Thorp Air Command - T18.net

I like the format of Hagle347's project updates and found them very helpful for a newbie, so I'll introduce my new project in a similar way and hope my notes can help future newbies. Thanks, Terry...

I acquired T-18 S/N 79 in late August. I'm going to keep it's original N number of 12055 - the airplane was originally built by Robert Kaergard in Chicago. The date of first flight is not known, but the builder applied for the first certificate of airworthiness in October, 1965.

Mr. Kaergard and/or his aircraft have been mentioned several times in the old newsletters and if anyone can relate the history of the aircraft to me, I'd appreciate it. I believe that Mr. Kaergard gave a demonstration at Rockford(?) on converting an open-cockpit Thorp to the present-day configuration. I'm wondering if 12055 was used for that purpose if anyone knows. I hope the builder is still alive and I get a chance to meet him.

I saw N12055 at my EAA Chapter 45 picnic. Saw it on a Sunday and bought it the next day. It hadn't flown in approximately 12 years. Always hanger-kept. There is only one small dent on the aircraft after 50 years. It has 193 hours on the tach with an O-290D on the front. We bore-scoped the cylinders and they were in amazing condition. Don't know about the cam yet. I am changing the oil this weekend and send it off for analysis. I plan on starting the engine in January.

My EAA buddies helped me tear it down and drag it home. Since it's arrival, I've been replacing rubber things and finding out that little things that should move - like a fuel selector valve - didn't move at all. So the replacement process began.

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John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)

Very nice shop for "the comeback"
You're welcome- enjoy the journey

Welcome to the Thorp Family. You could not have chosen better! We all look forward to your posts.
Steve Hawley

More detail: N12055 has, as best I can tell, a standard wing. It is set up for day VFR with no landing light or instrument lights. Basic instrumentation is used and I will keep the steam gauges for now until I get some experience flying a tailwheel aircraft and this one in particular. After that, I'll convert N12055 to EFIS over another winter.

I've begun to change out what is there to newer instruments that I had hanging around. For newbies, I found out that all tubing needs inspected and that you can't assume it's flight worthy. For example, there was a damaged pitot line (very flexible and rubbery) that I couldn't see until I removed the old instrument.

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John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)

This is the fuel setup in N12055. Shutoff valve, then Tee, then a hard line through a 90 degree bend to the firewall. The hard line seems awfully close to the passenger's left foot. I'm wondering if replacing the hard fuel line with a flexible fuel line is safer. Any thoughts?

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John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)

After looking at your photos, it is a "standard wing". As far as the fuel line- it appears you have plenty of clearance. The line looks to stay behind the fuel tank support. If you are really concerned- make it a briefing item for passengers. Remember, you can always find items to replace that aren't 'broke'.

I think I read somewhere in the newsletters that mounting the fuel valve directly to the fuel tank causes stress on the fuel tank, The suggestion was to mount the fuel valve to the airframe and have a flexible fuel line going to the fuel tank, i'm also a newbie so I could be totally wrong, maybe One of the senior members could chime in,
Thanks for sharing your project

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John Letkeman
N2562K SN.922
Seminole Tx
(KGNC)

And yet...the photos show no such issues on the fuel tank bung. The hard tube helps support the valve and in all its years, it appears there have been no issues.

John,
I believe you are correct about the newsletters and yet my aircraft has been flying for 45 years and 1500+ hours with the fuel valve hanging from the bottom of the tank like yours. The only difference is that I have a hose from the valve to the firewall instead of a hard line.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

Thanks for the thoughtful replies. Merry Christmas, by the way!
Terry - yes, the fuel line is in line with the tank support, and making it a briefing items sounds great. Glad to hear that there have been no apparent issues in all these years.
John L - I saw the newsletter or forum item too. No evidence of a torque-induced leak here, but the previous owner did talk about a very small chronic leak somewhere (no one quite remembers where it exactly it was), so I'll keep an eye out for it here. Are you flying or working on a project?
Bruce - did you decide to go the hose route out of the same concern or are there other concerns too? Congrats on having 1500+ hours on your plane

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John Twigg N12055 SN.79 Pittsburgh, PA (KFWQ)

Bruce, that makes a lot of sense, I've seen a lot of Thorps, including mine that have the fuel valve attached directly to the fuel tank,
John T, I discovered metal in oil during conditioning inspection and now I have the engine tore apart I have already overhauled the cylinders since I have a friend with all the equipment to do it, I know I need a new cam, I think crank is ok,

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John Letkeman
N2562K SN.922
Seminole Tx
(KGNC)

On the picture of the fuel valve, it looks like fuel may have been leaking from the joint between the blue anodized fitting and the brass "t" (the right side of the t). It looks like fuel stains where it has been dripping. Don't see any sealer on those particular threads also.


I would just get rid of the heavy brass t and make a new hard line that goes all the way from the firewall to the valve. Don't know if you are gravity feed fuel, but if so, getting rid of the brass t would also eliminate some fuel flow restriction as a side benefit.

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Bernie Fried
N18XS

John T,
That is the way the aircraft was when I purchased it, I've only flown it 350 of the 1542 total hours.

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Bruce Finney
N18JF T-18C #262
Yelm, WA USA

I suppose the brass T is so you can fish out your jewelry or remove a nasty hair clog !

RB

My valve (a relatively light brass 1/4" NPT ball valve obtained from ACE Hardware), has been attached directly to my tank for 25 years with absolutely no problems. Coming out of the valve is an AN6 (3/8") 90 deg. aluminum elbow, with a short piece of Teflon-lined S.S. braided hose going directly forward through the firewall and into my gascolator via another 90 deg. ell. I am completely gravity flow with a 160 HP O-320. I think it's quite possible in some cases that builders who had problems with hanging valves directly on the tank used heavier valves &/or indirectly routed or looped their tubing coming off the valve, perhaps with the misconception that they were providing flexibility to take strain off the valve/tank junction. That can allow vibration to occur that wouldn't be there if the valve was more rigidly connected to & supported by the firewall. The center area of the firewall & the tank are pretty rigidly stable in relation to each other. That's just my 2 cents worth.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE