How to ACCURATELY measure fuel/gas in a single-engine piston aircraft?

NoSpam wrote:

Is there a way to accurately measure the fuel in the tanks while the aircraft
is on the ground (using some "mechanical" measuring tool/gauge)?

Yes. Make or buy some sort of dipstick. Mine is a clear plastic tube. I bought it
and drained one of my fuel tanks. We then pumped in 5 gallons and marked where the
level was when I stuck the tube in. Put in another 5 gallons and marked that. And
so forth. Now I can stick the tube in the tank, pull it out, and know within a
gallon or two how much is in that tank.

Is there a way to
accurately measure the amount of fuel in the tanks while in flight?

No. As others have stated, use your watch and the gauges. Whichever indicates the
least amount of fuel is what you "believe". Land if you even think you *might* be
getting low.

George Patterson
Great discoveries are not announced with "Eureka!". What's usually said is
"Hummmmm... That's interesting...."

John, who had more ratings than I ever will, approached a homebuilt with the
mindset that he was dealing with a certified aircraft - that don't have
such 'gotchas'...
Denny
"C J Campbell" wrote The gauge
should be calibrated and marked with the fuel
quantity at several different levels, but no one had done this on Denver's
plane.

Newps ) wrote:

I bought the fuel hawk for my 182. Total waste of money.

LOL! Hence the value of Usenet.

Just out of curiosity, was the FuelHawk you bought *specifically* for your
model 182? The one I bought only listed late model 172SPs.

In my case, I did confirm the stick's readings on a few occasions by
reading the remaining, then refilling the tanks. The amount of gallons
going in equaled total capacity minus my stick's reading. This was done
for varying amounts of remaining fuel over a few flights.

--
Peter












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Peter R. wrote in message ...
NoSpam wrote:

Is there a way to ACCURATELY measure the available fuel in the tanks of a
general single-engine piston aircraft???

Just after receiving my private pilot certificate, I bought a FuelHawk
to accurately measure remaining fuel in my Skyhawk's tanks:

http://makeashorterlink.com/?O202128F6
...
I would be very uncomfortable flying one of these missions without it.

Peter,

I would be very uncomfortable relying on that FuelHawk unless you
have personally calibrated it in your plane and know it to be accurate.
We used to rent C172s, we had a FuelHawk, and the reading would be
different in different tanks which had the same amount of fuel left
as judged by how much fuel was added to 'top off', even different tanks
in the same plane.

I think Greg Travis posted a similar observation regarding his 180 HP
C172.

When we bought our Grumman, we calibrated the FuelHawk by noting the
reading before each top-off then doing a polynomial fit once we got
enough readings across the range. The other method of course is to
fly one tank dry then pour in fuel 1 gallon at a time, taking due
precautions against static. The latter method is quicker, both methods
are quite accurate if carefully done.

Once the stick (any stick -- fuel hawk, paint stirrer, etc) is
calibrated, it is quite accurate and I recommend it even to people
who always take off with full tanks, to determine whether they
actually landed with the amount of time in the tanks that they
thought they had. This has been a revelation to us a couple of
times (though, when the tank under the stick is dry, I still have
between 0 and 14 gallons, just our tank design).

Cheers,
Sydney

Snowbird ) wrote:

I would be very uncomfortable relying on that FuelHawk unless you
have personally calibrated it in your plane and know it to be accurate.

Thanks, Sydney. See my reply to NewPS.

--
Peter












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"NoSpam" wrote in message ...
Is there a way
to accurately measure the fuel in the tanks while the aircraft is on the
ground (using some "mechanical" measuring tool/gauge)?

Yes, using a dipstick calibrated *for that aircraft*. This is quite
accurate w/in the range it can measure (for example, when my dipstick
reads 0 on each tank, I have between 0 and 14 gallons of fuel left.

Is there a way to
accurately measure the amount of fuel in the tanks while in flight?

Not of which I'm aware. As you note, fuel computers measure fuel
flow, but don't account for fuel loss due to, say, leakage around
an improperly sealed gas cap or sump valve.

A friend of mine has bought some digital fuel gauges (a combination a
several digital engine instruments -- but I forgot the manufacturer's name).
Using these fuel gauges, you "calibrate" the instrument/gauges by leveling
the aircraft (both "wings level" and "pitch/flying attitude level") and
starting with 0 gals of fuel in the tank, then adding one gallon at a time,
wait a while for the fuel to settle, then take an electronic reading, add 1
gal of fuel and repeat the process until the tanks are full. How accurate
is this method? (personally I do not know how accurate this is, but would
like to know from someone with experience using these instruments...)

The method of adding 1 gallon and taking a reading on the ground is
accurate enough -- it's one way of calibrating a fuel dipstick.

I'm not sure how accurately it would translate to monitoring fuel in
flight -- the pitch attitude for level flight will vary so much
depending upon the atmosphere, the W&B, airspeed, and so forth.
It seems to me the design of the fuel tanks and the placement of
the gauge would be critical to accuracy, but I'm unfamiliar with the
technology used to make what you call an "electronic reading". That's
the point I'd want to investigate, though -- how much do the readings
I get with this wonder differ if I change the plane's pitch?

Cheers,
Sydney

I use a fuel stick to measure the fuel and put that information in my
fuel flow computer. I'm usually within a tenth of a gallon on landing.
Its pretty easy to make your own fuel stick, the best ones are wood.
I've made some out of the paint stir sticks you get at the home
improvement stores (they look like rulers). The best part about wood
is once you measure the fuel you just shake it and the fuel stain is
gone and ready for the next tank. The glass ones that you have to
stick your thumb in kinda suck.

-Robert

Newps ) wrote:

I bought the fuel hawk for my 182. Total waste of money.

I use a fuelhawk with general markings. I have a calibration table for a
specific Cessna 172 with long range tanks. I use it for any Cessna with
long range tanks, and use it for others with standard tanks by multiplying
the amount by 0.8. Is it accurate? Certainly not. Is it better than the
fuel gauges or my unaided eye? Sure is. So, by being conservative about
fuel burn and possible inaccuracy this tells me wether I have enough fuel
for the trip. Works thus far ;-)

Ok. I give up. How did it fail? The cork stick to the tube or what kept the
gas from draining through the bottom of the guage?

In article , "karl"
wrote:
******Doesn't it have a float on a wire? Not the same******

Exactly the same.You really should go have a look. No wire. Just a sight
gauge with a red colored cork floating. I spent my pilot youth ferrying
these fine airplanes from Lock Haven to Washington. Oregon, Alaska.

The float on a wire is on a J3, Taylorcraft, Aeronca, usually on a forward
fuselage tank. Super Cub tanks are in the wings.

Karl

By acurate I mean within one galon of actual fuel quantity.

I am only asking for interest sake. Whenever I fly our club's Archer, I
calculated the amount of fuel remaining by starting with a full tank and
then estimating the fuel burn per hour, etc. etc. But this has always left
me feeling nervous -- the aircraft did not have an accurate fuel flow
instrument (e.g. JPI) on board, and as a result a was always
"guestimating" -- although I was on the conservative side...

Thanks

Cameron


"Jim Weir" wrote in message
...
Two questions:

What is "accurate"?

Why do you need "accuracy"?

Jim


"NoSpam"
shared these priceless pearls of wisdom:

-Is there a way to ACCURATELY measure the available fuel in the tanks of
a
-general single-engine piston aircraft???



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com




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