Thorp Air Command - T18.net

Hi All,

My Thorp was fitted with an 0-320 (unsure of configuration). The previous owner sold the engine after it had a ground loop. I bought the project with a partially complete 0-360. I still need to see what comes with the engine, but it needs quite a lot.

I am trying to decide if it is best to spend the money building the 0-360 up, or selling it and buying a complete 0-320. I was keen on the 0-360 due to the extra power, but after reading your comments, I think the 0-320 would be the best engine (weight saving and economy). Suggestions?

Question: I've been trying to research the different configurations of the Lycoming, and would like to know what the best or recommended configuration is for the Thorp?

Originally I was thinking of using a constant speed prop, but now I'm leaning towards a Catto 3 bladed prop (lighter, better ground clearance, cheaper). I believe they are good performers over the Thorp's speed range. Comments?

Thanks in advance for your help... I'll definitely be asking for more help in the near future!

Regards,

Marc

Marc,
I have a T18 with an angle valve IO-360 A1A of 200hp. Sounds great, but it is heavy and makes the airplane very heavy and the stall speed is 87mph!! So touchdown is rather rapid on 5in wheels and I am at 4000ft so even faster across the ground.
In the hopes of reducing the landing speed I have a Catto 3 blade that removed 63lbs from the front together with the prop governor, removed the vacuum system for another few pounds and changed the wing tips to get a few less MPH at the threshold.
In my opinion, and I can't say too much as I am still getting it back together, and others may argue, the 0320 is the best engine for a Thorp. Weight and speed are all good and getting rid of the variable pitch prop is a good thing from a safety point of view with their history on the Thorp. Again others will start yelling and that is their opinion.
Good luck.
Speedbird 1.

_________________
N872DD
200hp Lycoming

Hi Speedbird 1,

Thanks for the insight into your aircraft. That's what I was thinking. I will be operating out of Johannesburg, so elevation is 5300ft. I'm sure the HP on an 0-320 would be sufficient.

I have a parallel valve 0-360 on my flying T-18. I stall at 63 knots and approach at 72 knots. I think you will be happy with either one. I have a T18 project as well. I'll probably go with an 0-360 on it too, but if I find an 0-320 that I just cant pass it, that's what I'll do!

Would the 0-320 B2C be a suitable engine?

If I remember correctly, the B2C doesn’t have a provision for a constant speed prop if you wanted to go that route. Otherwise 160 hp will do just fine. Mine is a B3B and I cruise 150 mph indicated behind a wood prop and no wheel pants.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

On the other hand, I was able to keep up with a 300+HP Bonanza this morning at 5000 ft. with my IO-360 burning 10.5 gph.

_________________
Bob Highley
N711SH
SN 835
KLAL

The airframe was designed to use a 125 hp O-290 and some of those claim faster speeds than mine. A little aerodynamic clean up can go a long way.

_________________
Thorp T18
O-320-B3B (160 HP)
68x74 Sterba Propeller

"The joke in aviation is, 'If you want to make a million, you'd better start with £10m.' " -Bruce Dickinson

The T18 has such a large speed range that a CSP does it the best justice. I have an old O-320 A2A out of a Cub in my T18 with a Sensenich 66WL76 prop which consistently gives me 155Kts TAS @ 9000' but I can get it into a strip that I probably would not get it out of. I pull 2100 on take off and the rpm won't start rising until I get through 75 Kts then its off like a rocket. I often fly a friends 180hp T18 with CSP and boy THAT makes a difference also has benefit in landing as well. If you are operating from a hi altitude strip then I would suggest CSP, I don't think it would matter whether O-320 or O-360.
Cheers
Tony Schischka
T18C
ZK-VMS

I don't think there is a definite, "this engine is the best for the T18". There are light T18's with the O-290 engine that are real performers and there are the 180 hp versions that are also real performers regardless of which prop is used.

I have an IO-320 with a C/S prop and I like it. It indicates 160 mph down low at 65% power. My stall speed is 67 mph and I turn final at 100 mph, approach at 90 mph and bleed the speed of so that over the numbers is is about 80-85 mph. I typically touch down between 60 and 70 mph. It floats a bit before touch down. The Trusty tail spring and Aviation Products tail wheel really improved my landings.

You need to look at what you mission profile will be and go from there. Also remember that Cubes is a great resource as far as parts go.

Regards,

Jim

Chiming in -- please see this short video showing unaccelerated stall just above 50 mph (followed by accelerated stalls just above 60):
https://youtu.be/JM-FqWQlK_U

This is N118BC, 180 hp, CS Hartzell. Awesome performance. My third T-18.

First was N6651, 180 hp, fixed pitch aluminum prop. Awesome performance (there's a theme here) -- but did not jump off the ground quite like the CS. "So what" would be a fine question to ask, and a valid one.

Anyway my second T-18 was N467JF, 160 hp, fixed pitch wood prop. Awesome perf...you get the idea. Did not blast away like the 180s, but again "so what" is a valid question. Depends what you care about most.

That said, I am in LOVE with my current power and adjustability. Get out of anywhere, then kick back and sip 9.5 GPH at 20" Hg manifold pressure and 2400 RPM, or push it to 10.5 GPH for a few (and just a few) additional mph. Typical cruise at 20.5 inches / 2400 RPM is 190 mph TAS at altitude. In fact, my typical climb, even in these summer months, with a passenger and full-ish fuel, at 25 inches / 2500 RPM, is nearly 1,500 fpm. (I am near sea level here, vicinity of Hillsboro OR.)

Last thought, something we all already know: there is no such thing as too much power.

_________________
Philip Mandel
N118BC
S/N 957
Beaverton OR

Thanks for the info and suggestions. It seems like the 0-360 is similar in weight to the 0-320 (depending on accessories). As long as I can get the 0-360 running for a reasonable price, I think I'll go with that. Catto Prop seems like a good performer, and it's much lighter and cheaper than a Hartzell CS. I still have time to decide, but that is my direction for now. I'm going to focus on getting the airframe as clean and straight as possible. I'm not really worried about the speed, but I'd prefer an aircraft that handles nicely.

Hi Guys,

Back on the subject again. I possibly have access to a Lycoming O-360 A1A. Regarding the snug fitting cowling, will this engine fit the T18 without too many hassles?

Thanks in advance.

Cheers,

Marc

My info is certainly worth what you pay for it, but I think either a 320 or a 360 will fit in the standard cowling. From what I understand, the angle valve may not fit, but either way, the angle valve 360 is too heavy to use in a Thorp anyway.

O360 is 14lbs heavier than an O320. If you add a CS prop, you will end up with 11-13lbs of lead in the tail to compensate.
If an O320 used to be in there, an O360 will fit.
The cowling will not be an issue. The mount is the same.
Cubes