Ever Run a Tank Dry In Flight

[BrianNC]

Pelican's Perch #7: Run That Fuel Tank Dry!

John Deakin

 

http://www.avweb.com/news/pelican/182044-1.html?redirected=1

[kmyfm20s]

Back on topic. I fly 4.0 hour legs, switch every hour and always land with significant reserve (IFR, too). I see no reason to run a tank dry and ever let an engine stop. It serves no purpose.

 

That will serve you well until the unexpected happens. I would feel foolish totalling a plane or injuring passengers because I felt like I had to land a plane early thinking I had a dry tank when in reality I didn't. POH useful fuel vs actual can be very different and knowing the what the actual is can save your bacon.

I had an interiesting thing happen to me and lucky for me it was when I was shutting down my plane and I was on the ground. I turn my fuel selector to the off position when the plane sits. This particular time I turned it and it moved about an 1/8" and got stuck between the 2 tanks. In this position I was able to move it back enough to get it back to the right tank with a lot of force but it would move no further. If this had happen in the air I would be very happy to know my actual fuel available to plan for my safest option to land.

[Mooneymite]

.....This particular time I turned it and it moved about an 1/8" and got stuck between the 2 tanks...

 

This is exactly what I thought about on the two occasions that I intentionally ran my tanks dry...."What if the selector won't move when the engine stumbles?"  Landing off-airport with plenty of fuel in one tank hardly seemed like adequate compensation!

[kmyfm20s]

This is exactly what I thought about on the two occasions that I intentionally ran my tanks dry...."What if the selector won't move when the engine stumbles?"  Landing off-airport with plenty of fuel in one tank hardly seemed like adequate compensation!

That would be a bummer! My example works as an argument for both sides:) I wanted to know my actual fuel capacity so I ran the tanks dry in a safe glide distance to an airport. I now know the capacity and have not had the need to actually run them dry but can if necessary.

[Bob - S50]

In most instances this procedure would be unneccesary and a bad idea. When the fuel stops flowing the engine does NOT quit turning. Simply switching to the other tank should get it running again. Has anyone here ever got an engine to quit spinning while in the air? I tried a precautionary shut down once and the prop kept spinning. I even tried to slow the plane down enough to stop the prop but could not stop the spinning. I gave up on stopping it and landed the plane.

I am not worried about the engine not restarting.  I might be slightly concerned about an overspeed when it does.  By pulling the throttle back and the mixture to cutoff before I switch tanks I will ...prevent... an immediate relight.  I can then control that relight by setting a moderate airflow rate with the throttle and using the mixture to get the right mixture for that restart.  Once everything is under control and within limits I can then reset it for cruise.  Should only take a few seconds longer.

 

Thanks for the input though.

 

Bob

[Bob_Belville]

I (not intentionally) ran a tank dry in N6901N, a rented M20G, returning from KCSG to 8A6 in 1970. The restart was a non event but, since I had already run the other side to "E", getting the plane onto a piece of the earth that would be within reach of a 100/130 avgas nozzle before the "empty" tank was dry was a little more exciting. I grabbed the sectional off my passenger's lap, identified I26, spotted an airport (KEOE) and landed (long). We put 50.2 gallons in the 52 usable tanks. I've never trusted a fuel gauge since.  

[Bob - S50]

Back on topic. I fly 4.0 hour legs, switch every hour and always land with significant reserve (IFR, too). I see no reason to run a tank dry and ever let an engine stop. It serves no purpose.

 

Here is another good reason for running a tank dry from Mike Busch:

 

http://www.sportaviationonline.org/sportaviation/201204#pg26

[Rich]

Years ago, I had a 1987 "J" lean machine that I was flying from Statesboro, Georgia to Milwaukee, WI. No fuel flow instruments and I'd made a similar trip multiple times. This time it was different and my fuel gauges were lower than normal. I was planning on flying over the Chicago airspace. Just before this area, I was advised to "turn right direct to Brave intersection"- this is well out over Lake Michigan. I was at 6K' and said I wasn't comfortable with this. They told me to climb to 8K' and they'll route me more westerly (which didn't happen). As I continued, it became evident that my fuel takes were far lower than they should have been for the flight. I decided to run one tank dry. The engine stopped immediately- 20 minutes before it 'should have" but came back to life almost as fast when tanks were switched. I gave a low fuel advisory at which time ATC cleared me direct to my destination. Incidentally, in a few minutes, ATC advised me that a TSM was over my intended airport and to "say intentions". I changed destinations to Kenosha and got the instructions to call the tower. That all being said, I landed uneventfully (with 4 gallons left- I likely wouldn't have made Milwaukee), tower called ME, and was concerned that I had a problem.

 

As I understand it, the trash left in the bottom of the fuel tank can cause filter problems, so it might be best to avoid running dry intentially.

[Joe Zuffoletto]

I did it a couple times in my Encore but never in the Acclaim, nor do I want to.

 

First time in the Encore was near the end of a long XC flight. Intentionally ran the left tank dry to see what would happen and also how accurate the fuel gauge and annunciator light were. I was in the flight levels in glide distance to my destination. As soon as the engine stuttered I switched tanks. Took about 10 seconds to start running smoothly again (I didn't use the boost pump). Otherwise a non-event.

 

The second time was unintentional after I added a new fuel totalizer. Thought the totalizer was dialed in after 10 test flights but it wasn't. It said I had 17 gallons onboard (both tanks) but I really had 3. Fortunately I landed safely 5 minutes later. I've posted here about that episode before. Haunts me still.

 

Now I have a bird with great big tanks and I don't ever plan to land with less than 20 gallons useable onboard!

[kerry]

I do it every cross country flight.  As soon as I switch tanks it fires right up.  It seems no different than leaning the mixture and engine starts to sputter.  Advance the mixture and it smooth out.

[Hank]

 

As I understand it, the trash left in the bottom of the fuel tank can cause filter problems, so it might be best to avoid running dry intentially.

If that's a real issue, stop flying in any turbulence, especially with low fuel levels (less than 1/4 tank or so), to keep the trash from getting mixed up with the fuel as you bounce along. Look at your wings, they (and the fuel) bounce much more than the fuselage. Also drain your tanks, remove the sump fittings and clean out the trash so you can safely resume normal flight operations.

[David Brown]

I never ran one dry, but did test the gauges.  Waited for the "dummy" light to come on, saw where the fuel gauge needle was, then ran till gauge read "0".  I learned a few things.  My gauges are accurate at empty, but not when full.  I have 3 gallons of useable fuel left after the dummy light comes on.  I never want to see the dummy lights come on during a flight, but if one does come on, I know what minimum fuel I have.  See no need to run one empty. 

 

Bob, with all due respect, you have not really achieved anything other than know how much fuel you have until the light came on, and if that is your end stop, you need to do that at least once a year, how do you know it is staying accurate? Also, you believe you have 3 gallons left, and that is an assumption based on what the book says.

 

The assumption based on what the book says and a stubbornness not to run tanks dry has killed pilots before. Assume nothing. Until you do, you DO NOT KNOW. 

[David Brown]

If you're bored, don't read it.

 

I have not yet done so but I plan to run both tanks dry on separate solo flights or with one of my partners (not with my wife on board).  We have an FL202 digital fuel gauge and I want to see two things: 1) Will the gauge get all the way to zero before the engine quits and 2) assuming it does, how long will the engine run after that before it quits?  Based on draining the tanks for calibrating the gauge, and how much we got out of the sump after the boost pump quit pumping, I'm thinking it may run up to 5 minutes after the gauge says zero.

 

My POH says for an Air Start I should: 1) Prop full forward 2) Switch tanks 3) Mixture cutoff 4) Check fuel pressure (boost if needed) 5) Throttle 1/4 open 6) Mags both 7) Mixture slowly toward rich until it starts 8) re-establish power settings.  However, I think for reasons mentioned above I'll probably switch #2 and #3.  However, from a 'flow pattern' point of view which I've grown accustomed to in my line of work it might make it easier to flow left to right and top to bottom twice like this: Throttle 1/4, Prop forward, Mixture cutoff, Tank switch, Pressure check/establish, Mags both, Mixture advance, Power set.  I don't see that it would hurt anything to do it in that order.

 

Bob,

 

PLEASE……PLEASE x100 DO NOT follow the POH in this instance.

 

Think this through, the fuel runs out 'now"…..lets assume you do nothing for 5 seconds, the lines are clear from the valve, the prop is still turning, mags are turning and plugs are sparking, the air intakes are still delivering the same air, the ONLY thing that changes was fuel at the injector nozzle or carby bowl. Fix that and she will run.

 

Flick the pump on for a second or two to speed the process up if you wish. If you do not touch anything it will relight. If you monkey with anything, you will then need to set WOT/RPM at full or close to it/sweep the mixture from ICO to full rich and back again slowly until it relights.

 

The POH has lots of good information about many things, but anything engine related needs careful critical thinking before simply swallowing it. 

[David Brown]

Lets deal with a few concerns, the trash in your tank…..

 

Trash: if you are worried pull the fuel drain out and flush fuel through it, wriggle the airframe, see what you can get out. After that whatever remains is going to still be there at the bottom of the tank regardless of level. The fuel pickup is not just the end of a 1/4" pipe and easily blocked, it sits above the bottom of the tank and if it was going to clog up, it would have by now. The fuel filter is there to actually filter, so it will do its job anyway, and it will not be subject to any more or less debris as you run the tank dry.

 

Restarts: Covered in the post above

 

What If's: This particular time I turned it and it moved about an 1/8" and got stuck between the 2 tanks… above Then what happens when you change tanks one day and that happens with 3/4 full tanks all round. No you have an out landing to do…..and a LOT more fuel on board   Best you stop finding excuses not to do things and keep the maintenance up to your plane 

 

Fuel in the exhaust: Most of us fly LOP in the cruise, if there is any fuel that makes it past the engine in a few cycles before the restart, it will be so lean that the mixture can't fire anyway. Non event. If you are full rich and lots of fuel in there it might be possible. Hence the don't touch anything.

 

This is a big non event, it was SOP for piston airliners and should not spook you guys.

 

Thanks to Brian NC for posting the link to Johns article, like all his articles, a great read! 

[kmyfm20s]

 

 

What If's: This particular time I turned it and it moved about an 1/8" and got stuck between the 2 tanks… above Then what happens when you change tanks one day and that happens with 3/4 full tanks all round. No you have an out landing to do…..and a LOT more fuel on board   Best you stop finding excuses not to do things and keep the maintenance up to your plane 

 

 

I think you read my post to fast, I'm in favor of running the tank dry! I do maintain my plane and that was my argument, in the event that something unforeseen happens such as a malfunction in a well maintained plane occurs...or maybe I'm misunderstanding you.

[John Pleisse]

Here is another good reason for running a tank dry from Mike Busch:

 

http://www.sportaviationonline.org/sportaviation/201204#pg26

 

Doesn't sway my point of view.  I am not a Bush fan. The article begins with  Mike's usual qualification...... "In my 45 years of aviation experience....."

[jetdriven]

He said he dorsnt usually write about experimentals because his 45 years of experience is in certified aircraft. Do you have. A point to make?

[DrBill]

I do it perhaps yearly to check calibration of the fuel totalizer and just to run the tank dry.

Not a big deal. Engine never really stops just gets rough for about 15 seconds.

BILL

[Bob - S50]

As I understand it, the trash left in the bottom of the fuel tank can cause filter problems, so it might be best to avoid running dry intentially.

 

Why would trash in the bottom get sucked up when there is little to no fuel flow when it did not get sucked up during normal operations?

 

The feed line does not connect to the bottom of the tank, it connects to the side of the tank in the cockpit, thus the 1.25 gallons of 'unuseable' that should remain when it flames out.  That would be a lot of trash to reach that high.  Its the trash that is floating in the fuel you have to worry about, not the stuff that has sunk to and stuck to the bottom of the tank.

 

Your sump drain is at the low point of the tank, any loose trash should come out when you check the sump for water.

 

Even if trash does get in the line, prior to flight it should be flushed out when you check the gascolator.  If it happens in flight, the gascolator has a filter in it.  If it gets past that the servo (injected engines) has a filter in it... I know, ours was filthy because the plane sat so long before we bought it, we actually did have trash that made it that far during normal operations.

 

I'm more interested in knowing more precisely when I'm actually out of gas than I'm worried about trash in the tank.  However, we are all entitled to our own opinions.

 

Bob

[jetdriven]

Precisely. That "trash in the bottom of the fuel tank" is an old myth that never dies. It doesn't hold true for automobiles and it doesn't hold true for aircraft.

Let me ask you this. Is your aircraft airworthy with trash in the fuel tank?

[Bob - S50]

Doesn't sway my point of view.  I am not a Bush fan. The article begins with  Mike's usual qualification...... "In my 45 years of aviation experience....."

You may not like him, but if you'll take the time to read the article, you'll see he cites an actual case where a pilot died when he ran out of fuel when he thought he still had fuel remaining.  Like almost all accidents, it was caused by a sequence of events, any of which had they not occurred, would have prevented the accident.  It was caused him ferrying a plane that was not his, with inop fuel gauges, reliance on a fuel totalizer instead, a wing that allowed trapped air in one tank that made the tank look full during fueling when in fact it was not, and his personal habits for fuel management.

 

So what can be learned from his article?

 

1.  Don't count on a fuel totalizer to know how much fuel you have.  If you give it a wrong starting point it will give you a wrong end point.  Not mentioned in the article but still true, a totalizer will not indicate fuel lost due to venting or leaks.

 

2.  Make sure your gauges work!  And what good are they if they are not accurate?  Since they are only required to be accurate when empty, how do you know they are accurate unless you test them?  How can you test them without draining the tank?  You can do that on the ground or in the air, your choice.  Easier in the air, safer on the ground.

 

3.  Get accurate fuel sticks.  Know how much is in your tanks before you fuel.  Figure out how much you need to add and add that amount.  Stick the tanks again and see if the sticks indicate what they should.  If they don't, figure out why.

[John Pleisse]

You may not like him, but if you'll take the time to read the article, you'll see he cites an actual case where a pilot died when he ran out of fuel when he thought he still had fuel remaining.  Like almost all accidents, it was caused by a sequence of events, any of which had they not occurred, would have prevented the accident.  It was caused him ferrying a plane that was not his, with inop fuel gauges, reliance on a fuel totalizer instead, a wing that allowed trapped air in one tank that made the tank look full during fueling when in fact it was not, and his personal habits for fuel management.

 

So what can be learned from his article?

 

1.  Don't count on a fuel totalizer to know how much fuel you have.  If you give it a wrong starting point it will give you a wrong end point.  Not mentioned in the article but still true, a totalizer will not indicate fuel lost due to venting or leaks.

 

2.  Make sure your gauges work!  And what good are they if they are not accurate?  Since they are only required to be accurate when empty, how do you know they are accurate unless you test them?  How can you test them without draining the tank?  You can do that on the ground or in the air, your choice.  Easier in the air, safer on the ground.

 

3.  Get accurate fuel sticks.  Know how much is in your tanks before you fuel.  Figure out how much you need to add and add that amount.  Stick the tanks again and see if the sticks indicate what they should.  If they don't, figure out why.

 

 

Pilot error is inevitable...suggesting you run a tank dry as the best and only means of assuring it doesn't happen, is not assurance.

[David Brown]

 

 

Pilot error is inevitable...suggesting you run a tank dry as the best and only means of assuring it doesn't happen, is not assurance.

 

Nobody suggests it will stop you running a tank dry due to pilot error. What it does do is prove you have what you think you have.

 

Knowing exactly what you have is important. Human Factors training will tell you about the decision making process, and it goes downhill with stress and fuel issues when weather or runways closed or other things get in the way just adds to that. Performance goes south as a result.

 

Nobody we know of has died or even crashed from running a tank dry in a controlled manner. The opposite is true. 

[David Brown]

I think you read my post to fast, I'm in favor of running the tank dry! I do maintain my plane and that was my argument, in the event that something unforeseen happens such as a malfunction in a well maintained plane occurs...or maybe I'm misunderstanding you.

 

Sorry…I was doing a generic objections list, like an FAQ but different, and I was leveraging off your comment about fuel taps. This is a common objection. Was not aimed squrly at you just those who go on about but what if my tap seizes…..

 

Cheers

[phecksel]

I can tell you that an O-360 at WOT, leaned for peak power in a race, at a headwind busting altitude makes a loud sphincter tightening bang when the tank runs dry   Co-pilot who's one single job was to keep on eye on the clock and remind me to change tanks got an earful after that.