Crash Investigation help request
09-10-2019, 06:24 AM
#1
Crash Investigation help request
I have a new albeit wrinkled Tower Hobbies Hellcat. It comes as a PNP and I added a Lemon plus stabilizer.
Two other mods I thought were minor. I replaced the tiger connector with a XT60 and added more neodymium magnetsto hold the front cowl on.
The first flight started nice, needed an elevator trim adjustment but was flyable. Flew two circuits and a mock landing approach. Flying to start my downwind leg I was level and in a shallow climb and she throttled back on her own and I lost control of it.....gliding to a uncontrolled stall at the trees. Broken prop and some mild rash.
My lemon antennas didn’t stay apart and laid straight aft along the aileron wires. I figured maybe they got masked and lost signal. New MAS prop, taped the antennas in separate places, rearranged the aileron wires away from them.
Tested ok on the ground with a range check. Took off after rechecking control surfaces. Long takeoff roll on purpose, pulled right upon command. Got about 25feet up and powered fully in a steep dive no apparent response.
At this point all i can hypothesize is a bad receiver, a bad solder joint on the ESC or the extra magnets in the cowl are messing something up.
Two other mods I thought were minor. I replaced the tiger connector with a XT60 and added more neodymium magnetsto hold the front cowl on.
The first flight started nice, needed an elevator trim adjustment but was flyable. Flew two circuits and a mock landing approach. Flying to start my downwind leg I was level and in a shallow climb and she throttled back on her own and I lost control of it.....gliding to a uncontrolled stall at the trees. Broken prop and some mild rash.
My lemon antennas didn’t stay apart and laid straight aft along the aileron wires. I figured maybe they got masked and lost signal. New MAS prop, taped the antennas in separate places, rearranged the aileron wires away from them.
Tested ok on the ground with a range check. Took off after rechecking control surfaces. Long takeoff roll on purpose, pulled right upon command. Got about 25feet up and powered fully in a steep dive no apparent response.
At this point all i can hypothesize is a bad receiver, a bad solder joint on the ESC or the extra magnets in the cowl are messing something up.
Last edited by SteelonSteel; 09-10-2019 at 06:41 AM.
09-10-2019, 01:47 PM
#2
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I would go over the stabilizer setup, and turn it off until you are a few mistakes high.
Obviously check and adjust balance and servo throws.
I would Imagine the weight difference shouldn't put you outside of a wing loading that would prevent flight but consider doing a few glide tests over a soft surface.
I don't think the connector swap would be an issue assuming the job was done correctly.
You can open up the reciever and look for burnt components, cracked/melted/just not right traces and solder joints.
Similarly so with other electrical components such as speed control, the stabilizer, servos etc.
Lastly, if you are using exceptionally underpowered servos that stall at the control surface deflections you are asking them to perform...that can be an issue that is outside my ability to explain, I use an online calculator to see if my servos have enough torque to do the job I'm asking of them.
Maurice Pudlo
Obviously check and adjust balance and servo throws.
I would Imagine the weight difference shouldn't put you outside of a wing loading that would prevent flight but consider doing a few glide tests over a soft surface.
I don't think the connector swap would be an issue assuming the job was done correctly.
You can open up the reciever and look for burnt components, cracked/melted/just not right traces and solder joints.
Similarly so with other electrical components such as speed control, the stabilizer, servos etc.
Lastly, if you are using exceptionally underpowered servos that stall at the control surface deflections you are asking them to perform...that can be an issue that is outside my ability to explain, I use an online calculator to see if my servos have enough torque to do the job I'm asking of them.
Maurice Pudlo
09-10-2019, 04:55 PM
#3
Thank you for putting your thoughts to it.
I wasn’t thinking the weight of the magnets was an issue, I still had to add stick on lead wheel weights to balance on the correct CG. I was thinking those super strong magnets might affect the electronics, they are still 5 inches from the receiver but only a couple from the ESC.
i am a new rc flyer, so I don’t know what I don’t know.
ETA I tugged on the solder wires, they seemed sound. I did redo it as I didn’t like the first connection as my solder in the connector got a bit cold and it stuck early not fully inserted. That was before any flight though.
Last edited by SteelonSteel; 09-10-2019 at 04:59 PM.
09-14-2019, 06:33 AM
#4
Moderator
I'd go with it being a bad receiver or faulty transmitter. Lemon stuff does work, but there is no quality control. You are the final inspector, so to speak. It really should be done with every receiver, but particular with cheap ones- an extended range test with motor/engine vibration and at all possible angles. This is where telemetry radios have such an advantage, because you can not only see if it works, but can count glitches and maybe even know the actual signal strength.
10-04-2019, 11:17 AM
#5
Was chatting on another forum with a long Lemon thread. Reading the back pages I read on a guy’s problem;
ESC is 30 amps, 5v, 2amp. The two amp output is marginally they say. Get a servo hung up or working many servos while at full throttle and you stand a chance of undersupplying the receiver. Might be that.
ESC is 30 amps, 5v, 2amp. The two amp output is marginally they say. Get a servo hung up or working many servos while at full throttle and you stand a chance of undersupplying the receiver. Might be that.
10-04-2019, 02:40 PM
#6
Moderator
I'd be surprised if that was the cause. Do Lemon receivers even have the low voltage cutoff problem that Spektrum has steadfastly refused to fix for over a decade? Even if they do though, pulling 2 amps would be an accomplishment on a plane like this. Those servos just aren't that hungry.
10-14-2019, 10:38 AM
#7
I don’t have the experience to refute the claim.
I did however ever pick up a basic 6 channel receiver from hobby king. I am going to try that first seeing as my replacement bec didn’t have the 3.5 mm connectors installed. Another thing to order or see if the hobby store has them.
I might burn burn a whole battery on the stand at the club to see if there are any issues I can find.
Thank you.
I did however ever pick up a basic 6 channel receiver from hobby king. I am going to try that first seeing as my replacement bec didn’t have the 3.5 mm connectors installed. Another thing to order or see if the hobby store has them.
I might burn burn a whole battery on the stand at the club to see if there are any issues I can find.
Thank you.
11-05-2019, 09:08 AM
#8
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A gent at our club encountered radio interference with a Specktrum set up which resulted in the same fate for one of his birds. Was that new trainer with pusher prop out of the box. There were no mods. We fly near a military installation, so the "conspiracy" theorists are out in full force...
