Fuel Gauges

[Bruce Fenstermacher]

Karl I totally agree with you on the accuracy of these gages.

So you seem to indicate that these gages aren't accurate yet the CAR says that they must indicate the quantity of fuel.

But if they aren't accurate how could they indicate the actual quantity of fuel. The question then is how accurate do they have to be to meet the CAR. The only tolerance the CAR gives us is O at the unusable fuel point.

[steve grewing]

My experience on '48 with four fuel tanks.
When I installed my gauges during my refurb I set them per the CAR's. That is, I had the plane in a level flight attitude and put the stated unuseable fuel in each wing. (Actually used Jet A for safety reasons. Let's not discuss the differences in specific gravity.) I then reached through the filler hole using a long rod with a small crowfoot wrench afixed to the end to adjust the float to read "empty". I used the lower edge of the red band as "empty". This is actually easy to accomplish. I then placed the aircraft in a three-point stance on level floor and drained the Jet A and flushed each tank and fuel system. I visually verified tanks were empty. I then added one gallon of Avgas at a time while logging the indication on the fuel gauge and on a dip stick made from wooded dowel and marked with industrial indelible ink. At 1/4 (top of "NO TAKEOFF" range) = 7 gallons, 1/2 = 10.5 gallons, 3/4 = 14.5 gallons and "full" = 19 gallons. Useable is 23 per side. (On a side note, when I initially fueled the aircraft with a fuel truck, the left wing held 24.6 gallons to the lip. I did not fuel the right side. This was the fuel I used for my initial flight and half a load of firewater was enough. Is that being confident of my work? Yes I did balance the fuel load.)
Gallon measurements on the dipstick in inches were:
3 = 0” 11 = 2”
4 = 3/8” 12 = 2 3/8”
5 = ½” 13 = 2 5/8”
6 = ¾” 14 = 2 7/8”
7 = 7/8” 15 = 3”
8 = 1 ¼” 16 = 3 3/8”
9 = 1 ½” 17 = 3 ½”
10 = 1 ¾” 18 = 3 7/8” (= 15/16 on gauge)

I quit at 18 gallons as that is all the fuel I had available at the time. I used my calibrated right eye (bifocal in place) to read the stick and my calibrated right hand (shakes the least) to accomplish the dipping. I find the gauges to be accurate to my chart.
I have the chart and measurements in a Word document. It will not copy to post is here. I printed it and my personal checklist on photo paper and then laminated them back-to-back. If anyone wants the Word doc, PM me your email address and I'll send it.

Steve

[GAHorn]

Steve,...when you calibrated your dipstick, how/where did you place it in the tank in order to guarantee consistent placement, both for yourself, and for others who might use your method?

[steve grewing]

George,

I held it vertical and in the center of the opening. It's all rather subjective as there is slushing of the fuel to deal with. I was not clear in that my dipstick is marked in 1/2 inch increments. The measurement is then compared to the chart.

Steve

[CAVU Mark]

I have a 170A and need one fuel gauge for the left tank. I read all the posts and was wondering if there is any current suggestions or back to the one 4 years ago? I have not evaluated the problem yet which may include any number of repairable items prior to replacement. All suggestions are welcome.

Thanks.

[3958v]

Just in case you guys wonder why this is important http://www.washingtonpost.com/wp-dyn/co ... 01046.html Bill K

[cessna170bdriver]

Even MORE important to visually verify fuel quantity before departure, and pay attention to the clock....

Miles

PS: Ron, the article says this guy is from Lafayette. Do you know him?

[3958v]

I always measure on longer flights. Gauges can also be important if one tank drops toward empty extra fast it probably means some one left the cap off the other side. If you are running with the fuel valve on both the missing cap will create a vacuum in that side and sucking the fuel out of the side with the cap still on. Don't ask me how I know. Bill K

[Bruce Fenstermacher]

Mark, I don't think there is any new fresh advice from that offered 4 years ago.

[CAVU Mark]

Thanks. This is one item requiring repair prior to my checkride, hopefully in Feb!

[mccarlie]

The original gauges were made by Scott. Rochester bought the product line. They are located in Dallas. I've talked to them extensively about this over the years. Their gauges (the ones re-sold by Spruce) are what are in my airplane, after having been modified by the installer. They work perfectly and look identical to the originals. (They may have been easier to install while the airplane was disassembled for rebuild, or while the tanks were removed.)

Rochester still makes the gauges for Cessna, for replacement use in a 170's. They are expensive when acquired thru Cessna, but they are the genuine product, and not all that out-of-line when compared to other, current prduction aircraft gauge prices. (Superceded PN is: 7083-00022 and costs about $260. Hill Aircraft: 1-800-998-7832 )

Rochester will not sell you the -00022 gauge directly, as they are committed to providing that exact model only to Cessna. They are basically made up from the Rochester 7083-5H76 gauge, and the 5-00894 Dail. The gauges purchased thru Spruce and others are a minor variant of the Rochester 7000 Series gauge (a 7080 actually), which can be used in both the vertical or horizontal positions.
The last number I had for Rochester was 800-982-0030 or 214-241-2161. They are insistent they will not sell direct for contractural and liability reasons. Perhaps thru them you might locate a local dealer who might be able to provide overhaul for your gauges, but that's only an idea.

What type of logbook sign off, paper trail, or basis for approval has been used for installing this Rochester gage from Spruce? Thanks, Doug.

[GAHorn]

...What type of logbook sign off, paper trail, or basis for approval has been used for installing this Rochester gage from Spruce? Thanks, Doug.

The parts were utilized to repair existing gauges and/or to mfr "owner produced parts" per FAR 21.303 (b)2.

PS- I also see that way back when...Bruce asked me about fuel gage accuracy regading reading empty when the tank is empty. My experience is exactly the same as his.... The only criteria for fuel gauge accuracy ever quoted me has been that they must read empty when the tank is empty.

[rydfly]

Rochester still makes the gauges for Cessna, for replacement use in a 170's. They are expensive when acquired thru Cessna, but they are the genuine product, and not all that out-of-line when compared to other, current prduction aircraft gauge prices. (Superceded PN is: 7083-00022 and costs about $260. Hill Aircraft: 1-800-998-7832 )

FYI, I was rummaging through post history regarding the Scott fuel gauges since I'll likely be repairing/replacing one in the future. The cost for the genuine part is now $432.65 each from Hill Aircraft.

[submoa]

George,

Hey guys, FNG here and just bounced in on this old thread. Hope it's not too old.

I understand exactly where you are coming from on the gauges. I bought the same gauges for my 1954 180. The "reach" of the guage is too short and no matter how you bend, cut or try to adjust the arm, it will not allow full travel of the arm inside the tank. You are absolutely correct about the gear ratio. It is different and if the arm is cut to the length ( has to be short) to allow it to indicate properly, the float hits one of the screw bosses on the inside of the bladder, and it will never go all the way to empty. I believe that the gauges of this type for the Cessna are probably all the same and that the actual quantity of the tank is not important. It's the total depth of the tank that's critical to proper indication. These gauges do not read in total agllons, but fuel remaining relative to total capacity, whatever that may be. Both the original factory guage and the Spruce Replacement use a magnetic coupler. The problem I have with the old guages and I think it's the common problem, is hat the magnets start to lose their magic, and do not effectively hold whatever piece inside the gauge it's supposed to hold onto. This allows the darned things to bounce all over. I tried to remagnatize one of my old guages and had a little success---but it was short lived. If whomever has that flyer from Rodchester or Scott, can send it to me I'd like to see it. Thanks Much Gang!!

[GAHorn]

submoa,... again, we may be talking apples-to-oranges. YOu don't specify exactly which model gauge you found difficulty with. Making the statement that you bought the "same gauge" .....doesn't mean that is so. What you probably meant was that you bought a mechanical float type gauge that was similar and had issues when installed in your Cessna 180 aircraft. Again,....not the same scenario.

The "flyer" issued by Scott/Rochester is in my personal library at home. I'll try to locate it and scan it into this discussion when I get home....in 3 weeks.