MT vs. Hartzell
The following is from an e-mail by Jim Ayers (MT Distributor):
I have done propeller cruise testing using a Harmon Rocket 2 with a stock Lycoming 540 engine, and on a RV-6A with a stock Lycoming O-360 180 hp engine. In normal cruise conditions, the MT 3 blade propeller for that aircraft at least matched the performance of the 2 blade Hartzell propeller for that aircraft on the same airplane with the same pilot under the same flight conditions.
The 4 blade MT Propeller on the HR2 that John Starn is talking about was a custom design for John Harmon's HR3 with a special Lycon 540 engine dyno'd at 380 hp.
Tom Gummo's HR2 has a stock Lycoming 540 engine, and the HR3 propeller is not designed for that engine. However, the price was right, and they were willing to give up the performance.
In my opinion, the 3 blade MT RV-10 propeller and spinner would be an excellent choice for your aircraft.
Next: The following is a posting from the Matronics RV E-mail postings:
Subject: Prop test 2-blade, 3-blade, 4-blade
From: JOHN STARN (
[email protected])
Date: Fri Jan 28 - 11:09 AM
--> RV-List message posted by: "JOHN STARN" <
[email protected]>
Very long and anecdotal.
Sent from Jack computer - Tom Gummo
do not archive
There has been a lot of talk lately on different props for the RV and Rocket
series aircraft. I have flown with three different props on my plane. I
have been asked to comment on my experiences.
First let me say that I am a pilot (OK, I like to think of myself as a
Fighter Pilot). I would build again in a heartbeat if the money and time
issue would occur again but I don't think of myself as a builder.
Second, I don't have the training of Kevin Horton or the wordsmith skills of
Doug R. but here is my story.
I have the slowest Rocket build with an IO-540 with 250 HP. (Isn't there a
Rocket with the 235 hp version of the engine?). With that said, it PUTS A
GIANT SMILE on my face each time I fly it. I started with a two blade
Hartzell that John Harmon sells for the Rocket. The six verses
four-cylinder engine different can be felt. I total believe the
six-cylinder is smoother.
Here is my flight test experience (note I don't say data). First, I don't
know the max speed at sea level. I just don't fly that way. I takeoff (at
22 GPH), climb to altitude and bring the fuel flow back to a reasonable 10
to 12 GPH and fly around at 140 to 150 Knots indicated. The speeds seen on
my gauges agree with the GPS but not tested in any real manner. At 11,500
or 12,500, the altitudes I go X-country, full throttle, RPM at 2100 or 2200,
fuel flow around 11.5-12.0 GPH, the 140 Knots indicated produced 180 Knots
True.
I let some dumb-guy fly my plane and he had to stop quickly while taxing
back to the hangar and put the plane on it's nose. NEW PROP required.
Enter Jim Ayers; I met Jim several years ago as my EAA chapter helps ACS run
the Copperstate Dash race, which started at APV my home airport. He ran his
RV-3 a couple of times. Turns out that he was building a Rocket too. So we
talked by email helping each other with building problems. By this time, I
knew he was dealer for MT props. So, I gave him a call. Let me say again,
I am a pilot. I didn't want to wait 6 months, 6 weeks, 6 days or even 6
minutes for a new prop. I want to fly. He told me that John Harmon had a
FOUR bladed MT prop he tried on his new HR-III and the Reno Air Races. It
didn't fit John's requirements. John made me a deal and I had a new prop
for my rocket. I knew up front, both Jim and John, told me that, it would
slow me down. As I wanted a military paint scheme (WW-II), the four bladed
prop just looked too good.
(My 250 HP isn't enough to use the prop properly)
The four bladed prop was notability smoother. While it wasn't really
"Turbine like", but except for the noise, it was hard to tell if the engine
was running (he said with tongue in cheek). As predicted, I lost some
speed. The same partial throttle 10 GPH fuel flows, now produce only 140
Knots indicated and at altitude, the GPS is now reporting 170 Knots true.
Sure looks good thou.
I let another dumb-guy fly my plane and as he was putting the plane back
into the hangar, he hit the prop on the hangar door. (Turns out someone
moved the hangar door while he was flying but he didn't check before moving
the plane.) I contacted Jim and we determined that the prop had to be
returned to MT-Germany to fix the ding. He then said something I never
expected. Jim said, "I have a three bladed prop you can use while your prop
is being fixed." Jack and I took off the prop, drove to Jim's house,
returned with the other prop, and was flying the next day.
I couldn't tell the difference in smoothness between the three bladed or
four bladed props. But the 10 knots lost were back.
Here is my summary:
All the MT props were smoother than the Hartzell prop. I don't have all the
model numbers here.
The two bladed Hartzell and three bladed MT produced the best speeds. I
didn't do enough testing to be able to tell if there was any difference.
But it wouldn't be more than one or two knots, so get the one you want.
The four bladed MT prop caused a lost of 10 knots of speed. However, MT
believes that they have a new design and at 250-300 HP ranges, a four bladed
prop will produce the same speeds as the three bladed prop. So far, MT
props have produced what they told me they would so I would like to believe
them. They want another 2200 dollars to change out the new blades for my
old ones so we won't know. 2200 dollars buys lots of gas.
As for Jim, he comes off as a MT dealer because he is. I also believe that
he is willing to help other builders, etc. He sure helped me out this time.
I am sure that he makes money when he gets group buys for MT props, but at
the same time, where are you going to get those prices if you want one. I
for one will give Jim a little slack on his emails.
Tom Gummo
HR-II, N561FS, 240 hours
Apple Valley, CA
P.S. - All those dumb guys were me.
I currently have the new MT 3 blade prop designed for the RV-10/IO-540. Once I get my RV-10 flying, I will post the flight test results. My hanger buddy, and fellow RV-10 builder, has an IO-540 and a two blade Hartzell and when we both have our 10's flying we are going to do a "race test". Won't those results be interesting!!
Regards,