Available fuel in a Piper

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Another current thread made me think about an issue I have with flying Pipers. Say I calculate that I have 2.5 hours of fuel in a tank. I've been taught the various methods of managing fuel by CFIs, but you always end with .5 hours of usable fuel in each tank (1 hr reserve). For instance, I've got 5 hours of usable fuel total, but after 4 hours of flying, there's .5'ish remaining in each tank. Do people really burn the gas down that low and count on that last .5 hour (each side) remaining when descending into the terminal environment? Are they not concerned with the tank running dry before they're in a position to land? Is the better method to run a tank dry en route, then rely on the last hour being contained in one tank? Seems this would be the more accurate method for determining true fuel quantity too. I suppose you just wait for the engine to cough, then quickly switch tanks and flip the boost pump on until you're certain it's feeding properly.

Anyone run a tank dry intentionally in a Piper?
 
Why are you posting this anon? Your asking perfectly legit questions and running a tank dry intentionally is not a bust.
 
It just takes practice and knowing your airplane. I don't usually run them dry intentionally but have done so inadvertently. If your paying attention you can often see the fuel pressure start dropping before the engine actually quits.

So how accurately are you running them down to .5hrs remaining, ie how much fuel do you put in afterwards? If you are planned on using 20 gallons and actually used 20 gallons then you can experiment with using 22 or 23 gallons on one side. if you aren't hitting your planned number accurately then you probably need to adjust the planned GPH number. And then can you do it consistently?
I do try to avoid running them this low at lower altitudes or in busy environments, once in the terminal area I run on the fullest tank.

BTW got really good at doing this with Viking with 5 fuel tanks that only between 45 min to 90 min of fuel each.

Brian
 
As someone new to Pipers I have the very same question/concern about how best to manage fuel. Right now what I do is switch tanks every hour of flight but wondered if that's a good way as my concern is if I switch every hour at some point I may be left w/ say a 1 hour reserve but split between the 2 tanks and how would I manage that last hour should I need it (e.g. run on one tank until dry and then "count" on the remaining fuel on the second one?, etc..)
 
I've run a tank dry before... best to be higher up, be aware of approximate time, and be ready to hit the boost pump with the other tank selected. It's good to know how to do it if you hit headwinds 20 KTS worse than forecast.
 
brcase said:
It just takes practice and knowing your airplane. I don't usually run them dry intentionally but have done so inadvertently. If your paying attention you can often see the fuel pressure start dropping before the engine actually quits.
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Correct. I have run one tank until empty just once on an Archer. I was waiting for it and saw the fuel pressure dropping.. switched tanks ... and the pressure was normal before I could switch on the electric fuel pump.

-Skip
 
I take off with full fuel and with a 3 hour bladder I plan to be landing with plenty of reserve. After at most 4 hours I need to get out and move around.
 
Unregistered said:
Another current thread made me think about an issue I have with flying Pipers. Say I calculate that I have 2.5 hours of fuel in a tank. I've been taught the various methods of managing fuel by CFIs, but you always end with .5 hours of usable fuel in each tank (1 hr reserve). For instance, I've got 5 hours of usable fuel total, but after 4 hours of flying, there's .5'ish remaining in each tank. Do people really burn the gas down that low and count on that last .5 hour (each side) remaining when descending into the terminal environment? Are they not concerned with the tank running dry before they're in a position to land? Is the better method to run a tank dry en route, then rely on the last hour being contained in one tank? Seems this would be the more accurate method for determining true fuel quantity too. I suppose you just wait for the engine to cough, then quickly switch tanks and flip the boost pump on until you're certain it's feeding properly.

Anyone run a tank dry intentionally in a Piper?
Click to expand...


It depends, but yes, I will run down to .5 fuel when I'm running around an area when I am never more than .1 or .2 from an airport with fuel along the way. Some parts of the country are more dense with airports than others. I also have no qualms with running tanks dry before switching so I have all my remaining fuel in my last tank or set of tanks on a twin. On my 310 I always ran the auxes dry.
 
If you dig around on Avweb you'll find a pretty compelling argument for running the tanks dry by John Deakin. That being said, on the Navion you can run the AUX's dry if you want, but you're in a bad situation if you run the main dry: first it's the only one placard for use in all flight regimes and second, and this one is what I believe personally was the problem with the crashes held up to be "fuel valve defects" (crammed down the communities throat as an AD by the people who currently own the Navion TC). Some of the aux tank designs can't flow the 24+ GPH that the big engines need when all the knobs are pushed forwards.
 
Cubs are Pipers. Running the right tank dry is common practice in a Cub since landing and takeoff are done on the left tank.

Get familiar with your airframe and the recommended fuel management for that model.
 
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I switch fuel on the half hour in my Cherokee to keep the aircraft balanced. If I runs tank dry it is a very, very big deal, because it means I have about a half hour left in the other. As it is I've never even come close.
 
If I remember correctly, the Aztecs I used to fly had 4 tanks of 36 gallons each, plus the Metco tip tanks of 12 gallons each for a total of 168 gallons.
On the longer legs we used to always run the tips dry and even when you knew they about to run dry in the next few minutes, you always jumped when you heard the engine burp as it sucked it dry. As you reached down to switch tanks, it was sometimes difficult not to bump heads with the other pilot because both of us would be reaching for the selector at the same time.
 
Unregistered said:
Another current thread made me think about an issue I have with flying Pipers. Say I calculate that I have 2.5 hours of fuel in a tank. I've been taught the various methods of managing fuel by CFIs, but you always end with .5 hours of usable fuel in each tank (1 hr reserve). For instance, I've got 5 hours of usable fuel total, but after 4 hours of flying, there's .5'ish remaining in each tank. Do people really burn the gas down that low and count on that last .5 hour (each side) remaining when descending into the terminal environment? Are they not concerned with the tank running dry before they're in a position to land? Is the better method to run a tank dry en route, then rely on the last hour being contained in one tank? Seems this would be the more accurate method for determining true fuel quantity too. I suppose you just wait for the engine to cough, then quickly switch tanks and flip the boost pump on until you're certain it's feeding properly.

Anyone run a tank dry intentionally in a Piper?
Click to expand...

I have dry tanked a Cherokee 180 on purpose once. I also did it unintentionally once.

Neither is much fun, but it is a very useful way to know exactly how much fuel you have.
 
netsurfr said:
As someone new to Pipers I have the very same question/concern about how best to manage fuel. Right now what I do is switch tanks every hour of flight but wondered if that's a good way as my concern is if I switch every hour at some point I may be left w/ say a 1 hour reserve but split between the 2 tanks and how would I manage that last hour should I need it (e.g. run on one tank until dry and then "count" on the remaining fuel on the second one?, etc..)
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When I'm really needing to go the distance in a Piper like that I generally time things to where I run one of them dry at altitude with an airport nearby.
 
I've run the tanks dry several times. Then you know that tank is dry and don't switch back to it. When you get on the ground you can accurately put fuel back in and calibrate the gage and double check the amount the tank will hold. Cold weather and you can get more fuel in the tank. :D
 
Found the article and makes sense. I like the idea of running on one tank till close to empty or empty before switching but I always worried this would be dangerous and I see based on the article its an OWT. My other worry was that the plane would be unbalanced.

flyingron said:
If you dig around on Avweb you'll find a pretty compelling argument for running the tanks dry by John Deakin. That being said, on the Navion you can run the AUX's dry if you want, but you're in a bad situation if you run the main dry: first it's the only one placard for use in all flight regimes and second, and this one is what I believe personally was the problem with the crashes held up to be "fuel valve defects" (crammed down the communities throat as an AD by the people who currently own the Navion TC). Some of the aux tank designs can't flow the 24+ GPH that the big engines need when all the knobs are pushed forwards.
Click to expand...
 
netsurfr said:
Found the article and makes sense. I like the idea of running on one tank till close to empty or empty before switching but I always worried this would be dangerous and I see based on the article its an OWT. My other worry was that the plane would be unbalanced.
Click to expand...

It's not that big of a deal on the engine or the balance. Start by pulling 1/2hr out of one side then go to hourly swaps.
 
I have run a tank dry more than a few times in the low wing Pipers. I'd rather have that last 10 gallons on one side than split between the tanks. I would do it at altitude and it wasn't a surprise, usually the engine only stumbles at most. One can usually see the fuel pressure needle start to waiver.

I would also only do it over a forgiving area for an engine out below, just in case.
 
When I fly low wings I switch tanks every 1/2 hour and use the analog clock as my reminder. If the minute hand is between 01 and 30 minutes past the hour I'm on the right tank and 31-60 I'm on the left tank.

Works well for me in cross-checking the fuel selector if the changeover "time" occurs while I'm attending to other things.
 
I fly an Archer and I just switch tanks every half hour. I also would say 5 gallons per side is ~.5 hours each. I have never run it that low though, I do not trust my fuel gauges and then I'm reliant on my own mental calculations based on time as to how much is really in there.

I've yet to be more than a gallon or two off.... but with only 5 remaining that makes me uncomfortable.

My tanks are 48 gallons or 4.8hours. I try to limit flights to about 3 hours, but I'll go a little over that without a lot of worry.

One practice I've started is on my 30 minute tank switches is if I'm getting close to my destination I'll delay switching a while longer.. maybe 15 minutes or so until I start my descent. The idea being I'm leaving a little more in the tank I'm going to be on when I enter the traffic pattern.
 
The main tanks on most low wings are fairly close into the longitudinal axis. Leaving them unbalanced is purely an annoyance. If you have tip tanks where you've got 120+ of fuel hanging out at the far end of the wing, having one full and the other empty can result in real controllability problems.

There's an odd behavior on my IO-550 which someone explained to me but I've forgotten. At near idle power settings the thing flows some incredible amount of fuel (much more than at cruise settings) from the selected tank. It returns that back to the main (all returns go to the main on my plane). I inadvertently taxied out at Dulles (which was nearly 3 miles that day) with the tip tank selected. By the time I got to the runway the tip tank had drained (though I had not noticed). I took the bad handling on takeoff to be a crosswind. Enroute I found the autopilot making S-turns about the course. I didn't know what this was until I punched the red button and found that the plane wanted to keep rolling to the left.

I checked the tanks and realized my error and landed and retopped the low tip tank. Now I'm always careful to not taxi on the tips (at least not for any extended time).

A similar effect occurred when doing my instrument rating. We did most of our approach work at quite reduced settings (the instructor felt it was more advantagenous to keep the speed down to Vle which is VERY SLOW in the Navion to minimize configuration changes). Again I managed to suck down a tip tank in short order. Nothing more unsettling than running a tank dry in the middle of the procedure turn.
 
Ron,

The swift is set up in a similar manner. The continental engine driven pump is always pumping higher volumes of fuel than your engine can burn at that particurlar RPM. What is not used by the engine is dumped back into the main tank via the return line. Modern cars are set up this way as well. As a side note the Jet-A C182 has a similar set up, the warm return fuel keeps the diesel from gelling at altitude (low temps)

I'm guessing at Taxi RPM's the pump is turning fast enough to pump a ton of fuel, but the engine is not working very hard at that speed and is burning very little. So most of the fuel is getting dumped back in the main tank.

In the swift, the pump flows about 20gph in cruise and the engine burns about 10gph. I have 11 gallon tip tanks and I will run them dry in 30 minutes. However I only burned half of that fuel, the rest ended up in the main tanks.

Takes some careful management. You need to be sure there is enough room in the main tank when running off of the aux tanks. If the main tank is full and you switch to the auxilary tank, you're putting about 10gph out of the main tank vent.

I can also share your concerns about Vle and instrument approaches. The Vle on the swift is a measly 100mph. About 2 minutes before the FAF I need to get the throttle back until the gear horn starts going off just to slow down enough.
 
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The issue is that at cruise, it draws maybe 18 GPH out of the the tank and puts 4 GPH back in the tank. At taxi settings it draws more than twice that. I could understand it if it always drew 26 GPH and put back what it doesn't need, but the outflow from the aux is higher when it needs less.
 
To the original topic: I've had the same concern in my arrow. I've adopted the practice of making sure that nearly all of my 1 hour planned reserve is available in one of the tanks while sagging the level in the other tank while I still have altitude to burn.

I do it for the exact reasons mentioned: don't want sputter at making the base to final. If for some reason i have to divert or headwinds have eaten into the reserve, its one less thing to have to mess with while getting to my destination. And finally it ensures theres a little more forgiveness in the tanks for a poorly coordinated turn.

I certainly don't plan to fly poorly especially near the ground. But know I'm capable of mistakes and will take all the margin I can give myself when in close proximity to terra firma.

I've gotten pretty good at leaving 2 gallons useful in the tank I'm not landing with. I've never run one dry and don't plan to. But if I do by mistake it will be while I have some altitude.... or at least that's the plan
 
Try it on a Piper with 4 tanks.
I only ran a tank dry once - on my first full day as a pilot after my checkride. :redface:

It's really hard to use up all of the fuel when you have 84 gallons.

The lowest I ever got it was when a fill up was 56 gallons, meaning I had over an hour and a half of fuel left but I would have to know where it was.

I time the switching so I have that 1 1/2 hours left when I'm looking for a place to refuel and I never run a tank dry on purpose.
 
I've run a tank pretty darn low, 3 gallons left, when the tank had to be drained to replace the sump valve. I saw no reason to run it dry since a bucket was needed regardless. If there are 4 tanks then I could see running two or three tanks dry but only for an absolute max range effort. It'd help to know the aircraft wasn't one of those with "floaters" in the sample when sumped.
 
Clark1961 said:
I've run a tank pretty darn low, 3 gallons left, when the tank had to be drained to replace the sump valve. I saw no reason to run it dry since a bucket was needed regardless. If there are 4 tanks then I could see running two or three tanks dry but only for an absolute max range effort. It'd help to know the aircraft wasn't one of those with "floaters" in the sample when sumped.
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If you have crap in the tank that comes out when you sump, it doesn't matter how much fuel you have in the tank, that crap will still get sucked into you gascolator.
 
I know I'm a little new here, but I see this all the time at my airport. Take a look at this photo and note the total useable fuel (2 tanks):

photo-1.jpg


I kid you not, I pumped 73.6 gallons of fuel into this aircraft, a Bonanza. Pilot wasn't even phased when I told him how much fuel his aircraft took. This aircraft flew in from at least 350 miles away. I've got an almost identical story about an Arrow III. I see a constant issue of pilots relying more on the published range in distance of their aircraft vs. its endurance in time. I have a 1977 Lance, and I know how many hours I can go with full tanks and still have a comfortable reserve that is usable. I've never told anyone else how to fly their own aircraft and I'm not starting now...but it's extremely important to know your aircraft's capabilities and limitations. Big difference between running one tank dry and running both (all) of them dry. I'm thankful that I only have 2 to manage...I don't know how people with more than that do it! ;)
 
Wow that's running on fumes. I was taught to run one of the tanks dry and it was always a non issue. I would make a game of it to catch it just as it stumbled. I'm the ARROW with 50 gallons at the tabs. I run left tank 30 minutes then right tank one hour then left tank dry. That should leave about 1.5 hours in the right tank. I have the fuel totalizer in my JPI so the only way to know how much fuel you really have left is to run one of the tanks dry.
 
All GA aircraft certified under CAR 3 or later must demonstrate running a tank dry, then switching to the other tank without changing ANY other settings and having the engine restart within X seconds(forgot the X time). I have 3 tanks and I've run each of them dry in flight at one time or another. Then I know exactly how much fuel it takes to refill so I know my capacity and endurance. Aux tanks aren't always covered, which is why many of them are placarded for in-flight use only.

Running a tank dry in cruise should be a non-event. It will also improve the endurance. Just remember, the rule is 'in cruise flight' and not on base leg.
 
Ok here is one that I have been at odds with for a long time. That would be the G in humps. I am very reluctant to change tanks while entering the pattern. Not sure why but unless fuel remaining is a big question I would rather just land on the tank I am running on. Thoughts?
 
Ok not humps. I meant gumps. Dayum I laughed out loud when I saw the spelling correction.
 
g in gumps is just a reminder to make sure the selector is on an acceptable tank, and boost pump is on if necessary.

Some planes can't use certain tanks for takeoff and landing.



Sent from my iPhone using Tapatalk
 
tmyers said:
Ok here is one that I have been at odds with for a long time. That would be the G in humps. I am very reluctant to change tanks while entering the pattern. Not sure why but unless fuel remaining is a big question I would rather just land on the tank I am running on. Thoughts?
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"the G in humps" is pretty good ;).

I was just talking about this issue with my CFI today while finishing a checkout in the Cherokee Six. Some tidbits:

- Definitely we should think carefully about when to replace a known-working source of fuel with a probably-working source. At a comfortable cruise altitude and near an airport? Absolutely. In mountains over rugged terrain? Right before takeoff? Let's talk options.

- CFI said he once set the fuel selector to off and timed how long until the engine quit -- about 3 minutes at 1000 rpm. Pretty scary to think about where that would leave you if you switched to a bad (empty/contaminated/blocked/etc) tank right before applying full power and taking off.

- I agree with you that if I've arrived at my destination with plenty of fuel in the current tank, I leave the selector alone and just land.
 
I really don't have an issue changing tanks to a tank I've drawn from when approaching to land, cuz I got fuel from there before. Of course - this doesn't work well if I drained the tank dry in flight.... DOH
 
tmyers said:
I am very reluctant to change tanks while entering the pattern. Not sure why but unless fuel remaining is a big question I would rather just land on the tank I am running on. Thoughts?
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The AFM for the 'kota says "fullest tank" for landing. I think it's a good habit to be in as long as the tank has been used on that flight (known good).

Sure, we can judge when we have plenty, "hey 20 gallons is two hours, good to go." I like the habit of checking the gauges and verifying them with run time (I do that as a matter of habit during the flight anyway) and selecting the fullest. One thing you can do is plan the fuel tank switching so you arrive in the airport vicinity already on the fullest tank. If it was a short flight and I didn't switch tanks then I won't switch for landing.
 
For fun, I pulled out the POH for the PA-28-161 I used to fly, here's the paragraph on switching tanks:

Always remember that the electric fuel pump should be turned "ON" before switching tanks, and should be left on for a short period thereafter. In order to to keep the airplane in the best lateral trim during cruising flight, the fuel should be used alternately from each tank. It is recommended that one tank be used for one hour after takeoff, then the other tank be used for two hours; then return to the first tank, which will have approximately one and one half hours of fuel remaining if the the tanks were full at takeoff. The second tank will contain approximate one half hour of fuel. Do not run tanks completely dry in flight. The electric fuel pump should be normally "OFF" so that any malfunction of the engine driven fuel pump is immediately apparent. If signs of fuel starvation should occur at anytime during flight, fuel exhaustion should be suspected, at which time the fuel select should be immediately positions to the other tank and the electric fuel pump switched to the "ON" position.

So, the interesting takeaway from this, the Warrior II has 2.5 hours of fuel in each tank when full.
 
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