Fuel guage repair

How to keep the Cessna 170 flying and airworthy.

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Re: Fuel guage repair

Postby minton » Wed Aug 04, 2010 1:19 am

I think that the original guages were "Scott" and not truely a "Cessna" mfg.
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Re: Fuel guage repair

Postby gahorn » Wed Aug 04, 2010 3:43 am

In reference to all the concern regarding "approved" fuel gauges and parts: This summer's convention mx seminar was addressed by Rick Anderson, DTO-FSDO who spoke at length regarding replacement parts for aircraft type certificated prior to Jan 1980. In a nutshell: buy the darn parts and install them. Log it, and record the source. Be happy. You're legal.
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Re: Fuel guage repair

Postby N2255D » Wed Aug 04, 2010 4:07 am

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Re: Fuel guage repair

Postby lowNslow » Wed Aug 04, 2010 4:59 pm

Bikini wrote:gahorn,
did you have to modify your guage at all for it to work in a 170? There's a whole discussion about having to shorten the arm or something. or is the Spruce product fit our plane?

Bill

To answer your question - yes the Spruce gauge works fine. The gauge comes with a long straight float arm so that it can be adapted to different tanks. You will have to shorten the arm and bend the end 90 degrees to attach the float so that it is horizontal and parallel to the bottom of the tank. The gearing is different than the original gauge so that the arm will swing about 150 degrees from "full" to "empty", on the original gauge the arm swings about 35-45 degrees. I don't remember the exact measurements but you can figure it out by measuring the inside depth of your tank.
Karl
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Re: Fuel guage repair

Postby Bikini » Wed Aug 04, 2010 10:33 pm

gahorn wrote:In reference to all the concern regarding "approved" fuel gauges and parts: This summer's convention mx seminar was addressed by Rick Anderson, CHI-FSDO who spoke at length regarding replacement parts for aircraft type certificated prior to Jan 1980. In a nutshell: buy the darn parts and install them. Log it, and record the source. Be happy. You're legal.



Can an owner do this or do I need to
Convince my A&P??
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Re: Fuel guage repair

Postby Bruce Fenstermacher » Wed Aug 04, 2010 10:57 pm

You need to convince your A&P to supervise your work.
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Re: Fuel guage repair

Postby mit » Thu Aug 05, 2010 1:33 am

gahorn wrote:In reference to all the concern regarding "approved" fuel gauges and parts: This summer's convention mx seminar was addressed by Rick Anderson, CHI-FSDO who spoke at length regarding replacement parts for aircraft type certificated prior to Jan 1980. In a nutshell: buy the darn parts and install them. Log it, and record the source. Be happy. You're legal.



That's good to hear, did he put it in writing?
Tim
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Re: Fuel guage repair

Postby Bruce Fenstermacher » Thu Aug 05, 2010 1:56 am

I think George's statement is pretty general. AC 23-27 spells out some specific things that can be substituted and general guide lines for others. It appears by this AC that the FAA is taking a bit more logical look at some of these parts and agreeing that if it looks like a duck, flies like a duck and quacks like a duck, it just might be a duck. That was the message from Rick Anderson who is a Cessna 175 owner himself.

If only more FAA folks fell in line with what Anderson was preaching.
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Re: Fuel guage repair

Postby gahorn » Thu Aug 05, 2010 2:15 pm

mit wrote:...That's good to hear, did he put it in writing?


He utilized a Powerpoint presentation which provided references to FAA legal opinions and Advisory Circulars.

When I asked for a written opinion on particular issues he answered that written opinions will be provided in response to written inquiries. (Sensible and correct response.)
'53 B-model N146YS SN:25713
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Re: Fuel guage repair

Postby mit » Fri Aug 06, 2010 1:01 am

Then did you get a copy of the Power point and his talk on tape?
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Re: Fuel guage repair

Postby gahorn » Fri Aug 06, 2010 9:30 pm

mit wrote:Then did you get a copy of the Power point and his talk on tape?


There's no reason to belabor the point... if you want a copy, then get in touch with him, he's an inspector at DTO-FSDO, name Rick Anderson. Easy to find. (and it was an FSDO-produced presentation based upon an FAA Advisory Circular available on line, a copy posted above.)

Errata: Corrected FSDO to Detroit.
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Re: Fuel guage repair

Postby iowa » Tue Jan 07, 2020 2:30 pm

is this the best thread on how to replace/overhaul a gas gauge?
thanks
dave
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1942 L-4B 2764C USAAC 43-572 (9433)
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Re: Fuel guage repair

Postby dstates » Fri Feb 28, 2020 1:04 am

lowNslow wrote:
Bikini wrote:gahorn,
did you have to modify your guage at all for it to work in a 170? There's a whole discussion about having to shorten the arm or something. or is the Spruce product fit our plane?

Bill

To answer your question - yes the Spruce gauge works fine. The gauge comes with a long straight float arm so that it can be adapted to different tanks. You will have to shorten the arm and bend the end 90 degrees to attach the float so that it is horizontal and parallel to the bottom of the tank. The gearing is different than the original gauge so that the arm will swing about 150 degrees from "full" to "empty", on the original gauge the arm swings about 35-45 degrees. I don't remember the exact measurements but you can figure it out by measuring the inside depth of your tank.



I just received two of the Spruce gauges to replace my fuel gauges. They have too much throw to work the same as the original gauges. If you were to adjust it to show full accurately then it will show empty way early. If you adjust it to show empty correctly it will never show full. I’ll be returning and looking for a place to refurbish my gauges.

Below are pictures of the original and Spruce gauges at their full travels. You can see in the first picture that the Spruce gauge has a lot more “up” travel.

Doug

A6407998-97ED-4BFE-A523-8C33CD9CF63B.jpeg

37426020-D65E-4E79-9AD8-F98B9417AA7C.jpeg
N1235D - 1951 170A - SN: 20118
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Re: Fuel guage repair

Postby gahorn » Fri Feb 28, 2020 3:53 am

Doug, it appears all you need do is shorten the rod to the appropriate length to mimic the OEM gauge.
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Re: Fuel guage repair

Postby n2582d » Fri Feb 28, 2020 6:39 am

Doug,
It looks to me like your original gauge must have been indicating "full" until it was nearly half-empty. The gauge is mounted in the middle of the tank vertically so when the float arm is horizontal the gauge should read half-full (or half-empty depending if you are an optimist or a pessimist :wink:). According to the installation sheet I posted here, "The float length dimension (measured from the float pivot point to the end of the float) should be proportional to the inside tank height and is usually less than 1/2 of the vertical inside height of the tank." SEB99-18 Revision 1 says to drain all your fuel from the tanks and then, with the fuel valve off and the aircraft leveled, add unusable fuel to each tank. The gauges should read empty. Next fill the tanks and confirm that the gauges read full.
Gary
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