170A/B fuel tank quantity

[GAHorn]

I was told the 2.5 unusable was because if you are coming in to land with 40 degrees flap, your nose is pitched so far down that the fuel is rolled toward the front of your tanks. The fuel line comes out of the rear of the tanks and if Cessna had put a fuel pick-up at both the front and rear of the tanks then we could count all the fuel as usable.

The fuel lines exit the tanks at the middle of the tanks, approximately beneath the gauge, and are then routed down the aft door posts, so extreme nose up or down can lead to interrupted fuel flow.

Later systems (172/182 etc) had dual lines, both fore and aft, which addressed the issue.

[mantry]

Great topic to read through, I was down at the airport visiting my 170A and a 170 owner was asking me about my fuel tanks. Here is his question:

He has a 1948 170 that had the 3 12.5 gallon tanks in it origionally, at some point before he purchased it as a rebuild project when he opened it up he noticed that it actually has 4 tanks in the plane. He had to have the 4th tank signed off via field approval during the rebuild. We are assuming that they are 4 12.5 gallon tanks for a total capactiy of 50 gallons. The plane is beautiful and has a IO-360 engine.

He did a fuel flow/totalizer add on a year or so ago and as the result of this he drained all the fuel out of the plane using the sump drains in the two tanks and then filled it back up but was only able to put in 44 gallons.

So his basic question is how much fuel does it actually hold and how much of it is useable?

I didn't think about the tire/gear leg combination, that sounds like it could explain a lot.

I'll tell him next time he FILLS it up, to then put it in the hanger and raise the tail 4-6" or so and then see if that changes the fuel level in the filler neck. Also, to try to trickle in more fuel.

Any other thoughts and or comments on these 3 1/2 or 4 tank 170 models?

Thanks in advance!!!!