Why does 3 blade MT have longer TBO than 2 blade for (I)O-320?

[wickedsprint]

So in looking through MT's downloads, I notice the MTV-11-C/183-59 2 blade has a TBO of 1000hrs while the MTV-12-C/180-119d (57) 3 blade has a full 2000hr TBO. The are props for the 320. The file is the Supp_sb1 one, and it names both props directly.

[osxuser]

Just a stab in the dark, but isn't the 2 blade newer? Perhaps they are working up to a long TBO. Either way, chances are it will calender out and need an overhaul before you hit 1000 hrs.

[Norman CYYJ]

Maybe its cuz the time is spread out over 3 blades instead of 2

[DGlaeser]

I suspect it is the dynamic pulsing effect on prop fatigue life. 3 blade props have different natural frequencies - maybe don't get as close to a prop harmonic as a 2 blade? Just a guess.

[RVjim]

Originally Posted by wickedsprint

So in looking through MT's downloads, I notice the MTV-11-C/183-59 2 blade has a TBO of 1000hrs while the MTV-12-C/180-119d (57) 3 blade has a full 2000hr TBO. The are props for the 320. The file is the Supp_sb1 one, and it names both props directly.

The flight hour TBO is established by EASA (Europian FAA) standards for new propeller designs.

The 1000 hr TBO is given for new propeller designed that is VERY similar to an existing design.

The 1800 hr TBO is given for a propeller that has gone through all of the vibration testing, etc., required for an STC on a certified aircraft.

The 2000 hr TBO is a time increase based on 3 of the same 1800 hr. propellers being overhauled without excessive wear before the 6 year TBO time.

A maximum flight time TBO of 2500 hrs is possible for propellers used on a reciprocating engine.

Service Bulletin 1 is a constantly changing document. When your propeller is getting close to the flight hour TBO, that is the time to look at service bulletin 1.

Jim Ayers
FAA Repair Station # LDSR535X
MT Propeller

[wickedsprint]

Originally Posted by RVjim

Service Bulletin 1 is a constantly changing document. When your propeller is getting close to the flight hour TBO, that is the time to look at service bulletin 1.

Jim Ayers
FAA Repair Station # LDSR535X
MT Propeller

I have to respectfully disagree. I will look at all manufacturer's public data when I am doing research for something as expensive and critical as a propeller...and I will do so as early in the process as I deem fit. Ideally before I buy it.

[RVjim]

Originally Posted by wickedsprint

I have to respectfully disagree. I will look at all manufacturer's public data when I am doing research for something as expensive and critical as a propeller...and I will do so as early in the process as I deem fit. Ideally before I buy it.

I don't mind if you disagree. But I don't understand what you are disagreeing about.

I made a simple statement about how Service Bulletin 1 is actually managed.

As an insight into the flight hour verse 6 year TBO I suggest this.
For a propeller with a 1000 flight hour TBO, or six years, whichever occurs first;
the aircraft would need to be flown about 170 hours per year to get the 1000 flight hours before 6 years is up.
Or over 300 flight hours per year to get 1800 flight hours within 6 years time.

From an annual maintenance stand point:
With the MT Propeller, there is no annual maintenance (no grease added into the hub) on the propeller.

And Serive Bulletin 16 shouldn't be overloooked as a resource for any RPM restrictions on the MT Propellers.
If this isn't a certified aircraft, scroll down to the experimental aircraft/engine section.

Jim Ayers

[wickedsprint]

I thought you were inferring that one should not look at this stuff and consider the TBO limits until they are near, vs. taking them into consideration as one of the comparisons we make when trying to choose between different propellers.

[RVjim]

Originally Posted by wickedsprint

I thought you were inferring that one should not look at this stuff and consider the TBO limits until they are near, vs. taking them into consideration as one of the comparisons we make when trying to choose between different propellers.

Sometimes knowing how the data is managed is as important as the data itself.

MT Propeller Service Bulletin 16 identifies the RPM restrictions on different MT Propeller and engine combinations. The RPM restriction data for a particular propeller and engine isn't likely too change.

Service Bulletin 1 identifies the flight hour and years of service TBO.
The years of service TBO isn't likely to change.
The flight hour TBO for reciprocating engines is presently limited to a maximum of 2500 hours. The current TBO for a particular MT Propeller is listed in Service bulletin 1.
As certain different events occur, the current listed flight hour TBO will be increased to a 2500 flight hour TBO.
I believe the 1800 flight hour TBO is the highest TBO MT Propeller, as the manufacturer, can obtain directly.
Then it requires three propellers being overhauled at the current flight hour TBO before the 6 year TBO expires to get an increase in the flight hour TBO. MT Propellers used on aircraft for flight training are usually the first to get to the 2500 flight hour TBO.

Bottom line. Get your aircraft flying. And fly often.

Jim Ayers