Buying a C170B - need advice

[skyhopper]

Hi folks - I am a CFI from San Jose, and have 110 hours in a rented C170B. Now buying my own first C170B and need advice. Can anyone answer the following questions:

1. In what year did Cessna start installing the "lady legs" and are they better than the previous landing gear? I'd like to know everything I can about this.
2. Is it worth it to put an 80 inch seaplane prop to improve overall performance, and does mccauley still make them for the 0-300? I saw one for sale in this forum for $2200 - how much can I expect to pay for a new one if they are available?
3. Should I be wary of an O-300 engine with only 250 hrs SMOH performed in 1990, and if the cylinders were channel chromed at that time?
4. Are Cessna firewalls really made of galvanized steel? I thought all firewalls were just bare aluminum - at least thats what I've always thought the metal looked like.
5. Finally, I found 3 different C170's with 3 different Mccauley props at my home airport - the largest was 76in by 5 3/4 in wide tapered to 3 1/8in wide, and the smallest was 75 3/4 in by 5 1/2 in wide tapered to 2 inches at the tips - can anyone explain why the diversity of props, and which one is best for climb performance? A specific model number to go by would be most appreciated.

I am new to this forum, so thanks in advance to any and all who have time to offer advice.

Skyhopper

[pdb]

Hi folks - I am a CFI from San Jose, and have 110 hours in a rented C170B. Now buying my own first C170B and need advice. Can anyone answer the following questions:


2. Is it worth it to put an 80 inch seaplane prop to improve overall performance, and does mccauley still make them for the 0-300? I saw one for sale in this forum for $2200 - how much can I expect to pay for a new one if they are available?

Skyhopper

I will let the other guys handle most of the questions but with respect to the 80 inch prop, I fly one and the difference it made on short field performance was remarkable. The performance however comes at a price; the props aren't cheap and they are slow. I am lucky to get 100 mph at 2450. (I also have 850.x 6s and bubble windows which don't help for speed at all either.)

Flying with that 80 x 40 prop is like driving around in first gear all the time. Do you really need it? In America, I imagine that you have enough long paved runways that it would be a better trade for speed than short field performance. I hear about all these guys cruising at >125mph and I get jealous.

As far as the gear goes, my '53 sn 25507 has the stock factory gear, whatever it is. I have owned the plane for nearly 10 years and never felt any need to change. I know a lot of local guys swap out for 180 gear but mine seems to work just fine, regardless of the load, crosswind, or surface. I operate off field from time to time but I avoid the really rough areas and the 180 gear might make more of a difference if I were regularly operating out of very rough spots.

Personally, I think it more technique than gear but others may no doubt have a different view.

[Bruce Fenstermacher]

1. In what year did Cessna start installing the "lady legs" and are they better than the previous landing gear? I'd like to know everything I can about this.

Lady legs started in '53 with serial number 25612. I have the older gear legs and would spend the money to change them. But then I'm a good enough pilot to handle them. Seriously if I was building an aircraft I'd use the later gear but I wouldn't pass up an otherwise good 170 because it has the old gear and I wouldn't consider it a necessary upgrade item.

2. Is it worth it to put an 80 inch seaplane prop to improve overall performance, and does McCauley still make them for the 0-300? I saw one for sale in this forum for $2200 - how much can I expect to pay for a new one if they are available?

If your going to be operating out of high density altitude or very short strips then maybe. You will have to decide. It's a trade off. The normal climb props do a pretty good job unless you are pushing the envelope.
I have a semi-cruise prop at 54 inch pitch. I can nearly out climb my buddy who is running a 51 inch prop. Both of us have the stock McCauley model. Pilot technique and the weight of the aircraft can have as much to do with the aircrafts performance as hardware.

3. Should I be wary of an O-300 engine with only 250 hrs SMOH performed in 1990, and if the cylinders were channel chromed at that time?

Yes but that doesn’t mean it's a bad deal. Where has the AC been for the last 16 years and how was the 250 hours flown. 250 hours in the first year then sitting for the next 15 years or was it on average 1 hour a month for 16 years. Makes a difference. There have been plenty of engines with similar time that have been flown without problem for many hours after purchase.

4. Are Cessna firewalls really made of galvanized steel? I thought all firewalls were just bare aluminum - at least that’s what I've always thought the metal looked like.

Many aircraft including Pipers have other than aluminum firewalls.

5. Finally, I found 3 different C170's with 3 different McCauley props at my home airport - the largest was 76in by 5 3/4 in wide tapered to 3 1/8in wide, and the smallest was 75 3/4 in by 5 1/2 in wide tapered to 2 inches at the tips - can anyone explain why the diversity of props, and which one is best for climb performance? A specific model number to go by would be most appreciated.
Skyhopper

The stock McCauley prop is 76 inches. Can't say what the taper should be. If in fact there is a shorter one that prop might have been shortened slightly for damage. Hard to say. It's is extremely hard for most people to walk up to a prop on an aircraft and tell very much about it without knowing the manufacturers dimensions and how to measure them or being able to see the markings which are usually hidden under a spinner. the props could also be miss marked. It would also be hard for anyone to say from your description what prop would have better climb performance

What do the records of the plane you are looking at say the prop is?

[cessna170bdriver]

4. Are Cessna firewalls really made of galvanized steel? I thought all firewalls were just bare aluminum - at least thats what I've always thought the metal looked like.

"Aluminum firewall" is an oxymoron. Aluminum loses strength at much too low a temperature to keep fire on the engine side for any amount of time. I suspect the 170 uses galvanized (zinc coated) steel as a cost-saving measure. It's the zinc coating that gives it a similar look to aluminum.

I know of no aircraft outside the experimental category with an aluminum firewall. In fact, many aircraft have stainless steel firewalls. Even most experimental aircraft, including the RV series, have stainless steel firewalls.

Miles

[GAHorn]

Great answer from Miles on the firewall material. (And stainless will influence the compass less than steel....but as Miles said...cost...)

1. In what year did Cessna start installing the "lady legs" and are they better than the previous landing gear? I'd like to know everything I can about this.

Date/Serial already anwered very capably by Bruce. I have a slightly different opinion of the gear differences: I wouldn't spend a single dime on changing the landing gear legs on a 170 unless I were operating one with a heavier engine in the bush, in which case I'd probably opt for a 180/185 gear. I think that some preferences for the later 170 gear is largely due to cosmetics. (There is a slight dissatisfaction by some with what may appear to be a knock-kneed look to the early gear...some folks call it a "sagging" look, while some refer to the later gear as a "bowlegged" look. Both descriptions seem derogatory to me, and carry inferences that far outweigh any true differences. Neither are any better than the other to a proficient pilot, IMHO.)

3. Should I be wary of an O-300 engine with only 250 hrs SMOH performed in 1990, and if the cylinders were channel chromed at that time?

If you have the choice between two otherwise identical engines that have sat around a lot without flying....pick the one with the channel-chrome cylinders. They'll have a lot less rust in the upper cylinders. (One of the big advantages to channel-chrome.) Of course, a tradeoff might be if the other isn't really identical and has been sitting around with new cylinders.... after all...how many times have the channel chromes been reused? Hard to make apples/to/apples comparisons on such things, because apples/apples comparisons actually never exist. No such thing.)
Inspect the airplane/engine before buying it using an annual inspection. You get what you pays for.

5. Finally, I found 3 different C170's with 3 different Mccauley props at my home airport - the largest was 76in by 5 3/4 in wide tapered to 3 1/8in wide, and the smallest was 75 3/4 in by 5 1/2 in wide tapered to 2 inches at the tips - can anyone explain why the diversity of props, and which one is best for climb performance? A specific model number to go by would be most appreciated.

Get a copy of the aircraft type certificate data sheet and read it, (available to Members at the Members Only page of this website) and compare it to the subject aircraft, making certain that any deviations from the type certificate are documented and approved alterations. The actual measurements of any installed propeller may deviate slightly from other examples due to many reasons, but some possibilities are: Props can be altered due to overhaul, damage/repair, time in service, and even varying model numbers between approved prop designs. Again, read the type certificate and you'll see there are numerous props that are approved for this aircraft. Which one is actually installed on the subject aircraft? Which is installed on the comparable aircraft? Has either one been subsequently overhauled to different dimensions? etc etc.
Props can be priced at http://aircraftspruce.com/ online catalog. New props can run $3500-$7500, but it's unlikley you'll need to spend that.
As for which model to go with???...go with the one already installed. You're not shopping at the Cessna factory for a new airplane that you will be specifying new equipment for. You are shopping the used market for, and among, airplanes made over 50 years ago. Virtually none of them are equally equipped, modified, or maintained. We all likely settle for the best example at the best comparative price we can find nearby, and then some of us spend money changing it as we can afford....and others of us spend money UNmodifying it (returning it to it's originality) as we can afford.

Welcome to our group! Join our Association on the Home page!

[Tom Downey]

The Firewall on the 170/172 are made from a Cessna material, that was alclad steel.

That is why we see so many firewalls showing rust. thru the alclad.

[cessna170bdriver]

The Firewall on the 170/172 are made from a Cessna material, that was alclad steel.

That is why we see so many firewalls showing rust. thru the alclad.

Thanks for the clarification, Tom. I stand corrected! The reason they look like aluminum is that the outer surface IS aluminum. DUH!

Miles

[GAHorn]

Actually, it's called "Galvalume" (which is a trademark name.)