The International Cessna^® 170 Association

Any one know who sells a calibrated stick for checking fuel.....I have seen a glass hollow tube type that is professionaly marketed...anyone know Thanks Pat

Check the posts for this subject with the search button. I have one and followed Georges instructions from his posting. Basically you get a C-172 dipstick (fuelhawk brand I think) and cut off the bottom 1inch ... but you'd better check George Horn's posting to make sure you get it right.

Good Luck,

The pertinent text from my previous msg regarding making your own fuel dipstick:
A FuelHawk brand clear measuring tube (available from Sporty's or Aircraft Spruce) for a 172 is perfect, if you use a tubing cutter and cut off the two lower gallon indices (below the zero). Then, use a wire wheel on a bench grinder to polish the cut end to a smooth radiused finish like previously. Place the tube at the aft end of the fuel-cap opening, and the bottom of the FuelHawk onto the bottom of the tank exactly against the baffle at that mid-tank line. (Easy to find,....just put it on the bottom and try to move the tube aft. It'll run into the baffle.) It will read correctly when so modified and used.
Otherwise, any paint store will give you a paint-stir stick which can be marked/calibrated with an ordinary ball point pen.

I should point out that the FuelHawk tube I was referring to was for the 172 with 19 gal. each tank. (The tanks are really 21 gallon, but 2.5 gal per side is unuseable, so the diptube is calibrated to 19 gal, which happens to be applicable for the 170 A and B models. This tube is not applicable to the ragwings.) The 172 FuelHawk is marked to a max of 19 gals, but has at it's bottom end two indices below the zero mark (to accomodate unuseable fuel for the 172. The 170, having the same fuel tanks/system as the early 172 also has the same unuseable fuel, but that fuel sits at the rear of the tank due to the 3-point stance of the taildragger, and is not displayed on the lower end of the tube.) Therefore.....Cut the tube off at the zero mark for use in a 170 A/B.

It may not be true, but I have heard that these devices are not calibrated for use in flight.

I was under the impression that the B vintage had 18.5gal useable per side.

n3437d wrote:I was under the impression that the B vintage had 18.5gal useable per side.

That's what the book & placards say...

I have a fuel hawk that is not for any specific airplane. You calibrate it yourself. It comes with directions on how to do this. Even so, I get a little nervous when I have more than 3 hours on the fuel tanks, and I get real nervous and am looking for a place to land... pronto...at 3 1/2 hours. It may just be paranoia but I don't trust the quoted usable amount at all.
The only time I have ever experienced complete silence in an airplane was while flying my 170 with around 3 1/2 hours on the tanks and I put it in a nose low attitude. While the engine only quit for about 2 seconds I had already zipped through my initial engine out procedures and found a place to land when it kicked back on. My 11 year old daughter was with me, and the only reason she knew anything was wrong was because she saw my hands moving around real fast (fuel selector, mixture, ignition, primer). I could have kicked myself when I realized that I had probably uncovered the fuel port in the tanks by the nose low attitude.
It really wasn't any big deal in the great scheme of things, it is just one of those things that I store in the old noggin... only fly normal attitudes when low on fuel.
David

dacker wrote:The only time I have ever experienced complete silence in an airplane was while flying my 170 with around 3 1/2 hours on the tanks and I put it in a nose low attitude. While the engine only quit for about 2 seconds I had already zipped through my initial engine out procedures and found a place to land when it kicked back on. My 11 year old daughter was with me, and the only reason she knew anything was wrong was because she saw my hands moving around real fast (fuel selector, mixture, ignition, primer). I could have kicked myself when I realized that I had probably uncovered the fuel port in the tanks by the nose low attitude.

I did something similar in a J-3 with about half fuel. I showed someone what zero g felt like, and immediately later the engine showed me what zero power sounded like. In my case it wasn't unporting the tank; I had just deprived the gravity feed fuel system of its gravity.

Miles

N73087 wrote:It may not be true, but I have heard that these devices are not calibrated for use in flight.

I use mine in flight all the time, & it seems to be accurate. It's climbing up on the strut & hanging on in the slipstream that's the problem......

Eric

n3437d wrote:I was under the impression that the B vintage had 18.5gal useable per side.

That's what the math works out to. There are several ways to get confused about the fuel system when reading the various descriptions. In one genuine Cessna document I've read, the 170 has two "twenty gallon" fuel tanks. In another, including the type certificate and the Owner's Manual, they are stated to be two "21 gal." tanks. The statement actually says they are 21 gallon tanks, holding 18.5 gallons of useable fuel each. This is also probably technically incorrect because it ignores the plumbing. The same part number tanks are installed in the early 172's where they are claimed to be "19 gals each". In all cases, the fuel systems are stated to be 42 gallon systems, with 5 gallons unuseable. This means the individual tanks are expected to hold 18.5 gallons of useable fuel. (And they do. If you fuel them slowly with the fuel selector off you may actually get another gallon in them tho'.)
Officially, it is a 42 gallon system, with 5 gallons unuseable. The most accurate way to say it is probably something like "A 42 gallon fuel system consisting of two tanks and associated plumbing, providing 37 gallons of useable fuel."

gahorn wrote:The statement actually says they are 21 gallon tanks, holding 18.5 gallons of useable fuel each. This is also probably technically incorrect because it ignores the plumbing. ... The most accurate way to say it is probably something like "A 42 gallon fuel system consisting of two tanks and associated plumbing, providing 37 gallons of useable fuel."

Including the plumbing is splitting hairs. If you assume 3/8 x 0.035 wall tubing for plumbing, it would take over 260 feet of it to hold one gallon . Even if you assumed 3/8 ID hose, it would still be in the neighborhood of 175 feet! Even including a cup or two in the gascolator and carb bowl, I doubt there's more than a quart (maybe 2 minutes at cruise) in the plumbing.

IMHO the biggest variables are the physical attitude of the airplane while filling, and the mental attitude of the filler: in other words, how patient you are putting in that last gallon or two.

Miles

That's certainly true, Miles, especially in the context of this discussion regarding tank capacity. I was only wishing to point out that we should consider the system as a "whole" rather than isolate individual components.
An example of how this might be a better way to view it is: When refueling, it can take almost an hour and/or over 16 ounces (about a pint) of fuel to be drained from the gascolator before water in the new fuel reaches our fuel sampling cups. Even more might have to be drained to observe it in the cup itself, and even then the water wouldn't have been purged from the fuel system.
No one I have ever observed drains that much fuel during a pre-flight check.
This was nearly disastrous in a 182 just refueled from gas cans I once planned to ride in. (The engine died at the run-up area. The airplane belonged to an AP/IA who usually obtained his fuel from the local Texaco.)

George you bring up a good point about water settling out of avfuel. Don't know what the rate is or given the rate how long it would take give the depth of our tanks but in a UH-1H Huey using JP4 it would take over 2 hours.

I laugh when I see people take a fuel sample just after filling their tanks. Any water in the fuel or in the tank was just mixed back together and needs to settle out.

As for the total amount of fuel and your modified fuel stick which reads 19 gal at the max. This is what you want. A stick that has more capacity than the tank. Since we probably will only get about 18.5 gal in the tank it will still be read on the stick. if the mark stopped at 15 gal lets say you would always be over the highest mark and only know that you have more than 15 gal but not the total amount in the tank.

N9149A wrote:
I laugh when I see people take a fuel sample just after filling their tanks. Any water in the fuel or in the tank was just mixed back together and needs to settle out.

It's getting a little off topic, but the above is a good reason not to refuel if the truck has just filled the storage tank. I won't even refuel my car at a station where I know the truck has just been there. My Saturn owner's manual doesn't mention a sump drain.

It's also an advantage of above ground tanks that they can be me more easily checked/drained of water (after they've been allowed to settle). When I worked as a line boy at TYS (1973 ), we used to get several pints of water out of the 5000 and 10000 gallon truck tanks first thing every morning.

Miles

On line the other day at a "general aviation " Users Group I saw a posted story. There could be something to be learned from this. Seems a Cessna single owner was having problems with his fuel gauges. He decied to "fly-off" most of the remaining fuel by doing Touch and Goes in the pattern. It seems that on the last T/O the engine sputtered, caught, sputtered and then quit with no reserve alt. to do a 180. The owner escaped injury but now has more problems than just the quirky fuel guages.