Cessna FT337GP - 3 blades prop

[Alainb]

Hello Guys

After a long search I found i nice FT337GP which could fit my needs.

As one of the prop has to be overhaul, I am thinking to replace it with a 3 blades prop ML Propeller.

Any user out there ? Plus & Minus ? Perfomance etc etc

It might be a stupid question ... but is it possible to have 3 blades on the rear engine and 2 blades on front ?

Thanks

Alain

[Learjetter]

Alain,

The MT props must be installed on both engines per the STC.

Search this board and you’ll find several threads with posts about the props.

I like mine, but they were on my plane when I got her.

LJ

[Dr.Dan]

I have them on my plane, but they were there from the previous owner. I can't do any direct comparisons to know what the benefits are. Are they slightly quieter, smoother, better climb? Yeah probably.

One thing I do know, is that they are relatively fragile. I've had to send the props out for repairs twice. An isolated rock chip can require repair. Repairs are relatively easy on the composites but it does mean removing the props and sending them out to a certified shop. For this reason, I would never land on a gravel strip with mine; the chance of the rear prop taking a rock chip is too great.

DD

[n86121]

Excellent news!

As I understand it, the most efficient propellor in cruise has ONE blade, as that represents the least drag, but has terrible static thrust (will take a long time to gain speed from standstill or to climb).

There actually have been single blade balanced experimental props.

https://en.wikipedia.org/wiki/Single...e%20powerplant.

Two blades are obviously more nicely balanced, at least aesthetically.

Three blades will give more static thrust. From a standstill, able to move more air per rotation, so are able to accelerate the aircraft (or climb) a wee bit faster as they can produce more pressure. BUT, in theory, 3 blades should be slower in cruise than two, as one now has to drag three blades through the same air (rotationally).

That's why heavy turbprops will go to four blades. They can accelerate / climb the aircraft faster than fewer blades, where speed or absolute efficiency are less a priority.

That all said, I would think 3 blades dynamically balanced would tend to break up engine pulse vibrations and should result in a slightly smoother ride.

However, a good dynamically balanced prop (on the airplane) should get close to the same results.

[Alainb]

David ,
Thanks for you replay
I guess the main advantage of the three blade would be the a bit noise reduction... and here in Switzerland it would be a "plus".

I discuss with MT-Propeller and they confirm to me you could have a rear 3 blades and a front 2 blades... interesting.

On my 206 I installed a 3 blades and the noise decrease a lot.

Thanks for your returns

Alain

[mshac]

As the old saying goes, "there is nothing free in aviation." If you increase your rate of climb with three blades, you will lose cruise speed.

My 310 still has two bladed props, even though all the cool kids switched over to three blades. My reasoning is the airplane spends most of its time in cruise flight, so I choose to optimize flight in that condition. I've flown formation with similar 310's, and the two-bladed birds are consistently 3-4 knots faster at the same fuel flow settings in cruise flight.

Plus its less expensive to keep the props you've already got!

[wslade2]

How do the MT props compare in weight vs the standard props?

[Alainb]

read that
https://www.cessnaskymaster.com/props.html

[wslade2]

I knew I had read somewhere the MT props were lighter. 60lb weight savings nothing to sneeze at.

[DaveM]

Hi, Dave McFarlane Here,
McFarlane Aviation products is a North American distributor for the German MT composite props and hold a lot of STCs for the props. The MT blades have a very special wood core that actually dampens or absorbs vibration. The core is then laminated with a composite outer structure to add strength and protect the core. This construction gives the props a lot of advantages over aluminum or hollow core composite blades. Field Reparability is one of them. The owner or mechanic is allowed to make repairs from nasty rock damage in the field by simply sanding the rough edges of the crater and applying J/B weld from the auto parts store and sand and paint. Sever damage requires applying a layer of fiberglass in the field over the epoxy repair. The generously allowed repairs are outlined in the MT owners manual. Quick and easy without removing the prop. I do not know where this wives-tale about difficult repairs and taking the prop off for repairs comes from. Other manufacturers hollow core props are very limited in reparability as they strictly rely on the strength of the composite. MT is the easiest prop to repair. When repairs are done the airfoil is always maintained and material is never taken away. Repairs do not take strength away. The leading edge is nickel-cobalt and bullet proof. We have a video on our website of a guy shooting the leading edge with a 22 rifle without damaging it. https://www.mcfarlaneaviation.com/re...T%20Propellers
Rocks can't touch it. Aluminum blades are very sensitive to vibration stress concentration from rock damage. Stress concentration and cracks are not an issue with wood and composite. The MT props do save a lot of aircraft weight and improve performance.

The hub centrifugal load is drastically reduced by the fact that the blades weigh 1/3 the weight of aluminum and put a lot less gyroscopic loading on the crankshaft in turns. The MT props are built for up to 4,000 HP and up to 11 blades and have never had a blade failure. If a prop strike happens, the blades take the damage and the engine and hub generally are saved.

[Alainb]

Hello Dave
I am in contact with MT Propeller in Germany. I am thinking to replace my rear 2 blades by a MT 3 blade. Will keep you inform
Thanks
Alain