180 horse prop comparison video
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
180 horse prop comparison video
This is a good prop comparison video. I like how they admit that these numbers are not perfect, but they tried to do apples to apples testing.
N1235D - 1951 170A - SN: 20118
Re: 180 horse prop comparison video
Having replaced the old Hartzell on my airplane with an MT, I can say for certain that his tests understate the performance improvement that the new design provides.
- ghostflyer
- Posts: 1395
- Joined: Mon Apr 21, 2008 3:06 am
Re: 180 horse prop comparison video
I watched that video with some interest and agree what you said Dave. But one thing I find interesting is that the top speed was only 115 mph [100kts]. I personally get a lot more that 100 kts out of my machine with a fixed pitch sensenich prop at 60ins pitch. His figures are a lot lower than a standard 172 . We do not have that draggey nose wheel also. I have thought long and hard and considered fitting a MT or a composite prop but with those figures and my figures ,I can’t justify that expense .
Re: 180 horse prop comparison video
I agree, David, 100 knots is slow. But their test was just indicated airspeed, not a two-way or loop course, so could easily have some error. I assume their airplane is faster than that. Speaking of indicated airspeed, did you notice the airspeed indicator in that airplane? It's got a 178mph redline. How did that happen?
- ghostflyer
- Posts: 1395
- Joined: Mon Apr 21, 2008 3:06 am
Re: 180 horse prop comparison video
It would be appreciated by a lot of us if we all stated here what our wide open throttle numbers are and say if fixed pitch[size of pitch on prop]. or constant speed and regardless of engine used. The reason being I have seen a 170a only achieve 90kts wide open throttle. It had a 53in pitch prop. It’s static thrust rpm was on the highest figure with parallax. Reason was the prop was totally worn out and the aircraft rigging was a mess. Shhh , this aircraft was a red one too.
- Kevin Pearce
- Posts: 49
- Joined: Mon Feb 26, 2018 8:03 am
Re: 180 horse prop comparison video
A good video and I think a fair comparison using the same technique for both.
The max speed test was flown with the prop fully fine which explains the lower than expected speed.
The max speed test was flown with the prop fully fine which explains the lower than expected speed.
- ghostflyer
- Posts: 1395
- Joined: Mon Apr 21, 2008 3:06 am
Re: 180 horse prop comparison video
That’s a good point on the prop being in full fine .i missed that so that’s the explanation of such a slow WOT speed.
Re: 180 horse prop comparison video
Well..from the skeptic’s point of view... I’m not sure I’d want to spend thousands of dollars to shorten take-off run 30-feet or reduce stall speed 3 mph based upon such ad hoc unverifiable testing. The presenter’s sales-pitch is self-contradictory in so many ways...one that comes to mind occurs around the 3:30 minute point of the video when he blames “increased friction (drag)” of the larger diameter prop for lack of significant top-speed increases.... but within the minute claims the larger diameter makes more thrust. Can’t have it both ways I don’t think.
The weight savings alone...of the composite prop might explain the (very) slightly shorter TO ground run and lower stall speed. But the percentage=gains of those are so small as to be entirely within the possibilities of technique and atmospheric differences between the two days flights. He mentions $7K at one point for the cost of a used prop... so I imagine the new prop is somewhat more than that. The cost-benefit comparison is a no-brainer for me.
What about repair costs of a composite versus an aluminum prop? A nick in an aluminum prop might be repaired on the airframe by the local A&P. I don’t know that the local A&P is qualified or knows how to work on a composite. Don’t know if it’d be convenient to have my airplane grounded with a missing-prop while it’s sent off for evaluation/repair somewhere.
The weight savings alone...of the composite prop might explain the (very) slightly shorter TO ground run and lower stall speed. But the percentage=gains of those are so small as to be entirely within the possibilities of technique and atmospheric differences between the two days flights. He mentions $7K at one point for the cost of a used prop... so I imagine the new prop is somewhat more than that. The cost-benefit comparison is a no-brainer for me.
What about repair costs of a composite versus an aluminum prop? A nick in an aluminum prop might be repaired on the airframe by the local A&P. I don’t know that the local A&P is qualified or knows how to work on a composite. Don’t know if it’d be convenient to have my airplane grounded with a missing-prop while it’s sent off for evaluation/repair somewhere.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
Re: 180 horse prop comparison video
It's not the RPM setting -- that's really as fast as that airplane goes. An airplane equipped with a CS propeller goes fastest at a given throttle setting when the RPM is maximum.
It's a CS prop, not an adjustable-pitch prop. With adjustable pitch (or re-pitching a fixed-pitch) the airplane cruises faster with more pitch because it loads the engine and allows you to push more throttle without overspeeding. That gives you more engine power, because power is torque times RPM. More throttle is more torque and more power.
In the case of the speed test in the video, throttle is always full so maximum engine power occurs at maximum prop RPM. You can't make the airplane go faster by reducing RPM. That would be nice!
It's a CS prop, not an adjustable-pitch prop. With adjustable pitch (or re-pitching a fixed-pitch) the airplane cruises faster with more pitch because it loads the engine and allows you to push more throttle without overspeeding. That gives you more engine power, because power is torque times RPM. More throttle is more torque and more power.
In the case of the speed test in the video, throttle is always full so maximum engine power occurs at maximum prop RPM. You can't make the airplane go faster by reducing RPM. That would be nice!
Re: 180 horse prop comparison video
The prop is not at the "fine" setting when at max speed or at any speed when the aircraft is moving forward. As soon as the airplane starts moving the governor starts increasing the blade pitch of the low pitch stops so as not to allow the engine/prop to over speed. Also a more "apples to apples test would have been the 80 inch Harzell which has a wider cord blade than the 76 and 4 inches more diameter and thrust levels comparable to the MT. MT is careful not to post 80 inch data also. As you may have guessed by now I have the 80 inch Harzell on my 180 hp 170B and am very happy with it even with the extra 15 pounds on the nose.
Tim
Tim
Re: 180 horse prop comparison video
I’ve got the 80” inch as well,
George the spinner is 2.5 K.....yes the prop is only a pile of cash. If we could simply get free knots....
George the spinner is 2.5 K.....yes the prop is only a pile of cash. If we could simply get free knots....
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
1953 C170B S/N 25656
02 K1200RS
- Kevin Pearce
- Posts: 49
- Joined: Mon Feb 26, 2018 8:03 am
Re: 180 horse prop comparison video
Tim
The extra 15 pounds! Is that compared to fixed pitch, Harzell CS 76”, MT?
I ask as I have a Harzell CS 76” on my 180hp 170B.
The extra 15 pounds! Is that compared to fixed pitch, Harzell CS 76”, MT?
I ask as I have a Harzell CS 76” on my 180hp 170B.
Re: 180 horse prop comparison video
Kevin, I have to admit that the 15 pound number is the one thrown around on the internet. I do know that there is a substantial increase due to the required harmonic balancer required with the 80 inch prop. I find one of the major advantages of the 80 inch prop is the balancer which eliminates any RPM restrictions due to harmonics on the Lycoming O 360's with a non counter weighted crankshaft. I have a busy day today but will try to lock down a hard weight increase number from when my airplane was converted from the 76 to 80 inch Hartzell tonight. This happened many years before my purchase of the airplane.
Tim
Tim
Re: 180 horse prop comparison video
My MT MTV-15-B/210-58 is 10 pounds lighter than the Hartzell HC-C2YK-1BF/F7666-2 74-inch it replaced.
- Kevin Pearce
- Posts: 49
- Joined: Mon Feb 26, 2018 8:03 am
Re: 180 horse prop comparison video
Thank you, much appreciated.