Prop failure....... Have you had one??

[49dimes]

I don't know about safer. Much heavier for sure. On my race boats, we turn a 6.5" 4-blade propeller (steel alloys) about 10,000 rpm (they are super-cavitating, or surfacing - and run half in half out of the water), therefore have much higher cyclical loading than an aircraft propeller, but... I can see where you would run into cracking problems due to fatigue. We would thin the blades as much as we dare to get both acceleration and top end, but usually when you found a "good one" it would no sooner let a blade go. That usually ends in a similar result as noted previously where the pieces of the engine and lower unit housing go missing. Have a very strict policy to never have anyone standing radially from the propeller (in front with airplanes as well). At least with wood and carbon the density is so much lower your resultant "projectile" has less kinetic energy than a similar metal design, IMHO.

You make a very good point. And I am certainly just adding to content here. You have to keep in mind that slapping a much more dense material as water vice air is much more violent and understandably would cause fatigue and stress failure at a higher rate.
To me a "projectile" is a projectile and I personally do not want to be in front of it all be it wood, carbon or aluminum.
I am curious to just how far off that missing piece of Terry's prop landed???

 

[emtp275]

Only due to a cheap spinner bolt breaking and the prop ate the spinner but no where near the damage you have just broke my header, I landed is and never killed the motor but could hear the noise once i was on the ground and killed it.

 

[yakpilot]

I had the same thing happen as emtp275 yesterday but it was a spendy Mezjlik spinner cone that let go when I throttled up on an up line. Luckily landed without damage except prop is no longer usable. All of the spinner screws were still tight with little pieces of CF under each one. Maybe my GP 176 EVO was spinning too many rpm on the little 30x13evo L haha.

 

[edgewise]

A couple years ago I had a carbon fiber prop split on the seam of one blade. Noticed a funny noise when pulling out of a hover, I imeadiatly landed and checked the prop,didn't see anything at first,but I twisted the prop sideways and the seam would open,when the pressure was released you would never know there was anything wrong with it. Ever since then I always double check the prop. Sorry to hear that Terry.

 

[stangflyer]

Man, hate seeing an airframe beat up so badly. But the upside is, if it's gonna self destruct, it's nice to get it back to save the goodies. I feel really fortunate as the only prop failure I have ever had was the one I had a couple of months ago with my Sukhoi. And really it was more prop bolt failure than prop failure. Damn Carbon Fiber back plates behind CF props. I can't say when those two prop bolts sheared Terry, (as you mentioned in the lead post of your thread). I've watched my maiden video a number of times and I just can not tell when it happened. But thankfully it started sprinkling and I chose not to do a second flight. I've heard stories of things happening as many of you have pointed out. But never experienced it first hand. I like the fact that Terry keeps us all privy to the fact of this all being educational. I can honestly say I learned something that day about CF on CF. On big motors anyway. But along with that, imagine standing to the side of or in front of a spinning slasher. Wood, CF, plastic, nylon or otherwise, they are extremely dangerous and I know I am going to be paying far better attention than I have in the past. A recent occurrence from a guy at a previous field nearly lost his arm from the elbow down from one of those rotating slashers. It's just too bad the 700 or so stiches it took to piece him back together didn't make more of an impact on taking better safety precautions.

 

[49dimes]

Under the variable forces and circumstances that can cause prop failure it is mostly recognized that wood is the better choice simply for safety reasons (actually insurance hoping liability would be reduced) but that was in due consideration that at the time when engines rarely exceeded 2.5 hp .
Now lets take Terry's DLE 85. 8.5 hp . 4X's the driving force to potentially send that splinter over supersonic speed. Or better yet 18 hp of brute force not just to only send a piece on its way but on its way with authority! (kinetic energy and kenny from south park).
Why does it matter if it is wood, carbon, composite or aluminum???. And it was a material ( wood ) failure causing all the havoc on Terry's plane. Now lets take an even more dense material such as aluminum. Does this same type of incident happen??? I think the insurance odds if studied would say NO! In regards to prop strikes. Is not aluminum just more likely to bend??? (You can make aluminum only so hard with silicon). It is still going to bend and not necessarily snap off like a hardened steel that is brittle.
When it comes to human flesh it's a game of rock paper scissors. This video is graphic but the message is "Being Safe" around propellers and highly "aware" of potential danger. Not "more safe" propellers. I would show a training film I have from my Navy days but it WAY to graphic. This one makes a "typical" point of appeal...... Oh!.....I group props and bullets in the same safety category.lol
Remember when the first female surgeon general said "We need to make bullets more safe" LMAO.

 

[49dimes]

Here is another vid showing a wood prop driven ultra light replica. Wonder what caused the "incident"???

 

[Bill Vargas]

I had a very rare occurrence with a Falcon 32 x 11W prop the other day as well.

I normally spend the week tinkering on my planes and preflighting for the upcoming weekend,,, to include Torque Checking the prop bolts with my certificated calibrated Snap On torque wrench at 90 in. lbs.

Well the other day, while torque checking the prop bolts, the first bolt I checked, the torque wrench went click followed by a a loud SNAP.

I got lucky and was able to pull the broken bolt back out of the hub.

Spinner is a 5in. truturn and the prop is less than 2 months old.

Spinner cone had lots of dust too.

just makes no sense as to why this occurred.

 

[Jetpainter]

Were any of the others loose? Any wear on the prop to account for the dust?

 

[Bill Vargas]

No, not that I could tell as it was useless to mess around with the remaining bolts while trying to figure out what the hell just happened. The back side of this particular prop has the normal TruTurn backplate serration wear marks on it. Bolts are the 12.9 metric grade.

This particular prop is done as far as I am concerned for as I don t trust it. Got another one coming and thinking that last one was just that 1% of "if its going to happen, it will thing"(murphy's law)

I have a really nice band saw so it will be interesting to see what the prop hub looks like underneath the C/F or if there's any large voids, etc.