bent prop H

[AH-1G]

@DronAirPro
When I replaced all 6 of my engines, I purchased 8, glad I did. One did not work (defective). So now I have one new and 6 old engines if I ever need to repair one.
Order extra engines, just incase.

 

[DronAirPro]

@Steve Carr
When you look at the blade, there's no evidence of hitting something, no residue of bug or bird, not even any marks on the leading edges of the blade.
we also do not see any chipped marks from ground impact???
I will agree with the possibility of a hair line crack.

@AH-1G As I said to @Steve Carr , I think you're right and that this could be one or even the most probable scenario.
Even if I carefully check the arms before each flight and slightly twist them to feel and ear if carbon fibers are damaged, I may have missed a hairline crack.
I have to say that only the fact that the prop bent in flight and broke the arm didn't satisfied me 100%

Thanks to you as well for your comment !

 

[DronAirPro]

@DronAirPro
When I replaced all 6 of my engines, I purchased 8, glad I did. One did not work (defective). So now I have one new and 6 old engines if I ever need to repair one.
Order extra engines, just incase.

Good advice!
That's why I also have extra arms and engines
Now, I "just" have to repair the H.

 

[DronAirPro]

Just one point that annoys me is what was this flapping noise I eared, some seconds before the problems began???

 

[AH-1G]

It can be very difficult to see hairline cracks unless you were looking for it. It would never dawn on me looking for a hairline cracks during preflight either?

 

[AH-1G]

Just one point that annoys me is what was this flapping noise I eared, some seconds before the problems began???

Moth or butterfly flapping next your ear.

 

[Fred Garvin]

It can be very difficult to see hairline cracks unless you were looking for it. It would never dawn on me looking for a hairline cracks during preflight either?

You don’t do a fluorescent penetrant inspection? Very, very unsafe. Mandatory after every RTT.......

 

[PatR]

Steve brought up a good point about battery voltage. I found early on the factory H batteries would discharge quickly after being deep discharged just once. A battery that experienced cell discharged to 3.1v/cell just once could discharge from full charge to 14 or so volts in only 4 minutes of flight. After that discharge rate increased significantly.

There’s a lot of us that have been flying the H and factory batteries for a long time and those of us that have elected to be on the ground before the battery discharged below 14.4v-14.5v didn’t come up with that number by chance. We did so though many observations of battery performance and reading of the difficulties encountered by many that chose to fly to lower voltages

There’s also the fact that lipo performance was quantified a long, long time ago, along with minimum safe cell voltage levels. 80% of capacity is the absolute maximum that can be extracted from a cell, and that’s when using known quality cells with plenty of attention to how they are treated. Unknown quality cells, which is what we are provided, should not be discharged below 70% capacity and still require good care.

Ultimately, if we see our batteries performing poorly, discharging quickly, failing to achieve a full charge, become puffy, or have elevated IR, we should consider replacing them while limiting how we use them until new batteries are obtained. Regardless of age a lipo can fail at any time for multiple reasons. Usually those reasons are of our own doing. Age and cell quality are the two factors we can’t control.

 

[Steve Carr]

If I were to take a WAG, regardless of the cause of the crash, the flight controller was attempting to level the H. In doing so, more power was needed than could be supplied. The voltage had already dropped to 14.0 at that point. From previous telemetry reviews, that is the point where the FC shuts down the motors.

So the event occurs like this:
Motor #2 breaks
FC applies more current to 4 motors to level the H.
Increase in power draw depletes the batt below the threshold of viable flight.
FC shuts down motors on low voltage

I believe most of the damage occurred on impact and not during flight.

 

[Sarah]

About hairline cracks it seems not to happen on carbon fiber

"When carbon breaks it does so with a tear, crush or puncture. Carbon does not develop small cracks which could fail later like a steel or alloy frame might, by nature of it being a composite material. "

Here are the tests:
Don’t be afraid of Carbon, it’s stronger than you think

 

[Sarah]

Just one point that annoys me is what was this flapping noise I eared, some seconds before the problems began???

Actually I would say problem began right before you've heard the flapping noise... (not after) according to your log files that could bet at about 45:00, 6 seconds later the bird dove.

 

[DronAirPro]

You don’t do a fluorescent penetrant inspection? Very, very unsafe. Mandatory after every RTT.......

Oh ! Yes ! My fault !
Good advice I will try this now.
In fact I inflate the H with air under high pressure and put it under water to check if there are leaks in the structure.

Thank you for your humor, it's always a pleasure to see people who have some and I really mean it.

 

[DronAirPro]

If I were to take a WAG, regardless of the cause of the crash, the flight controller was attempting to level the H. In doing so, more power was needed than could be supplied. The voltage had already dropped to 14.0 at that point. From previous telemetry reviews, that is the point where the FC shuts down the motors.

So the event occurs like this:
Motor 2 breaks
FC applies more current to 4 motors to level the H.
Increase in power draw depletes the batt below the threshold of viable flight.
FC shuts down motors on low voltage

I believe most of the damage was cause at impact and not during flight.

As you can see in my profile, I am french, quite fluent in English but... So, I am going to ask a stupid question: What means WAG ?
I believe you're right about the battery point, as others told me already. It's is something I didn't think about but it is very likely what happened.
But wondering why motor 2 broke.
Well, maybe I'll never know...

Thanks for your comment !

 

[DronAirPro]

About hairline cracks it seems not to happen on carbon fiber

"When carbon breaks it does so with a tear, crush or puncture. Carbon does not develop small cracks which could fail later like a steel or alloy frame might, by nature of it being a composite material. "

Here are the tests:
Don’t be afraid of Carbon, it’s stronger than you think

I practice archery, with carbon arrows among others and I can tell you that if an arrow hit the wood around the target (stramit), it can happen when you shoot at Olympic distance of 90m, it doesn't break most of the time but then the carbon fiber can be dissociated and if you then twist the arrow you can ear the carbon fibers making a scratching noise.
So, yes, carbon can have a crack or more precisely fibers can be disassociated from each other!
Then if you use this arrow again, it simply explodes at the moment you shoot it.
Just ask any archer to have confirmation of this if you don't believe me.

 

[DronAirPro]

Actually I would say problem began right before you've heard the flapping noise... (not after) according to your log files that could bet at about 45:00, 6 seconds later the bird dove.

You quoted me :
"this flapping noise I eared, some seconds before the problems began" and then said: "Actually I would say problem began right before you've heard the flapping noise... (not after)".
Can you tell me what the difference is (noise before problem and problem after noise seems the same for me)? Do you really read posts before answering or was it to confirm I was right (glad to read it from you for once)?

All your comments are negative. It could be interesting if you explained really and clearly your point of view or even better if you brought some NEW ideas or solutions but you don't.
You just always say: no! no! wrong! no! wrong! wrong! It is like this not like that! and so on.
This becomes more than a bit annoying!

On FB, you already had remarks from the forum moderator about the same discussion (you even went up to tell me I should go and consult a psychiatrist) and I had to block you to avoid trolling in which you excels, please don't do the same here!

I think that during all discussion here I tried to be open, to learn, to explain things that I know or believe and to read and appreciate the constructive comments people here had the kindness to write giving details.
So, please don't post just to show you're here and that you know everything, mainly and in fact only what (you believe) is wrong.
If you write intelligent, detailed and substantiate point of view, I will be more than happy to read them carefully otherwise, just stop please!
We are not here to troll or pollute this forum and I don't want this to happen!

 

[Sarah]

, it doesn't break most of the time but then the carbon fiber can be dissociated and if you then twist the arrow you can ear the carbon fibers making a scratching noise.
So, yes, carbon can have a crack or more precisely be disassociated from each other!

Maybe wording is not essential but carbon fibers tears, crushes or punctures. What you describe is tearing. Which is not exactly the same as a crack, oftenly seen with metals, specially hairline cracks. in carbon fiber you would not see much (unless obvious) but indeed you would hear a scratching sound when twisted.

@DronAirPro I maybe missed something, did you write that you changed the motors ? If so why ? and during the remplacent can screws have caused some harm to arms like if not finely placed or if too tight or remplaced by inadapted screws ? Did you hear this typical tearing sound while remplacing ? have you remplaced motors due to a crash ? changed arms previously ?

 

[Sarah]

All your comments are negative. It could be interesting if you explained really and clearly your point of view or even better if you brought some NEW ideas or solutions but you don't.
You just always say: no! no! wrong! no! wrong! wrong! It is like this not like that! and so on.
This becomes more than a bit annoying!

On FB, you already had remarks from the forum moderator about the same discussion (you even went up to tell me I should go and consult a psychiatrist) and I had to block you to avoid trolling in which you excels, please don't do the same here!

I think that during all discussion here I tried to be open, to learn, to explain things that I know or believe and to read and appreciate the constructive comments people here had the kindness to write giving details.
So, please don't post just to show you're here and that you know everything, mainly and in fact only what (you believe) is wrong.
If you write intelligent, detailed and substantiate point of view, I will be more than happy to read them carefully otherwise, just stop please!
We are not here to troll or pollute this forum and I don't want this to happen!

Needless to say thank you for helping you, you are anyways welcome You have already presented your apologies in FB for your behaviour, I accepted them of course. Open your mind let ideas flow-in as they come... If I'm throwing out arguments pro or con and bringing new alternatives to as what happened to YOU, should it upset you ?

 

[DronAirPro]

No, I didn't changed any motors or arms, had no crash and what annoys me is that I didn't ear any scratching sound when trying (slightly) to twist the arms.
Indeed, you are right, it could have been a good reason for the broken arm.
I had, as I said before 2 or 3 "not so good landing" when I began with the H, like many of us I think, in high grass or brambles but I checked everything after, it was long ago and the H did many hours of flight since then.
So, could it be fibers tears, crushes or punctures, whatever, that happened at this moment which caused the problem much later ?
I honestly don't know if it could or couldn't happen.
If you have information about this point, I'll be more than happy to learn about this.

Thanks for your comment

 

[DronAirPro]

Needless to say thank you for helping you, you are anyways welcome You have already presented your apologies in FB for your behaviour, I accepted them of course. Open your mind let ideas flow-in as they come... If I'm throwing out arguments pro or con and bringing new alternatives to as what happened to YOU, should it upset you ?

I presented my apologies in FB, not to you, but to the group because by answering to your aggressive and not constructive comments I (and you = We) polluted the discussion.
As you can see, I think I haven't been upset by any comments (but some of yours) here.
I said many times thanks to all people who helped me if not to you (until your very last post, which was interesting, I appreciate).
I prefer to think about ideas flowing-in as they come, before wring them... As they come.

So, let's stay on the behavior of your last post and let's enjoy nice discussion.

 

[DronAirPro]

@PatR Wow ! Thank you for these information about the batteries.
I knew it was mandatory not to discharge them at low voltage per cell but discharged my H batteries several times down to 14V even once or twice to 13.9V.
So I believe I have to be cautious now, as my batteries are more than likely not so reliable after this, even if they charge fully and don't inflate or heat.
This is very interesting and I will keep in mind this 14.4V limit for the Typhoon H.