Rukla

[] Dear friends, if you like to see what hapend when prop was broken in the air ?

http://www.youtube.com/watch?v=Vjy7YxX6bLc

Rukla /Cro/

cncswiss1

at about 3:12 to 3:35 the engine is backfiring badly, that ~may have helped the prop break..

Rukla

I do not agree with that, because the engine was running well. After the landing we examined the broken prop and found a difference in colour at the breakage area. This all indicated on the production flaw, but the prop manufacturer dows not want to admit it.

best regards

Rukla

PLANE JIM

My Feedback: (109)

difference in color-failure may be due to prop strike from previous occurance, mishandling the prop or any other abuse of the prop caused by you.

I do not know but you do not know either-so I can blame you just like you blame a manufacturer.

Rukla

The prop was brand new and from the material structrure you can see air bubbles - which was confirmed by the manufacturer after they examined the broken prop.
We thank god that the breakage did not occur while the plane was surrounded by people (on the ground).
If you woudl send me your e-mail, I can send you the picture of the broken prop where you can see the material structure.

cncswiss1

bubbles in the material are bad for sure. it is good it happened in the air and nobody got hurt

MJD

My Feedback: (1)

Re the color difference, a ot of these unfilled and filled thermoplastics change color under strain, usually they lighten at the areas that have yielded under load. Also, in parts with a wide range of cross sectional thicknesses, injection molded parts often show some fine porosity in the thick areas, although the bubbles should be very small and somewhat evenly distributed. Are they big bubbles? Why not post the picture here?

MJD

PLANE JIM

My Feedback: (109)

please post a picture by all means if there is a problem with MAS we all need to know-I did not mean to snap at you accept my apolgy

Rukla

Jim, for next few days you will have pictures on forum, because I dont know how I take this pictures on, I am waiting when my friend have time than he takes this pictures. If you need immediately, give me your mail than I riplay mail which I send to manufactur first time . When you have pictures takes yourself on forum, thanks

my mail: [email protected]

rvt64

Here are the pictures of the broken prop - pay attention to the material colour at the break area.

Rukla

Dear friends,

now you can see the pictures. If you would like to see the difference in material structure, just break one old MAS prop that you can spare. It is very difficult to break it, and if you decide to try it, you will be able to see the difference in material structure.

Regards,
Rukla

airraptor

My Feedback: (66)

that prop broke from to much RPM!

ke6gkc

I agree about to much RPM. Could it have been the prop tips going supersonic? I could not tell I do not have sound at work.
I hope the airplane is repairable.

Bruce

Rukla

You are wery smart guy, how do you know the engine is overrevving ?

Mike Connor

My Feedback: (5)

I analyzed the video using Doppler and the WaveOScope program. The sound clips I was able to get were not that good so there is some margin for error.
I found the maximum unload RPM to be 10947 rpm with a max tip speed of .587 mach or 456 mph. The aircraft speed was 99 kmh or 61 mph.

MAS props usually do not break. I think you had a defective prop. You were not even close to over revving the prop.

bob27s

My Feedback: (19)

I didnt get to see the video......

was there a spinner installed?

Mike Connor

My Feedback: (5)

Bob, The Youtube video was in the first post. It looked like a large prop nut similar to one that comes with a Jett.

bob27s

My Feedback: (19)

ok.. thanks.

The reason I asked is that blade failures just outboard of the hub like that often come from tight-fitting spinner slots. A spinner rubbing on a blade, not even cutting into it, will cause a stress point and a failure. A spinner cutting the blade will propigate a crack and a failure.

rvt64

From the attached picture you can see that it is a Truturn 1" Hub with the original adapter for ZG20.

cncswiss1

the guy on the left looks like a saboteur

Rukla

[>:]Yes it is, but I think that is not comunist !!!!

airraptor

My Feedback: (66)

from the way the prop looks i have been to several classes on material failures and thats what it looks like. may have been a bad prop, but you also said you knew about the small bubbles but continued to run the prop.

What engine is it on? MS props do flex alot and arent the best for high rpm use unless cut down. A 2 bladed prop will give you the best perfomance anyway, unless ground clearence is an issue.

Rukla

We did not know about any bubbles in the prop structure. When the airplane was ready to fly, we took the most adequate prop for the ZG20 engine. From our experience, we also know that 2 blade prop has better performance and has lower drag, but 3-blade prop is a better choice for scale models, such as Yak54. We do not fly 3D program and are not interested in 3D figures.
We have over 15 different airplanes (warbirds, biplane, aerobatic, etc) and use 2-blade and 3-blade MAS props and so far we had no problems.
To make the story short, the only problem is that we contacted first the manufacturer with the idea of alerting him about the problem. The lucky fact here is that the prop broke in mid-air - had it break on the ground, just imagine what would happen with the model surrounded by people.
The manufacturer responded very unprofessionaly. He even did not offer any replacement for the broken prop.
In one of the previous posts, there was a mention about RPMs over 11000 - it is impossible.
Resume:
Imagine the comments if my friend Robi did not shot a video of the flight?

There is evidently a material flaw, the engine which looses a prop blade in flight, breakes the firewall and the rest of the airplane nose, due to disbalance. In our case, there was also a engine damage - bended crankshaft.

It would be logical that the manufacturer of the prop compensates the damages. His answer was that he would only compensate for the shipping of the broken prop and DVD recording.[:-]

Rukla

Dear friends,

I am grateful for your comments.
I just received by mail my broken prop and a DVD with video recording from the manufacturer with a very foolish reply and with a very uncommercial approach, so I asked my daughter who lives in San Francisco to take the matter to the attorney.
I am 58 years old and I am in this hobby for 40 years. I am sad when someone tries to make a fool of me.

Rukla

Master Airscrew factory compensated for the damages. I am sorry that this incident happened, but I accept that there is allways a possibillity of production errors and I hope that nobody would have the same problem in the future.
We would continue to use MAS props, as this was the only incident in many years of using their products.