Running dry?

As a student, I would like to interject here with a couple of comments
and questions...

1. I have learned from this discussion that everyone has an opinion,
and their opinion is quite strongly held. Does anyone have any data,
on either side, to back up their opinion? How often do planes have
trouble caused by not knowing precisely how much gas they have,
perhaps influenced by inaccurate gages? How often do planes have
trouble caused by running a tank dry (NOT running the _last_ tank
dry)?

2. There seems to be a lot of discussion mentioning that the only way
to be sure of your tank's capacity is to run it dry. In my reading
about flying, I notice that folks talk about measuring fuel by looking
in the tanks and perhaps using a dipstick. Couldn't you calibrate
your gages by filling the tanks, going for a flight, then sticking a
ruler into the tank to see how much is left? Is running the tank dry
any more accurate or useful?


To me, the two sides of this debate seems to be as follows: some folks
want to be in control of every aspect of their flight, while other
folks want to have as wide of a saftey margin as possible at all
times. The fuel tank issue is one where these two goals conflict.

To the control oriented folks, having a tank run dry when they expect
it gives them one more data point which makes them more comfortable
and feel more in control during the flight. Any small change in
flight characteristics is detectable by a change in tank switch
timings, and so these folks are willing to accept what they think is a
small risk in changing tanks in order to detect any problems.

The safety margin folks feel more comfortable not knowing precisely
how much margin of safety they have, as long as that margin is wide
enough that they never have to worry about it. To these folks minor
problems will be covered by their ample margin of safety, and major
problems will become apparent on their gages. These folks want to
make sure they have as much fuel as possible in reserve in all tanks
when the major problem hits, and don't worry about missing a couple of
minor problems as a result.

Is my characterization accurate?

Chris
--
Chris Colohan Email: PGP: finger
Web: www.colohan.com Phone: (412)268-4751

"Chris Colohan" wrote in message
.. .
As a student, I would like to interject here with a couple of comments
and questions...

1. I have learned from this discussion that everyone has an opinion,
and their opinion is quite strongly held. Does anyone have any data,
on either side, to back up their opinion? How often do planes have
trouble caused by not knowing precisely how much gas they have,
perhaps influenced by inaccurate gages? How often do planes have
trouble caused by running a tank dry (NOT running the _last_ tank
dry)?

http://www.avweb.com/news/columns/182044-1.html

http://www.aopa.org/asf/publications...ndex.html#fuel

(The most common excuses are along the lines of "I though it was full when I
took of, so I didn't check it").
http://www.aopa.org/asf/publications/sa16.pdf

2. There seems to be a lot of discussion mentioning that the only way
to be sure of your tank's capacity is to run it dry. In my reading
about flying, I notice that folks talk about measuring fuel by looking
in the tanks and perhaps using a dipstick. Couldn't you calibrate
your gages by filling the tanks, going for a flight, then sticking a
ruler into the tank to see how much is left? Is running the tank dry
any more accurate or useful?

Better to run ONE dry, land, and fill it to the rim and read the numbers on
the fuel truck.

NEVER run it dry when it is unintentional. Also, never run it dry
intentionally when you don't know within a few minutes of WHEN it's going to
cut out AND ARE WATCHING FOR IT TO CUT OUT.

To me, the two sides of this debate seems to be as follows: some folks
want to be in control of every aspect of their flight, while other
folks want to have as wide of a saftey margin as possible at all
times. The fuel tank issue is one where these two goals conflict.

See the AvWeb article at the URL above.

To the control oriented folks, having a tank run dry when they expect
it gives them one more data point which makes them more comfortable
and feel more in control during the flight. Any small change in
flight characteristics is detectable by a change in tank switch
timings, and so these folks are willing to accept what they think is a
small risk in changing tanks in order to detect any problems.

The safety margin folks feel more comfortable not knowing precisely
how much margin of safety they have, as long as that margin is wide
enough that they never have to worry about it. To these folks minor
problems will be covered by their ample margin of safety, and major
problems will become apparent on their gages. These folks want to
make sure they have as much fuel as possible in reserve in all tanks
when the major problem hits, and don't worry about missing a couple of
minor problems as a result.

One problem with fuel planning is when things don't shape up as expected
(headwinds, holds due to weather...), but how do you plan alternative
actions if your only know, in a fuzzy fashion, how much fuel you have. Yeah,
it's always better to play it safe, land, and take on both airplane and
people fuel...but when if that alternative is not immediately available.

Fly over the Colorado Rockies sometime during widespread, low weather and
your nearest fual can be esaily a half an hour away or more.


Is my characterization accurate?

Pretty much.

As a student, I would like to interject here with a couple of comments
and questions...
[...] How often do planes have
trouble caused by running a tank dry (NOT running the _last_ tank
dry)?

I would make this two parts - one for =deliberately= running a tank
(not the last tank) dry, and the other for =accidentally= doing the same.

Jose
--
Quantum Mechanics is like this: God =does= play dice with the universe,
except there's no God, and there's no dice. And maybe there's no universe.
for Email, make the obvious change in the address.

Chris Colohan wrote:
2. Couldn't you calibrate
your gages by filling the tanks, going for a flight, then sticking a
ruler into the tank to see how much is left? Is running the tank dry
any more accurate or useful?

If only it were that simple!
Fuel tanks are of various shapes and sizes.
Linear measurements apply only to tanks with flat sides, tops and bottoms.
I can tell you that on some airplanes, if you look in the filler neck
and see it within an inch of the top, you can still get 10 or more
gallons into it.

"john smith" wrote in message
.. .
Chris Colohan wrote:
2. Couldn't you calibrate
your gages by filling the tanks, going for a flight, then sticking a
ruler into the tank to see how much is left? Is running the tank dry
any more accurate or useful?

If only it were that simple!
Fuel tanks are of various shapes and sizes.
Linear measurements apply only to tanks with flat sides, tops and bottoms.
I can tell you that on some airplanes, if you look in the filler neck
and see it within an inch of the top, you can still get 10 or more
gallons into it.

It also depends on how the plane is parked. A couple of degrees left or
right, nose up or down can make a huge difference. That fact also plays
havoc with the fancy fuel measuring do dads. Just like navigation, never
rely on a single method of fuel management.

john smith wrote:


I can tell you that on some airplanes, if you look in the filler neck
and see it within an inch of the top, you can still get 10 or more
gallons into it.

And in others, if it's within an inch of the top, fuel is already running out
the vent tubes.

George Patterson
Give a person a fish and you feed him for a day; teach a person to
use the Internet and he won't bother you for weeks.

John,

Fuel tanks are of various shapes and sizes.


which may even change, e.g. when a fuel bladder collapses partially.

--
Thomas Borchert (EDDH)

1. I have learned from this discussion that everyone has an opinion,
and their opinion is quite strongly held. Does anyone have any data,
on either side, to back up their opinion? How often do planes have
trouble caused by not knowing precisely how much gas they have,
perhaps influenced by inaccurate gages? How often do planes have
trouble caused by running a tank dry (NOT running the _last_ tank
dry)?

I don't know if there's a way to adequately answer your question, as no
records (to my knowledge) are kept of this kind of thing.

The one record we all know, however, is the appallingly high number of
"accidents" that happen each year because of planes running out of gas.
This is a statistic that should be easily improved, yet, year after year,
the numbers stay stubbornly high.

Why? Carelessness and stupidity. There simply IS no other reason for
running out of gas. (Short of a fuel leak, of course.)

My wife and I are both pilots. We have both had it pounded into our heads
(by instructors, FAA seminars, and magazine articles) that it is the
ultimate display of ignorance to ever run out of fuel. Thus, our *very*
conservative fuel management system has evolved over the last decade, and it
has served us well.

In the end, we may ultimately succumb to some sort of an aviation mishap --
but I can almost guarantee that it will *not* be due to fuel exhaustion.

2. There seems to be a lot of discussion mentioning that the only way
to be sure of your tank's capacity is to run it dry. In my reading
about flying, I notice that folks talk about measuring fuel by looking
in the tanks and perhaps using a dipstick. Couldn't you calibrate
your gages by filling the tanks, going for a flight, then sticking a
ruler into the tank to see how much is left? Is running the tank dry
any more accurate or useful?

The bottom line is that with a dipstick (or, in our plane, with the gauges)
you will be accurate to within a gallon -- maybe two. The truth is, if this
amount of gas is the difference between a safe arrival, and an off-field
landing, you have made a VERY dumb mistake in your fuel management.

In short, if you need it more accurate than *that*, you are pushing your
range too close to the razor's edge.

Is my characterization accurate?

Quite.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

"Jay Honeck" wrote in message
news:yWwOe.299648$xm3.128272@attbi_s21...
I don't know if there's a way to adequately answer your question, as no
records (to my knowledge) are kept of this kind of thing.

The one record we all know, however, is the appallingly high number of
"accidents" that happen each year because of planes running out of gas.
This is a statistic that should be easily improved, yet, year after year,
the numbers stay stubbornly high.

Are the large numbers due to fuel exhaustion or fuel mismanagement. Seems I
remember a lot of engine out accidents are fuel mismanagement and not
exhaustion.

On 2005-08-22, Jay Honeck wrote:
1. Refuel after every flight. You will be ready to go for your next flight,
and can rest assured that you have gas on board. (Renters will have to
switch this to refueling BEFORE every flight.)

Again, this is not a hard and fast rule. It is NOT stupidity to NOT do
this, and often it's necessary. Indeed, airlines routinely fly without
full tanks.

I'm making an assumption here - by refuelling, you mean top the tanks. I
apologise if this isn't what you really mean, but let's assume that you
(or the generic 'you') do mean that. It probably works well for you with
your aircraft and your typical mission. But consider this.

I did my multi training in a Piper Apache (Geronimo conversion) which
carried rather a lot of fuel. Seven hours of fuel in fact. 7 hours of
fuel weighs quite a bit, even at the fuel burn of a Piper Apache. The
plane has 5 seats. I need to be able to trade off fuel for payload in
case a bunch of us are going somewhere. 7 hours of fuel and 5 filled
seats = way over gross, which in a Piper Apache means you are not going
anywhere other than down should one of the donkeys decides to take the
day off. To fly with half fuel to go to an airport an hour away is
NOT bad decision making - it is called trading off range for payload,
and as I said, it's common practise with the airlines.

Really, the same goes for taking 4 people in a Cessna 172 or a Warrior -
you're going to have to trade off fuel for payload. I don't consider it
"stupid" to carry only 2.5 hours of fuel to take three friends on a 30
minute sightseeing trip around the local area.

About 2 weeks ago, I was flying with my friend Paul in his Cessna 180.
We were departing from an 860 foot long back country airstrip with a
field elevation of 4200 feet. If the airfield sold fuel (it doesn't), it
would have been foolish in the extreme to top the tanks before departing
this airfield. (Of course, some people may argue it's foolish in the
extreme to use that airstrip at all, but IMHO the rewards exceeded the
risks).

My old Cessna 140. I've flown it up in the mountains. Flying with half
fuel was a given. With 85 horsepower you need all the help you can get
at high elevations.

Towing the gliders at Andreas. Taking a full tank of fuel in the Auster
simply prolongs the climb and means you have to run the engine at full
power (where it gets hot because the installation doesn't exactly have
the best cooling in the world). Much better to avoid flying with more
than half tanks.

If your normal mission and your aircraft allows it, by all means top off
after every flight. However, it is not stupid or wrong NOT to top off
after every flight - especially if you don't know what your next flight
will be and you fly a plane where you can usefully trade range for
something else (rate of climb or non-fuel payload). The main thing is to
use your brain when deciding how much fuel to carry.

4. Measure your gas with your watch, never your fuel gauges.

No. Measure your gas with your watch AND KEEP THE FUEL GAUGES IN YOUR
CROSS CHECK. If the fuel gauges indicate less fuel than you expect to
have at the given stage of the flight, land and check it out. Do NOT
ignore your fuel gauges. If you own the plane, it behooves you to make
sure your fuel gauges are at least useful enough so that you can detect
the situation where you have less fuel than you calculated. If you rent,
get to know the planes you fly and know how useful the fuel gauges are
for cross-checking.

Working fuel gauges provide a useful cross check. In most things in
aviation - you should avoid relying on a single source of data and at
least have a cross check. For your watch and fuel calculations, cross
check with the gauges. For your GPS, cross check by using VOR and
pilotage. There's lots of emphasis on cross checks when flying IFR. It's
not just IFR that benefits from cross checking - pretty much anything is
less likely to land you with an unpleasant surprise if you can perform a
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"