Props

Geo_in_KS · Feb 7, 2018

What are opinions here on triple blade props? Any good? Legality issues? Bad/good for stability/performance?

AH-1G · Feb 7, 2018

Geo_in_KS said:
What are opinions here on triple blade props? Any good? Legality issues? Bad/good for stability/performance?

This was discussed in another forum, 3 blades cause more instability according to aero engineers.

Geo_in_KS · Feb 7, 2018

Youre kidding...... I even did a search before I posted, couldnt find it.
Ok, thanks.

BigAl07 · Feb 7, 2018

The most efficient prop arrangement is a single blade but that is a whole other ball of wax (counter balance etc). With the additional blade in the mix we are introducing more turbulence and less "clean air" for the next blade to utilize.

In some cases (high performance aircraft) we utilize additional blades to reduce blade diameter but in those instances it's a trade off that is worth it.

With today's crop of multirotors the majority are utilizing a Flight Controller that regulates thrust, speed, direction etc so installing more efficient (or not) props usually does not equate to a more efficient aircraft like it does in other airframes.

Over the last few years we have tried using different props on the off-the-shelf aircraft with no real benefit and sometimes exactly the opposite of what we were expecting.

Geo_in_KS · Feb 8, 2018

Thanks guys,
Thats basically what I read somewhere else online, but I want to get some pros' opinions.
I think a good example that proves this theory is the C-130. (maybe not a perfect example, but somewhat). More props, more engines, more thrust. And on the C-130J there are 6 props per engine.

aerialimagery · Feb 20, 2018

I know a quad copter won't fly with three propellers but will it fly with two? (diagonally opposed of course).

I would try it but I don't want it to end up upside down churning on the ground.

ArrUnTuS · Feb 20, 2018

If it only balances with one axis, what do you think the other axis will do? Start spinning like a madman making it unmanageable.

There always has to be a compensation, and the base is the same as in helilcopters, the difference is that instead of tilting the rotor gives more power to the rear engines of the direction in which you want to go.

BigAl07 · Feb 20, 2018

aerialimagery said:
I know a quad copter won't fly with three propellers but will it fly with two? (diagonally opposed of course).

I would try it but I don't want it to end up upside down churning on the ground.

It's not likely that most units can compensate enough for 50% loss of thrust.

One thing to understand is that it is POSSIBLE for a Quad to lose a single prop/motor/ESC and still fly but the algorithms etc are not in most off-the-shelf systems. I have seen a Yuneec model lose a prop and continue to fly (not graceful but in control) to a safe landing.

ArrUnTuS · Feb 20, 2018

BigAl07 said:
It's not likely that most units can compensate enough for 50% loss of thrust.

One thing to understand is that it is POSSIBLE for a Quad to lose a single prop/motor/ESC and still fly but the algorithms etc are not in most off-the-shelf systems. I have seen a Yuneec model lose a prop and continue to fly (not graceful but in control) to a safe landing.

A quad lose a propeller and keep on flying? A hexacopter or an octocopter without problem. But a quad.............

Here's an example, but the engine is not completely dead, fails, recovers, fails and lands without much damage. But a total failure of an engine or propeller on a quadcopter means a sure blow.

P.D.: At least I haven't seen one of them stabilize. Let's see if any partner can give an example although theoretically it is not feasible.

P.D.2: The Yunnec video you mean is this? Is very funny

BigAl07 · Feb 20, 2018

ArrUnTuS said:
A quad lose a propeller and keep on flying? A hexacopter or an octocopter without problem. But a quad.............

P.D.: At least I haven't seen one of them stabilize. Let's see if any partner can give an example although theoretically it is not feasible.

Algorithm lets quadcopters keep flying on three or less propellers

ArrUnTuS · Feb 20, 2018

BigAl07 said:
Algorithm lets quadcopters keep flying on three or less propellers

Pufffff, it's playing with fire. In fact I'm thinking about moving from a quad to a hexacopter to avoid these situations and not lose the payload that are very expensive.

And speaking of payload, that same quad with a gymbal and a camera wouldn't end up totally destabilized? It's not clear to me. But thanks for the link, it's interesting