Scimitar Gave My M20E 5-6+ KTAS...

[USNA12]

So as the title says, the scimitar is amazing. I had a small incident, not my fault, and got a new prop out of the ordeal.

Prior to this I was cruising at 100 degrees ROP at 153-155KTAS at 7500' and 22.5/2400 at 10.6 GPH

Now I am at 100-120 degrees ROP at 158-162 KTAS between 7500-9500' at 22"/2500 at 10.8-11.1

Im new to GA, wanted a fast plane to put a ton of hours on quickly before meeting ATP mins and this plane has been amazing for it. Only thing its missing is an AP

[EricJ]

Some of that will be due to the additional 100 rpm and fuel flow.   That's roughly a bit more than 4% increase in power.   

So it's hard to separate that and the other changes from differences due to the propeller.    

[Ragsf15e]

36 minutes ago, USNA12 said:

So as the title says, the scimitar is amazing. I had a small incident, not my fault, and got a new prop out of the ordeal.

Prior to this I was cruising at 100 degrees ROP at 153-155KTAS at 7500' and 22.5/2400 at 10.6 GPH

Now I am at 100-120 degrees ROP at 158-162 KTAS between 7500-9500' at 22"/2500 at 10.8-11.1

Im new to GA, wanted a fast plane to put a ton of hours on quickly before meeting ATP mins and this plane has been amazing for it. Only thing its missing is an AP

Did you have a 3 blade before and move to a 2 blade now?

[ZuluZulu]

What do you get at 100º ROP (not 120), at 7500' (not varying altitudes), at 22.5"/2400 RPM (not 22"/2500)?

[Will.iam]

And even then what temp? As that is a factor as well. Got to compare apples to apples or comparison is no good. 

[USNA12]

Ok so lets answer some questions, at 100 degrees at 7500' i was seeing about 158 easy but 159-161 on average. 2 bladed prop the entire time. Temp was maybe 3-4 degrees C colder since the last time i flew it before the new prop. 

[Will.iam]

And was that 22.5” and 2400rpm? 

[jaylw314]

Going from the Macauley to the Hartzell 2-blade scimitar in the J model, I saw no measurable performance change, slightly less noise and slightly more vibration.  It definitely looks cooler though  @USNA12 what model M20 do you fly?

The RPM setting is important for comparison, 100 rpm difference is more than 1" of MAP difference, which equates to about 4-5 KTAS difference

Edited December 15, 2022 by jaylw314

[EricJ]

11 minutes ago, jaylw314 said:

Going from the Macauley to the Hartzell 2-blade scimitar in the J model, I saw no measurable performance change, slightly less noise and slightly more vibration.  It definitely looks cooler though  

That's the usual assessment, that it's mostly a noise reduction.   The Scimitar is about 8lbs heavier than the McCauley it replaces, too.

My airplane has had the Top Prop scimitar on it since I bought it, so I've nothing to compare to.   I like it a lot and it's been trouble-free, but my performance figures seem to be the same as most.

 

[A64Pilot]

37 minutes ago, jaylw314 said:

Going from the Macauley to the Hartzell 2-blade scimitar in the J model, I saw no measurable performance change, slightly less noise and slightly more vibration.  It definitely looks cooler though  @USNA12 what model M20 do you fly?

The RPM setting is important for comparison, 100 rpm difference is more than 1" of MAP difference, which equates to about 4-5 KTAS difference

I went from a McCauley straight two blade on a different airplane to a three blade Hartzell Scimitar. I had no speed gain, may have lost an little and gained 11 lbs on the nose.

But it was smoother, maybe quieter and did look cooler on the ramp.

[USNA12]

Im fairly certain the prop on it before was a Hartzell 

[0TreeLemur]

Propellers have not changed appreciably since the 1930's.  They figured aircraft propellers out before WWII.     The main achievement of the mild sweep at the end of the blade is reduction the local Mach number that reduces prop noise, and an itsy-bitsy increase in efficiency in cruise.  This comes at the cost of slightly longer takeoff roll.  A large change in TAS from a scimitar prop isn't likely. 

The old "A" hub original Hartzell prop on our C was condemned at overhaul for undercut blade roots.   We put a Top Prop on.  No discernible increase in TAS.   Slightly less noise.

 

[A64Pilot]

Here is a prop tip speed calculator, or mach number is about .8 I believe.

https://www.warpdriveprops.com/propspd2.html

Crop duster I used to build was .9. Our props being so short really cuts down on top speed and noise, so a Mooney has very little prop noise regardless of who’s prop is on it

[0TreeLemur]

3 hours ago, A64Pilot said:

Here is a prop tip speed calculator, or mach number is about .8 I believe.

https://www.warpdriveprops.com/propspd2.html

Crop duster I used to build was .9. Our props being so short really cuts down on top speed and noise, so a Mooney has very little prop noise regardless of who’s prop is on it

That site doesn't ask for the airspeed, so it doesn't add in the vector component accounting for forward motion of the machine?