Running dry?

In article ,
Greg Copeland wrote:

In September 2004 issue of AOPA Flight Training, Mark Cook has an article,
"No Fueln' Around". Under the "Selector boy" side article, he mentions
that he runs some of his tanks dry in his Bellanca Viking. In at least
one of John Deakin's articles
(http://www.avweb.com/news/columns/182044-1.html), he not only recommends
running tanks dry but puts forth a powerful argument that it's a
responsible fuel management strategy. Furthermore, Deakin also offers
that he has never found an NTSB accident report related to a failed engine
start when running a tank dry and switching to the next. Both guys
recommend setting a timer a couple of minutes before the tank should run
dry; which acts of both early warning and as validation of your
anticipated fuel consumption.

Is this common? How many run their tank(s) dry as part of their fuel
management strategy? If you don't run dry, why not? Aside from the heat
beat skipping which is sure to follow the first couple of times, what's
the down side to this strategy?

I was taught to run aux tanks dry, as a matter of fuel management. This
technique is best on carbureted engines, as restart is just about
instantaneous, as soon as th float bowl fills. On fuel-injected engines,
it takes a few seconds (which seems like hours) to get fuel to the
engine and back running.

The philosophy is that it is best to end a flight with all of yoy=ur
available fuel in a single tank, to prevent starvation at critical
times. On the old, pressure-carburetor Bonanzas, the fuel return fed
back to the left main tank only (about 2-3 gph). The procedure was to
run that tank dry, switch to the aux tank(s), run dry, switch to right
main an run it dry. You are left with an hour's worth of fuel in the
left main and no longer have to switch tanks for the duration of the
flight.

You can catch the "tank dry" point by monitoring the fuel pressure gage
and switch as soon as you see it flicker.

I'm familiar with the article, and somewhat in agreement. Running a
tank dry intentionally and at a safe altitude can be a responsible fuel
management strategy, uninformed comments to the contrary
notwithstanding.

Some factors favor running a tank dry. These factors are normally
aspirated engines (start right up when fuel is restored - an injected
engine can vapor-lock) and a gravity-feed fuel system (once again - no
risk of vapor lock). In a plane with a carbureted engine and a gravity
feed system, I would not hesitate to run tanks dry routinely. In a
plane with an engine driven suction pump and injected engines, I would
need a good reason - yes, the engine WILL restart - but it could take
forever (well, OK, 30-60 seconds) before the surging stops and full
available power is restored.

So what is a good reason to run a tank dry intentionally? Paradoxical
as it may sound, one good reason is to prevent running one dry
unintentionally - like the guy who ran his dry on the approach. It's
certainly more of an issue in IFR flying than it is in VFR flying,
because you're often not in a position where you can land safely on 15
mintues notice, and thus you NEED your reserves.

So how does one run a tank dry unintentionally? One method I often see
taught for fuel management that drives me absolutely bat**** is the
30-minute switch. Two tanks, run 30 minutes off each one. Works great
if you never use anything close to the full range of the airplane (in
which case ANYTHING works) or if you have the fuel consumption nailed.
If not, you're setting yourself up to run a tank dry - and what happens
when you do? Now you have less than 30 minutes left in the other tank!
Under VFR, that will probably be enough to make the nearest airport.
Under IFR, it may not be enough to reach an airport with a suitable
approach.

If flying something carbureted with a gravity feed system, I will
routinely run tanks dry in cruise just to have all my reserve fuel in
one tank. That way, if the worst happens (someone gears up on the only
runway and closes the airport, or the airport and my alternated go
below mins unexpectedly) I have all my reserve fuel in one place AND I
know exactly how much I have so I know what kind of plan I can make.
The advantage I gain may be slim (an extra 20 miles of range) but the
cost is essentially nil.

If flying something with a suction pump system and fuel injection, I
won't intentionally run a tank dry - but I will calculate exactly how
long I expect the tank to last and run it exactly that long - NOT LESS.
If I run out sooner than expected, that tells me my fuel consumption
is high, or I was misfueled (maybe due to fueling on a slope - can't
always avoid it) and thus I derate the amount of time I should have
available on the tank(s) I didn't run dry - and maybe change my
destination.

As a general rule, I would say you should always manage your fuel burn
such that if a tank unexpectedly runs dry due to misfueling or
higher-than-expected consumption, you should always have enough in
another tank to make a safe landing. Switching tanks in 30 minute
intervals does not do that.

Michael

I don't recommend doing engine outs by
pulling the mixture knob either. But people do it and usually get away
with it.

Actually, on carbureted engines the mixture cut is the safe way to do
it, and it's the people who use the throttle who are taking a risk -
the very real risk of fouling plugs and building carb ice (carb heat
may not be terribly effective at idle power) rather than some
mysterious and unexplained risk of the engine not starting again.

On injected engines, it's not so simple - there vapor lock is a real
issue so the correct procedure is a throttle cut - but one must pay
VERY careful attention to keeping the mixture VERY lean, lest plugs
foul and full power is not availabe just when you need it most.

Michael

Michael wrote:
As a general rule, I would say you should always manage your fuel burn
such that if a tank unexpectedly runs dry due to misfueling or
higher-than-expected consumption, you should always have enough in
another tank to make a safe landing. Switching tanks in 30 minute
intervals does not do that.


If you extend that to every hour, be prepared to carry one wing for a while due
to weight imbalance. It's not dangerous; just an annoyance.



--
Mortimer Schnerd, RN

VE

On my Super Viking I routinely ran the Aux tanks dry... I ran a timer
so I knew within a few minutes when it would happen... The engine would
begin to lose power and I would switch tanks and hit the boost pump...
Usually did not get an engine stoppage... If I was a bit slow on the
switch the engine might stop running but relight within a few seconds
of the tank change.. On my Apache I run the tank(s) dry about once a
year to clean them out (and I usually stick a mirror in them before
refilling)...
Now, running a tank dry and running out of fuel are two different
critters... I do not allow the fuel on the Apache to go below 1 hour (6
hours total capacity) for any reason...

denny

The philosophy is that it is best to end a flight with all of yoy=ur
available fuel in a single tank, to prevent starvation at critical
times. On the old, pressure-carburetor Bonanzas, the fuel return fed
back to the left main tank only (about 2-3 gph). The procedure was to
run that tank dry, switch to the aux tank(s), run dry, switch to right
main an run it dry. You are left with an hour's worth of fuel in the
left main and no longer have to switch tanks for the duration of the
flight.

Unless the fuel return didn't function properly (can you preflight it?),
in which case you have zip.

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.

Recently, Greg Copeland posted:

Is this common? How many run their tank(s) dry as part of their fuel
management strategy? If you don't run dry, why not?

Two main reasons; there are better ways to gauge your fuel consumption
rate, for example, logging how much fuel you put back in the tank after
the flight; and why play with the trim to keep the plane going in a
straight line, then start all over again with that fiddling when you
switch tanks?

Aside from the
heat beat skipping which is sure to follow the first couple of times,
what's the down side to this strategy?

Besides being pointless? How about being uneccesarily risky?

Neil

On Thu, 18 Aug 2005 17:21:16 +0000, Neil Gould wrote:

Recently, Greg Copeland posted:

Is this common? How many run their tank(s) dry as part of their fuel
management strategy? If you don't run dry, why not?

Two main reasons; there are better ways to gauge your fuel consumption
rate, for example, logging how much fuel you put back in the tank after
the flight; and why play with the trim to keep the plane going in a
straight line, then start all over again with that fiddling when you
switch tanks?

Aside from the
heat beat skipping which is sure to follow the first couple of times,
what's the down side to this strategy?

Besides being pointless? How about being uneccesarily risky?


"I know of no accidents that have occurred because an engine would not
restart when supplied with fuel in flight. I have personally done this
literally thousands of times myself, and never seen more than a couple of
seconds of interruption, even when I was completely unaware the engine was
about to quit. If we count all the people I know who routinely did it,
there are literally millions of such events." -John Deakin

"This is simply not true of recips. When a recip runs out of fuel, nothing
else has changed. The spark is still there on every power stroke, the
piston is still pumping air, driven by the prop, which is nearly
impossible to stop, inflight even when you want to. Two of the "three
necessities" (fuel, air, spark) remain, totally unaffected by the lack of
fuel." -John Deakin

So what risk factor can you assign to what is more or less, a non-event?

As for the "why", John Says, "I'd like to take a look at fuel management,
and since my method sometimes calls for running a tank dry, let's get that
out of the way first." In other words, its his strategy for fuel
management which lets him known and understand how much he really has in
reserve and how much can he get out of the "unuseable". Should he have an
event where he has to bite into his reserves, he never has to say, "I sure
hope I have enough. I wonder how much is there".

This is not to say that I've bought into it, but hey, someone has to play
Devil's Advocate!

Greg

Mortimer Schnerd, RN wrote:
If I were trying to stretch a flight and even then only if I were alone, I might
consider running one dry. But I have to tell you: running a tank dry in a
Cherokee results in te longest 30 seconds of your life.

Four tank Pipers (PA28-235, PA32-300 series) manuals specifically state
that up to 10 seconds is required for fuel to refill the system after
running an outboard tank dry.

1972 PA32-300 POH, page 4-1, Emergency Procedures, Engine Powere Loss
During Takeoff and page 4-2, Engine Powere Loss in Flight
and
1979 PA32-300 POH, page 3-7, Emergency Procedures, Section 3.9, Engine
Powere Loss During Takeoff and page 3-8,Section 3.11, Engine Powere Loss
in Flight

"NOTE: If an engine failure was caused by fuel exhaustion, power will
not be regained after tanks are switched until empty fuel lines are
filled, which may require up to ten seconds."

In rec.aviation.piloting James Ricks wrote:

I'd like to know exactly how much fuel is useable, too, but think I'd probably
run a tank low, pump out the remaining gas, then either high idle or taxi
around until it sputtered, switch over, then fill the empty tank. Seems waaay
too much hassle to not just believe the manufacturer. If you choose to do this
when flying, please don't have either me or your insurance agent as a
passenger.

I routinely run tanks dry on long flights. As I know my plane and know
when a tank is about to empty, chances are that you, my insurance agent,
or my somewhat nervous wife or children ever notice that a tank went dry.

My first warning is a tank is about to dry is that my timer runs out.
A few minutes later I see a slight increase in my EGT (I've a good engine
monitor). About 40 seconds later, my fuel pressure gauge twitches. I
then switch tanks and the engine hasn't even burbled. Nobody notices.

BTW, Beech sez I've got 20 gallon tanks, with 17.5 usable. After running
my right tank dry, I can put fill with 20.8 gallons. My aux tank tank is
20 with 19 usable according to the book. After running it dry, I can put
19.7 in it. I don't know how much I can put in my left one as I only have
three tanks and I try hard not to have all three of them empty at one time
;-)

Fortunately, what Beech put in my owners book were written by engineers
with an engineers fudge factor. The books on later models were written by
lawyers using the engineers data (with the afore mentioned fudge factor).
Way lotta slop there.

In my day job, I operate a 2005 vehicle, and see the gunk that comes out of
fuel filters regularly. I can hardly imagine what could lurk in the +/- 30
year old tanks on aircraft we trust to keep us out of the trees.

Does your 2005 vehicle have sumps that you drain every time before you
start it?

--
Frank Stutzman
Bonanza N494B "Hula Girl"
Hood River, OR