Thorp Air Command - T18.net

Bill Williams posted that he has an HA-6 carb on his T-18.
I want to know about it, but didn't want to highjack that other thread.
So Bill, (or anyone else running an HA-6) how do you like it, how did you mount it (front or back) what kind of air filter, etc?
I got a rear entry sump, and a Rotec TBI, but I see the engine mount tubes would interfere with a carb, so I haven't done anything further with it.
AN HA-6 seems (to me) more reliable than a TBI unit...

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

What reliability issues are you having? I have been interested in the rotec as a cheaper, more updated replacement to my carb issues. David Read uses the rotec (i'm pretty sure it's a rotec brand). To my knowledge when I asked him last he hasn't run into any issues and he has a really nice flying t18 with a smooth engine.

I'm sorry. I don't mean to be-little the Rotec TBI. My son Peter put one on his RV-4 along with a Christen oil system so he could fly inverted. He now competes in IAC aerobatics.
The Rotec never gave him any problems and I also flew the plane with no problems.
I bought one because of Peter's experience. I may yet install it.
There are posts over on Vansairforce site about Rotec TBI and Ellison TBI success stories and problems. I think some of the problems stem from owners experiencing leaning at full throttle, with TBI units that are a bit too big for the engine application. Lots of discussion about limiting maximum throttle opening, or drilling additional or larger holes in the spray bar.
Other problems relate to how the air enters the TBI unit (turbulent / laminar) axis of orientation to the engine (slide for&aft or crosswise) All of these could be regular carb issues when one puts on a new type.
Some posts seem like the usual noise of the disgruntled, or don't understand. There are a few complaints of poor product workmanship. One can never sell a product without unhappy customers, so where would one draw the line?
There is some discussion about wear in the slide and the spray bar seal over time. None of these negative issues has been experienced by me.
I ask about the HA-6 because it is an FAA certified carb, which should mean it is pretty reliable and has continuous follow-up for service problems. HA-6 has been successfully employed on O-320 and O-360 Lycomings. I am curious about the HA-6 as a way to remove the updraft sump and shave off the chin scoop on my T-18.
If there is a simple way to modify the engine mount for rear draft, would the HA-6 carb be low enough, and close enough to the fuel tank for gravity feed?
So many questions...

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Ah, that makes sense.

Well, if you decide in the near future to sell it I might be in the market for it.

I know David Read's system has his rotec on it's side so he has a rear-draft intake and the cowl cut down in the front. He had to do a little more work to get it there but the install looks great and has been working just fine for him.

Bob and I both ran HA6's for years until he converted to fuel infection.
My engine is a 0-360 A1G which is manufactured that way with a rear mounted carb.
I used an Piper Arrow, Twin Comanche style air box, if memory serves me the filter is a Dodge V8. This setup allows for little room between the engine and firewall.
Some guys use an X_XXX A1A engine (updraft) and using a 90* elbow and mount the HA6 which gives you more room. You also don't need a different sump.
I think Ron Hayes has this setup. I think Precision makes a 90 or buy a SS 90 and make your own

Scott, I have been flying with the HA-6 for nearly 39 years. There are two types of that model. The leaning mechanism on the first was a rotary type that MS could not stop from leaking. The later model has a plunger type and is much superior. Both types require about .6 psi at the inlet and that is not
possible with gravity feed. I run a mechanical pump and an automotive type electric one. The reason was to keep from cutting my beautiful new aluminum John Thorp cowl. I would post some pictures of how I hooked it all up don’t know how. Another unusual thing, I have been flying all these years with no carburetor heat! I just use the hot air for the engine cooling for the heat. There is a butter fly valve to select cool ram air or the hot engine cooling air. There is no room behind the air box to install a hot air duct system. I have a dry air filter about 3” diameter and about 6” long behind cylinder #3. I did extensive testing to be sure there was no drop in manifold pressure due to the air filter. I have flown the system 1400+ hours with no problems.

Tomorrow morning I leave for KY Dam!

Steve Hawley

I ran the Rotec for most of a year with no serious problems. Early this spring when I was trying to get a problem solved that ended up requiring cylinder overhauls I didn't think it was running quite right so I had them take it back to bench check it after sun & fun while we flew to the Bahamas on the original updraft carb. One of the main things I remember they said they did was enlarge the holes in the spray bar. It is still in the box on the shelf, I didn't want to mess with a combination that seems to be trouble free, at least for now. I also have an HA-6 that i am debating on putting on so I can eliminate having the bottom of the cowl too low for carb clearance, I just haven't committed to anything yet.