Inop fuel gauge on rental + long XC

[PilotAlan]

A plane I rent from time to time had a fuel gauge that read a few gallons low. Eventually, it got stuck at zero irrespective of the quantity of fuel in the tank. It was squawked but never placarded. I suspect it was fixed at annual.

And I fully expect that the myth that gauges only have to be correct at zero came from FBOs and flight schools that didn't want to pay the money to make them function properly.

The only fuel that exists to me is fuel that I either measured or put in the tank myself. I go by that and very conservative/padded burn rates.

Agreed, in that endurance is calculated in time with a conservative reserve. But best practice and rules on operating minimum equipment are two different conversations.

But if the fuel is not required to work, why is it required to put in the plane as minimum VFR equipment?
And if a gauge stuck at zero is legal (since the myth is that it only has to be correct at zero), how do you know when the tank is actually at zero?

How do you identify a fuel leak, venting fuel from a overpressured tank, or excessive fuel burn? The clock won't tell you any of those things.

 

[PilotAlan]

How will you know when they're not?

At every fill up I compare the expected amount required to the actual amount required. I dip the tanks on preflight and compare that to the gauge readings.

Endurance is still a function of time, not gauges, but the gauges provide valuable information, no?

 

[wabower]

The answer is also the title to a Simon and Garfunkel song. BTDT.

And I fully expect that the myth that gauges only have to be correct at zero came from FBOs and flight schools that didn't want to pay the money to make them function properly.


Agreed, in that endurance is calculated in time with a conservative reserve. But best practice and rules on operating minimum equipment are two different conversations.

But if the fuel is not required to work, why is it required to put in the plane as minimum VFR equipment?
And if a gauge stuck at zero is legal (since the myth is that it only has to be correct at zero), how do you know when the tank is actually at zero?

How do you identify a fuel leak, venting fuel from a overpressured tank, or excessive fuel burn? The clock won't tell you any of those things.

 

[PilotAlan]

The answer is also the title to a Simon and Garfunkel song. BTDT.

Nice......

Or are you saying you are a peculiar man? Or are we hearing the voices of old people in this thread?
All I know is I took that silver haired daddy of mine flying last year, late in the evening over Bleeker Street in my little town, and he says I'm still crazy after all these years......

 

[ChrisK]

Nice......

Or are you saying you are a peculiar man? Or are we hearing the voices of old people in this thread?
All I know is I took that silver haired daddy of mine flying last year, late in the evening over Bleeker Street in my little town, and he says I'm still crazy after all these years......

Keep the customer satisfied like a 59th street bridge over troubled water.

 

[Dan Thomas]

I actually just had a similar situation yesterday. When I was doing the preflight, I saw that the right tank was on E and the left tank was on about 1/3. When my CFI came out of the FBO I asked him if we were flying light on purpose. He told me that the plane had been flown about 4 hours prior, and that it had been filled up after the last flight, and that the gauges were working properly when they shut down the plane after that flight.

We visually verified that the tanks were both full. We rocked the wings by hand while still on the ground (in case the sensor was stuck), but nothing would budge the gauges.

Knowing full well we had plenty of gas to do touch and goes for an hour, we prepared to launch. As we were taxiing to the run up area, I saw that both tanks were now registering F. We scratched our heads and took off.

Bad electrical supply to the gauges, probably. If it was sticking sender floats, it would likely be only one gauge, and it would rise when the wings were rocked.

Homebuilders can buy capacitance fuel level gauges. No moving parts. The system reads the difference in dielectric constants between air and fuel and displays it on the gauge. Old systems (like the Electras I used to work on, built in 1958-1961) used an analog gauge, while newer gauges are digital.

You can buy an entire uncertified system for less than the cost of a single certified and inaccurate fuel sender. I wish I knew why light aircraft manufacturers aren't using capacitance systems yet. With multiple probes in a single tank you can eliminate the inaccuracy caused by aircraft attitude, too.

See:

http://jameswiebe.blogspot.ca/2010/09/belite-fuel-gauge-installation.html

Dan

 

[wabower]

In my case it was "The Sound of Silence" when the Aerostar fuel line broke over the Rockies.

 

[ChrisK]

In my case it was "The Sound of Silence" when the Aerostar fuel line broke over the Rockies.

You're breakin' my heart.

 

[azure]

Land immediately and check it out.

Could be a fuel leak, cap left off, etc. I would never just assume the gauge went bad in the middle of my flight.

If low wing or individually selectable I would switch to the tank showing good prior to landing.

Once on the ground you can go from there.

Agree 100%. The only thing I would add is: if you're on FF, do not, repeat NOT tell ATC anything about your reason for landing, unless you have reason to suspect it's more than a simple gauge malfunction and you might need assistance. Tell them you need to make a pit stop or something. If you then take off after having assured yourself that nothing serious was wrong*, and ATC knew what was going on, you may have to explain yourself to an inspector from the local FSDO.

(I'm not speculating BTW, this actually happened to me.)

*And actually, unless the gauge is functioning normally again, the airplane is legally unairworthy anyway -- which is why the FSDO might be interested.

edit: caught up on thread now, legalities already covered ad nauseam. Sigh.

 

[Fearless Tower]

In which case wouldn't you expect the quantity on the other gage to decrease by more than the estimated amount of burn?

That has been my experience in the Cardinal. With the fuel selector on BOTH, one tank goes up slightly while the other tank goes down a lot.

 

[Dan Thomas]

That has been my experience in the Cardinal. With the fuel selector on BOTH, one tank goes up slightly while the other tank goes down a lot.

Let me guess. Right tank rises, left goes down. A leaking fuel cap gasket or cap vent check valve on the right tank.

Dan

 

[Fearless Tower]

Let me guess. Right tank rises, left goes down. A leaking fuel cap gasket or cap vent check valve on the right tank.

Dan

No, wasn't the fuel cap. It has been a while since was flying the Cardinal and hanging around CFO, but it apparently was a design flaw that IIRC had something to do with the way the vent system was plumbed.


Sent from my iPad using Tapatalk HD

 

[Silvaire]

..

Thank god I am the only "idiot" that flys it and updates the fuel added..

It only takes one

 

[N801BH]

It only takes one

Yup..... And I will only have myself to blame..

 

[flyingron]

That's contrary to the 172 POH. Land on both even with one tank empty. That "unusable" fuel may help you in a turn, and the gascolator won't suck air unless BOTH ports are dry.

Correct. The only time you should use LEFT/RIGHT in flight is above 5K in cruise. Besides, the fuel selector on the 172 is only a suggestion to the engine as to which tank to draw fuel from.

 

[flyingron]

My understanding of 91.205 is that you have to have a functioning fuel gauge for every tank, but that they only need to be accurate when the tanks are empty. Is your gauge inaccurate and fluctuating, or is in inoperative? If the former, it's legal, if the latter it's not.

Practically, given how inaccurate most fuel gauges are, I use a generous fuel burn figure and keep a log of time on each tank. This has been an accurate metric for me.

Actually, the above statement is a myth. The FARs make no statement about fuel gauge accuracy at all. The reg that people commonly attribute to "only accurate empty" just says that the E mark corresponds to zero usable rather than bone dry.

It's not really the gauge's fault in most planes. The fuel tanks are shallow pans. Any acceleration tends to send the fuel sloshing across the breadth of the pan which given the sender is measuring a very shallow vertical section can make for some wild fluctuations.

Given lots of flights and refueling at various points on the gauges, I kind of know how mine behave (no indication off pegged Full for the first ten gallons and then you kind of average the excursions for the middle range and then when it starts smacking on the left side, I've got an hour reserve.

I've also got a fuel totalizer (Shadin sensor feeding a JPI) which is pretty good. I always use the most pessimistic of the:

1. What the totalizer tells me
2. What the fuel guage is telling me
3. What I've computed as my fuel burn.

I had a loose pump fitting cause me to throw fuel overboard at 45 GPH coming out of annual one year. You can believe I trusted the fuel gauge when it was heading towards half tanks with reckless abandon.

Another friend ran out of fuel and landed on a road after a carb developed a crack and burned through fuel faster than expected.

All that being said, if you consider the fuel gauge INOPERATIVE because it either reads nothing, something known to be completely wrong, or just out of tolerances of the general design poor as they may be, the legal answer is NOPE you can't fly on most light planes. Even if you don't ever want to use that tank.

 

[Dan Thomas]

No, wasn't the fuel cap. It has been a while since was flying the Cardinal and hanging around CFO, but it apparently was a design flaw that IIRC had something to do with the way the vent system was plumbed.


Sent from my iPad using Tapatalk HD

Most of those smaller Cessnas are all plumbed the same way. If they have a "Both" position on the selector, or just an "On-Off," they have one vent, under the left wing. That line goes into the outboard end of the left tank. The inboard end of the tank has a line that runs across the cabin roof to the inboard end of the right tank. If the caps and cap check valves are tight, the air pressure on the fuel in both tanks is equal except when the tanks are right full and that crossover line will have fuel in it. Until it drains down to the point that air is in the top of the tanks, the drawdown will be somewhat uneven since fuel can transfer between them. It can also transfer if the pilot doesn't fly wings level, via the fuel selector if it's on Both. And some pilots fly cockeyed. Used to see that as a flight instructor.

So if the flow is really uneven, it's most often due to a leaky cap or its check valve. And that usually shows up only on the right tank, since a leaking left cap will drop the pressure in the left tank and the right tank will be at the same pressure. If the right cap leaks, air flows from the left to the right across the vent line and causes a small pressure drop in the RH tank due to the friction in the line. Less pressure in that tank means a slower flow out of it. If that leaky cap leaks bad enough it will siphon fuel overboard and draw fuel from the left tank and lose it, too.

Dan

 

[Silvaire]

No, wasn't the fuel cap. It has been a while since was flying the Cardinal and hanging around CFO, but it apparently was a design flaw that IIRC had something to do with the way the vent system was plumbed.

The Cessna fuel vent problem and subsequent AD had to do with negative pressure venting. The replacement vented caps have a simple rubber flapper that will prevent the accumulation of negative (meaning less than ambient) pressure in the tank which could lead to either fuel starvation or collapsing of the tank. The cause of negative pressure would have been if the vent inlet or vent crossover were to become blocked. Prior to the AD the caps were non vented so drawing of fuel from the tank would create the condition in such a situation. In the lower powered models only one vented cap (the right one) is required but most have had both replaced.

 

[spiderweb]

The broken equipment / rental threads got me thinking about this, and as a renter...

Here's the scenario.

You check the plane out, do your runup, and everything is fine. You launch on your cross country flight and notice about halfway to your destination that one of your fuel gauges appears to be malfunctioning (fluctuating a lot but reading zero most of the time). You know that that tank should be almost full, and the other tank is reading almost full. What do you do? Turn around? Land? Continue?

Honestly, I ignore fuel gauges. I use a dipstick, or whatever else to visually confirm amount of fuel, then I calculate fuel flow per hour, with a big cushion for safety.

If I see fuel spilling out or feel an imbalance, time to land.

 

[Silvaire]

Honestly, I ignore fuel gauges. I use a dipstick, or whatever else to visually confirm amount of fuel, then I calculate fuel flow per hour, with a big cushion for safety.

If I see fuel spilling out or feel an imbalance, time to land.

I agree with all that except the ignore part. Like I said before, if you look at a fuel gauge and ask yourself "why is it doing that?" it's time to find out. Fuel siphoning out of a high wing is not something you're likely to see and I wouldn't want to wait until I felt an imbalance before suspecting something might be amiss.

But you're absolutely right about the rest. Even with a sophisticated engine analyzer with very accurate fuel flow capability, it doesn't actually know how much fuel you have, it only knows how much fuel you told it you had.

 

[wabower]

In that case you are wise to continue flying planes with chutes.

Honestly, I ignore fuel gauges. I use a dipstick, or whatever else to visually confirm amount of fuel, then I calculate fuel flow per hour, with a big cushion for safety.

If I see fuel spilling out or feel an imbalance, time to land.

 

[Hiperbiper]

Sorry, that's incorrect.

91.205 requires "Fuel gauge indicating the quantity of fuel in each tank" for the aircraft to be airworthy.

The confusion about "being accurate when empty" comes from Part 23, which requires (as part of Part 23 aircraft certification) that *unusable* fuel not be included in the gauge indication (if there's 10 gal of unusable fuel, the gauge reads empty when there's 10 gallons remaining).

CAR3 does not take unusable fuel into account, so the gauge can read 10 gals when you're actually at zero usable.

So, Part 91 requires accurate fuel gauges, and "no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation ... unless" they are present. The discussion is what does "accurate" mean, and there's no rulings I know of defining how accurate that is.
But a non-functioning gauge, or one that is all over the place cannot reasonably meet that definition.

We just went over this in A&P skool...
Part 23 only says the fuel indicator must read "0" when the tank has only unuseable fuel.
This is the only point where accuracy of the gauge(s) is noted in the regs.
Part 91 does not (as you noted) define what accurate means so the term is moot as the only actual definition of accurate has to do with the gauge indication vs. unuseable fuel (at empty). Otherwise the A&P/IA would be compelled to do a "fuel sender calibration check" at every annual. Not happening as of now that I know of. Different airplanes, different senders, different gauges, wiring going TU, temperture, everything contributes to erronious fuel level readings!
The "myth" seems to have a basis in fact to me...
The difference between a gauge doing swings or stuck at zero (maintaince problem) and just being not required to be 100% correct to be airworthy is a wide gap, with everything working as intended a 1977 C-172 the best you can hope for is a kinda', sorta', more-or-less agreement with the dip-stick you used during preflight to accurately portray what is actually in the tanks.


Chris

 

[PilotAlan]

It amazes me that with the number of fuel starvation/exhaustion accidents, pilots continue to treat functioning fuel gauges so cavalierly.

 

[Jim Logajan]

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used.​

Notwithstanding claims otherwise, why would the FAA use the highlighted words if it didn't intend them to have some level of precision appropriate to the task of aerial transportation?

 

[spiderweb]

In that case you are wise to continue flying planes with chutes.

I acknowledge your jibe. But I think if you actually read what I wrote you'll see that I'm embarrassingly anal rententive about fuel.

Let's start again:

1) I trust nothing except for the fuel I see in the tanks
2) I carefully calculate fuel burn, with generous cushions
3) I land the moment I think I screwed up with 1 and 2.

Pilots: KNOW how much fuel you have. KNOW what your fuel burn is. KNOW when things start to fall to pieces!

 

[Fearless Tower]

It amazes me that with the number of fuel starvation/exhaustion accidents, pilots continue to treat functioning fuel gauges so cavalierly.

The vast majority of fuel starvation accidents have nothing to do with fuel gauges.

 

[poadeleted20]

We just went over this in A&P skool...
The "myth" seems to have a basis in fact to me...

It may seem that way to you, but not to the FAA, and by law, they get to decide what those regs really mean. Ask your PMI if you need confirmation.

 

[wabower]

You said you ignore the fuel gages.

I can read.

Did you or did you not write that you ignore the fuel gages, stick the tanks, watch for leaks and land if you see a fuel leak or feel an imbalance?

Did you provide those same answers to the examiner during the oral portion of the exam for your current rating? If so, what questions and scenarios do you think he might have posed to cause you to be better prepared for the re-test?

I acknowledge your jibe. But I think if you actually read what I wrote you'll see that I'm embarrassingly anal rententive about fuel.

Let's start again:

1) I trust nothing except for the fuel I see in the tanks
2) I carefully calculate fuel burn, with generous cushions
3) I land the moment I think I screwed up with 1 and 2.

Pilots: KNOW how much fuel you have. KNOW what your fuel burn is. KNOW when things start to fall to pieces!

 

[PilotAlan]

The vast majority of fuel starvation accidents have nothing to do with fuel gauges.

That's a mighty big assumption. Do you know that for certain?

As you know, accidents are caused by chains of events.
I am willing to wager that a cavalier attitude toward functioning fuel gauges, and ignoring them when they were trying to tell the pilot about the impending accident, was part of the chain.

Some are just plain stupidity, to be sure. But can you honestly not see that unreliable or nonfunctioning fuel gauges eliminate the pilot's ability to see different failure modes, and may in fact CONTRIBUTE to fuel starvation accidents (as opposed to fuel exhaustion accidents).

 

[Dan Thomas]

Cessna demands (but they can't enforce it for private airplanes) a yearly check on fuel gauge accuracy. It's not a big deal for most of their puddlejumpers. With a long wire, suitably bent, you reach into the tank and lift the float all the way and then push it down and have a helper tell you what the gauge is doing. If it's misbehaving you fix it. The whole test takes less that ten minutes. The gauges can be made reasonably accurate with a little effort and the replacement of parts that are shot, just like any other indicating system.

Dan

 

[wabower]

Look at the location of the fuel exhaustion wrecks relative to their distance from the destination airport and explain how any other conclusion is feasible.

That's a mighty big assumption. Do you know that for certain?

As you know, accidents are caused by chains of events.
I am willing to wager that a cavalier attitude toward functioning fuel gauges, and ignoring them when they were trying to tell the pilot about the impending accident, was part of the chain.

Some are just plain stupidity, to be sure. But can you honestly not see that unreliable or nonfunctioning fuel gauges eliminate the pilot's ability to see different failure modes, and may in fact CONTRIBUTE to fuel starvation accidents (as opposed to fuel exhaustion accidents).

 

[PilotAlan]

Look at the location of the fuel exhaustion wrecks relative to their distance from the destination airport and explain how any other conclusion is feasible.

Let me ask the question again.
Do you truly believe that lack of functional and accurate fuel gauges, and the cavalier attitude toward gauges, doesn't add a link to the accident chain?

"I know the gauge says I'm empty, but my math says there's 30 more minutes of fuel in the tanks."
Or, if they had reliable gauges, they might have realized they were short on gas before it turned into an accident.

My point is that math gives you one datapoint, indicators give you another.
Do you use GPS or VOR when a heading and clock would give you a way of getting there? Why? Because more datapoints are better.

An error in fuel calculations, in the absence of reliable fuel indicators, leaves no warning to the PIC that something is wrong.
The statement that pilots end up short of gas short of the runway reinforces my argument, not yours.

 

[wabower]

I think you have it backwards. Once they fly over all the easy-stop enroute airports while constantly checking the gages (without respect to the indications) and decide to go for it, they have decided to ignore the gages. If a big red "YOU ARE GOING TO DIE! message appeared on the gage, they would ignore it too.

Let me ask the question again.
Do you truly believe that lack of functional and accurate fuel gauges, and the cavalier attitude toward gauges, doesn't add a link to the accident chain?

"I know the gauge says I'm empty, but my math says there's 30 more minutes of fuel in the tanks."
Or, if they had reliable gauges, they might have realized they were short on gas before it turned into an accident.

My point is that math gives you one datapoint, indicators give you another.
Do you use GPS or VOR when a heading and clock would give you a way of getting there? Why? Because more datapoints are better.

An error in fuel calculations, in the absence of reliable fuel indicators, leaves no warning to the PIC that something is wrong.
The statement that pilots end up short of gas short of the runway reinforces my argument, not yours.

 

[PilotAlan]

I think you have it backwards.

Respectfully, I think it's the other way around. Generations of pilots have been told that the gauges don't mean a thing, and are worthless.
So for some pilots, when their math says one thing and the gauge says something else, they ignore it.

Obviously there's as many accident chains as there are accidents. But the logical conclusion of your argument is that there might as well be no gauges, and that there's no need to have them work.

Can you really say that having functioning, reasonably accurate gauges somehow make the aircraft LESS safe?
Or more specifically, that having inaccurate or inop gauges has NO negative effect of safety?

 

[wabower]

I think your generational premise is pure speculation.

Pilots who have been around for a while (or some of us, anyway) understand that some gages and the installed systems that drive them are dead-on and some are guesstimates at best, and that no amount of tweaking or adjusting will make them better. The STC'd gravity-flow Monarch systems provide more than ample evidence of the inherent flaw in your "I spend whatever is necessary to make them right" because physics precludes it.

Furthermore, pilots obviously ignore math and other logical decision-making criteria no matter where the needles are pointing, simply because they decide to do so. Like the old truck height vs overpass height joke, "I don't see any cops around, let's go for it" is the only logical conclusion from the accident reports.

As to proof, can you really say that accurate gages make the airplanes that crash due to fuel exhaustion more safe? If so, why do those with accurate gages crash?

Respectfully, I think it's the other way around. Generations of pilots have been told that the gauges don't mean a thing, and are worthless.
So for some pilots, when their math says one thing and the gauge says something else, they ignore it.

Obviously there's as many accident chains as there are accidents. But the logical conclusion of your argument is that there might as well be no gauges, and that there's no need to have them work.
Can you really say that having functioning, reasonably accurate gauges somehow make the aircraft LESS safe?

 

[spiderweb]

You said you ignore the fuel gages.

I can read.

Did you or did you not write that you ignore the fuel gages, stick the tanks, watch for leaks and land if you see a fuel leak or feel an imbalance?

Did you provide those same answers to the examiner during the oral portion of the exam for your current rating? If so, what questions and scenarios do you think he might have posed to cause you to be better prepared for the re-test?

Wayne, my beloved friend--I will refine this for you, since you seem so overtly alarmed by my response. I should have said "mistrust" instead of "ignore."

Fuel gauges are not reliable in piston singles, as a rule. I trust what I see before I fire up, and what I know should be the fuel burn, with a cushion. If you don't do this, and if you rely only on fuel gauges, then you do so at your own risk, and THAT is what you should have told YOUR examiner.

If, suddenly, there IS NO FUEL IN THE LEFT TANK ACCORDING TO A GAUGE, but I see no fuel spilling overboard and feel no imbalance, I will do this--I will cautiously evaluate the situation, and formulate a plan. If an immediate landing is warranted, the I will do just that.

 

[wabower]

I agree with mistrust.

Wayne, my beloved friend--I will refine this for you, since you seem so overtly alarmed by my response. I should have said "mistrust" instead of "ignore."

Fuel gauges are not reliable in piston singles, as a rule. I trust what I see before I fire up, and what I know should be the fuel burn, with a cushion. If you don't do this, and if you rely only on fuel gauges, then you do so at your own risk, and THAT is what you should have told YOUR examiner.

If, suddenly, there IS NO FUEL IN THE LEFT TANK ACCORDING TO A GAUGE, but I see no fuel spilling overboard and feel no imbalance, I will do this--I will cautiously evaluate the situation, and formulate a plan. If an immediate landing is warranted, the I will do just that.

 

[spiderweb]

I agree with mistrust.

Thanks. You're right that I shouldn't have said, "ignore." We should use every tool and gauge in the cockpit, but understand how and why any of those elements might be wrong.

 

[JHW]

...As to proof, can you really say that accurate gages make the airplanes that crash due to fuel exhaustion more safe? If so, why do those with accurate gages crash?

to wayne's point, I suspect if you compare fuel starvation accidents between 310's and barons, 2 models used about as similarly as you can find, I would bet that the 310's run out of gas at the same rate, probably more due to the somewhat convoluted fuel system. The 310's capacitance-type fuel gages are pretty darn good, probably as good as you'll find in the piston world. The beechcraft fuel gages are.....not among the best you'll find.

 

[Hiperbiper]

Hiperbiper: Highlighted and underlined are mine.

(b) Fuel quantity indication. There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. An indicator calibrated in appropriate units and clearly marked to indicate those units must be used.
Notwithstanding claims otherwise, why would the FAA use the highlighted words if it didn't intend them to have some level of precision appropriate to the task of aerial transportation?

Your quote is from 23.1337. An Indicator is a gauge or human interface. and yes it must be "calibrated in appropriate UNITS". i.e. gallons, pounds, ect...

The only reference tied to 23.1337 is 23.959 which is the one that says the fuel Gauges must be calibrated to read empty when only un-usable fuel is left in the fuel tanks. This is the only reference calling for any system calibration at all.

Nothing in the wording of 23.1337 states any required accuracy, validity or positive indication of the INDICATION "SYSTEM" except for (ref.) 23.959 which is the unusable fuel reg.

The OP asked about an inop fuel gauge. answer: not airworthy per 91.205.

Then we went to how accurate the fuel gauges have to be. answer: it has to indicate 0 just before the motor expires. There is no required check by part 23,91 or 43. The needle just has to move.


As to a crash caused by running out of fuel; the FAA makes it's own rules and these vary from coast to coast, state to state and even person to person. Lawyers on the other hand would make the case that 23.1337 requires an "accurate and calibrated indication of fuel state" to 12 people (none pilots BTW) that think their car fuel gauge sucks but airplane should be better. Most are not.

We had 3 planes that left DTN in the past few years that went down due to running out of gas; an SNJ going to MO, a PA28 going to TN and a 337 going to FL. Every one "landed" within 10nm of where they should have given full fuel vs. fuel burn.
I don't think the fuel gauges were at fault in any of the 3...

Chris