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5 Motor Mode Videos

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This video was shot almost a year ago. The drone made a pass over the church and I saw a bird flying straight at it. I thought, "Oh he can't be stupid enough to fly into the drone." Well he was! He took out half of the right rear propeller.

I brought the drone back towards the launch point and was preparing to descend when the other half of the blade came off. You can see and hear the blade eject and fall into the trees in the video.

After the ejection the drone did an uncommanded yaw to the left. I brought it straight down and was going to try to land it on its gear but as you can see it started buffeting as it got close to the ground so I brought it back up and hand captured it.

After I put the drone down, I inspected it for any additional damage. The arm that had lost the blade was cracked all the way through right at the base of the hinge fitting. So it actually flew with half a propeller and the only thing holding it on was the wires for the Motor and the Navigation LED.

I was able to find the half of the blade that came off when the bird hit it. I looked extensively for the half that came off over the trees but didn't have any luck. Amazingly, the bird flew off seemingly unharmed. He may have died from his injuries later but I'll never know for sure.
 
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Here's another video shot after Drone #3 went into 5 Motor Mode.

The drone was 400 feet up over a park in Arlington, Texas. The customer wanted some still shots of their construction project as seen from a distance. The park provided a great location to do that. I was within 5 miles of DFW so I actually requested and got clearance for my flight plan. The flight plan was about a radius of 1 foot and 400 feet high.

I shot a bunch of pictures of the construction project, bracketing the exposure and varying the composition ever so slightly. Then I incrementally panned the camera around and tried to take pictures of the full 360 degree view. The camera got about 270 degrees around and the 5 Motor Mode warning came up on the controller. I quickly switched the video on, brought the landing gear down and started my descent.

As I brought the drone back down I did a 3 point scan:

1. Visual on the drone
2. Controller screen
3. Altimeter check

Between what I saw on the screen, which you can see it in the video as the drone violently rocks back and forth, what I could see the drone doing and what I could hear coming from the motors I knew this was bad. I eventually realized that the camera wasn't pointed straight ahead so I put the Pan Mode Toggle into Follow Mode. That probably wasn't necessary and may have made it harder to detect any additional rocking because while the gyros did stabilize the camera having the landing gear in frame gave a frame of reference that showed how bad it really was.

From my prior experience, and seeing how badly the drone was rocking, I didn't even attempt to land it. Instead I just went ahead and hand captured it. The post flight inspection revealed that all that was left of the propeller was the hub. The motor was very hot, considerably hotter than the other 5.

This was actually the 3rd 5 Motor Mode incident for me. Incident number 2 was shortly after the first one and was the most innocuous of the three. I'd ordered a replacement arm for Drone #2 but Yuneec didn't get it to me before I took Drone #1 to Rhode Island to have an Electrical Engineer look at it. We actually repaired the arm with some boat epoxy and it's stronger than a brand new arm although a little less aerodynamic. We took drone #2 up on a very low altitude check flight and it flew fine. We took it up to about a 100 feet and flew it around no problem. Later that day we took it up to about 25 feet to take some pictures of the house that he and his wife had bought and everything was going fine until I went to land.

The blade on the repaired arm broke and both pieces went flying. Luckily the drone was about 2 feet off the ground. I managed to get it down but it tipped and broke 2 more blades. I wondered if there was some kind of stress on the blade because of the arm repair. What I've learned since then was it was the blade. I'd bought a whole bunch of blades off of Amazon for what I thought was a really good price. I'm lucky that those blades didn't cost me a whole lot more than what I paid for them. Drone #2 has flown many a mission with the repaired arm and OEM blades and I've never had a repeat of that failure. The check flight was the first time I used the Amazon blades and within less than an hour I had a failure. I've suspected since then that the cheap blades on Amazon are OEM blades that failed the Quality Assurance test for balance.

After Drone #3's close call I switched to composite blades. Drone #3 was purchased from eBay for the lowest price I've ever seen a Typhoon H go for. True to what the seller listed its batteries were on their last legs but I've got plenty of batteries so it was worth it. The one problem was I didn't know where he bought his blades. After the crisis at 400 feet the blades went into the garbage and I replaced them with blades I'd gotten from the OEM while I waited for the composite ones to come from China.

The composite blades feel and are more durable than the plastic ones but they are noticeably heavier. They do make up for the extra weight by being more aerodynamically efficient. The time to climb is faster than it is for the plastic blades and unfortunately they have greater ground effect. With the plastic blades I could descend right onto the landing pad. It's much more of a fight to get onto the pad with the composite blades.

I'd be happier if I could fix Drone #1's problem. Ever since he landed on his head he won't bind to a controller. His antenna seems to be bad but I've temporarily hooked in a brand new one and he still won't bind. I also can't get the old one out because one of the screws is stripped and won't come out. Hopefully I'll have time to deal with that soon!
 

DoomMeister

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Thanks for sharing your experiences with 5 motor mode incidents and the ultimate cause for the failures.
 
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Steve Carr

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I've suspected since then that the cheap blades on Amazon are OEM blades that failed the Quality Assurance test for balance.
The OEM blades have Yuneec embedded in the plastic. They are designed to flex which provides a smoother flight. There are dozens of reports of crashes using aftermarket props. They are cheap and break easily. When they do break they often cause other props to fail resulting in catastrophe.

The composite blades feel and are more durable than the plastic ones but they are noticeably heavier.
The CF blades are notorious for being out of balance. They also have a different pitch which makes it more likely to enter VRS when descending. You may wish to carefully check the balance.
 

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