Backcountry Pilot • Fuel management and switching tanks

Fuel management and switching tanks

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Fri Feb 25, 2011 7:30 pm

Re: Fuel management and switching tanks

nmflyguy wrote:I can see the argument that if you're down to a handful of gallons of gas, splitting it between two tanks is not as good as having it all in one tank ... but as MTV pointed out, intentionally getting down to just a couple of gallons of gas in the tank is a bad idea anyway. Always land with a minumum of one hour of reserve fuel at your alternate destination - a half hour in each tank is best. If your fuel tank ports are going to uncover in the landing pattern with just a half hour fuel in them, then you need more than an hour's reserve at the end of your flight.


In a perfect and easy world I agree... But.

Lots of reasons why you push up to those fuel reserves, and into them. Headwinds, field going IFR and long hold time, emergency shutting the airport down, etc. Lots of reasons. And what do you do? Declare an emergency because you have an hour's worth of gas left? They frown on that. And there are plenty of places to fly to where you reach a point of no return, and have no legitimate alternative.

Test your fuel flow from all your tanks/selectors early in your flight so you know they work. Then it's manage your fuel best you can. And running a tank dry is a legitimate part of that management. It does you no good to have a collection of one, two, three gallons scattered here and there in different tanks. Empty them out as you near the end of your supply, and save the most for last in one spot.

Gump
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Fri Feb 25, 2011 7:49 pm

Re: Fuel management and switching tanks

mtv wrote:, ONE HOUR fuel remaining is mandatory as far as I'm concerned.MTV


I'm with you here Mike!!!!
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Fri Feb 25, 2011 7:59 pm

Re: Fuel management and switching tanks

Of course sometimes shit doth happen....

GumpAir wrote:There I was...

About 15 years ago I was working as a deputy sheriff in Northern California. A work buddy of mine was shopping for a new car, using our credit union to find the best wholesale deal around and set it all up. It all worked out, and in a very short time found the right car for him down in Lancaster, which was about 12 hours driving time away.

I got the proverbial, "Can you fly me down there?" phone call and of course said, "You pay for gas and breakfast" and we'll be good to go. So, on a cold and foggy October morning we launched off from KSTS in the Comanche 260 I had at the time and climbed into the crud. About an hour into the trip we broke out of the gray, and for the rest of the flight had a smooth, sunny flight down the valley, over the rocks, and into the desert.

I hung around while my buddy did the deal with the car dealer, and once he was set, we headed back to the airport for breakfast. I had more than a few cups of coffee, and at the time thought this probably wasn't the wisest thing to do, but what the hell, it's only two hours back home.

I filed, gassed up, and off in the air I went, opening a very simple IFR flight plan for the trip home. All was well until about Concord. The fog wasn't lifting at KSTS and approaches were now stacked up about ten deep. It was also about this time that I was noticing that all those cups of coffee were making things rather uncomfortable.

I had some choices to make. Ask approach for the LDA into Concord so I could pee, or keep mushing on towards STS and hope for the best with the bladder situation. Mush on I did, and I joined the happy crowd making turns in the clouds above Santa Rosa.

By this time bladder situation was critical. I had probably an hour to go before it was my turn for the approach, and about 15 microseconds left of bladder control. Of course I had no sic sacks in the airplane, no one every flew with me that got airsick. Peeing in my pants or on the floor of my airplane sounded pretty damn good at that instant, but wasn't going to happen. So that left only one choice...

My beloved ceramic extra large Mickey Mouse coffee mug that I had had since I was a kid. Still full of now cold coffee. My microseconds of control were fast approaching the spurt in the pants stage, so cold coffee got chugged as fast as I could, seat belt off, pants undone, skivvies dropped and aim into the cup and let loose.

Was working like a charm, relief that felt so good. Then the engine quit.

I was feeding off the right tip tank, and knew time wise I was getting close to empty, but got distracted with the hold and pee issue.

So there I sat. IFR conditions, dead engine with the prop windmilling. My pants down around my knees. And my dick in my hand. All I could do was just sit there and laugh out loud. What would the investigators make of this accident scene? They'd be scratching their heads for years.

First things first... I finished peeing, switched tanks and got the engine making noise again, then pulled up my pants, and proceeded to work my way back home.

Like the guy said above, probably more airplanes wreck from full bladders than anything else.

Gump
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Fri Feb 25, 2011 9:23 pm

Re: Fuel management and switching tanks

hey Gump, I know of at least one incident where a big off road dump truck rolled over out in the boonies of Alaska, the driver was seen staggering around the wreck with his pants down around his ankles. Seems he had been thinking about his girl friend and re living some of his best nights, at the crucial moment he lost concentration and woopsie daisy. [-X Hey stuff happens when you are having fun right #-o
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Fri Feb 25, 2011 9:28 pm

Re: Fuel management and switching tanks

I think that's the "Half Mile Club" that old Coyote Ugly was talking about earlier!!!!! :twisted:

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Fri Feb 25, 2011 9:33 pm

Re: Fuel management and switching tanks

Oh forgot to mention, We were in a buddy's Commanche and he was circling over some very large septic ponds just out of Vegas when everything went silent, big pucker factor as we were not very high, pump picked up fuel and off we went again. He had been planning to run out the tip tanks and then continue on the mains and he did. :shock:

I also rode a super cub to a forced landing due to a broken fuel selector. We had plenty of gas in the other tank just couldn't get to it. :x

I don't know what is best but for me I run 1/2 hr on each tank read off the hobbs meter. If on a long trip I will run 1/2 off one tank then run the other empty and switch back to the first one. To each his own.
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Fri Feb 25, 2011 9:45 pm

Re: Fuel management and switching tanks

shorton wrote:I also rode a super cub to a forced landing due to a broken fuel selector. We had plenty of gas in the other tank just couldn't get to it. :x


That's what happened to me. I was riding in back with a buddy in our boss's Super Cub. We took off out of Wainright, and were f**king around the tundra getting a real close look at some bears :roll: when I made the comment, "Think she'd probably like us to crash here so she could eat us." I no sooner said that, when the engine quit.

Glenn had run the tank dry, and when he went to switch tanks (with lots of fuel in the other) the selector wouldn't work. So we rode it in, which was a non-event, and pulled gas out of the full tank into a can to load into the working one. Boss wasn't happy with us.

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Fri Feb 25, 2011 10:34 pm

Re: Fuel management and switching tanks

In the S-7S, at least mine, I have NO selector valve for the dual wing tanks, if I did, I would remove it. They both feed into the 3 gallon header tank. The wing tanks and the header all have sight gauges, and when NO fuel is visible in the mains sight gauges (assuming I notice when the last of the fuel is visible in the sight gauges), I have an hour at cruise before I see air in the top of the header tank sight gauge, then I have another hour in a pinch or a good 45 minutes at normal cruise.

The header tank tapers so it is 100% usable, and I can see that last 1/2 pint slowly go..... and when NO fuel is visible in the header tank sight gauge, I re-aquaint myself with the 11 gallon aux tank: it has a panel mounted on/off valve and electric transfer pump (into the mains). Once, to see what would happen, as in how long it would take to re start a totally empty fuel system once I started transfering fuel from the aux tank, I ran it ALL dry. About 20 seconds before the engine died, the fuel pressure gauge got hinky, and about a second after going to the aux tank I had normal pressure and performance. I thought it may take longer but it was pretty much instant.

I like this system, I can "run out" of fuel a few times while still not really running out, I have several cues a landing may be a good idea in an hour or two, and the entire time I can SEE exactly what the hell is going on. In real life use I of course pump out the aux tank while I still have a half hour or so in the header tank rather then wait, just in case the aux tank pump didn't work for some reason. This has been the simplest and best fuel system I've ever had, so if I ever run dry I have NO excuses! 32 gallons usable and at most 4 GPH, usually less, 2.5 to 2.0 GPH at 65 MPH, and yeah I have a Porta John!
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Sat Feb 26, 2011 3:04 pm

Re: Fuel management and switching tanks

So whats the typical cruise speed of the rans s7, normal load at 4gph? I,m assuming it's the 912 rotax? Sounds like a great airplane.
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Sat Feb 26, 2011 3:38 pm

Re: Fuel management and switching tanks

GumpAir wrote:I think that's the "Half Mile Club" that old Coyote Ugly was talking about earlier!!!!! :twisted:

Gump


Here is an excerpt from NTSB #SEA86FA248

THE UNICOM OPERATOR AT BOULDER CITY MADE RADIO CONTACT WITH '81J' AT ABOUT 2300 PDT, AFTER HEARING AN ACFT MANEUVERING IN THE AREA. THE PLT STATED HE DID NOT PLAN TO LND AT BOULDER CITY, BUT SAID HE INTENDED TO FLY 'UP THE VEGAS WASH' AREA. AT APRX 2300 TO 2400, WITNESSES NOTED A LOW FLYING ACFT THAT WAS 'BUZZING' A BOAT, CAMPERS & VEHICLES IN THE AREA OF VEGAS WASH & THE OVERTON ARM OF LAKE MEAD. AT ABOUT 1000 THE NEXT DAY, THE WRECKAGE WAS SIGHTED ABOUT 150 FT BELOW THE CREST OF A 1622 FT MTN, EAST OF THE OVERTON ARM. TOXICOLOGY CHECKS OF THE PLT'S & PASSENGER'S BLOOD SHOWED ALCOHOL LVLS OF 0.18 & 0.14 MG% (0.18% & 0.14%), RESPECTIVELY.

" Local authorities removed the bodies from the wreckage.
Investigators said local police reported that, as evidenced
by the position of the bodies and certain injuries to the
pilot, the passenger was performing an act of oral sex at
the moment of impact. The pilot was missing his penis, and the
Coroner found it in the passengers throat." Passenger was female.

The Mile High Club is fun, but let's not join this version of it.
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Sat Feb 26, 2011 7:55 pm

Re: Fuel management and switching tanks

Man, this thread's taken an ugly turn :D

One point of clarification: I said I always want one hour of reserve fuel. Note that this is a PLANNING issue: I plan the flight to provide one hour of fuel at my destination. As Gump says, sometimes shit happens, and you cut into that reserve. That's why 1/2 hour isn't enough for this kid.

MTV
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Sat Feb 26, 2011 8:22 pm

Re: Re: Fuel management and switching tanks

mtv wrote:Man, this thread's taken an ugly turn :D

One point of clarification: I said I always want one hour of reserve fuel. Note that this is a PLANNING issue: I plan the flight to provide one hour of fuel at my destination. As Gump says, sometimes shit happens, and you cut into that reserve. That's why 1/2 hour isn't enough for this kid.

MTV

I second that, I try to always have 5 gallons in each tank through planning.
I have run both tanks out (not at same time) to test flow and they will run to about 1/4 gallon remaining but I still don't like to go lower than 5 gallons.
I'm also paranoid about sumping my tanks, I do it before every flight even if it has only sat for an hour and any time I have added fuel, saw that almost get a guy once, don't assume the FBO tanks are water free.


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Sat Feb 26, 2011 8:37 pm

Re: Fuel management and switching tanks

Well here is something I haven't read from anyone else on this post so its up to me. Two wing tanks on the 701 and one 5 gallon header tank which they drain into. No L R selector. The first time I ran the wing tanks dry into the header was no problem. Still had 5 more so I just landed and filled up. Didn't know much about the airplane yet so I did not realize I would have to hold the fuel line petcock drains open long enough to get all the air purged and a solid flow of gas from the drop line between the wing tanks to the header. Next flight after the 5 gallon header went dry there was an air lock waiting for me in the lines from the wing tanks that prevented fuel from either tank making its way down into the header tank. With the wing tanks full and the header empty I proceeded to make a dead sticker in a rolling stubble field next to the neighbor below who was working his cattle. He thanked me for cutting my engine before landing as not to spook his cattle in the corrals. The considerate fellow that I am.
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Sat Feb 26, 2011 9:36 pm

Re: Fuel management and switching tanks

In my RV-4 you could only run off one tank or the other. Standard practice for me on local flights was take off and land on the left tank, fly on the right tank. On cross countries I would run of the left tank for one hour, the right tank for two hours, then look for a place to land because I usually needed to stretch and take a leak after 3 hours. I did run the right tank dry once inadvertently on my last trip back from OSH. It got my attention for sure. Boost pump on, switch tanks, prop was still windmilling, engine fired right back up. I paid closer attention to my flight timer after that.
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Sat Feb 26, 2011 10:24 pm

Re: Fuel management and switching tanks

avi8ter wrote:So whats the typical cruise speed of the rans s7, normal load at 4gph? I,m assuming it's the 912 rotax? Sounds like a great airplane.


94 mph indicated with the 912S, but I usually go a bit slower, 85, that'll get the fuel flow down to 3 1/2.
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Sat Feb 26, 2011 11:22 pm

Re: Fuel management and switching tanks

Very nice economical cruiser.
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