Converting a 180HP 172S to a 160HP?

bimmerphile said:
Why? Unless there's a ridiculous cost savings that makes a difference in your fuel consumption, I can't imagine it would help your resale at all. People would just by an R model instead
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by the time I"m done with the plane there wont be much resale value left in it. The previous school I flew at had 20,000+ hours on the airframe on more than one of their planes.
 
bimmerphile said:
Rent it dry?
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One of the flight schools here does that. The field sells fuel wholesale (you join a Fuel Club for $18 a month) and you get the airplanes at a dry rate - you just fill up the airplane after your rental. Convenient.
 
bimmerphile said:
Rent it dry?
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NEVER run a rental plane dry. What you might sell on fuel will be spent on cylinders and valves.


trafficinsight said:
12 is too much for the 180 I think, you should be able to flight plan it conservatively at 10.
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For a normal training flight, you can plan on 8-9 tips due to a lot of idle time, 1-1.5hr sorties with taxi time, and low power/non-cruise settings.


If you’re looks long term—Thielert/Continental diesel STC. The upfront cost is heavy, but your burn would be about 50-60% of the Lycoming.
 
Roger Roger said:
You could always file for a field approval on the basis of the OEM 160HP install.
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It's been a long time since I looked into it, but can't an IA do a model change based on the aircraft being in compliance with the TCDS? I didn't think a 337 was even needed, just a logbook entry ...
Or is that only if there's a service letter detailing the model change?
 
Urp99 said:
It's been a long time since I looked into it, but can't an IA do a model change based on the aircraft being in compliance with the TCDS? I didn't think a 337 was even needed, just a logbook entry ...
Or is that only if there's a service letter detailing the model change?
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Not with airframes.

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Urp99 said:
It's been a long time since I looked into it, but can't an IA do a model change based on the aircraft being in compliance with the TCDS? I didn't think a 337 was even needed, just a logbook entry ...
Or is that only if there's a service letter detailing the model change?
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Only if the TCDS lists multiple different engine options under one subtype. Like with some of the old pipers, there is a number of different engine options that fall under one type on the TCDS. Changing between engines listed on the TCDS is a minor alteration. In the case of (I assume) the 180HP 172S going to the 160HP 172R setup, the two are listed separately on the TCDS and you need some other form of approved data (field approval, STC, etc) to do the swap. Clear as mud?
 
trafficinsight said:
Dry rental is how you get cooked cylinders... And fuel exhaustion accidents.

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Hmm. The place I referenced above experiences neither of those things, so they're doing something right. The dry-rate rental program with the fuel club works very well for these folks, and the flight school is owned by an A&P who takes very good care of the fleet. <shrug> Don't know what to say.
 
Roger Roger said:
Only if the TCDS lists multiple different engine options under one subtype. Like with some of the old pipers, there is a number of different engine options that fall under one type on the TCDS. Changing between engines listed on the TCDS is a minor alteration. In the case of (I assume) the 180HP 172S going to the 160HP 172R setup, the two are listed separately on the TCDS and you need some other form of approved data (field approval, STC, etc) to do the swap. Clear as mud?
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Ah, that makes sense. I knew an IA could do a model change with a logbook entry, just couldn't remember the particulars involved, I never actually did it myself. I'm sure you're right about the R and S models being listed separately, the FAA isn't as lenient with the manufacturers putting everything under one broad TCDS anymore.
I used to work for an aerial applicator that changed the model designation on several Air Tractors while upgrading them to turbines, but in that case Air Tractor had issued service letters detailing exactly how to do it.
 
The only experience I have in a situation like this was trying to help a friend convert a C-175 (basically a C-172 with a 175 hp geared GO-300 engine) to a C-172. The geared engine is notorious for maintenance issues, and a non-geared O-300 is cheaper, and basically bolt right in with only a nose bowl change as I recall. Anyway, it only took one phone call to the FAA to shut that idea down, we were told that even though we would be creating a C-172 there was absolutely, positively, no way that they would sign off on installing a smaller engine than an airframe had originally.
This is in the Midwest where homebuilding and major alterations aren't extremely common, and that was one guy at the FSDO, so it may not be FAA policy, but if there's no manufacturer service letter or STC approving the change I would start with the FAA and see if it's something they'd even consider.
 
Urp99 said:
The only experience I have in a situation like this was trying to help a friend convert a C-175 (basically a C-172 with a 175 hp geared GO-300 engine) to a C-172. The geared engine is notorious for maintenance issues, and a non-geared O-300 is cheaper, and basically bolt right in with only a nose bowl change as I recall. Anyway, it only took one phone call to the FAA to shut that idea down, we were told that even though we would be creating a C-172 there was absolutely, positively, no way that they would sign off on installing a smaller engine than an airframe had originally.
This is in the Midwest where homebuilding and major alterations aren't extremely common, and that was one guy at the FSDO, so it may not be FAA policy, but if there's no manufacturer service letter or STC approving the change I would start with the FAA and see if it's something they'd even consider.
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That’s a bit of a different animal because IIRC the 175 is a whole different TC than the 172.
 
Roger Roger said:
That’s a bit of a different animal because IIRC the 175 is a whole different TC than the 172.
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This is true, but we never got that far in the conversation, it was their stance that that they wouldn't allow us to go down in hp. But, like I said, major alterations, modifications, and STC development isn't something that's done often around here, so it's not our FSDO's strong point. A person might have better luck with a different FSDO.
 
Urp99 said:
The only experience I have in a situation like this was trying to help a friend convert a C-175 (basically a C-172 with a 175 hp geared GO-300 engine) to a C-172. The geared engine is notorious for maintenance issues, and a non-geared O-300 is cheaper, and basically bolt right in with only a nose bowl change as I recall. Anyway, it only took one phone call to the FAA to shut that idea down, we were told that even though we would be creating a C-172 there was absolutely, positively, no way that they would sign off on installing a smaller engine than an airframe had originally.
This is in the Midwest where homebuilding and major alterations aren't extremely common, and that was one guy at the FSDO, so it may not be FAA policy, but if there's no manufacturer service letter or STC approving the change I would start with the FAA and see if it's something they'd even consider.
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The Penn Yan or Air Plains 180hp STC is applicable to the 175, you'd replace the GO-300 with an O-360.



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