Time, running out of fuel and fuel gauges

[Dylan Smith]

A couple of points with regard to running out of fuel:

1. I think many pilots forget about the time factor (i.e. keeping track
of it) once they are a few months out of student training.
2. I think teaching that the fuel gauges are useless (which is very
common) is teaching a dangerous myth.

With point (1), if you keep good track of time it's almost impossible to
get lost, certainly during daylight VFR. My instructor certainly harped
onto me about the importance of keeping note of time (not just time off,
but time passing X on your route). Many pilots I've flown with don't (or
worse still rely on VOR/DME or GPS).

With point (2), so far I've only flown one aircraft with truly useless
fuel gauges. Few people ever bother looking at them because:
1. they do a visual fuel inspection before the flight
2. they know the fuel burn and endurance of the aircraft
3. they have been taught that the fuel gauges are useless

But 3. is most often wrong. Even though I've never been in a light plane
with particularly precise fuel gauges, all but one light plane I've
flown has had fuel gauges which were good enough for performing a cross
check.

I'll now tell you a story about how I avoided running out of fuel.

About 3 years ago, I got checked out in a C182, the 1960 model (which
was the only year model to have a swept tail but no rear window, if I
remember correctly). It also doesn't have fuel tanks as big as the later
C182. However, I knew all of this as well as pertinent information (such
as fuel burn) from reading the manual before getting checked out. Our
flying club required a short open-book written exam for any plane you
were getting checked out in to get everyone to at least look and try and
remember all the pertinent information, including computing a weight and
balance and fuel burn calculations.

So a couple of weeks after first getting checked out, I have the plane
booked for a long trip from Houston to Utah. Knowing I wouldn't be able
to get fuel the next morning since I was setting out at 6am, I went out
to Houston Gulf the night before and checked the fuel so I could get it
topped off if necesary. I got on the little ladder and looked in the
tanks, and it looked full, so I went home. I filed my IFR flight plan
that evening, so I could just get ready, and go out to the airport and
fly.

I did another visual check of the fuel as part of my preflight - yep,
still full.

So off I went, climbing to altitude, and got the engine leaned out
nicely. The weather had turned out to be much better than forecast, but
I still went IFR - after all, there was a high overcast and it was still
dark. My first leg was long enough that I'd have only an hour worth of
fuel on landing.

Passing over Waco, I cross-checked my time en route with the fuel
gauges. They showed a little LESS than expected; they had been
indicating F on departure. About 45 minutes on, they were showing
sufficiently less than I expected that I decided to land before
reaching my intended fuel stop. I told ATC I wanted to change
destinations, got the field in sight, canceled IFR and landed.

The FBO had just opened. They topped the plane off. When I did the
visual check, I noticed what I thought was full wasn't really full - now
it was truly full, I realised the fuel being an inch below the filler
neck was actually the best part of an hour's worth of fuel! Looking at
my fuel receipt, I calculated I'd have landed at my original intended
destination with only 15 minutes of fuel left. Any vectoring or holding
could have quite easily blown that. Had I ignored the fuel gauges as
being useless, that's what would have happened. After topping off, I
noticed the fuel gauges indicated slightly over the F mark instead of
being right on it - rather like my car really.

So my lesson is - keep track of time AND cross check time and your
expected fuel burn with the fuel gauges. If the gauges show less than
expected, land and check it out. They might well be right.

Of course we'll never know - but perhaps the fuel gauges on that Archer
that ended up in Lake Michigan were telling the pilot all along that he
was running out of fuel. Perhaps he hadn't leaned the mixture right,
perhaps he hadn't kept track of time and had a higher headwind than
expected and perhaps his flight plan said he'd make it with adequate
reserve. And perhaps the fuel gauges were telling him all along, but
he'd been admonished never to trust them, so never even thought to
include them in his normal cross-check.

--
Dylan Smith, Castletown, Isle of Man
Flying: http://www.dylansmith.net
Frontier Elite Universe: http://www.alioth.net
"Maintain thine airspeed, lest the ground come up and smite thee"

[[email protected]]

I have owned and flown a Cessna 182B for almost 27 years, and have
found that the
fuel gauges are pretty accurate in level flight (checked with a
dipstick after landing).
Like you say, the tanks will take quite a bit more when they look full.
Also, it is not
uncommon for the gauges to be hard against the pin (full) for an hour
after takeoff.

Be that as it may, I always start the stopwatch when I take off - and I
believe whichever
indication is the most pessimistic about fuel remaining (calculated
endurance or
gauges).

David Johnson

[nrp]

Fuel gages can also be made inaccurate by fuel tank deformation. The
Aeronca Sedan on floats I was flying 40 years ago had fuel cells, which
I didn't really understand the consequences of at the time. It also
had sight glass gages directly into the two wing tanks. After all,
what could be more accurate and reliable I thought.........

My cross country aerial adventure with my then new girl friend started
out by a magneto failure (stone dead) discovered at altitude on the
outbound trip. That got fixed by a local tractor magneto repair shop
(Yeah, he'd seen that mag used on old Allis Chalmers - but they were
considered quite troublesome). It needed a new coil for $3.00.

But the old bird also had leaky fuel caps and possibly a plugged fuel
vent system. At any rate on the return leg the fuel levels still
indicated nice and high while cruising along. The fuel cells were
collapsing, while those wonderful gages showed lots of fuel on board.
I'd swear that thing went from 1/2 tanks indicated to a complete engine
stoppage in 5 minutes. We deadstick landed in a swamp and drifted to
shore, up to a very surprised farmer's house to ask for fuel.

It was quite an adventure. I understand it is now an AD on Aeronca
15ACs.

[[email protected]]

As for peeking into the tanks and seeing what's there: we have
made calibrated dipsticks for every airplane we operate, with the zero
on the stick being the unusable-fuel level in the tanks as specified by
the POH, and full being FULL, which usually coincides with the tank
capacity given by the POH. These aircraft are used for training
commercial pilots who will be flying in Third-World
jungle/desert/mountain/sea operations, for outfits that demand an exact
fuel figure before every takeoff. Fuel mistakes in such environments
are usually fatal.
The calibrated stick isn't hard to make, but it surely is a pain
to get every drop out of the system, put the unusable fuel amount in
each tank, then add three or five gallons at a time to determine the
level for that amount. The airplane has to be fairly level, too,
without being rocked around by wind or moved while determining dipstick
calibrations.
The stick is handy for confirming accurate fuel flows after
landing from cross-countries and seeing what the real burn is at
various mixture settings. Cessna, for example, calculates their cruise
charts based on a pretty lean mixture, where few low-time pilots
operate.

Dan

[Peter R.]

> wrote:

> The stick is handy for confirming accurate fuel flows after
> landing from cross-countries and seeing what the real burn is at
> various mixture settings.

I used a dip tube extensively when I flew in a C172. This allowed me to
provide very specific refueling instructions for the lineman when weight
and balance required less than full tanks.

In the Bonanza I now fly, the wing tanks slope from the cap to the back of
the wing. Below about 26 gallons, I cannot see the fuel nor dip a stick to
determine fuel quantity. Thus, to be absolutely sure of fuel when it is
out of sight like this, I am forced to fill at a minimum to the bottom of
the tabs, or 30 gallons useable. I miss the certainty and flexibility
that the C172 tanks provided.


--
Peter


















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[Gene Seibel]

The only regulations for fuel gauges are that they read correctly at
empty. They are not reliable for determining the amount of fuel in the
tanks, but as they approach empty, they should be believed.
--
Gene Seibel
Hangar 131 - http://pad39a.com/gene/plane.html
Because I fly, I envy no one.

[Bob Moore]

"Gene Seibel" wrote

> The only regulations for fuel gauges are that they read correctly at
> empty. They are not reliable for determining the amount of fuel in the
> tanks, but as they approach empty, they should be believed.

Bull****! I am repeating an e-mail that I sent to a young man
who posted the same information on his web site.

Russ......

I stumbled on your web site while searching for some C-172 Fuel Cap
information.
I found the following statement which while completely false, seems to be
circulating quite widely.

"The FAA only requires the gauges to read accurately when the tanks are
empty. Yeah, you're right, that's really stupid, but it's the law."

I have quoted the applicable portion of the Federal Aviation Regulation
"law".

Section 23.1337: Powerplant instruments installation.
(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 under §23.959(a);

Paragraph (b) of course is the controlling portion and requires the
indicator to indicate the quantity of fuel at all times. Since no
tolerance is specified other than the indicator must be marked and
calibrated, it must be assumed that it must be calibrated accurately.

The intention of paragraph (1) is to require that the "zero" reading be
applied to "useable fuel" and not "total fuel". The C-172 that I fly
(1959 model) can be filled with a total of 42 gal. of fuel of which only
37 are useable. It obviously would not be acceptable to have the engine
quit from fuel starvation with 5 gal. showing the gages.

Paragraph (1) has nothing to do with gage "accuracy" but rather the
calibration of the system to indicate zero with zero useable fuel
remaining.

It might be wise to remove the erroneous "hangar talk" from your web
site.


Bob Moore
ATP CFII

[[email protected]]

Dan
Having operated for much of my 22,000 hours in remote areas and/or
hostile terrain where help was where you could find it, I made it a
point to take the time and trouble of making a calibrated stick for
each of my aircraft. I have run out of fuel a couple times in about 50
years of flying for various reasons. Fuel gages to me, are simply
indicators to assist in aircraft operations. They may or not be
accurate. In any case, when they indicate below 1/4 I get nervous and
watch my fuel burn vs time even more closely and in particular when I
am over hostile terrain.
I've experienced mechanical failures when either the gages went offline
as in an electrical failure, or I was losing fuel from a poor
connection or venting from a faulty drain. The end result was not
pleasant but no injuries to anything either. If you are not flying a
glider, you sure better know specific fuel burn for your operations and
aircraft lest you turn into a glider pilot of a lousy glider with a big
chunk of iron hanging on the nose!!
One hour of fuel remaining in the tanks at my destination usually gives
me that warm fuzzy feeling. Sometimes I never had that option or
capability. As a segue to that, GOOD navigation is a requisite skill so
you don't find yourself wondering where in hell you are or where you
are going?!
Cheers
Ol S&B

[Gene Seibel]

Thanks for the correction.
--
Gene Seibel
Gene & Sue's Aeroplanes - http://pad39a.com/gene/planes.html
Because we fly, we envy no one.

[Paul kgyy]

The cherokee series has a fairly prounounced wing dihedral. If the
airplane is parked on a non-level surface, it's possible for the lower
tank to appear full when in fact it can be a good half hour short of
full.

[[email protected]]

>In the Bonanza I now fly, the wing tanks slope from the cap to the
back of
>the wing. Below about 26 gallons, I cannot see the fuel nor dip a
stick to
>determine fuel quantity.

Guys flying 180s/185s have the same problem. They make a dipstick
that looks like a scimitar, a curved blade that has a tee on top to
rest on the tank neck and inserted so that the curved blade reaches
toward the back of the tank. (Got to be careful not to cut the rubber
bladder.) It will detect lower fuel levels than the eyeball can.

Dan

[Ed H]

"Dylan Smith" > wrote in message
...
>A couple of points with regard to running out of fuel:
>

Question for all: how accurate are fuel flow meters?

[john smith]

Ed H wrote:
> Question for all: how accurate are fuel flow meters?

The Cherokee Six I fly has an FS450.
It had been installed for over a year and never calibrated.
After a trip to AirVenture in 2001 with a fuel flow on the guage of 16
gph, imagine my surprise when the fuel truck upload calculated out to 12
gph!
A series of four flights over the next couple months resulted in
tweaking the calibration to where a three hour trip showed only a 0.6
gallon difference between actual fuel used and calculated fuel used.
I couldn't adjust it any better than that.

[Peter R.]

Ed H > wrote:

> "Dylan Smith" > wrote in message
> ...
>>A couple of points with regard to running out of fuel:
>>
>
> Question for all: how accurate are fuel flow meters?

I have a JPI EDM-800 engine monitor installed in my Bonanza and its fuel
flow meter is accurate to less than 1 gallon per three hour flight. The
JPI reads one gallon less than there really is in the tanks after a three
hour flight. The JPI also has a programmable alarm that will flash time
remaining when time reaches a preset limit. I set it to one hour
remaining., which is the upper limit of the alarm.

Regarding accuracy, there is a method for adjusting the k-factor in this
instrument that would allow me to get the fuel flow even more accurate, but
I have yet to do this.

Another nice feature of the JPI is that it feeds fuel flow and fuel
remaining data to the Garmin GNS430. This allows me to go to the Fuel
Planning page of the GPS to see an actual landing fuel, fuel to next
waypoint, fuel needed for remaining trip, and time remaining (endurance).

Of course, the GIGO factor applies here (garbage in, garbage out). The JPI
needs to be told how much fuel is on board. If the pilot fails to
initialize the instrument with the actual FOB, the fuel remaining and
endurance will obviously be incorrect.

--
Peter


















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[Peter R.]

> wrote:

> Guys flying 180s/185s have the same problem. They make a dipstick
> that looks like a scimitar, a curved blade that has a tee on top to
> rest on the tank neck and inserted so that the curved blade reaches
> toward the back of the tank.

I wonder if this is possible for the Bonanza's tanks?

--
Peter


















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[George Patterson]

Peter R. wrote:
>
> I wonder if this is possible for the Bonanza's tanks?

Why would you need this with tricycle gear?

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

[George Patterson]

Gene Seibel wrote:
> The only regulations for fuel gauges are that they read correctly at
> empty.

No, the regs also require that they indicate the quantity of fuel in the tank.
All the time.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

[Peter R.]

George Patterson > wrote:

>>
>> I wonder if this is possible for the Bonanza's tanks?
>
> Why would you need this with tricycle gear?

Sorry, George, your question has me confused. Are you asking why I would
like some method for verifying the amount of fuel in the tanks?

--
Peter


















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[George Patterson]

Peter R. wrote:
>
> Sorry, George, your question has me confused. Are you asking why I would
> like some method for verifying the amount of fuel in the tanks?

No, I just find it amazing that the slope of the tanks could be severe enough on
a trike to require a stick like those used on tailwheel aircraft. Hence, the
question.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

[Peter R.]

George Patterson > wrote:

> No, I just find it amazing that the slope of the tanks could be severe enough on
> a trike to require a stick like those used on tailwheel aircraft. Hence, the
> question.

I am not exactly sure what shape the Bonanza's fuel tanks are, but looking
inside I see a shallow slope to the trailing edge. This only permits 26
gallons or more of fuel to be seen.

It would be much more comforting to have a method for verifying exactly how
many gallons of fuel are in each tank. Hence my question.


--
Peter


















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[Morgans]

"George Patterson" > wrote
>
> No, I just find it amazing that the slope of the tanks could be severe
enough on
> a trike to require a stick like those used on tailwheel aircraft. Hence,
the
> question.

The slope of the tank due to dihedral (sp?) is the problem, if the cap is at
a point furthest out from the wing, and the tank is long. (chordwise)

The same principle, only in reverse, would hold for a gauge sending unit in
the lower end of the tank. It would read completely full, until the top
burns off of the tank, but it would tell how low your gas level is, in
spades.

That is the beauty of Jim's capacitance sending unit, because you can
install it lengthwise, from the bottom inboard to the top outboard at the
cap. It will start going down when the first fuel is used, and still be
going down, right up until the fan stops turning.
--
Jim in NC

[Peter Duniho]

"Ed H" > wrote in message
. ..
> Question for all: how accurate are fuel flow meters?

I have a very simple one, shows only current fuel flow, and total fuel used
since the last reset. I don't even recall what brand it is.

My experience with it is much more like Peter R.'s than John Smith's. It's
extremely accurate, and consistently predicts how much fuel will be required
to top off the tanks to less than a gallon (to within 0.5 gallon is
typical).

Pete

[[email protected]]

Pete et al
With all due respect for the modern electronics and advancements, I
guess I am just one of the soon to be gone dinosaurs and have seen all
too many occasions when the modern technology takes a vacation when you
need it most. Reliance on anything electrical with little regard for
anything else in the way of aviation aids is, to my mind, just another
example of an unexplained NTSB report in the making.
I flew for many years in remote areas without anything but common sense
and the teachings of an old CFI who was very demanding and required
that I knew our exact location at any given time, and give him the
number of gallons we'd take on at refueling. I smile to think of how
easy it would have been if we'd had GPS for an aid. We didn't even have
ADF in many regions and in many cases no accurate charts.
Lovely to have the modern technology working, but it will never replace
the human brain. The human brain is useless unless it has the proper
knowledge to work with.
My point is to not rely solely on electrical components/indications.
Fly safe
Ol S&B

[Paul kgyy]

My JPI is always within a gallon when I top up.

[Gene Seibel]

My mistake. Thanks for pointing it out.
--
Gene Seibel
Hangar 131 - http://pad39a.com/gene/plane.html
Because I fly, I envy no one.

[John Galban]

Dylan Smith wrote:
<snip>
> So my lesson is - keep track of time AND cross check time and your
> expected fuel burn with the fuel gauges. If the gauges show less than
> expected, land and check it out. They might well be right.
>

That's the key to using the often less-than-accurate fuel gauges
found on most aircraft. Even though they may not tell you the exact
quantity of fuel in each tank, an unusual reading can tip you off to a
fuel leak or higher than expected fuel burn.

One more trick that I keep in the bag is to burn fuel from one tank
at a time (even when flying a high wing that allows both). If you
have a leak or unusually high fuel burn, you'll be alerted when a tank
goes dry ahead of schedule. At that point, you (hopefully) have fuel
remaining in the other tank to get you safely on the ground. When
flying on a "both" setting, by the time you realize that something is
wrong, you may have emptied both tanks.

John Galban=====>N4BQ (PA28-180)

[Peter R.]

S&B wrote:

> My point is to not rely solely on electrical components/indications

I agree. This is why I always take along a cross country flight log
with blocks at each waypoint for estimated time of arrival and actual
time of arrival. En route, I use this log and a clock to monitor fuel
usage.

OK, so the XC log is produced by Jepp's FlightStar flight planning
software, but I could produce one by hand if I had to. :)

--
Peter

[Peter Duniho]

> wrote in message
oups.com...
> [...]
> My point is to not rely solely on electrical components/indications.

Who said anything about making the fuel flow meter one's sole source of
information with respect to fuel quantity?

Geez...take a chill pill. The correct "takeaway" here is that a) fuel flow
meters ARE useful (when properly calibrated) and b) you cannot trust any one
source of information (not even your watch) and so the more sources of
information you have available, the better (so you can cross-reference).

It's got nothing to do with being "one of the soon to be gone dinosaurs".
Other than a dinosaur who refuses to take advantage of new technology *in
addition to* their existing tools may be gone sooner rather than later, that
is.

Pete

[[email protected]]

Pete
You misread or misunderstand me. I said not to rely SOLELY on
electrical. I'm delighted to see the modern advances and electronics
and use them as often as they are available. But, I've been around a
long time and have yet to see a foolproof system. I've encountered more
than a few in-flight failures of nearly everything that can go wrong!
Fortunately I was close enough to make a landing when I had some
serious failures in flight.
BTW, what is a "takeaway"? Is that a new word that us old english major
dinosaurs have to learn? Of course I understand the meaning or intent,
I think, but have never seen it used before.
geeezzzo....chill pill?
fly safe and don't take anything for granted
Ol S&B

[JOM]

Before you get too excited about FAR part 23, remember most of the planes we fly were certified under CAR 3, and don't have to conform to part 23 regarding fuel gauges. Only newer aircraft certified under part 23 have to conform to this regulation.

That's not to say that it isn't a very good idea to get your gauges calibrated and make them as accurate as possible. And if your fuel gauge says empty, then land ASAP and figure out the problem.

John


[QUOTE=Bob Moore;269828]"Gene Seibel" wrote

The only regulations for fuel gauges are that they read correctly at
empty. They are not reliable for determining the amount of fuel in the
tanks, but as they approach empty, they should be believed.

Bull****! I am repeating an e-mail that I sent to a young man
who posted the same information on his web site.

Russ......

I stumbled on your web site while searching for some C-172 Fuel Cap
information.
I found the following statement which while completely false, seems to be
circulating quite widely.

"The FAA only requires the gauges to read accurately when the tanks are
empty. Yeah, you're right, that's really stupid, but it's the law."

I have quoted the applicable portion of the Federal Aviation Regulation
"law".

Section 23.1337: Powerplant instruments installation.
(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 under §23.959(a.......