Champ S+ Went Inverted and Crashed Right After Takeoff

[K Teacher]

Hello all,

PROBLEM:
The first time I flew the Champ S+ was indoors, in an inflatable dome (not metallic structure). The plane took off from the ground, smoothly and in straight line. It reached an altitude of 2 ft. at approximately 10 yd. of distance. Suddenly, without any input from me, the plane quickly rolled to the right, went inverted and then crashed, nose first. The damage to the plane was considerable.

BACKGROUND:
I bought this RTF (ready-to-fly) Champ S+ second-hand, in a swap meet. The plane was in very good condition and came with all accessories.
Before inspection, I made sure that the transmitter and the plane had fully charged batteries. As part of the pre-flight, I mechanically checked the motor mount and control horns. They were solid and the linkage on the horns were as indicated in the instructions manual that came with the plane.
Did re-bind the transmitter to the plane, checked all control surfaces movement's, ensured that GPS was DISABLED, as per instructions manual directions (plane's system confirmed by waving the rudder four times). Also, put the transmitter Flight Mode Switch in Beginner mode (pos. 0).

NOTES:

1. To rule-out the Champ S+ transmitter malfunction, I bound it to a new Night Vapor plane, which has AS3X and SAFE and flew it. Everything worked as it should.
2. In the Champ S+, if the GPS board is DISCONNECTED from the receiver board, the receiver will NOT bind to the transmitter.
3. I also contacted Horizon Hobby Customer Support and the advisor that I spoke with, said that he couldn't offer any explanation on why this problem happened nor any suggestion or recommendation on how to prevent this from happening again.

After the crash, I read the whole "Instructions Manual" again, and confess I am a little confused…

QUESTIONS:

• As per the instructions manual, If the plane loses GPS signal, the system will indicate that condition by moving both ailerons' up.
  If the plane loses COMPASS calibration, the system will indicate that by moving left aileron down and right aileron up.
  The COMPASS is part of the GPS system. If I disabled the GPS, as per the Instructions Manual directions, shouldn't the COMPASS input be also disabled?
• SAFE was in Beginner Mode (pos. 0). Isn't SAFE pos. 0 supposed to limit the airplane pitch and roll?
• If there was a system issue, why it wasn't it indicated by the ailerons' movement during the receiver initialization?
• Could it be GPS board malfunction? How do I check it?

I am waiting to re-build the Champ S+, until I understand if the crash happened due to one the plane's control boards failure (main board or GPS board) OR if I missed something on the step during the plane's initialization.
I am curios; did anybody have a similar experience and how did you fix it?
Thanks for your time.

[xviper]

What your plane did after take-off, kinda tells me that the gyro response for aileron (and maybe elevator) was reversed. You say you checked that the sticks moved the control surfaces in the correct directions BUT, did you ever check that the gyro response direction was correct? IE, after you plugged the battery in, did you leave the plane in it's upright position and not touch it for several seconds? After it initialized, did you test the gyro response? IE, did you initialize the AS3X by blipping throttle to at least 1/3 throttle so that the control surfaces moved when you moved the plane? And when you moved the plane, did the control surface move in the proper direction to correct for the manual movement? Any plane that comes with a gyro must be checked in this manner before it flies.

[K Teacher]

Hello xviper,

Thanks for your quick response.

The plane took off from the ground, smoothly and in straight line. It reached an altitude of 2 ft. at approximately 10 yd. of distance, and then, without any input from me, the plane quickly rolled to the right, went inverted and crashed.

Before that, I powered up the transmitter (on beginner mode), installed a charged battery on the plane, put it on the floor and waited for the system to initialize. Right after connecting the plane's battery, it waved the rudder 4 times to indicate that the plane was in indoor flying mode, that is, GPS DISABLED.

After that, I moved the control sticks to check ailerons, elevator and rudder functionality; they worked as they should. Then I applied throttle to taxi and takeoff. If the control surfaces move in the right direction, then mechanically the SAFE system will respond in the right direction as well.

Just to double check, after the crash, I partially mended the plane and using this YouTube video as guide (Bench Testing the Eflite SAFE Rx), I bench checked the AS3X and it worked just as it was supposed to; no issues and no reversal.

[xviper]

Yes, I understood all that from your first post. I'm going to have to take your word for it when you said you checked that the gyro response was in the correct direction. If you based your test on that video, then all should be good. The only other thing that I can think of is perhaps the RX came loose. Other than that, I don't know what else could be wrong.

[K Teacher]

Hello xviper,
My understanding is that SAFE is designed to prevent the plane to pitch or roll more than 15 degrees.

According to the Champ S+ Instructions Manual, the only event that would cause the left aileron to go full down and the right aileron to full up (which would force the plane to roll right) is (as means of indication) loss of Compass calibration from the GPS board. I assumed that this only would happen during the plane’s power up initialization and not at any time. However, the Instructions Manual is not specific on that.

For this reason, I suspect that the issue with my plane was caused by GPS malfunction and/ or GPS software bug. Unfortunately, so far, I found absolutely NO information available on the Champ S+ GPS system.

Does anybody have any info on Eflite plane GPS system?
Thanks again.

[xviper]

Hello xviper,
My understanding is that SAFE is designed to prevent the plane to pitch or roll more than 15 degrees.

The degree of bank limit can be different for every plane that has SAFE. 15 degrees is pretty shallow, even for a trainer plane. It's usually 50 degrees. I still have no idea why your plane flipped upside down. I'll leave that to those more informed.

[K Teacher]

xviper,

Thanks for your comment. I think I saw 15 degrees somewhere and it stuck on my mind; perhaps this value is not accurate.

However, the point I was trying to make is -- if I checked the SAFE functionality according to the directions on the "Bench Testing the Eflite SAFE Rx" video AND it worked properly, THEN the safe should prevent the plane from rolling upside-down.

Because of the above, I am inferring that this issue was caused by the GPS board. Just FYI, in my conversation with Horizon Hobby Customer Support, the advisor confirmed that the COMPAS is on the GPS board and not on the ESC/ receiver board. But like I said before, there is absolutely NO information available on the Champ S+ GPS system.

I was hoping that someone here, had the opportunity to experiment with the Eflite GPS and could shed some light on my GPS concern.

[K Teacher]

Additional Info on CHAMP S+ GPS

To answer a previous question, I believe, because the Champ S+ was launched in 2016, its receiver + integrated ESC (HBZ5457) uses DSMX communication protocol with the transmitter.

I found this 2016 thread with some info on the Champ S+ that I think might be of interest:
Hobbyzone Champ S+ (Aug 25, 2016) -- https://www.hobbysquawk.com/forum/rc...byzone-champ-s.