MT prop/shout out to McFarlane

[Walt]

Originally Posted by Planecrazy232

Walt,

I have the same prop on my 6A, O360. Mine is super smooth except for when I throttle way back in cruise, say to 11in mp. Definitely get good braking, but also feel vibration at that setting. Do you feel the same?

We’ll, I avoid low mp setting at higher airspeeds, driving the prop/engine with airspeed can cause piston ring flutter and may‘detune’ a counter weighted crank.

[SteveR]

I just ordered a MTV-20-B/183-50 electric prop for my IO-360, lead time is 9 months, order in May, won't get it until February. I'm surprised they had one in stock when lead time is so long.

Why did you go with the three blade over two? My understanding is that weight is only 1lb less with 2 blades, and cruise is very slightly better with 2, while acceleration is slightly better with 3.

[Walt]

Originally Posted by SteveR

I just ordered a MTV-20-B/183-50 electric prop for my IO-360, lead time is 9 months, order in May, won't get it until February. I'm surprised they had one in stock when lead time is so long.

Why did you go with the three blade over two? My understanding is that weight is only 1lb less with 2 blades, and cruise is very slightly better with 2, while acceleration is slightly better with 3.

The 3 blade is the only one that has been tested/certified on the high compression IO-370 engine.
Whirlwind, which I also looked at had the same advice 3 blade for the 370 was required.

[Rick_A]

As I tend to do, I copied Walt’s lastest upgrade. I flew out to 52F last week and installed the exact same prop on my plane (with Walt’s help of course).

I did a couple of local test flights then flew from Texas to Jacksonville, FL on Saturday. The prop runs very smoothly and overall there is less vibration. (Walt balanced both my old prop and the new one) There is a noticeable difference compared to the 2 blade Hartzell.

On the return trip I was at 7,000 ft where I was running full throttle 23.6 MP. I found that 2300 rpm was the sweet spot. My cruise speed was 159 kts which was maybe 1 less than the Hartzell.

[Taltruda]

Originally Posted by Rick_A

On the return trip I was at 7,000 ft where I was running full throttle 23.6 MP. I found that 2300 rpm was the sweet spot. My cruise speed was 159 kts which was maybe 1 less than the Hartzell.

159 knots? Is that with a O320? If it’s a 360, I would expect Full Throttle at 7000 to be 170+ knots..

[Rick_A]

Originally Posted by Taltruda

159 knots? Is that with a O320? If it’s a 360, I would expect Full Throttle at 7000 to be 170+ knots..

Actually, it’s an IO 370 with high compression pistons. For what ever reason, this is about as fast as my plane has ever been. I have not done any testing to see if there is an air speed error. However, when my IFR check was done, air speed was correct using the test box (we only brought the air speed up to something less than 100 kts). Ground speed correlates well with TAS.

Going from my original O 360 to the IO 370 increased climb performance but it only added a few knots of top speed.

[Walt]

For those interested yesterday's flight at 7500' pretty well confirms no or negligible speed loss compared to what I was used to seeing on the Hartzell BA.
Note the RPM, would never cruise at that low an RPM with the BA, still smooth as glass and noticeably quieter!

[Skykingbob]

Very nice Walt....... I hear a lot about the MT smoothness and look forward to the experience in the near future.....keep posting your observations

[PandaCub]

Glad to hear it didn't significantly affect your cruise speed. While I have yet to try out my -8 at optimum cruise altitudes (7000 - 9000 MSL) with the 3-bladed MT, I really do like its climb performance as well as its smoothness and the aforementioned "airbrake option."

The only head-scratcher in my mind is MT's factory TBO recommendation(s), which seem largely based on time since manufacture rather than time in service.

[riseric]

I see 72 months or 2400 hours TBO in the manufacturer's booklet.
That's for a MTV-9-B/183-50a