We are flying an RV-7 with Aerosports Power IO-375 with dual PMAGs since more than one year (140 hours) with an Hartzell C2YR-1BPFP/F7497-2.
We followed the discussions in this forum concerning harmonic resonance vibrations with this propeller - engine combination and therefore asked Aerosports Power + Hartzell + emagair do run vibration tests to identify any RPM/MAP restrictions for this combination. However after several attempts to get the test done we gave up end of 2013 and decided to replace the Hartzell propeller with a 3 Blade MTV-9 Propeller. MT recently conducted the vibration analysis tests with our plane. We now received the official E-241 document stating no operational RPM/MAP restrictions with the MTV-9 propeller with the IO-375 + dual PMAGs.
The MTV-9 has been designed for larger engines such as the IO-540 to be used e.g. in an Extra 300. MT recommended this prop also for the 195 HP IO-375.
Using the Dynon SkyView Datalog we now have tons of data to do a comparison of both propellers.
Here is a short summary:
1. Cruise Performance
All tests have been run by leaning to PEAK. The KTAS comparison has been done using the same fuel flow. The Cruise Performance of the Hartzell was measured using 2.350-2.550 RPM. With the MTV-9 lower RPMs (2.200-2.400) and higher MAPs can be used and the engine is still running very smooth. Harmonic resonance vibrations at higher MAPs are no issue with the MTV-9. Lower RPMs allow higher propeller efficiency.
In the range from 45% to 60 % performance (fuel flow at Peak) the cruise performance of both propellers is almost the same. (Measurement accuracy is 1-2 KTAS.) In the range of 65%-75% performance (RPMs > 2.500 required) the Hartzell is 2-3 KTAS faster.
Detailed performance diagrams (KTAS in Density Altitude at a given Fuelflow) are available on request for both props.
Take off and Climb Performance:
The take off run is slightly shorter with the MTV-9. Take off distance over 50 ft is nearly the same. Average Climb Rate to 10.000 ft is almost the same.
Other observations:
The engine is running much smoother with the MTV-9. Less noise inside and outside in particular at lower RPMs (2.200-2.400). With descends at 2.000 RPMs it is a very smooth and quiet ride. The take off noise emission at 2.600 RPM is 0,7 dB(A) lower with the MTV-9. The sound is different and smoother.
Cooling is slightly better - in particular during climb.
Look and feel: The MTV-9 is a big 3 blade propeller (same diameter as the Hartzell) and our RV-7 looks more aggressive with this prop.
Total cost of ownership
The MTV-9 is significantly more expensive than the Hartzell. However it comes with a TBO of 6 Years compared to 5 Years with the Hartzell. This may compensate some of the higher investment cost.
We followed the discussions in this forum concerning harmonic resonance vibrations with this propeller - engine combination and therefore asked Aerosports Power + Hartzell + emagair do run vibration tests to identify any RPM/MAP restrictions for this combination. However after several attempts to get the test done we gave up end of 2013 and decided to replace the Hartzell propeller with a 3 Blade MTV-9 Propeller. MT recently conducted the vibration analysis tests with our plane. We now received the official E-241 document stating no operational RPM/MAP restrictions with the MTV-9 propeller with the IO-375 + dual PMAGs.
The MTV-9 has been designed for larger engines such as the IO-540 to be used e.g. in an Extra 300. MT recommended this prop also for the 195 HP IO-375.
Using the Dynon SkyView Datalog we now have tons of data to do a comparison of both propellers.
Here is a short summary:
1. Cruise Performance
All tests have been run by leaning to PEAK. The KTAS comparison has been done using the same fuel flow. The Cruise Performance of the Hartzell was measured using 2.350-2.550 RPM. With the MTV-9 lower RPMs (2.200-2.400) and higher MAPs can be used and the engine is still running very smooth. Harmonic resonance vibrations at higher MAPs are no issue with the MTV-9. Lower RPMs allow higher propeller efficiency.
In the range from 45% to 60 % performance (fuel flow at Peak) the cruise performance of both propellers is almost the same. (Measurement accuracy is 1-2 KTAS.) In the range of 65%-75% performance (RPMs > 2.500 required) the Hartzell is 2-3 KTAS faster.
Detailed performance diagrams (KTAS in Density Altitude at a given Fuelflow) are available on request for both props.
Take off and Climb Performance:
The take off run is slightly shorter with the MTV-9. Take off distance over 50 ft is nearly the same. Average Climb Rate to 10.000 ft is almost the same.
Other observations:
The engine is running much smoother with the MTV-9. Less noise inside and outside in particular at lower RPMs (2.200-2.400). With descends at 2.000 RPMs it is a very smooth and quiet ride. The take off noise emission at 2.600 RPM is 0,7 dB(A) lower with the MTV-9. The sound is different and smoother.
Cooling is slightly better - in particular during climb.
Look and feel: The MTV-9 is a big 3 blade propeller (same diameter as the Hartzell) and our RV-7 looks more aggressive with this prop.
Total cost of ownership
The MTV-9 is significantly more expensive than the Hartzell. However it comes with a TBO of 6 Years compared to 5 Years with the Hartzell. This may compensate some of the higher investment cost.
