canardlover

Howdy fellows, recently warned a junior member in our club NOT to stand in front of the plane/engine when adjusting high speed needle at full throttle...[:@]....told him in rather harsh words that a blade would not be thrown out in the plane of the prop arc but rather forward towards him standing in front of the plane which was sitting on a table.
Afterwards I began to think........how accurate was my statement really..?...have a slight memory reading in a magazine eons ago that a thrown blade would go forwards in about 30 degree angle to the prop arc.
Anyone out there who can enlighten me/us on this. Let us say we talk about a 10x6 APC prop spinning at 13.000rpm when one blade decides to leave.......guess this can be calculated by someone smarter than me.......If this topic has been treated earlier please direct me, could not find much in my recent search........Thanks and Cheers.../Harald

GrnBrt

My Feedback: (5)

I recently had an engine throw a prop on me and it came at about a 10 degree angle and caught me right in the stomach but then that's a good sized target![&o] I have never in my years in the hobby have a prop throw a blade so can't answer that one, now watch I'll have props tossing blades all over the place![:@]

huggins

I think that generally the the prop will go more or less forward, but as soon as the tip strikes something it will take of like a rocket to either side. I have witnessed this twice. Niether was my plane. Then, just this past week a fellow was running up his 1.20 4-stroke up about three pits over from me and the wood prop exploded at about 1/3 throttle. The pieces pretty much stayed in line with the prop arc. A large chunk landed about three feet from me (about 25 feet away). Fortunately, no one was hurt during any of these three incedents. Bottom line is get behind the prop as soon as you can after starting and be aware of other engines running as you walk around at the field.

Mike

Scar

My Feedback: (3)

My Saito 100 was a little lean, and I tried to rev it up. It backfired and shed the prop, which flew forward and slightly to the right about 30 feet, out onto the runway. I like to make sure my prop is pointed toward open ground, with no one directly to the right or left, if I'm going to adjust the needle or anything. Sure paid off that time.

I've seen other engines shed a prop, they can go 'most any direction, but mine traveled farther than any other I've seen. Once, I saw a wood prop shed a blade when starting, went down & right, didn't hit anyone.

Good luck,
Dave Olson

Bob101

Not sure about props but a spinner will go forward a fair amount until it hits something and go off in another direction as well. Once you get into 3"+ aluminum ones it starts to matter.

Ed

All of the above and always unpredictable .......... Just stay behind it !

js3

My Feedback: (3)

YES! Stay WAY behind it. They can go behind the arc of the prop too. This happened to a good friend of mine.

RCAddiction

My Feedback: (87)

If a prop comes off in one piece, such as when a 4 stroke backfires and blows off the spinner and/or spinner nuts, it will go straight ahead in the direction the plane would travel. I was dyno testing an Enya 53 a couple of years ago and when I got to a larger prop size, as I throttled up, it kicked off the prop and it spun through the air forward, spinning in a perfect circle, hitting the garage wall 20 feet ahead of it, quite hard.

If a prop or spinner fails, due to damage, centrifugal force will tend to fling it directly sideways, but usually with a slight forward motion as well. This is a much less predictable situation.

As others have said, the ONLY safe place is behind the prop!

Stripes

My Feedback: (19)

Yup, we had one at our field that broke and threw a blade rearward at about 45 degrees for about 8 - 10 feet.

I agree it is safer behind the propeller arc but not absolutely so as we found out.

Geistware

My Feedback: (16)

When a propeller is thrown, it should go off to the right and forward. If you are standing to the left of the plane you should be ok. A lot depends on the speed that it was turning when it left the hub. Now if the bolt shears at the hub, it will tend to leave at a 90 degree angle inline with the direction the blade is facing.

FLYBOY

My Feedback: (11)

Had a guy at the field testing a saito 180. He kept yelling at people to get behind the prop arc. I thought to myself, that thing won't throw the prop, never seen one do it yet. The though no longer left my mind and zzzzziinggggg! The prop took off and went about 65 feet forward and maybe 20 feet to the left of the plane. Hit a plastic fence on the way by and put a ding in it. If someone would have been standing there, they would have gotten cut pretty bad!

Lesson learned! [X(]

Stay behind the prop! Have seen too many people hit with them. Heli rotor hit a guy and he had a pic on here. Hit him flat across the gut, and the bruise was about 5 times wider than the blade was. Not pretty.

canardlover

Well, this appears to be more complicated than I thought. Now we are not even safe behind the plane...[]......food for thought....thank you all for contributions so far....Cheers/Harald

center of the universe

umm.... what is a prop arc?

Scar

My Feedback: (3)

The tip of the prop travels through an arc, a curve. The geometric plane that contains that arc or curve, we refer to as the prop arc.

Best wishes,
Dave Olson

randall1959

My Feedback: (11)

A long time ago a guy on the flight line was tuning his giant Bingo. The prop broke completely in two, and one side went straight down the flight line. It zipped right past my ear and I was about thirty feet or so off to his side. The other piece went straight up and fluttered back to the ground, behind the plane as the wind was coming from across the runway. Tore one hell of a hole in the poor guy's hand too. The culprit was a knot in the wood.

BasinBum

My Feedback: (2)

I got hit in the arm by a thrown aluminum spinner from 15 feet away while walking thru the pits. It was more like a carpet burn than a cut and I think it was just by chance that it didn't slice me instead. Only safe place is behind the plane.

All to often I see spectators that don't know better (and should not be in the pitts in the first place) standing with children in front of planes. Then we tell them to stand behind and they go over to see someone start up their turbine and get told the opposite.

tailskid

My Feedback: (34)

My son and I were 'testing' a used 3W100 w/ carbon fiber prop/aluminum spinner. We decided to try and start this 'new' creation by starting it in the driveway, 10 feet in front, facing the house. I had just started it and immediately proceeded to go behind the prop arc. The engine was at a high idle (1500 RPM max) and my son reduced it to idle then bumped it up / down a couple of times. AT NEARLY IDLE the spinner/prop decided to go their own way. The prop (28-10) almost hit the roof of our two-story house!

It turned out the previous owner had used some aluminum bolts to hold the prop on and all of them (when we finally found them) were all bent!

Anytime I start ANY engine, I'm the fastest moving, overweight accumulation of protoplasm - until I get behind the prop!

I started a threat once dealing with one rule (and I HATE rules) every club should have (and some have too MANY) is you never adjust an engine from the front - or take a tach reading in front.......you are just a 'target' waiting to get pegged!

Jerry

Clark L

Here's an old thread that should be of interest to you guys...

http://www.rcuniverse.com/forum/fb.a...821&key=darwin

Note that the departing blade went BEHIND the aircraft.

P-51B

My Feedback: (5)

The prop can leave the arc in any direction, not just right.

The centripital acceleration will carry it out of the prop arc in a straight line trajectory from the point at which the break occurs. Forward or backward motion will depend on how the prop reacts. The typical pull of the blad is forward, but, upon separation the blade could "twist" while in its path. That would affect how far forward (or backward) the blade goes. I have not personally witnessed one that went backwards, but I guess that theoretically it is possible.

Cyclic Hardover

My Feedback: (3)

I have seen my fair share of props flying off and frankly, they can shoot off in any direction.

slopoke

My Feedback: (16)

We reciently had a prop come off that went to the right, the spinner went to the left. The plane had not been flown for a while. It had a wooden prop that we think shrank ofer time and loosened it. Just a theory, but its a good idea to check props that have been stored for a while.

Slopoke