2-Bladed P-3 Prop?

[jarrodeu]

Re: 2-Bladed P-3 Prop?

Well I could always be wrong. But I still think that it said in an interview on this website that the Wildfire crew put a 3 blade prop because it was more efficient.

[speeddemon]

Re: 2-Bladed P-3 Prop?

You have an eagle-eye, my friend. That's exactly where it is...

Cool. Been there. Done that.

Just one of those things. The hangar looked just a little too familiar.

[jarrodeu]

Re: 2-Bladed P-3 Prop?

I found it!

"Bill Jr.: Thank you. We are running a 3-blade prop rather than the 4-blade. The 3-blade prop is more efficient."

http://aafo.com/racing/2004/wildfire_2/

Jarrod

[speeddemon]

Re: 2-Bladed P-3 Prop?

Click the first link that is labeled "Air show at Misawa one (engines 1 and 2)..."

http://www.lynellen.com/p3orion/japan.html

Now, what's REALLY cool is that that is MY old squadron in those pictures, and better than that, Yates (the guy who took the pictures) was in the squadron at the same time. I believe the VP-40 pictures on the link page were taken about 3 months after I rotated out...but I know that they went to Misawa on that deployment.

Great blast from the past....and great to see the ol' Skypig again.

[speeddemon]

Re: 2-Bladed P-3 Prop?

Okay, one BIG thing to keep in mind. The P-3 was designed to 'loiter around' for 13 hours at a time....low fuel flows, low prop rpm. The "efficiency" to consider here is 'fuel efficiency'.

Putting a lot of blades on the hub of a P-3 or C-130 has NOTHING to do with performance or top speed. It's all about fuel efficiency.

These kind of props would not work AT ALL on an Unlimited.

[AirDOGGe]

Re: 2-Bladed P-3 Prop?

Putting a lot of blades on the hub of a P-3 or C-130 has NOTHING to do with performance or top speed. It's all about fuel efficiency.

I think what prop works best all depends on what airframe, engine, prop brand and model combination are being used, as well as the enviroment to be flown (high speed? High altitude? Heavy payloads?....) What works for "A" may not be the best choice for "B"...


The Bear went from 3 to 4 blades with an improvement, but a lot had to do with the type/design of prop, and not just the blade count.


The wildfire team claims going from 4 to 3 was an improvement (They used blades from a convair 440), but I found nothing about which model propeller they switched from...perhaps they kept the same blades and just switched from a 4-blade hub to a triple, since their article says they lost one blade when the plane nearly nosed over....4 blades may have simply been too much prop for their R-2800...

[Stevo]

Re: 2-Bladed P-3 Prop?

Are these the props you were refering to (page 2)?

http://www.afa.org/magazine/jan1996/0196assemble.pdf

If so, they are listed as "Dowty Aerospace, all composite six blade R391 propellers" here --> http://www.airforce-technology.com/p...dex.html#specs

[Peashooter]

Re: 2-Bladed P-3 Prop?

Here's another good link on the C-130J.

http://www.airforce-technology.com/projects/hercules/index.html#hercules2

Seems more blades are like a better low gear -- better takeoff and climb performance, i.e., more payload or shorter field ops. There've been a few at KLUK with security teams as the presidential campaign rolls through our swing state of Ohio. I saw one takeoff in less distance than my Long EZ! No kidding! Not sure what his load was, but it was VERY impressive. Maybe if Lyle gets the hots to break his time-to-climb record, he can run a Dowty prop.

Can Bear Driver illuminate the prop selection process, or is it "classified"?

[AirDOGGe]

Re: 2-Bladed P-3 Prop?

The 8 blade props I mentioned can be seen here:

http://www.hamiltonsundstrandcorp.com/hsc/proddesc_display/0,3809,CLI1_DIV22_ETI2937_PRD80,00.html

...and here:

http://force.navair.navy.mil/e2_projects.htm

Still no photos of an 8 blade prop on a c-130 or P-3 though (those 6-bladed C-130J photos are excellent....thanks...I was unaware of them....Looks like they got a head start on Hamilton Sundstrand’s idea.)

[Leo]

Re: 2-Bladed P-3 Prop?

I would think the only benifit to more blades would be smoother performance by giving an increased number of smaller power pulses.
The same amount of power would still be instilled into the air assuming both props were optimised for the airframe/engine.

Leo

[Air Race Addict]

Re: 2-Bladed P-3 Prop?

Putting a lot of blades on the hub of a P-3 or C-130 has NOTHING to do with performance or top speed. It's all about fuel efficiency.

Well Brad, I don't know if I TOTALLY agree with that statement. If you look at the attached photo, the prop is designed with a blend of the two characteristics in mind. The Q400 is one of the fastest turboprops in the world. They also have one VERY efficient fuel burn. So good, I think they have gone a long way to saving the Alaska Air Group's bacon over the last several months. Very good in the climb category too. I believe they set a time to climb record in their class. These babies regularly CRUISE in the 425+ mph range, (we're talking ground speed here of course with no tail wind), and I realize aerodynamics has a word in all of this.
They are Dowty 6 blade commercial props. I am sure there is some advantage to the scimitar design as well, probably in the higher prop RPM ranges. Not an engineer, but being around props for 25 years or so, the propeller has come a long way. The question still begs, can a better prop be designed to make our favorite racers faster. Money issues aside, I believe it is possible. Composites provide strength, durability, and light weight. Of course, then you start getting into the W&B thing that seems to be critical in some of these aircraft too. Also Engine RPM.......So........ Hell, maybe I'm just talking out my ###

[Rigby]

Re: 2-Bladed P-3 Prop?

Maybe getting off track here, but I believe the 4 blade prop used on the early Rare Bear was from a DC-7 along with the spinner..

[440_Magnum]

Re: 2-Bladed P-3 Prop?

I would think the only benifit to more blades would be smoother performance by giving an increased number of smaller power pulses.
The same amount of power would still be instilled into the air assuming both props were optimised for the airframe/engine.

Leo

I'm no aerospace engineer, but I am an engineer and I've looked at things like blade count vs. efficiency for things like cooling fans. The basic principles are kinda similar, and its a lot more complicated (even for cooling fans!) than you might think. There are LOTs of competing design parameters that have to be balanced- things like blade design, blade angle of attack, intended air flow speed (airspeed in the case of a prop) anticipated pressure differential (in the case of a cooling fan), operating RPM, anticipated available torque at that RPM, etc. etc.

Just to distill it down a little for a simpler example- lets say we have a 3-blade prop and a 4-blade prop where as many things are held constant as possible- we want them to fly about the same speed, absorb torque from the same engine, and we even make the blade design identical (unlike the Bear with P3 blades on one hub and a Skyraider prop on the other). Starting with the 4-blade prop- at maximum race speed, it turns XX RPM (this needs to be where the engine makes its maximum horsepower, so its really pretty much fixed). The prop governor is going to set the angle of attack of the blades (the pitch) wherever it needs to to maintain the demanded engine RPM.

Now switch to the 3-bladed prop. You put the throttle in the same position and again set the prop control to get the same RPM because you still want the engine making max horsepower... so what happens? With 1 less blade to absorb power, each of the other blades must have a greater angle of attack on the air in order to hold the engine RPM at the same spot. The prop governor complies, and holds the RPM the same as before by setting the pitch to a sharper AOA on each blade relative to the air stream. So the question now is, "are the blades more efficient at the angle of attack they assume on the 4-blade prop, or are they more efficient at the greater angle of attack that the 3-blade prop demands?" Not an intuitively easy question to answer! And its even more complicated when you allow different blade designs to start factoring in, let alone which one induces undesirable vibrations or P-factor.

[speeddemon]

Re: 2-Bladed P-3 Prop?

Maybe getting off track here, but I believe the 4 blade prop used on the early Rare Bear was from a DC-7 along with the spinner..

Yes, you are correct. It had a DC-7 prop until 1971, I think.

[BellCobraIV]

Re: 2-Bladed P-3 Prop?

Rare Bear prop history:
1969-1970, DC-7,
1971-1976, Skyraider With M20A-162-0 blades (late model)
1980-1986/87, Skyraider With M20A-162-0 blades (late model)
1987-1990, Skyraider With H20G-162-0 blades (early model)
Afterwards till 2004, Special fabricated three blade using P3 blades and Constellation Hub.
2004, Skyraider With H20G-162-0 blades (early model)
The primary difference and only visible difference between the M20A and the H20G airfoil sections is the "cuff" or "flap" about one inch long on the trailing edge of the M20A Blade, this was added to give the propeller more load pulling ability rather than speed ability. The original blade profile reffered to as H20G-162-11 was the stock Bearcat blade, and the original blade profile refered to as a H20G-162-24 was the blade profile for the P-51H. The "dash" number signifies the reduction in length from the prototype blade configuration. Thus a 162-0 would be 162 inches tip to tip. and a 162-11 would be 151 inches tip to tip. however in the case of the H20G blades chord remained the same in proportion blade to blade. The DC-7 propeller was originally because it would work and was cheap.
John Slack