dive. There were a few homemade drones flying nearby at the time of the crash as well. my plane was maybe around 50 feet away from me at the time so signal issues shouldn't have been a problem, but I am no radio expert so I cant be sure.
It is pretty upsetting for a maiden flight but after investing this much money into it, I am determined to see it fly again, one way or another.
Attached is a picture of the aftermath. I was able to get all the broken pieces to fit back together so I do think repair could be an option if HH cant do anything.

 

[BlockerAviation]

My thoughts were signal loss, signal interference from near by drones, or possibly a CG issue.
The fact that it didn't want to hold altitude in safe mode, along with the nose dive makes me think CG, which is the only thing I did not check during preflight. The manual does not give a clear enough way to check CG like the Aeroscout did. But it was still able to fly in safe mode with additional elevator correction.
I am also leaning towards signal loss and or interference because there was no response to any control inputs during the nose dive. There were a few homemade drones flying nearby at the time of the crash as well. my plane was maybe around 50 feet away from me at the time so signal issues shouldn't have been a problem, but I am no radio expert so I cant be sure.
It is pretty upsetting for a maiden flight but after investing this much money into it, I am determined to see it fly again, one way or another.
Attached is a picture of the aftermath. I was able to get all the broken pieces to fit back together so I do think repair could be an option if HH cant do anything. View attachment 197649

With the 2.4 technology on spektrum radios interference has pretty much become a thing of the past. I'm guessing the problem wasn't cg either if you're using the recommended battery. From the sound of it, it seems either like you're rx is defective or you have a bad servo. Either way I'd wait for horizon to respond before buying any replacement parts because it seems to be a manufacturing defect. It definitely looks repairable though!

 

[Bifi.baarlo]

You said that the plane didn't keep altitute without applying elevator and before landing it made a nosedive, I think you made it to slow and the flight controller was working hard to keep it flying, but when you slow down a little more before landing, the flight controller gives up, that is the danger of flying with flight controller, you don't feel how the plane normaly behaves when flying, I recommend to learn without safe.

 

[Tench745]

Agreed that interference is unlikely. Did the motor RPM drop out at all? If it did that may show either a loss of power in the model or a loss of signal between TX and RX. If the fail-safe is set correctly, when you lose signal all controls should go to neutral and the motors cut out. If RPM didn't change that probably means it was something physical; either a mechanical failure or pilot error. Check to see if the Elevator servo is still connected.
What I suspect is basically what @Bifi.baarlo i just said; the flight controller was fighting something mis-trimmed in the model and when you slowed down enough the plane stalled. When the plane stalls and you see the plane drop suddenly your first impulse is to pull up, which only makes things worse. Aileron control is usually pretty limited in a stall too.

 

[sprzout]

Highly unlikely it was a signal loss. With Spektrum, *IF* you get a signal loss (and you haven’t programmed failsafe to switch the attitude to level flight) the plane will continue in in whatever attitude it was flying previously. So, if it was flying straight & level, it would continue. In a turn? Same thing. To just nose over says there was either a problem with the battery shifting forward suddenly (VERY unlikely unless you were in a dive immediately prior to the crash) or your flight controller had an issue.

Now, first things first, with regards to AS3X and SAFE - did you let the plane level itself before takeoff? This can take up to a minute after it connects with the transmitter - my UMX Timber takes time to initialize, and the way I can tell it’s done is that the flaps will go to full down elevator (I always switch them to full down so I can tell when the plane is ready). I realize the Twin Otter may not have that, so the next best thing is to pick up the plane and twist it a bit to see if the leveling kicks in. You’ll hear the servos trying to correct and keep it level of SAFE is on.

If that wasn’t set before takeoff, the plane could have been trying to right itself back to what it thought was level flight - which might have been at a nose down attitude when you were carrying it out to the runway. This is kinda one of those reasons I don’t like flight controllers; if it isn’t level, it has the potential to kick in and over correct, regardless of whether it’s a Horizon Hobby plane or the FT Aura or any other gyro system. I don’t hate the idea of them, as they have their place, but it’s something that can end up being a problem.

 

[Merv]

.... I am also leaning towards signal loss and or interference because there was no response to any control inputs during the nose dive....

I agree that interference form the drones is not the issue. BUT I would not dismiss the loss of signal theory

Did you do a preflight range check? All brands of Rx are subject to damage or malfunction. I have had new Rx's that were just bad. They will work on the bench but get about 50 feet away and you have nothing.

It's always a good practice to do a range check on a new setup or after a crash. Antennas are easily damaged in a crash.

 

[Bricks]

Was not there so have no idea of what was wrong, it could be a bad bind. NEVER bind a receiver with the transmitter right nest to the receiver at least 6 feet away or what I do is put my back to the model and hold my transmitter in front of me. What can happen when the transmitter is too close the receiver picks up multiple signals aka reflections and the receiver will bind but not a strong bind locked into a specific signal..