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My experience running a tank dry.

bsacks05

Well Known Member
Due to my impatience and boneheaded fuel expectations I managed to run a tank dry on a recent long cross country.

I knew the left tank was getting close to being empty but I thought it would get me another 10-15 minutes along before I switched to the right tank. I was about 20 minutes from home with rapidly diminishing daylight at 3500 ft. "The fuel in the right tank would be enough to get me home with reserves", was my thinking before the left tank went dry.

I did not think it would happen but suddenly the engine quit with the prop windmilling at a good clip. I was pretty quick to switch tanks and after about 3 long seconds the engine restarted. I don't remember if I pushed in the mixture and turned on the boost pump but was very relieved that the power came back on.

So...do I fly on, confident that the right tank would carry me through a darkening sky to my destination? No. I finally made a wise decision and diverted 9 miles to an airport I knew had SS fuel. I made it home later than I planned and logged some night flying and and a landing. I would have gotten home sooner if I had just topped off the tanks before I left in the first place. :(

Lesson Learned: After 11 years and 1100 hrs with my RV9, overconfidence, impatience, and complacency are real dangers. I'm glad this happened. It needed to happen and I am a better pilot for it.
 
Not sure that's necessarily a problem...

Suppose you're on a long flight burning a bunch of fuel from each tank. How do you know how much fuel you've got in each tank? And how do you know that you won't run one tank dry on short final or unport the tank if you slip the wrong way?

I've thought about this a bunch, but don't have a good answer. My "thoughts" are:
* Change fuel tanks five miles out, so you know that you're not about to run one dry on final. And that's still high enough that if there's a problem, you can go back to the other tanks;
* Or run one tank dry in flight, knowing then that the other tank has all the fuel reserves/

And let's face it, precise fuel management in an RV is more optimism than practice. Probably the best fuel burn numbers come from factory built airplanes with the same engine/prop combination, and that will give fuel burn per hour, but those numbers will need adjustment for climb, etc. And although RV tanks are relatively easy to fill completely, the wing ribs can act as air traps, so you may not get them exactly full.

And then there have been flights where the destination airport didn't have gas -- the credit card reader was inoperative, the fuel hose was stuck, or the gas vendor wasn't open on weekends. On long trips, I've gotten in the habit of planning to land with two hours of gas, and that means that if I have to go somewhere unplanned an hour away for gas, I can land there, still with an hour of reserves.

But there have been flights back to home base when the landing was planned with only an hour of reserves, night was falling, etc.

As they used to say on TV, be careful out there!
 
Grumman Trainer

While building my 9A, I purchased a Grumman AA1B with an O-320 and stock gas tanks. 11 gallons on each side and an 8 gal/hr motor flying around the middle of Nevada makes for critical fuel management. I got used to running a tank dry so that I knew how much time I had on the other tank. Like this:

Left 30 min - Right 30 min
Left 30 min - Run it dry (15-20 min more)

Right tank now has 30 min plus the run dry time.

One eye on the fuel pressure gauge when it is about to run out makes the swap without the engine stopping.

I have not used this technique in the 9A but I could.
 
On long range flights, I'm a proponent of running a tank dry so you know you've got all of your remaining fuel in one tank. No sense running both of 'em down to the "is one gonna unport in the pattern?" level.
 
Not sure that's necessarily a problem...

Suppose you're on a long flight burning a bunch of fuel from each tank. How do you know how much fuel you've got in each tank? And how do you know that you won't run one tank dry on short final or unport the tank if you slip the wrong way?

I've thought about this a bunch, but don't have a good answer. My "thoughts" are:
* Change fuel tanks five miles out, so you know that you're not about to run one dry on final. And that's still high enough that if there's a problem, you can go back to the other tanks;
* Or run one tank dry in flight, knowing then that the other tank has all the fuel reserves/
Agree- I've tried to run out a tank many times, doing the 5 miles out option then switch. Nice too see someone has ran a tank dry, I have not been able to yet. These RV's are fast and efficient!
 
Me too

I always run the left tank dry when on cross country and left hand pattern airports in the plan. On our -9, six gallons is another hour of flying but I'm looking for a place to refuel around 8 gallons.
 
On long range flights, I'm a proponent of running a tank dry so you know you've got all of your remaining fuel in one tank. No sense running both of 'em down to the "is one gonna unport in the pattern?" level.
I'm a proponent of always having an hour's worth of reserve fuel!! Just simpler, with less that could potentially go wrong that way. My typical longer stints are about 3 hours, which leaves closer to 1.5 hours reserve.
 
Running a tank dry is normal cross country ops for me. Many different airplanes, many different fuel tank configurations. I want to land with all remaining fuel in one tank.
 
Granted our RV's are not certified, but for those that still fly spam-cans....

The FAA said:
FAR 23.955(e) Multiple fuel tanks. For reciprocating engines that are supplied with fuel from more than one tank, if engine power loss becomes apparent due to fuel depletion from the tank selected, it must be possible after switching to any full tank, in level flight, to obtain 75 percent maximum continuous power on that engine in not more than -

(1) 10 seconds for naturally aspirated single engine airplanes;
(2) 20 seconds for turbocharged single engine airplanes, provided that 75 percent maximum continuous naturally aspirated power is regained within 10 seconds; or

(3) 20 seconds for multiengine airplanes.

I regularly run a tank dry. Did it as recently as 4 hours ago! Take off on one, climb to altitude (10.5-11L), switch to the other, and I have 165 minutes until I run it dry. Change back to the left tank and I now have 95 minutes until I hit my 45 minute reserve. Rotec TBI with an OX-340S. The engine stumbles, EGT's drop slightly, change tanks, a couple more stumbles then it's back to normal cruise power in less than 10 seconds.

If you plan on doing this brief your passenger first, unless you don't like them. They tend to get nervous when you get Fuel Quantity warnings in the headset and low level alarms on the EFIS...
 
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I'm actually surprised it took me this long with my RV to have my first experience with this. I've read posts in the past that describe it as routine and not a big deal for some RVers.

I guess its like anything else you experience for the first time. Your level of anxiety before you do it is disproportionate to the actual event which turns out to be no big deal.
 
Normal ops during my 135 days in Barons and twin Cessnas. Balance fuel to the last drop with boost pumps on then switch to the fullest tank for the approach and landing.
 
As a previous poster noted, in a carbureted engine you will see the fuel pressure drop before the engine quits. Then you still have what is left in the bowl. When you know you are close to empty on a tank just put the fuel pressure on a constant scan and swap tanks when it drops.
I don't like the idea of letting the engine cough or stall, but this method seems perfectly safe to me, and is what I do when fuel levels are tight.

You can safely measure how long the fuel in the bowl will last by ground running and shutting off the fuel selector. Keep your fuel pressure gauge scan to 1/2 that time interval.
 
Question...let say you were flying somewhere in a commercial airliner and all the engines went silent for a short perior of time. Then the Captain announces, "don't worry folks, we just ran our fuel dry in one tank. This is our normal operational procedure". Would you ever fly that airline again. Lots of things G.A. pilots can do that working professional pilots would never consider doing. Even though the risk appears minimal, aren't you creating the potential of a real emergency where one did not exist?
 
Question...let say you were flying somewhere in a commercial airliner and all the engines went silent for a short perior of time. Then the Captain announces, "don't worry folks, we just ran our fuel dry in one tank. This is our normal operational procedure". Would you ever fly that airline again. Lots of things G.A. pilots can do that working professional pilots would never consider doing. Even though the risk appears minimal, aren't you creating the potential of a real emergency where one did not exist?

It's a little different scenario when the fire goes out in a turbine....

But you still have a valid point, yes.
 
Question...let say you were flying somewhere in a commercial airliner and all the engines went silent for a short perior of time. Then the Captain announces, "don't worry folks, we just ran our fuel dry in one tank. This is our normal operational procedure". Would you ever fly that airline again. Lots of things G.A. pilots can do that working professional pilots would never consider doing. Even though the risk appears minimal, aren't you creating the potential of a real emergency where one did not exist?

I only have 250hrs as a PP, but I fail to see the logic in A. having an engine stop mid flight and B.unbalancing the airplane. It makes no sense to me.
 
Moot point

In these United States of America, there is never a reason to run out of gas. Bad planning or bad decision making will lead to it. If you get into your last hour of flight and actually worry about making it home, that?s bad planning or decisions.
I?m not saying don?t run a tank dry but if you feel you have to to make it home safely, land and get gas.
 
It would be my luck that the only tank with gas left in it would have a plugged vent......

I don't run a tank dry.
 
Question...let say you were flying somewhere in a commercial airliner and all the engines went silent for a short perior of time. Then the Captain announces, "don't worry folks, we just ran our fuel dry in one tank. This is our normal operational procedure". Would you ever fly that airline again. Lots of things G.A. pilots can do that working professional pilots would never consider doing. Even though the risk appears minimal, aren't you creating the potential of a real emergency where one did not exist?

I have been on several commercial flights where the pilot came on the radio and announced that we were diverting to a different airport because we do not have enough fuel - the passenger response is the same as what you are questioning. There were people on those flights who will tell that story for the rest of their life - about how they almost ran out of fuel and that the airline should have put more fuel onboard before the flight.
How the general public reacts to aviation is really irrelevant. There is nothing unsafe with running a tank dry as long as you do not let the engine quit or the fuel system become air-bound. Given the reliability of fuel gauges in the GA fleet I think it is adding safety to keep your last fuel quantity in one tank rather than split between two tanks. Here is why:
A 45 minute reserve is 6 gallons. That means 3 gallons per tank, which is in the red on my fuel gauge. That makes my passenger and me more nervous than anything to see both tanks in the red. I would much rather land with 6 gallons in one tank than assuming I have 3 in each but not really knowing for sure. It is less likely to un-port, and if I have to go-around and get distracted there is a good chance of running the one tank out while low & slow and not focused on the fuel gauges. When I go to fuel power on a go-around and fuel consumption goes up to 16gph, that 3 gallons turns into a 10 minute fuel supply (assuming it is exactly 3 gallons to start with). What if I really have 2 gallons in the tank I am using and 4 in the tank I am not?

Many will argue that a 45 min reserve is not adequate, and I do agree; however there are times when you are racing weather and darkness and other factors where it is much safer to land with a 45 minute reserve than to land short for fuel and add an hour to your trip. In those cases I choose to have all of the remaining fuel in one tank.
 
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I was once right seat in a Bonanza over central CA when PIC ran tank dry. He switched tanks, and went to work on the wobble pump, we lost maybe 1500-2000', and got down to a few hundred feet over flooded rice fields, all aboard was tightening seat belts, when finally he got a restart. His comment was "I don't know why that happened, it has always restarted easy for me".

Note to Self - Avoid running tank dry.
 
gotta agree

It would be my luck that the only tank with gas left in it would have a plugged vent......

I don't run a tank dry.
That would be exactly my concern - or a bit of proseal clogs something, or whatever. While the risk of running one tank dry seems low, the reward seems lower.
 
Put in a header tank and you can run both tanks dry routinely.
Seriously folks, you will never regret being too conservative with fuel planning.
 
If you've been switching tanks during the flight, why would you suspect that one tank suddenly would not feed? If that were a legitimate concern, then the only safe course would be to fly the entire flight on just one tank.

And as for the airline analogy... Jets have all kinds of automation in the fuel systems. By the way, back in DC-6/7 days, on very long range flights, they did indeed run the tanks dry in flight.
 
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And let's face it, precise fuel management in an RV is more optimism than practice. Probably the best fuel burn numbers come from factory built airplanes with the same engine/prop combination, and that will give fuel burn per hour, but those numbers will need adjustment for climb, etc. And although RV tanks are relatively easy to fill completely, the wing ribs can act as air traps, so you may not get them exactly full.
Well, I am sure each RV is going to be different. Given that, I most certainly cannot agree with this as a blanket statement about all RVs. I have been flying my 9A since 2010. I have been religious about measuring and calculating the fuel quantity and fuel burn of every tank full of gas in those 7+ years (as a side note, I do this with all my ground vehicles as well). I have put thousands of gallons of fuel through the engine. Without question I can say that my GRT fuel totalizer is 100% reliable and valid down to the .1 gallon level. There has never been a moment in time when I did not know exactly how much fuel I have in the tanks, how much I had burned, how much was left to burn, and how much time was left before I needed to be on the ground. Thus, I have great confidence in relying on my fuel instruments to tell me what my fuel situation is at any given time.

I'm a proponent of always having an hour's worth of reserve fuel!! Just simpler, with less that could potentially go wrong that way. My typical longer stints are about 3 hours, which leaves closer to 1.5 hours reserve.

Question...let say you were flying somewhere in a commercial airliner and all the engines went silent for a short perior of time. Then the Captain announces, "don't worry folks, we just ran our fuel dry in one tank. This is our normal operational procedure". Would you ever fly that airline again. Lots of things G.A. pilots can do that working professional pilots would never consider doing. Even though the risk appears minimal, aren't you creating the potential of a real emergency where one did not exist?

I only have 250hrs as a PP, but I fail to see the logic in A. having an engine stop mid flight and B.unbalancing the airplane. It makes no sense to me.

In these United States of America, there is never a reason to run out of gas. Bad planning or bad decision making will lead to it. If you get into your last hour of flight and actually worry about making it home, that?s bad planning or decisions.
I?m not saying don?t run a tank dry but if you feel you have to to make it home safely, land and get gas.
My thoughts are reflected above. With full tanks I plan for an average fuel burn of 8 gph. with 36 gallons that equates to 4 hours. This is a conservative expectation but one that I believe will always allow me to land with fuel in the tanks. In the real world I average more like 7 - 7.5 gph. So even using the conservative choice of 7.5 gph, real world, that gives 4.8 hours of flight time. So planning for 8 gph should always provide for any deviation in climb or descent or other unforeseen issues.

The other issue that has been brought up by Flienlow is the balance of the airplane. With my 9A, if I allow one tank to burn down while the other remains full I have to deal with a noticeable imbalance of the airplane. By switching tanks every 30 minutes I keep the plane in trim at all times.

One last issue, I must always be cognizant of my passenger's needs and desires. She rarely will tolerate a flight leg longer than 3 hours. The longest she has endured has been 3.5 hours. At the speeds of our RVs, 3 hours flight time puts us about 500 statute miles away from our starting point. I don't know about where you live but for us, that places us in an entirely different world from our home world.

I do believe it of value to run a tank dry to examine the performance of the airplane. I do not believe it a prudent thing to do after testing as it only increases the risk factors of that flight whenever it is done. Once one knows the performance of the plane at its extreme limit, is it really necessary to always fly to that extreme?

Oh yes, one last thing, LIVE LONG AND PROSPER!
 
I have been on several commercial flights where the pilot came on the radio and announced that we were diverting to a different airport because we do not have enough fuel - the passenger response is the same as what you are questioning. There were people on those flights who will tell that story for the rest of their life - about how they almost ran out of fuel and that the airline should have put more fuel onboard before the flight.
How the general public reacts to aviation is really irrelevant. There is nothing unsafe with running a tank dry as long as you do not let the engine quit or the fuel system become air-bound. Given the reliability of fuel gauges in the GA fleet I think it is adding safety to keep your last fuel quantity in one tank rather than split between two tanks. Here is why:
A 45 minute reserve is 6 gallons. That means 3 gallons per tank, which is in the red on my fuel gauge. That makes my passenger and me more nervous than anything to see both tanks in the red. I would much rather land with 6 gallons in one tank than assuming I have 3 in each but not really knowing for sure. It is less likely to un-port, and if I have to go-around and get distracted there is a good chance of running the one tank out while low & slow and not focused on the fuel gauges. When I go to fuel power on a go-around and fuel consumption goes up to 16gph, that 3 gallons turns into a 10 minute fuel supply (assuming it is exactly 3 gallons to start with). What if I really have 2 gallons in the tank I am using and 4 in the tank I am not?

Many will argue that a 45 min reserve is not adequate, and I do agree; however there are times when you are racing weather and darkness and other factors where it is much safer to land with a 45 minute reserve than to land short for fuel and add an hour to your trip. In those cases I choose to have all of the remaining fuel in one tank.
I understand what you are saying. However, I would contend that rather than using this philosophy of fuel consumption protocol in order to prevent such a precarious situation at the end of a long flight with little fuel left, I believe one should never plan a flight, or continue a flight, even unplanned, into that environment. In my world 6 gallons of fuel is way below my personal minimums. As stated in my comments in my previous post, anything below an hour reserve is going beyond the minimums allowed for a flight in my plane. There are more reasons to avoid the risks of running a tank dry than there are in running balanced fuel tanks within a planned fuel burn protocol.
 
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Fuel Management

I regularly fly my -8A from California to Pennsylvania and back normally with two fuel stops going east and three flying west.. Have spent a lot of time considering optimum fuel management based on my knowledge/experience with fuel burn and accuracy of fuel level readings (running on left tank, engine quits almost immediately at zero; right tank gives a few more minutes).

I'll burn the left tank dry (at altitude) and finish the flight on the right tank. I do not want to have to worry about fuel tank management in case of a problem/divert.

Not for everyone - but works for me.
 
If you've been switching tanks during the flight, why would you suspect that one tank suddenly would not feed? If that were a legitimate concern, then the only safe course would be to fly the entire flight on just one tank.

The reason it might not feed is the same reason the pitot got clogged with a bug wing while descending through a hole in the clouds.

Yeah, I know, it is a very small risk, but I can't figure out why I should ever run a tank dry. We do so much hand-wringing over how double and triple redundant our panels and electrical systems should be and then some want to remove all fuel redundancy by only having fuel in one tank. I don't get it.

Two hours is pretty much my personal endurance/comfort zone so fuel range just isn't an issue and the fuel computer and gauge on my plane have proven to be very accurate. But I realize there are some iron-butts out there that like to see how many hours they can sit in a small airplane.... ;)
 
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I regularly fly my -8A from California to Pennsylvania and back normally with two fuel stops going east and three flying west.. Have spent a lot of time considering optimum fuel management based on my knowledge/experience with fuel burn and accuracy of fuel level readings (running on left tank, engine quits almost immediately at zero; right tank gives a few more minutes).

I'll burn the left tank dry (at altitude) and finish the flight on the right tank. I do not want to have to worry about fuel tank management in case of a problem/divert.

Not for everyone - but works for me.

What is different between left and right? Could you explain more about your procedure and your fuel system : carbureted/injected? How do you know when the tank is empty, ect.
 
I never run one dry

I never run a tank lower than about 5 gallons...on a long flight i climb out on one then switch to the other. I run it until about 30 mins of fuel remain then switch. I dont have a fuel flow meter and my gages are not very accurate so fuel management is done with my watch.

When you run a tank dry you have reduced redundancy.
The old timers that taught me to fly would freak out at the idea of letting the engine quit on purpose..

To each his own..

Cm
 
But I realize there are some iron-butts out there that like to see how many hours they can sit in a small airplane.... ;)
:D

This is one of the reasons I decided to install the long-range tanks in my airplane, I can tanker fuel for further destinations and do so frequently. I've got a hard minimum of 1 hour reserve for any destination and my "Red Cube" flow meter and Dynon calculations of fuel remaining have proven to be within 0.1 gallon every time once I got them dialed in.

Having said that - I ran dry tanks during testing, and have not done so since, and don't plan to.
 
The old timers that taught me to fly would freak out at the idea of letting the engine quit on purpose..

To each his own..

Cm

This really struck me as well, I can’t seriously believe people do this. If you’re running yourself so low you need to run a tank dry to ensure you have enough for airport ops on the second you should look at your fuel management practices...
 
The other issue that has been brought up by Flienlow is the balance of the airplane. With my 9A, if I allow one tank to burn down while the other remains full I have to deal with a noticeable imbalance of the airplane. By switching tanks every 30 minutes I keep the plane in trim at all times.

I don't think anyone is suggesting to run one tank empty and have the other full. The discussion, as I understand it, is how to manage your fuel when you are getting close to your reserve. Do you switch tanks at 30 minutes leaving 3,4 or 5 gallons in that tank, or do you delay switching tanks until you have consumed all of the fuel in that tank. This way you know for sure that you have all fuel on board available to you for the remainder of the flight.

I have read many accident reports where sufficient fuel was found on board to complete the flight, but in the unselected tank. I do not recall ever reading one where the pilot intentionally ran a tank dry as part of their fuel management protocol and then crashed.

I would not do this in a fuel injected plane; however, in a carbureted plane, I do not see any safety risk with running the tank down until the fuel pressure drops and then switching to the fullest tank before the carburetor bowl runs dry. Sam brought up one possible down side, but if I have been switching tanks up to that point I know they both work. In my opinion the chance of the vent plugging in the last 30 minutes of flight are lower than the chances of the fuel selector jamming when I try to make that one last tank switch.

Something to consider for those saying it is better to land every two hours and top-off (yes, I know I am stretching your position). - TO/Landing are the most dangerous phases of flight, followed by climbs/descents. Why add an additional one of each to your flight and opportunity for something to go wrong? There could be debris on the runway, a wild animal strike, NORAD traffic at that airport, etc, etc, etc.
There is no right answer other than to stay on the ground. The good thing is that people are thinking through their rational for operating the way they do.
 
I don't think anyone is suggesting to run one tank empty and have the other full. The discussion, as I understand it, is how to manage your fuel when you are getting close to your reserve. Do you switch tanks at 30 minutes leaving 3,4 or 5 gallons in that tank, or do you delay switching tanks until you have consumed all of the fuel in that tank. This way you know for sure that you have all fuel on board available to you for the remainder of the flight.

I have read many accident reports where sufficient fuel was found on board to complete the flight, but in the unselected tank. I do not recall ever reading one where the pilot intentionally ran a tank dry as part of their fuel management protocol and then crashed.

I would not do this in a fuel injected plane; however, in a carbureted plane, I do not see any safety risk with running the tank down until the fuel pressure drops and then switching to the fullest tank before the carburetor bowl runs dry. Sam brought up one possible down side, but if I have been switching tanks up to that point I know they both work. In my opinion the chance of the vent plugging in the last 30 minutes of flight are lower than the chances of the fuel selector jamming when I try to make that one last tank switch.

Something to consider for those saying it is better to land every two hours and top-off (yes, I know I am stretching your position). - TO/Landing are the most dangerous phases of flight, followed by climbs/descents. Why add an additional one of each to your flight and opportunity for something to go wrong? There could be debris on the runway, a wild animal strike, NORAD traffic at that airport, etc, etc, etc.
There is no right answer other than to stay on the ground. The good thing is that people are thinking through their rational for operating the way they do.

Exactly!

This discussion subject comes up every once and a while with the same results....
1 - Some that would never empty a tank....
2 - Some that do it all the time......
3 - and some that would only in specific circumstances.

(BTW, I fall into the third category)

Regarding safety in the context of trusting fuel guages, fuel flow meters and management computers, think about it this way -

The only way you can actually know for sure how much fuel you have used from a specific tank (unless you have a visual sight system like on the early RV-12 fuel tanks) is to run a tank (nearly) dry. BTW, if you pay attention and monitor fuel pressure, you can run it nearly dry and never cause the engine to quit.

If you do good in flight record keeping and run one tank nearly dry, you gain the following (very accurate) information, assuming you know precisely how much fuel was in the tank at the start of the flight)..........

At that moment you know fairly accurately (without any reliance on fuel gauges or computers) how much fuel you still have on board (as long as you know your airplane well and can make a decent estimate of what you used for taxi and climb to cruise altitude), regardless of what your fuel gauges and fuel computer says.

You also know very precisely what your actual fuel flow has been during the time you have operated from that tank (once again regardless of what the fuel computer says). This will be very accurate if your start-up, taxi and climb was done on the tank you don't run dry......

Is this for everyone? No. But don't fool yourself into thinking that you are automatically more safe than the guy who does.

Yes, doing so does remove one level of redundancy in the fuel system but as already mentioned, the books are full of accidents where pilot had fuel but apparently didn't have a clue where it was. A standard RV fuel system having only two tanks does reduce the risk of that but it still happens all the time. If a flight is being completed with the understanding that there is an hour of fuel on board and the pilot knows for a fact that it is all in one tank, the risk of this type of accident is extremely low regardless of what equipment failures occurred during the flight.

Standard disclaimer ---- Do not do this without flight testing to learn what signs to watch for (fuel pressure reduction, etc.) and determining how your airplane reacts in case you do accidentally fully drain a tank.


BTW.... in my opinion the riskiest fuel management decision is when to switch tanks (as in where you are at the moment).
If anything bad related to fuel management is likely to happen, this is when it likely will. When possible, I make all of my fuel tank switches when within gliding distance of a decent forced landing site (preferably an airport whenever possible).
 
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I don't think anyone is suggesting to run one tank empty and have the other full. The discussion, as I understand it, is how to manage your fuel when you are getting close to your reserve. Do you switch tanks at 30 minutes leaving 3,4 or 5 gallons in that tank, or do you delay switching tanks until you have consumed all of the fuel in that tank. This way you know for sure that you have all fuel on board available to you for the remainder of the flight.

I have read many accident reports where sufficient fuel was found on board to complete the flight, but in the unselected tank. I do not recall ever reading one where the pilot intentionally ran a tank dry as part of their fuel management protocol and then crashed.

I would not do this in a fuel injected plane; however, in a carbureted plane, I do not see any safety risk with running the tank down until the fuel pressure drops and then switching to the fullest tank before the carburetor bowl runs dry. Sam brought up one possible down side, but if I have been switching tanks up to that point I know they both work. In my opinion the chance of the vent plugging in the last 30 minutes of flight are lower than the chances of the fuel selector jamming when I try to make that one last tank switch.

Something to consider for those saying it is better to land every two hours and top-off (yes, I know I am stretching your position). - TO/Landing are the most dangerous phases of flight, followed by climbs/descents. Why add an additional one of each to your flight and opportunity for something to go wrong? There could be debris on the runway, a wild animal strike, NORAD traffic at that airport, etc, etc, etc.
There is no right answer other than to stay on the ground. The good thing is that people are thinking through their rational for operating the way they do.
Yep, I have had the same conversation with friends a few years ago about landing early or often to fuel the plane. However, what I am saying about my fuel decisions are based mainly on having a long enough reserve to avoid any of the risks that could arise with low fuel quantities at flight end or on landings. You are right about one thing. You are stretching my position about "landing every two hours". That is an exaggerated position to make your point. I have not supported that idea in any of my posts and I would not argue for it here either. What I did say is, with my wife on board, 3 hour legs is about the limit. That leg gets us 500 miles down the road and is a long enough time that she wants to stretch her legs and see what facilities are available. Those 3 hour legs will give us plenty of reserve so that we do not have to worry about unporting tanks and such.

Now, if I were a single guy flying on my own, I might be inclined to stretch the range just a tad bit more, and I have done so as a sole occupant of my plane on occasion. However, even then I have not stretched it past having that one hour reserve. I just do not see the need to do that with an RV. Given our range, I am content to fly a 3-4 hour leg with plenty of reserve on each leg. Flying with such a self imposed fuel range allows me to maintain a level of risk in which I can live. And as I am inclined to emphasize by the link in my signature, living is indeed a goal I strive to achieve. I work hard at doing the things that allow me to:
LIVE LONG AND PROSPER!

I wish the same for everyone else also!
 
As many here have mentioned, there is a huge difference between a turbine and piston in the above discussion. I also think there is some confusion between fuel starvation in a controlled sequence of events and fuel exhaustion which would reek of improper preflight planning. I would personally only intentionally run a tank dry then switch, in level flight with plenty of altitude and with a boost pump on. However, modern fuel totalizers have made the procedure of running a tank dry mostly obsolete.
 
In these United States of America, there is never a reason to run out of gas. Bad planning or bad decision making will lead to it. If you get into your last hour of flight and actually worry about making it home, that?s bad planning or decisions.

I?m not saying don?t run a tank dry but if you feel you have to to make it home safely, land and get gas.
But we are not all in the United States...Many of us live where fuel stops are few and far between, or you need to fly a looong time to get anywhere.

I do not run a tank dry just to make sure I have that bit of extra range, I do it so all my remaining fuel is in one tank, and in doing so, reduces the chances of that fuel becoming unported during maneuvering to landing. 45mins reserve for me is 4.8USG, though I usually plan on a full hour. Would anyone here really be comfortable with only 2.4USG in each tank?

That would be exactly my concern - or a bit of proseal clogs something, or whatever. While the risk of running one tank dry seems low, the reward seems lower.
If you are relying on that as justification for not doing so, the argument doesn't become one of running a tank dry, but of switching tanks at all... That bit of proseal could just as easily render the entire 18 gallons in the tank unusable, then where would you be?

Now, SDSEFI have come out and said they do not recommend the process of running a tank dry with their injection setup, nor is it viable for turbine powerplants. But, properly risk-managed, I believe it is a sensible, safe and practical way to maximise your 'safe' fuel available for descent and landing.
 
there will come a time when you need to stretch your fuel reserve comfort...

Regardless of intention, there will come a time when you need to stretch your fuel reserve comfort... perhaps significantly.

During initial flight testing I wanted to know a few things to better understand how to manage the end of a tank:

  • how much useable fuel my tanks actually hold - run it dry and fill it to the caps... mine will hold and use just over 21 gallons.
  • what the fuel quantity and pressure indications are as the tank empties - float reads solid zero for about two minutes and the pressure drops off fast.
  • how the engine performs when a tank runs dry and you switch tanks - pressure drops quickly, engine sputters but keeps running, switch tanks, pump on, engine sputters a bit then runs normally... start to finish in about 10 seconds.

If fuel threatens to become a critical issue I make a specific decision that when I leave a tank for the last time, it is the last time. I want to ensure that there is a maximum reserve available on a single tank to complete the flight.

One of my tanks has a trap door and flop tube in it and is better able to contain the fuel near the pickup in turbulent or uncoordinated flight. This is my designated landing tank.
 
I read this thread pretty close and I don't think anyone has mentioned what kind of stresses go on inside the engine and related components. When a tank is run dry it can jerk things around quite a bit. If you want to do this to your engine on purpose it is your decision.
 
You might have missed a detail or two. Running a tank dry doesn't mean the engine has to stop, or even get rough.. True for carbs, and apparently contrary to popular belief, also true for Bendix style injection.
 
Is this thread still going? Really?

Lets discuss the "best" color. It's red, BTW, and anyone who disagrees is wrong.
 
From AFP:

"WARNING

Airflow Performance and Bendix/Precision fuel injection systems are non-returning systems. In the event that a tank is run dry in flight, an air lock will be formed on the out let of the pumps. It is possible that the auxiliary pump will not pick up fuel, as the auxiliary pump cannot create enough air pressure to over come the flow divider opening pressure, thus displacing the air and resume pumping fuel. It is not recommended to run a fuel tank dry in flight without adequate testing and proper documentation of the procedure for this operation."

So try it safely before you need it.

Ive been wondering about this AFP note. I get that with EFI youre really running a risk of not being about to over come the bubble because youre relying on the electric pump to loop the fuel, but why would it be an issue with the RSA style? The engine pump is designed to overcome dry injector lines, and pull fuel thru some head height (or how else do we dry start a new motor?), so the AFP pump is immaterial - the engine pump will pull fuel thru it and "prime it". No?
 
I only have 250hrs as a PP, but I fail to see the logic in A. having an engine stop mid flight and B.unbalancing the airplane. It makes no sense to me.

It does make sense if you're trying to maximize range.. I'd rather have 4 gallons in one tank than to have 2 gallons in each tank, more chance of sucking air when the level gets low..
 
My take on this thread

1. Different proceedures necessary for different missions.

2. Just because someone else has a different way of carving the ham does not invalidate the way someone else does it.
 
I have read many accident reports where sufficient fuel was found on board to complete the flight, but in the unselected tank. I do not recall ever reading one where the pilot intentionally ran a tank dry as part of their fuel management protocol and then crashed.
Assuming these were crashes where there were no survivors, how would you know whether it was intentionally run dry and control was merely lost while startled/confused/fumbling to switch tanks?
 
Ive been wondering about this AFP note. I get that with EFI youre really running a risk of not being about to over come the bubble because youre relying on the electric pump to loop the fuel, but why would it be an issue with the RSA style? The engine pump is designed to overcome dry injector lines, and pull fuel thru some head height (or how else do we dry start a new motor?), so the AFP pump is immaterial - the engine pump will pull fuel thru it and "prime it". No?

I put ~190 hrs on a Swift that had Bendix injection (Lyc IO-320, then IO-360 engines) that had an STC'd aux tank. Standard practice on cross countries was to TO-main, switch to aux, run the aux dry, and switch back to main. You always knew within a few minutes when the aux would run dry, so you just monitored the fuel flow/pressure gauge & switched at the 1st drop in pressure & hit the boost pump. Yes, occasionally you could get distracted and the engine would cough/sputter before switching. The engine driven pump has no problem recovering; it'll just recover faster if the boost pump pushes fuel up there.

If the AFP pump is a gerotor or roller vane style pump (and it's almost certainly one or the other), the [AFP] statement makes no sense as written. Gerotor and roller-vane pumps are positive displacement pumps; they will self-prime at any level of lift you're likely to see in the planes we fly. Self-priming by definition means that there will be a bubble of air on the output side of the pump after the pump self primes; it means that the pump is pulling air through itself to get the gas up there. That air has to go somewhere; it doesn't just disappear. So....when the boost pump self-primes, there will always be a (temporary) bubble of air on the output side of the boost pump.

If AFP used a turbine style pump in that assembly, they made a grievous error in pump selection.

EDIT: Just realized what they might be talking about. Positive displacement pumps must have a regulator, to avoid damaging downstream stuff or stalling the pump. The regulator on that pump (and the other brands that are configured similarly) bypasses excess fuel *back to the intake of the pump*. I can see how the pump could fail to pump (gas), once there's air in the system around the pump. It's a lot easier to move air than fuel, so the pump *system* can vapor lock *itself*, if air ever gets in the line.

Something to think about, while flying over that forest, if you think there's ever any risk of unporting your fuel pickup while operating on the boost pump....

Would not be an issue, if the regulator bypass went back to the tank, as is done with the auto style injection systems that are gaining popularity on this forum.
 
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Would not be an issue, if the regulator bypass went back to the tank, as is done with the auto style injection systems that are gaining popularity on this forum.

Also applies to heat buildup while operating at low fuel flows, since the pumps use the fuel flow itself to cool the pump motors. This was the driving factor for me to route the return lines all the way back to the tank.
 
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