# Do you regularly run tanks (aux) dry?

#### SixPapaCharlie

##### May the force be with you
I have a plane that has Aux tanks. Each holds 15 Gallons. I plan 15 GPH for every flight knowing I burn more like 13. I like buffers.
I have flown with a 2 people this week that both mentioned running the aux completely out then flying on the mains.

Generally when I run a tank dry, it is as much a surprise to me as it is other people in the plane. Running the aux dry, I get means there are 2 less tanks to question regarding the volume but even the one time I did it on purpose, I still have 5 seconds of elevated blood pressure and a slight shock. But the engine has started again and all is good.

How many of you run your aux tanks dry regularly? I like the idea of knowing I don't have to do that *weird pilot math on those tanks but I don't like the part where the engine gets jittery at the end.

*Worst case scenario, I know there is "some" fuel there if I need it but could be a minute. Could be 30. Gauge reads zero-ish though.

Does your plane have a fuel pressure gauge? Flow meter? Something like that could give you a few seconds warning before the engine goes quiet.

Does your plane have a fuel pressure gauge? Flow meter? Something like that could give you a few seconds warning before the engine goes quiet.
Legally, it has a fuel pressure gauge but realistically.... You know how if you flap a pencil loosely between your fingers in front of your face and it looks like it is bending? It has a similar level of accuracy.

Depends on how much I am pushing my fuel range.
running them to 13 means you probably have 20 minutes of fuel you aren’t using and is split between two tanks. One way to look at it, this fuel is available if you inadvertently run the mains dry, But it is only 10 minutes of fuel per tank, or is it?

The other way to look at is, wouldn’t you rather have that 4 gallons (20 minutes of fuel) in the main tank that you will be landing on, I would hate to run out of fuel during the landing sequence, have to switch to an Aux tank that may or may not have 10 minutes of fuel it it.

Running it dry or close to dry lets me verify my fuel burn. I don’t usually really try to run them dry, but I will try to run them very close to dry. If I am burning more than I think it will sort of surprise me, but it is usually close enough I am watching the fuel pressure and can switch before the engine actually stops.

I also, when possible try to time the near dry switch from the Aux tanks to when I am over friendly terrain/airports.

Brian

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Luckily I don't have the trade fuel for luggage problem. 84 gallons @14gph (LOP@12) gives me 6 hours air time. My bladder limit is 4.

I have run the auxiliary out exactly twice. Once was prepared for it. The other took me by surprise after upgrade and was putting too much faith in the 1960's style boat sender and not the fancy new totalizer.

The one thing I'd like Dynon to do would be allow me to put a timer on each tank. It helps when there's 4 and would be a crosscheck to the senders.

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When I flew my Yankee, I regularly ran the left tank dry. The fuel gauges were very accurate, my fuel flow meter would give me a minute or two warning before the engine stumbled and (due to the O-320) I was regularly flying it near max range.

I had this fear that my fuel calculations would be right (4 useable gal reserve), but because I switched tanks early I would get delayed on landing by a 172 flying a multistate pattern and I would have 2 gal in one tank and go dry in the other too low to do anything about it.

I have a 206 with wing tip auxiliary tanks which hold an extra 15 gallons each. I do not use them in may calculations, at 15 gal per hr, full tanks give me over 7 hrs of flying. I am good for max 3 before I need to land and take a break. I have a g1000 and my fuel remaining number is always within a gallon of true. However, I do not depend on only the technology in my plane, I use observation as well. I keep track of my hours since last fill up, I always fill up to the tabs, when preflighting I check visually and with my trusty tube how much fuel I have, and never start a flight with no less than 2 hour reserve or 100 percent reserve whichever is more(so if I have a 3 hour flight I will make sure I have a full tank for a 3 hour reserve). I often do not have fuel in my auxiliary at all, why carry the extra weight, but will use them when I do overnights and the FBO offers discounts for ramp fees if you use their fuel, and my home base is cheaper for fuel.
I know I am being extra conservative, but making my plane a inadvertent glider will take the fun out of flying quite quickly.

The SF-260 was the only thing we ever ran the aux tanks dry on. It’s placarded against any acro with any fuel in the tip tanks.

Routinely on my lancair, but with a header tank feeding the engine running auxiliary tanks dry is uneventful.

Never.
If I want to verify fuel burn, I compare the totalizer reading with what goes back into the tanks. Pretty much spot on.

I've never run a tank dry.. but I'm a little superstitious. Now, I'll take it to a calculated 1/4 or 1/2 gallon if I have a totalizer... but I'm too chicken to wait for the wobble in the gauge.

One of the avwebbers (Deakins, Busch?) advocates running the tanks dry. I regularly run mine dry. It takes only less than a second of the engine sputtering for me to reach down and switch the tank.

Given the way the IO-550 (and my fuel lines work), the totalizer is great for total fuel, but since my auxes return to the main, it's hard to gauge how much you've drawn from them.
One thing I've never had explained to my satisfaction is why the fuel flow from the aux is HIGHER at very low power settings than at cruise. I can drain the aux tank in 20 minutes at idle.

By myself? Run the tanks dry.
With passengers experienced in that model and with my quirky predilections? Run the tanks dry.
With my wife or other passengers? No way.

I have a plane that has Aux tanks. Each holds 15 Gallons. I plan 15 GPH for every flight knowing I burn more like 13. I like buffers.
I have flown with a 2 people this week that both mentioned running the aux completely out then flying on the mains.

Generally when I run a tank dry, it is as much a surprise to me as it is other people in the plane. Running the aux dry, I get means there are 2 less tanks to question regarding the volume but even the one time I did it on purpose, I still have 5 seconds of elevated blood pressure and a slight shock. But the engine has started again and all is good.

How many of you run your aux tanks dry regularly? I like the idea of knowing I don't have to do that *weird pilot math on those tanks but I don't like the part where the engine gets jittery at the end.

*Worst case scenario, I know there is "some" fuel there if I need it but could be a minute. Could be 30. Gauge reads zero-ish though.

I've heard that running a tank dry can move debris into the filters. I don't know if that is an old wives tale, or if there is any truth to it.

Depends on the plane...I used to do it all the time w/a carbureted plane.

But now, with a fuel injected engine (adding low/high boost pumps to complicate matters), no uh uh!

I've heard that running a tank dry can move debris into the filters. I don't know if that is an old wives tale, or if there is any truth to it.
Unless you have stuff floating in the gas, it likely would be the first thing out of the tank not the last. If you're filling from above ground tanks or fuel trucks, you're not picking up much "debris" any how.

I guess I never thought about this aspect of the Maule fuel system. We don't run the engine on the aux tanks. There are transfer pumps to the mains. So we can always completely empty the aux tanks without worrying about the engine getting starved.

Depends on what you are comfortable with. Personally, I don't run fuel that close so I wouldn't try it because it wouldn't matter. If a flight turned into some type of emergency where I needed every drop, then I would probably go back and empty the tank. But I don't see that happening for me.

Running a tank dry = running a fuel pump dry.

I use powdered fuel so my tanks are always dry

Does your plane have a fuel pressure gauge? Flow meter? Something like that could give you a few seconds warning before the engine goes quiet.
That's a good way to do it, even in aircraft with simpler fuel systems (e.g. a left and right tank). There are plenty of accidents caused by fuel mismanagement, and if fuel is getting scarce, having a couple of gallons here and a couple of other gallons there really complicates things. In a low fuel situation I'd rather have all my remaining fuel in one tank so I can focus on flying the plane.

Compare that with the number of accidents caused by running a tank dry. Can anyone think of one? I'm not aware of any.

- Martin

That's a good way to do it, even in aircraft with simpler fuel systems (e.g. a left and right tank). There are plenty of accidents caused by fuel mismanagement, and if fuel is getting scarce, having a couple of gallons here and a couple of other gallons there really complicates things. In a low fuel situation I'd rather have all my remaining fuel in one tank so I can focus on flying the plane.

Compare that with the number of accidents caused by running a tank dry. Can anyone think of one? I'm not aware of any.

- Martin
how many accidents happened because of "having a couple gallons here, a couple of gallons there"? probably zero, since clearly they had fuel. they most likely happen when knuckleheads don't plan properly and don't pay attention.

Compare that with the number of accidents caused by running a tank dry. Can anyone think of one? I'm not aware of any.
John Denver. But he put significant amount of effort into making sure that the outcome would be as bad as possible.

I have no problems with running a tank dry if I have altitude and am over terrain where I stand a chance in the very unlikely event that things go really wrong. But the 5-10 seconds it takes for the engine to catch does seem like a long time.

how many accidents happened because of "having a couple gallons here, a couple of gallons there"? probably zero, since clearly they had fuel. they most likely happen when knuckleheads don't plan properly and don't pay attention.
Knuckleheads or not - accidents do happen because of fuel mismanagement. I am not aware of an accident due to intentionally running a tank dry.

- Martin

...I am not aware of an accident due to intentionally running a tank dry.

- Martin

I mean, you're probably right. doesn't mean you'll catch me running tanks dry as a regular procedure. I did it once when I needed to run a tank dry for maintenance and it's not a big deal, you just won't catch me doing it on the regular. if you're a mooneyspace reg, and I'm assuming a beechtalk reg, you probably preach it as gospel.

Not running dry, you could have 12 gallons of fuel, but only 3 gallons in each tank . So it just depends on how tight one is running the fuel reserves.

BTW, if you run main dry on the Comanche, you'll find it doesn't hold 30 gallon but 28, hence the 2 gallons unusable.

I also fly a Comanche with aux tanks. I don't usually run the aux tanks dry, but I also don't plan trips where that extra 2-3 gallons per tank would make the difference. With full tanks that gives the Comanche 250/260 6 hours endurance. My butt and bladder are only about 4-5 hours max.

how many accidents happened because of "having a couple gallons here, a couple of gallons there"? probably zero, since clearly they had fuel. they most likely happen when knuckleheads don't plan properly and don't pay attention.
I have gone back to running a tank dry, or at least really close to it after my accident that occurred with low amounts of fuel in each tank. I want lots of fuel in one tank. I'd rather chance the tiny likelihood of an issue running a tank low with a bunch of fuel in the other tank, than having both "lowish". I had 8 gallons in my mooney when the engine quit. 4 per wing. If it were all in one wing, who knows, not that anyone knows what the issue actually was....

I run my auxes dry because I value "8 gallons in main" much more than "4 gallons in aux and 4 in mains" -- particularly when it's windy or turbulent out. My mains and auxes feed directly to the selector, so are separate fuel paths.

In singles with L/R mains, I will run a main dry under the same philosophy. I like to start on, say, L, burn down until it has an hour remaining, switch to R, burn it dry, and when I switch back to L, I know that I've already run it today (so it should work), and that it is time to start shopping for a fuel stop.

I use the fuel flow fluctuations as my switch point. It means I need to be vigilant for those last 5-10 minutes. If I'm busy, it's bumpy, or I am otherwise distracted, I will switch early since I consider that most safe, and the nuisance of split fuel loses to my workload needs

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Yes.

It was great fun being 20 miles from BF Alaska and have the engine go quiet. So I would turn to the passengers and scream in a little girls voice....''We're all gonna die.!!'' The looks on the passengers faces was priceless.!!

Ok, not really.

I never intentionally ran a tank dry, especially with passengers onboard.

and scream in a little girls voice....''We're all gonna die.!!''

That's not really necessary.

Just say, "Aw, crap! Not again!! C'mon, baby!" while beating the panel with your fist and surreptitiously switching tanks. When it restarts, a "Thank you Lord!" will enhance the effect.

That's a good way to do it, even in aircraft with simpler fuel systems (e.g. a left and right tank). There are plenty of accidents caused by fuel mismanagement, and if fuel is getting scarce, having a couple of gallons here and a couple of other gallons there really complicates things. In a low fuel situation I'd rather have all my remaining fuel in one tank so I can focus on flying the plane.

Compare that with the number of accidents caused by running a tank dry. Can anyone think of one? I'm not aware of any.

- Martin
That is also how I think. If I am running close on fuel, I will run tanks dry so that all the available fuel is one. But I seldom run that close. The closest so far was a trip from MD to FL on Christmas Day. I did not want to take a chance on landing somewhere and the pumps not working, so I ran on tank down to the low fuel light. If the other tank got low, I would have switched back and run it dry. But the wind gods took pity on me and I landed with a reasonable amount of fuel.

how many accidents happened because of "having a couple gallons here, a couple of gallons there"? probably zero, since clearly they had fuel. they most likely happen when knuckleheads don't plan properly and don't pay attention.

There have been a number of mishaps where the airplane crashed with the selector on a tank with no fuel, while another tank or tanks had fuel. That takes a special kind of stupid.

My favorite was an accident report where the guy filed that he had 7:20 of fuel on board. At 7:30 into the flight the engine quit. Too bad he wasn't quite at the airport yet. I gave him credit for nailing the fuel burn though.

Compare that with the number of accidents caused by running a tank dry. Can anyone think of one? I'm not aware of any.
I know of one where the handle broke right at the midpoint between the two selections. Unlike John Denver, the pilot managed to put it in some crops and then walk away.

And to answer the OP's question, I don't regularly run a tank dry mainly because I don't regularly fly a plane with more than 2 tanks. However, there was one time that for maintenance reasons I ran a tank dry and the other tank had more than VFR reserves. Saw the pressure and flow meters wiggle and then switched before the engine went quiet.

Do it all the time in the 414. By experience I know how long each aux will last at normal cruise power. When I get close, my right hand drifts towards the selector and I watch the fuel flow indicator. I can usually catch right when the fuel flow drops off and make the switch. Plane yaws a bit for a second and that’s it. I stagger switching to the auxes by about 10 minutes so there’s no chance of both engines loosing fuel at the same time.

I know of one where the handle broke right at the midpoint between the two selections. Unlike John Denver, the pilot managed to put it in some crops and then walk away.
That's a good reminder to work out a fuel strategy for each flight where the switching between tanks occurs while over landable area, ideally in easy gliding distance of a runway. It's a low probability that something like this would happen, but the impact can be severe.

- Martin

Not running the tank dry in cruise is essentially making the remaking fuel unusable. You won’t switch back to that tank later on an approach.

I always ran mine dry.

Just my preference.

The only wrong answer is running out of usable fuel.

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Yes, I run tanks dry on long cross country flights. I don't want to end up in a situation with a little bit of fuel in multiple tanks.

My Viking has 3 tanks: Left main, right main, and Aux. The mains in the wings each have 34.5 gal usable, and the aux tank between the rear seat and the baggage compartment has 15.

On long flights, I take off on one of the mains, run it to half, switch to the other main, run it to half, and then switch to the Aux and run it dry. Switch back to one of the mains and run it dry. That way all of my usable fuel is in the remaining wing tank, and I complete the flight on that tank.

I can get about 5 hours with an hour reserve with this strategy.

Sent from my iPhone using Tapatalk Pro

That's a good reminder to work out a fuel strategy for each flight where the switching between tanks occurs while over landable area, ideally in easy gliding distance of a runway. It's a low probability that something like this would happen, but the impact can be severe.

- Martin
We used to try to do this but we kept picking a field and running short of it. Of all the problems I've had on my plane with three different engines, I've never had it NOT restart in flight when you switched to a tank with fuel in it. It's a certification thing to support this.

Here's the AVWEB (it was Deakin) on the subject: