- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
Could it be a gun-shot, that twisted the prop ? Or a big wasp unseeable from far away... just throwing out some guesses after reading all posts.
bent prop H
- Thread starter Sarah
- Start date
- Status
PatR
Premium Pilot
Actually, after folding his sample prop by hand he did provide ample structural evidence the prop could have bent in flight. It also could have bent at time of impact if the initial impact was at the prop location.
If the prop bent in flight it might have been responsible for inducing the vibration necessary to break other stuff.
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
Well here's a sample with half cut props... take a look.
These having very weak points ( in the cuts) they should logically bend... during fight.
These having very weak points ( in the cuts) they should logically bend... during fight.
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
You've said it : "folding his sample prop by hand"
by hand, so there must be an external force to bend it, because as video proves it, they don't just bend during flight.
Not same drone (weight is really different), not same motor arms, not same blades (I could bend and cut mine really easily), so not very representative!
The point is that with blade completely cut and this is, in my opinion, quite close from a blade bent to near 90°, we could see strong vibrations on the arm and the drone didn't fly anymore!
This video is very interesting for a Mavic and has useful information but isn't closely correlated to what happened to the Typhoon H.
Even if it is an interesting video, it doesn't confirm nor invalidate any of the theories experts proposed here!
Last edited:
arruntus
Premium Pilot
- Joined
- Aug 19, 2017
- Messages
- 1,851
- Reaction score
- 730
No, but it's a good video to see how plastic propellers behave. That's normal. Not that it bends 90 degrees and stays that way. In the video you can see perfectly that it goes back to its original form, that it bends slightly is normal, even more so in the video, but it goes back to its original form which is the important thing. Otherwise, the brutal vibrations appear, even in the first flight says it flies perfectly but you can see that the gimbal vibrates more than normal.
Oh yes! I agree and said it. It is for sure an interesting video.
My blades don't have a proper elastic characteristic, they bend easily and don't come back.
Otherwise, as I said all explanations proposed here are possible.
Just trying to figure out which one could be more probable than others.
And, at least for me, it is still hard to say!
My blades don't have a proper elastic characteristic, they bend easily and don't come back.
Otherwise, as I said all explanations proposed here are possible.
Just trying to figure out which one could be more probable than others.
And, at least for me, it is still hard to say!
- Joined
- Jul 4, 2017
- Messages
- 4,258
- Reaction score
- 2,025
- Joined
- Jun 11, 2018
- Messages
- 101
- Reaction score
- 25
- Joined
- Jul 4, 2017
- Messages
- 4,258
- Reaction score
- 2,025
PatR
Premium Pilot
All wood, plastic, and carbon model props deflect to some degree under a centrifugal thrust load. Full scale planes and helis do as well, which is why life cycle periods are imposed on them. That they bend or flex in flight is not in question, only the amount and amount of efficiency lost is a question. Wings on airplanes bend slightly when generating lift or experiencing gust loads. The ability to bend and return to original shape in called elastic deformation and part of the design process.
The use of cheap or soft materials can most certainly contribute to being bent and fail to return to the original shape under load, which is called plastic deformation, regardless of how the load is applied, be that thrust, direct and continuous, or impact. All of the above is part of basic structural engineering.
All propellers are not created equal, and one brand is not representative of another. There’s even quality differences between brands of “soft” props, which used to be common fixtures on “slow flyer” type drones. The props being referenced in this thread were not designed and manufactured using a material that provides structural rigidity.
The video proves nothing relative to a prop bending in flight as at no time is there any attempt to display blade tracking. In any case, the video is only applicable to the effects of flying with with a broken Mavic propeller in a specific configuration.
BTW, if you break the tip off of a stock H propeller it will continue to fly a lot smoother than that Mavic did. Been there, done that.
The use of cheap or soft materials can most certainly contribute to being bent and fail to return to the original shape under load, which is called plastic deformation, regardless of how the load is applied, be that thrust, direct and continuous, or impact. All of the above is part of basic structural engineering.
All propellers are not created equal, and one brand is not representative of another. There’s even quality differences between brands of “soft” props, which used to be common fixtures on “slow flyer” type drones. The props being referenced in this thread were not designed and manufactured using a material that provides structural rigidity.
The video proves nothing relative to a prop bending in flight as at no time is there any attempt to display blade tracking. In any case, the video is only applicable to the effects of flying with with a broken Mavic propeller in a specific configuration.
BTW, if you break the tip off of a stock H propeller it will continue to fly a lot smoother than that Mavic did. Been there, done that.
Last edited:
Oh yes, being an instructor and pilot of light aircraft (about 3000h of flight), I totally agree with you about propellers and wings.
After a flight on "real" aircraft, the blades of a propeller are quite hot at their base due to constraints induced by the twist and bent they support.
It is absolutely normal that they bend and then come back to their initial position and bad materials can bend and NOT come back to their initial position, that's the fact about my props.
As you said the props should be adapted to the drone, weight, speed, rotational speed and so on...
Mines where not (once again my fault, I agree).
Why one bent is still not very clear for me... As it was of very poor quality, maybe an even weaker point in its structure?
You tried a fly with a a stock H propeller missing its tip and it was still flying nicely (well, better than the Mavic in the video)?
This is an interesting point.
Thanks for this information.
Nooo!
I love my Typhoon H, of course I dream of a H520 but it is a bit expensive for me at that moment.
The H is already on my workbench and I am repairing it, as I have some spare parts and will buy the missing ones.
PatR
Premium Pilot
You tried a fly with a a stock H propeller missing its tip and it was still flying nicely (well, better than the Mavic in the video)?
This is an interesting point.
Thanks for this information.
Was doing a shoot on a stage and got to close to an overhead stage light and lost about 3/4” of a prop. Knew it as soon as it happened but the stability remained good so I completed the shot before flying back off the stage to land.
I honestly do not believe the motor pod broke because of a bent prop unless it hit something. It's also possible the motor housing had a hairline crack from a previous incident.
The single most troubling thing I see in the telemetry is the voltage level. There is a significant drop during the last minute of flight before the aircraft's begins to descend. The drop from 14.6v to 14.2v is concerning. It has been my experience in reviewing logs that bad things can happen at any point below 14.4v.
From liftoff to the point of the incident was just 8:13 min during which time the voltage dropped from 16.1 to 14.1.
The single most troubling thing I see in the telemetry is the voltage level. There is a significant drop during the last minute of flight before the aircraft's begins to descend. The drop from 14.6v to 14.2v is concerning. It has been my experience in reviewing logs that bad things can happen at any point below 14.4v.
From liftoff to the point of the incident was just 8:13 min during which time the voltage dropped from 16.1 to 14.1.
- Joined
- Jul 4, 2017
- Messages
- 4,258
- Reaction score
- 2,025
@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 posibility of a hair line crack.
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 posibility of a hair line crack.
Not sure as well if the motor pod broke because of the bent prop.
I didn't hit anything, this is for sure.
I had some "landing" in high grass or once in brambles, so maybe a hairline crack I wouldn't have noticed but it flew many many hours after this and had pre-flight inspection each time.
Of course this doesn't mean that the crack wasn't here.
It was the first time I used these propellers so maybe their very poor quality added to a former invisible crack could be the reason of all this.
Your statement is pertinent and can be another interesting possibility to explore. Unfortunately now, it will be hard to say as 4 arms over 6 are totally destroyed and I can't analyze if a crack I missed existed before or not.
About the battery, yes I noticed it was draining quite fast. Honestly I thought that 14V (3.5V per cell) wasn't so terrible if not good, of course.
Your experience shows that I was wrong, I learned something else. Good to know !
Anyway, thanks for your comment !
- Status
Similar threads
