Avgas price and the light plane ownership

Answering Matt's statement that vapor lock has nothing to do with the
type of fuel: One reason why the FAA is reluctant to grant STC's for
mogas is because of its vapor-lock propensities. There have been
studies and plenty of discussion about the differences in vapor
pressure at the same temperature and pressure between avgas and mogas.
There was some discussion not long ago, iirc, in RAH. Google and you
will find.

wrote in message
ups.com...
Answering Matt's statement that vapor lock has nothing to do with the
type of fuel: One reason why the FAA is reluctant to grant STC's for
mogas is because of its vapor-lock propensities. There have been
studies and plenty of discussion about the differences in vapor
pressure at the same temperature and pressure between avgas and mogas.
There was some discussion not long ago, iirc, in RAH. Google and you
will find.



http://www.avweb.com/news/maint/187232-1.html

-------------------------
A large proportion of low-compression aircraft engines from both Lycoming
and Continental were originally certificated for operation on 80/87 octane
aviation gas. Most Lycoming O-235, O-290 and O-320 engines fall in this
category, and so do some of the larger O-360 and O-540 engines. Most
Continental O-200, O-300 and O-470 engines, and some of the fuel-injected
IO-470 and IO-520 engines can run it as well.
So, if you have a low-compression engine, can you just fill it up with
autogas and take off? Nope, you've got to get an appropriate STC -- and
despite what you may have heard elsewhere, it is very important to get that
STC, even though it usually will consist of one or two pieces of paper, plus
new decals for your fuel ports.

Why is the STC important? While unleaded autogas provides sufficient octane
to substitute for 80/87 avgas in low-compression engines, there are other
differences that can cause problems when using autogas in some engine
installations. The two most significant are lower vapor pressure -- which
can lead to vapor lock -- and incompatibility between some of the additives
in autogas and some components (particularly seals) in some aircraft fuel
systems.

In order to qualify for an STC, a particular airframe/engine combination has
to be rigorously tested, to include either a 150 hour engine endurance test
or 500 hour flight test, under controlled conditions. The tests also include
checking operation at high ambient temperatures, which can create vapor
lock. Some aircraft don't pass -- the Piper Apache and Comanche-250, and
Cessna Skyhawk with Avcon's 180HP conversion all failed testing, and cannot
legally run autogas.

In a nutshell, by buying the STC you are paying for a bunch of research and
testing to verify that it really is safe to use autogas in the
airframe/engine combination you have. In a few cases, you may be required to
have modifications made or the STC may authorize only premium (91 octane or
higher) autogas. For example, Petersen Aviation's STC for Piper
PA-28-160, -161, -180, and -181 models requires replacing the electric boost
pump and running premium gas.

-----------------------------

On 4-Jul-2005, "Matt Barrow" wrote:

Well, vapor lock has nothing to do with the type of fuel you're running.


On 4-Jul-2005, "Matt Barrow" wrote:

While unleaded autogas provides sufficient octane
to substitute for 80/87 avgas in low-compression engines, there are other
differences that can cause problems when using autogas in some engine
installations. The two most significant are lower vapor pressure -- which
can lead to vapor lock -- and incompatibility between some of the
additives in autogas and some components (particularly seals) in some
aircraft fuel
systems.


Hmm.... either there are two Matt Barrows (using the same e-mail address)
or else he is schizophrenic. Judging from some of his political views, I'd
say the later is a distinct possibility.
--
-Elliott Drucker

wrote in message
news:OWiye.14793$mr4.13119@trnddc05...
On 4-Jul-2005, "Matt Barrow" wrote:

Well, vapor lock has nothing to do with the type of fuel you're running.


On 4-Jul-2005, "Matt Barrow" wrote:

While unleaded autogas provides sufficient octane
to substitute for 80/87 avgas in low-compression engines, there are other
differences that can cause problems when using autogas in some engine
installations. The two most significant are lower vapor pressure -- which
can lead to vapor lock -- and incompatibility between some of the
additives in autogas and some components (particularly seals) in some
aircraft fuel
systems.


Hmm.... either there are two Matt Barrows (using the same e-mail address)
or else he is schizophrenic. Judging from some of his political views,
I'd
say the later is a distinct possibility.
--
-Elliott Drucker

I'm keeping out of the politics on this one, except to say that two out of
every one of us could be schizophrenic.
After talking to a Shell Guru at a seminar my understanding is that the
vapour pressure issue with mogas can be of real concern and that mogas is
best used for low altitude work. His other push was the relative quality of
avgas versus mogas - not just in manufacture but in distribution. With what
I find in many of the auto fuel filters I change, I'd have to agree. I have
had about 15 cases from one local servo in the past 8 to 10 weeks. Now
that, in Oz, ethanol is included in much mogas, not to mention the odd
toluene shonk, I would be wary about mogas use for long haul or high
altitude. Also goes without saying that you don't get as far on a litre of
fuel containing ethanol and/or toluene.
Brian

wrote in message
news:OWiye.14793$mr4.13119@trnddc05...
On 4-Jul-2005, "Matt Barrow" wrote:

Well, vapor lock has nothing to do with the type of fuel you're running.


On 4-Jul-2005, "Matt Barrow" wrote:

While unleaded autogas provides sufficient octane
to substitute for 80/87 avgas in low-compression engines, there are
other
differences that can cause problems when using autogas in some engine
installations. The two most significant are lower vapor pressure --
which
can lead to vapor lock -- and incompatibility between some of the
additives in autogas and some components (particularly seals) in some
aircraft fuel
systems.


Hmm.... either there are two Matt Barrows (using the same e-mail address)
or else he is schizophrenic. Judging from some of his political views,
I'd
say the later is a distinct possibility.

It's called correcting myself.

You call it schizophrenia, I call it maturity.

Get a ****ing clue, statist prick!

On 5-Jul-2005, "Matt Barrow" wrote:

Hmm.... either there are two Matt Barrows (using the same e-mail
address)
or else he is schizophrenic. Judging from some of his political views,
I'd say the latter is a distinct possibility.

It's called correcting myself.

You call it schizophrenia, I call it maturity.

Get a ****ing clue, statist prick!


Yeah, right.

For a while I was confused. How could someone as clearly challenged by the
English language (and common logic) as Mr. Barrow have composed the lucid
and intelligent comments in his second post regarding vapor lock (which
completely contradicted his earlier post on THE SAME DAY)? However, I took
his advice to heart and "got a clue." A simple Google search on the phrase
"incompatibility between some of the additives in autogas" pointed me to the
following website:
http://www.aviation-indonesia.com/mo...rticle&knid=16
It seems that in addition to his wealth of other shortcomings Mr. Barrow is
also a plagiarist.
--
-Elliott Drucker

wrote in message
news:hByye.50$VN3.15@trnddc01...
For a while I was confused. How could someone as clearly challenged by
the
English language (and common logic) as Mr. Barrow have composed the lucid
and intelligent comments in his second post regarding vapor lock (which
completely contradicted his earlier post on THE SAME DAY)? However, I
took
his advice to heart and "got a clue." A simple Google search on the
phrase
"incompatibility between some of the additives in autogas" pointed me to
the
following website:
http://www.aviation-indonesia.com/mo...rticle&knid=16
It seems that in addition to his wealth of other shortcomings Mr. Barrow
is
also a plagiarist.

Actually, he did cite the source of the words in that post, though it may
not have been obvious that he was doing so.

--Gary

Does the phrase "fermented grape juice" spring lightly to the tongue?

Jim




For a while I was confused. How could someone as clearly challenged by
the
English language (and common logic) as Mr. Barrow have composed the lucid
and intelligent comments in his second post regarding vapor lock (which
completely contradicted his earlier post on THE SAME DAY)?

On 5-Jul-2005, "Gary Drescher" wrote:

Actually, he did cite the source of the words in that post, though it may
not have been obvious that he was doing so.

It appears that the citation was somehow blocked from the viewing window of
my news reader, but I see it now upon re-loading the post. My apologies to
Mr. Barrow for the comments regarding plagiarism.

-Elliott Drucker