3-Blade MAS prop test results (log analysis & video)

I've been trying to stay out of this conversation, I do not own any MAS props. My preference has been APC for a variety of reasons and have held true over the last 3 years. I have done a little research over the last few years to gain some understanding for the subject. Not an expert by any means, just an informed opinion.

The following will answer a few questions. Not a white paper study, however there are plenty on the net related to the subject...again search is your friend.

From Hartzell Propeller Co., emphasis mine...

Will a 3-blade prop make my airplane quieter inside?
Yes, in most installations increasing the number of blades helps to reduce noise. Cockpit noise comes from a variety of sources; engine, exhaust, air flow around the fuselage, and the propeller. Vibrations are also perceived as noise in the cockpit. In a single-engine airplane, the propeller blade wake will beat on the windshield producing noise. A 2-blade propeller produces two pressure pulses per revolution, where a 3-blade propeller will produce three smaller pulses per revolution (for the same amount of total thrust) which is inherently smoother and therefore quieter. The 3-blade propeller will generally have a smaller diameter than the 2-blade propeller that it replaces, which also reduces the tip speed and noise. In a twin-engine aircraft, the reduced diameter of the 3- blade propeller will result in less tip-generated noise and a greater clearance between the blade tip and the fuselage. Both of these characteristics will reduce cabin noise.

Sure, not a quad prop, but the concept is the same. I'd venture to bet the tri-blade has an equal amount of airfoil surface as the larger twin-blade. Also a shorter prop is going to be that much stiffer, again less tip flex to generate the buzzing noise.

As noted in P2P's data, RPM did increase and as expected for the thrust needed to hover. If you can live with shorter flight time you will reduce perceived vibrations, as the frequency is higher. @Ralph E. Johnson video is a great example with less vibes...

You guys wanting more thrust at higher alt are going to be disappointed with the 945 tri-blade. Find a 1035~ tri-blade and you'll have what you want. That is what I'm holding out for.... (@Saijin_Naib )

Finally a tri-blade is typically better/easier balanced than a twin-blade. There is physics involved, plenty of white papers on that subject as well.

I wish everyone the best of luck using whatever prop, for what ever reason you choose. It's good to have choices. Peace!
 
Log data and graphs showing actual measured performance data is not an opinion. They are facts backed up by data. Perhaps you could do that too?

Well, I sure can, but won't spend the time

I didn't see any graphs or log data on the noise level!? Do you have some "measured performance data" to prove your point?
I got 78.5 dB vs 82.5 dB for the 2 blades measured one feet away.
 
  • Like
Reactions: brianuc4 and skyhax
I've been trying to stay out of this conversation, I do not own any MAS props. My preference has been APC for a variety of reasons and have held true over the last 3 years. I have done a little research over the last few years to gain some understanding for the subject. Not an expert by any means, just an informed opinion.

The following will answer a few questions. Not a white paper study, however there are plenty on the net related to the subject...again search is your friend.

From Hartzell Propeller Co., emphasis mine...



Sure, not a quad prop, but the concept is the same. I'd venture to bet the tri-blade has an equal amount of airfoil surface as the larger twin-blade. Also a shorter prop is going to be that much stiffer, again less tip flex to generate the buzzing noise.

As noted in P2P's data, RPM did increase and as expected for the thrust needed to hover. If you can live with shorter flight time you will reduce perceived vibrations, as the frequency is higher. @Ralph E. Johnson video is a great example with less vibes...

You guys wanting more thrust at higher alt are going to be disappointed with the 945 tri-blade. Find a 1035~ tri-blade and you'll have what you want. That is what I'm holding out for.... (@Saijin_Naib )

Finally a tri-blade is typically better/easier balanced than a twin-blade. There is physics involved, plenty of white papers on that subject as well.

I wish everyone the best of luck using whatever prop, for what ever reason you choose. It's good to have choices. Peace!

Will obviously need to log RPM data myself to prove this.

Otherwise, I fully agree with one exceptions - There is no way you would be better with lower pitch on high altitude. Thats simple physics and aerodynamics. Low air density will require more work, no matter how you do that - increase RPMs or increase Pitch.
 
Otherwise, I fully agree with one exceptions - There is no way you would be better with lower pitch on high altitude. Thats simple physics and aerodynamics. Low air density will require more work, no matter how you do that - increase RPMs or increase Pitch.
You're likely right, it was a subjective thought as I have no test rig. I fly at 80' MSL with 800kV motors, the twin 1145's tend to be sluggish for me. Once Solo is up to speed they move out fairly quick. If all things are equal, I prefer more RPM.

Different thread, different conversation.
 
It is entirely possible he can barely hear them from normal operating distance. Sound pressure reduces 6dB for every doubling of distance. I know I don't launch my Solo with less than about 10-12ft between myself and the bird. By the above, that means there will be ~15.5dB of reduction between a measurement at 2' and one at 12'. Given the oft stated psychoacoustic '6dB is half the power' [this is a source of MUCH debate, and often dependent on the listener in question], those 4dB could be the threshold line between noticeably audible depending on where one stands.

Just saying. The two statements don't necessarily contradict each other.
 
  • Like
Reactions: Jameson
I tried to put some numbers to the different sounds generated from the stock Solo props and the replacement 2-blade and 3-blade props by Master Airscrew. First, this is not a scientific measurement as I only used one 3DR Solo drone and one set of each type of prop. Second, the wind was light at 5-10 mph but still produced an ambient noise of 50-60 dB at frequencies between 60 and 120 Hz, which overlays the noise generated by the props. Third, the sound of the motors overpowers the sound of the props themselves so the information given by Pedals2Paddles about the motor load gives great insight into the noise levels of the different props. At idle (props spinning but drone not flying) there were two peaks in the sound analyzer for the stock 10” props (5” prop blade), one at 1200 hz (74 dB) and one at 117 hz (31 dB). The 1200 was clearly the screaming of motors making it hard to hear the 117 whoosh of the props. During flight (hovering) the prop sound increased to 124 hz (80 dB). For the 10” (5” blade) two-blade MA props, the idle peaks occurred at 1180 hz (62 dB) and 115 (33 dB). During hover, the prop noise increased to 120 hz (74 dB). This surprised me a bit since the MA props look more aggressive and I anticipated more noise. For the 4.5” MA tri-blades, the idle sound had peaks at 1215 (60 dB) and 119 (28 dB). During hover, the prop noise increased to 125 hz (68 dB). Overall, I found little difference in the sound levels of the different props.
 
Cool. This definitely is inline with what I perceive with my ears. Although I can't use my ears to claim a dB level, the changes you found seem to be inline with what I experienced.
 
  • Like
Reactions: Ralph E. Johnson
I tried to put some numbers to the different sounds generated from the stock Solo props and the replacement 2-blade and 3-blade props by Master Airscrew. First, this is not a scientific measurement as I only used one 3DR Solo drone and one set of each type of prop. Second, the wind was light at 5-10 mph but still produced an ambient noise of 50-60 dB at frequencies between 60 and 120 Hz, which overlays the noise generated by the props. Third, the sound of the motors overpowers the sound of the props themselves so the information given by Pedals2Paddles about the motor load gives great insight into the noise levels of the different props. At idle (props spinning but drone not flying) there were two peaks in the sound analyzer for the stock 10” props (5” prop blade), one at 1200 hz (74 dB) and one at 117 hz (31 dB). The 1200 was clearly the screaming of motors making it hard to hear the 117 whoosh of the props. During flight (hovering) the prop sound increased to 124 hz (80 dB). For the 10” (5” blade) two-blade MA props, the idle peaks occurred at 1180 hz (62 dB) and 115 (33 dB). During hover, the prop noise increased to 120 hz (74 dB). This surprised me a bit since the MA props look more aggressive and I anticipated more noise. For the 4.5” MA tri-blades, the idle sound had peaks at 1215 (60 dB) and 119 (28 dB). During hover, the prop noise increased to 125 hz (68 dB). Overall, I found little difference in the sound levels of the different props.
So maybe not quieter but a different pitch?
 
So maybe not quieter but a different pitch?
Yes, not really quieter but a slightly different frequency. It would be interesting to investigate P2P's observation that the tri-blades were more responsive. I did notice that the hover with them seemed more stable and changing position and altitude seemed quicker; however, I do not have any quantitative measures for that.
 
Last edited:
Yes, not really quieter but a slightly different frequency. It would be interesting to investigate P2P's observation that the tri-blades were more responsive. I did notice that the hover with them seemed more stable and changing position and altitude seemed quicker; however, I do not have any quantitative measures for that.
Yes, not really quieter but a slightly different frequency. It would be interesting to investigate P2P's observation that the tri-blades were more responsive. I did notice that the hover with them seemed more stable and changing position and altitude seemed quicker; however, I do not have any quantitative measures for that.

It seemed to me that there was less vibration when flying at a faster speed. It was a smooth recording at top speed.
Appreciate your research.
 
I tried to put some numbers to the different sounds generated from the stock Solo props and the replacement 2-blade and 3-blade props by Master Airscrew. First, this is not a scientific measurement as I only used one 3DR Solo drone and one set of each type of prop. Second, the wind was light at 5-10 mph but still produced an ambient noise of 50-60 dB at frequencies between 60 and 120 Hz, which overlays the noise generated by the props. Third, the sound of the motors overpowers the sound of the props themselves so the information given by Pedals2Paddles about the motor load gives great insight into the noise levels of the different props. At idle (props spinning but drone not flying) there were two peaks in the sound analyzer for the stock 10” props (5” prop blade), one at 1200 hz (74 dB) and one at 117 hz (31 dB). The 1200 was clearly the screaming of motors making it hard to hear the 117 whoosh of the props. During flight (hovering) the prop sound increased to 124 hz (80 dB). For the 10” (5” blade) two-blade MA props, the idle peaks occurred at 1180 hz (62 dB) and 115 (33 dB). During hover, the prop noise increased to 120 hz (74 dB). This surprised me a bit since the MA props look more aggressive and I anticipated more noise. For the 4.5” MA tri-blades, the idle sound had peaks at 1215 (60 dB) and 119 (28 dB). During hover, the prop noise increased to 125 hz (68 dB). Overall, I found little difference in the sound levels of the different props.


Great data. So essentially you got on hover:

Master Airscrew Solo props - 2 blade - 74 dB - pitched at 120 Hz
Master Airscrew Solo props - 3 blade - 68 dB - pitched at 125 Hz

This is actually better reduction in sound than my measurements.
You got 6dB reduction which as this is logarithmic scale represents more than double change in power.

"An increase of 3dB doubles the sound intensity but a 10dB increase is required before a sound is perceived to be twice as loud. Therefore a small increase in decibels represents a large increase in intensity. ... The sound intensity multiplies by 10 with every 10dB increase." - What's a Decibel

Note: change of Hz will offset the values as the noise will be perceived differently - that is depending on the person.
 
Thanks for the testing!

I experienced the same things wiht 3 bladed MA props compared to the stock props:
  • different higher pitch noise
  • maybe less noise
  • more stable
  • more agile
  • higher power consumption by ~10%
That the 3 bladed props are more agile and more stable can be explained by physics. 3 bladed props tend to be better balanced which could lead to less vibrations. And very important the momentum of inertia is probably lower because it rises with radius squared. If the later is the case it means that the motors can change the speed of the props faster which gives more stability and is more agile.

For my Solo to fly stable I reduced the PIDs in P Pitch by 10% and P Roll by 5% with the stock props. Otherwise it would shake from time to time a bit.
 
Last edited:
very neat, I think the guy who had the idea of circular saw blades was on to something - have you tried inverted flying???
as far as the noise can you hear a pin drop if you type is as a message or do you imagine that it's louder than it was intended, like capitalized letters.... ??? I see some opinheads <-- typo opinions matter to most
 
I flew the tri-blades today and the results were not much different than the APC 10" props. I was flying at 8,000 feet so sea level results may differ.

Without all the calculations and figures they don't sound quieter but more pleasant than the stock props..

It felt like less vibration than the 2 bladed props and I carefully balance my props.

Not sure about flight time but it's not as bad as the figures indicate, altitude may play a role here. Going up the usual trail battery remaining at the end was within 5% of normal.

Overall I like them with two caveats. One, they are a pain to pack; and two I think the 11" props still have an advantage. Maybe some larger tri-blade props would have an advantage in thinner air.

So I'm not disappointed at all I think they are a close second to the 11" props and similar to the 10" props with a more pleasant sound.
 

Members online

No members online now.

Forum statistics

Threads
13,093
Messages
147,741
Members
16,047
Latest member
pvt solo