I'm considering a 172 with the Avcon 180 & Hartzell conversion. It doesn't have a gross weight increase STC, so the plane has ~100bs less useful load.

Anyone know if there's a gross weight increase STC that can be added to this plane? From Avcon or someone else?

Any comments on the performance of this conversion? Is it worth the little extra fuel and the costs of dealing with a CS prop?

Thanks.

I have a 56 172 with an Avcon conversion, and no on the weight increase for the 172, at least in my search. The Hartzell I am planning on losing as soon as possible, 7 years of paying eddy-current AD checks and I could have just about bought a real prop.

As far as performance, I can only compare it to a 56 172 with the stock C-145, which is not any comparison. It is nose heavy, but at sea level I can get an honest 1500 fpm climb and cruse 105 kts at 9gph. 6000 ft I can still get 700 fpm, 110 kts at 8 gph. 10000 I get 500 fpm and 115 kts at 6.5gph. Not exact, but what I have seen as average over the years. The advantage I have found is at the higher altitudes, courser pitch allows higher cruse and less fuel consumption, which is working out really well here in Utah, not so much when I lived in Alaska and did most of my flights below 1000 ft.

Chris

If you go with wing extensions from ART you get 200 lb gross increase with the combination of the wingX and the 180 hp.

A1Skinner wrote:If you go with wing extensions from ART you get 200 lb gross increase with the combination of the wingX and the 180 hp.

That's only in Canada, the STC still hasn't been approved in the US.

OK. Good to know Rob.

Unga

According to my years of listening to Harry Delicker at Del-Air in Porterville, the weight increase could only be used on the later 172s that have a "step" on the top of the firewall, but not on the early ones with a FLAT firewall like the 170. I do not remember why.

The Chris that inherited the business may be able to tell you why. Del Air also sells a conversion similar to, if not the same, as Avcon so he might be able to tell you why. He is also the one that rebuilt a prize wining rebuild of a classic 170.

I had the old original BUSH 1180 hp. conversion on mine and it took me three prop changes to end up with the MT. Lost 29lbs off the nose. That was after taking off the Hartzell 80 inch with 14Lb dynamic balancer needed to run at all rpms. Mine originally came with a label limiting operations from around 1800 to 2100 rpm.

Hope that helps

Chris C N4036C

robw56 wrote:

A1Skinner wrote:If you go with wing extensions from ART you get 200 lb gross increase with the combination of the wingX and the 180 hp.

That's only in Canada, the STC still hasn't been approved in the US.

Exactly, I keep hoping though. I check the wingex site from time to time to see if it finally gets approved.

slowhawk wrote:I have a 56 172 with an Avcon conversion, and no on the weight increase for the 172, at least in my search. The Hartzell I am planning on losing as soon as possible, 7 years of paying eddy-current AD checks and I could have just about bought a real prop.

As far as performance, I can only compare it to a 56 172 with the stock C-145, which is not any comparison. It is nose heavy, but at sea level I can get an honest 1500 fpm climb and cruse 105 kts at 9gph. 6000 ft I can still get 700 fpm, 110 kts at 8 gph. 10000 I get 500 fpm and 115 kts at 6.5gph. Not exact, but what I have seen as average over the years. The advantage I have found is at the higher altitudes, courser pitch allows higher cruse and less fuel consumption, which is working out really well here in Utah, not so much when I lived in Alaska and did most of my flights below 1000 ft.

Chris

I did know about the eddy current AD check, but have no idea what those cost. I'm leaning more and more away from this plane, as I'm looking for something simple as a first plane. The 180 conversion with the CS prop sounded good, but I'm not sure if I want to deal with the extra headaches yet. $10-15K to install a MT prop sure buys a lot of gas.

Thanks for the info.

There is the cost 250.00 - 500.00 annually for the test, and the hassle factor. Since I have mostly lived in the hinter-lands, it's usually a several hour trip to somewhere to get it done and getting harder to find places to do it. It takes longer to take the spinner off/replace than it does for the test, just so hartzell can cover their ass.

Going MT as soon as I can afford it.

An IA in Fairbanks got field approvals for some model years of 172 with the 180 added. He did the research and was able to demonstrate to the FAA that the structures were identical to later models with the higher gross.

Someone at Cessna may know more about it.

MTV

My P172D has the Avcon conversion but with a McCauley prop. When it finally needs overhauling, it will have to be replaced, as the parts for an overhaul aren't available, according to my IA. He has done some preliminary looking at other props, but nothing definitive yet--and not necessary yet. When it started leaking about 3 years ago, we let it go until annual before last, and a local prop shop was able to get the necessary seals to reseal it. It still works fine. Other than the occasional dressing of the blades at annual time, that's the only maintenance the prop has required.

As for performance, the lowest elevation I've flown it out of is Tulsa at just over 600' and OSH at 800', and even with a full load, it climbs like a scalded cat at those low elevations. At my home dromes (Greeley at 4700' and Fort Collins/Loveland at 5000'), it outclimbs any stock 180hp 172 and will almost keep up with an XP in the climb. For cruise, I flight plan for 115 knots at 8000' or 9000', which ends up very, very close in a 3 hour leg--that's about 10 knots faster than a 180hp 172 with a standard fixed pitch prop, and almost as quick as an XP. That's with the super droopy tips which add drag and the flap gap seals which reduce drag--I think they pretty much cancel each other out.

The highest I've flown it is 15,000', but that's really a stretch. It's pretty comfortable at 14,000', although it takes awhile to get there on "normal" days. When I took off from Leadville (9934' MSL) about 5 1/2 years ago, the ground temp was about 75F, the DA was 12,100', and my climb rate was between 150 and 200 fpm. On that very warm day, it topped out at 12,300' MSL, although I might have been able to eke out a tiny bit more. I had a relatively light load of just me, puppy dog, and survival equipment, and about 38-40 gallons of gas when I left Leadville.

Fuel burn at cruise is 9.8 or a little less, depending on how carefully I lean using my Insight G1. Much under that, it peaks out and starts running a little rough--can't run lean of peak, although I've tried as an experiment by adding carb heat, which does even out the cylinders but still doesn't allow running LOP. All that is with 2400 rpm and 21" MP (decreasing MP with altitude, of course). I've tried different combinations of rpm and MP, but that works out the best, and the engine seems "happy" at 2400 rpm, whereas much slower and it seems to be lugging--although that's just my subjective view.

For me, the only downside has been that the back 2 cylinders tend to run warmer than I'd like, going over 410 in the climb. They cool down to under 400 in cruise except on very warm days, when I have to run with the cowl flaps partially open to keep them to 400.

For my IA, the downside has been the absolute lack of customer support from Avcon. If he leaves a message on their voice mail, they don't respond. If he talks to the Mrs. live, she says the Mr. is out and will call, and he never does. And they don't respond to email--not sure if they even have it. The big question he had was something about the engine mounts some 10-11 years ago, but there are enough Avcon conversions out there, so that my IA was able to confer with other mechanics to determine what could be done.

To answer your main question: My airplane came from the factory with a 2500# gross, but the Avcon conversion actually reduced that to 2350#. So far as I know, there are no STCs approved by the FAA which allow it to be returned to the original 2500#, or to increase it on mine or any other 172. That makes it a 3 person airplane except with a light fuel load, such as just under half tanks.

If you're ever out this way, I'd be happy to take you up in it.

Cary