How much fuel is in my Archer's tank?

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SkyVoyager

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How much fuel is in the Archer's tanks?

I thought this was easy, but nothing in aviation seems to be!

I have this lovely placard on my '76 Archer's wing that says the tabs are 17 gallons of fuel in the tank. I know from my manual that I should be able to put 50 gallons in between the tanks, but I only have 48 useful. Check.

So...That should mean that after fueling to the tabs, I should have room for an additional 8 gallons per tank (or is it seven? are those tabs useful fuel or total fuel??)

As an experiment yesterday, I was able to put in six gallons over the tabs and not any more. That would give me either 23 gallons (if you consider total) or 24 gallons (if you assume one gallon is taken in consideration somewhere). I'm still missing something.

I have a friend who has a '82 Warrior. I thought they were the same tanks. But...his POH states the tabs are 19 gallons. Six additional gallons over the tabs would make complete sense. My manual does not seem to make any mention of the tabs, only the placard.

If I make the assumption the tabs give me 17 gallons, 6 more in each only gives me 46 gallons. What am I missing? Is this a stupid question? (I would never get the fuel that low to make a difference either way...I'm just curious!)

Thanks!
 
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Sometimes the shock on the archer make one wing higher than the other if you made any fast turns taxiing. Did you fill up both sides?
 
The tabs provide an easy method of insuring that you do not have too much fuel from a weight-and-balance viewpoint. If you had a trip coming up tomorrow and you knew that one of the passengers weighed 300 pounds, you might tell the fueler to "fill it to the tabs," because if the tanks were topped off you would be over gross.

Unusable fuel is unusable fuel, tabs or no tabs...it doesn't magically become usable.

Bob Gardner
 
Much depends on how the airplane is sitting on the fuel ramp. Most are not completely level.
 
The tabs should mark total fuel in the tank, so the placard says 17, which includes the unusable fuel. If you could only put in 6 additional gallons, were the wings level? Some times the Piper struts do not compress the same after landing and the plane is not level.

If a placard is on the wing, it should be in the POH also with a reference to partial fuel loading. Granted older POH are not as complete as the newer models.
 
The Arrow has similar tabs. First time I saw it, I thought it was a real clunker. I rent it for training. It's really easy to work with though. Fill it to the tabs and two people get 3-4 hours of fuel, it's a no brainier. Top it off and one person gets about 5-6.
 
Re: How much fuel is in the Archer's tanks?

SkyVoyager said:
I thought this was easy, but nothing in aviation seems to be!

I have this lovely placard on my '76 Archer's wing that says the tabs are 17 gallons of fuel in the tank. I know from my manual that I should be able to put 50 gallons in between the tanks, but I only have 48 useful. Check.

So...That should mean that after fueling to the tabs, I should have room for an additional 8 gallons per tank (or is it seven? are those tabs useful fuel or total fuel??)

As an experiment yesterday, I was able to put in six gallons over the tabs and not any more. That would give me either 23 gallons (if you consider total) or 24 gallons (if you assume one gallon is taken in consideration somewhere). I'm still missing something.

I have a friend who has a '82 Warrior. I thought they were the same tanks. But...his POH states the tabs are 19 gallons. Six additional gallons over the tabs would make complete sense. My manual does not seem to make any mention of the tabs, only the placard.

If I make the assumption the tabs give me 17 gallons, 6 more in each only gives me 46 gallons. What am I missing? Is this a stupid question? (I would never get the fuel that low to make a difference either way...I'm just curious!)

Thanks!
Click to expand...

The information you are missing is the temperature and API index of your fuel.
 
Only way to know for certian is drain the tanks, then re-fill with the airplane sitting level (more or less). Most Cherokees (the ones I've delt with anyway) will be about 36 gallons total when filled to the tabs, and 50 when topped. That will vary some depending upon how the airplane is sitting when it's filled.
 
My Warrior is 34 useable filled to the tabs.
 
Re: How much fuel is in the Archer's tanks?

Yeah, right. Huge deal in a Cherokee that's filled to the tabs--or any other light single for that matter. :rofl:
Henning said:
The information you are missing is the temperature and API index of your fuel.
Click to expand...
 
Re: How much fuel is in the Archer's tanks?

wabower said:
Yeah, right. Huge deal in a Cherokee that's filled to the tabs--or any other light single for that matter. :rofl:
Click to expand...

If you are going for more precision than is given its required, otherwise you go by the book number and leave it alone.
 
My old Cherokee 140 was 18 gal exactly to the tabs when sitting level on the ground, 25 topped off per side. I had one of these also (http://www.aircraftspruce.com/catalog/pspages/fuelindicatorpa28.php) and it was accurate to within +/- a gallon or two which is plenty close enough for practical use in dipping the tanks.

The 2 gallons "unusable" in a PA28 is a fair enough estimate for safety, but if you keep the plane nice and level in flight, it will suck a tank down to about 1/2 cup in a tank before the engine goes silent ;)

Methinks the PA28 tanks are all alike, however the tabs may be slightly up or down, depending on batch manufactured, and the POH and placards were written by lawyers to err on the cautious side or by salesmen/marketeers to sell more planes depending on corporate mood of the time. The original tab measurement was 18 gallons but the distance between the fuel barely touching the bottom of the tab's metal versus just barely flowing over the top of the metal could be +/- a gallon or thereabouts.
 
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BillTIZ said:
The tabs should mark total fuel in the tank, so the placard says 17, which includes the unusable fuel. If you could only put in 6 additional gallons, were the wings level? Some times the Piper struts do not compress the same after landing and the plane is not level.

If a placard is on the wing, it should be in the POH also with a reference to partial fuel loading. Granted older POH are not as complete as the newer models.
Click to expand...

I have to disagree with you, but I have no documentary evidence. The only Piper POH I have is for a Warrior. However, it is possible to add fuel after the level reaches the tabs, so it is not likely that the tabs indicate total fuel capacity.

Bob Gardner
 
bobmrg said:
I have to disagree with you, but I have no documentary evidence. The only Piper POH I have is for a Warrior. However, it is possible to add fuel after the level reaches the tabs, so it is not likely that the tabs indicate total fuel capacity.

Bob Gardner
Click to expand...

Total fuel in the tank, when filled to the tabs, should include unusable fuel.
I said nothing about TOTAL CAPACITY, but total fuel in the tank, usable plus unusable when using the TABS to determine a partial fuel load. (Other than dipping the tanks with a calibrated stick.)
 
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Fill the tanks...................50 gal remaining, 48 usable
Fill to tabs......................36 gal remaining, 34 usable
Run to engine quits............2 gal remaining, 0 usable
 
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kgruber said:
Much depends on how the airplane is sitting on the fuel ramp. Most are not completely level.
Click to expand...
In fact, they should not be completely level. They are constructed so that a fuel spill would run in a particular direction for containment purposes.
 
I thought this was going to be one of those things where if I guess the right amount I win the Archer. On the off chance you guys all screwed it up I'm going to put my bid in at 50 gal.


I think I may be light though as the OP stated he puts fuel in between his tanks too. Oh crud, I'm never going to win.
 
kgruber said:
Fill the tanks...................50 gal remaining 48 usable
Fill to tabs......................36 gal remaining 34 usable
Run to engine quits............2 gal remaining 0 usable
Click to expand...

Give that man a cigar! (But don't light up on the ramp.) You have some experience in PA-28s, kgruber? :wink2:

Bob Gardner
 
bobmrg said:
Give that man a cigar! (But don't light up on the ramp.) You have some experience in PA-28s, kgruber? :wink2:

Bob Gardner
Click to expand...

I was going to go into my "unusable" verus "undrainable" fuel spiel, but am leaving that to the experts.
 
kgruber said:
Fill the tanks...................50 gal remaining, 48 usable
Fill to tabs......................36 gal remaining, 34 usable
Run to engine quits............2 gal remaining, 0 usable
Click to expand...

Zero useable is predicated on the airplane's most unfavorable attitude for fuel leaving the tank, like in either a climb or flaps-down glide. In level flight you'll burn much farther into the "unusable" fuel. Then the engine quits on approach.

Dan
 
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