https://www.aviationpros.com/engines-co ... latus-pc12

The more blades the better it seems.

Impressive performance gains and sound reduction. They have also included new performance charts with the STC which has not been done in prior 5 blade prop upgrades for the PC-12 even though there were performance improvements over the factory charts.

- Certified Ground roll distance reduced by approx. 10%; AFMS amended
- Certified Take-off distance over 50 ft obstacle reduced by approx. 15%; AFMS amended
- Climb performance improved
- Aircraft noise level is about 4 dB(A) less than with the original metal propeller
- Cabin noise is reduced by 6 to 7 dB(A) depending on location

Only issue is potential prop damage she using the electric tugs. There isn’t much clearance with the 5 blade props but maybe the shorter blades will help.

Someone with some aerodynamics background is gonna need to explain this one to me. I though more blades = worse performance due to the higher drag.

It's a trade off.

I found it interesting that piston engines are similar,
the trade off of every piston added also increases friction.


That prop doesn't enhance the appearance , IMHO.

it's all fun and games until the line guy needs to reposition the plane

I was thinking the same thing. Funny how 5 blades look better then 4 on the pc-12 but 7 looks worse then 5.

Takeoff and climb is improved (not surprisingly) but the press release is mum on cruise performance.

Noise is way down and I think might be the primary goal here:


Cruise performance might be a wash or down only slightly- the article also mentions a smaller diameter but no other details. That generally helps cruise, especially high speed cruise by delaying Mach effects to a higher cruise speed. Since the gearbox is unchanged then the rpm is almost certainly unchanged, which means the tip speed is lower (this is very important for a propeller airplane that goes fast).

They're calling it an "unducated fan." That (and "propfan," means the same thing) is a loosely-defined term, but "small diameter propeller" doesn't exactly roll off the tongue. It is, however, a distinction with a difference in propulsion- it's different from a conventional propeller but it's definitely not a fan engine* either, and it does fill a niche in between those two.


*turbofan engines use a nozzle; squeezing all that air into a duct and out through a nozzle is what flattens their thrust-speed curve when you compare them to a propeller, which makes a lot of thrust at low speed and less and less thrust the faster you go...

Same.

Also, I thought that more blades means that they're running through the disturbed propwash of the preceding blade and this was bad?

Performance aside, those are big improvements in noise levels.

Same.

Also, I thought that more blades means that they're running through the disturbed propwash of the preceding blade and this was bad?

That's part of it but it's not the only part.

The 2-blade vs 3-blade Barons is an example that is close to home. The 2-blades are generally better cruisers while the 3-blades have better takeoff and climb. One or the other has a slight advantage when the blades are "flying" close to their best L:D. Think of lift, drag, and angle of attack of an airfoil.

The significance of diameter is easy to understand if you think of helicopter rotors and cartoonishly large STOL propellers... or at the other end of things how pure jet engines push a very small column of air very fast.

When the tip speed gets close to the speed of sound then it gets more complicated. Tip speed is separate concept from diameter, even though the size of the propeller affects both.

I was thinking the same thing. Funny how 5 blades look better then 4 on the pc-12 but 7 looks worse then 5.

Why would this be a potential issue with this prop? I would think it would be better with more clearance.

Why would this be a potential issue with this prop? I would think it would be better with more clearance.

Jim, I can't find it but somewhere on BT there was a thread about 2/3/4 bladed props and it was put forth that the "perfect" prop would be 1 blade with counterweight on the other side it would always be running in clean air.

Why would this be a potential issue with this prop? I would think it would be better with more clearance.