How safe is it, really?

"Happy Dog" wrote:
ALWAYS refuel after every flight, so that we always have full
tanks.

I don't know why more pilots don't do this.

I don't know what you are flying, but with the planes I fly, full
tanks aren't an option unless I want to fly alone.

It should be obvious that I wasn't suggesting that anyone overload
their aircraft.

No, but you were wondering why more pilots don't "ALWAYS refuel after
every flight, so that [they] always have full tanks," which is a silly
practice unless one ALWAYS knows the next flight will require full
tanks. At my old club, members were asked NOT to fill the tanks after
using the airplanes, so that the next pilot could add fuel appropriate
to his flight.
--
Dan
C172RG at BFM

On Sun, 5 Dec 2004 06:42:51 -0600, "Dan Luke"
wrote in
::

... so that [they] always have full tanks," which is a silly
practice unless one ALWAYS knows the next flight will require full
tanks.

The practice of topping the fuel tanks after each flight rests on the
notion that air contains a certain amount of moisture, and that the
water will condense out of the air contained in partially emptied
tanks and contaminate the aircraft's fuel system.

On Sat, 4 Dec 2004 20:03:56 -0800, Brian Burger
wrote in c.ca::

On Fri, 3 Dec 2004, Matt Barrow wrote:

"Aviation in itself is not inherently dangerous. But to an even greater
degree than the sea, it is terribly unforgiving of any carelessness,
incapacity, or neglect." -- Unknown

"Captain A. G. Lamplugh, British Aviation Insurance Group, London. Circa
early 1930's..." (http://www.skygod.com/quotes/safety.html - 2nd quote
from the top)

Thank you very much for that link. The quotations there are
remarkable for their original insights and aptly articulated truths.
David English's choice of which to include adds immeasurably the
content. Bravo!

"Larry Dighera" wrote in message
...
On Sun, 5 Dec 2004 06:42:51 -0600, "Dan Luke"
wrote in
::

... so that [they] always have full tanks," which is a silly
practice unless one ALWAYS knows the next flight will require full
tanks.

The practice of topping the fuel tanks after each flight rests on the
notion that air contains a certain amount of moisture, and that the
water will condense out of the air contained in partially emptied
tanks and contaminate the aircraft's fuel system.

Which is an old wives tale. The amount of water contained in 20-30
gallons of air is insignificant.
--
Dan
C172RG at BFM

On Sun, 5 Dec 2004 07:40:00 -0600, "Dan Luke"
wrote in
::


"Larry Dighera" wrote in message
.. .
On Sun, 5 Dec 2004 06:42:51 -0600, "Dan Luke"
wrote in
::

... so that [they] always have full tanks," which is a silly
practice unless one ALWAYS knows the next flight will require full
tanks.

The practice of topping the fuel tanks after each flight rests on the
notion that air contains a certain amount of moisture, and that the
water will condense out of the air contained in partially emptied
tanks and contaminate the aircraft's fuel system.

Which is an old wives tale. The amount of water contained in 20-30
gallons of air is insignificant.

A Piper PA28-235 can have 84 gallons of fuel in 4 tanks, so leaving
them half empty, for instance in a humid maritime environment,
overnight where the temperature drops sufficiently to cause the
moisture to condense out of the 40 gallons of air contained in them,
will result in enough water in the fuel system to interfere with
operation of the aircraft's power plant.

However, PA28-235 can carry its empty weight (~1,400 lbs) in useful
load, so weight management through fuel offloading is seldom
necessary.

Personally, I prefer that water never be present in the aircraft fuel
system, especially in aircraft with fuel tank bladders....

Larry Dighera wrote:

A Piper PA28-235 can have 84 gallons of fuel in 4 tanks, so leaving
them half empty, for instance in a humid maritime environment,
overnight where the temperature drops sufficiently to cause the
moisture to condense out of the 40 gallons of air contained in them,
will result in enough water in the fuel system to interfere with
operation of the aircraft's power plant.

At 40 degrees Celsius, 1 cubic meter of saturated air contains roughly
40 grams of water. (I leave it to you to convert this to US units.)
Hardly significant.

Stefan

A Piper PA28-235 can have 84 gallons of fuel in 4 tanks, so leaving
them half empty, for instance in a humid maritime environment,
overnight where the temperature drops sufficiently to cause the
moisture to condense out of the 40 gallons of air contained in them,
will result in enough water in the fuel system to interfere with
operation of the aircraft's power plant.

At 40 degrees Celsius, 1 cubic meter of saturated air contains roughly
40 grams

That's about one and a third ounces. Remember, if all of the water comes out
of the air, it settles to the bottom, and is either drained or used by the
engine. It would take a lot of such cycles before enough water would be in the
tank to matter. As someone else already said, full tanks to prevent dangerous
condensation is another aviation myth.

On Sun, 05 Dec 2004 15:29:44 +0100, Stefan
wrote in ::

Larry Dighera wrote:

A Piper PA28-235 can have 84 gallons of fuel in 4 tanks, so leaving
them half empty, for instance in a humid maritime environment,
overnight where the temperature drops sufficiently to cause the
moisture to condense out of the 40 gallons of air contained in them,
will result in enough water in the fuel system to interfere with
operation of the aircraft's power plant.

At 40 degrees Celsius, 1 cubic meter of saturated air contains roughly
40 grams of water. (I leave it to you to convert this to US units.)
Hardly significant.

While the amount of water in the fuel system may be small, so is the
diameter of the fuel lines. In the cool environs at altitude, what is
to prevent the water from forming a frozen 'cork' blocking fuel flow?

Aircraft with fuel bladders that have become deformed or otherwise
lack a smooth bottom surface are capable of trapping significant
amounts of water and preventing it from reaching the fuel sumps for
removal without tipping the wings and other effort. The later model
Cessna 172s now have 10 wing drains as a result.

I submit, that water in an aircraft fuel system has the potential for
disaster. To argue otherwise seems absurd.

On 05 Dec 2004 15:35:02 GMT, emove (AJW) wrote
in ::

Remember, if all of the water comes out of the air, it settles to the bottom,

Even if only some of the water condenses out, that happens.

and is either drained or used by the engine.

If the water is trapped by an irregular surface at the bottom of the
fuel tank thus preventing it from reaching the sump, it will not be
drained; it will be retained within the tank.

It would take a lot of such cycles before enough water would be in the
tank to matter.

While the engine may be able to continue running after ingesting some
water, with an ambient temperature low enough, it wouldn't get fuel if
water in the fuel lines froze. What volume of water is enough to
cause such a frozen plug?

Larry Dighera wrote:

I submit, that water in an aircraft fuel system has the potential for
disaster. To argue otherwise seems absurd.

Nobody argues otherwise. But claiming that condensation caused by
halfways empty tanks is a noteworthy source for that water is equally
absurd. If there is water in your tanks, chances are you buyed it at
fuel price. Another important source is a leaking seal while the plane
is parked in the rain.

But you're correct in one way: If you always fill the tanks after each
flight, there won't be water in the tanks. No, not because there is no
condensation, but because you will have to drain a couple of gallons
before the each flight.

Stefan