907Pilot wrote:DenaliPilot -

Do you run an 8042 on yours then?

Matt

I'm not the best source for hard numbers on prop performance. The following is mostly just impressions. But here's some background to help decide if my missions and configuration are applicable or not:

It's been four years since I went from the 7653 to the 8042. It's a bit hard to recall the old performance. Also, I went from 8:00s to 8:50s to 26" GYs during that time span (and also run skis in winter), so there were some other things affecting my TAS. And I'm on 180 gear legs, so my AOA is different from factory geometry. I also have an A model engine, with a couple venturis hanging off the side of the cowl slowing me down.

I bought this plane in Maine, and flew it up to Alaska. That was about six years ago. I had 8:00s and the 7653 prop, and I remember getting around 110 to 115 MPH. I mention this because it was the cleanest the airplane ever was, and the most strictly X-C flying I ever did in this plane. For that purpose, the gear and the prop were probably both desirable. (could have run 7:00s, I guess).

Here at home, my flights are more sight-seeing oriented and I care less about speed. I operate off of an 1,800' gravel strip at 1570' elevation. Air temps are sometimes up in the 80s, but today it's 45F, so DA isn't much of a concern. I sometimes go in to tighter places, but mostly around the same elevation and OAT. I'm 165 lbs, and none of my passengers are particularly large.

In the 7653 days, I was very conservative and treated my plane as a 2-place. I practiced fuel management more carefully, and I still used most of the 1,800' getting airborne. Climb was 300 or 400 fpm as I recall.

Currently, I can take two passengers (besides me), I worry less about fuel management, and I can be airborne with a comfortable amount of runway left over. With two souls aboard I can see a climb of 500-600 fpm.

At most I may have sacrificed 15 MPH to do this. If you are truly cruising at 120 MPH, My guess is that
you will still see over 100 MPH TAS.

The O-300A redline is 2700 RPM. With the 7653 prop I seldom got close to redline. With the 8042 prop it is easy to come close, but I think it would be hard to exceed. However, I think you will notice the increased RPMs the first time out with an 8042.

With the longer prop, you will appreciate the taller stance afforded by 180 legs and big tires. Especially if you will be operating on gravel or snow. I'm 5'-10" and I still have plenty of visibility over the nose in a 3-point stance.

One more thought is that I bought a new 8042, and replaced a high-time 7653. Some of my performance figures are probably just due to replacing a tired prop with a brand-spanking new one. If you are eyeing a used 8042 prop, you should probably take its condition into account when drawing any conclusions from my experience.

For what it's worth, the 8042 seems to be a very common mod here in Alaska. I've heard that the majority of stock-engine 170s here have it. I'd do it again for sure.

You might just need a new spinner if you go for the 8042. My mechanic found one that was ridiculously expensive. I found another option in Aircraft Spruce or Wag Aero which was fully PMA'd, for half the money.

DenaliPilot

robw56 wrote:I wasn't aware that they had an STC for an MT propeller on a 170... unless it has an O-360.

Vick wrote:Any durability issues with the MTs? They were all the rage in the Stearman crowd for a while but guys discovered that they didn't hold up well operating off of turf. Different construction method for this application?

robw56 wrote: Are you sure your prop is 82'' and not 80''. I haven't heard of anyone running that prop on a 170.