Running tanks dry in cruise

[weilke]

All of them have weight limits. Although that seems to be either unknown or ignored. When getting into the bigger trucks and recreational vehicles some have weight limits in different cargo areas, and the big trucks will have axle weight limits.

Old picture. The building in the background houses a ballet school my daughter used to attend.

Note the white panel van in the background that was similarly overloaded.

 

[ja_user]

Well if you burned the first tank for 15 minutes then went half hour half hour half hour half hour half hour in a Cherokee you would be what I call OCD. When I had my Cherokee I would fly half hour, then an hour, then an hour then dry tank (90 mins) and I should have an hour left. If that tank goes empty before 90 minutes I land early.

Which is why I asked. I'm in your category. half hour then 1 hour on the other tank, then back an hour, etc. If balance is going to be an issue.

I've flown with guys that want to switch every 15 minutes, or every 30 minutes but it has never occured to them that the plane is just getting balanced when they switch it back. 1Hour reminder on the G430 will keep you awake.

 

[Clip4]

Which shows you don’t know what it’s about. It’s about determining the exact amount of fuel/fuel burn you have in a tank, and using that info to your advantage. And many pilots more knowledgeable than you or me have been using it as SOP for decades.

If you are unable to determine the exact amount of fuel in the tank without running it dry, what makes you think you can determine the exact amount in the reserve. Also, why are you planning your fuel so close that you need every drop out of a tank?

 

[Tflhndn]

If you are unable to determine the exact amount of fuel in the tank without running it dry, what makes you think you can determine the exact amount in the reserve. Also, why are you planning your fuel so close that you need every drop out of a tank?

It is not for the flight you planned that you need every drop. It is for the flight that didn’t go as planned...

And when everything goes south, wx drops below mins, the wx guessers were wrong and some fool gears up on the only useable runway at your alternate that knowing “exactly”* how many minutes of fuel you have left, and in which tank, is critical.

* yes, yes, no one ever know “exactly” how much fuel is left, but by running one tank dry, you at least know all of your remaining fuel is in one tank - especially useful when down low shooting approaches to mins, going missed, etc.

I have had the flight where it went from a planned 3h45m flight to 5h15m before I could get on the ground when the wx didn’t obey the forecast. It was nice to know where my fuel was (and that I had at least an hour remaining) when I switched to that last tank. (PA24 w/ tip tanks)


Sent from my iPhone using Tapatalk

 

[timwinters]

Why a half hour and not an hour? If you want to keep the tanks that balanced why not every 15 minutes?

I'm not sure if this is where Tim's coming from, but there's one fuel balance/management philosophy that advocates running on the tank that the clock's minute hand is pointing at...switching at the top and bottom of the hour.

Never worked for me and my digital clock.

 

[Salty]

If you are unable to determine the exact amount of fuel in the tank without running it dry, what makes you think you can determine the exact amount in the reserve. Also, why are you planning your fuel so close that you need every drop out of a tank?

It’s not about getting every drop out of the tank. If you leave what you think is 10 minutes of fuel in a tank, it’s 10 minutes of fuel you can’t plan on. If you burn that fuel you have 10 more minutes to fly on the other tank that you wouldn’t have had otherwise.

Let’s say I planned for 60 minutes spare. If I’m delayed by 30 minutes I still have 30 minutes left on the tank I’m on. If I switched with 10 minutes left in the other tank, I’m down to 20 minutes. If something else goes wrong, now I’m facing the possibility of needing to switch tanks after a couple links in the chain of failures has already occurred. You’re removing 10 minutes of your safety net at the time you’re going to want it the most.

 

[timwinters]

The three most worthless things in aviation:

• Runway behind you
• Altitude above you
• Fuel left in the TANK

!!!

 

[Clip4]

It’s not about getting every drop out of the tank. If you leave what you think is 10 minutes of fuel in a tank, it’s 10 minutes of fuel you can’t plan on. If you burn that fuel you have 10 more minutes to fly on the other tank that you wouldn’t have had otherwise.

Let’s say I planned for 60 minutes spare. If I’m delayed by 30 minutes I still have 30 minutes left on the tank I’m on. If I switched with 10 minutes left in the other tank, I’m down to 20 minutes. If something else goes wrong, now I’m facing the possibility of needing to switch tanks after a couple links in the chain of failures has already occurred. You’re removing 10 minutes of your safety net at the time you’re going to want it the most.

Ever hear about diverting before using your reserve?

 

[timwinters]

If you are unable to determine the exact amount of fuel in the tank without running it dry, what makes you think you can determine the exact amount in the reserve.

Ummm...maybe because the engine stops when the tank is empty and then when you refill it...ummm...you read on the pump how many gallons went in. You do understand that the pump tells you that, right?

Also, why are you planning your fuel so close that you need every drop out of a tank?

I can't speak for anyone else except me but, in my case, it adds 30 minutes to my reserve. I won't land with less than 45 minutes in the tank, even VFR, that's my personal minimum. So, if dry tanking allows me to fly non-stop and still land with 45 in the right tank, then you damned right I'll do it! I'd be stupid not to.

There is no downside if you have confidence that your aircraft is properly maintained. Now, if I was flying a clapped out old junker or an aircraft that is annualled by a pencil whipper, then, no, I wouldn't do it. OTOH...I try not to even get into planes like that.

 

[Salty]

Ever hear about diverting before using your reserve?

You still can’t avoid that you are shorting yourself by 10 minutes. You have to divert 10 minutes earlier or you have 10 min less if you have to divert.

 

[FlySince9]

NOT running a tank dry on a long cross country is the unsafe thing to do.

Don't agree...

 

[geneseib]

looking for thoughts and words of wisdom on running a tank dry on a long cross country. I’ve never done this before. But, how else to maximize fuel range and leave the max amount in the last tank for approach, landing, missed approach, etc? Is the method to run her til the engine quits and immediately switch tanks? Any thing to be worried about from a sediment/ contamination standpoint or getting air in the line such that the engine won’t re-light? How much uncomfortable silence is expected before she fires again? Plane is a 63 debonair.

Just don't run them all dry.

 

[weilke]

Don't agree...

Sure, decreasing the amount of fuel available for your flight is always a good thing.

 

[EdFred]

Don't agree...

The only way to know an accurate fuel burn is to run a tank dry.

Scenario: You always leave a half an hour of fuel in your fuel tank and don't dry tank. But how do you know there's a half hour of fuel in your tank? Maybe the primer line stuck open, maybe the fuel flow sender isn't accurate. So, you launch on your cross country flight in my plane. You have 4 tanks. Two wing tanks, and two tip tanks. So your plan is to land with 2 hours of fuel (out of possible 7 hours of fuel). You burn off the tip tanks, and leave what you believe to be a half hour of fuel left in each one. You burn off the left main, and leave what you believe to be a half hour of fuel left in the tank. But what you didn't know is that your draining more fuel from the tanks than you expected, and you made the switch, not with 30 minutes of fuel left in the tank, but 30 seconds of fuel left in the tank, and you happened to switch over just before it was going to run out. But you "know" there's 30 minutes left in each of the three tanks.

So you're flying along on the right main, and you have planned that you will be landing with just short of 30 minutes of fuel in the right main tank. Perfect, you still have 90 minutes of fuel in the other tanks. So you're on a long straight in and about 10 miles out. No problem, you planned have at least 25 minutes in the last tank, and another 90 in the other three. Suddenly, the engine quits 6 minutes short of the field. You freak out because you have never dry tanked. You start to lose altitude, and finally switch to the left tank. Engine comes back to life, and then quits only a few seconds later. You switch to the left tip tank. Again the engine comes back to life, and then quits shortly thereafter. Last tank, same thing. You can see the runway, but it's slowly disappearing behind the trees.

NTSB report: No post impact fire. No fuel found in any of the tanks.

Now, had you run any one of those tanks dry, you would have known that the fuel burn was higher than what you had planned for, and your almost 2 hours of fuel reserve was in fact 2 minutes. You could have stopped 16 airports back, and you would have been able to see your family waiting for you at your destination rather than them seeing you disappear into the trees 3 miles short of the runway.

So how exactly is your way safer?

 

[Clip4]

You still can’t avoid that you are shorting yourself by 10 minutes. You have to divert 10 minutes earlier.

You still can’t avoid that you are shorting yourself by 10 minutes. You have to divert 10 minutes earlier or you have 10 min less if you have to divert.

Your operational mindset puts you at risk of running out of fuel. Running a tank dry to get you 10 minutes will not change that.

At least get a JPI or similar. They are accurate to .2 of a gallon.

 

[Salty]

Your operational mindset puts you at risk of running out of fuel. Running a tank dry to get you 10 minutes will not change that.

Intentionally putting 10 minutes of fuel in a different tank at the end of a flight is putting you at risk.

 

[Juliet Hotel]

The only way to know an accurate fuel burn is to run a tank dry.

Scenario: You always leave a half an hour of fuel in your fuel tank and don't dry tank. But how do you know there's a half hour of fuel in your tank? Maybe the primer line stuck open, maybe the fuel flow sender isn't accurate. So, you launch on your cross country flight in my plane. You have 4 tanks. Two wing tanks, and two tip tanks. So your plan is to land with 2 hours of fuel (out of possible 7 hours of fuel). You burn off the tip tanks, and leave what you believe to be a half hour of fuel left in each one. You burn off the left main, and leave what you believe to be a half hour of fuel left in the tank. But what you didn't know is that your draining more fuel from the tanks than you expected, and you made the switch, not with 30 minutes of fuel left in the tank, but 30 seconds of fuel left in the tank, and you happened to switch over just before it was going to run out. But you "know" there's 30 minutes left in each of the three tanks.

So you're flying along on the right main, and you have planned that you will be landing with just short of 30 minutes of fuel in the right main tank. Perfect, you still have 90 minutes of fuel in the other tanks. So you're on a long straight in and about 10 miles out. No problem, you planned have at least 25 minutes in the last tank, and another 90 in the other three. Suddenly, the engine quits 6 minutes short of the field. You freak out because you have never dry tanked. You start to lose altitude, and finally switch to the left tank. Engine comes back to life, and then quits only a few seconds later. You switch to the left tip tank. Again the engine comes back to life, and then quits shortly thereafter. Last tank, same thing. You can see the runway, but it's slowly disappearing behind the trees.

NTSB report: No post impact fire. No fuel found in any of the tanks.

Now, had you run any one of those tanks dry, you would have known that the fuel burn was higher than what you had planned for, and your almost 2 hours of fuel reserve was in fact 2 minutes. You could have stopped 16 airports back, and you would have been able to see your family waiting for you at your destination rather than them seeing you disappear into the trees 3 miles short of the runway.

So how exactly is your way safer?

All perfectly true. All perfectly logical and I agree with all of it completely. Unfortunately just politics, religion and conspiracy theory, it will do absolutely nothing to convince anyone who isn't already convinced.

 

[Hunt-man]

https://www.avweb.com/news/pelican/182044-1.html

Great article. Good read. This guy is right.

 

[FlySince9]

So how exactly is your way safer?

didn't say mine was safer, just disagreed with the all inclusive statement that not running the tank dry is not safe...

 

[FlySince9]

Sure, decreasing the amount of fuel available for your flight is always a good thing.

didn't say that, did I? You can plan your flight in a way that doesn't require you to use every drop of fuel in your tanks requiring you to run one or more dry in the process...

At my age, my bladder is only good for 90 minutes at at time anywayz... LOL

 

[RudyP]

Your operational mindset puts you at risk of running out of fuel. Running a tank dry to get you 10 minutes will not change that.

At least get a JPI or similar. They are accurate to .2 of a gallon.

Haha. You have it totally backwards. By limiting how much of your fuel is actually useable, you are exposing yourself to a higher risk of running out than he is.

Your 45 minutes of reserve is actually 35 because you have 10 minutes of mystery fuel that you can’t exactly place and if you and he end up cutting it close at some point (the airport has a disabled aircraft on the runway, your alternate is 25 min away), you are the one who might have the engine die on you on short final.

No matter how you rationalize it, for any number that you think is acceptable fuel planning, the equivalent number with someone who is willing to run a tank dry will give you more certainty to use the entire reserve. Whether you book that extra certainly as safety margin or extra range is up to you but the silly thing is to not have a safe plan to use as much of the fuel you brought onboard as you possibly can.

 

[Ravioli]

I'm not sure if this is where Tim's coming from, but there's one fuel balance/management philosophy that advocates running on the tank that the clock's minute hand is pointing at...switching at the top and bottom of the hour. Never worked for me and my digital clock.

Yes, that is the theory I was taught, and I described it oh so many posts ago in this thread. With the comment that I may be considered an "over switcher."

 

[ja_user]

It does impact your range, especially when people start leaving 5-10 gallon in 4-6 tanks because they don't like to run dry or close to it. Plenty of people have went down due to fuel starvation, but still had fuel on-board.

Tough to compare fuel management in a C172 with a cabin class twin, etc.. So to each their own.

And to the "over switchers", it doesn't really hurt anything. But please have a better understanding than "This is what my CFI told me to do."

 

[bradg33]

One of my airplanes has 5 tanks (Viking), the other has 4 (TBone). In the Viking, if I don't run the tanks dry I'm leaving quite a bit of unusable fuel scattered among several tanks. So as a matter of practice I run them dry on cross-country trips. My TBone has 4 tanks (aux and main on each side). Takeoff/land on the mains, cruise on the aux tanks. I run the aux tanks dry as a matter of practice on cross country flights, too.

 

[ja_user]

The VIking is a good example of "Know your Fuel system".

 

[weilke]

didn't say that, did I? You can plan your flight in a way that doesn't require you to use every drop of fuel in your tanks requiring you to run one or more dry in the process...

Sometimes flights dont go as planned. I fail to see how I would be better off with 3 tanks containing 3gallons each while I burn down the fourth one.

I do have to say, that if one burns down the tips on a Osborne system without transfer pumps, it is a good idea to tell the next guy who flies that he may have to suck 16ft of air filled line through the pump before the engine comes back. So dont switch to that tank at night over the mountains .

At my age, my bladder is only good for 90 minutes at at time anywayz... LOL

The original post spoke about a 'long cross country'. Your definition of what is long may vary from mine.

 

[EdFred]

Sometimes flights dont go as planned. I fail to see how I would be better off with 3 tanks containing 3gallons each while I burn down the fourth one.

I do have to say, that if one burns down the tips on a Osborne system without transfer pumps, it is a good idea to tell the next guy who flies that he may have to suck 16ft of air filled line through the pump before the engine comes back. So dont switch to that tank at night over the mountains .

On the Comanche, I can have two fuel selectors. OFF-LTIP-LMAIN | RMAIN-RTIP-OFF. So when I go to switch to tips, I usually turn one of the mains to tip for about 30 seconds or so, then the other. Haven't had the engine go unexpectedly quiet yet.

 

[bradg33]

The VIking is a good example of "Know your Fuel system".

That's the truth. The NTSB records are full of Viking accidents that happened because the pilot flubbed up fuel management. 5 tanks, 2 selectors, and gauges that only show the level of the selected tank. Later models went to a 2-tank setup, but lots of early 4-5 tank models still flying.

 

[bflynn]

My memory of the Piper POH says to run one tank for 30 minutes ,switch to the second tank and then run that until you expect to have 30 minutes left on it. Switch back to the first tank. If that one runs dry, you are on reserves, have an emergency situation and must land immediately. Your call if that's an airport or the nearest field.

 

[EdFred]

My memory of the Piper POH says to run one tank for 30 minutes ,switch to the second tank and then run that until you expect to have 30 minutes left on it. Switch back to the first tank. If that one runs dry, you are on reserves, have an emergency situation and must land immediately. Your call if that's an airport or the nearest field.

That results in some serious wing heaviness. Which is why I would do what I did as mentioned previously in the thread in the Cherokee.

 

[flyingcheesehead]

Reminds me of @Eamon and his old injected Musketeer, which had all of its return fuel going to the left tank regardless of which was selected. He said he would start with the left tank, run it dry, switch to the right tank, run it dry, and then he would have 45 minutes remaining in the left tank and needed to land and get fuel.

 

[Zeldman]

I guess no one here has heard of ''pocket gas''....

 

[EdFred]

I guess no one here has heard of ''pocket gas''....

I have but it usually involves bad Mexican food, and bed sheets.

 

[MooneyDriver78]

When installing a certified engine monitor (my case a JPI 900), you have to calibrate the fuel senders. Found out how much my tanks hold, quarter tank increments, without having to run my tanks dry in the air. Both tanks hold extra 1.5 gallons.


Tom

 

[EdFred]

When installing a certified engine monitor (my case a JPI 900), you have to calibrate the fuel senders. Found out how much my tanks hold, quarter tank increments, without having to run my tanks dry in the air. Both tanks hold extra 1.5 gallons.


Tom

And how do you know that at some point you don't develop a fuel leak before the fuel gets to the fuel transducer? Or the transducer goes bad. Had that happen on my JPI. And if those are the resistive float units they still aren't *that* accurate.

 

[flyingron]

Knowing how much more you have by running it dry doesn't tell you how much "usable" fuel you have. Tanks are calibrated from full down to zero usable, not from bone dry up.

 

[EdFred]

Knowing how much more you have by running it dry doesn't tell you how much "usable" fuel you have. Tanks are calibrated from full down to zero usable, not from bone dry up.

It sure does. If I know I've burned 30 gallons in 2.4 hours (my tips are bone dry when dry tanked), I know how many hours of usable I have left in the remaining 56 on board. On a 1000nm XC I was within 5 miles of where I did my last dry tanked actual vs calculated, and I was within half a gallon of what I calculated to have left when I landed. Unless a 1/2% error is not telling me what I have left.

 

[tmyers]

I could be wrong, and often am, but I think most of us are simply comfortable with what we were taught in primary flight school and that is ingrained in our brains. Not gonna change anyone's way of thinking on the subject.

 

[EdFred]

I could be wrong, and often am, but I think most of us are simply comfortable with what we were taught in primary flight school and that is ingrained in our brains. Not gonna change anyone's way of thinking on the subject.

You're just saying that because it's what you were taught.

 

[midwestpa24]

I could be wrong, and often am, but I think most of us are simply comfortable with what we were taught in primary flight school and that is ingrained in our brains. Not gonna change anyone's way of thinking on the subject.

The law of primacy.