Looking to do the Airplanes 550 conversion into a 180. Whats the best prop ? I hear the 86x3 mac is the best all round ... anybody got contrary veiws ???

I have a io550d on my 185 with a hartzell 3 blade scimitar prop that works great and is real smooth. The 550 on a 180 turns it into a really nice performing airplane and I think you are going to be very happy no matter what prop you put on it. Enjoy
p.s.- you might try the skywagons.org sight also.

Go with the McCauley 84 or 86. OR, try the three bladed MT composite prop, and save a bunch of weight.

My experience with the Hartzell scimitar bladed props isn't as favorable as dlhanst's is. I've found them pretty lame in pulling power, especially on floats, which is the real test for any prop.

MTV

Hands down,... Go with the Mac 86" 401 3 blade. Pulls HARD on takeoff and if your pitch stops are set right, with full flaps and idle you come out of the sky on approach that is close to a turboprop. Some people say its 2-3 knots slower in cruise than a 2 blade, I haven't seen it. You will be happy with it I'm sure.

Splashpilot,

What did the Snider speed kit do for your cruise? I have a '59 wagon on 8x50's and have been looking at the kit for years now. Is it worth it?

As a general rule. long props "pull harder" and three blades are smoother, but heavier and less efficient than two. The Scimitar is a little different because if you measure the leading edge, it's longer than the same diameter straight prop and the MT's are light for a three blade.
I gained ten pounds and lost about two mph on my Maule going from two to three. I don't think the three blade Scimitar pulls as hard either, but that is only seat of the pants. It is almost turbine smooth though. The Scimitar is quite a bit less loud at the same RPM if that is a consideration. More ground clearance with the Scimitar also, but in a short take off or climb contest, I think the two blade would win every time.
That's a Maule of course which is not what you asked, but I bet the results would be similar.

180 Driver,

I think it is worth every penny. With the P-Ponk O520, the 86"Mac 401 prop, and the Snider Kit its TAS is 160 KTS at 8500' Std. OAT. When I first put it on I only saw 5 mph indicated increase at 4500'. But then remembered that the airspeed claims of 8-12 knots were TRUE airspeed. So I climbed to 8500' and did the calculation. It gave a 10 knot increase. I checked it 3 times thinking I screwed up the calculation, but its correct. And this is with 8.50's. There is a write up somewhere where Snider did a speed trial and found the 8.50's are as fast as smaller wheels with pants by 1 knot. Its amazing how dirty the gear legs and brakes are on a Skywagon. You will notice you have to power back sooner on decent, because it maintains speed very well.

Now the the downside. Make sure you get a detail oriented A&P to install it because its a b$%ch to install correctly. It can easily take 12-14 hours to install, with swearing. You want the tire/faring spacing tight, 1/8-3/16". Also make sure you run the trim up and down to check the spacing on the horizontal faring since the spacing will change based on trim position. It does take a little bit longer (15-20 min.)to inspect the brakes or jack the plane up. But the material used is incredibly strong.

Make sure you get a good fit and you will see the speed increases as advertised. It's not magic, just aerodynamics. Yes I am very happy with it.

a64,

Nope, the results between a two and three blade prop on 180/185's is a no brainer. The old two bladed props just don't pull as hard the newest generation three bladed props. The Mac will just flat outperform anything around, in my experience. The MT is good as well, and much lighter (-30 pounds, I believe, vs a comparable 3 blade), but I doubt it will pull as hard as the Mac 86.

And, smooth is huge, when you consider all the cracking, loose fasteners, etc that are common on older Cessnas that have been running two bladed props.

On these airplanes (180/185) two bladed props just don't make much sense these days.

On Maules, my experience with the three bladed props was that they were heavier, and didn't perform as well. This was 2 and 3 bladed props on the same M-7. Different airplane, different problems.

MTV

On the same IO-520 equipped 185, on the same day, we tested a two blade MT against an 88 inch Mac three blade 401. The MT substantially out climbed the Mac to 1000, 2000, 3000, 4000 and 5000 feet. We didn't feel we could accurately measure take off perfromace, so we didn't try to do so.

We will be soon flying an IO 550 powered 185 with an 88 inch Mac 401 three blade and an IO 550 powered 185 with an MT three blade, so soon we should have some feel as to which prop pulls better on an IO-550.

George

Thanks all for the feed back. Looks like 86 x 3 mac it is


Dont know how I got this thread in the accident analysis section ? probably one beer too many last night

Wonder if a mod can put the thread in a suitable section please.

Aussie,

It was probably an accident

MTV

I have the mac 86 with the 520, pulls a lot better than the old 2 blade but i'm sure the newer engine helped some, 23 squared at 6000 i usually indicate 120 to 125 knots, 850's and flint tips probably slow me down, this is at full gross with an aft cg

I wonder if the high RPM of the 550 put's a long prop's tips so far into transonic that they lose efficiency? Even Mooney's perform better with two blades.

A 550 turns 2,700 on takeoff versus 2,850 on the 520. So high tip speed should be less an issue on the 550.

Around here, folks seem to think that a 86 Mac 401 is better on a 520 and the 88 is better on a 550, but I haven't seen any data as to why.

George

Check out the PPonk website; www.pponk.com. Steve has some pull test data that is quite interesting. Also, ask him about the Hartzell blended airfoil propeller that he has Stc'd.

One should bear in mind that static pull tests are a very small glimpse into the performance characteristics of a given prop/engine. As the airplane accelerates, virtually all the forces change, some radically, so using static pull as one's only evaluation factor will not fairly represent the performance characteristics of a prop.

It's not a bad place to START, of course, just not the whole story. And, I've seen a couple props that pulled pretty hard in a simple static pull test, but didn't takeoff or climb as well as the competition.

Ponk's little algorithm is a good place to start, but then talk to people who are running the props on comparable engines before you plunk down wads of cash.

MTV

In the flight tests required by the FAA to obtain an STC (must be done by a certified independent test pilot), we have always found static thrust to be indicitive of TO and climb performance. The MT props we have STC'd for the Cessna's (and Husky, Scout and Bonanza) all use the same -58 series scimitar blade. This blade was developed by my business partner specific for best performance on 470 and 520 powered float planes. It incorporates multiple NACA airfoil shapes along the length and really does well at mid-high RPM's. Here is a link to the actual test results obtained by this STC test pilot on the same plane, same day, same technique at max GTOW and fwd CG. The engine is an IO-520 on a C185.
http://www.flight-resource.com/PTD/Cessna185.pdf

All our props are 210cm (83")diam. We use the 3-blade when there is enough HP to drive it, otherwise the 2-blade is used on stock -470 motors.

They cost more than alum (about $10K for 2-blade, $12K for 3-blade) but are life unlimited, much lighter, turbine smooth, cost less to overhaul and provide better performance than alum. MT is to props as Bose is to sound. And like Bose, we have always offered a complete satisfaction gaurantee with no returns in over 5 years!

There is a ton of detail info on our website:
www.MTProps.com

Best regards,
John Nielsen, General Partner
Flight Resource, LLC
World's Largest Volume MT Distributor

Aussiedog wrote:Dont know how I got this thread in the accident analysis section ? probably one beer too many last night

Wonder if a mod can put the thread in a suitable section please.

Done !