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C-180 Fuel Capacity Issue/Question

sj

Staff member
Northwest Arkansas
Well folks, flying back from Grand Rapids today in the 55 C-180 I started with full tanks 3.8 hours later with one tank empty, I landed on the left tank to get some more gas. Still running good on touchdown (tail high), tail high taxi to the turn off, came around the corner put the tail down and the engine died.

This is the second time this has happened. This time I had 13 gallons of gas (1.0 unuable in the right, the rest in the left) in the plane.

I do have 8:50 tires, but I am wondering what is going on here. I have 60 gallons total, and the book says in level flight I can use up to 58 of it, and up to 55 of it in "non level" flight.

I have an EI fuel gadget which is very accurate, and confirmed the quantity when I filled it up. I also have run both tanks dry in the past to confirm the hold the whole 30 gallons (1 unusable).

Any insight on this one?

Thanks!

sj
 
Steve,

Are you still chasing that problem...I thought you had it fixed...Guess not...

Check to see if your bladder bottoms are laying flat in the tank bay, I've seen them wrinkle/bubble up and trap some fuel/water. forward of the pickup point. I would be surprised if it could trap that much fuel but you never know, I've seen some come up pretty good when not much gas in them.

David.
 
Should I be on "both" when taxiing? Would it really matter if there is no gas in the right side anyway?

Before I assumed it was part of the mag / hot start issue.

Guess I better practice my tail high taxi technique, or carry a powertow around with me.

sj
 
Steve,

I thought that 180s have a pickup in front and back of each tank. THey surely have a pickup in the back of each tank, so tail up or down shouldn't make a difference.

Which direction did you turn? If you turned away from the fuller tank, the engine could suck wind, due to fuel sloshing outboard.

Why are you running on one tank or the other anyway? I've always run these things on Both, for virtually everything.

Has this ever happened with the fuel selector on both?

MTV
 
Mike, not sure, when I get down to the brass nuts on fuel, even though I have an EI gadget, I switch to left/right fuel management so I can calculate what I have left. I will try it on both. I do know that I did run the mixture in, so it was not that. Usually I leave it out on final (not that high anyway, 1500 msl).

Seems kinda strange to me. I might need to check to make sure the rear ports are flowing I guess.

I had darn near one hour of fuel left in the tanks, and I would love to have that extra 30 minutes of flying to count on.

sj
 
I guess I should say, maybe I could have done the flying but I would need to land next to the fuel pump.

sj
 
If its only doing it on taxi/3 point touch down check your rear pickup point and lines for blockage, with only 10-12 gals it will not feed from the front in 3 point position as the level will be too low.

BTW: I always ran in the both position even when low on fuel and never had a problem. I flew jumpers for quite a while and we always landed with the minimum fuel for the weight. Just make sure you stay in co-ordinated turns, no extended slips...

David.
 
Steve,

It is always wise to remember that the FAR's provide a Minimum set of requirements.

I want ONE full hour of fuel in my tanks as a reserve. Thirty minutes is not enough. A little divert around a thunderstorm or a hold due to fouled runway can rapidly eat up 30 minutes fuel. Keep an hour's worth in the tanks, and if you get slipped thirty minutes, no big deal. Get pushed thirty minutes with thirty minutes fuel and the pucker factor goes way up there.

As you say, though, if you are supposed to have X amount of fuel available, you should, or start flight planning for the lesser amount.

Does this consistently do this with one tank or the other? I'm with the others that it sounds like a fouled rear tank pickup, and I'd be surprised if both were fouled. Course, someone sometime might have loaded a big gob of bad gas.....

MTV
 
Mike, I DID have an hour left, I just could not use it... at least on Taxi!

Having experienced air contamination in the fuel as a young pilot, I am very wary of my fuel reserves...

sj
 
Steve, I haven't been keeping up on what airplanes you own now, so I'm not sure what serial block your 180 falls into. However, I seem to recall you've got an O-470 A, so I assume it's an early one.

If it falls in to the serial number block 3000 thru 180051063, which I'm fairly certain it does, you...

...will not have a forward fuel pick up in either tank.

So, watch out while you're taxiing. :D
 
TJ, smart aleck!

NO. I just take every chance, and they're rare, to correct Mike V.

:D

Steve, that had to to with ice building on the funky rubber vent deal. They want you to put a later style vent behind the lift-strut/wing junction.

DMC :peeper
 
Man, there goes Dave pickin on me again, just because I made a dumb comment :lol: . At least I knew they had pickups in the back 8) .

Sumpin wrong with the picture which Mr. Steve describes, though.

Steve, I'm betting you looked pretty cool, taxiing right up to the gas pumps with the tail up in the air?? :angel:

MTV
 
Steve, If you really want to know what's going on in the tank, pull the plate on top of the wing that holds the cap and look in the tank. I had to check for wrinkles by doing that a long time ago.
Marty
 
Steve Pierce said:
Wasn't there an AD or SB on the fuel vent on the early C180s also?

There's an AD that requires a placard on the panel if the vent is still on top of the fuselage, and requires that the vent be moved to behind the strut (like the later Cessnas) when the left bladder is replaced. This is in response to the vent's propensity to ice up and plug when flying in conditions conducive to ice accumulation.

My 180 still has the vent in the original spot (above the cabin), so at some point in the future I'll be looking at moving it to the wing behind the strut. (Hopefully not too soon, as I hate replacing bladders!!)

Joe
 
It was about 50 degrees, so I doubt ice was involved. I suspect mine is in the old spot also, but maybe not.

sj
 
mvivion said:
I thought that 180s have a pickup in front and back of each tank. They surely have a pickup in the back of each tank...

Steve and MTV,

Actually, they don't have a pickup in the back of the tank on the early 180s. Steve, your airplane (like mine) has the early "tapered" tanks. They have a single fuel outlet that's neither in the front or back of the tank. It's about halfway in between (maybe a little toward the back). This is the reason there's so much "unusable" fuel for any attitude. If the airplane is nose up or nose down there will be a considerable amount of fuel in the tank that can't get to the pickup. (In level flight you can get pretty much all of it, but you can't climb, dive or taxi). Bigger tires will aggravate this situation to a certain extent, as the deck angle on the ground will be greater so as to have more fuel trapped "below" the pickup.

When one tank is empty (or at least empty enough so as to not flow fuel in the three-point attitude) it won't work to run on "both" because the fuller tank will simply be pushing fuel through the fuel valve into the emptier tank. This could ultimately lead to a situation where the tanks would equalize to a condition where neither would flow fuel to the engine. So if you're running with only one tank able to flow fuel to the engine, stick with that tank even during taxi.

The bottom line on these tanks is that you don't want to run them super low on fuel, as you could get yourself into a situation where the engine may starve for fuel during a steep decent or on a go-around. (If they starve during taxi they will definitely starve on a go-around!)

Joe
 
Joe, thanks for the explanation, but do you think that 13 gallons in one side is "super low"? Seems not that low at all since that is more than 30% of the tank capacity.

sj
 
Not sure if the system works like this but if you have a blocked vent line the bladder tanks can lift and trap or make you believe you have more fuel than you do. (This happened to me in an M model Bonanza years ago.)

Check the vent lines as well.

Brent
 
Joe, Not to be contrary, but don't you think the fuel would flow to the carb before flowing further uphill to the opposite tank?
Marty
 
I understand what Joe is saying. I agree.

Last night I was thinking about this and remembered a story I heard awhile back something like what Brent said.

I heard of a guy who flew for hours and never saw the sight gauge move off of full. He even ran a tank dry and saw no movement. Until then, he thought it was pretty cool the range this 180 Cessna airplane has.

Well, a clogged vent had caused the bladder to collapse, from the bottom up, and was holding the guage float to the top of the wing. When he opened the fuel cap he was looking at the bottom surface of the bladder sucked right up to the filler area.

If your present mechanic hasn't had a good look at the inside of those bladers, maybe it's time.
 
JNorris,

Thanks for your description! Not sure it fits Steve's problem, but it fits, and explains what is happening with my tanks (1953 bird).

Upon initiating a descent at cruise power, I have lost power on a tank that I am intentionally running dry - and later that day have found useable fuel in that tank in level flight. But this is only about 2 gallons or so - based on remaining fuel burn time.

Separately, some fuel is getting through the gas valve from a full tank to the empty tank also, (when not on Both) because I find I can get a few minutes out of a tank that I have run dry the previous day.

And yes, in cruise I run tanks individually, for fuel state knowledge, and maintaining light weight (30 gallons of total capacity is enough for local flight).

Steve, something does sound fishy with the venting system from that tank or the gravity feed line from that tank if you are fuel starved with 13 gallons remaining (15 being a half tank).

Bob Breeden


www.AlaskaAirpark.com
 
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