Champ S+ Went Inverted and Crashed Right After Takeoff

K Teacher

New member
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.
 

OlliePackman

Active member
Even though it won't bind with the GPS unplugged, you will probably be able to fly with it unplugged. Remember, you only need to bind the plane to the transmitter once and then you should just be able to turn the transmitter on and plug the battery in. If you cannot fly without GPS, then try binding with the GPS plugged in and then unplug it and fly. If you can't do anything without the GPS then... Well I have no idea. I would guess that this is probably the problem but you will struggle to to fix the GPS without just buying a new one. I had a similar issue with an as3x gyro system and sometimes the technology is just too advanced for basic hobbyists like me and you to understand how to fix.
However, in assuming you have ruled out basic issues such as trim, C.o.G etc.?
 

Bricks

Master member
Being you purchased it used nobody really knows what the last person changed or not changed on it. Just curious did you check the receiver orientation or even if it is the correct AS3X receiver for that plane. Did you bench test to see if the AS3X was moving the control surfaces in the right direction, did you reverse any servos in your radio, this is a very nasty no no as that needs to be changed in the stabilizing receivers....Just asking questions to try and help.
 

K Teacher

New member
Hello OlliePackman,

Thanks for your comments.

Yes, before I flew the plane, I checked the motor mount, the mechanical linkage and if the control surfaces were centered (transmitter out of SAFE and control sticks centered – except throttle). Also, the transmitter radio digital trims were all centered. After that, holding the plane, gave 100% throttle to check for motor/ propeller vibration. All was OK.

Before takeoff, checked the C.G. and checked all control surfaces movements and ensured that GPS was DISABLED (as per Instructions manual directions -- plane's system confirmed by waving the rudder four times). Also, switched the transmitter flight mode to Beginner mode (pos. 0).

With regards to binding & GPS -- the Spektrum/ Eflite Ultra Micro (UMX) receiver with integrated ESC and servos, unlike larger receivers, does NOT have a binding jumper. For this reason, the UMX system requires (even for systems that have already been bound), to re-establish the link between transmitter and receiver (aka initialization), every time the system is powered ON. A blinking micro-LED (on the receiver board) illumination indicates when the initialization is successfully completed.

The firmware code, in the Champ S+ receiver board, looks for the GPS board to either bind or initialize the transmitter-receiver system (even in indoor flying mode, that is, GPS has been DISABLED). I did try to bind my plane, disconnect the plane's battery and then the GPS connector. After installing the plane's battery back, the system did not complete the initialization.
So… NO, you cannot fly the Champ S+ without the GPS board connected to the receiver board.

- - - - - - - - - -

Hello Bricks,

Thanks for your comments.

You are right, this being a second-hand plane, you never know what was done to it by the previous owner. However, looking at its guts after the crash, I could tell by the way that the receiver and GPS boards were glued to the fuselage that they were factory installed.

This is an RTF model and it comes with a simple radio transmitter, the same used on the Eflite Sport Cub S; it cannot do servo reversing, so this is out of the way. Besides, to rule out transmitter malfunction, after the crash, I bound the transmitter to another Eflite plane with SAFE and flew it; the transmitter worked fine.

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.

I still suspect that the issue with my plane was caused by GPS malfunction and/ or GPS software bug. Unfortunately, there is absolutely NO information available on the Champ S+ neither on its GPS system.

I guess the only way to verify that, is to replace the GPS board for a new one.
 

LitterBug

Techno Nut
Moderator
FYI, we have had fly-ins at inflatable domes. Many of them DO have a foil lining which can cause havok with radio signals. Were there any other pilots flying at that time? was it bound in DSMX or DSM2? I have seen really bad problems at indoor flys when using the older DSM2 protocol.
 

K Teacher

New member
Hi bisco,

When the plane crashed, I ran to it and disconnected the plane's battery. Later, inspecting the plane, I saw that the left aileron was locked full down and the right aileron full up, which explains the plane's roll to the right. At that time, I was commanding only a little up elevator for takeoff; no aileron input, so the plane did roll on its own. The strangest thing is, with SAFE ON, the plane should be unable to roll enough to go inverted.

To answer your question – if my understanding is correct, in order for the plane to stall one wing only, it is necessary to give a lot of up elevator AND at the same time try to make a turn.
 

K Teacher

New member
Hi LitterBug,

There were other planes flying at the dome simultaneously. I flew with them before and never had any issues. Right after the crash, I bound the Champ S+ transmitter radio to another Eflite plane I brought with me and flew it, to rule out any transmitter radio issues. The other plane is also equipped with SAFE and worked as it should, no problems.
 

LitterBug

Techno Nut
Moderator
Hi LitterBug,

There were other planes flying at the dome simultaneously. I flew with them before and never had any issues. Right after the crash, I bound the Champ S+ transmitter radio to another Eflite plane I brought with me and flew it, to rule out any transmitter radio issues. The other plane is also equipped with SAFE and worked as it should, no problems.
What protocol did it show when it binded up to the TX. Is plausible that it was in DSM2 and your other was in DSMX.
 

K Teacher

New member
Hi LitterBug,

I was in a hurry when I read your first post. Thanks for the info about the inflatable domes; I did not know about the foil lining. Thinking of it, it does make sense for them to have a foil lining to discharge static electricity from the structure.

Also, good information about interference with DSM2 receiver technology.

The Champ S+ RTF comes with the same transmitter used on the Sport Cub S and it will bind to either DSM2 and DSMX receivers. From the Eflite and Spektrum sites, the Champ S+ uses the HBZ5457 receiver board, but there is no mention about DSM2 or DSMX.

At this time I can't tell if the Champ S+ HBZ5457 receiver uses DSM2 or DSMX technology. Is there a way to know which one it uses?
 

LitterBug

Techno Nut
Moderator
Hi LitterBug,

I was in a hurry when I read your first post. Thanks for the info about the inflatable domes; I did not know about the foil lining. Thinking of it, it does make sense for them to have a foil lining to discharge static electricity from the structure.

Also, good information about interference with DSM2 receiver technology.

The Champ S+ RTF comes with the same transmitter used on the Sport Cub S and it will bind to either DSM2 and DSMX receivers. From the Eflite and Spektrum sites, the Champ S+ uses the HBZ5457 receiver board, but there is no mention about DSM2 or DSMX.

At this time I can't tell if the Champ S+ HBZ5457 receiver uses DSM2 or DSMX technology. Is there a way to know which one it uses?

That depends on your transmitter. The champ supports DSMX, but is backward compatible with DSM2. The DX6 and DX8s that I've had will tell you at bind time what protocol they bound up in. I am very hesitant to bind any auto bind plane up at an indoor fly because they may bind up to the first signal they see. I have seen people put the battery in without turning their radio on first, it went in to bind mode, and someone else just happened to be binding at the same time. Poof, someone else is controlling their model.

LB
 

TheFlyingBrit

Legendary member
That's why I don't use flight controllers, if any of my planes crash its pilot error plane and simple :unsure:;)(y)
KISS - Keep It Simple Stupid.
 

TheFlyingBrit

Legendary member
Not if you have good quality well maintained equipment and do all your pre checks before flight ie range testing.
I have personally only lost a signal once and that was with an inferior AR6210 Spektrum fake receiver. It wont happen again, I only buy genuine RC gear from legitimate dealers these days and always do a range test before I fly. Plus I always use telemetry where possible, to give me a RSSI value during a flight.
 
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K Teacher

New member
Thank you all for your input.

I flew several times in this indoor space before with my Horizon Sport Cube S (SAFE ON) and never had any issues.
I don’t think 100 ft. x 70 ft. is big enough for you to fly out of range...

Now, it is possible the Champ S+ GPS was defective or suffered some kind of interference like Bisco described before…
 

K Teacher

New member
Hello [U]BayDesigns[/U],

The first flight attempt was indoors, at a inflatable industrial dome.

I turned the radio ON, plug a fully charged battery to the plane and wait a few moments for the plane receiver to initialize. The rudder wagged four times to indicate the GPS was disabled.

Moved the radio sticks to make sure that the control surfaces were working properly, and then I checked the "Flight Mode Switch" to make it was in "Beginner Mode" (pos. 0 – full down).

After that, I started applying throttle until the plane begun to roll, and then, applied full throttle and at the same time, gently pulled on the elevator stick a little and held it. 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.

Then suddenly, without any input from me, the plane quickly rolled to the right, went inverted and then crashed, nose first.

My understanding is that, in order for the plane to stall one wing only, it is necessary to give a lot of up elevator AND at the same time do a hard turn.

The plane was taking-off, so my estimate, based on distance and time, the flight speed was approx. 8 mph when the plane rolled and crashed.
 

Piotrsko

Master member
Ok analyzing your replies to what the system does and what you found, it appears that it lost the compass function and did the right roll thing to inverted ( which seems stupid as all get out) . The system is probably engineered such that the stabilizer and gps functions will override the beginner settings that limit travel and probably everything else. Except for being unsure how sensitive the compass function is, the metal in the building shouldn't affect reception at all since it is longer than a wavelength, but it will shield the earths magnetic field somewhat. A cheap handheld compass would test that.

So two possible things: signal interference..... unlikely since you found it in the lost compass condition, or an odd anomaly coupled to the system design resulting in a death roll. You might replicate the process somewhat by hand walking it around the dome. A range test is useless in this case.
 
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