 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
dan(at)rvproject.com
Guest
|
 Posted: Sat Feb 03, 2007 8:02 am Post subject: I've sworn off purge valve installations |
 |
|
FWIW:
I see 3.8 gph stable on the meter when purging (it goes up higher than that
at first and then comes down and stabilizes there). AFP recommends a
30-second purge. So for my setup that results in 0.032 gallons having
flowed through. That's 121ml or 0.19 lbs of fuel. Not much...but enough.
My math isn't good enough to figure out how much length of -6 (3/8" ID) fuel
tubing/hose that equates to. I'm sure somebody out there can figure it out.
But I suspect it's right around the same length as the run from the selector
valve up to and past the flow divider. Not much more than that, but that's
all ya need.
I'm really sorry to hear about your and your friend's issues related to the
purge valve. That really sucks, and I can understand why you're upset about
it. I just still think the concept of the purge valve is a great one, and
I'm keepin' mine!
I also would like to understand better why the AFP system has a
"designed-in" ICO leak. There has to be a good reason behind it, and I'm
sure Don Rivera can explain it better than anybody. It doesn't bother me
like it bothers some people, because I like & use the purge valve, and an
ICO leak is irrelevant to me. Still would like to understand it, though.
)_( Dan
RV-7 N714D
www.rvproject.com
---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
 |
Gary.A.Sobek
Joined: 09 Jan 2006
Posts: 217
Location: SoCAL USA
|
| Posted: Sat Feb 03, 2007 8:43 am Post subject: I've sworn off purge valve installations |
|
|
I am not an expert on fuel refining so someone who is should speak up. Fuel
Volatility, Fuel Vapor Pressure, Vapor Lock are all concerns I have in a
fuel injected aircraft engine.
Some info can be found at:
http://www.chevron.com/products/prodserv/fuels/bulletin/aviationfuel/8_ag_perf.shtm
Hot fuel vaporizes at a lower pressure. Vapor lock will occur with hot fuel
in the line being sucked from a fuel tank by only the hot engine mechanical
pump. It may run fine at run up power but quickly turn to vapor lock when
asked to provide takeoff power fuel flow.
Sit on a hot ramp in the sun for about an hour after flying to a HOT
location. Start up, taxi, run up, all go fine. On takeoff, vapor lock
occurs.
HOT fuel turns to vapor quicker. We locate our boost pump close to the tank
so that it does not need to SUCK and create more vapor. If the boost pump
fails or is not turned on, the HOT mechanical fuel pump has to ACT as a
vacuum pump to suck the fuel to the engine and makes it easier to vapor
lock. The FI system requires liquid fuel under pressure for the engine to
run.
A purge valve allows the operator to TEST the boost pump, move cooler fuel
into the lines, and lower the likelihood of the mechanical pump sucking so
hard that it creates vapors in the delivery line causing vapor lock and the
resulting engine failure on takeoff.
ECI FI system has continuous flow of fuel to the FI system and back to the
tank. The RSA type FI system used on most Lycomings does not.
30 seconds of fuel flow through the lines may only move a quart of fuel.
Not much to cause a large error in the fuel flow computer but it could be
enough to make sure that no vapor is in the line and could help make the
difference between the mechanical pump being able to SUCK liquid fuel at
takeoff power with an electrical boost pump failure.
Swearing off a purge valve is not a good excuse for not following good
installation practices. My paranoia about vapor lock on takeoff makes me
want to install a purge valve on any EXPERIMENTAL FI Aircraft that I fly.
Is the CHEAP FI HIGH Pressure boost pump part of the problem? Certificated
aircraft with the RSA type fuel injection does not use a purge valve. What
can WE in our EXPERIMENTAL FI aircraft do without using a purge valve to
prevent vapor lock on takeoff when a scenario like I list above occurs? I
agree that in most cases, less is more. Less parts, less cost, less
installation time, less to break, less to fix.
How do I prevent vapor lock on a HOT FI engine with an electric boost pump
failure, after sitting on a HOT RAMP for about one hour? Startup, taxi, run
up all go fine but the fuel flow stops during climb out? Lots of fuel in
the tanks but none in the FI hose and lines.
Is installing a SECOND electric boot pump needed when no purge valve exists
to insure that fuel gets to the working mechanical pump?
I do not see the purge valve as a fix all problem but just one possible
solution that should help LESSEN the possibility of vapor lock with only the
mechanical engine driven pump proving fuel to a FI engine on takeoff. It
only lessens the possibility of vapor lock with an electric boost pump
failure on takeoff as we replace hot fuel in the lines between the tanks and
engine with COOLER fuel from the tanks before startup. The purge valve
allows us to TEST the fuel delivery system on the ground before takeoff.
Only one fuel injection system available to our EXPERIMENTAL airplanes
includes a purge value as part of their fuel inject system. If they did not
include it, they could make more money by leaving it out and increasing
their profits. Other builders add their purge valve to their FI airplanes
for the reasons that I like the purge valve.
Gary A. Sobek
"My Sanity" RV-6 N157GS O-320 Hartzell,
1,977 + Flying Hours So. CA, USA
----Original Message Follows----
From: "kahuna" <mike.stewart(at)us.ibm.com>
Reply-To: rv-list(at)matronics.com
To: rv-list(at)matronics.com
Subject: Re: I've sworn off purge valve installations
Date: Sat, 3 Feb 2007 03:49:37 -0800
Gary.A.Sobek wrote:
> I know of one RV accident that totaled the airplane where the fuel
injected
> engine quit after takeoff. Post crash investigation sure looked like
VAPOR
> LOCK to me. If that airplane had a purge valve and was used before
> starting, there may be one additional RV flying today.
>
> I agree that a FI system should not need a purge valve to SHUT OFF the
> engine but one fuel injector manufacturer made his servo require one.
>
> Gary A. Sobek
> "My Sanity" RV-6 N157GS O-320 Hartzell,
> 1,977 + Flying Hours So. CA, USA
>
>
Gary I do not see how this is a possible senerio argue purge to the AFP
system. Here is why.
THere are many opportunities for vapor lock. The AFP purge vaule is mounted
right before the spider. If used per the manual, you purge for a few seconds
and start. Now if a guy has not used the purge valve, starts, taxis, and
takes off, he has already run for minutes and done way more by running than
the purge valve ever did. Running the purge valve, with boost on, will only
dribble fuel since the meter device is not getting air flow. Im not sure
what the flow is, Id guess ~ 1gph. So if you run the purge for 20 seconds
you have moved some miniscule amount of fresh fuel into the lines. Which is
fine since you dont need much movement in the injection lines to purge
vapor. If you run your engine at take off power for even a few seconds you
have blasted fresh fuel into the system at an order of magnatude greater
than 1gph. In an IO360 for example. One second of take off power is worth
~20 seconds of purge, at least in terms of fuel flow of fresh fuel. And Ill
bet the number is s!
everal times that. Im only guessing at the purge fuel flow. The only
design senerio Im aware of for the purge is to help with vapor lock starts,
not vapor lock while airborn. You will have to convince me that operating a
purge valve on the ground would have prevented your accident senerio.
Also Im with the others, whats the point of ICO still delivering fuel? I
have over 2k AFP hours in multiple planes, and I dont use the purge for
anything.
Talk to me Gary
Mike
PS Smoozer is doing well and mentioned your help
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=92538#92538
_________________________________________________________________
Check out all that glitters with the MSN Entertainment Guide to the Academy
Awards® http://movies.msn.com/movies/oscars2007/?icid=ncoscartagline2
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
lifeofreiley2003(at)yahoo
Guest
|
| Posted: Sat Feb 03, 2007 8:49 am Post subject: I've sworn off purge valve installations |
|
|
In you post back to Gary you refer to carb ice, I
guess its new info to me... carb icing on a fuel
injected engine?
Oh well... 
Darrell
--- linn Walters <pitts_pilot(at)bellsouth.net> wrote:
| Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs 
do not archive
Darrell Reiley wrote:
>
<lifeofreiley2003(at)yahoo.com>
>
>Linn,
>
>I believe Gary stated the plane was 'fuel
injected".
>
>Darrell
>
>do not archive
>
>
>--- linn Walters <pitts_pilot(at)bellsouth.net> wrote:
>
>
>
>>
>><pitts_pilot(at)bellsouth.net>
>>
>>RV6 Flyer wrote:
>>
>>
>>
>>>
>>>
>>>
>><rv6_flyer(at)hotmail.com>
>>
>>
>>>I know of one RV accident that totaled the
>>>
>>>
>>airplane where the fuel
>>
>>
>>>injected engine quit after takeoff. Post crash
>>>
>>>
>>investigation sure
>>
>>
>>>looked like VAPOR LOCK to me.
>>>
>>>
>>Hmmm. The engine started, ran long enough to taxi
>>to the runway, some
>>full-power takeoff and short flight ..... explain
to
>>me how that could
>>be caused by vapor lock??? How did it look like
>>vapor lock????
>>
>>I would be more inclined to believe excessive
water
>>in the fuel (did the
>>plane sit outside in a lot of rain before flying,
>>have leaking fuel caps
>>to allow the water in, and the pilot didn't sump
the
>>tanks??? Not
>>likely, but stupid pilot tricks do happen.) or
carb
>>ice or ..... almost
>>anything but vapor lock.
>>Linn
>>do not archive.
>>
>>
>>
>>> If that airplane had a purge valve and was used
>>>
>>>
>>before starting,
>>
>>
>>>there may be one additional RV flying today.
>>>
>>>I agree that a FI system should not need a purge
>>>
>>>
>>valve to SHUT OFF the
>>
>>
>>>engine but one fuel injector manufacturer made
his
>>>
>>>
>>servo require one.
>>
>>
>>>Gary A. Sobek
>>>"My Sanity" RV-6 N157GS O-320 Hartzell,
>>>1,977 + Flying Hours So. CA, USA
>>>
>>>
>>>
>>>
>>>----Original Message Follows----
>>>From: "kahuna" <mike.stewart(at)us.ibm.com>
>>>Reply-To: rv-list(at)matronics.com
>>>To: rv-list(at)matronics.com
>>>Subject: Re: I've sworn off purge valve
>>>
>>>
>>installations
>>
>>
>>>Date: Fri, 2 Feb 2007 16:32:21 -0800
>>>
>>>
>>>
>>>
>><mike.stewart(at)us.ibm.com>
>>
>>
>>>[quote="gerf(at)gerf.com"]So ... at the risk of
>>>
>>>
>>starting a war ... if
>>
>>
>>>I left the cotter pins out of my flap mounting
>>>
>>>
>>bolts and a flap fell
>>
>>
>>>off, should I conclude that the flaps are too
much
>>>
>>>
>>trouble or should I
>>
>>
>>>chastise myself for forgetting to install the
>>>
>>>
>>cotter pins ?
>>
>>
>>>Sorry, but I question your conclusion that purge
>>>
>>>
>>valves have no place
>>
>>
>>>on an RV.
>>>
>>>g
>>>
>>>
>>>
>>>
>>>>--
>>>>
>>>>
>>>The flaps serve a very useful purpose. One that
>>>
>>>
>>can be demonstrated
>>
>>
>>>and quantified. I say the purge vavle can do
>>>
>>>
>>neither of these. As for
>>
>>
>>>the servo not being at idle cut with fuel flow,
>>>
>>>
>>that can be fixed.
>>
>>
>>>Mike
>>>
>>>
>>>
>>>
_________________________________________________________________
>
>
>>>Turn searches into helpful donations. Make your
>>>
>>>
>>search count.
>>
>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>browse
>>Subscriptions page,
>>FAQ,
>>
>>Web Forums!
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>Finding fabulous fares is fun.
>Let Yahoo! FareChase search your favorite travel
sites to find flight and hotel bargains.
>http://farechase.yahoo.com/promo-generic-14795097
>
>
>
>
>
>
|
Looking for earth-friendly autos?
Browse Top Cars by "Green Rating" at Yahoo! Autos' Green Center.
http://autos.yahoo.com/green_center/
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
pitts_pilot(at)bellsouth.
Guest
|
| Posted: Sat Feb 03, 2007 10:26 am Post subject: I've sworn off purge valve installations |
|
|
Good catch Darrell .... I was on a roll and let my fingers do the talking. :-[
My apologies.
You're right about carb icing not being a problem in FI engines. It isn't in my PS5 carb either.
I trust you guys to keep me in line!!!
Linn
do not archive
Darrell Reiley wrote:
[quote] | Quote: | --> RV-List message posted by: Darrell Reiley <lifeofreiley2003(at)yahoo.com> (lifeofreiley2003(at)yahoo.com)
In you post back to Gary you refer to carb ice, I
guess its new info to me... carb icing on a fuel
injected engine?
Oh well...
Darrell
--- linn Walters <pitts_pilot(at)bellsouth.net> (pitts_pilot(at)bellsouth.net) wrote:
| Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
| Quote: | --> RV-List message posted by: Darrell Reiley
|
<lifeofreiley2003(at)yahoo.com> (lifeofreiley2003(at)yahoo.com)
| Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
injected".
| Quote: | Darrell
do not archive
--- linn Walters <pitts_pilot(at)bellsouth.net> (pitts_pilot(at)bellsouth.net) wrote:
| Quote: | --> RV-List message posted by: linn Walters
<pitts_pilot(at)bellsouth.net> (pitts_pilot(at)bellsouth.net)
RV6 Flyer wrote:
| Quote: | --> RV-List message posted by: "RV6 Flyer"
|
<rv6_flyer(at)hotmail.com> (rv6_flyer(at)hotmail.com)
| Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
0 And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
1 | Quote: | | Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
2 And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
3 | Quote: | | Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
4 And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
5 |
And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
6 | Quote: | | Quote: | | Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
7 |
And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
8 | Quote: | | Quote: | | Quote: | And your point is???? I have a problem when, in the
absence of any
clear data, a malfunction is attributed to 'vapor
lock'. I've put up
with all the rhetoric for a lot of years running
auto fuel ..... in FL,
on hot days, with both injected and carb'd engines
(yep, run auto fuel
through the injected engine too ..... but not near
as much as through a
carb) with nary a hiccup. Not even any more hard
starting problems than
using 100LL. I guess the statement 'looked like
vapor lock to me' just
rubbed me the wrong way. Sorry. I really would
rather have statements
backed up by data or first-person-experience, not
(to seal a line from a
song) 'I heard it from a friend, who, heard it from
a friend, who .... '.
The point I tried to make (and failed, I guess) is
that all that engine
running after startup should have purged any
heat-soaked fuel. Once the
heat soaked fuel is gone (from the firewall
forward), the possibility of
vapor lock goes way down ......
Linn ...... calmed down without the drugs
do not archive
Darrell Reiley wrote:
|
9 |
--> RV-List message posted by: Darrell Reiley
|
0 | Quote: | | Quote: | | Quote: | --> RV-List message posted by: Darrell Reiley
|
1 |
--> RV-List message posted by: Darrell Reiley
|
2 | Quote: | | Quote: | | Quote: | --> RV-List message posted by: Darrell Reiley
|
3 | Quote: | | Quote: | --> RV-List message posted by: Darrell Reiley
|
4 --> RV-List message posted by: Darrell Reiley
|
5 | Quote: | | Quote: | --> RV-List message posted by: Darrell Reiley
|
6 --> RV-List message posted by: Darrell Reiley
|
7 | Quote: | | Quote: | --> RV-List message posted by: Darrell Reiley
|
8 |
|
--> RV-List message posted by: Darrell Reiley
|
9 | Quote: | | Quote: | 1 3 5 7 9 | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
0 |
|
Linn,
I believe Gary stated the plane was 'fuel
|
1 | Quote: | | Quote: | | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
2 Linn,
I believe Gary stated the plane was 'fuel
|
3 | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
4 Linn,
I believe Gary stated the plane was 'fuel
|
5 | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
6 Linn,
I believe Gary stated the plane was 'fuel
|
7 | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
8 | Quote: | | Quote: | Linn,
I believe Gary stated the plane was 'fuel
|
9 injected".
|
0 injected".
|
1 3 5 |
injected".
|
7 4 6 Darrell
do not archive
--- linn Walters <pitts_pilot(at)bellsouth.net> (pitts_pilot(at)bellsouth.net) wrote:
|
7 [b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
charlieray(at)optonline.n
Guest
|
| Posted: Sat Feb 03, 2007 10:39 am Post subject: I've sworn off purge valve installations |
|
|
Its called throttle Ice and happens on the back side of the trottle plate,
it happens no mater if you have a carb or throttle body. Its just less
severe for an injected engine, the venturi is the real problem area for
carb ice, not necessarily throttle ice.
---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
lifeofreiley2003(at)yahoo
Guest
|
| Posted: Sat Feb 03, 2007 11:15 am Post subject: I've sworn off purge valve installations |
|
|
I this common? This is the first I've heard of this?
(on fuel injection)
Darrell
do not archive
--- Charles Reiche <charlieray(at)optonline.net> wrote:
[quote]
<charlieray(at)optonline.net>
Its called throttle Ice and happens on the back side
of the trottle plate,
it happens no mater if you have a carb or throttle
body. Its just less
severe for an injected engine, the venturi is the
real problem area for
carb ice, not necessarily throttle ice.
---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
dan(at)rvproject.com
Guest
|
| Posted: Mon Feb 05, 2007 4:26 pm Post subject: I've sworn off purge valve installations |
|
|
RV listers,
Don Rivera from Airflow Performance (AFP) responded off-list to my previous
inquiry, asking about the rationale for having a designed-in ICO leak. I
don't know too many manufacturers who take the time to address concerns &
questions in such detail. What follows is his response. I have his
permission to post it where required, and I felt this forum would benefit
from this in-depth explanation of the design's history.
======= BEGIN Don's Response =======
Dan,
It saddens me to hear of incidents let alone ones that are strictly the
cause of poor judgment, practice, attention; you know what I mean. It seems
that Michael Stewart has his opinion and that's fine, but to spout off like
he does, is kind of up setting, as he seems to sensationalize events that
are strictly in his control.
You had made comment that you wanted to know more about the mixture control
valve design. To completely understand the reasoning behind this design you
have to know a little history of how this all got started. When we started
our company in 1984 I had already 10 years experience with aircraft fuel
injection systems at the Bendix Corporation. Being the under study of the
inventor of the RS and RSA fuel injection system and later being the project
engineer on that product line gave me insight into the manufacturing
problems and cost associated the RSA design. In Airflow's infancy, we knew
that we would have to design a system to satisfy a large range of horsepower
requirements with a minimum of part and tooling changes. Knowing that we
wanted to be able to run engines from around 80 HP to 1000 HP we designed
the present fuel regulator concept.
Studying the needs in the aviation field we constantly heard of the big draw
back to fuel injection was 1) initial cost, 2) hot starts, 3) high cost of
overhaul. In this design we determined that eliminating part count without
sacrificing performance would help with manufacturing costs, and overhaul
cost.
Studying various manufacturing techniques, we knew that plate valves were
expensive to make (high part count) were susceptible to scoring unless you
used some expensive materials and there's always the issue of making the
parts flat (specialized equipment). Rotary valves on the other hand were
easy to control in manufacture (OD grinding) and round bores were easy to
control with honing. This would allow parts that would not have to be hand
lapped or fitted. The round parts could be made with tight enough
tolerances that matched parts were not necessary. Having a through bore
that both idle and mixture valves ran in gave the bonus of getting cost out
of manufacturing as through bore honing would hold the bore straight and we
could easily hold + .0005" on the entire bore. Brass was chosen as the
material to run in an anodized honed bore. Designing the L/D of the valve
gave excellent bearing surface and I have to admit, we really haven't had
any problems with wear or scoring of these parts in 20+ years of service.
The only down side is continued actuation of the parts when dry can cause
galling of the valve. This is solved by oil flushing the parts after test,
and in service the parts are always in fuel. Of course with a rotary valve
there has to be clearance for the valve to rotate, therefore ICO cannot be 0
leak. We also only shut off the metered side of the circuit in the
regulator. This removed the additional parts required to mechanize an
additional valve to shut off this side of the circuit and since the decision
was made to use the purge valve as standard equipment, a zero leak mixture
valve was not required.
Hot starts were a common problem with low-pressure non-returning fuel
injection systems, and even some early mechanical automotive fuel injection
like the Bosch K Jetronic suffered from this problem. We determined that
the hot start problem was due to heat soak on the fuel system components on
the engine. Since fuel boiled at around 130 degrees F at sea level
pressure, after the engine shut down the fuel on the engine side of the fire
wall in the hoses, engine driven fuel pump, fuel control, flow divider, and
nozzle lines would be partially boiled away. Since the fuel metering system
was non-returning, there was no way to get rid of the hot fuel and vapor.
You had to start the engine flooded or when the engine started you had to
run it up excessively to pass the vapor through the metering system to keep
the engine running. Some people didn't have problems with this technique,
many did. The components that held the most volume of fuel were the
culprits. The #6 fuel hoses, the engine driven fuel pump and the fuel
control. Since our metering system metered fuel to the engine based on
engine airflow consumption there was a limit on how fast fuel would transfer
through the system when the engine was not running. On a typical 4 cylinder
Lycoming the normal calibration set up allowed about 1 cup of fuel to
transfer through the system in 45 seconds of purging with the throttle wide
open. This would pretty much exchange the fuel in the engine driven fuel
pump and the fuel control and hoses. At idle the fuel transfer would be
.038 cup of fuel in one minute. This is why idling the engine will never
get the air out of the system, well at least not for 26 minutes. This is
another reason we want to minimize the volume of fuel on the engine side of
the firewall.
The purge valve was designed on the premise that cleaning out the hot fuel
and vapor from the engine driven pump, fuel control and hoses would cure the
hot start problem. The first system was installed on an IGSO 480 in an
aerobatic airplane, which was pretty much unstartable when hot. The system
worked quite well with pretty much the same start routine hot or cold. Also
the benefit with the purge valve was that it would dump the fuel pressure
when the engine was shut off to keep fuel from bleeding into the engine
after shut down. This was a problem with engines using diaphragm fuel
pumps. We always had complaints of fuel dripping into the air box after
shut down on Bendix servos which basically dead head the fuel pump pressure
against a plate valve. When the plate valve scored a little leakage started
and the engine would not shut down clean. People whine and moan about this
now, but 30 years ago when I was working at Bendix we heard the same thing.
Thus, another reason for the design of the purge valve.
The purge valve design was not something we designed from scratch with a
fresh sheet of paper. The basic valve design was studied as to what design
in the field gave the most trouble free service. Looking at helicopter
service, we found that that seemed to get the most abuse. From both a
vibration and wear stand point this installation typically had fuel tanks
above the engine so the valve had to be near zero leak as possible, yet be
robust enough to withstand the harsh environment it was in. So the valve
bushing was used from a RSA-7 fuel regulator. This same design had been
used on all Hughes 300 and Beechcraft Baron 58P installations. With a few
million flight hours accumulated, there had been not one incident of
malfunction of the valve, let alone the screw backing out because it was not
lockwired. The idle valve bushing on these fuel servos had the same design,
that is, being held in by one screw. Thus the Airflow purge valve was
designed to mimic the Bendix design, with some minor changes in the venting
of the ports in the bushing, and of course a housing was designed to hold
the valve.
So there you have it. A history and reasoning behind the mixture control
and purge valve design. This design was done to satisfy requirements that
we determined customers wanted in the field. After all, if the status quo
was accepted, why build anything? It would not address any of the issues
that existed, and you would end up with a clone of the same 40-year-old
design. Kind of like a Silver Hawk. All of these parts were designed for a
reason and with lot of forethought. Are there other ways to do it? You
bet. Is there a better cost effective way to address the problems
associated with low-pressure non-returning fuel injection systems? Probably
not, with the market as it is today.
======= END Don's Response =======
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
pitts_pilot(at)bellsouth.
Guest
|
| Posted: Mon Feb 05, 2007 6:45 pm Post subject: I've sworn off purge valve installations |
|
|
Great response!!! Thanks Dan & Don! This is the education I was
looking for. I've saved the email so that I can revisit it when the
time comes to decide what I'm going to do with my installation. This
email should put some of the urban legend stuff to bed.
In all my dealings with engines over the years, I learned that there are
methods of starting an engine that woprk, and those that don't. I
developed a great set of abs and stomach muscles learning to prop my
Pitts ..... unfortunately, I learned to prop it the easy way!
Again, thanks to Dan & Don.
Linn
do not archive
Dan Checkoway wrote:
| Quote: |
RV listers,
Don Rivera from Airflow Performance (AFP) responded off-list to my
previous inquiry, asking about the rationale for having a designed-in
ICO leak. I don't know too many manufacturers who take the time to
address concerns & questions in such detail. What follows is his
response. I have his permission to post it where required, and I felt
this forum would benefit from this in-depth explanation of the
design's history.
|
snip
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
kahuna
Joined: 02 Feb 2007
Posts: 93
|
| Posted: Tue Feb 06, 2007 5:41 am Post subject: I've sworn off purge valve installations |
|
|
Hmm. Spout off? Sensationalize? That's interesting. I have been bringing
my experience to the table in an effort to educate the users. Yes, I did
not safety wire the screws, neither did the off field failure. I have
received 2 listers off messages that they read these posts and also
found their screws now safety wired. Im not here to spout off. Im here
to learn, engage in useful dialogue, and educate where I can based on my
experience.
Im not an AFP basher. Dons a bright guy with an excellent product, one
that I use on my plane.
I would respectfully recommend that he find a way to ship the valve with
the screws safety'd already, like the rest of his system. The flow
divider and fuel servo both come all wired up and ready to bolt on, but
not the purge valve. Leaving this up to the installer can lead to a
failure to do so. With many things on an airplane, this cant be avoided.
But with this purge valve, I think it can be done simply. How many
accidents do we need before it changes from dumb user error, to design
change? Giving the user a chance to fail, where it can be avoided, does
not sound like good practice.
Just my 2 cents.
Best,
Mie
--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
gerf(at)gerf.com
Guest
|
| Posted: Tue Feb 06, 2007 7:37 am Post subject: I've sworn off purge valve installations |
|
|
Excellent info ... I'd bet there'd be a lot of interest if Don put together a talk on the system ... there's got to be a fair sized number of installations out there at this point ...
g
>--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
dan(at)rvproject.com
Guest
|
| Posted: Tue Feb 06, 2007 8:23 am Post subject: I've sworn off purge valve installations |
|
|
Pretty sure Don actually used to offer "Fuel Injection 101" classes. The http://www.airflowperformance.com web site has an online thing for it, but I coulda sworn he held occasional weekend classes at their facility in the past. Don't quote me on that...
do not archive
)_( Dan
[quote] ---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
gerf(at)gerf.com
Guest
|
| Posted: Tue Feb 06, 2007 10:02 am Post subject: I've sworn off purge valve installations |
|
|
Looks like there's a class beginning of March and November ... hmm, March isn't going to be doable for me ...
g
[quote]--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
Don
Joined: 18 Jan 2006
Posts: 13
|
| Posted: Tue Feb 06, 2007 11:43 am Post subject: Re: I've sworn off purge valve installations |
|
|
Please Michael, do not take this as being disrespectful or as an insult to your intelligence. But I feel that the record must be corrected here. I am hopefully not coming off as arrogant but will only list the facts here. First off Airflow Performance sells a complete Fuel Injection kit for installation on RV aircraft. In that kit the purge valve and flow divider come as an assembly; flow tested pressure tested, lock wired and oil flushed. We have process sheets that control the assembly process, and the lock wire sign off is part of that sheet. I believe if you look back on your build record for the RV-6A there are pictures of the purge valve flow divider assembly bolted to the engine. It clearly shows the assembly lock wired. There are instances that customers want to install our purge valve on other fuel-injected installation not using Airflow Performance equipment; this is the customer’s choice. In this case the customer is responsible for fabricating their own brackets and mounting hardware. The purge valve has mounting holes for brackets on the housing, there is a tag, which says “LOCK WIRE THIS SCREW”, on the purge valve stop screw warning to lock wire the screw after assembly and the installation, and operation manual has the following warnings in it:
In the manual supplied with the purge valve:
. “……….Lock wire all hard ware. Make sure to lock wire the stop screw.”
In the Appendix in the manual:
“WARNING
Failure to lock wire the stop screw holding the purge valve in the housing, will result in immediate engine stoppage if the screw backs out.”
Again here, as stated in the Installation and Service Manual Rev.E:
“OPERATION OF THE INSTALLED SYSTEM
2-2. There are many factors affecting satisfactory fuel injection operation in service, which cannot be addressed regarding the design of the fuel controller alone. A recognition of these requirements regarding fuel tanks, fuel lines, fuel pumps, fuel pressure requirements, controls, air induction inlet, intake manifold design, and the operation and maneuvers the aircraft will be subjected to, must be evaluated if the fuel injection system is to function successfully in the airplane. It is up to the owner/installer to use proper and approved aircraft installation and fabrication techniques. Airflow Performance recommends using AC-4313-2B as a guide for approved methods and techniques for installing components on aircraft installations.”
I don’t know what else we can do to insure that proper installation and maintenance techniques are used. You are, after all, building an “Experimental Aircraft” there is no type certificate, which controls the components installed on the aircraft. That’s the beauty of this category. But of course this puts more responsibility on the builder.
Michael, you stated:
“I would respectfully recommend that he find a way to ship the valve with the screws safety'd already, like the rest of his system. The flow divider and fuel servo both come all wired up and ready to bolt on, but not the purge valve. Leaving this up to the installer can lead to a failure to do so. With many things on an airplane, this cant be avoided. But with this purge valve, I think it can be done simply. How many accidents do we need before it changes from dumb user error, to design change? Giving the user a chance to fail, where it can be avoided, does not sound like good practice.”
Well, to answer the first part of your statement, the assembly in the kit is lock wired. To the second part of the statement, I believe we have to the best of our ability informed the customer of the need to lock wire the stop screw. And in some of the instances when the factory installed lock wire was removed for one reason or another it was not reinstalled. Hopefully the person removing this lock wire had enough presence of mind to re-lock wire parts that he/she disassembles and reassembled. It’s not any different than lock wiring oil filters, oil drain plugs, propeller bolts, making sure the spark plugs are torqued and your seat belts and harness are on when you take off. It’s all about the details.
But, if you take the analogy further, maybe the experimental kit market should not sell kits that have to be assembled. Is the RV-nose gear in need of design change, if it would fail if you hit a pothole? Should the control stick in an aircraft be welded in instead of bolted in the event the bolt would fall out or is not installed? (This has happened). Should there be cotter pins on the nut that holds the throttle lever on the fuel injector throttle shaft or should there be a lock nut? The cotter pin could not be installed or the lock nut could have no running torque. The debate goes on and on. I guess what I’m saying here is yes we the manufactures are responsible to have sound engineering behind their products. Since this is an experimental category, you as the builder have the right to assemble, modify or do whatever. Where I have a problem is when people disregard the proven track record of a product, with millions of flight hours accumulated, to say that the design is defective or needs to have a design change because the original design intent has not been met or the device has been used, abused or incorrect maintenance practices have been used. All of us operating experimental aircraft, myself included have the responsibility to insure to the best of our ability that our aircraft are safe to fly. Doing your own maintenance, modifications or for that matter building your own flying machine is highly rewarding and an accomplishment not taken lightly. Let’s face it. Flying is dangerous, but we need to evaluate the risks and be responsible to operate the aircraft in a safe, legal manner. This was the basis of the experimental movement when I got involved back in the 1960’s. Experimental aircraft give us a lot of freedom; one way to be able to exercise that freedom is to be responsible.
I need to get off the soapbox.
Yes Dan we are having Fuel Injection 101 classes at our facility the 2007 dates are March 2-4 and November 2-4.
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
klwerner(at)comcast.net
Guest
|
| Posted: Tue Feb 06, 2007 12:32 pm Post subject: I've sworn off purge valve installations |
|
|
Mr. Don Rivera,
Both you and I probably agree that Air Flow Performance builds probably one of the best ( if not THE best ) Fuel Injection Systems on the experimental market today.
Personally, I actually do like the idea of a manually controlled Purge Valve for its various reasons. Shutting off an engine via the Purge Valve or via Mixture cutoff is like six of one, half a dozen of another as far as I am concerned. But not everyone may think this way. Well, to each experimenter his/her own, but I sure do think your system is very versatile.
That said, I'd like to add that I am not even a customer of AFP just yet, nor do I have a financial or any other interest in AFP for sharing my thoughts on my understanding of the system.
However I would not mind getting 50% off when the time cometh to place an order! Please keep this in mind...
Sincerely,
Konrad
Do not archive
[quote][b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
rvbuilder(at)sausen.net
Guest
|
| Posted: Tue Feb 06, 2007 1:32 pm Post subject: I've sworn off purge valve installations |
|
|
Just as a data point, I can confirm that my FM-300 is sitting in its box with the safety wires all in place.
Michael Sausen
-10 #352 Limbo
--
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
kahuna
Joined: 02 Feb 2007
Posts: 93
|
| Posted: Wed Feb 07, 2007 4:18 am Post subject: Purge valve design |
|
|
Subject changed.
For those that dont know what we are talking about, here is a picture of one.
Hi Don,
THanks for coming to the list to share your thoughts. You have provided us with some great insight into your design. No disrespect taken here. Ive been a member of this list for 12 years. No one survives here without leaving their egos at the door. I hope that you will continue to provide your experience here and share your thoughts. THere are many smart people here, more than I could count. And while there is often a lot of useless rhetoric, there are also many posts that actually save lives. That Im sure of. So if you have a few minutes, lets look at the design of the purge valve and some design goals. Lets start from some common ground.
Like you, I am also responsible for the design and implementation of some complicated devices. Some of which have hundreds of man years of development. Some of our gismos are used in the battle field where lives are at risk, so from that perspective we both make things that have high risk implementations. But no matter how hard my team may work, we still provide the opportunity for our customers to get themselves into weeds, so to speak. And when they do, we have violated our prime directive. THat being, "thou shall not let the customer get into the weeds." Cause when that happens, no one wins no matter the reason. And when they do, we ask ourselves, "how'd we let them do that?"
Clearly the purge valve provides some very useful benefits. You have taken great care to "box it up" so to speak so that the customer can bolt it on. But you also admit that some installations require customers to crack the box open for a particular installation, requiring them to take positive steps to seal the box up. This is clearly an opportunity for failure. Several that Im aware of. IF a customer has to break the safety wire to install, then they are required to safety it back. If they dont, then there is a strong possibility they can get themselves into the weeds. I would be interested in knowing from how how many you are aware of. And when a customer ends up on his back with his kid in the back seat (N360WS), do you really want to tell him, "Hey your in an experimental and you didnt read the directions. Sorry there is nothing I can do. Ive done all I can." I know you don't. And when a customer ends up in the weeds, has the product failed to meet a design goal? I think it has. Whether or not there is anything you can do is what Id like for you to consider. Is there another way? Can you take into consideration all the potential installation options and still keep your customer from ending up in the weeds with this screw stop?
I believe the design issue may be that the set screw is required to be safety wired by the installer in some installations. Many customers unmount the valve from the bracket and break your seal. Could the screw stop be locktighted in place? Is there any reason why any installation would resuire the user to remove this screw? Could a small through hole be drilled through the black retaining plate near the screw and safety wired where no installation would required the user to break it? Another tab near by? I dont know. Seems worthy of consideration. What are your thoughts here Don?
We can agree that you have a great product, one that has years of design engineering built in. We can also agree that customers do dumb things. I know cause Im one of em. This is not the first mistake Ive made on my plane and it wont be the last. But would you consider my ideas above and provide yout thoughts for this dumb customer. Cause even if I never get it Don, someone will. You just might save a life.
Thanks
Mike
| Don wrote: | Please Michael, do not take this as being disrespectful or as an insult to your intelligence. But I feel that the record must be corrected here. I am hopefully not coming off as arrogant but will only list the facts here. First off Airflow Performance sells a complete Fuel Injection kit for installation on RV aircraft. In that kit the purge valve and flow divider come as an assembly; flow tested pressure tested, lock wired and oil flushed. We have process sheets that control the assembly process, and the lock wire sign off is part of that sheet. I believe if you look back on your build record for the RV-6A there are pictures of the purge valve flow divider assembly bolted to the engine. It clearly shows the assembly lock wired. There are instances that customers want to install our purge valve on other fuel-injected installation not using Airflow Performance equipment; this is the customer’s choice. In this case the customer is responsible for fabricating their own brackets and mounting hardware. The purge valve has mounting holes for brackets on the housing, there is a tag, which says “LOCK WIRE THIS SCREW”, on the purge valve stop screw warning to lock wire the screw after assembly and the installation, and operation manual has the following warnings in it:
In the manual supplied with the purge valve:
. “……….Lock wire all hard ware. Make sure to lock wire the stop screw.”
In the Appendix in the manual:
“WARNING
Failure to lock wire the stop screw holding the purge valve in the housing, will result in immediate engine stoppage if the screw backs out.”
Again here, as stated in the Installation and Service Manual Rev.E:
“OPERATION OF THE INSTALLED SYSTEM
2-2. There are many factors affecting satisfactory fuel injection operation in service, which cannot be addressed regarding the design of the fuel controller alone. A recognition of these requirements regarding fuel tanks, fuel lines, fuel pumps, fuel pressure requirements, controls, air induction inlet, intake manifold design, and the operation and maneuvers the aircraft will be subjected to, must be evaluated if the fuel injection system is to function successfully in the airplane. It is up to the owner/installer to use proper and approved aircraft installation and fabrication techniques. Airflow Performance recommends using AC-4313-2B as a guide for approved methods and techniques for installing components on aircraft installations.”
I don’t know what else we can do to insure that proper installation and maintenance techniques are used. You are, after all, building an “Experimental Aircraft” there is no type certificate, which controls the components installed on the aircraft. That’s the beauty of this category. But of course this puts more responsibility on the builder.
Michael, you stated:
“I would respectfully recommend that he find a way to ship the valve with the screws safety'd already, like the rest of his system. The flow divider and fuel servo both come all wired up and ready to bolt on, but not the purge valve. Leaving this up to the installer can lead to a failure to do so. With many things on an airplane, this cant be avoided. But with this purge valve, I think it can be done simply. How many accidents do we need before it changes from dumb user error, to design change? Giving the user a chance to fail, where it can be avoided, does not sound like good practice.”
Well, to answer the first part of your statement, the assembly in the kit is lock wired. To the second part of the statement, I believe we have to the best of our ability informed the customer of the need to lock wire the stop screw. And in some of the instances when the factory installed lock wire was removed for one reason or another it was not reinstalled. Hopefully the person removing this lock wire had enough presence of mind to re-lock wire parts that he/she disassembles and reassembled. It’s not any different than lock wiring oil filters, oil drain plugs, propeller bolts, making sure the spark plugs are torqued and your seat belts and harness are on when you take off. It’s all about the details.
But, if you take the analogy further, maybe the experimental kit market should not sell kits that have to be assembled. Is the RV-nose gear in need of design change, if it would fail if you hit a pothole? Should the control stick in an aircraft be welded in instead of bolted in the event the bolt would fall out or is not installed? (This has happened). Should there be cotter pins on the nut that holds the throttle lever on the fuel injector throttle shaft or should there be a lock nut? The cotter pin could not be installed or the lock nut could have no running torque. The debate goes on and on. I guess what I’m saying here is yes we the manufactures are responsible to have sound engineering behind their products. Since this is an experimental category, you as the builder have the right to assemble, modify or do whatever. Where I have a problem is when people disregard the proven track record of a product, with millions of flight hours accumulated, to say that the design is defective or needs to have a design change because the original design intent has not been met or the device has been used, abused or incorrect maintenance practices have been used. All of us operating experimental aircraft, myself included have the responsibility to insure to the best of our ability that our aircraft are safe to fly. Doing your own maintenance, modifications or for that matter building your own flying machine is highly rewarding and an accomplishment not taken lightly. Let’s face it. Flying is dangerous, but we need to evaluate the risks and be responsible to operate the aircraft in a safe, legal manner. This was the basis of the experimental movement when I got involved back in the 1960’s. Experimental aircraft give us a lot of freedom; one way to be able to exercise that freedom is to be responsible.
I need to get off the soapbox.
Yes Dan we are having Fuel Injection 101 classes at our facility the 2007 dates are March 2-4 and November 2-4. |
[img][/img][img][/img]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
ronschreck
Joined: 04 Aug 2006
Posts: 192
Location: Gold Hill Airpark, NC (NC25)
|
| Posted: Wed Feb 07, 2007 7:38 am Post subject: I've sworn off purge valve installations |
|
|
I believe Dan is still offering the classes. I flew my RV-8 to Airflow Performance last year and had Don balance my injectors. For $300 no fewer than three of Don's technicians and/or Don himself worked with me and my airplane for over 4 hours to dial in the injectors, conduct 3 test flights, give me a tour of their facility and tell me everything I ever wanted to know about fuel injection. I'm sure Don's classes are full of great information as he is extremely knowledgeable, but for my money the education I got while getting my injectors balanced was like having a personal tutor in a lab class. Outstanding!
Ron Schreck
RV-8, "Miss Izzy"
Gold Hill Airpark, NC
| Quote: | Pretty sure Don actually used to offer "Fuel >Injection 101" classes.
The http://www.airflowperformance.com web site has >an online thing for
it, but I coulda sworn he held occasional weekend >classes at their
facility in the past. Don't quote me on that...
|
| Quote: | do not archive
)_( Dan
--- |
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
panamared5(at)brier.net
Guest
|
| Posted: Mon Feb 12, 2007 3:45 pm Post subject: I've sworn off purge valve installations |
|
|
I am sorry to get into this dog fight a little late, but, I do not understand. My engine definately is hard to start and hard to keep running at idle during hot weather. I run an IO-360 (180 hp) Bendix FI system.
On taxi to and back from the runway on a hot day I get some pretty violent engine surges, settles down with boost pump on. It can take 30-40 revolutions to start the engine. Before I installed the purge valve, one time during a hotstart I had to take the cowl off and wait 90 minutes for engine cool down! I have even been supervised by Don Rivera himself during engine startup. My current solution; don't fly in hot weather
If this is not vapor lock, then what is it? .
You guys really got me confused
Bob
[quote] I have a problem when, in the absence of any clear data, a malfunction is attributed to 'vapor lock'. I've put up with all the rhetoric for a lot of years running auto fuel ..... in FL, on hot days, with both injected and carb'd engines (yep, run auto fuel through the injected engine too .... but not near as much as through a carb) with nary a hiccup. Not even any more hard starting problems than using 100LL. I guess the statement 'looked like vapor lock to me' just rubbed me the wrong way. Sorry. I really would rather have statements backed up by data or first-person-experience, not (to seal a line from a song) 'I heard it from a friend, who, heard it from a friend, who .... '.
The point I tried to make (and failed, I guess) is that all that engine running after startup should have purged any heat-soaked fuel. Once the heat soaked fuel is gone (from the firewall forward), the possibility of vapor lock goes way down ......
[b]
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
klwerner(at)comcast.net
Guest
|
| Posted: Mon Feb 12, 2007 5:00 pm Post subject: I've sworn off purge valve installations |
|
|
Bob,
I got another question on this subject. If you now have a purge valve on your engine and eventually get the hot engine started, is it then possible to taxi with the purge valve partially open (& boost pump ON)? Wouldn't this keep your engine happy by circulating this excess cool fuel while at a low powersetting?? If this would work, then don't forget to fully close the P.V. before T.O. though, as it could be disastrous.
Always do use a checklist for the runup sequence and make sure the PV is shut off /-fully closed!!!
I just wondered...
Do not archive
[quote] ---
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
khorton01(at)rogers.com
Guest
|
| Posted: Mon Feb 12, 2007 5:12 pm Post subject: I've sworn off purge valve installations |
|
|
This certainly sounds like it could be vapour lock. What things have
you done to the fuel system to try to improve the situation?
Kevin Horton
On 12 Feb 2007, at 18:44, Panama wrote:
| Quote: | I am sorry to get into this dog fight a little late, but, I do not
understand. My engine definately is hard to start and hard to keep
running at idle during hot weather. I run an IO-360 (180 hp)
Bendix FI system.
On taxi to and back from the runway on a hot day I get some pretty
violent engine surges, settles down with boost pump on. It can
take 30-40 revolutions to start the engine. Before I installed the
purge valve, one time during a hotstart I had to take the cowl off
and wait 90 minutes for engine cool down! I have even been
supervised by Don Rivera himself during engine startup. My current
solution; don't fly in hot weather
If this is not vapor lock, then what is it? .
You guys really got me confused
Bob
I have a problem when, in the absence of any clear data, a
malfunction is attributed to 'vapor lock'. I've put up with all
the rhetoric for a lot of years running auto fuel ..... in FL, on
hot days, with both injected and carb'd engines (yep, run auto fuel
through the injected engine too ..... but not near as much as
through a carb) with nary a hiccup. Not even any more hard
starting problems than using 100LL. I guess the statement 'looked
like vapor lock to me' just rubbed me the wrong way. Sorry. I
really would rather have statements backed up by data or first-
person-experience, not (to seal a line from a song) 'I heard it
from a friend, who, heard it from a friend, who .... '.
The point I tried to make (and failed, I guess) is that all that
engine running after startup should have purged any heat-soaked
fuel. Once the heat soaked fuel is gone (from the firewall
forward), the possibility of vapor lock goes way down ......
http://www.matronics.com/Navigator?RV-List_-
============================================================ _-
forums.matronics.com_-
============================================================
|
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?RV-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
