lml@lancaironline.net Mailing List Archive

Gang,

The vast majority of answers on this subject have focused on the filtration benefits of the gascolator. I think Dennis Johnson's observations are spot on. If one carefully sumps the tanks (ensuring the aircraft is sitting on a level surface) prior to engine start it would be nigh impossible to get a coherent slug of water large enough and to interfere significantly with engine operation. This is especially true for fuel injected Continental installations, where a significant portion of the fuel pumped to the engine is unused and returned to the tank. Is it possible for a very large slug of water to remain coherent in five gallons of fuel while agitated by aircraft motion and fuel recirculation? I suppose it is, but it seems unlikely to me.

That aside, no one has mentioned ever finding water in the gascolator of their Lancair. Which makes sense, because in order to do so water would have flow uphill while on the ground, or remain separated enough from the fuel to fall out while flowing thru the gascolator at something approaching a half-a-gallon per minute while the engine is running.

Regarding the filtration capabilities of the gascolator; I've emailed Andair for more information on the specifications (filtration level, filter material area, max fuel flow, etc.), but they have yet to respond. If anyone has this information I would greatly appreciate it.

Kevin Stallard suggested the gascolator would appear to be a better option as a filter than an inline style. The type of inline filter I'm talking about is not your prototypical one-inch diameter, one-inch long plastic see-thru filter we've all seen on our lawnmowers. I talking about something more like this:

http://www.summitracing.com/parts/sum-230118-b/overview/

This filter is 1.75" in diameter and 6.25" long. If the filtration media was a simple cylinder that size would yield 30+ square inches of filtration area. Since the media is pleated (much like your typical oil filter), the filtration area is actually much larger. Maximum flow rate is 150 gph, which is more than three times that required for an IO-550. That suggests this filter could be two-thirds clogged with crud and still have adequate fuel flow. And let's not forget there would be one filter for each tank; if one clogs I can still switch tanks.

Additionally, this isn't a throw-one-in-and-hope-it-works scenario. These filters would be installed in a location making it exceptionally easy to remove for inspection/servicing--something that would occur following every engine run up to first flight. My reasoning is that such a test regimen will reveal any problems of the type mentioned here.

Thoughts?

--Mark

On Thu, Jul 24, 2014 at 4:39 PM, John B <2thman1@gmail.com> wrote:

Like most of you who responded I would not give up the gascolator. Have done two annuals since flying and both times have found almost a teaspoon of white fuzzy stuff. Fiberglass particles I'm virtually certain, and I thought I had done a perfect job of cleaning out the tanks before first flight.

John

Sent from my iPad

On Jul 24, 2014, at 11:15 AM, Robert R Pastusek <rpastusek@htii.com> wrote:

Adam,

My experience is the same as yours. I often found/drained water out of my old Cherokee tanks, and MANY rental airplanes as well. All were parked outside, and I think avgas came with a certain amount of “water added” in the old days… L

I’ve never found any water in the gascolator of my IV-P, so the fuel doesn’t have/collect any water…or it’s going through the engine and being vaporized--which I think unlikely. I know the gas caps are MUCH better than the old Cherokee “stoppers,” and I rarely park the Lancair outside these days.

Like you, I was meticulous in cleaning/keeping the fuel tanks/lines clean during fabrication and through flight test. I still collected some small amounts of carbon fuzz, and a few bits of aluminum in the gascolator during testing, and at the first two condition inspections. Almost undetectable bits of something for the last three, not enough to even identify when poured onto a piece of white paper… So the gascolator/filter is probably not serving a useful function today…but deleting it would be like throwing away the spare tire in my car, IMHO… I carry a few critical spare parts in my airplane for the same reason…

Bob

From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Adam Molny
Sent: Thursday, July 24, 2014 1:30 PM
To: Lancair Mailing List
Subject: [LML] Re: Gascolators and fuel lines.

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!

-Adam Molny

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.

What do you think?

--Mark

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?

--Mark