The International Cessna 170 Association

How many gallons are left when fuel level is at the tabs. During preflight today I peerer into tanks and both were just above the tab or divider, or baffle what ever it might be. Just wondering if anyone might have taken the time to measure this? I'm curious as the accuracy of my fuel gauges. Thanks in advance!!

B-MOD about 1/2.

About 1/2 of 20gals or 18.5? That's only a .75 gallon difference between the two so it would be safe to assume 9 usable gallons left at tabs?

If you really want to know, when you see the fuel at the level you want to know about, set the selector valve on that tank and fly the airplane until the engine quits. Just be sure you have enough to get up to a couple of thousand feet. The engine will recover very quickly when the selector valve is switched.
When flying my stock tanked C-170B, I normally set the selector on both for most of the flight. I always switched to the other single tank when one tank got down to 1/4 with the skid ball centered. When the selected went empty and the engine quit. then I knew exactly how much I still had left. Previous experience told me how long I had on that tank when it was reading 1/4.

It is a good idea to run a tank down until the engine quits, and then land with that tank shut off. keep the selector valve shut off until the refueling is completed. Make and mark a dip stick as you refill that tank and you will always have a way to get an accurate fuel reading on preflight. Do the same on the back side of the dip stick for the other tank, but be sure to mark the proper side on the stick. The capacity of the individual tanks may vary.
Looking in the filler neck is a damn poor way to get a fuel measurement.

blueldr wrote:Looking in the filler neck is a damn poor way to get a fuel measurement.

A fuel stick is a good thing to have.They make blanks that you can mark yourself while you fill up.
With the tank empty, you stick it every 5 gallons read on the pump.
I had a fuel line fail and had to siphon the tank empty. It's not that much trouble if you have enough empty cans and then get the last bit out from the drain.
It's a good time to replace those drains too. I found all kinds of dead critters in my tank when I flushed it.


My personal policy is if I can't stick my finger in the gas, it needs filled up.

bagarre wrote:

blueldr wrote:Looking in the filler neck is a damn poor way to get a fuel measurement.

A fuel stick is a good thing to have.They make blanks that you can mark yourself while you fill up.
With the tank empty, you stick it every 5 gallons read on the pump.
I had a fuel line fail and had to siphon the tank empty. It's not that much trouble if you have enough empty cans and then get the last bit out from the drain.
It's a good time to replace those drains too. I found all kinds of dead critters in my tank when I flushed it.


My personal policy is if I can't stick my finger in the gas, it needs filled up.

Using the baffle is exactly the same as using a stick.

Be careful running around with one tank completely dry. Takeoff and Land with BOTH tanks ON and with BOTH tanks containing useful fuel is the best practice.

Anyway...
For a B-model, the FuelHawk for a 19 gallon C-172 makes a PERFECT fuel gauge dipstick ... IF YOU MODIFY it and use it properly.
http://www.aircraftspruce.com/catalog/p ... geC172.php

Using a common plumber's tubing cutter, CUT the plastic tube exactly at the ZERO mark. (The 172 tube begins a -2 then counts up to 0 then goes further to 19.) By the way.... I have a wire wheel on my bench grinder. After cutting the tube I polished the cut end by gently holding it up to the wire wheel in order to achieve the same rounded contour as the mfr'r. This is not necessary but I did it to assure no cracks developed at the cut end. You might achieve the same results with a piece of sandpaper. But be certain the lower end is exactly at the "zero" mark on the original C172 19 gal. fuel hawk. (cost is about $10)

Now, utilizing it as it's directions indicate.... place the tube down inside the tank, and rest the bottom of the tube at the forward side of the tank-divider ("tab" as you referred to it) place your finger over the upper/open end of the tube and withdraw it from the tank. The fuel level indicated will be extremely accurate.

I have done this and added 2 gallons at a time to a tank which was run-dry and it is a perfect measurement for a standard B-model resting in the 3-point position on a level ramp. The A-model should not be any different.

mit wrote: Using the baffle is exactly the same as using a stick.

It is but I've found a stick a little easier.

Thanks Everyone!!

Don't forget to be on level ground

Just remember to make yhour dip stick from a tank that has been RUN dry, noy DRAINED. Then you will be measuring USEABLE fuel.

blueldr wrote:Just remember to make yhour dip stick from a tank that has been RUN dry, noy DRAINED. Then you will be measuring USEABLE fuel.

If you fly wing s level all the time.

If you measure unuseable fuel that way, you'll come up with more than the 37 gallons Cessna claimed was useable. I calibrated my stick the other way -- started with a full tank (37 gallons useable), removed two gallons, marked the stick (35 gallons), lather, rinse, repeat. If you do that, zero on the stick corresponds to zero useable in the tank.

If you ever get down to zero and you fly real smooth and coordinated with the wings level, the engine will run for a while on "unuseable" fuel. But that's the way the gauge is required to read also.

jrenwick wrote:If you measure unuseable fuel that way, you'll come up with more than the 37 gallons Cessna claimed was useable. I calibrated my stick the other way -- started with a full tank (37 gallons useable), removed two gallons, marked the stick (35 gallons), lather, rinse, repeat. If you do that, zero on the stick corresponds to zero useable in the tank.

Interesting, perhaps that is why the dipstick George mentioned above starts at minus 2 instead of zero.

I should have said I started with 18.5....