Crashing Question

[trec-r]

I am pretty new to this hobby, although I have been researching for a while and flying cheap coaxial helis for awhile. Is it reasonable to be able to avoid crashing larger multirotors or should I expect that it just going to happen at some point? It seems that most crashes are due to lack of experience and equipment failure. I have a blade MQX coming soon to help get the experience. Can good maintenance and inspections cut out equipment failures that result in crashes? If a crash is imminent what can you do to limit the damage?

The main reason I ask is that I have heard people say that just expect to crash at some point. Do they tell commercial airline pilots the same thing? Just curios.

Richie

 

[Dewster]

Every multi rotor that I've had crashed due to one reason or another. I had a Draganflyer Ti (thermal intelligent leveling system) once. I crashed it twice. The first time was pilot error. I thought that I took off with it in Thermal Intelligent mode and expected it to hover. My second crash was when the folding props folded onto itself. Since it was a quad it immediately crashed.

Enter the world of DJI WKM. I built and flew an Xaircraft DIY hexa frame with the WKM installed. I had a lot of successful flights with my GoPro and Sony Nex 5n camera. My flights were without incident and no drama what so ever. So... not being content with a perfectly operating ship, I decided to "upgrade" to full carbon fiber props. Those props lasted five minutes before sending my craft down. I'm still kicking myself over that one because it flew without a glitch. My FPV equipment, gimbal, frame, two motors were gone. Luckily I didn't have my Sony Nex 5n onboard or the cost would have really totaled up. I was able to salvage my WKM, four out of six motors and four out of six DJI ESC (electronic speed controllers). I test flew the components on a DJI F450 quad to make sure that the parts worked before building my current craft: The Y6.

Lesson learned. Expect crashes. There are things that you can do to reduce the chances of a crash. I didn't foresee my new carbon fiber prop disintegrating after less than five minutes of flight time. If you watch videos of other crashes you'll see that many don't expect the things that go wrong to go wrong. Bad props in my view cause most of the crashes, second would probably be wiring connections, third battery consumption (running the battery completely out), and lastly bad motors. These flight controllers hiccup every now and then. Some of them have fatal hiccups. Thinking about this... most of the crash videos that I've seen were equipment failures.

I've even had my AR-Drone drop out of the sky. It was a faulty board which was replaced by the company for free (first gen AR-Drone).


I really don't think theres much you can do to save your craft if it loses a prop, esc or motor unless its an Octo and even then you'll probably have issues if you don't have the experience. I say build a craft that is capable of carrying what ever camera you want. Keep it light. I really don't see a need to build the biggest craft in town. Small, light and able to accomplish what you want it to do. The bigger craft are more stress, and more money, especially when you see it drop from the sky. Smaller craft are easier to transport.

I converted my DJI F550 into a Y6 hoping for redundant control if I lose a prop, esc or the rare event: motor. I'm still test flying my craft to make sure that it won't drop after a failure. I think it is possible to build a reliable craft. It just takes attention to detail and research into what makes these things crash.

Some will say that you will have a crash just like an automobile. You just want to reduce the chances of crashes and the amount of out of pocket expense if you do crash.

 

[trec-r]

Ok so what can be done to limit the in flight failure of those various parts? Beside balancing props what about a bench top RPM test? I know from my work as a stage hand that a rope has to be able to hold 3 times the load that it is rated for. So for a bench test would say doubling the rpm for 10-15 minutes reveal a faulty prop or just put undo stress on a good one?

What about a replacement schedule? After every X hours of flying replacing parts?

What is the main cause of ESC failure? Heat, age, overdraw? Could something like this help? http://www.uline.com/BL_1055/Heat-Indicator

Just a few thoughts, I really just want to make sure I am doing this as safely as I can and without the need to rebuild when I could have just replaced one part.

 

[Tomstoy2]

If it flys, it dies. Wether rc planes, single rotor helicopters or multi-rotors. eventually, they all go back to kit form. It's not a question of if, but when.

All one can do is to do his homework, start small, learn the ropes and pay his dues.
Once you have a firm grasp of all the components, and how they all interact. then it's time to decide on your next rig. By then you should have a good idea of what works, what you want to achieve, and how to go about building the rig to meet your needs.

Preventative maintenance is a big part of reducing the chances of an equipment failure. Checking over all your connections, looking for anything that has shaken loose, blowing out your motors with compressed air, checking over your props for functionality and security of mounting, batterys for resistance and signs of puffing, the list goes on.

The key to the kingdom is starting small and learning all aspects. There are no shortcuts in this hobby. Only time, persistance, and money can get you there.

To start off in multi's and spend a fortune building a large rig for your first ship is a recipie for more aggrivation than I would care to go thru.
I started off with a Gaui 330sx and had grand schemes of hauling a GoPro and fpv with it. The reality of it was, I did get the Gaui to fly, but it did crash a lot. I never even had the opprotunity to try the rest out, and I've been flying models of one sort or another for 52 years!

After that, I graduated to my current x/a hexa and a WKM. Had one wreck in the beginning, got everything working and am extremely pleased with my results. Now, I feel I'm ready for my next rig, one capable of handling a real gimbal and camera, plus the flight time I want to achieve, but I don't kid myself either. I know that even though I now know what I'm doing with multi's at any time disaster can happen. And, happen it has. Had a bit of bad luck, once when I flew into a power line and just reciently when a prop blade separated in flight.

Truth is, for most of us, that is part of the draw. If we want to fly we have to accept the fact that any time it leaves the ground it might be its last flight.
If we can't accept that, then we might as well take up basket weaving.

 

[Str8 Up]

I disagree. While I haven't taken the MR plunge just quite yet, I recognized early on that avoiding crashes was going to be the #1 priority to building a profitable AP business. Seven years later, I have only had three forced autos and zero crashes. It is possible but it takes a major time committment and attitude adjustment to realize. All six of my SR rigs are all flown manually with no form of stabilization other than flybar and gyro. KISS is never a bad plan. Granted, it certainly didn't hurt that I was a professional pilot for the preceeding 22 years.

If you can get and keep the machines running perfect, life is always good when the phone rings. Saying that crashing is inevitable is like saying its expected to drop a newborne baby once in a while. The importance placed on the act will often dictate the results you get. Pay attention sometime to the care and attention people place on handing off a newborne child. My goal is to never crash and I take extroidinary preventative measures to make that happen. It is said that for every crash, there are at least 100 near misses that almost caused a crash. Pay attention to and eliminate all the near misses and you are well on your way. Nothing goes on my rigs that has not been thoroughly tested first. It also helps to know the exact limits of both your flying ability and your equipment.

 

[trec-r]

So... not being content with a perfectly operating ship, I decided to "upgrade" to full carbon fiber props. Those props lasted five minutes before sending my craft down.

This makes me wonder if a simple bench test of each prop could have prevented the crash? Does anyone bench test their props before they fly them?

Richie

 

[trec-r]

I didn't foresee my new carbon fiber prop disintegrating after less than five minutes of flight time. If you watch videos of other crashes you'll see that many don't expect the things that go wrong to go wrong. Bad props in my view cause most of the crashes, second would probably be wiring connections, third battery consumption (running the battery completely out), and lastly bad motors. These flight controllers hiccup every now and then. Some of them have fatal hiccups. Thinking about this... most of the crash videos that I've seen were equipment failures.

Bad props? Does that mean the fail shortly after take off, or after hours of strain from flying?

Wiring connections, is that from heat or breaking loose from vibrations? Would you include ESC in this list?

For the batteries I thought I had read about telemetry that show battery levels? However I know that may not be accurate but in combination with a timer should be very good at preventing dead batteries. What about replacing batteries after after X charges and Months?

Thanks for all of the input. I think this is really going to help.

Richie

 

[trec-r]

If it flys, it dies. Wether rc planes, single rotor helicopters or multi-rotors. eventually, they all go back to kit form. It's not a question of if, but when.

Yes I agree that nothing lasts forever. The idea is to catch parts before they die to prevent the whole bird from going out in a big epic crash.

Preventative maintenance is a big part of reducing the chances of an equipment failure. Checking over all your connections, looking for anything that has shaken loose, blowing out your motors with compressed air, checking over your props for functionality and security of mounting, batterys for resistance and signs of puffing, the list goes on.

Can you please continue the list? The more we share what we know the more we all can enjoy this hobby or profession.

I started off with a Gaui 330sx and had grand schemes of hauling a GoPro and fpv with it. The reality of it was, I did get the Gaui to fly, but it did crash a lot.

What was the cause of those crashes? Was that your first MR?

After that, I graduated to my current x/a hexa and a WKM. Had one wreck in the beginning, got everything working and am extremely pleased with my results.

What was the cause of that crash?

Had a bit of bad luck, once when I flew into a power line and just reciently when a prop blade separated in flight.

Regarding the blade, did the blade come apart or did it become disconnected from the motor?

Truth is, for most of us, that is part of the draw. If we want to fly we have to accept the fact that any time it leaves the ground it might be its last flight.
If we can't accept that, then we might as well take up basket weaving.

For me I see this as part of the challenge. Can I build and fly something that will not have an equipment failure leading to the death of the bird. I am getting a Blade MQX to train with and fully expect to crash it. But then replace the props and fly again. Each time I want to learn a new maneuver I would go back to the MQX and practice before using the bigger MR. Perhaps I was not clear enough about that in my original post.

Thanks for all of the info.

Richie

 

[trec-r]

Granted, it certainly didn't hurt that I was a professional pilot for the preceeding 22 years.

I had wondered about that. When you started out as a professional pilot were you told to expect to crash at some point in your career? Why do you think there is such a different mindset with RC?

My goal is to never crash and I take extroidinary preventative measures to make that happen. It is said that for every crash, there are at least 100 near misses that almost caused a crash. Pay attention to and eliminate all the near misses and you are well on your way. Nothing goes on my rigs that has not been thoroughly tested first. It also helps to know the exact limits of both your flying ability and your equipment.

What are those preventative measures that you take? Do you mind detailing you testing procedures for components?

Thanks
Richie

 

[Tomstoy2]

Originally Posted by Tomstoy2 Preventative maintenance is a big part of reducing the chances of an equipment failure. Checking over all your connections, looking for anything that has shaken loose, blowing out your motors with compressed air, checking over your props for functionality and security of mounting, batterys for resistance and signs of puffing, the list goes on.

Can you please continue the list? The more we share what we know the more we all can enjoy this hobby or profession.

Every component that goes onto your frame needs attention from time to time. What I touched on were just the most common.

Any metal to metal connection, such as bolts to inserts should be loctite'd with blue locktite, medium strength.

Wires are often overlooked by new beginners. Wire are a source of noise, twisting the wires will eliminate a lot of that electronic noise. Making sure the wires are secure so they do not vibrate against the frame anywhere is critical and often overlooked.

Speaking of wires vibrating on the frame, any time a wire passes thru the frame that point of the frame should have the sharp edge broken with a small diamond file, your wifes nail file, light grit sand paper, whatever works.
My Hexa has the esc leads comming out of the frame and making a bend over the top plate. I split a section of heat shrink and superglue it where the wire will touch. I don't want vibrations to eat into the insulation and causing a short.

Still speaking of wires, I prefer to seperate the high voltage from the low voltage wires at different levels of the frame whenever I can. It's not a good idea to have a low voltage control wire laying across a battery lead wire or and esc, stuff like that.

Sucess is in the details, you can't get too anal.

Did you tip over and hit a prop? Check out the prop thoroughly. Flex it a little and inspect the hub area, see if you can find a fault. Look at the prop blade itself for nicks, this can set up a stress point.
Prop adapters could get bent. Inspect them for damage.
The prop strike could have loostened up the prop nut slightly.

Motor beatings fatigue and wear out. Motors also collect debris. I blow out my motors with compressed air frequently, inspect the leads for cracks in the insulation, and use oil to lube the bearings.
There are lots of arguments about oiling the bearings, I prefer to and have recieved the benefit of long life with the bearings. It's up to you to subscribe to what you want to follow.

New electronics require a burn-in period. Most failures of electronic components will happen in this burn in period. If I replace components, I will keep the Hexa close in for around 10 flights. This is just my rule of thumb. I've lost 1 motor and 1 esc during this burn-in period. Last thing I want to do is to loose an esc or motor a couple hunderd feet up and a 1/2 mile away. Been there, done that, didn't like the experience at all.

Connectors is a huge issue. If you need to add a splice cable make sure it's a top quality cable and heat shrink over the connection.
Same with bullet connectors from motor to esc. Once the motor rotation has been confirmed I heat shrink over them so they can not come loose in flight. Proper sizing of the connector is essential, also. You want to be able to draw the maximum amps the motor needs.

A big killer is vibration. All sources of vibration should be hunted down and eliminated.

So, you see, there is a lot to address. As I said, you can't be to anal.

Originally Posted by Tomstoy2 I started off with a Gaui 330sx and had grand schemes of hauling a GoPro and fpv with it. The reality of it was, I did get the Gaui to fly, but it did crash a lot.

What was the cause of those crashes? Was that your first MR?

Mostly, it was ignorance on my part. You really need to do your homework. It was my first mr and I had grandure schemes for it. A 330 size frame isn't really large enough to lift a GoPro, a gimbal and fpv gear, not to mention it's limited size.
The gu344 controller isn't the best, but it does a fair job on a stock frame with no add ons. I then updated the controller to an fy91q with navigation system without doing my homework and ended up with a $400 paper weight.

Originally Posted by Tomstoy2
After that, I graduated to my current x/a hexa and a WKM. Had one wreck in the beginning, got everything working and am extremely pleased with my results.




What was the cause of that crash?

Motor failure in flight. This was towards the end of the burn-in period. It was fine for the first 3 minutes of flight then all of a sudden the motor just quit. The Hexa still flew but drifted off towards the dead motor direction and could not hold height.
I kept it as level as I could and when she got close to the ground killed the throttle and let it drop the last couple of feet.
Inspection showed a lead came disconnected inside the motor.

Originally Posted by Tomstoy2 Had a bit of bad luck, once when I flew into a power line and just reciently when a prop blade separated in flight.

Regarding the blade, did the blade come apart or did it become disconnected from the motor?

I was using Gaui 8" props, very impressive performance and durability with them on my part. I had one blade on the prop seperate at the hub. Once again the Hexa flew, but couldn't maintain altitude. It went down 1/4 mile out in a pumpkin field and I spent 1 1/2 hours looking for it.
These props served me a long time, but failure of my own dillegence was the ultimate reason for the last crash.

The only people who enjoy crashes are the observers. The pilot has his heart jump into his throat, swallows his pride and looks for the cause and how to eliminate it as best as he can.

You can say you have never crashed, but nobody can say with certainty that it will never happen. The truth of the matter is once it leaves the ground all bets are off.

My advise, be dilligent, be safe and enjoy.

 

[Breezemont]

While I haven't taken the MR plunge just quite yet

No offense, but until you do you really have no idea. The glide path for a MR is rather.... steep.
"three forced autos" = three crashes in the MR world.

 

[Dewster]

No offense, but until you do you really have no idea. The glide path for a MR is rather.... steep.
"three forced autos" = three crashes in the MR world.

lol! Yes... One motor gone on a quad, hexa and it's straight down. I lost a prop and watched my hexa do the Dance of Death. I knew there was no hope and I became a spectator. My craft banked 90 degrees after a flurry of activity and just dropped straight down. It took me an hour of trekking through the woods to find it. Battery was punctured but still supplied power to a twitching motor. The WKM LED indicated a blue fail safe strobe (I turned the transmitter off after seeing/hearing the crash). The heat from the punctured battery was intense. It was like being next to an open oven. I was almost afraid to unplug the thing.

Yeah...no glide slope. I have seen some miraculous saves on Hexas. I'm not sure if they were flying in manual mode or not. My crash looked like a boxer getting knocked out. In action one minute down the next.

 

[yeehaanow]

I think you can count on a crash at some point. There are SO many ways it can come down the odds are strongly against you if you do it long enough. It might take a few years, but it will happen.

I have had one MR crash, and it wasn't pretty, happened like lightening, and confirmed my rule that I don't fly over people.

To be profitable you must build crash costs into the price.

 

[R_Lefebvre]

I had wondered about that. When you started out as a professional pilot were you told to expect to crash at some point in your career? Why do you think there is such a different mindset with RC?

That's hardly a fair comparison. A Cessna 150 costs something like $200,000 new, yet it only has 2 seats, cruises at just 75mph, and it has the interior luxury of a 1960 VW Beetle. Actually that's not true, a Beetle has more elbow room, and better heating. The rest of the price goes into the EXTREMELY high levels of engineering that go into them. They are designed not to fail.

Multirotors are designed foremost to be cheap, even the expensive ones.

Nothing goes on my rigs that has not been thoroughly tested first.

How do you thoroughly test something which has such a low or unknown MTBF? Your testing might have used up all the life. Or do you buy 100 of each gyro, run them for 1000 hours and then pick the one with the lowest MTBF?

I've seen statements like this so many times, but never seen any accurate description of what you're doing.

Myself, I prefer redundancy. I just built an Octo that is PROVEN to fly on 7 motors. I even flew it on 6 motors. Heck, I even tried 5. I got it off the ground but it wasn't pretty...

I'll never understand the concept that SRH's are more reliable. They have SO many single points of failure. (And I ain't bashing them, I fly them too!)

 

[yeehaanow]

+ a million! ^^^

I would guess if you added up all the single-point failures that would result in a crash on a SR compared to all the single-point failures on a MR, the MR would win, having less. (As long as it's a octo or Y6.. etc with a decent power to weight ratio)

All of my incidents on the MR and all but one on the SR were battery related issues. I've had, and have heard about others that have had even "the best" most expensive batteries lose a cell mid flight and bring their birds down. There is no way to test a battery if it will fail on the # XX filght.

When you're over water, autorotation is not going to help.

 

[R_Lefebvre]

All of my incidents on the MR and all but one on the SR were battery related issues. I've had, and have heard about others that have had even "the best" most expensive batteries lose a cell mid flight and bring their birds down. There is no way to test a battery if it will fail on the # XX filght.

What happens in a MR if a battery fails, but you have two batteries in parallel? Does the first battery take down the second? I'd think the battery that is failing will stop outputting amps as the voltage drops, just basic electrical theory, and you'd be flying on the first battery only. So you'd see a rapid power loss, but should be saveable?

 

[Murocflyer]

Along the same lines, can you control a quad if a motor goes out? How about a hexicopter? Can you limp in for a landing?

Thanks,

Frank

 

[R_Lefebvre]

Quad: absolutely not.

Hexa: probably not.

Octo: it depends if you've designed it right, and not everybody has. You need a lot of reserve power.

 

[Stacky]

 

[yeehaanow]

What happens in a MR if a battery fails, but you have two batteries in parallel? Does the first battery take down the second? I'd think the battery that is failing will stop outputting amps as the voltage drops, just basic electrical theory, and you'd be flying on the first battery only. So you'd see a rapid power loss, but should be saveable?

What happened in my case was a double flip and crash due to low voltage cutoff, but that was because I didn't have the esc's set to nimh. My thinking was that "it could never go below 2.8v/ cell", well... when one cell goes out on pack #1, and it causes pack #2 to discharge much faster and lower the total voltage.. IT CAN. It was at the end of my flght, just as I was going to make a high speed run, so the extra amps it needed caused the voltage to drop enough. I think 2 motors next to each other went out at the same time.

I have since had an incident where I flew too long and did not have enough power to land at a 'normal' speed. Luckily it sunk into soft grass and caused no damage. So i think if the esc's were set correct before, it would've just sunk to the ground fast. Better than flipping but still could be bad.

Nice save Stacky! That's what you call JeLLoooo!