Climb prop

[Rosey_La_Roe]

I recently discovered the 1A175/DM8042 prop STC from Kenmore thanks to this great website! I just orderd the STC and want to order the prop this week, but I was wondering what people have done for a spinner. According to the Cessna Parts Manual I have a 0550101-3 spinner on my 170A, but the Kenmore STC calls for a Cessna Part Number 0550162 spinner assembly. The new spinner has a mounting plate that goes behind the prop, while my current spinner has a V-shapped bracket that mounts to the front of the prop.

Doing some investigation I discovered that Wag Aero sell's the 0550162-7 spinner and 0550162-3 backplate, but they say it will only work with a prop extension. I also looked at the Univair website any they sell the same thing, but there is no mention of a prop extension. To those of you that have done this modification (as per the STC), will I need anything other than the prop, bolts and this spinner assembly as I'm not sure what is meant by the prop extension comment.

Thanks for your help!

[twlareau]

We just bolted on a 1A175/DM8043 on our 54B model today. We have the 0550162-7 spinner and 0550162-3 back-plate and needed no prop extension. The whole process took about 45 minutes for the install. The 337 form and log book entry took longer than the install. If you buy the prop new, McCauley includes the bolts and washers. Fred at Kenmore will email you the STC so you don't have to wait for snail-mail. Good luck.

[Rosey_La_Roe]

Thanks for the quick reply twlareau! I'll give Wag Aero a call today and see what this is all about as they are allot cheaper than Univair.

I also noted that you said your prop was an 8043, however the STC calls an 8042. I have heard other's refer to both 8043 and 8042 when talking about this STC, however I assumed this was just an error. I assume that this is the case with your comment? If not, what is the reasoning for re-pitching the prop and was there any special paperwork required for this?

Thanks!

[twlareau]

The Kenmore air harbor STC SA111NW is for a McCauley 1A175-DM propeller. You can call McCauley or a vendor for them and order whatever pitch you want. The STC does not state a manditory pitch just a model. I thought that a 43 pitch would work best for my situation in Colorado. It seems that the most popular pitches are either a 42 or 43.

[bagarre]

The pitch will be dictated by the static RPM limits in the TCDS unless the STC has new limits for the new prop.

If only the STC covered the 6 bolt crank

[twlareau]

The STC has no limits on static RPM.

[Bruce Fenstermacher]

The pitch will be dictated by the static RPM limits in the TCDS unless the STC has new limits for the new prop.

If only the STC covered the 6 bolt crank

No this is not correct because static RPM limits set in the 170 TCDS are for specific props listed in the TCDS. Some times a TCDS lists a generic prop such as "any wood prop" as the 170 TCDS does: "(b) Sensenich 73BR-50 or any other fixed pitch wood" but this does not apply and there is no generic metal prop listed.

Limits would fall to the STC for the propeller and if none are listed there wouldn't be any other than the limit set by engine max RPM.

[bagarre]

My mistake, I thought the TCDS covered the seaplane propeller and the STC was to use the 80 inch prop on a land plane.
Just looked at the TCDS again and there is no Seaplane Propeller. Instead, they give RPM limits for a seaplane using the normal McCauley

[twlareau]

It is a great legal "loop hole"! You too can get that loop hole for $3570.00 new, plus $200.00 for the STC.

[Bruce Fenstermacher]

If there truly is no static limit I don't think its a loop hole at all. There simply is no limit in that regard.

[twlareau]

Bruce,
As usual, I agree with you. (I hope that I'm not sounding like a Bruce groupie ). My take is that the limit is max continuos power that we all know is 2700RPM. The 8043 is certainly able to go over this in cruise flight so you have to keep you eyes and ears open but my static RPM on the start of the T.O. Roll is around 2375 and rapidly increases to 2550RPM on the T.O. Roll. DA 5400' I only have some preliminary numbers so far but will update as we fly it more.

[Rosey_La_Roe]

Sorry for the miss information; the STC does not say I need to use the 8042 it was Fred at Kenmore that told me that that was the part number for the prop I needed (ie: 1A175/DM8042). Just to pick your brains a bit more... I operate my plane in the Canadian Prairies where most of my airports are around 2000' ASL. Do you think I'd be better off getting my prop twisted to an 8043, or is that more for operating out of high altitude airports (ie: >4000' ASL)?

Thanks again!

[twlareau]

If you currently own a 1A175DM8042 I would leave it alone. I think the difference would be minimal between the 8042 VS 8043. If you are going to buy one new I would probably go with the 8043 but that is just my opinion. Again, I think the difference in performance would be minimal.

[twlareau]

She sings like a choir girl on Easter Sunday.

[GAHorn]

...... I operate my plane in the Canadian Prairies where most of my airports are around 2000' ASL. Do you think I'd be better off getting my prop twisted to an 8043, or is that more for operating out of high altitude airports (ie: >4000' ASL)?

Thanks again!

A "higher" (coarser/greater) pitch of 43" will not improve field performance at higher elevations....it will DEcrease field length performance. (Higher/greater pitch = better cruise/longer takeoff runs. Lower/lesser itch = slower cruise/shorter takeoff runs. This is true regardless of elevation/altitude. Think of pitch as you do auto transmission gearing. Lower gearing = lower/flatter pitch.....and more rpm per distance travelled. HIgher gearing = higher/coarser pitch....and less rpm per distance travelled.)

I'm not sure everyone will agree but I believe the static RPM limits posted in the TCDS are minimum limits...not maximum limits....for the purpose of meeting AFM published takeoff performance. While the specific props (and pitch/rpm limits) listed are the only ones approved by aircraft type-design, the substitution of a different pitch prop of the same approved type design is not necessarily disqualifying. Re-pitching an approved prop (within the limits approved by the prop type design) is not a violation of the aircraft TCDS so long as the field-performance of the aircraft meets or exceeds published/approved data. (The AFM data is approved. The Owners Manual data, although duplicative for field-performance, is not approved data. Nor is the OM cruise performance data approved.)
However, if the field performance is degraded (for example, by increasing pitch), then an approval basis must be found.