Fuel Gauges
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Fuel Gauges
How reliable are the fuel guages in say a PA-28? during my training my instructor told me never to trust what they said as they are inaccurate, then when he started air charter work I had another instructor who said "oh yes, you should always look and rely on them", basically who is right? at the moment all my fuel planning is done manually using my planned data etc.
What if I wanted to substitute some fuel weight to enable me to carry more pax? if you didnt use the gauges how can you asscertain how much fuel is in the aircraft an how much more to put in, as after the last flight the aircraft is topped up right away by the fuel truck, basically I want to take my wife and my brother & sister in-law in a warrior to the Isle Of White sometime and Im just thinking maybe the plane could be overloaded with 4 adults and fuel to tabs
thanks in advance for you time to reply
Dean
What if I wanted to substitute some fuel weight to enable me to carry more pax? if you didnt use the gauges how can you asscertain how much fuel is in the aircraft an how much more to put in, as after the last flight the aircraft is topped up right away by the fuel truck, basically I want to take my wife and my brother & sister in-law in a warrior to the Isle Of White sometime and Im just thinking maybe the plane could be overloaded with 4 adults and fuel to tabs
thanks in advance for you time to reply
Dean
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Do not trust the gauges. Get a dipstick made or buy one that someone else has already done the calibration for.
You don't say whether it's a group or club aircraft. If it's club and it flies just before you then I'd suggest doing your weight and balance beforehand and then loitering around for when it gets back - making sure only the fuel you want is put in. Either that or get accurate weights for you plus pax - you might find tabs fuel is ok.
You don't say whether it's a group or club aircraft. If it's club and it flies just before you then I'd suggest doing your weight and balance beforehand and then loitering around for when it gets back - making sure only the fuel you want is put in. Either that or get accurate weights for you plus pax - you might find tabs fuel is ok.
Last edited by Chilli Monster; 3rd Dec 2003 at 07:21.
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I was told that the only time to trust a fuel gauge is when it reads empty!
No reason to go fly with empty fuel tanks? And if stopping somewhere in most lighties, look inside to verify there is fuel. Leaks have been known to happen! Use a dipstick. C182 and others with landing weight restrictions really need a dipstick to back up the gauges. High wings are tough to visually check, so dipstick is again quite important.
As you know what the fuel burn is, and how long you have been turning and burning (add a 15% fudge factor) you can mentally verify what the tanks (and gauges) should be telling you.
Oh yeah, W&B is MUCHO important - especially with 4 up in a warrior. Hope your passengers are all svelte!
No reason to go fly with empty fuel tanks? And if stopping somewhere in most lighties, look inside to verify there is fuel. Leaks have been known to happen! Use a dipstick. C182 and others with landing weight restrictions really need a dipstick to back up the gauges. High wings are tough to visually check, so dipstick is again quite important.
As you know what the fuel burn is, and how long you have been turning and burning (add a 15% fudge factor) you can mentally verify what the tanks (and gauges) should be telling you.
Oh yeah, W&B is MUCHO important - especially with 4 up in a warrior. Hope your passengers are all svelte!
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I wouldn't rely on them, though the ones in the a/c I fly seem to be quite accurate.
In any event, if the gauge says you have 4 gals left (20 mins in a 182) are you really going to push it another quarter hour?
Wasn't there a case in England recently where a doctor put a twin into a house because it ran dry? It was a rental and the owners wouldn't allow full fuel between renters.
In any event, if the gauge says you have 4 gals left (20 mins in a 182) are you really going to push it another quarter hour?
Wasn't there a case in England recently where a doctor put a twin into a house because it ran dry? It was a rental and the owners wouldn't allow full fuel between renters.
Between your calculations, dipstick & fuel gauges trust whichever one gives the least amount of fuel remaining (for endurance & range). Trust whichever one gives the most amount of fuel (for weight & performance)
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Thanks for the comments guys, yes it is a club aircraft, and the W +B issue is why Im asking the question, we may just be inside the W + B limitation for takeoff but are definately inside it for landing, this much I have asscertained (subject to adverse wind / ground speed on the day of dep), its only a 40-50 minute flight to the IOW from my departure aerodrome so no need to refuel whilst there, being too heavy will only be an issue on the way down
Thanks for the tips
Dean.
Thanks for the tips
Dean.
Below I've pasted the total requirements (apart from deleting some paragraph cross references) from FAR-23, which is the safety code against which most light aircraft worldwide are certified, that affect fuel gauge accuracy. It wouldn't do to expect more than the aircraft was certified to do...
G
23.963 (e) Each fuel quantity indicator must be adjusted, as specified ... to account for the unusable fuel supply...
23.1305(1) A fuel quantity indicator (must be supplied) for each fuel tank
23.1337(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. In addition:
(1) Each fuel quantity indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined
23.1553 Fuel quantity indicator.
A red radial line must be marked on each indicator at the calibrated zero reading,
23.1551 (1) For fuel systems having no selector controls, the usable fuel capacity of the system must be indicated at the fuel quantity indicator
G
23.963 (e) Each fuel quantity indicator must be adjusted, as specified ... to account for the unusable fuel supply...
23.1305(1) A fuel quantity indicator (must be supplied) for each fuel tank
23.1337(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. In addition:
(1) Each fuel quantity indicator must be calibrated to read "zero" during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined
23.1553 Fuel quantity indicator.
A red radial line must be marked on each indicator at the calibrated zero reading,
23.1551 (1) For fuel systems having no selector controls, the usable fuel capacity of the system must be indicated at the fuel quantity indicator
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On the PA-28's I've flown (Warrior and -180) full fuel was 50USG and tabs was 34USG. Handily enough, four average adults leaves you room for 34USG or so of fuel - i.e. as a rule of thumb fuel to tabs is OK unless one or more of your adults is on the heavy side. I guess that's why the tabs are where they are (remember this would have been calculated in the 60's when people were perhaps lighter!).
Of course you should still do a W&B calculation the first few times you travel 3- or 4-up - but you may well find that the above works for your aircraft too.
Tim
Of course you should still do a W&B calculation the first few times you travel 3- or 4-up - but you may well find that the above works for your aircraft too.
Tim
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As Genghis points out, the only time a fuel guage must legally be accurate is when its reading empty...by them I think you will have other things on your mind!!!
ALWAYS check your fuel quantity using visual and dipstick.
There was a previous discussion thread running saying that on some models this can be very hard to do anyway.
ALWAYS check your fuel quantity using visual and dipstick.
There was a previous discussion thread running saying that on some models this can be very hard to do anyway.
Incidentally, a lot of aircraft use capacitance based gauges, which read differently with different brands of fuel, water content, cycle of the moon, etc. anyway.
G
N.B. Re-reading my previous post, I find myself wondering how you achieve level flight with an empty fuel tank anyway? Slightly spurious requirement one might argue !
G
N.B. Re-reading my previous post, I find myself wondering how you achieve level flight with an empty fuel tank anyway? Slightly spurious requirement one might argue !
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ALWAYS check your fuel quantity using visual and dipstick.
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Deano777
Never trust fuel gauges for ANYTHING. They are usually either completely useless, or nearly so. Flying school/club planes are often maintained to the minimum standard legally possible and gauges aren't important.
The way to do it, always, is to work out how much fuel is needed for the proposed flight, and make sure you have it (plus a decent reserve), using a PHYSICAL (visual) check. Always visually check the tank content before every flight. Never accept anyone else's word for it - not even that of an instructor! Even if an instructor says there is enough for 3 hrs, the tech log says 3 hrs, and the daily flight log says 3 hrs, still check it because all of these could be wrong (I've seen it myself).
If permitted by W&B, always fill up to the top. Then you have a known endurance (hours airborne) at a given engine power setting. Make sure you know what these are (the endurance in hours, and the cruise power setting in RPM or whatever, and the mixture setting if not full rich).
If you cannot fill up to the top, be extra careful. Regardless of how you have done your calculations, ALWAYS visually check what's in the tank before departure. I know on many planes the fuel level isn't visible through the filler cap once at or below say 50%, and on some the W&B are so severely limited that those planes often "have" to be operated below 50%, but then you are taking on a very big risk. The incident referred to in this thread was partially caused by the fact that the fuel level could not be checked.
The reason fuel gauges are usually c**p and few people seem to care is that one should not need them for flight/fuel planning, and once airborne they are no more than handy for knowing when to switch tanks. For the latter alone they ought to work but usually they aren't even OK for that; when I used to rent I used to carry a kitchen timer set to 30 mins.
Genghis
I have capacitance gauges and they are highly accurate, in fact as accurate as I can read the dials. These are the only fuel gauges which I have seen (on about 10-15 diff planes) which are actually usable.
They should not be susceptible to fuel grade etc unless they were defective to the point of falling apart. Have you any specific information that diff brands of fuel affect these gauges?
Never trust fuel gauges for ANYTHING. They are usually either completely useless, or nearly so. Flying school/club planes are often maintained to the minimum standard legally possible and gauges aren't important.
The way to do it, always, is to work out how much fuel is needed for the proposed flight, and make sure you have it (plus a decent reserve), using a PHYSICAL (visual) check. Always visually check the tank content before every flight. Never accept anyone else's word for it - not even that of an instructor! Even if an instructor says there is enough for 3 hrs, the tech log says 3 hrs, and the daily flight log says 3 hrs, still check it because all of these could be wrong (I've seen it myself).
If permitted by W&B, always fill up to the top. Then you have a known endurance (hours airborne) at a given engine power setting. Make sure you know what these are (the endurance in hours, and the cruise power setting in RPM or whatever, and the mixture setting if not full rich).
If you cannot fill up to the top, be extra careful. Regardless of how you have done your calculations, ALWAYS visually check what's in the tank before departure. I know on many planes the fuel level isn't visible through the filler cap once at or below say 50%, and on some the W&B are so severely limited that those planes often "have" to be operated below 50%, but then you are taking on a very big risk. The incident referred to in this thread was partially caused by the fact that the fuel level could not be checked.
The reason fuel gauges are usually c**p and few people seem to care is that one should not need them for flight/fuel planning, and once airborne they are no more than handy for knowing when to switch tanks. For the latter alone they ought to work but usually they aren't even OK for that; when I used to rent I used to carry a kitchen timer set to 30 mins.
Genghis
I have capacitance gauges and they are highly accurate, in fact as accurate as I can read the dials. These are the only fuel gauges which I have seen (on about 10-15 diff planes) which are actually usable.
They should not be susceptible to fuel grade etc unless they were defective to the point of falling apart. Have you any specific information that diff brands of fuel affect these gauges?
Why do it if it's not fun?
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Capacitance guages are good - I have one on my Europa, and it is essential because it's not possible to visually check the fuel level. But be careful - the scale is not linear! It is vital that the guage is calibrated properly, and you must read the calibration data before you start interpreting what the guage is telling you.
FFF
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FFF
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I recently changed the gauages and senders on my Cessna for new ones and have found them to be totally accurate. I have a FS450 fuel computer which is totally accurate and the gauges compare bang on with the fuel computer.
But it still does not stop me from dipping the tanks on every flight. I guess the fear of falling out of the sky after omitting a visual check that the gadgets are telling the truth is still as strong as it was when I first learnt!!
But it still does not stop me from dipping the tanks on every flight. I guess the fear of falling out of the sky after omitting a visual check that the gadgets are telling the truth is still as strong as it was when I first learnt!!
I believe it's down to alcohol and water content, which can vary a lot depending upon the particular fuel company's procedures, and the airfield's storage of fuel. Increasing the water content fuel alters the dielectric constant of the fuel.
I heard this authoritatively from the engineer who signed off the design of your aeroplane FFF !
G
I heard this authoritatively from the engineer who signed off the design of your aeroplane FFF !
G
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It continues to be an absolute scandal that after all these years the majority of mainstream light aircraft still have poor fuel indication systems. What is the point in having a fuel gauge fitted if you carnt trust it ?
With the technology available now, why o why can we not now have cheap but reliable sytems available for such a vital area.
Fuel starvation incidents continue abound every year so come on
piper/cessna/authorities etc, as the decades go past can we sort it out !!
With the technology available now, why o why can we not now have cheap but reliable sytems available for such a vital area.
Fuel starvation incidents continue abound every year so come on
piper/cessna/authorities etc, as the decades go past can we sort it out !!
Why do it if it's not fun?
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I heard this authoritatively from the engineer who signed off the design of your aeroplane FFF !
FFF
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what a wonderful response thanks alot guys theres nothing I can really add here apart from the fact that I always do the visual check on my walk around, and if it aint tabs or higher I dont fly (well I do, I get them to top it up 
)
Tim
Obviously W+B is very important with 4 up (it is with any No. of pax) and is a legal requirement, I have an excel spreadsheet which does the calculations for me so I print off 2 copies, one comes with me in the a/c and one stays at home, just incase
If anyone wants a copy of this spreadsheet dont hesitate to ask and I will send it to you or upload it to some webspace, its bloody marvelous
oh btw its for a PA-28 Warrior II and I also have one for the PA-28 140 Cherokee
Regards
Dean.
theres nothing I can really add here apart from the fact that I always do the visual check on my walk around, and if it aint tabs or higher I dont fly (well I do, I get them to top it up )Tim
Obviously W+B is very important with 4 up (it is with any No. of pax) and is a legal requirement, I have an excel spreadsheet which does the calculations for me so I print off 2 copies, one comes with me in the a/c and one stays at home, just incase
If anyone wants a copy of this spreadsheet dont hesitate to ask and I will send it to you or upload it to some webspace, its bloody marvelous
oh btw its for a PA-28 Warrior II and I also have one for the PA-28 140 Cherokee
Regards
Dean.
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Always visually check the tank content before every flight. Never accept anyone else's word for it
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Well, if you're picking up the aircraft from the pump and you've seen the refueller's signature in the book it might seem somewhat untrusting to climb up and look inside the tank whilst the guy's watching you
Any pump operator who thinks this is un-trusting should be working at a petrol station, not at an airfield
Any pump operator who thinks this is un-trusting should be working at a petrol station, not at an airfield