Thorp Air Command - T18.net

G'day Thorpers
Got a fuel gauge problem(not working) I'm running a JPI 450 but the gauge must be operable. Looking around from underneath I can't see the location of the sender, and can't locate the Tank Drawing in my set of drawings. This week I'll have to take the dash out and see if I can locate it as I suspect that is the problem.
I'm asking 2 questions 1. What is the tank drawing No. ?
2. Where is the plan location of the tank sender unit ?
To change the sender, have you any hints for a headache free sender change

Appreciated
Good onya
John Groth VH IXI

I don't have access to the plans now, but can tell you some information. The location is on the top of the tank, slightly left of center and about midway along the top deck. If you don't have an access opening on the deck I think you'll have to remove the tank. I'm sure that will be no fun. I had to change my sending unit last year and was mighty glad that I made a access opening above the sender. The original sender lasted 25 years. Probably a lot of Thorps never have to replace them.

JIm

N180RG

I'm in the same situation.
I checked the builder's aircraft manual, and ordered the Stewart Warner sender from SummitRacing's aerospace depatment It's on order with a 90 day back log. I guess they don't get much call for the adjustable float model.
I'll be making that access opening above the tank. This is a part that will require maintenance from time to time.

I too used a stewart warner sender and fuel gauge. I found out thru Dick Ecklund what the part number was and went to a local stewart warner distributor in the Minneapolis area. They had it in stock so was able to install it same day. I don't know if you have the same gauge and sender or not. I don't remember who I bought it from but it was a common choice amongst T-18s at the time. I'll be back at my hangar early next week and would gladly research it more for part numbers if you like.

Jim

I just got home and checked my manual;
The Stewart Warner adjustable fuel sender in my plane is part # D-391-B '240 Ohm, 10-15" RH'
I see some on fleabay right now, but the # has been changed to 391-BF in the current SW online catalog.
PS; I just rechecked that 391-BF online, and a fleabay vendor has it $29.95 + 9.95 shipping (gag!). Looks like I could have had it by now if I went this route.

Thanks for the swift replies. I've borrowed a Borescope, so with the dash out I should be able to get in and get the exact location of the Sender. Looks like an access panel in the deck coming up. Don't fancy dropping the tank. I'm sure I've seen the Tank Drawings somewhere but can't remember where.
I've got two things wrong with me, one's Alhiemers and I can't remember the other one !!!!
I'll update

John Groth IXI

John
The standard T18 plans drawing 792 shows the sender centred 4.25" to the left of the centreline and from my quick rough measure it looks to be approximately 9.25" back from the front of the tank.
Looking at sensors have a look at this website http://www.gillsensors.co.uk they have a range of solid state, no moving parts fuel level sensors which look good. I think you would need one 480mm long to do the job. No doubt it would be expensive but would probably never need replacing.
Stuart

I don't know if either of you got into disassembly yet. The stewart warners that I dealt with had to be split into two pieces to get in and out of the tank. The lower portion of the sender had to be fished thru the tank filler opening and then assembled to the top portion. Two screws are involved with this procedure and they are the same screws that adjust the float height. Also a resistance wire had to split and then re-spliced after assembly. Sounds a little cumbersome but actually not that bad. Good luck.


JIm

If you don't have an access hole on top of the skin over the sender, do it if you have to take the tank out ! I have the "solid state" sender that you can calibrate. I calibrated it out of the tank according to the istructions and found that when it was installed in the tank it still required a little tweaking. That would not have been possible without the access panel. The gauge it within 1/2 gallon of being accurate and this has been x-checked with the newly installed fuel flow computer.

RB

Here is my suggestion John,

Richard Bentley had the same situation with his fuel sending unit and with very little coaching he managed to do a great job. If you can take the glare shield out without pulling the instrument panel, using a mirrow, get a rough measurement of where the sender is just left of landing gear beam at upper deck. Getting as close to the center between it and stiffener to the left and near the F.S. location where you believe the sensor may be, drill a 1/4" maybe 5/16" hole and peek to see if you can determine as close as possible the center of the sensor. Once there, you can enlarge the hole gradually until you get to the size you need to disconnect and pull the sensor out without getting the hole too large, then cut you a doubler plate to beef up the skin when putting it back together and make a cover to go over it or in it, whichever way you'd like. Email Richard and he'll tell you just how he did it.

You may have to cut and splice the wires to the sensor. As far a sensors are concerned, I use a Capacitance type which has no moving mechanism and go straight down to within 1/4" from bottom of tank. Mine was 24" long and I had to cut it to fit. They come with instruction. The gauge must be compatable with the sensor or it won't work. Another problem with capacitance type sensors is that if moisture gets inside, it'll act as if it was shorted out and read "Zero" (empty). It can be taken out, dried and put back in if it does.

Hope this help.

In CowTown USA,
Don D-Day

Thanks Fellas
I can't get to the Hanger 'til the weekend. I'll try the borescope before I start drilling holes. I found Drawing 514 but it only shows the filler/vent and outlet. You blokes have put my on the track of the position that's half the battle( I hope).
Thanks again

John Groth IXI

I was curious about that Gil fuel gauge sender and got some information to share. it looks like it would neatly drop in place of the stewart-warner sender but boy is it expensive, near on twice the price. Then add on some for a new gauge to match it.

Cheers
Stuart

When you buy gauges that require a sender, buy them as a matched set. Especially the fuel tank, if you do not have access to the sender once the tank is installed.

RB

John,

Get your fuel probe issue taken care of yet? The setup I have is 10-00040 UMA 1-1/4 FUEL QTY IND. CAPAC. $135.950
10-01262 WESTACH FUEL SENDER $ 98.50

The system is not cheap, but works good for me. The probe has no moving part, the element is aluminum as the center conductor as well separated by taflon sleeves to prevent shorting and has "0" and "Full" calibration screws. Believe I saw the post from Rick B. where he mentioned buying as a match set. That would help, but not necessary, just make sure when buying the gauge, to let them know what type sending unit you'll be using so the gauge can be calibrated to that probe. The probe I have is 0-5 ohms.

D-Day

Having been down that road trying to "match" guages with other senders...even though they say they work with them I have found spending the few extra bucks and get the "matched set !" I spent hours trying to get a fuel pressure guage from UMA to work with a VDO sender that was listed as to work. In the end I bought a matched Westach fuel pressure gauge and sender. It worked the first time ! I guess if you have the electrical knowledge to pair up a mis matched set of guages and senders, then press ahead !

RB