Today's Message Index:
----------------------
1. 06:35 AM - Re: Fuel flow (Roger Kemp M.D.)
2. 06:43 AM - Re: Fuel flow (Roger Kemp M.D.)
3. 07:48 AM - Re: Fuel flow (William Halverson)
4. 08:37 AM - Re: feul feed (A. Dennis Savarese)
5. 09:37 AM - Re: Fuel flow (KingCJ6@aol.com)
6. 09:42 AM - Really interesting video! (keithmckinley)
7. 12:54 PM - Re: Fuel flow (Gill Gutierrez)
8. 01:11 PM - Re: Fuel flow (Byron Fox)
9. 02:41 PM - Re: Fuel flow (Gill Gutierrez)
10. 02:55 PM - Re: Fuel flow (Byron Fox)
11. 02:56 PM - Re: feul feed (Walter Lannon)
12. 03:56 PM - Re: Fuel flow (Walter Lannon)
13. 03:56 PM - Re: Fuel flow (Gill Gutierrez)
14. 04:06 PM - Re: Fuel flow (Gill Gutierrez)
15. 04:55 PM - Experimental Class (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
16. 06:15 PM - Re: Experimental Class (Dale)
17. 07:15 PM - Re: fuel feed (Sam Sax)
18. 07:44 PM - Re: fuel feed (T A LEWIS)
Message 1
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PVC?
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of
KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
Subject: Re: Yak-List: Fuel flow
All =93 I think there have been 50+ posts on this subject in the
last few days, not counting the 100+ in years past. Bill Blackwell
sells a simple, very inexpensive kit consisting of some PVC tubing, two
manual cockpit mounted toggle shut-off valves and a few T-fittings that
takes about 3-4 hours for a novice A&P wana-be to install. Simply flip
the non-venting tank switch off for 5-10 minutes in-flight, and problem
solved.
The beauty of our =9Cexperimental=9D class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
wlannon@persona.ca writes:
Jim;
I agree with you as well - but this engineer type just came FROM the
bar.
Yes the same quantities of fuel in both tanks will result in the same
pressure being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being
applied on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
whatever produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing
force is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence,
perfect condition vents, etc.) it will take an imbalance of about 50
liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a
non fuel sloshing flight.
That it is invariably the right side hung up is I believe a result of
the vent system design. The left side vents much more directly than the
right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank,
I just don't feel that the vent line placed closer to one tank than the
other will cause the problem. If we have two tanks with equal amounts of
fuel in them AND they are level with each other, they both will exert
the same pressure head at the outlets. Hence the fuel in the header
tank, which is full at all times, will have that same pressure. The flop
valves will only open when pressure from the tank side is greater than
what is in the header tank and thus fuel will flow. So it bear to reason
that if the airplane is sitting on a slope, fuel from the high side will
flow. Since the head pressure builds up in the header tank the flop
valve on the lower side will close.
Now lets get the airplane moving. Now both tanks AND the header tank,
will not only have the head pressure but inertia forces acting on them.
IF you make coordinated turns forces are the same in the tank AND the
header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure
will force one flop valve open and fuel will feed from that tank. Assume
you have yaw left (left rudder peddle down), the inertia in the left
tank will effectively increase the head pressure and force open the left
flop valve, and the left tank will feed fuel. The right tank may have
exactly the same amount of fuel, but its inertia is a way from the flop
valve thus its head pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but
I think he was in a hurry to get to the bar. Would appreciate a back up
check on my theory.
Jim "Pappy" Goolsby
Message 2
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In the YAK, have done exactly that as well as have snap rolled the aircraft
into the heavy wing and away from the heavy wing with pretty much equal
results. On the ground on Dennis's advice have taken a rubber hose that will
fit the main drain and force low pressure air through it until air bubbling
could be heard in the right tank. If it was fuel in the siphon for the vent
that clears it out.
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 11:51 PM
Subject: Re: Yak-List: Fuel flow
In this case the right tank has the most fuel in it. Raise that wing (stick
left) while at the same time applying right rudder. You'll do two things.
Increase the head pressure of the right tank and induce a yaw to use inertia
to increase its effective pressure to open the flop valve. - - - - - - - I
think.
Jim "Pappy" Goolsby
-----Original Message-----
From: Paul Hamlin <ph451@yahoo.com>
Sent: Wed, May 19, 2010 12:12 am
Subject: Re: Yak-List: Fuel flow
So are you saying if the right tank is not feeding, step on the right
rudder. Others have said apply rudder on the low tank side (left).
--- On Wed, 5/19/10, cjpilot710@aol.com <cjpilot710@aol.com> wrote:
From: cjpilot710@aol.com <cjpilot710@aol.com>
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank, I
just don't feel that the vent line placed closer to one tank than the other
will cause the problem. If we have two tanks with equal amounts of fuel in
them AND they are level with each other, they both will exert the same
pressure head at the outlets. Hence the fuel in the header tank, which is
full at all times, will have that same pressure. The flop valves will only
open when pressure from the tank side is greater than what is in the header
tank and thus fuel will flow. So it bear to reason that if the airplane is
sitting on a slope, fuel from the high side will flow. Since the head
pressure builds up in the header tank the flop valve on the lower side will
close.
Now lets get the airplane moving. Now both tanks AND the header tank, will
not only have the head pressure but inertia forces acting on them. IF you
make coordinated turns forces are the same in the tank AND the header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure will
force one flop valve open and fuel will feed from that tank. Assume you have
yaw left (left rudder peddle down), the inertia in the left tank will
effectively increase the head pressure and force open the left flop valve,
and the left tank will feed fuel. The right tank may have exactly the same
amount of fuel, but its inertia is a way from the flop valve thus its head
pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but I
think he was in a hurry to get to the bar. Would appreciate a back up check
on my theory.
Jim "Pappy" Goolsby
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Message 3
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Exactly. Doesn't PVC + AvGas = Goo?
+-----Original Message-----
+From: Roger Kemp M.D. [mailto:viperdoc@mindspring.com]
+Sent: Wednesday, May 19, 2010 06:34 AM
+To: yak-list@matronics.com
+Subject: RE: Yak-List: Fuel flow
+
+PVC?
+
+Doc
+
+
+
+From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
+Sent: Wednesday, May 19, 2010 12:33 AM
+To: yak-list@matronics.com
+Subject: Re: Yak-List: Fuel flow
+
+
+
+All I think there have been 50+ posts on this subject in the last few days, not
counting the 100+ in years past. Bill Blackwell sells a simple, very inexpensive
kit consisting of some PVC tubing
Message 4
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Walt,
I will see if I can scrounge up some photos of the fuel junction and
flapper valves and send them to you off-list.
Dennis
----- Original Message -----
From: Walter Lannon
To: yak-list@matronics.com
Sent: Tuesday, May 18, 2010 11:32 PM
Subject: Re: Yak-List: feul feed
Hi Dennis;
It would be interesting to see the 52 flapper valve. It could very
well be an improved version of the early CJ6 valve which were likely
direct copies from the Yak 18 era.
The Chinese did at some point in time make a minor change that would
improve the flow. I have seen that improved valve in 1980's aircraft
but also the original 1960 type in the same aircraft.
I personally do not like the single point vent system since one leaf
cutter bee (common in this area) can spoil your whole day. If your
aircraft is parked outside here you are well advised to use a pitot
cover AND a vent cover. Lack of airspeed indication is a minor
annoyance. Lack of engine power is a major one.
The CJ has an advantage over the 52 for fuel tank venting in that the
outer wing has a 7 deg dihedral, The filler is at the inboard end and
the vent outlet at the outboard forward corner. This allows a fairly
generous expansion space that cannot be filled. Of course if the
temperature is high enough it can still vent fuel.
If I convert to an individual tank vent system (which I am
considering) I may install Parker MS series fuel vent valves with pin
hole bleeds.
Best;
Walt
----- Original Message -----
From: A. Dennis Savarese
To: yak-list@matronics.com
Sent: Tuesday, May 18, 2010 9:50 AM
Subject: Re: Yak-List: feul feed
Walt,
Although it seems questionable regarding the vent system as the
cause of fuel not feeding from one tank or the other, particularly in
the 52, the Yakovlev design bureau redesigned the vent system in the 89
and up model years. Two things happen on a pre 1989 Yak 52's which most
Yak 52 owners have experienced. When the fuel tanks are close to full
and the temperature builds causing the fuel to expand in the tank, if
one were to remove the fuel caps, you will hear a rather large "whoosh"
and the fuel will spill out of the filler neck all over the wing. This
is caused by pressure building in the tank. The only way the expanded
fuel can exit is via the vent line with the tank cap in place. The
second reason the vent system was redesigned was because of the
expansion and contraction of the very thin aluminum metal of the fuel
tanks. This expansion and contraction of the metal (ie: flexing)
created cracks in many of the fuel tanks as evident of the weld marks on
the bottom of the tanks seen in most pre 1989 Yak 52's.
The post 1989 vent system was far superior to the pre 1989 system.
The fuel tanks had two vent lines; one at the top, rear on the inside
(the same as pre 1989) and one on the top of the tank near the outboard
edge. This second vent line eliminated the expansion of the fuel and
the puking of the fuel overboard because the tank could "breath".
There are 2 separate vent systems on the post 1989 airplanes. One
system for each tank. And here's the most important fact,......no more
fuel feeding imbalance. The tanks are the same size. The flapper
valves are identical. The only thing that changed was the vent system.
Dennis
----- Original Message -----
From: Walter Lannon
To: yak-list@matronics.com
Sent: Tuesday, May 18, 2010 10:59 AM
Subject: Re: Yak-List: feul feed
If there was zero turbulence and the turn was perfectly
co-coordinated
throughout it may not work.
But in the real world it probably will.
If necessary I use a very brief "knife edge" - definitely not
co-coordinated.
I have a problem with the fuel in vent lines being the cause of
unequal
feed. If the lines are properly routed in relation to the max.
fuel level
in the tanks and are not blocked by some other material the fuel
in the
line will flow to wherever the pressure is lower. If the engine
is using
fuel that flow will be back to the tank.
The comments I have heard so far lead me to believe the Yak series
fuel feed
tank check valves are exactly the same as the Nanchang and are
therefore the
primary reason for unequal fuel flow.
The file and/or hacksaw cuts in the flapper used by the PLAAF and
others do
not address the problem.
They simply destroy the intended function of the valve
Have at it guys!
Walt
----- Original Message -----
From: "Stephen Morrey" <stephenmorrey@gmail.com>
To: <yak-list@matronics.com>
Sent: Tuesday, May 18, 2010 7:41 AM
Subject: Re: Yak-List: feul feed
<stephenmorrey@gmail.com>
>
> Again I am a little confused on this, it seems if the 360 turn
was
> coordinated then the turn should have had no effect. Do I
understand
> this correctly?
>
> On Tue, May 18, 2010 at 7:49 AM, Hans Oortman
<pa3arw@euronet.nl> wrote:
>> Dennis,
>>
>>
>>
>> It can be very scary though=85.When I ferried my Yak from
Estonia via
>> Lithuania back to Holland I found it to be very scary.
>>
>> I flew from Palanga (Lithuania) to Gdansk(Poland) over the
middle of the
>> Baltic Sea outside the airspace of Bullarus when the left tank
showed
>> only
>> 12 liters and the right hand tank was still at 60 liters. I
made a 90
>> degree
>> bank turn to the left and a full 360 back to the original
course=85after a
>> while I saw the right hand tank indicator flip to 50 ......man
I was glad
>> to
>> see that happening=85..problem solved=85.scary though=85.
>>
>>
>>
>> Hans
>>
>> RA3326K
>>
>> ________________________________
>>
>> Van: owner-yak-list-server@matronics.com
>> [mailto:owner-yak-list-server@matronics.com] Namens A. Dennis
Savarese
>> Verzonden: dinsdag 18 mei 2010 13:24
>> Aan: yak-list@matronics.com
>> Onderwerp: Re: Yak-List: feul feed
>>
>>
>>
>> Steve,
>>
>> In the Yak 52, the purpose of stepping on the low side tank is
two fold:
>> in
>> case one of the flapper valves in the fuel junction under the
front seat
>> is
>> stuck closed, forcing the weight of the fuel against the
flapper valve
>> may
>> free the flapper valve thus permitting fuel to flow; secondly
and more
>> likely, there is fuel in the vent line of the tank that is not
feeding
>> and
>> by stepping on the low side you are trying to force the fuel
out of the
>> vent
>> line.
>>
>>
>>
>> Assuming the airplane is trimmed properly as Pappy says, which
definitely
>> causes fuel imbalance, a vent line with fuel in it will
definitely affect
>> the fuel feed. I didn't realize I was probably forcing the fuel
into the
>> vent lines on the Yak 52 by filling the tanks all the way up to
the lip.
>> Because of the sitting angle of attack, the vent line at the
top, rear,
>> inside corner of the tank can get fuel in it by filling the
tank to the
>> lip. This is particularly true on the right tank because the
vent line
>> sits
>> lower in the fuselage than the left tank. Remember, the left
vent line
>> enters the fuselage and turns down and connects at the top of
the vent
>> junction. The right tank vent line is attached to the left side
of the
>> vent
>> junction which ends up being lower than the left tank vent
line. So when
>> fuel enters the right vent line by filling to the lip of the
filler neck,
>> it
>> may force the fuel into the vent line and into the vent
junction,
>> blocking
>> air back to the tank through the vent line.
>>
>>
>>
>> Also when the fuel heats up in the tank it expands and guess
where it
>> expands to? Right into the vent line. Have you ever seen a Yak
52
>> "puking"
>> fuel overboard on the ramp during hot weather? The reason is
the fuel has
>> expanded in the tank and is forced out of the vent line through
the vent
>> junction and out through the overboard vent line exiting out
the belly of
>> the airplane. Once the siphon has been set up by the expansion,
the
>> siphoning effect can siphon out 5+ gallons. No kidding.....it
happened to
>> me. I filled the airplane and left it on the ramp in the sun
for 2 days.
>> When I came back the fuel instrument no longer read 60/60. I
refilled the
>> tanks and it took over 5 gallons of fuel to bring the tanks
back to
>> 60/60.
>> The telltale sign was the dark, black spot in the blacktop
under the
>> fuselage directly under the vent line.
>>
>>
>>
>> Dennis
>>
>> ----- Original Message -----
>>
>> From: Stephen Morrey
>>
>> To: yak-list@matronics.com
>>
>> Sent: Monday, May 17, 2010 9:48 PM
>>
>> Subject: Re: Yak-List: feul feed
>>
>>
>>
<stephenmorrey@gmail.com>
>>
>> So just to be sure, am I correct in saying an in flight remidy
is to
>> step on the side showing the lowest fuel level. If this is the
case
>> is it best to simply step on the low side or is it needed to
step and
>> "hold" for an extended period of time on the low side ? Do I
have
>> this backwards? steve "old school"
>>
>> On Mon, May 17, 2010 at 12:19 PM, <cjpilot710@aol.com> wrote:
>>> Guys,
>>>
>>> The problem has always been aircraft yaw. The T-34 which has
the same
>>> fuel
>>> setup (on one model anyway) has had the same problem. If you
do not
>>> apply
>>> enough rudder on climb out, engine seem to pull out of the
left tank
>>> more.
>>> I have separate tank vent lines that go to the wing tips. I
was told
>>> that
>>> this would cure the uneven flow, when I put in the long range
tanks. It
>>> didn't. Yaw is the most likely cause of fuel imbalance.
>>>
>>> Jim "Pappy" Goolsby
>>>
>>> -----Original Message-----
>>> From: Chris Wise <wise@txc.net.au>
>>> To: yak-list@matronics.com
>>> Sent: Mon, May 17, 2010 2:18 am
>>> Subject: Re: Yak-List: feul feed
>>>
>>> G'Day Walt,
>>>
>>> We carry a piece of plastic tubing that fits over the vent
pipes and we
>>> use
>>> this to check the vents by blowing into the pipe.
>>> Every now and then we blow compressed air thru the vent.
>>> At no time have we ever found a blocked air vent.
>>> My mate also fitted new fuel cap seals. Did not solve the
problem.
>>>
>>> The check valves are a simple flapper valve that prevents any
X flow and
>>> I
>>> cannot see how they can be a problem.
>>> I am not familiar with the check valves on a CJ6
>>>
>>> Thanks and cheers,
>>> Chris.
>>>
>>>
>>>
>>> Chris Wise
>>> GT Propellers Australia
>>> __________________________________________________________
>>> Tel. +61 415 195 095 Fax. +61 8 8326 7268
>>>
>>> Email chris@gtpropellersaustralia.com.au
>>> Website www.gtpropellersaustralia.com.au
>>>
>>> The information transmitted in and with this email is intended
only for
>>> the
>>> person or entity to which it is addressed and may contain
confidential
>>> and/or privileged material. Any review, retransmission,
dissemination or
>>> other use of, or taking of any action in reliance upon this
information,
>>> by
>>> persons or entities other than the intended recipients is
prohibited. If
>>> you
>>> received this transmission in error, please contact the sender
and
>>> delete
>>> this e-mail and associated material from all computers and/or
systems.
>>> The
>>> intended recipient of this e-mail may only use, reproduce,
disclose or
>>> distribute the information contained in this e-mail and any
attached
>>> files,
>>> with the permission of the sender.
>>>
>>> ----- Original Message -----
>>> From: Walter Lannon
>>> To: yak-list@matronics.com
>>> Sent: Monday, May 17, 2010 2:05 PM
>>> Subject: Re: Yak-List: feul feed
>>> Hi Chris;
>>>
>>> The Nanchang exhibits the same fuel feed problem. Typically
the RH tank
>>> is
>>> late and I know of at least one forced landing with a full RH
and empty
>>> LH.
>>> Believe this was in South Africa about 6 or 7 years ago.
>>>
>>> The CJ6 has a single point vent system which I don't believe
is the
>>> problem. However the effective length of the vent line and the
fuel feed
>>> line are both longer for the RH tank. Theoretically that could
induce a
>>> lag
>>> in the RH feed time but I don't belive it is signifigant. Any
blockage
>>> of
>>> the vent by insect nests etc. will definitaly cause a big
problem.
>>>
>>> Other than the bugs that leaves the feed tank check valves as
the only
>>> remaining source. SPEAKING FOR THE CJ6 ONLY (since I have no
knowledge
>>> of
>>> the check valves in any of the Yak models) I believe I have
solved that
>>> problem with a modification to the check valve which, IMHO,
was very
>>> poorly
>>> designed.
>>>
>>> If you have the opportunity to take photos of one of your
check valves
>>> and
>>> email to me I will try to determine if the mod is applicable.
>>>
>>> Walt
>>>
>>>
>>> ----- Original Message -----
>>> From: Chris Wise
>>> To: yak-list@matronics.com
>>> Sent: Sunday, May 16, 2010 7:18 PM
>>> Subject: Yak-List: feul feed
>>> G'Day All,
>>>
>>> I and a friend each run a Yak18T.
>>> We suffer the same problem with both aircraft, re even fuel
feed.
>>> Flying in turbulence seems to help the problem, but still air
is bad
>>> news.
>>>
>>> The left tank will feed untill almost empty leaving plenty of
fuel in
>>> the
>>> right tank and on my mates 18, the low fuel warning light on
the left
>>> tank
>>> lit up and was fortunate enough to be close to a small country
strip
>>> where
>>> he landed in a hurry.
>>>
>>> He has teed both vents into one. This has not helped.
>>>
>>> I moved the left tank vent and re located the vent to about
3/4 of a
>>> inch
>>> next to the right tank vent thinking that it may be the vortex
from the
>>> prop
>>> that is allowing the right tank to feed. Or rather stopping
the left
>>> tank
>>> to
>>> feed.
>>> I have changed the angle of the vent pipe facing the airflow
to try and
>>> perhaps get more air into the vent to assist the left tank to
feed more.
>>> This has only marginally helped.
>>>
>>> I landed on Saturday with the left tank low fuel warning light
coming on
>>> on
>>> finals.
>>> The right tank had 65 - 70 litres fuel remaining and about 12
in the
>>> left
>>> when dipped.
>>>
>>> We have removed and carefully checked the check valves. No
problem
>>> there.
>>>
>>> Any suggestions would be greatly appreciated.
>>>
>>> Thanks and cheers,
>>> Chris.
>>>
>>>
>>> Chris Wise
>>> GT Propellers Australia
>>> __________________________________________________________
>>> Tel. +61 415 195 095 Fax. +61 8 8326 7268
>>>
>>> Email chris@gtpropellersaustralia.com.au
>>> Website www.gtpropellersaustralia.com.au
>>>
>>> The information transmitted in and with this email is intended
only for
>>> the
>>> person or entity to which it is addressed and may contain
confidential
>>> and/or privileged material. Any review, retransmission,
dissemination or
>>> other use of, or taking of any action in reliance upon this
information,
>>> by
>>> persons or entities other than the intended recipients is
prohibited. If
>>> you
>>> received this transmission in error, please contact the sender
and
>>> delete
>>> this e-mail and associated material from all computers and/or
systems.
>>> The
>>> intended recipient of this e-mail may only use, reproduce,
disclose or
>>> distribute the information contained in this e-mail and any
attached
>>> files,
>>> with the permission of the sender.
>>>
>>>
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Sorry, it's a gas-friendly flex fuel tubing, about 3/8" OD
In a message dated 5/19/2010 7:48:12 A.M. Pacific Daylight Time,
william@netpros.net writes:
--> Yak-List message posted by: "William Halverson" <william@netpros.net
>
Exactly. Doesn't PVC + AvGas = Goo?
+-----Original Message-----
+From: Roger Kemp M.D. [mailto:viperdoc@mindspring.com]
+Sent: Wednesday, May 19, 2010 06:34 AM
+To: yak-list@matronics.com
+Subject: RE: Yak-List: Fuel flow
+
+PVC?
+
+Doc
+
+
+
+From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
+Sent: Wednesday, May 19, 2010 12:33 AM
+To: yak-list@matronics.com
+Subject: Re: Yak-List: Fuel flow
+
+
+
+All =93 I think there have been 50+ posts on this subject in the la
st few
days, not counting the 100+ in years past. Bill Blackwell sells a simple
,
very inexpensive kit consisting of some PVC tubing
========================
===========
========================
===========
========================
===========
========================
===========
Message 6
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|
| Subject: | Really interesting video! |
Sent to me by a fellow CJ pilot. Just what we need!
http://widgets.nbc.com/o/47f1317f105123ad/498ebd00a62edaa0/47fe70d4555df05a/9e46bd46/-cpid/ba4377d3bfd6c
--------
Keith McKinley
700HS
KFIT
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=298193#298193
Message 7
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Don=99t install vent control valves on metal tanks unless you want
smaller tanks!
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Roger Kemp
M.D.
Sent: Wednesday, May 19, 2010 6:34 AM
Subject: RE: Yak-List: Fuel flow
PVC?
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of
KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
Subject: Re: Yak-List: Fuel flow
All =93 I think there have been 50+ posts on this subject in the
last few days, not counting the 100+ in years past. Bill Blackwell
sells a simple, very inexpensive kit consisting of some PVC tubing, two
manual cockpit mounted toggle shut-off valves and a few T-fittings that
takes about 3-4 hours for a novice A&P wana-be to install. Simply flip
the non-venting tank switch off for 5-10 minutes in-flight, and problem
solved.
The beauty of our =9Cexperimental=9D class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
wlannon@persona.ca writes:
Jim;
I agree with you as well - but this engineer type just came FROM the
bar.
Yes the same quantities of fuel in both tanks will result in the same
pressure being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being
applied on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
whatever produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing
force is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence,
perfect condition vents, etc.) it will take an imbalance of about 50
liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a
non fuel sloshing flight.
That it is invariably the right side hung up is I believe a result of
the vent system design. The left side vents much more directly than the
right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank,
I just don't feel that the vent line placed closer to one tank than the
other will cause the problem. If we have two tanks with equal amounts of
fuel in them AND they are level with each other, they both will exert
the same pressure head at the outlets. Hence the fuel in the header
tank, which is full at all times, will have that same pressure. The flop
valves will only open when pressure from the tank side is greater than
what is in the header tank and thus fuel will flow. So it bear to reason
that if the airplane is sitting on a slope, fuel from the high side will
flow. Since the head pressure builds up in the header tank the flop
valve on the lower side will close.
Now lets get the airplane moving. Now both tanks AND the header tank,
will not only have the head pressure but inertia forces acting on them.
IF you make coordinated turns forces are the same in the tank AND the
header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure
will force one flop valve open and fuel will feed from that tank. Assume
you have yaw left (left rudder peddle down), the inertia in the left
tank will effectively increase the head pressure and force open the left
flop valve, and the left tank will feed fuel. The right tank may have
exactly the same amount of fuel, but its inertia is a way from the flop
valve thus its head pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but
I think he was in a hurry to get to the bar. Would appreciate a back up
check on my theory.
Jim "Pappy" Goolsby
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
Message 8
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|
I have Blackwell's vent valve kit on my metal tanks, and indeed you must be
careful. Our thin-walled CJ tanks will collapse if you fail to cycle the
vent valve switch frequently. I was shocked at the oil-canning I heard when
pulled a fuel cap off after failing to turn the switch off. Now, I cycle th
e
switch about every ten minutes until balance is achieved. No fuel tank leak
s
have appeared, and I've had the systems in place for about five years.
...Blitz
On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
> Don=92t install vent control valves on metal tanks unless you want small
er
> tanks!
>
>
> Gill
>
>
> *From:* owner-yak-list-server@matronics.com [mailto:
> owner-yak-list-server@matronics.com] *On Behalf Of *Roger Kemp M.D.
> *Sent:* Wednesday, May 19, 2010 6:34 AM
> *To:* yak-list@matronics.com
> *Subject:* RE: Yak-List: Fuel flow
>
>
> PVC?
>
> Doc
>
>
> *From:* owner-yak-list-server@matronics.com [mailto:
> owner-yak-list-server@matronics.com] *On Behalf Of *KingCJ6@aol.com
> *Sent:* Wednesday, May 19, 2010 12:33 AM
> *To:* yak-list@matronics.com
> *Subject:* Re: Yak-List: Fuel flow
>
>
> All ' I think there have been 50+ posts on this subject in the last few
> days, not counting the 100+ in years past. Bill Blackwell sells a simple
,
> very inexpensive kit consisting of some PVC tubing, two manual cockpit
> mounted toggle shut-off valves and a few T-fittings that takes about 3-4
> hours for a novice A&P wana-be to install. Simply flip the non-venting t
ank
> switch off for 5-10 minutes in-flight, and problem solved.
>
>
> The beauty of our =93experimental=94 class!
>
>
> Dave
>
>
> In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
> wlannon@persona.ca writes:
>
> Jim;
>
>
> I agree with you as well - but this engineer type just came FROM the bar.
>
> Yes the same quantities of fuel in both tanks will result in the same
> pressure being applied to both sides of the flapper valve.
>
> But that same pressure does not translate into the same force being appli
ed
> on each side of the valve.
>
>
> Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
> whatever produces equal force only when applied to an equal area.
>
>
> That is precisely the problem with the CJ flapper valve. The closing forc
e
> is actually 3 to 4 times the opening force with equal pressure.
>
> In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence,
> perfect condition vents, etc.) it will take an imbalance of about 50 lite
rs
> to open.
>
>
> Fortunately we rarely ever find a day, or a pilot, that can deliver a non
> fuel sloshing flight.
>
>
> That it is invariably the right side hung up is I believe a result of the
> vent system design. The left side vents much more directly than the righ
t.
>
>
> Walt
>
>
> ----- Original Message -----
>
> *From:* cjpilot710@aol.com
>
> *To:* yak-list@matronics.com
>
> *Sent:* Tuesday, May 18, 2010 8:44 PM
>
> *Subject:* Yak-List: Fuel flow
>
>
> Let me see if I can elucidate what I think happens.
>
>
> While a plug vent will definitely cause fuel to flow from just one tank,
I
> just don't feel that the vent line placed closer to one tank than the oth
er
> will cause the problem. If we have two tanks with equal amounts of fuel i
n
> them AND they are level with each other, they both will exert the same
> pressure head at the outlets. Hence the fuel in the header tank, which is
> full at all times, will have that same pressure. The flop valves will onl
y
> open when pressure from the tank side is greater than what is in the head
er
> tank and thus fuel will flow. So it bear to reason that if the airplane i
s
> sitting on a slope, fuel from the high side will flow. Since the head
> pressure builds up in the header tank the flop valve on the lower side wi
ll
> close.
>
>
> Now lets get the airplane moving. Now both tanks AND the header tank, wil
l
> not only have the head pressure but inertia forces acting on them. IF you
> make coordinated turns forces are the same in the tank AND the header tan
k.
>
>
> But lets say you have a slight yaw either in a turn or wings level, the
> inertia forces of the fuel tank will actually increase head pressure will
> force one flop valve open and fuel will feed from that tank. Assume you h
ave
> yaw left (left rudder peddle down), the inertia in the left tank will
> effectively increase the head pressure and force open the left flop valve
,
> and the left tank will feed fuel. The right tank may have exactly the sam
e
> amount of fuel, but its inertia is a way from the flop valve thus its hea
d
> pressure is effective less.
>
>
> The inertia of the fuel in the header tank will react the same - helping
> keep the opposite flop valve closed.
>
>
> Anyway that's what I think happens. A engineer type agreed with me, but I
> think he was in a hurry to get to the bar. Would appreciate a back up che
ck
> on my theory.
>
>
> Jim "Pappy" Goolsby
>
> * *
>
> * *
>
> * *
>
> * *
>
> * *
>
> * *
>
> *http://www.matronics.com/Navigator?Yak-List*
>
> * *
>
> *http://forums.matronics.com*
>
> * *
>
> *http://www.matronics.com/contribution*
>
> * *
>
> * *
>
> * *
>
> * *
>
> **
>
> **
>
> **
>
> **
>
> **
>
> **
>
> *http://www.matronics.com/Navigator?Yak-List*
>
> **
>
> **
>
> **
>
> *http://forums.matronics.com*
>
> **
>
> **
>
> **
>
> **
>
> *http://www.matronics.com/contribution*
>
> **
>
> * *
>
> *
>
===========
===========
===========
===========
> *
>
>
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
Message 9
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Blitz,
I designed the vent control valves to work with rubber bladders where
permanent deformation is not a issue like it is on metal tanks. The engine
fuel pump is a positive displacement device which can cause nearly a full
atmosphere of negative pressure which is sufficient to collapse the flat
sides on the standard metal tanks, even thick walled ones. As a minimum I
suggest you install a spring check valve with a low break pressure so a to
limit the pressure differential between the inside of the tank and the
ambient pressure.
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Byron Fox
Sent: Wednesday, May 19, 2010 1:10 PM
Subject: Re: Yak-List: Fuel flow
I have Blackwell's vent valve kit on my metal tanks, and indeed you must be
careful. Our thin-walled CJ tanks will collapse if you fail to cycle the
vent valve switch frequently. I was shocked at the oil-canning I heard when
pulled a fuel cap off after failing to turn the switch off. Now, I cycle the
switch about every ten minutes until balance is achieved. No fuel tank leaks
have appeared, and I've had the systems in place for about five years.
...Blitz
On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
Don't install vent control valves on metal tanks unless you want smaller
tanks!
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Roger Kemp M.D.
Sent: Wednesday, May 19, 2010 6:34 AM
Subject: RE: Yak-List: Fuel flow
PVC?
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
Subject: Re: Yak-List: Fuel flow
All - I think there have been 50+ posts on this subject in the last few
days, not counting the 100+ in years past. Bill Blackwell sells a simple,
very inexpensive kit consisting of some PVC tubing, two manual cockpit
mounted toggle shut-off valves and a few T-fittings that takes about 3-4
hours for a novice A&P wana-be to install. Simply flip the non-venting tank
switch off for 5-10 minutes in-flight, and problem solved.
The beauty of our "experimental" class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
wlannon@persona.ca writes:
Jim;
I agree with you as well - but this engineer type just came FROM the bar.
Yes the same quantities of fuel in both tanks will result in the same
pressure being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being applied
on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
whatever produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing force
is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect
condition vents, etc.) it will take an imbalance of about 50 liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a non
fuel sloshing flight.
That it is invariably the right side hung up is I believe a result of the
vent system design. The left side vents much more directly than the right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank, I
just don't feel that the vent line placed closer to one tank than the other
will cause the problem. If we have two tanks with equal amounts of fuel in
them AND they are level with each other, they both will exert the same
pressure head at the outlets. Hence the fuel in the header tank, which is
full at all times, will have that same pressure. The flop valves will only
open when pressure from the tank side is greater than what is in the header
tank and thus fuel will flow. So it bear to reason that if the airplane is
sitting on a slope, fuel from the high side will flow. Since the head
pressure builds up in the header tank the flop valve on the lower side will
close.
Now lets get the airplane moving. Now both tanks AND the header tank, will
not only have the head pressure but inertia forces acting on them. IF you
make coordinated turns forces are the same in the tank AND the header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure will
force one flop valve open and fuel will feed from that tank. Assume you have
yaw left (left rudder peddle down), the inertia in the left tank will
effectively increase the head pressure and force open the left flop valve,
and the left tank will feed fuel. The right tank may have exactly the same
amount of fuel, but its inertia is a way from the flop valve thus its head
pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but I
think he was in a hurry to get to the bar. Would appreciate a back up check
on my theory.
Jim "Pappy" Goolsby
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
et="_blank">http://www.matronics.com/Navigator?Yak-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
Message 10
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|
Excellent thought, Gill, and easy to install. Where might I locate such a
check valve? Thanks, Blitz
On Wed, May 19, 2010 at 2:49 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
> Blitz,
>
>
> I designed the vent control valves to work with rubber bladders where
> permanent deformation is not a issue like it is on metal tanks. The engi
ne
> fuel pump is a positive displacement device which can cause nearly a full
> atmosphere of negative pressure which is sufficient to collapse the flat
> sides on the standard metal tanks, even thick walled ones. As a minimum
I
> suggest you install a spring check valve with a low break pressure so a t
o
> limit the pressure differential between the inside of the tank and the
> ambient pressure.
>
>
> Gill
>
>
> *From:* owner-yak-list-server@matronics.com [mailto:
> owner-yak-list-server@matronics.com] *On Behalf Of *Byron Fox
> *Sent:* Wednesday, May 19, 2010 1:10 PM
>
> *To:* yak-list@matronics.com
> *Subject:* Re: Yak-List: Fuel flow
>
>
> I have Blackwell's vent valve kit on my metal tanks, *and indeed you must
> be careful. * Our thin-walled CJ tanks will collapse if you fail to cycle
> the vent valve switch frequently. I was shocked at the oil-canning I hear
d
> when pulled a fuel cap off after failing to turn the switch off. Now, I
> cycle the switch about every ten minutes until balance is achieved. No fu
el
> tank leaks have appeared, and I've had the systems in place for about fiv
e
> years. ...Blitz
>
>
> On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com>
> wrote:
>
> Don=92t install vent control valves on metal tanks unless you want smalle
r
> tanks!
>
>
> Gill
>
>
> *From:* owner-yak-list-server@matronics.com [mailto:
> owner-yak-list-server@matronics.com] *On Behalf Of *Roger Kemp M.D.
> *Sent:* Wednesday, May 19, 2010 6:34 AM
> *To:* yak-list@matronics.com
> *Subject:* RE: Yak-List: Fuel flow
>
>
> PVC?
>
> Doc
>
>
> *From:* owner-yak-list-server@matronics.com [mailto:
> owner-yak-list-server@matronics.com] *On Behalf Of *KingCJ6@aol.com
> *Sent:* Wednesday, May 19, 2010 12:33 AM
> *To:* yak-list@matronics.com
> *Subject:* Re: Yak-List: Fuel flow
>
>
> All ' I think there have been 50+ posts on this subject in the last few
> days, not counting the 100+ in years past. Bill Blackwell sells a simple
,
> very inexpensive kit consisting of some PVC tubing, two manual cockpit
> mounted toggle shut-off valves and a few T-fittings that takes about 3-4
> hours for a novice A&P wana-be to install. Simply flip the non-venting t
ank
> switch off for 5-10 minutes in-flight, and problem solved.
>
>
> The beauty of our =93experimental=94 class!
>
>
> Dave
>
>
> In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
> wlannon@persona.ca writes:
>
> Jim;
>
>
> I agree with you as well - but this engineer type just came FROM the bar.
>
> Yes the same quantities of fuel in both tanks will result in the same
> pressure being applied to both sides of the flapper valve.
>
> But that same pressure does not translate into the same force being appli
ed
> on each side of the valve.
>
>
> Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
> whatever produces equal force only when applied to an equal area.
>
>
> That is precisely the problem with the CJ flapper valve. The closing forc
e
> is actually 3 to 4 times the opening force with equal pressure.
>
> In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence,
> perfect condition vents, etc.) it will take an imbalance of about 50 lite
rs
> to open.
>
>
> Fortunately we rarely ever find a day, or a pilot, that can deliver a non
> fuel sloshing flight.
>
>
> That it is invariably the right side hung up is I believe a result of the
> vent system design. The left side vents much more directly than the righ
t.
>
>
> Walt
>
>
> ----- Original Message -----
>
> *From:* cjpilot710@aol.com
>
> *To:* yak-list@matronics.com
>
> *Sent:* Tuesday, May 18, 2010 8:44 PM
>
> *Subject:* Yak-List: Fuel flow
>
>
> Let me see if I can elucidate what I think happens.
>
>
> While a plug vent will definitely cause fuel to flow from just one tank,
I
> just don't feel that the vent line placed closer to one tank than the oth
er
> will cause the problem. If we have two tanks with equal amounts of fuel i
n
> them AND they are level with each other, they both will exert the same
> pressure head at the outlets. Hence the fuel in the header tank, which is
> full at all times, will have that same pressure. The flop valves will onl
y
> open when pressure from the tank side is greater than what is in the head
er
> tank and thus fuel will flow. So it bear to reason that if the airplane i
s
> sitting on a slope, fuel from the high side will flow. Since the head
> pressure builds up in the header tank the flop valve on the lower side wi
ll
> close.
>
>
> Now lets get the airplane moving. Now both tanks AND the header tank, wil
l
> not only have the head pressure but inertia forces acting on them. IF you
> make coordinated turns forces are the same in the tank AND the header tan
k.
>
>
> But lets say you have a slight yaw either in a turn or wings level, the
> inertia forces of the fuel tank will actually increase head pressure will
> force one flop valve open and fuel will feed from that tank. Assume you h
ave
> yaw left (left rudder peddle down), the inertia in the left tank will
> effectively increase the head pressure and force open the left flop valve
,
> and the left tank will feed fuel. The right tank may have exactly the sam
e
> amount of fuel, but its inertia is a way from the flop valve thus its hea
d
> pressure is effective less.
>
>
> The inertia of the fuel in the header tank will react the same - helping
> keep the opposite flop valve closed.
>
>
> Anyway that's what I think happens. A engineer type agreed with me, but I
> think he was in a hurry to get to the bar. Would appreciate a back up che
ck
> on my theory.
>
>
> Jim "Pappy" Goolsby
>
> * *
>
> * *
>
> * *
>
> * *
>
> * *
>
> * *
>
> *http://www.matronics.com/Navigator?Yak-List*
>
> * *
>
> *http://forums.matronics.com*
>
> * *
>
> *http://www.matronics.com/contribution*
>
> * *
>
> * *
>
> * *
>
> * *
>
> *http://www.matronics.com/Navigator?Yak-List*
>
> *http://forums.matronics.com*
>
> *http://www.matronics.com/contribution*
>
> * *
>
> * *
>
> * *
>
> *et="_blank">http://www.matronics.com/Navigator?Yak-List*
>
> *tp://forums.matronics.com*
>
> *_blank">http://www.matronics.com/contribution*
>
> * *
>
>
> --
> Byron M. Fox
> 80 Milland Drive
> Mill Valley, CA 94941
> 415-307-2405
>
> * *
>
> * *
>
> **
>
> **
>
> **
>
> **
>
> **
>
> **
>
> *http://www.matronics.com/Navigator?Yak-List*
>
> **
>
> **
>
> **
>
> *http://forums.matronics.com*
>
> **
>
> **
>
> **
>
> **
>
> *http://www.matronics.com/contribution*
>
> **
>
> * *
>
> *
>
===========
===========
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> *
>
>
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
Message 11
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Thanks Dennis
----- Original Message -----
From: A. Dennis Savarese
To: yak-list@matronics.com
Sent: Wednesday, May 19, 2010 8:19 AM
Subject: Re: Yak-List: feul feed
Walt,
I will see if I can scrounge up some photos of the fuel junction and flapper
valves and send them to you off-list.
Dennis
Message 12
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Gill;
Over the years I have seen two T6 (actually 1 T6, 1 Harvard) fuel tanks "reworked"
by plugged vents. These are not light wall tanks. You could touch the tank
bottom with your fingers through the filler opening.
Also recall one of our Bristol Brittanias sched. run Mexico City to Toronto .
Emergency landing in the US (can't remember where) due running out of fuel. These
were all bag tanks, all were sucked to the top. Vents all plugged by some
Mexican bugs!
Walt
----- Original Message -----
From: Gill Gutierrez
To: yak-list@matronics.com
Sent: Wednesday, May 19, 2010 2:49 PM
Subject: RE: Yak-List: Fuel flow
Blitz,
I designed the vent control valves to work with rubber bladders where permanent
deformation is not a issue like it is on metal tanks. The engine fuel pump
is a positive displacement device which can cause nearly a full atmosphere of
negative pressure which is sufficient to collapse the flat sides on the standard
metal tanks, even thick walled ones. As a minimum I suggest you install a
spring check valve with a low break pressure so a to limit the pressure differential
between the inside of the tank and the ambient pressure.
Gill
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Byron Fox
Sent: Wednesday, May 19, 2010 1:10 PM
To: yak-list@matronics.com
Subject: Re: Yak-List: Fuel flow
I have Blackwell's vent valve kit on my metal tanks, and indeed you must be careful.
Our thin-walled CJ tanks will collapse if you fail to cycle the vent
valve switch frequently. I was shocked at the oil-canning I heard when pulled
a fuel cap off after failing to turn the switch off. Now, I cycle the switch about
every ten minutes until balance is achieved. No fuel tank leaks have appeared,
and I've had the systems in place for about five years. ...Blitz
On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
Don't install vent control valves on metal tanks unless you want smaller tanks!
Gill
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of Roger Kemp M.D.
Sent: Wednesday, May 19, 2010 6:34 AM
To: yak-list@matronics.com
Subject: RE: Yak-List: Fuel flow
PVC?
Doc
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
To: yak-list@matronics.com
Subject: Re: Yak-List: Fuel flow
All - I think there have been 50+ posts on this subject in the last few days,
not counting the 100+ in years past. Bill Blackwell sells a simple, very inexpensive
kit consisting of some PVC tubing, two manual cockpit mounted toggle
shut-off valves and a few T-fittings that takes about 3-4 hours for a novice
A&P wana-be to install. Simply flip the non-venting tank switch off for 5-10
minutes in-flight, and problem solved.
The beauty of our "experimental" class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time, wlannon@persona.ca
writes:
Jim;
I agree with you as well - but this engineer type just came FROM the bar.
Yes the same quantities of fuel in both tanks will result in the same pressure
being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being applied
on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or whatever
produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing force
is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect
condition vents, etc.) it will take an imbalance of about 50 liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a non fuel
sloshing flight.
That it is invariably the right side hung up is I believe a result of the vent
system design. The left side vents much more directly than the right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
To: yak-list@matronics.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank,
I just don't feel that the vent line placed closer to one tank than the other
will cause the problem. If we have two tanks with equal amounts of fuel in them
AND they are level with each other, they both will exert the same pressure head
at the outlets. Hence the fuel in the header tank, which is full at all times,
will have that same pressure. The flop valves will only open when pressure
from the tank side is greater than what is in the header tank and thus fuel
will flow. So it bear to reason that if the airplane is sitting on a slope, fuel
from the high side will flow. Since the head pressure builds up in the header
tank the flop valve on the lower side will close.
Now lets get the airplane moving. Now both tanks AND the header tank, will
not only have the head pressure but inertia forces acting on them. IF you make
coordinated turns forces are the same in the tank AND the header tank.
But lets say you have a slight yaw either in a turn or wings level, the inertia
forces of the fuel tank will actually increase head pressure will force
one flop valve open and fuel will feed from that tank. Assume you have yaw left
(left rudder peddle down), the inertia in the left tank will effectively increase
the head pressure and force open the left flop valve, and the left tank
will feed fuel. The right tank may have exactly the same amount of fuel, but
its inertia is a way from the flop valve thus its head pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but I
think he was in a hurry to get to the bar. Would appreciate a back up check on
my theory.
Jim "Pappy" Goolsby
http://www.matronics.com/Navigator?Yak-List http://forums.matronics.com http://www.matronics.com/contribution http://www.matronics.com/Navigator?Yak-Listhttp://forums.matronics.comhttp://www.matronics.com/contribution et="_blank">http://www.matronics.com/Navigator?Yak-Listtp://forums.matronics.com_blank">http://www.matronics.com/contribution
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
http://www.matronics.com/Navigator?Yak-Listhttp://forums.matronics.comhttp://www.matronics.com/contribution
Message 13
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Blitz,
Aircraft Spruce has spring loaded check valves with low break pressure. You
can always adjust break pressure by changing the spring. I can't tell you
the pressure you need but I would think something under 12"wg which is
equivalent to 20"fuel gauge and under 0.5 psig. You can use a simple U-tube
water filled manometer to test with. The other concern I have has to do
with metal fatigue and ultimately a crack developing as a result of pressure
pulsing the tank sides. You should locate the check valves so that they are
between you vent control valves and the tanks. That will require a tee in
each line to accommodate the new check valves. Also, remember that the
collector tank is vented through one of the wing tanks, assuming you didn't
separate the vents when you installed the valves.
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Byron Fox
Sent: Wednesday, May 19, 2010 2:55 PM
Subject: Re: Yak-List: Fuel flow
Excellent thought, Gill, and easy to install. Where might I locate such a
check valve? Thanks, Blitz
On Wed, May 19, 2010 at 2:49 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
Blitz,
I designed the vent control valves to work with rubber bladders where
permanent deformation is not a issue like it is on metal tanks. The engine
fuel pump is a positive displacement device which can cause nearly a full
atmosphere of negative pressure which is sufficient to collapse the flat
sides on the standard metal tanks, even thick walled ones. As a minimum I
suggest you install a spring check valve with a low break pressure so a to
limit the pressure differential between the inside of the tank and the
ambient pressure.
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Byron Fox
Sent: Wednesday, May 19, 2010 1:10 PM
Subject: Re: Yak-List: Fuel flow
I have Blackwell's vent valve kit on my metal tanks, and indeed you must be
careful. Our thin-walled CJ tanks will collapse if you fail to cycle the
vent valve switch frequently. I was shocked at the oil-canning I heard when
pulled a fuel cap off after failing to turn the switch off. Now, I cycle the
switch about every ten minutes until balance is achieved. No fuel tank leaks
have appeared, and I've had the systems in place for about five years.
...Blitz
On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
Don't install vent control valves on metal tanks unless you want smaller
tanks!
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Roger Kemp M.D.
Sent: Wednesday, May 19, 2010 6:34 AM
Subject: RE: Yak-List: Fuel flow
PVC?
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
Subject: Re: Yak-List: Fuel flow
All - I think there have been 50+ posts on this subject in the last few
days, not counting the 100+ in years past. Bill Blackwell sells a simple,
very inexpensive kit consisting of some PVC tubing, two manual cockpit
mounted toggle shut-off valves and a few T-fittings that takes about 3-4
hours for a novice A&P wana-be to install. Simply flip the non-venting tank
switch off for 5-10 minutes in-flight, and problem solved.
The beauty of our "experimental" class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
wlannon@persona.ca writes:
Jim;
I agree with you as well - but this engineer type just came FROM the bar.
Yes the same quantities of fuel in both tanks will result in the same
pressure being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being applied
on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
whatever produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing force
is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect
condition vents, etc.) it will take an imbalance of about 50 liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a non
fuel sloshing flight.
That it is invariably the right side hung up is I believe a result of the
vent system design. The left side vents much more directly than the right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank, I
just don't feel that the vent line placed closer to one tank than the other
will cause the problem. If we have two tanks with equal amounts of fuel in
them AND they are level with each other, they both will exert the same
pressure head at the outlets. Hence the fuel in the header tank, which is
full at all times, will have that same pressure. The flop valves will only
open when pressure from the tank side is greater than what is in the header
tank and thus fuel will flow. So it bear to reason that if the airplane is
sitting on a slope, fuel from the high side will flow. Since the head
pressure builds up in the header tank the flop valve on the lower side will
close.
Now lets get the airplane moving. Now both tanks AND the header tank, will
not only have the head pressure but inertia forces acting on them. IF you
make coordinated turns forces are the same in the tank AND the header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure will
force one flop valve open and fuel will feed from that tank. Assume you have
yaw left (left rudder peddle down), the inertia in the left tank will
effectively increase the head pressure and force open the left flop valve,
and the left tank will feed fuel. The right tank may have exactly the same
amount of fuel, but its inertia is a way from the flop valve thus its head
pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but I
think he was in a hurry to get to the bar. Would appreciate a back up check
on my theory.
Jim "Pappy" Goolsby
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
et="_blank">http://www.matronics.com/Navigator?Yak-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
et="_blank">http://www.matronics.com/Navigator?Yak-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
Message 14
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Walt,
You are right, if the vents get plugged, metal and/or bag tanks will
collapse. It's just harder to get the metal tanks back into shape.
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lannon
Sent: Wednesday, May 19, 2010 3:57 PM
Subject: Re: Yak-List: Fuel flow
Gill;
Over the years I have seen two T6 (actually 1 T6, 1 Harvard) fuel tanks
"reworked" by plugged vents. These are not light wall tanks. You could
touch the tank bottom with your fingers through the filler opening.
Also recall one of our Bristol Brittanias sched. run Mexico City to Toronto
. Emergency landing in the US (can't remember where) due running out of
fuel. These were all bag tanks, all were sucked to the top. Vents all
plugged by some Mexican bugs!
Walt
----- Original Message -----
From: Gill Gutierrez <mailto:gill.g@gpimail.com>
Sent: Wednesday, May 19, 2010 2:49 PM
Subject: RE: Yak-List: Fuel flow
Blitz,
I designed the vent control valves to work with rubber bladders where
permanent deformation is not a issue like it is on metal tanks. The engine
fuel pump is a positive displacement device which can cause nearly a full
atmosphere of negative pressure which is sufficient to collapse the flat
sides on the standard metal tanks, even thick walled ones. As a minimum I
suggest you install a spring check valve with a low break pressure so a to
limit the pressure differential between the inside of the tank and the
ambient pressure.
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Byron Fox
Sent: Wednesday, May 19, 2010 1:10 PM
Subject: Re: Yak-List: Fuel flow
I have Blackwell's vent valve kit on my metal tanks, and indeed you must be
careful. Our thin-walled CJ tanks will collapse if you fail to cycle the
vent valve switch frequently. I was shocked at the oil-canning I heard when
pulled a fuel cap off after failing to turn the switch off. Now, I cycle the
switch about every ten minutes until balance is achieved. No fuel tank leaks
have appeared, and I've had the systems in place for about five years.
...Blitz
On Wed, May 19, 2010 at 1:03 PM, Gill Gutierrez <gill.g@gpimail.com> wrote:
Don't install vent control valves on metal tanks unless you want smaller
tanks!
Gill
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Roger Kemp M.D.
Sent: Wednesday, May 19, 2010 6:34 AM
Subject: RE: Yak-List: Fuel flow
PVC?
Doc
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 12:33 AM
Subject: Re: Yak-List: Fuel flow
All - I think there have been 50+ posts on this subject in the last few
days, not counting the 100+ in years past. Bill Blackwell sells a simple,
very inexpensive kit consisting of some PVC tubing, two manual cockpit
mounted toggle shut-off valves and a few T-fittings that takes about 3-4
hours for a novice A&P wana-be to install. Simply flip the non-venting tank
switch off for 5-10 minutes in-flight, and problem solved.
The beauty of our "experimental" class!
Dave
In a message dated 5/18/2010 10:07:46 P.M. Pacific Daylight Time,
wlannon@persona.ca writes:
Jim;
I agree with you as well - but this engineer type just came FROM the bar.
Yes the same quantities of fuel in both tanks will result in the same
pressure being applied to both sides of the flapper valve.
But that same pressure does not translate into the same force being applied
on each side of the valve.
Pressure, whether described in pounds per sq. ft, grams per sq. cm. or
whatever produces equal force only when applied to an equal area.
That is precisely the problem with the CJ flapper valve. The closing force
is actually 3 to 4 times the opening force with equal pressure.
In fact with absolutely no fuel sloshing (ie: no yaw, no turbulence, perfect
condition vents, etc.) it will take an imbalance of about 50 liters to open.
Fortunately we rarely ever find a day, or a pilot, that can deliver a non
fuel sloshing flight.
That it is invariably the right side hung up is I believe a result of the
vent system design. The left side vents much more directly than the right.
Walt
----- Original Message -----
From: cjpilot710@aol.com
Sent: Tuesday, May 18, 2010 8:44 PM
Subject: Yak-List: Fuel flow
Let me see if I can elucidate what I think happens.
While a plug vent will definitely cause fuel to flow from just one tank, I
just don't feel that the vent line placed closer to one tank than the other
will cause the problem. If we have two tanks with equal amounts of fuel in
them AND they are level with each other, they both will exert the same
pressure head at the outlets. Hence the fuel in the header tank, which is
full at all times, will have that same pressure. The flop valves will only
open when pressure from the tank side is greater than what is in the header
tank and thus fuel will flow. So it bear to reason that if the airplane is
sitting on a slope, fuel from the high side will flow. Since the head
pressure builds up in the header tank the flop valve on the lower side will
close.
Now lets get the airplane moving. Now both tanks AND the header tank, will
not only have the head pressure but inertia forces acting on them. IF you
make coordinated turns forces are the same in the tank AND the header tank.
But lets say you have a slight yaw either in a turn or wings level, the
inertia forces of the fuel tank will actually increase head pressure will
force one flop valve open and fuel will feed from that tank. Assume you have
yaw left (left rudder peddle down), the inertia in the left tank will
effectively increase the head pressure and force open the left flop valve,
and the left tank will feed fuel. The right tank may have exactly the same
amount of fuel, but its inertia is a way from the flop valve thus its head
pressure is effective less.
The inertia of the fuel in the header tank will react the same - helping
keep the opposite flop valve closed.
Anyway that's what I think happens. A engineer type agreed with me, but I
think he was in a hurry to get to the bar. Would appreciate a back up check
on my theory.
Jim "Pappy" Goolsby
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
et="_blank">http://www.matronics.com/Navigator?Yak-List
tp://forums.matronics.com
_blank">http://www.matronics.com/contribution
--
Byron M. Fox
80 Milland Drive
Mill Valley, CA 94941
415-307-2405
http://www.matronics.com/Navigator?Yak-List
http://forums.matronics.com
http://www.matronics.com/contribution
href="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/
Navigator?Yak-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
Message 15
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| Subject: | Experimental Class |
A question for the legal Eagles out there. I have been told that if an
Experimental Aircraft has a "Certified" engine type, then that engine is
required to undergo all requirements that it normally would have were it
to be installed in a fully certified aircraft.
Ok... Then that brings up the question:
1. Is this true?
2. If it is, then what makes an engine itself "Experimental" ??
I really do not quite understand this aspect....
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of
KingCJ6@aol.com
Sent: Wednesday, May 19, 2010 1:33 AM
The beauty of our "experimental" class!
Dave
Message 16
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| Subject: | Re: Experimental Class |
Depends on the Experimental category the aircraft is licensed in.
Once a engine is installed in a experimental amateur built it would need
to be re-inspected and certified by a approved shop/person/mfg to be re-installed
in a certified aircraft so that in itself tells you it does not need to be
maintained in a approved manner. If so the re-inspection would not be needed.
There are several categories of experimental aircraft some do not require approved
as in amateur built and some do as in testing and certification category's.
The phase 2 can be written in such a way to indicate that requirement also.
Depends on who writes it. Lots of 10-1 pistons installed in engines that
are not approved used in lots of experimental aircraft with once certified engines.
Ad's are not issued "normally" on a homebuilt either.
And the AC43 is the only inspection guide required. The annual inspection in not
a airworthy endorsement. Only a scope and detail inspection.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=298241#298241
Message 17
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Hi Walt,
I may have missed something in reading your e-mail regarding the mod you did to
the check valve - what was the mod? Was it roughing the flapper contacting surface?
I heard in the past that doing so would preclude a "mechanical seal"
of the very smooth mating surfaces.
Also, regarding the vent drain on the bottom of center section (CJ6) - indeed a
mud dubbers (South FL) would fill the vent with grass and ruin the day. To make
the vent drain less hospitable to these critters, about 1/2" above vent bottom
I drilled 2 holes, perpendicular to each other and inserted 2 cotter pins
- creating an "X" cross section. This has worked for me thus far...
Sam Sax
Miami
-----Original Message-----
From: Walter Lannon
Sent: May 19, 2010 5:56 PM
Subject: Re: Yak-List: feul feed
Thanks Dennis
----- Original Message -----
From:
A. Dennis Savarese
To: yak-list@matronics.com
Sent: Wednesday, May 19, 2010 8:19
AM
Subject: Re: Yak-List: feul feed
Walt,
I will see if I can scrounge up some photos of the fuel
junction and flapper valves and send them to you off-list.
Dennis
Message 18
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Hi Sam
The mod you refer to was proposed to me by Joe House .
He suggested that by using rough sandpaper on the flapper valve the
chances of it sticking were minimized . I did that and also took Papy's
advise. After trimmed to level flightin cruisekeep your feet off the
rudders . I have no problem keeping within 2 gal in 2 hrs . Formation
flight is a different challenge .
I am sure Walt will have some good advise .
Terry
.----- Original Message ----
From: Sam Sax <cd001633@mindspring.com>
Sent: Wed, May 19, 2010 10:13:44 PM
Subject: Re: Yak-List: fuel feed
Hi Walt,
I may have missed something in reading your e-mail regarding the mod you did to
the check valve - what was the mod? Was it roughing the flapper contacting surface?
I heard in the past that doing so would preclude a "mechanical seal" of
the very smooth mating surfaces.
Also, regarding the vent drain on the bottom of center section (CJ6) - indeed a
mud dubbers (South FL) would fill the vent with grass and ruin the day. To make
the vent drain less hospitable to these critters, about 1/2" above vent bottom
I drilled 2 holes, perpendicular to each other and inserted 2 cotter pins
- creating an "X" cross section. This has worked for me thus far...
Sam Sax
Miami
-----Original Message-----
From: Walter Lannon
Sent: May 19, 2010 5:56 PM
Subject: Re: Yak-List: feul feed
Thanks Dennis
----- Original Message -----
From:
A. Dennis Savarese
To: yak-list@matronics.com
Sent: Wednesday, May 19, 2010 8:19
AM
Subject: Re: Yak-List: feul feed
Walt,
I will see if I can scrounge up some photos of the fuel
junction and flapper valves and send them to you off-list.
Dennis
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