Hot weather and autogas?

[Rich S.]

Hi Troop..........

The weather forecast for Idaho today is staggering! 107° F in Boise, 108° in
Twin Falls and 110° in Mountain Home. Montana is similar with 108° forecast
in Helena.

Last year, on my way to OSH, I planned my fuel stops to take advantage of
autogas availability. I stopped at Pullman, WA and filled up. As we were
flying past Helena, Montana, the OAT showed 85° at 9500'. Fuel pressure went
to zero and the electric pump (ahead of the firewall) made no difference.
Within one minute the engine quit. Not rough. QUIT.

I'll spare you the details, but fortunately, as I was about to turn downwind
for a soybean field, it had cooled off enough to restart. Cautiously, we
climbed and made our way to Helena, 25 miles distant. Draining the autofuel
and filling up with 100 LL solved the problem.

Unless you are *absolutely* sure that your engine will not vapor lock in
extreme temperatures, do not run autogas. It is not worth the few bucks
difference. Don't worry about the 100 LL fouling a plug or two - your plane
will still fly.

I am not looking for an discussion or argument about autogas. I use it
regularly in moderate temps. I will not use it when the mercury rises to
these levels.

Keep 'em flying,
Rich S.

[Larry Smith]

"Rich S." > wrote in message
...
> Hi Troop..........
>
> The weather forecast for Idaho today is staggering! 107° F in Boise, 108°
in
> Twin Falls and 110° in Mountain Home. Montana is similar with 108°
forecast
> in Helena.
>
> Last year, on my way to OSH, I planned my fuel stops to take advantage of
> autogas availability. I stopped at Pullman, WA and filled up. As we were
> flying past Helena, Montana, the OAT showed 85° at 9500'. Fuel pressure
went
> to zero and the electric pump (ahead of the firewall) made no difference.
> Within one minute the engine quit. Not rough. QUIT.

What were you flying?

Fuel pumps work better against vapor-lock when closer to the source.
>
> I'll spare you the details, but fortunately, as I was about to turn
downwind
> for a soybean field, it had cooled off enough to restart. Cautiously, we
> climbed and made our way to Helena, 25 miles distant. Draining the
autofuel
> and filling up with 100 LL solved the problem.
>
> Unless you are *absolutely* sure that your engine will not vapor lock in
> extreme temperatures, do not run autogas. It is not worth the few bucks
> difference. Don't worry about the 100 LL fouling a plug or two - your
plane
> will still fly.
>
> I am not looking for an discussion or argument about autogas. I use it
> regularly in moderate temps. I will not use it when the mercury rises to
> these levels.
>
> Keep 'em flying,
> Rich S.

Yes, mogas is more volatile, but couldn't you have mixed it with 100LL? Do
you have your firewall-forward fuel lines well-insulated with firesleeves?
A friend complained about vapor-lock until he band-it clamped that orange
silicone Aeroquip stuff on his lines. And don't forget to seal it on the
ends so that oil and fuel don't soak into the insulation. See Tony
Bingelis on Firewall Forward. Some people seal it with RTV silicone, some
with that expensive stuff Tony says to buy as a group.

Better to discuss it than not to discuss it. And then have to cuss it
later.

[BRUCE FRANK]

What kind of plane? I used to have high desert vapor lock on my old
International Travelall...5000 feet and 110 degrees F in the shade. Nothing
I did, and I mean NOTHING stopped the vapor lock problems until!!! I
installed an electric fuel pump at the fuel tank With insulated fuel lines
in the engine compartment and a 1/16" diameter bleed line that vented back
to the tank (so that after sitting for a while any vapor that formed in the
line would vent back to the tank unblocking the line when I flipped on the
fuel pump....the bleed line was insurance as I ran it almost a year with the
tank mounted fuel pump with no problems...The fuel pump seemed to create
enough pressure to collapse or force through any bubbles in the line...but
the heat soaked engine would start more quickly once the bleed line was
installed) I also by-passed the block mounted fuel pump to reduce engine
block heat transfer into the fuel. I put another 100,000 miles on that
vehicle, most of it rock crawling in Utah's Canyonlands in the summer time,
with never even a hic-up caused by fuel vapor blocking the line.

Bruce A. Frank

"Rich S." > wrote in message
...
> Hi Troop..........
>
> The weather forecast for Idaho today is staggering! 107° F in Boise, 108°
in
> Twin Falls and 110° in Mountain Home. Montana is similar with 108°
forecast
> in Helena.
>
> Last year, on my way to OSH, I planned my fuel stops to take advantage of
> autogas availability. I stopped at Pullman, WA and filled up. As we were
> flying past Helena, Montana, the OAT showed 85° at 9500'. Fuel pressure
went
> to zero and the electric pump (ahead of the firewall) made no difference.
> Within one minute the engine quit. Not rough. QUIT.
>
> I'll spare you the details, but fortunately, as I was about to turn
downwind
> for a soybean field, it had cooled off enough to restart. Cautiously, we
> climbed and made our way to Helena, 25 miles distant. Draining the
autofuel
> and filling up with 100 LL solved the problem.
>
> Unless you are *absolutely* sure that your engine will not vapor lock in
> extreme temperatures, do not run autogas. It is not worth the few bucks
> difference. Don't worry about the 100 LL fouling a plug or two - your
plane
> will still fly.
>
> I am not looking for an discussion or argument about autogas. I use it
> regularly in moderate temps. I will not use it when the mercury rises to
> these levels.
>
> Keep 'em flying,
> Rich S.
>
>

[Cy Galley]

Well Rich, It was only 77 ° today. Supposed to get down to high 40s or low
50 tonight and we are 160 miles south of Oshkosh. Is supposed to get to 90
some this week end but I am heading North this Friday to look for green
planes that break off axles.
<GRIN>

Have a safe flight!

--
Cy Galley, TC - Chair, Emergency Aircraft Repair, Oshkosh

Editor, EAA Safety Programs
or

Always looking for articles for the Experimenter

"Rich S." > wrote in message
...
> Hi Troop..........
>
> The weather forecast for Idaho today is staggering! 107° F in Boise, 108°
in
> Twin Falls and 110° in Mountain Home. Montana is similar with 108°
forecast
> in Helena.
>
> Last year, on my way to OSH, I planned my fuel stops to take advantage of
> autogas availability. I stopped at Pullman, WA and filled up. As we were
> flying past Helena, Montana, the OAT showed 85° at 9500'. Fuel pressure
went
> to zero and the electric pump (ahead of the firewall) made no difference.
> Within one minute the engine quit. Not rough. QUIT.
>
> I'll spare you the details, but fortunately, as I was about to turn
downwind
> for a soybean field, it had cooled off enough to restart. Cautiously, we
> climbed and made our way to Helena, 25 miles distant. Draining the
autofuel
> and filling up with 100 LL solved the problem.
>
> Unless you are *absolutely* sure that your engine will not vapor lock in
> extreme temperatures, do not run autogas. It is not worth the few bucks
> difference. Don't worry about the 100 LL fouling a plug or two - your
plane
> will still fly.
>
> I am not looking for an discussion or argument about autogas. I use it
> regularly in moderate temps. I will not use it when the mercury rises to
> these levels.
>
> Keep 'em flying,
> Rich S.
>
>

[Jim Weir]

Cy...

I know you've got your share of volunteers, but if you need an IA to sign of a
certificated major repair, I'm happy to do it. I'll be on the field from Monday
to Saturday...leave a note for me in the press tent if you need help.

Obviously...no charge. (Knew you knew this, but had to say it.)

Jim



"Cy Galley" >
shared these priceless pearls of wisdom:

I am heading North this Friday to look for green
->planes that break off axles.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Rich S.]

"Cy Galley" > wrote in message
news:HzGTa.130839$ye4.92382@sccrnsc01...
> Well Rich, It was only 77 ° today. Supposed to get down to high 40s or
low
> 50 tonight and we are 160 miles south of Oshkosh. Is supposed to get to
90
> some this week end but I am heading North this Friday to look for green
> planes that break off axles.
> <GRIN>
>
> Have a safe flight!

Not coming this year, Cy. I have imposed enough on the good offices of the
Emergency Repair Crew. I hope you guys will have a relatively quiet time of
it. Please tell the crew that I am thinking of them and still remember their
good-natured and able assistance. 2002 was a year to remember, for sure.

Rich S.

P.S. Current temperature in Helena, MT @ 8 PM is 96°.

[Jay Honeck]

> P.S. Current temperature in Helena, MT @ 8 PM is 96°.

And tonight in Iowa City, IA we're expecting record-breaking LOW
temperatures. It is absolutely perfect sleeping temperature.

But I suppose your blazing heat will arrive in the Midwest just in time for
(you guessed it!) Oshkosh 2003...
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Rich S.]

"Bob Olds" > wrote in message
om...
>
> I use a mixture of 100LL and mogas. My RV-4 sat in the sun all day
> with temp. 95 F. As I taxied I noticed a miss now & then,so I turned
> on the electric boost pump and had no further problem in the flight.
> My boost pump is located beside the fuel selector valve,at the lowest
> point possible.
> The engine driven pump makes suction in the fuel line from the valve
> to the pump. With a suction/vacuum the boiling point is lowered =
> vapor lock.
> With a boost pump in the engine compartment, you add another hot place
> for the fuel to boil.
> I have had the same problems with 80 oct.,100LL and mogas. They are
> all problems when the tank gets so hot.
>
> Bob Olds RV-4 , N1191X

Bob.............

Your recommendations to prevent vapor lock are sound. However, unless you
have tested the system under actual extreme conditions, it is best to not
trust it. 100 LL (much as I hate its cost and tendency to foul plugs) is
more resistant to vapor lock than mogas. Especially mogas out of a tank at
an airport which may be last Winter's blend.

Rich S.

[BRUCE FRANK]

Rich,

All I was doing was offering a relatively straight forward mod of the fuel
system that will prevent fuel blocking vapor lock. I know of several home
builders who have made similar mods to their fuel system to assure trouble
free operation. Heck, I have read stories of low wing aircraft vapor locking
on 100LL, so avgas is not the panacea for a system running hot and high.

Bruce A. Frank

"Rich S." > wrote in message
...
> "BRUCE FRANK" > wrote in message
> ...
> > What kind of plane? snip.....
>
> Bruce..............
>
> Read the post again. If you are *absolutely* sure that "YOUR ENGINE" will
> not vapor lock - have a ball. Burn kerosene if'n you want. If you have the
> slightest doubt, put in 100 LL fer chissake. I'm trying to prevent anyone
> else in this group from having a problem.
>
> Repeat - I am not trying to start an argument about autofuel. I am trying
to
> warn those folks who have been happily burning car gas (as I was) at low
> altitudes and moderate temperatures. It ain't gonna freakin' work at
10,000'
> when you can fry eggs on the cowling.
>
> Rich S.
>
>

[Bill Daniels]

I've posted this story before but this thread seems a good time to repeat
it.

One hot afternoon in Albuquerque I was pre-flighting my Archer and noticed
that the 100LL in the fuel tester was fizzing like champagne. I showed the
fuel tester to another pilot who was also pre-flighting his homebuilt. He
in turn showed me his tester full of amber auto gas which showed no bubbling
at all. In this case, the mogas clearly had a much higher vapor pressure
than the 100LL. I chose to delay my departure until the next morning - he
fired up and flew away.

On the other hand, during a recent road trip to New Mexico, my Jeep Grand
Cherokee suffered two fuel pump failures within a week - both pumps were
brand new. The failure mode was possibly due to winter gasoline blend that
was mistakenly shipped to service stations during the hot season as a result
of the ongoing shortfall in US gasoline stocks. Winter gas has a big load
of volatile components to aid cold starting but will boil and vapor lock in
the summer. In my case, the volatile fuel likely caused the in-tank fuel
pump to cavitate, overheat and fail.

The service writers in both dealerships who replaced the bad pumps told me
that they had been inundated with fuel pump failures and otherwise
unexplained hot stalling.

Diesels are sounding better all the time.

Bill Daniels

[Rich S.]

"Andre" > wrote in message
...
> I have seen on the Great Plains Web site that they repeatedly recommend
> using a fuel pump.
> They also recommend putting the fuel pump between the Gascolator and the
> Carb.
> What happens if the fuel pump fails or loses power?
> How much fuel pressure will the fuel pump add?
> Won't the aditional fuel pressure possibly flood the carb?
> How do I rig a return line to the fuel tank?
> Why should a fuel pump be installed between the gascolator and carb?
> Any Ideas?

Andre.........

An electric fuel pump shuts off when the fuel pressure rises to ~6 psig. The
carb needle valve easily handles that much. If the fuel pump is downstream
of the gascolator, the gascolator isn't pressurized. This reduces the
possibility of a gascolator failure which could dump your fuel in a hurry.

It also means that the electric fuel pump is ahead of the firewall. This is
both good and bad. In the event of a fuel leak in the cockpit, the pump
won't be helping to fill the footwell with gas. The bad part is the pump is
exposed to engine heat. In the Sonerai, as in the RV's, I'd install the
electric pump at the tank outlet. Electric pumps push fuel much better than
they pull it.

Just my opinion, tho.
Rich S.

[Rich S.]

"Barnyard BOb --" > wrote in message
...
>
> Definitely words to 'live' by, Rich.
>
> Coming back from Seattle to Kansas City
> after visiting with you Arlington yahoos--
> it was IFR... and Rand McNally all the way.
> Never got over 9500 feet through the Rockies.
>
>
> Barnyard BOb - I_F_ollow_R_oads
>
> >>> 50 years of flight <<<

After Helena, my child bride wisely *insisted* that we do just that. We were
both a lot happier within gliding distance of that nice big SAC runway that
DDE spent our taxes building.

There are a lot of acres in Montana that even the jackrabbits pack a lunch
to cross.

Rich S.

[Cy Galley]

Got down to 41° last night. Didn't break 80 today, Maybe by Sunday it will
go to 90 but by that time I'll be in cool Oshkosh. Sorry you won't make it.
it will be my 32nd.

Cy Galley, TC - Chair, Emergency Aircraft Repair, Oshkosh
Editor, EAA Safety Programs
or

Always looking for articles for the Experimenter

"Rich S." > wrote in message
...
> "Cy Galley" > wrote in message
> news:HzGTa.130839$ye4.92382@sccrnsc01...
> > Well Rich, It was only 77 ° today. Supposed to get down to high 40s or
> low
> > 50 tonight and we are 160 miles south of Oshkosh. Is supposed to get
to
> 90
> > some this week end but I am heading North this Friday to look for green
> > planes that break off axles.
> > <GRIN>
> >
> > Have a safe flight!
>
> Not coming this year, Cy. I have imposed enough on the good offices of the
> Emergency Repair Crew. I hope you guys will have a relatively quiet time
of
> it. Please tell the crew that I am thinking of them and still remember
their
> good-natured and able assistance. 2002 was a year to remember, for sure.
>
> Rich S.
>
> P.S. Current temperature in Helena, MT @ 8 PM is 96°.
>
>

[BRUCE FRANK]

Adding a blast tube to direct fresh air onto the pumps helps.

Bruce A. Frank

"Rich S." > wrote in message
...
> "Andre" > wrote in message
> ...
> > I have seen on the Great Plains Web site that they repeatedly recommend
> > using a fuel pump.
> > They also recommend putting the fuel pump between the Gascolator and the
> > Carb.
> > What happens if the fuel pump fails or loses power?
> > How much fuel pressure will the fuel pump add?
> > Won't the aditional fuel pressure possibly flood the carb?
> > How do I rig a return line to the fuel tank?
> > Why should a fuel pump be installed between the gascolator and carb?
> > Any Ideas?
>
> Andre.........
>
> An electric fuel pump shuts off when the fuel pressure rises to ~6 psig.
The
> carb needle valve easily handles that much. If the fuel pump is downstream
> of the gascolator, the gascolator isn't pressurized. This reduces the
> possibility of a gascolator failure which could dump your fuel in a hurry.
>
> It also means that the electric fuel pump is ahead of the firewall. This
is
> both good and bad. In the event of a fuel leak in the cockpit, the pump
> won't be helping to fill the footwell with gas. The bad part is the pump
is
> exposed to engine heat. In the Sonerai, as in the RV's, I'd install the
> electric pump at the tank outlet. Electric pumps push fuel much better
than
> they pull it.
>
> Just my opinion, tho.
> Rich S.
>
>

[Barnyard BOb --]

>Adding a blast tube to direct fresh air onto the pumps helps.
>
>Bruce A. Frank
+++++++++++++++++++++++++++++++++++++++

HELPS?

ARRGH!

"HELPS" is not good enough.
In fact, going down the road of "helps"....
is a very dangerous and risky one.

A FIX is what is required.
Nothing less is acceptable.
Nothing less is defensible, IMO.


Barnyard BOb --
================================================== =


>
>"Rich S." > wrote in message
...
>> "Andre" > wrote in message
>> ...
>> > I have seen on the Great Plains Web site that they repeatedly recommend
>> > using a fuel pump.
>> > They also recommend putting the fuel pump between the Gascolator and the
>> > Carb.
>> > What happens if the fuel pump fails or loses power?
>> > How much fuel pressure will the fuel pump add?
>> > Won't the aditional fuel pressure possibly flood the carb?
>> > How do I rig a return line to the fuel tank?
>> > Why should a fuel pump be installed between the gascolator and carb?
>> > Any Ideas?
>>
>> Andre.........
>>
>> An electric fuel pump shuts off when the fuel pressure rises to ~6 psig.
>The
>> carb needle valve easily handles that much. If the fuel pump is downstream
>> of the gascolator, the gascolator isn't pressurized. This reduces the
>> possibility of a gascolator failure which could dump your fuel in a hurry.
>>
>> It also means that the electric fuel pump is ahead of the firewall. This
>is
>> both good and bad. In the event of a fuel leak in the cockpit, the pump
>> won't be helping to fill the footwell with gas. The bad part is the pump
>is
>> exposed to engine heat. In the Sonerai, as in the RV's, I'd install the
>> electric pump at the tank outlet. Electric pumps push fuel much better
>than
>> they pull it.
>>
>> Just my opinion, tho.
>> Rich S.
>>
>>
>

[Andre]

Thanx all!
I'm reading these comments as if my life depends on it...
Can anyone recommend more reading material on the topic please?
Rich I see you mention: "if Tony Bingelis had devoted a full page in
"Firewall Forward""
Is that a book?
And is that good reading?
Andre

"Barnyard BOb --" > wrote in message
...
>
> >Adding a blast tube to direct fresh air onto the pumps helps.
> >
> >Bruce A. Frank
> +++++++++++++++++++++++++++++++++++++++
>
> HELPS?
>
> ARRGH!
>
> "HELPS" is not good enough.
> In fact, going down the road of "helps"....
> is a very dangerous and risky one.
>
> A FIX is what is required.
> Nothing less is acceptable.
> Nothing less is defensible, IMO.
>
>
> Barnyard BOb --
> ================================================== =
>
>
> >
> >"Rich S." > wrote in message
> ...
> >> "Andre" > wrote in message
> >> ...
> >> > I have seen on the Great Plains Web site that they repeatedly
recommend
> >> > using a fuel pump.
> >> > They also recommend putting the fuel pump between the Gascolator and
the
> >> > Carb.
> >> > What happens if the fuel pump fails or loses power?
> >> > How much fuel pressure will the fuel pump add?
> >> > Won't the aditional fuel pressure possibly flood the carb?
> >> > How do I rig a return line to the fuel tank?
> >> > Why should a fuel pump be installed between the gascolator and carb?
> >> > Any Ideas?
> >>
> >> Andre.........
> >>
> >> An electric fuel pump shuts off when the fuel pressure rises to ~6
psig.
> >The
> >> carb needle valve easily handles that much. If the fuel pump is
downstream
> >> of the gascolator, the gascolator isn't pressurized. This reduces the
> >> possibility of a gascolator failure which could dump your fuel in a
hurry.
> >>
> >> It also means that the electric fuel pump is ahead of the firewall.
This
> >is
> >> both good and bad. In the event of a fuel leak in the cockpit, the pump
> >> won't be helping to fill the footwell with gas. The bad part is the
pump
> >is
> >> exposed to engine heat. In the Sonerai, as in the RV's, I'd install the
> >> electric pump at the tank outlet. Electric pumps push fuel much better
> >than
> >> they pull it.
> >>
> >> Just my opinion, tho.
> >> Rich S.
> >>
> >>
> >
>

[Barnyard BOb --]

>
>"Barnyard BOb --" > wrote in message
...
>>
>> >Adding a blast tube to direct fresh air onto the pumps helps.
>> >
>> >Bruce A. Frank
>> +++++++++++++++++++++++++++++++++++++++
>>
>> HELPS?
>>
>> ARRGH!
>>
>> "HELPS" is not good enough.
>> In fact, going down the road of "helps"....
>> is a very dangerous and risky one.
>>
>> A FIX is what is required.
>> Nothing less is acceptable.
>> Nothing less is defensible, IMO.
>>
>>
>> Barnyard BOb --


>Alright already! Poor selection of words! To eliminate the likelihood of
>vapor lock, an electric fuel pump on the engine side of the firewall needs
>to be installed so as to be bathed in a good flow of unheated air or, if
>such a position is not available, a blast tube must be installed! Definitive
>enough?
>
>Bruce A. Frank
+++++++++++++++++++++++++++++++++++++

Sorry, my point has nothing to do with parsing a definition.
Every fuel system on mogas needs to be TESTED/PROVEN
per Rich S.'s parameters. Screw warm and fuzzy definitions.

For my money, the electric fuel pump should be installed
OUTSIDE the engine compartment and PUSH the mogas....
not suck it, to the engine - if I'm going to even consider
mogas at 10,000 feet at elevated temps, like 90+ degrees.

FWIW -
My RV-3 with gravity feed system has run on mogas
for over 440 hours [for me] without a stumble or burp.
Some of it has been at 9500 ft at elevated temps, but
not enough to feel 100% safe on every possible blend,
combination and variant of mogas.

Rich S. has made a believer out of me when it comes
to mogas, mountain flying and high summer temps.
I'll not do it..... no matter where the electric fuel pump
or blast tube is or isn't.


Barnyard BOb -- to old to be bold

[Rich S.]

"Andre" > wrote in message
...
> Thanx all!
> I'm reading these comments as if my life depends on it...
> Can anyone recommend more reading material on the topic please?
> Rich I see you mention: "if Tony Bingelis had devoted a full page in
> "Firewall Forward""
> Is that a book?
> And is that good reading?

It is. Tony was a writer for Sport Aviation for many years, a prolific
builder and an avid proponent of homebuilding. Among many other airplanes,
he built two - TWO - Emeraudes. Building just one is more than enough for
one lifetime! He built several of the Van's RV series and a Falco.

His books are available through the EAA and many other sources. You'll
probably find some in the FlyMart at OSH. They are a must-read for every
homebuilder.

Rich S.

[BRUCE FRANK]

But BOb, my first post emphasized pushing the fuel. The follow up was a
comment on assuring cool components to prevent vapor lock.

Hmmm, I'm outa practice here...been working too much (sometimes actually
working on my plane) and my editorial composition skills appear to have
degraded somewhat. I'll endeavor to remedied that.

Bruce A. Frank

"Barnyard BOb --" > wrote in message
...
>
> >
> >"Barnyard BOb --" > wrote in message
> ...
> >>
> >> >Adding a blast tube to direct fresh air onto the pumps helps.
> >> >
> >> >Bruce A. Frank
> >> +++++++++++++++++++++++++++++++++++++++
> >>
> >> HELPS?
> >>
> >> ARRGH!
> >>
> >> "HELPS" is not good enough.
> >> In fact, going down the road of "helps"....
> >> is a very dangerous and risky one.
> >>
> >> A FIX is what is required.
> >> Nothing less is acceptable.
> >> Nothing less is defensible, IMO.
> >>
> >>
> >> Barnyard BOb --
>
>
> >Alright already! Poor selection of words! To eliminate the likelihood of
> >vapor lock, an electric fuel pump on the engine side of the firewall
needs
> >to be installed so as to be bathed in a good flow of unheated air or, if
> >such a position is not available, a blast tube must be installed!
Definitive
> >enough?
> >
> >Bruce A. Frank
> +++++++++++++++++++++++++++++++++++++
>
> Sorry, my point has nothing to do with parsing a definition.
> Every fuel system on mogas needs to be TESTED/PROVEN
> per Rich S.'s parameters. Screw warm and fuzzy definitions.
>
> For my money, the electric fuel pump should be installed
> OUTSIDE the engine compartment and PUSH the mogas....
> not suck it, to the engine - if I'm going to even consider
> mogas at 10,000 feet at elevated temps, like 90+ degrees.
>
> FWIW -
> My RV-3 with gravity feed system has run on mogas
> for over 440 hours [for me] without a stumble or burp.
> Some of it has been at 9500 ft at elevated temps, but
> not enough to feel 100% safe on every possible blend,
> combination and variant of mogas.
>
> Rich S. has made a believer out of me when it comes
> to mogas, mountain flying and high summer temps.
> I'll not do it..... no matter where the electric fuel pump
> or blast tube is or isn't.
>
>
> Barnyard BOb -- to old to be bold
>

[Rich S.]

"Andre" > wrote in message
...
> Thanx Rich!
> I have just placed my orderfor the "Firewall Forward" book.
> Hopefully UPS will have it here in South Africa by the end of the week.
> Now I'm looking forward to some winter reading in front of the fireplace!
> :-)
> Question: How does Tony Bingelis "Firewall Forward" book compare to
> "Bingelis on Engines", considering that I'm running a VW engine?

The two books are comparable, Andre. "Firewall Forward" may be a bit more
comprehensive, but "TB on Engines" appears to be a later, slicker volume. I
bought the whole series - as little as I knew about aircraft when I started
my project, I needed all the help I could get!

Rich S.

[Rich S.]

"Michael" > wrote in message
om...
> That's the key question. Until I hear evidence to
> the contrary, I'm going to keep on believing that gravity feed
> carbureted systems that have a reasonable (say 2 ft or better)
> vertical distance between tank pickup and carb inlet are immune to all
> this vapor lock stuff.

Believe whatever you like.

Rich S.

[Barnyard BOb --]

>"Michael" posted:

>> That's the key question. Until I hear evidence to
>> the contrary, I'm going to keep on believing that gravity feed
>> carbureted systems that have a reasonable (say 2 ft or better)
>> vertical distance between tank pickup and carb inlet are immune to all
>> this vapor lock stuff.
>
>Believe whatever you like.
>
>Rich S.
++++++++++++++++++++++++++++++++++++++++++++

Anecdotally speaking....

My GRAVITY fed RV3 has been totally immune to
vapor lock after logging more than 440 hours in it.
The vertical distance has remained less than 2 ft
for over 17 years.

P.S.
Not yet sure certain what can be believed.

P.P.S.
A greater 'fall' is certainly desirable.

YMMV.


Barnyard BOb --

[Andre]

Thanx Rich,
I think I will do the books one by one.
I am currently removing the engine from my Sonerai to redo the whole engine
installation.
I think I am going to hang on until I have gone through the book in detail.
Regards
Andre

"Rich S." > wrote in message
...
> "Andre" > wrote in message
> ...
> > Thanx Rich!
> > I have just placed my orderfor the "Firewall Forward" book.
> > Hopefully UPS will have it here in South Africa by the end of the week.
> > Now I'm looking forward to some winter reading in front of the
fireplace!
> > :-)
> > Question: How does Tony Bingelis "Firewall Forward" book compare to
> > "Bingelis on Engines", considering that I'm running a VW engine?
>
> The two books are comparable, Andre. "Firewall Forward" may be a bit more
> comprehensive, but "TB on Engines" appears to be a later, slicker volume.
I
> bought the whole series - as little as I knew about aircraft when I
started
> my project, I needed all the help I could get!
>
> Rich S.
>
>

[Michael]

"Rich S." > wrote
> > That's the key question. Until I hear evidence to
> > the contrary, I'm going to keep on believing that gravity feed
> > carbureted systems that have a reasonable (say 2 ft or better)
> > vertical distance between tank pickup and carb inlet are immune to all
> > this vapor lock stuff.
>
> Believe whatever you like.

So prove me wrong. Show me a counterexample.

Michael

[Rich S.]

"Dave" > wrote in message
...
>
> Summer vapor pressure figures are 9.0 PSI @ 100degrees

Typical undercowl temperatures on a 100° day can double that.

Rich S.

[Rich S.]

"Michael" > wrote in message
om...
> "Rich S." > wrote
> > > That's the key question. Until I hear evidence to
> > > the contrary, I'm going to keep on believing that gravity feed
> > > carbureted systems that have a reasonable (say 2 ft or better)
> > > vertical distance between tank pickup and carb inlet are immune to all
> > > this vapor lock stuff.
> >
> > Believe whatever you like.
>
> So prove me wrong. Show me a counterexample.
>
> Michael

Michael..........

I went back and re-read the entire thread and, you're right, I failed to
identify my airplane and to describe the fuel system configuration. It is an
Emeraude, powered with a Lycoming O-320-E3D and having a mechanical fuel
pump on the engine. There is a Bendix electric fuel pump mounted on the
engine side of the firewall, downstream of a gascolator. All the lines are
firesleeved and are well clear of the exhaust system. There is no vapor
return line. There is a fuel pressure gauge teed in at the carburetor. A
manual primer pump takes its feed from the gascolator and is piped to all
four cylinders at the intake ports. The carb has a stock accelerator pump.

There are two 20 gallon fuel tanks, one located ahead of the instrument
panel and the other behind the seat. The nose tank has about 15" of head
above the carb inlet when the aircraft is level. There is a tank selector
valve mounted on the left kick panel. The rear tank is almost level with the
carb. The tank vents exit the bottom of the fuselage at 90° to the
slipstream and received no pressure "boost" from it. I have no idea how much
the restrictions in the fuel line (filters, check valves in the pumps,
fittings, etc.) affect the head pressure or fuel flow. The fuel system is
virtually identical with the one depicted in Fig. 4, Pg. 172 of "Firewall
Forward" by Tony Bingelis and titled "Typical Pump Fed Fuel System".

On a hot day, oil temps may exceed 200° F in the climb and run about 180° F
at cruise. Long climbs at high altitudes will bump these numbers. My oil
temp gauge has not been calibrated, but I think it's pretty close. Cylinder
head temps run 400° - 425° F in climb and 350° - 375° at cruise.

The airplane had flown over 200 hours with no mechanical problems to speak
of. It had operated perfectly in 90° temperatures and at altitudes up to
13,500' - but never both at the same time.

I hold a commercial SEL ticket with an instrument rating. I still have a CFI
card, but it has not been renewed for 20 years or so. I have logged some
1500 hours over the last 55 years and haven't logged probably another thou.
I've scared myself more times than I like to remember but have somehow
managed to survive without ever putting a scratch on an airplane due to
pilot error. One of the reasons for this luck is that I keep an open mind
and listen to those who have gone before.

On the day I experienced vapor lock and loss of power, the selector valve
was set on the nose tank and it was at least 2/3 full, adding another 10" to
the head distance. We were at 9,500' and the OAT was 85°. The electric pump
was turned off in cruise and the fuel pressure gauge had been reading just
above red line at ~2 lbs. As I was scanning the gauges, I saw the fuel
pressure fall to zero while I watched. I immediately turned the plane
towards a soybean field I has just passed. By the time I completed the turn,
the engine lost power.

I turned on the electric pump and switched to the rear tank. Nothing. The
engine must have been getting little dribbles of fuel, because the vibration
was severe. There was no noticeable thrust from the prop, however. My wife
was becoming hysterical, adding to the situation. I put out a Mayday to Salt
Lake Center in order to get through on the frequency - it was quite busy and
I wanted someone apprised of our situation and location at once. As we
descended, I did indeed lose line-of-sight and relied on a relay through an
overflying cargo flight (Thanks again, Matt!)

We lost about 7,000' and I was just setting up to enter a downwind leg for
the bean field. All attempts at a restart had failed. I admit that I had
forgotten to try the manual prime pump. On the Emeraude, I have a fold-down
instrument panel and the primer is mounted under the panel, pretty much out
of sight. No excuse for forgetting to think of it, I know. But a
"contributing factor". I did remember the accelerator pump at that moment
and decided to pump the throttle. Perhaps there was some fuel left in the
pump itself even though the float bowl was dry. I intended to close the
throttle before landing to make sure that I didn't get a burst of power at
the wrong moment.

I pumped the throttle and was immediately rewarded with engine power. It
sagged a bit, coughed a couple of times and then burst into full song. We
climbed without leaving the vicinity until I was sure that we could reach a
private field marked on the sectional another 5-6 miles further away. The
engine ran perfectly as we flew to the location; only to find the airport
had been turned into fenced ag fields. We had continued the climb somewhat
and decided to try to reach Helena, MT, then some 15 miles to the South. We
reached Helena without incident. The temperature there was over a hundred.
There was no FAA report necessary, as the emergency was terminated while
still airborne and without incident. Center, Approach and Tower staff were
concerned, professional and helpful. I called and thanked them all.

I'm sorry to be so long-winded about this, but you asked for details. Feel
free to criticize my plane or my actions, but try to be kind. I am not
trying to force you to abandon autogas or fly near roads. I'm just letting
you know what may happen if you persist in the belief that your airplane is
*immune* to vapor lock. Trust me in this, though. You don't ever want to
hear the person you love screaming and sobbing in fear. Never.

Rich S.

[Barnyard BOb --]

On Tue, 29 Jul 2003 07:48:35 -0700, "Rich S."
>> Anecdotally speaking....
>>
>> My GRAVITY fed RV3 has been totally immune to
>> vapor lock after logging more than 440 hours in it.
>> The vertical distance has remained less than 2 ft
>> for over 17 years.
>>
>> P.S.
>> Not yet sure certain what can be believed.
>>
>> P.P.S.
>> A greater 'fall' is certainly desirable.
>>
>> YMMV.
>>
>>
>> Barnyard BOb --
>
>The quality of autofuel dispensed at a strange FBO may vary as well. I
>prefer to buy from a known source and often test for alcohol content. The
>fuel which boiled in the Emeraude came from a really crappy looking
>tank/pump installation at the Pullman, WA airport. I have no idea if it was
>fresh - or last Winter's blend.
>
>Chances are that the Avgas is more consistent quality.
>
>I think you said your RV-3 has an electric fuel pump in the line. Does it
>also have a mechanical pump? Do the check valves in the pump(s) reduce the
>head pressure at the carburetor? Seems like a direct, gravity fed line with
>no restrictions or check valves would deliver a higher fuel flow.
>
>Rich S.
++++++++++++++++++++++++++++++++++++++++++++++

GRAVITY... and only GRAVITY.
No mechanical engine driven or electric boost pump
No fuel pressure gage, either

You're dead nuts on about 'restrictions'....
hampering a gravity only system.

I dare NOT install an electric pump directly in the line.
Van's sez it's OK to do that with an RV3 gravity system,
but I doubt if they have ever tried it for themselves. The
check valve restriction through the electric pump
combined with the puny 14 inch or so head is asking
for HUGE troubles with the boost pump off or failed, IMO.
At least with a half tank of fuel and high AOA, like...
at take-off trying to feed 60-80 of the 150 hungry horses?
[Remember we are only spinning at 2200 rpm, not 2700.]

What I have in mind is a PARALLEL path for an electric
boost pump...PREFERABLY without a check valve in
the system.

Think I can get away without one? <---<<<
Think CAREFULLY, before you answer.


Barnyard BOb -- engage brain before putting mouth into gear

[Rich S.]

"Barnyard BOb --" > wrote in message
...
>
> GRAVITY... and only GRAVITY.
> No mechanical engine driven or electric boost pump
> No fuel pressure gage, either
>
> You're dead nuts on about 'restrictions'....
> hampering a gravity only system.
>
> I dare NOT install an electric pump directly in the line.
> Van's sez it's OK to do that with an RV3 gravity system,
> but I doubt if they have ever tried it for themselves. The
> check valve restriction through the electric pump
> combined with the puny 14 inch or so head is asking
> for HUGE troubles with the boost pump off or failed, IMO.
> At least with a half tank of fuel and high AOA, like...
> at take-off trying to feed 60-80 of the 150 hungry horses?
> [Remember we are only spinning at 2200 rpm, not 2700.]
>
> What I have in mind is a PARALLEL path for an electric
> boost pump...PREFERABLY without a check valve in
> the system.
>
> Think I can get away without one? <---<<<
> Think CAREFULLY, before you answer.
>
>
> Barnyard BOb -- engage brain before putting mouth into gear

I have been mulling over several different questions regarding fuel system
plumbing in the last year or so - even up to the last resort of an extra one
gallon (or so) tank with a mechanical pump piped to the intake manifold
after the carb.

As for your concept, I think it would require a shutoff valve to keep the
electric pump from pumping in a circle. Unless the electric pump had
sufficient flow to create friction loss in the line leading back to the
tank, that is. I'd have to get out my tables for friction loss to figger
that one out. Used to be able to do it in my head with a fire engine roaring
next to me.

How about a solenoid operated valve tied to the electric pump switch?

Rich S.

[Morgans]

> the system.
>
> Think I can get away without one? <---<<<
> Think CAREFULLY, before you answer.
>
>
> Barnyard BOb -- engage brain before putting mouth into gear
>
BOb, I'm "Positive" you could get away without one. Me though, I would
want the 2nd and third way out! <g>

I got through my back surgery (fusion) so count on even more mistakes, now
that my fingers are stoned.
--
Jim in NC

[Dave Hyde]

Michael wrote:

> So prove me wrong. Show me a counterexample.

No quantitative data to back it up, so I'm sure
it won't meet your idea of a counterexample,
but a search of NTSB records shows a few
accidents with high wing gravity-feed systems
where vapor lock was suspected or reported,
and there was no other obvious mechanical
defect.

Dave 'Plan for the worst, accept better results' Hyde

[Michael]

"Rich S." > wrote
> I went back and re-read the entire thread and, you're right, I failed to
> identify my airplane and to describe the fuel system configuration.

[Long, careful, and complete description deleted] Thank you. As I
suspected, you have a system that I always knew COULD suffer from
vapor lock. Insufficient head pressure for reliable gravity feed, and
a pump inline, mounted on the engine and thus sucking fuel.

There's nothing inherently wrong with that - every design is a
compromise - but there is an awful lot of FUD associated with the
autogas vapor lock issue. I know people who have had vapor lock
problems. I also know lots of people who use autogas in high wing
Cessnas and high wing Pipers, and NONE of those people have EVER
experienced vapor lock - even when running autogas in high
temperatures while crossing the Rockies, as I have. Clearly this is a
design issue.

> Emeraude, powered with a Lycoming O-320-E3D and having a mechanical fuel
> pump on the engine. There is a Bendix electric fuel pump mounted on the
> engine side of the firewall, downstream of a gascolator.

I think these are the key points. Your pumps are in the engine
compartment, past the restrictions. Thus they are sucking fuel, not
pushing it, and are creating a point in your fuel system where the
pressure is lower than atmospheric ambient.

> There is a fuel pressure gauge teed in at the carburetor.

Given the system, I think that's a fine idea. Generally, you do not
see fuel pressure gauges on gravity-fed carbureted systems. Generally
you DO see them on pump-fed systems. It's worth considering WHY this
is.

> There are two 20 gallon fuel tanks, one located ahead of the instrument
> panel and the other behind the seat. The nose tank has about 15" of head
> above the carb inlet when the aircraft is level. There is a tank selector
> valve mounted on the left kick panel. The rear tank is almost level with the
> carb. The tank vents exit the bottom of the fuselage at 90° to the
> slipstream and received no pressure "boost" from it. I have no idea how much
> the restrictions in the fuel line (filters, check valves in the pumps,
> fittings, etc.) affect the head pressure or fuel flow.

A fuel filter (if it's an actual filter and not a screen) will cost
you about about a foor or two of head pressure. Not sure about the
check valves. The fittings are basically irrelevant.

Just FYI - these things can be calculated. There are published data.
A sophmore-level textbook of fluid mechanics for chemical or
mechanical engineers will contain all this information.

> On the day I experienced vapor lock and loss of power, the selector valve
> was set on the nose tank and it was at least 2/3 full, adding another 10" to
> the head distance. We were at 9,500' and the OAT was 85°. The electric pump
> was turned off in cruise and the fuel pressure gauge had been reading just
> above red line at ~2 lbs.

Just curious - is this normal for your installation? It seems very
low to me. In other words - it sounds like either your fuel filter
was clogged, or gas bubbles had already started to form in your fuel
system, causing pressure drop.

> I turned on the electric pump and switched to the rear tank. Nothing.

I find this unsurprising - unless the vapor lock was between the
electric pump and the mechanical one, there would be no effect from
'sucking harder' when your problem was vaporization of the fuel in the
line. Since you have carefully insulated the fuel lines inside teh
engine compartment, there is no reason to believe the gas bubbles
would form there.

> I admit that I had
> forgotten to try the manual prime pump.

I doubt strongly that it would have helped.

> I'm sorry to be so long-winded about this, but you asked for details.

And I'm glad you provided them. Especially details of the fuel
system.

> Feel free to criticize my plane or my actions, but try to be kind.

Actually, I think all the actions you took were very reasonable. My
experience and ratings are similar to yours (though I racked up my
1500 hours in a little over a decade, and some of them in gliders and
light twins) and I doubt I would have done anything differently.

As for your plane - I will make this comment. The fuel system you
have is very similar to what one might expect to see on older
certified light aircraft, with one significant difference. An older
aircraft is most likely not going to have a real fuel filter.
Instead, it's likely to have a gascolator with a settling bowl and a
fuel screen - what's often referred to as an elephant catcher. Adding
a REAL fuel filter does provide additional protection for the engine,
but this protection is not free.

If there's one thing I've learned from my years as an engineer, it's
that everything is a tradeoff. That fuel filter protects your engine
from dirt and sediment, but it is a major source of pressure drop.
Worse, the more necessary that fuel filter is (meaning the more
contamination in the fuel) the more pressure drop it causes. I
suspect that if you had a simple wire screen, you would not have had a
problem. But that's 20/20 hindsight.

> I'm just letting
> you know what may happen if you persist in the belief that your airplane is
> *immune* to vapor lock.

Actually, I no longer own that TriPacer. But I do believe that a
plane with a properly designed gravity fed fuel system is going to be
immune to vapor lock. I believe this based on the calculations
(posted elsewhere in this thread) and based on the field experience of
those who have been doing it.

I also believe that any plane with a suction-pump fuel system is at
risk for vapor lock. That doesn't mean we should not build such
planes (everything is a tradeoff!) but that we should be aware of the
issues.

To me, this is just one more issue where the design of the systems
makes a difference in what constitutes acceptable operation.

> Trust me in this, though. You don't ever want to
> hear the person you love screaming and sobbing in fear. Never.

I'll take your word for it.

Michael

[Bushy]

> I have been mulling over several different questions regarding fuel system
> plumbing in the last year or so - even up to the last resort of an extra
one
> gallon (or so) tank with a mechanical pump piped to the intake manifold
> after the carb.
>

Was a modification that was made to some aircraft in the hostile hills of
PNG at one time and known as the missionary fuel system.

A pump or shutoff valve to supply fuel equal to about 80% power into a jet
in the inlet manifold below the carby, so that if the carby jet blocked
there was a fuel option that might get one home..... Would require the carby
butterfly to be opened up to match and if the jet was partly blocked, the
fuel to the carby would be shut off manually to prevent flooding the motor.

A small reserve tank may also be a good idea to go with it.

Considering same as a backup to my aircraft when I build in a couple of
years. Not much weight penalty and the nice warm fuzzy feeling of an
emergency fuel backup system......

Hope this helps,
Peter

[Rich S.]

"Bushy" > wrote in message
...
> A small reserve tank may also be a good idea to go with it.
>
> Considering same as a backup to my aircraft when I build in a couple of
> years. Not much weight penalty and the nice warm fuzzy feeling of an
> emergency fuel backup system......
>
> Hope this helps,
> Peter

Peter.......

I remember as a teenager, sitting on the fender of a hot rod, trying to
dribble gas into the carb to get us home after a fuel pump went West.

Rich S.

[Ernest Christley]

Barnyard BOb -- wrote:
>
>>I remember as a teenager, sitting on the fender of a hot rod, trying to
>>dribble gas into the carb to get us home after a fuel pump went West.
>>
>>Rich S.
>
> ++++++++++++++++++++++++++++++++++++++++++++
>
> Rich,
> I once had a young cousin who did that.
> He was out of the hospital in less than 6 months....
> after major skin grafting and agonizing therapy.
>
> Seems the engine backfired and the gas stream then
> burned back to the jug he was holding over the carburetor.
>
> Youngsters destined to be firemen are a lucky lot? <g>
>
>
> Barnyard BOb - that which does not kill us makes us stronger?

He should have put the gas in a Windex bottle and stood back to squirt
it into the carb. I watched a guy show and engine to a potential buyer
while the engine sat in the middle of his yard using this technique.

Now, how do you hunker over the cowling to spray that bottle into the
carb while on downwind?

Maybe use a garden sprayer type system?

--
----Because I can----
http://www.ernest.isa-geek.org/
------------------------