Today's Message Index:
----------------------
1. 11:10 AM - Re: Oil blurp on start (Bitterlich, Mark G CIV NAVAIR, WD)
2. 02:03 PM - Re: Fuel Imbalance (Re: Yak 52TW Fuel Starvation at near zero G) (John Nolan)
3. 08:13 PM - Re: Fuel Imbalance (Re: Yak 52TW Fuel Starvation at near zero G) (Anthony Savarese)
Message 1
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| Subject: | Re: Oil blurp on start |
With respect, I can't say I agree with Jill's analysis.
The real difference with YAK-50's and 55's and Sukes, is that they are
tail draggers, thus the engines do not sit perpendicular to the ground
but instead are canted slightly backwards. This allows oil to flow
backwards through the intake valve into the intake tubes themselves
more so say than on a 52. Another big factor that can add to this is if
the engine is pulled through backwards when a hydraulic lock is felt.
This will push oil right back out the intake valve again into the tubes.
If you are using single weight oil, say SAE 50 or so, and it gets cold,
this oil can get so thick it is hard to drain. Of course this is most
prevalent in the lower cylinders. This is the whole purpose behind the
intake drains, and of course sometimes yanking plugs out to let the oil
drain.
That being said, if it gets into the intake tubes and gets thick, you
will usually notice it because when you prime the engine, and I mean
REALLY REALLY prime it (as in over prime it on purpose), the raw gas
will NOT flow out the intake tube(s) drain because it is full of oil.
That is your OMG indication to NOT CRANK THE ENGINE. If that happens,
you must get that oil out of there, and that means either heating the
whole engine, or over priming to thin the oil with gas, opening up the
individual intake drains, whatever... to get that oil out of the intake
tubes before cranking.
So.....Part of the solution is having an intake drain kit on the lower
cylinders, leaving that drain open and KEEPING it open when priming for
the next start. If you don't see fuel running out that drain after
priming then you have a very bad incident getting ready to happen, and
you have to take it seriously. Another big advantage is that it is hard
to over-prime with that drain open. Large amounts of excess fuel just
runs right out the drain.
Mark
-----Original Message-----
From: owner-yak-list-server@matronics.com
<owner-yak-list-server@matronics.com> On Behalf Of Bill Culberson
Sent: Monday, December 31, 2018 1:19 AM
Subject: [Non-DoD Source] Re: Yak-List: Oil blurp on start
Yep. It=99s up in the intake tubes. Destroyed an engine that way.
We had a particularly =9Cwet=9D engine that was dumping a
lot of oil during pull through. I pulled 15 blades and still had
hydraulic lock on start. Destroyed the engine. Fortunately I had a
=9Cspare=9D engine on my Yak-55. Wet engines can pull oil up
into intake tubes due to camshaft scavenge during pull through. This
according to Jill.
Bill Culberson
Red Star Aero Services
251/716/8119
> On Dec 30, 2018, at 8:45 PM, Jon Boede <jonboede@hotmail.com> wrote:
>
>
> Anybody ever see an engine that blurps a couple of tablespoons of oil
on start that just wouldn=99t come out no matter how much you
pulled it through by hand??
>
> Jon
>
>
>
>
Message 2
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| Subject: | Re: Fuel Imbalance (Re: Yak 52TW Fuel Starvation at near zero |
G)
Dennis,
Can these be installed on your aftermarket fuel bladders?
John Nolan
On Sat, Dec 15, 2018 at 6:42 AM A. Dennis Savarese <
dsavarese0812@bellsouth.net> wrote:
> FWIW, the single vent system Yak 52's (pre '89) models have a fuel
> imbalance issue as well, especially with full tanks and with the airplane
> sitting on the ramp in the sun. The net of it is the vent system gets
> blocked with fuel. Particularly the vent line on the right tank because
of
> the design of the vent system. As everyone knows, vent lines must be cle
ar
> of fuel in order for fuel to feed. With a blocked vent line, no fuel can
> feed from that tank. That's why we roll the airplane up on one wing and
> fly straight to force the fuel out of the vent line.
>
> BUT there is a solution...a second vent to the tank. This can also apply
> to the CJ. Install this vent check valve on the top of the tank and run
> the vent tube overboard. Most likely location is near the fill port so
> you'll have access to the inside of the tank to tighten the nut on the
> bottom of the vent check valve. The vent check valve is used in race car
s
> and should the race car were to turn over, the vent check valve would
> prevent the fuel from leaking out of the tank. With the vent check valve
> installed, during flight the tank will always have a clear vent line.
>
> Here is a link to where it can be purchased and also a photo of the vent
> check valve installed on the top of a fuel filler plate on a Yak 52 fuel
> bladder. One is required for each fuel tank.
>
> https://fuelsafe.com/thv45/
>
> [image: Inline image]
>
> [image: Inline image]
>
>
> ------------------------------
> *From:* Greg Wrobel <clouddog22@gmail.com>
> *To:* yak-list@matronics.com
> *Sent:* Saturday, December 15, 2018 7:32 AM
> *Subject:* Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>
> Regarding the CJ6. I was one of the fortunate to go to China with members
> of the Southeast region a few months ago. The highlight of our 2 week
> journey was visiting the factory that is currently building the latest CJ
6A
> aircraft (by the way, no significant changes were noted). I will not go
> into the details of the visit or our journey but during our visit to the
> factory, we were able to sit down with the factory manager , CJ6A
> engineers, and production staff. When you ask a question , you do not wan
t
> to ask in a way that they preceive that you are accusing them of a design
> flaw so our wording was carefully chosen. One of our questions related t
o
> fuel imbalance so we carefully asked if they were aware of the fuel
> imbalance that occures during flight or while sitting on a sloped ramp. T
o
> our amazement, they were familiar. To our further amazement, nothing has
> been done to correct the issue! They know it exist but there has been n
o
> changes in design to correct it.
>
> Please realize, our discussions were through interpreters as the only
> Chinese we knew were P=C3=ADji=C7=94 (beer) and B=C3=A1iji=C7=94 (clear
types of alchohol)
> pronounced pee-joe and bye-joe respectively. Ok then, you have now been
> enlightened to some important Chinese words of the day. In any case, we
> are not sure if they truly understood our question or we truly understo
od
> their answer but there you have it.
>
> Now what does this have to do with engine hesitation at the top of a loop
> in a YAK52.....absolutely nothing! Just seems we were beating flapper
> valves to death in a CJ and went astray. We have installed elaborate
> venting systems in our CJ's to fix fuel imbalance and have all these
> questions and theories. Maybe the Chinese are telling the truth on this
> one. The CJ has a fuel imbalance issue created by flappers/ check valves
> or gremlins and apparently it is not going away. From my personal
> expierence, I keep the fuel 3/4" - 1" below the rear lip of the fill port
> as mentioned in the Chinese Flight Manual. This equates to 1 gallon less
in
> the tanks versus topping it off. Also attempting to fly wings level and
in
> trim (thats a full time, max concentration effort for me by the way) and
> most of the time, my fuel burns symmetrical but not always. Apparently I
'm
> not concentrating hard enough. Darn flapper valves or are they flipper
> valves? Who knows!
>
> On Fri, Dec 14, 2018, 16:07 Walter Lannon <wlannon@shaw.ca wrote:
>
> A few thoughts on fuel flow problems in the CJ;
>
> Dennis, would I be correct in assuming that each flapper valve outlet of
> the
> fuel junction would go to the corresponding side of the Yak 52 header tan
k?
> If so that is functionally the same as the CJ where the flapper valves ar
e
> mounted in the header tank walls.
>
> In the early CJ days there were numerous problems with flapper valves stu
ck
> closed due to evaporating Chinese fuel effectively gluing them in place.
> Probably could repeat with auto gas and long enough storage time. Have n
ot
> heard of any such problem here with avgas.
> Also many problems of blocked (or partially blocked) fuel and vent lines
> due
> dead bugs and debris. Many had sat for years after being discarded at or
> near their 4000 hr. life limit.
> Dented, kinked and otherwise damaged fuel and vent lines also contribute
> immensely to unequal fuel flow.
>
> On flapper valves; There are 3 of these in the CJ. One is mounted in t
he
> line from the header tank to the fuel pump for the sole purpose
> of preventing back flow of wobble pump fuel which would otherwise just
> re-circulate through the wobble pump. It is subject to substantial openi
ng
> pressure from the wobble pump. Even Chinese fuel glue could not keep it
> closed. An excellent design for the application.
>
> The other two are identical but are used in an application that requires
a
> slightly different design which moves with fuel flow at minimal
> differential
> pressure. These are designed to require a significantly higher
> differential
> pressure to open (significantly here is a relative term, if one could
> measure the pressures involved it would likely be in milligrams/sq. cm. )
.
> This is evident on inspection:- the area of valve opening surface is
> about
> 1/4 that of the surface holding it closed.
> In theory, with perfect trim and absolutely no turbulence whatsoever this
> valve would require one full and one empty tank to open.
>
> So; I have modified the valves in mine by removing valve seat material to
> reduce the surface contact area from 100% to a near line contact.
> (actually,
> since this is a hand filing operation) about a 0.020' to 0.030" contact
> band. This allows the normal closing pressure to also react on the
> opening
> side of the flapper resulting in a much closer balance between opening an
d
> closing forces. See attached photos.
>
> I normally never see a fuel imbalance in excess of 2 to 4 lts. except whe
n
> I
> try to do good slow (or point) rolls. In this case the valve flappers
> are
> are doing just that, flapping! After a few I see imbalance up to 15 lts
.
> or so which returns to normal in a few minutes of level flight.
>
> The valves alone are not the whole problem, I can not stress how
> important
> the condition of the fuel and vent lines are. Both damage, internal
> contamination and leakage are critical. I have spent days during CJ
> restorations with a hose, hot water, dish washer soap and shop air gettin
g
> crap out of the lines. If you are going to do this be sure both ends of
> all
> lines are disconnected. You don't want to blow up the the mains or
> header
> tank in the process.
>
> I had a good example of what a minor discrepancy can do to this fuel
> system.
> A few years back on about 1 hr. flight home checked fuel gauges and
> shocked
> to see a 20 + lt. imbalance. Checking the vent system I found one
> connector
> hose in the RH wing joint area had slipped off! (I had used all new hose
> but no clamps thinking they were tight enough). Dumb! But this
> relatively
> small vent pressure change made a huge difference to the entire fuel
> system.
>
> These valves (In Western terms normally called a vent valve) MUST be
> mounted
> with the flapper hinge at the top! This requirement is a problem for the
> Chinese valve as mounted in the header tank since it is threaded into a
> welded fitting on the tank wall with a sealing washer.
> So; Three things have have to come together at precisely the same time
> and
> place. The valve is at the top, the torque is correct and the sealing
> washer
> is exactly the right thickness. This of course is mission impossible.
>
> Enough for now.
> Walt
>
>
> -----Original Message-----
> From: JON
> Sent: Thursday, December 13, 2018 2:51 PM
> To: dsavarese0812@bellsouth.net ; yak-list@matronics.com
> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>
> Thanks Dennis.
>
> I'm thinking these "flapper" valves do not exist on the CJ. I say this
> because when I part my CJ on a slope fuel will drain from the upslope tan
k
> to the down slope tank.
>
> Still leaving the question possed eariler about the header tank. JB
>
>
> Sent from Xfinity Connect Application
>
> -----Original Message-----
>
> From: dsavarese0812@bellsouth.net
> To: yak-list@matronics.com
> Sent: 2018-12-13 4:37:58 PM
> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>
> <dsavarese0812@bellsouth.net>
>
> I don=99t know the answer to this situation on the CJ. The 52 has
a fuel
> junction below the front seat which has flapper valves on each end of the
> junction where the hoses from the left and right fuel tanks attach. The
> flapper valves are design to move inward or away from the fuel tank. Thei
r
> purpose is to prevent fuel from moving from one tank to the other. HOWEVE
R,
> if one of the flapper valves were to bind or stick closed, it would preve
nt
> fuel from flowing into the fuel junction from that tank. Should this occu
r,
> one fuel tank could be completely emptied without the other tank ever
> draining a drop.
>
> Now if the CJ=99s header tank has anything similar to the 52
=99s fuel
> junction,
> a stuck or sticking flapper valve, it could definitely cause the symptom
> described.
> Dennis
>
> Sent from my iPad
>
> > On Dec 13, 2018, at 3:32 PM, JON BLAKE <saber369@comcast.net> wrote:
> >
> >
> > While we are on the subject of fuel flow, header tanks, etc. I have a
> > question about the CJ fuel system.
> >
> > Not long after I bought my CJ I was returning home from a full day of
> > formation flying. My CJ, not unlike many others, has an asymmetrical
> fuel
> > feed issue meaning it drains from one tank more than the other based on
> > trim or rather imbalanced trim. On this day, as I neared home, the rig
ht
> > tank had about 30 liters indicated and the left tank was approaching
> zero.
> > Just as I arrived at the initial entry point over the runway with the
> left
> > fuel low light on steady for a few minutes, the engine quit. While thi
s
> > sudden silence quickly got my attention, I wasn't all that worried
> because
> > I was over the runway. I entered a left bank planning to continue with
a
> > circling approach and land with the engine out, but then after about 3-
5
> > seconds in the left bank the engine caught up and continued operating
> > normally. I landed immediately without any further issues.
> >
> > Being an FNG to the CJ back then, I started calling some of the old
> timers
> > asking their opinions. All agreed that it was most likely a fuel issue
,
> > or lack of fuel on one side and as long as I had gas in both tanks I
> > shouldn't experience any additional problems. So, with ample gas in bo
th
> > tanks, I did several minutes of ground test runs at varying RPMs;
> > high-speed taxi checks and after an hour or so took off and completed a
> > successful test flight.
> >
> > So the simple question is... Why did this happen? I repeated the
> scenario
> > a few years later; this time on purpose and over the long runway with t
he
> > same results. I replicated the same conditions with one exception...
> when
> > the engine "quit" I delayed entering a turn for a few seconds (seemed
> like
> > hours with all that quite in front of me) to see what would happen.
> After
> > a short delay, I entered the left bank and sure enough, the engine
> > regained full RPM with no additional issues.
> >
> > Why did this happen? The main tanks feed the header tank, so in theory
,
> > the fuel tank with gas should continue to feed the header regardless -
> > right? I would think that the header tank, being center-line to the
> > engine, would continue to drain fuel from the tank with gas and feed fu
el
> > to the engine regardless of any delta in fuel tank quantities.
> >
> > After I repeated the incident on purpose, I once again called around fo
r
> > opinions and the one thing that I will remember and have passed on to
> FNGs
> > is something Doug Sapp said... "There are a lot of CJs laying on their
> > bellies in corn fields with 60 liters in one side and zero in the other
."
> >
> > I know many will give opinions on the asymmetrical fuel flow, but that'
s
> > not the question... the header tank is the question. And for those who
> > want to tell me about setting proper trim, I've got the trim tabs well
> > balanced, but still have to "step on the fuller tank" to get it back to
> > "30-30" in both tanks. Help me understand the header tank thing and we
> > can talk about trim later please.
> >
> > Jon Blake
> > Saber369@comcast.net
> >
> >
> >> On December 13, 2018 at 12:59 PM Mark Davis <markdavis@wbsnet.org>
> wrote:
> >>
> >>
> >>
> >> What everyone is possibly not considering is that the flop tube is hel
d
> >> in
> >> good fuel by either positive g or negative g. O g where the issue aro
se
> >> could have the flop tube out of the fuel if sustained for a long enoug
h
> >> time
> >> of the hose is becoming somewhat stiff.
> >>
> >> Mark Davis
> >> N44K
> >>
> >>
> >> -----Original Message-----
> >> From: owner-yak-list-server@matronics.com
> >> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lanno
n
> >> Sent: Thursday, December 13, 2018 11:19 AM
> >> To: yak-list@matronics.com
> >> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
> >>
> >>
> >> No I am not suggesting anything of the sort. If you would re-read my
> >> second paragraph you will understand that.
> >>
> >> My post was a response to your's implying the amount if fuel in the
> main
> >> tanks was enough to to ensure this hesitation should not have happened
.
> >> My response was to simply advise you that the amount of fuel in the
> mains
> >> was immaterial and the problem lies somewhere in the fuel management
> >> system.
> >>
> >> Cheers;
> >> Walt
> >>
> >> -----Original Message-----
> >> From: ggtyler
> >> Sent: Wednesday, December 12, 2018 11:41 PM
> >> To: yak-list@matronics.com
> >> Subject: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
> >>
> >>
> >> Walt, I'm pretty sure I have a decent handle on the fuel system. I've
> got
> >> a
> >> header tank under the feet, with a flop tube, and then the fuel globe
on
> >> the
> >>
> >> front side of the firewall and a pressure carb. I was under the
> >> impression
> >> that this system was specifically designed to supply fuel for even a
> >> couple
> >> minutes of sustained inverted flight.
> >>
> >> Are you suggesting that fuel starvation during aerobatics could be
> >> considered normal in a Yak 52? Sergei didn't seem to think so. He's go
t
> >> thousands of hours in the Yak 52 and the first words out of his mouth
> >> were
> >> "that's not good".
> >>
> >> I'm trying to assess if this has been an occasional rare occurrence fo
r
> >> other Yak owners, and what the possible solutions might be.
> >>
> >>
> >>
> >>
> >> Read this topic online here:
> >>
> >> http://forums.matronics.com/viewtopic.php?p=486270#486270
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> ---
> >> This email has been checked for viruses by Avast antivirus software.
> >> https://www.avast.com/antivirus
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> >
>
>
Message 3
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| Subject: | Re: Fuel Imbalance (Re: Yak 52TW Fuel Starvation at near zero |
G)
Fuel bladders are no longer available. If you have them, yes they can be ins
talled in the filler plate.
Dennis
Sent from my iPhone
> On Jan 7, 2019, at 5:01 PM, John Nolan <johnrobertnolan@gmail.com> wrote:
>
> Dennis,
>
> Can these be installed on your aftermarket fuel bladders?
>
> John Nolan
>
>> On Sat, Dec 15, 2018 at 6:42 AM A. Dennis Savarese <dsavarese0812@bellsou
th.net> wrote:
>> FWIW, the single vent system Yak 52's (pre '89) models have a fuel imbala
nce issue as well, especially with full tanks and with the airplane sitting o
n the ramp in the sun. The net of it is the vent system gets blocked with f
uel. Particularly the vent line on the right tank because of the design of t
he vent system. As everyone knows, vent lines must be clear of fuel in orde
r for fuel to feed. With a blocked vent line, no fuel can feed from that ta
nk. That's why we roll the airplane up on one wing and fly straight to forc
e the fuel out of the vent line.
>>
>> BUT there is a solution...a second vent to the tank. This can also apply
to the CJ. Install this vent check valve on the top of the tank and run th
e vent tube overboard. Most likely location is near the fill port so you'll
have access to the inside of the tank to tighten the nut on the bottom of t
he vent check valve. The vent check valve is used in race cars and should t
he race car were to turn over, the vent check valve would prevent the fuel f
rom leaking out of the tank. With the vent check valve installed, during fl
ight the tank will always have a clear vent line.
>>
>> Here is a link to where it can be purchased and also a photo of the vent c
heck valve installed on the top of a fuel filler plate on a Yak 52 fuel blad
der. One is required for each fuel tank.
>>
>> https://fuelsafe.com/thv45/
>>
>> <Vent valve.JPG>
>>
>> <photo 2.JPG>
>>
>>
>>
>>
>> From: Greg Wrobel <clouddog22@gmail.com>
>> To: yak-list@matronics.com
>> Sent: Saturday, December 15, 2018 7:32 AM
>> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>>
>> Regarding the CJ6. I was one of the fortunate to go to China with members
of the Southeast region a few months ago. The highlight of our 2 week journ
ey was visiting the factory that is currently building the latest CJ6A aircr
aft (by the way, no significant changes were noted). I will not go into the d
etails of the visit or our journey but during our visit to the factory, we w
ere able to sit down with the factory manager , CJ6A engineers, and producti
on staff. When you ask a question , you do not want to ask in a way that the
y preceive that you are accusing them of a design flaw so our wording was ca
refully chosen. One of our questions related to fuel imbalance so we carefu
lly asked if they were aware of the fuel imbalance that occures during flig
ht or while sitting on a sloped ramp. To our amazement, they were familiar.
To our further amazement, nothing has been done to correct the issue! The
y know it exist but there has been no changes in design to correct it.
>>
>> Please realize, our discussions were through interpreters as the only Ch
inese we knew were P=C3=ADji=C7=94 (beer) and B=C3=A1iji=C7=94 (clear type
s of alchohol) pronounced pee-joe and bye-joe respectively. Ok then, you hav
e now been enlightened to some important Chinese words of the day. In any c
ase, we are not sure if they truly understood our question or we truly und
erstood their answer but there you have it.
>>
>> Now what does this have to do with engine hesitation at the top of a loop
in a YAK52.....absolutely nothing! Just seems we were beating flapper valve
s to death in a CJ and went astray. We have installed elaborate venting syst
ems in our CJ's to fix fuel imbalance and have all these questions and theor
ies. Maybe the Chinese are telling the truth on this one. The CJ has a fue
l imbalance issue created by flappers/ check valves or gremlins and apparen
tly it is not going away. =46rom my personal expierence, I keep the fuel 3/
4" - 1" below the rear lip of the fill port as mentioned in the Chinese Flig
ht Manual. This equates to 1 gallon less in the tanks versus topping it off
. Also attempting to fly wings level and in trim (thats a full time, max con
centration effort for me by the way) and most of the time, my fuel burns sy
mmetrical but not always. Apparently I'm not concentrating hard enough. Da
rn flapper valves or are they flipper valves? Who knows!
>>
>> On Fri, Dec 14, 2018, 16:07 Walter Lannon <wlannon@shaw.ca wrote:
>> A few thoughts on fuel flow problems in the CJ;
>>
>> Dennis, would I be correct in assuming that each flapper valve outlet of t
he
>> fuel junction would go to the corresponding side of the Yak 52 header tan
k?
>> If so that is functionally the same as the CJ where the flapper valves ar
e
>> mounted in the header tank walls.
>>
>> In the early CJ days there were numerous problems with flapper valves stu
ck
>> closed due to evaporating Chinese fuel effectively gluing them in place.
>> Probably could repeat with auto gas and long enough storage time. Have n
ot
>> heard of any such problem here with avgas.
>> Also many problems of blocked (or partially blocked) fuel and vent lines d
ue
>> dead bugs and debris. Many had sat for years after being discarded at or
>> near their 4000 hr. life limit.
>> Dented, kinked and otherwise damaged fuel and vent lines also contribute
>> immensely to unequal fuel flow.
>>
>> On flapper valves; There are 3 of these in the CJ. One is mounted in t
he
>> line from the header tank to the fuel pump for the sole purpose
>> of preventing back flow of wobble pump fuel which would otherwise just
>> re-circulate through the wobble pump. It is subject to substantial openi
ng
>> pressure from the wobble pump. Even Chinese fuel glue could not keep it
>> closed. An excellent design for the application.
>>
>> The other two are identical but are used in an application that requires a
>> slightly different design which moves with fuel flow at minimal different
ial
>> pressure. These are designed to require a significantly higher different
ial
>> pressure to open (significantly here is a relative term, if one could
>> measure the pressures involved it would likely be in milligrams/sq. cm. )
.
>> This is evident on inspection:- the area of valve opening surface is abo
ut
>> 1/4 that of the surface holding it closed.
>> In theory, with perfect trim and absolutely no turbulence whatsoever this
>> valve would require one full and one empty tank to open.
>>
>> So; I have modified the valves in mine by removing valve seat material to
>> reduce the surface contact area from 100% to a near line contact. (actual
ly,
>> since this is a hand filing operation) about a 0.020' to 0.030" contact
>> band. This allows the normal closing pressure to also react on the openi
ng
>> side of the flapper resulting in a much closer balance between opening an
d
>> closing forces. See attached photos.
>>
>> I normally never see a fuel imbalance in excess of 2 to 4 lts. except whe
n I
>> try to do good slow (or point) rolls. In this case the valve flappers a
re
>> are doing just that, flapping! After a few I see imbalance up to 15 lts
.
>> or so which returns to normal in a few minutes of level flight.
>>
>> The valves alone are not the whole problem, I can not stress how import
ant
>> the condition of the fuel and vent lines are. Both damage, internal
>> contamination and leakage are critical. I have spent days during CJ
>> restorations with a hose, hot water, dish washer soap and shop air gettin
g
>> crap out of the lines. If you are going to do this be sure both ends of a
ll
>> lines are disconnected. You don't want to blow up the the mains or head
er
>> tank in the process.
>>
>> I had a good example of what a minor discrepancy can do to this fuel syst
em.
>> A few years back on about 1 hr. flight home checked fuel gauges and shock
ed
>> to see a 20 + lt. imbalance. Checking the vent system I found one connec
tor
>> hose in the RH wing joint area had slipped off! (I had used all new hose
>> but no clamps thinking they were tight enough). Dumb! But this relative
ly
>> small vent pressure change made a huge difference to the entire fuel syst
em.
>>
>> These valves (In Western terms normally called a vent valve) MUST be moun
ted
>> with the flapper hinge at the top! This requirement is a problem for the
>> Chinese valve as mounted in the header tank since it is threaded into a
>> welded fitting on the tank wall with a sealing washer.
>> So; Three things have have to come together at precisely the same time a
nd
>> place. The valve is at the top, the torque is correct and the sealing was
her
>> is exactly the right thickness. This of course is mission impossible.
>>
>> Enough for now.
>> Walt
>>
>>
>>
>>
>> -----Original Message-----
>> From: JON
>> Sent: Thursday, December 13, 2018 2:51 PM
>> To: dsavarese0812@bellsouth.net ; yak-list@matronics.com
>> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>>
>> Thanks Dennis.
>>
>> I'm thinking these "flapper" valves do not exist on the CJ. I say this
>> because when I part my CJ on a slope fuel will drain from the upslope tan
k
>> to the down slope tank.
>>
>> Still leaving the question possed eariler about the header tank. JB
>>
>>
>> Sent from Xfinity Connect Application
>>
>> -----Original Message-----
>>
>> From: dsavarese0812@bellsouth.net
>> To: yak-list@matronics.com
>> Sent: 2018-12-13 4:37:58 PM
>> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>>
>> <dsavarese0812@bellsouth.net>
>>
>> I don=99t know the answer to this situation on the CJ. The 52 has a
fuel
>> junction below the front seat which has flapper valves on each end of the
>> junction where the hoses from the left and right fuel tanks attach. The
>> flapper valves are design to move inward or away from the fuel tank. Thei
r
>> purpose is to prevent fuel from moving from one tank to the other. HOWEVE
R,
>> if one of the flapper valves were to bind or stick closed, it would preve
nt
>> fuel from flowing into the fuel junction from that tank. Should this occu
r,
>> one fuel tank could be completely emptied without the other tank ever
>> draining a drop.
>>
>> Now if the CJ=99s header tank has anything similar to the 52
=99s fuel junction,
>> a stuck or sticking flapper valve, it could definitely cause the symptom
>> described.
>> Dennis
>>
>> Sent from my iPad
>>
>> > On Dec 13, 2018, at 3:32 PM, JON BLAKE <saber369@comcast.net> wrote:
>> >
>> >
>> > While we are on the subject of fuel flow, header tanks, etc. I have a
>> > question about the CJ fuel system.
>> >
>> > Not long after I bought my CJ I was returning home from a full day of
>> > formation flying. My CJ, not unlike many others, has an asymmetrical f
uel
>> > feed issue meaning it drains from one tank more than the other based on
>> > trim or rather imbalanced trim. On this day, as I neared home, the rig
ht
>> > tank had about 30 liters indicated and the left tank was approaching ze
ro.
>> > Just as I arrived at the initial entry point over the runway with the l
eft
>> > fuel low light on steady for a few minutes, the engine quit. While thi
s
>> > sudden silence quickly got my attention, I wasn't all that worried beca
use
>> > I was over the runway. I entered a left bank planning to continue with
a
>> > circling approach and land with the engine out, but then after about 3-
5
>> > seconds in the left bank the engine caught up and continued operating
>> > normally. I landed immediately without any further issues.
>> >
>> > Being an FNG to the CJ back then, I started calling some of the old tim
ers
>> > asking their opinions. All agreed that it was most likely a fuel issue
,
>> > or lack of fuel on one side and as long as I had gas in both tanks I
>> > shouldn't experience any additional problems. So, with ample gas in bo
th
>> > tanks, I did several minutes of ground test runs at varying RPMs;
>> > high-speed taxi checks and after an hour or so took off and completed a
>> > successful test flight.
>> >
>> > So the simple question is... Why did this happen? I repeated the scena
rio
>> > a few years later; this time on purpose and over the long runway with t
he
>> > same results. I replicated the same conditions with one exception... w
hen
>> > the engine "quit" I delayed entering a turn for a few seconds (seemed l
ike
>> > hours with all that quite in front of me) to see what would happen. Af
ter
>> > a short delay, I entered the left bank and sure enough, the engine
>> > regained full RPM with no additional issues.
>> >
>> > Why did this happen? The main tanks feed the header tank, so in theory
,
>> > the fuel tank with gas should continue to feed the header regardless -
>> > right? I would think that the header tank, being center-line to the
>> > engine, would continue to drain fuel from the tank with gas and feed fu
el
>> > to the engine regardless of any delta in fuel tank quantities.
>> >
>> > After I repeated the incident on purpose, I once again called around fo
r
>> > opinions and the one thing that I will remember and have passed on to FN
Gs
>> > is something Doug Sapp said... "There are a lot of CJs laying on their
>> > bellies in corn fields with 60 liters in one side and zero in the other
."
>> >
>> > I know many will give opinions on the asymmetrical fuel flow, but that'
s
>> > not the question... the header tank is the question. And for those who
>> > want to tell me about setting proper trim, I've got the trim tabs well
>> > balanced, but still have to "step on the fuller tank" to get it back to
>> > "30-30" in both tanks. Help me understand the header tank thing and we
>> > can talk about trim later please.
>> >
>> > Jon Blake
>> > Saber369@comcast.net
>> >
>> >
>> >> On December 13, 2018 at 12:59 PM Mark Davis <markdavis@wbsnet.org> wro
te:
>> >>
>> >>
>> >>
>> >> What everyone is possibly not considering is that the flop tube is hel
d
>> >> in
>> >> good fuel by either positive g or negative g. O g where the issue aro
se
>> >> could have the flop tube out of the fuel if sustained for a long enoug
h
>> >> time
>> >> of the hose is becoming somewhat stiff.
>> >>
>> >> Mark Davis
>> >> N44K
>> >>
>> >>
>> >> -----Original Message-----
>> >> From: owner-yak-list-server@matronics.com
>> >> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Walter Lanno
n
>> >> Sent: Thursday, December 13, 2018 11:19 AM
>> >> To: yak-list@matronics.com
>> >> Subject: Re: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>> >>
>> >>
>> >> No I am not suggesting anything of the sort. If you would re-read my
>> >> second paragraph you will understand that.
>> >>
>> >> My post was a response to your's implying the amount if fuel in the m
ain
>> >> tanks was enough to to ensure this hesitation should not have happened
.
>> >> My response was to simply advise you that the amount of fuel in the ma
ins
>> >> was immaterial and the problem lies somewhere in the fuel management
>> >> system.
>> >>
>> >> Cheers;
>> >> Walt
>> >>
>> >> -----Original Message-----
>> >> From: ggtyler
>> >> Sent: Wednesday, December 12, 2018 11:41 PM
>> >> To: yak-list@matronics.com
>> >> Subject: Yak-List: Re: Yak 52TW Fuel Starvation at near zero G
>> >>
>> >>
>> >> Walt, I'm pretty sure I have a decent handle on the fuel system. I've g
ot
>> >> a
>> >> header tank under the feet, with a flop tube, and then the fuel globe o
n
>> >> the
>> >>
>> >> front side of the firewall and a pressure carb. I was under the
>> >> impression
>> >> that this system was specifically designed to supply fuel for even a
>> >> couple
>> >> minutes of sustained inverted flight.
>> >>
>> >> Are you suggesting that fuel starvation during aerobatics could be
>> >> considered normal in a Yak 52? Sergei didn't seem to think so. He's go
t
>> >> thousands of hours in the Yak 52 and the first words out of his mouth
>> >> were
>> >> "that's not good".
>> >>
>> >> I'm trying to assess if this has been an occasional rare occurrence fo
r
>> >> other Yak owners, and what the possible solutions might be.
>> >>
>> >>
>> >>
>> >>
>> >> Read this topic online here:
>> >>
>> >> http://forums.matronics.com/viewtopic.php?p=486270#486270
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> ---
>> >> This email has been checked for viruses by Avast antivirus software.
>> >> https://www.avast.com/antivirus
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>> >
>> >
>>
>>
>>
>>
>>
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