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pennington.construction.i
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 Posted: Sun Jul 07, 2019 11:29 am Post subject: CJ6 fuel management: What happens when... |
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Question:
Do you have the stock steel tanks in your CJ or the newer long range bladders?
On Sun, Jul 7, 2019 at 3:13 PM chrisunrau <cunrau(at)gmail.com (cunrau(at)gmail.com)> wrote:
| Quote: | --> Yak-List message posted by: "chrisunrau" <cunrau(at)gmail.com (cunrau(at)gmail.com)>
Have been flying my CJ6 for nearly a year and despite best attempts to adjust rudder trim, still can't get fuel to feed evenly from both tanks. Consistently runs down the LH tank more than the RH. On cross countries it's easier to manage by flying RH wing high; but just bombing around locally that's not always practical. Question is, will the LH tank run completely dry before the other one, and if so, what happens? Will the engine die, or will it just feed fuel from the tank that has the gas?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=490109#490109
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wlannon(at)shaw.ca
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| Posted: Sun Jul 07, 2019 12:43 pm Post subject: CJ6 fuel management: What happens when... |
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Hi Chris;
This is a common problem with CJ's, many of which are just stored outside
with no preparation when their military service life expires.
The vent system is a primary suspect for various insects and the remains
thereof as well as physical damage from careless handling; sharp bends and
kink's etc. The only effective means I have found for internal cleaning is
hot, soapy water, and lots of it, under some pressure. Before starting this
process you must ensure the vent lines are disconnected from all three fuel
tanks and tank fittings are capped for obvious reasons.
One reason being that any shop air pressure will destroy the fuel tanks!!
Good idea to tie cloth part's bags on one end of each line to see results.
I start with a soap solution sprayed in with my shop air gun, let soak for a
bit then lots of hot water. You may want to do this two or three times over
a day or two. Once satisfied blow out with shop air and allow lots of time
for drying.
Visually inspect every inch of vent lines and fuel delivery lines between
tanks for physical damage like kink's. Most likely area for this damage, as
well as interconnecting hose condition, is at the wing joints. Correct
everything that looks like a vent (or fuel flow) restriction.
Walt
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wlannon(at)shaw.ca
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| Posted: Sun Jul 07, 2019 1:22 pm Post subject: CJ6 fuel management: What happens when... |
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Chris;
There has been more than one report over the years of CJ engine failure with
one full tank. If the vent system for that tank is fully blocked the fuel
is probably going nowhere! But then again I have seen (though not CJ!) the
bottom of the fuel tank sucked right up to the filler cap.
The RH vent system being longer than the LH may be easier blocked than the
left. Of course that all depends on the number and size of insect residue.
The general condition of the header tank and in particular the condition of
the flapper valves can also have a negative effect on fuel flow though vent
and flow problems should be eliminated first.
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pennington.construction.i
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| Posted: Sun Jul 07, 2019 2:09 pm Post subject: CJ6 fuel management: What happens when... |
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Chris.
Keeping the vent system clear is key as Walt has said. This past winter I pulled my header tank and made sure the flapper valves worked freely which one did not, t would hang open or hang closed. The other flopped open and closed at it should.
Also after talking to Doug, he suggested and I think this helped a lot.
Make sure when you artificial horizon in flat and your ball is centered your plane is flying straight and level. I put my plane on the jacks and leveled the plane and the ball was not centered and the horizon was not flat.
Adjusted the instruments and that along with the maintenance on the vent system I am not having nearly the problem I had in the past.
Hope this helps.
Mark
N621CJ
On Sun, Jul 7, 2019 at 5:27 PM Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
Chris;
There has been more than one report over the years of CJ engine failure with
one full tank. If the vent system for that tank is fully blocked the fuel
is probably going nowhere! But then again I have seen (though not CJ!) the
bottom of the fuel tank sucked right up to the filler cap.
The RH vent system being longer than the LH may be easier blocked than the
left. Of course that all depends on the number and size of insect residue.
The general condition of the header tank and in particular the condition of
the flapper valves can also have a negative effect on fuel flow though vent
and flow problems should be eliminated first.
--
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Clouddog
Joined: 02 Jun 2016
Posts: 116
Location: Lebanon, TN
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| Posted: Sun Jul 07, 2019 4:12 pm Post subject: CJ6 fuel management: What happens when... |
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Chris,
Blocked vent valves can be blocked by critters or filling you fuel tank all the way to the rim. Somewhere I read to keep the fuel 3/4 - 1" below the back fuel filler lip. I took an inspection mirror and looked in the tank where the vent system is at the top of the tank. With full fuel to the rim, the vent is completely submerged in fuel. I then lowered the fuel to the 3/4 - 1" below the rear lip and looked again and low and behold, the vent was in clear air. I then topped it off and probably put 1/2 - 3/4 gallon (per tank) of fuel to get it back to the rim. So with all that said, I keep my fuel 1" +/- below the rear rims of the tanks sand for safety, I plan on 38 gallons of available fuel ( I have the standard 40 gallon tanks). Of course the keeping it level helps along with all the other great suggestions.
Greg "Clouddog" Wrobel
On Sun, Jul 7, 2019, 14:13 chrisunrau <cunrau(at)gmail.com (cunrau(at)gmail.com)> wrote:
| Quote: | --> Yak-List message posted by: "chrisunrau" <cunrau(at)gmail.com (cunrau(at)gmail.com)>
Have been flying my CJ6 for nearly a year and despite best attempts to adjust rudder trim, still can't get fuel to feed evenly from both tanks. Consistently runs down the LH tank more than the RH. On cross countries it's easier to manage by flying RH wing high; but just bombing around locally that's not always practical. Question is, will the LH tank run completely dry before the other one, and if so, what happens? Will the engine die, or will it just feed fuel from the tank that has the gas?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=490109#490109
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-Matt Dralle, List Admin.
rel="noreferrer noreferrer" target="_blank">http://www.matronics.com/contribution
===========
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chrisunrau
Joined: 06 Sep 2018
Posts: 4
Location: Winkler, Manitoba Canada
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| Posted: Sun Jul 07, 2019 6:32 pm Post subject: Re: CJ6 fuel management: What happens when... |
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Stock fuel tanks.
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wlannon(at)shaw.ca
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| Posted: Sun Jul 07, 2019 7:43 pm Post subject: CJ6 fuel management: What happens when... |
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Hi Mark,
Since you have had the flapper valves out you are familiar with the major challenge presented with their re-installation. The probability of finding a new crush washer of exactly the correct thickness to ensure adequate torque to avoid fuel leakage and at the same moment position the flapper valve hinge exactly at the top where it must be for correct operation.
There is no info given on this in any of the CJ manuals I have seen but aircraft fuel and /or fuel vent systems commonly utilize these valves. They are designed to operate only with the hinge at the top. Deviation beyond +/- 5 deg. is not acceptable. The valves are clearly marked with the required position but of course on the CJ that marking is in Chinese!
There are in fact three of these valves in the CJ. The one location where the valve is used exactly as it was designed for is the fuel line from the header tank to the eng. driven fuel pump. In this location it prevents wobble pump fuel from being pumped back to the header tank and re-sucked by the pump. It works perfectly here due to the positive differential in pressures on either side.
In the header tank it sort of half-ass works but the valve was not designed for this particular purpose. If you take a good look at this you will see that the closing pressure works on a valve surface approx. twice the area of the opposing opening pressure. In theory this means that in a probably mythical flight with zero turbulence one tank would have to be empty before the other tank could even begin to feed.
Add that to contaminated and or damaged vent system and you have a recipe for problems.
I have modified my valves to reduce this differential so that the valves work correctly for this particular function.
I rarely ever see fuel differentials in excess of 3-4 litres except after slow (or point) rolls where there is some negative “G”. In this case the header tank and valves are totally confused and fuel is just running back and forth. Might have 10–15 litre differential which returns to normal in about 5 mins. of level flight.
See attached. First 3 pics are original, next 3 after modification. I have done a few for others but probably not worth the effort unless the vent system is in good order.
Walt
From: Mark Pennington (pennington.construction.inc.1(at)gmail.com)
Sent: Sunday, July 07, 2019 3:07 PM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: CJ6 fuel management: What happens when...
Chris.
Keeping the vent system clear is key as Walt has said. This past winter I pulled my header tank and made sure the flapper valves worked freely which one did not, t would hang open or hang closed. The other flopped open and closed at it should.
Also after talking to Doug, he suggested and I think this helped a lot.
Make sure when you artificial horizon in flat and your ball is centered your plane is flying straight and level. I put my plane on the jacks and leveled the plane and the ball was not centered and the horizon was not flat.
Adjusted the instruments and that along with the maintenance on the vent system I am not having nearly the problem I had in the past.
Hope this helps.
Mark
N621CJ
On Sun, Jul 7, 2019 at 5:27 PM Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
Chris;
There has been more than one report over the years of CJ engine failure with
one full tank. If the vent system for that tank is fully blocked the fuel
is probably going nowhere! But then again I have seen (though not CJ!) the
bottom of the fuel tank sucked right up to the filler cap.
The RH vent system being longer than the LH may be easier blocked than the
left. Of course that all depends on the number and size of insect residue.
The general condition of the header tank and in particular the condition of
the flapper valves can also have a negative effect on fuel flow though vent
and flow problems should be eliminated first.
--
| | - The Matronics Yak-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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