The POH for my 59 180 has the fuel capacity at 65 gallons total. For any type of flight attitude they say that 55 gallons is usable fuel. After that it says that 62 gallons is usable in straight and level flight. I understand what they're getting at with the different capacities but what I'm wondering is who has burned into those 7 gallons between 55 and 62 and what can and can't you do? In most cases of course, even if you are using those 7 gallons in your flight planning, they will fall in your 30 min reserve and not generally get used anyway. Landing at any sort of prepared strip shouldn't usually push the plane beyond what anyone would call straight and level flight and in most cases a person doesn't land in the real tight places with empty tanks. However can a person still do a steep turn if they have to? A steep climb on an overshoot? I would expect that the further you burn down into this fuel the straighter and leveler you'll have to fly. Just curious if the experienced people here have explored this with these planes.

While I can't answer that question I'm very interested in it. Seems like the condition of the bladder could come into play, like wrinkles, snaps unsnapped, things like that.

You can run them pretty low, but make sure you have it on "both" for anything other than comfortable cruise.

Your model only has one fuel port in the bladder, in the aft end. Nose down it will unport.

I'm afraid it's a liitle worse than you've indicated for us early 180 owners. Per AD 75-16-01:

http://www.airweb.faa.gov/Regulatory_an ... enDocument

which references SE75-7:

https://support.cessna.com/custsupt/con ... s_id=25704

which in turn references "Chart 1":

https://support.cessna.com/custsupt/con ... s_id=25705

which results in having to subtract 2 gallons from the total and useable fuel quantities for each fuel bladder which has been replaced with a a fuel cell with a date of manufacture after 1973. So, for my 180B, that works out to 51 gallons useable.

When I calibrated my EI CGR-30P with the aircraft leveled, the right tank held 28.6 gallons till empty, and the left 30.0 gallons. That's level, and not in a landing or stall AOA. To figure that out, you'd have to mimic that AOA by raising the main gear and digging a hole for the tailwheel, which was more effort than I was willing to extend.

I've heard if you put it into a little bit of a side slip you can force the gas up against the outlet side of the tank and get more out.

In my '59 Cessna 180 nearly all of the 32.5 gallons in each tank is usable in level flight. In these early models there is only a single fuel pickup on each side, towards the middle of the tank so when you are three point you can have 7 or 8 gallons in the tank and not be able to get it to your engine (especially with big bush wheels and a small tailwheel) If you leave the fuel selector on both and burn 4+ hours you will get on the ground and the engine will quit when you lower the tail. My practice is to run one tank dry the last hour of a four hour flight so I know I have enough in the other tank to taxi off the runway when I get there.

jrc111 wrote:I'm afraid it's a liitle worse than you've indicated for us early 180 owners. Per AD 75-16-01:

http://www.airweb.faa.gov/Regulatory_an ... enDocument

which references SE75-7:

https://support.cessna.com/custsupt/con ... s_id=25704

which in turn references "Chart 1":

https://support.cessna.com/custsupt/con ... s_id=25705

which results in having to subtract 2 gallons from the total and useable fuel quantities for each fuel bladder which has been replaced with a a fuel cell with a date of manufacture after 1973. So, for my 180B, that works out to 51 gallons useable.

When I calibrated my EI CGR-30P with the aircraft leveled, the right tank held 28.6 gallons till empty, and the left 30.0 gallons. That's level, and not in a landing or stall AOA. To figure that out, you'd have to mimic that AOA by raising the main gear and digging a hole for the tailwheel, which was more effort than I was willing to extend.

This is some great info, thanks

180driver wrote:In my '59 Cessna 180 nearly all of the 32.5 gallons in each tank is usable in level flight. In these early models there is only a single fuel pickup on each side, towards the middle of the tank so when you are three point you can have 7 or 8 gallons in the tank and not be able to get it to your engine (especially with big bush wheels and a small tailwheel) If you leave the fuel selector on both and burn 4+ hours you will get on the ground and the engine will quit when you lower the tail. My practice is to run one tank dry the last hour of a four hour flight so I know I have enough in the other tank to taxi off the runway when I get there.

Very interesting also. This is probably less of a concern in my plane seeing as it's on floats all the time. No nose high 3 point landings and no taildragger taxi attitude.

Nose high climb outs, too.


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180Marty wrote:I've heard if you put it into a little bit of a side slip you can force the gas up against the outlet side of the tank and get more out.

Yes!

Could be a bacon saver!

I have the same issue with my P172D, 52 gallons total, 21 gallons from each tank in all attitudes, 23 1/2 gallons from each tank in level flight. The tanks are aluminum, so there's no issue with bladder wrinkles, but the rest of the issues are the same.

So my practice is generally to keep to under 38 gallons used (3.9 hours)--not too hard to do, because typically my bladder requires that I land sooner than that anyway. That gives me a minimum of about 35 minutes reserve using the 42 gallon usable figure, and another 35 minutes reserve (total 70 minutes) using the 47 gallon usable figure. The one time I can remember going over that 38 gallons use, it was 40 gallons, and I was very careful to maintain straight and level when the flow meter showed I'd gone over 38 used.

I suppose you could fly on one tank and run out the other to make sure how much is actually usable, but I've been reluctant to do that, and it wouldn't tell you how it would react in a different configuration, such as a steep approach or a sudden go around. I only have one experience, over 35 years ago, running a tank dry on the T210 we had, and because it seemed to take close to forever to get the engine firing again on the other tank, I decided then not to do that again.

Cary

180Marty wrote:I've heard if you put it into a little bit of a side slip you can force the gas up against the outlet side of the tank and get more out.

Had a '58 180 that I was planning on replacing a bladder, so I took it out flying to use up as much as I could, and to see how much flight time I would get once the needle got into the red arc. Took about 20 mins longer than I thought for it to run dry using a little sideslip as mentioned above. When I got back and removed the wing drain, only about a quart of fuel came out!

On a side note, later while removing the right side bladder I found two pieces of wood measuring about 2"x2"x5". Those things were floating around in the tank for a good 30 years

This is not good news. I read through this rather quickly. Must we reduce the _usable_ capacity by 2 gallons? Per side?

That's not cool.

jrc111 wrote:I'm afraid it's a liitle worse than you've indicated for us early 180 owners. Per AD 75-16-01:

http://www.airweb.faa.gov/Regulatory_an ... enDocument

which references SE75-7:

https://support.cessna.com/custsupt/con ... s_id=25704

which in turn references "Chart 1":

https://support.cessna.com/custsupt/con ... s_id=25705

which results in having to subtract 2 gallons from the total and useable fuel quantities for each fuel bladder which has been replaced with a a fuel cell with a date of manufacture after 1973. So, for my 180B, that works out to 51 gallons useable.

When I calibrated my EI CGR-30P with the aircraft leveled, the right tank held 28.6 gallons till empty, and the left 30.0 gallons. That's level, and not in a landing or stall AOA. To figure that out, you'd have to mimic that AOA by raising the main gear and digging a hole for the tailwheel, which was more effort than I was willing to extend.

soyAnarchisto wrote:This is not good news. I read through this rather quickly. Must we reduce the _usable_ capacity by 2 gallons? Per side?

That's not cool.

Usable & total reduced by 2 gallons per bladder (side), only if the original bladders were replaced with bladders where the replacements were manufactured after June 1973. This makes it sound like the Cessna bladder design changed in '73 to be smaller if the total must be changed as well as the usable.

-asa

B) On all models of aircraft manufactured in and prior to 1973 review the aircraft records to determine if new fuel bladder(s) have been installed since June 1, 1973, and if so, comply with Paragraph A of this AD unless it is established that the fuel cells installed were manufactured prior to June 1, 1973, and this fact is entered in the permanent aircraft records.

NOTE: The owner may review the aircraft records and if he determines that new fuel bladder(s) have not been installed since June 1, 1973, may enter such information in the aircraft records.

What about aftermarket bladders not manufactured by Cessna? Is it EVERY bladder made after 1973?

Frankly, asking someone else how much fuel is available in their pretty old airplane doesn't do you a lot of good. As noted, there are Cessna bladders, aftermarket bladders, and sometimes other issues that can affect the useable.

PLANNING on using a side slip to get fuel out of a tank is a fool's game, but it's good to know if you really screw the pooch sometime.....but far better to NOT screw the pooch in the first place.

Get the airplane leveled on it's main wheels, with the tailwheel up on a barrel or sling, etc, to get the airplane into a level flight attitude. Before you do this, run the fuel down to minimum you're comfortable with. Open the gascolator drain and drain both tanks with the fuel selector on "Both".

Now, get the airplane to a pump with a certified meter, and fill it up with fuel. THAT is YOUR useable fuel. Granted, you may be able to get a little bit more out of it by fussing with it, but this should give you a good baseline.

But, bear in mind, that's the useable fuel in level flight, NOT maneuvering. So, get the fuel level down to that point, then descend/climb or maneuver at your own peril.

Frankly, I've never liked bladders because there can be a little variable to a lot of variability in their capacity.

MTV

I'm not a lawyer (not bragging, but I'm just not), but as an AP, my read is any new fuel bladder after 1973 requires the operators manual be corrected and new numbers be written on the fuel selector. Sorry. On the other hand, a rebuilt fuel bladder is probably exempt from that requement.

As MTV suggests, the exact fuel amount that constitutes the Cessna unuseable fuel is a regulatory amount, vs the real world unuseable fuel depends on flight attitude and also on fuel flow required. To figure out the "unuseble fuel" for experimental aircraft reference page 22-23 of AC 90-89A:

https://www.faa.gov/documentlibrary/med ... 90-89a.pdf

Here's an example of me figuring out required fuel flow with a Bearhawk:

http://mykitlog.com/users/display_log.p ... 5189&row=8

mtv wrote:Frankly, asking someone else how much fuel is available in their pretty old airplane doesn't do you a lot of good. As noted, there are Cessna bladders, aftermarket bladders, and sometimes other issues that can affect the useable.

PLANNING on using a side slip to get fuel out of a tank is a fool's game, but it's good to know if you really screw the pooch sometime.....but far better to NOT screw the pooch in the first place.

Get the airplane leveled on it's main wheels, with the tailwheel up on a barrel or sling, etc, to get the airplane into a level flight attitude. Before you do this, run the fuel down to minimum you're comfortable with. Open the gascolator drain and drain both tanks with the fuel selector on "Both".

Now, get the airplane to a pump with a certified meter, and fill it up with fuel. THAT is YOUR useable fuel. Granted, you may be able to get a little bit more out of it by fussing with it, but this should give you a good baseline.

But, bear in mind, that's the useable fuel in level flight, NOT maneuvering. So, get the fuel level down to that point, then descend/climb or maneuver at your own peril.

Frankly, I've never liked bladders because there can be a little variable to a lot of variability in their capacity.

MTV

I appreciate the thoughts Mike and I'm not sure if all this is directed at me,
I wasn't so much asking about what exactly the fuel capacity was on my specific plane or what I could do once the tanks were extremely low while already in straight and level flight. I'm not looking to maximize flight time by sideslipping to get more fuel out of the tanks although that's good to know for a bad day.
Since two different usable fuel volumes are listed for the plane what I was wondering is what is the plane still capable of when you've gone past the lower usable fuel volume and are now into the gallons meant only for straight and level flight (hopefully not very far into those gallons). Specifically could you still make a steep turn or a steep climb on an overshoot. I would think the lower you've burned the less maneuvering you can do. It's not that I want to make a habit of burning these gallons, as I said I think they'd only ever fall into the 30 min reserve category.
I'm most definitely going to drain the tanks of the level plane and then meter in the fuel to see how much they really hold.
Again, thank-you
Matt

The best way to get the most out of whatever fuel you have is to only burn on tank at a time cough one in level flight than go to the other until prop stops turning. This will get you a few gallons more. I would agree with Mike each plane is different. You have to go drain and refill or cough a tank and refill you figure out a baseline. Interesting input on the 3 point attitude I will have to check mine.
DENNY