Hi Mark –
Our planes are kept in a heated hangar so
there’s no opportunity for water in the system from rain or condensation.
Back when I was renting Cessnas and Pipers I did occasionally drain water from the
gascolator. Those planes were kept outside.
The lowest point in the Legacy fuel system
is the fuel selector valve, but it’s not designed to capture water or
sediment like a gascolator. Your notion that the fuel flows too fast for water
to settle out is difficult to prove or disprove. I always envisioned tiny globs
of water flowing out of the fuel tanks and coalescing into a large glob of
water in the gascolator. The real test would be to pour a cup of water into one
wing tank, run the engine at high power, and see where the water ends up (in the
gascolator, out the tailpipe, or back to the fuel tank). However, deliberately
adding water to the fuel system seems like a bad idea so I’m not going to
try it.
I think you are saying you want fuel
filtration but there’s no point in having water separation since a
gascolator won’t work. Can you be 100% certain that you will never get
water in your system? What about flying through rain with a loose fuel cap?
What about being parked outside at Oshkosh
for a week? If you do get water in the system, where will it go? I hate to fall
back on the “It’s always been done that way” argument, but
gascolators exist for a reason.
For all the Legacy drivers out there: Have
any of you ever discovered water in the gascolator?
Good discussion!
From: Mark Sletten
[mailto:mwsletten@gmail.com]
Sent: Thursday, July 24, 2014 9:15
AM
To: Adam Molny
Subject: Re: Gascolators and fuel
lines.
Adam,
I wasn't questioning the value of fuel filtration, just whether a
gascolator is the best choice. As I understand it, the gascolator provides a
means to filter the fuel and a low point to catch water that may have gotten
into the fuel system. There are several arguments against using one for the
Legacy.
- In the Legacy the gascolator is not the lowest
point in the fuel delivery path from the tank to the engine, so water in
the tank should not flow to the gascolator before turning on the pumps. (I
believe the same is true of the RV. Has your wife ever drained any water
from her gascolator?)
- Given the high fuel flow rate and recirculation
of unused fuel to the tank, it's unlikely the gascolator will remove any
water with the engine running.
- The gascolator in the engine compartment provides
a large surface area to add heat to the fuel which can contribute to vapor
lock. Lancair combats this with a heat shroud and blast air, adding weight
and complexity.
- The gascolator requires numerous fittings and
breaks in the fuel lines, adding to complexity, weight and the possibility
of fuel leaks.
Since the gascolator appears to be rather useless at removing water,
it's primary function for the Legacy is filtration. With so many other
filtration options available, it seems illogical to put a gascolator in the
engine compartment.
On Thu, Jul 24, 2014 at 7:12 AM, Adam Molny <Adam@validationpartners.com>
wrote:
Mark –
The gascolator provides a large reservoir for capturing water and
sediment. It also contains a fine screen with a fairly large area that acts the
final filtration element to keep junk out of your carburetor or injector(s).
Case in point: my wife’s RV6-A started showing small amounts
of debris when sumping the fuel tank drains and gascolator. We opened up the
gascolator and found a small amount of debris at the bottom of the bowl, and
the screen was about 5% blocked. There was no immediate danger, since the bowl
would have to completely fill with debris and the screen would have to be 100%
blocked in order to kill the engine. It turned out to be bits of fuel tank
sealant flaking off.
My point here is that the gascolator acts as a buffer and gives you
lots of warning and lots of time to head off any potential fuel contamination
problem.
What is the argument for omitting the gascolator on fuel injected
engines?
-Adam Molny
Legacy N181AM 255hrs
From: Mark Sletten [mailto:mwsletten@gmail.com]
Sent: Wednesday, July 23, 2014
7:35 AM
Subject: Gascolators and fuel
lines.
Gang,
First:
Gascolators. There is a great deal of debate around the web on the benefits of
a gascolator in fuel injected systems. What's the consensus among
Lancairians?
Second: I'm
considering making my own engine compartment fuel lines. I plan to build them
up from scratch including the fire sleeve (or not if the hose is sufficiently
fire resistant). Anyone have a recommendation on the type of hose to use?