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#1
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Individual Fuel Tank (Cell) Capacity
Does anyone know the number of gallons each of the four tank cells hold in a 1977 T337G (P337)??
Reason for this information is in determining where a leak has developed in the inboard tank. When fuel capacity was reduced from having topped off, down to 38 to 40 gallons, the leak ceased. I surmise the fuel leveled out between the inboard and the immediate outboard tank from the boom. The 1975 and later year P337's have four individual tanks, but the question is, what is the capacity of each one of them... obviously the inboard tank is larger than the rest. Got numbers? SkyKing 
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#2
10-20-02, 03:55 PM
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Hmmmm.... well I though you said...
I though you had opened up the inspection covers under the wing.. and looked at where the leaking was coming from and determined that it was from the inboard tank.. area...
To answer your question... the tanks look smaller as you go out to the wing tip... with the inboard tank between the boom being the largest.. and having the turning tank built inside... the next one out is not as big the first as it is much thinner... and finally the third tank is still smaller... those tanks make up the smaller fuel tanks on the early skymasters... or about 45 gallons each side... so with a little dudction you can divide each into the 45 and come up with about a good ball park figure... giving the inboard tank a rating of say 17 gallons... the next 15...makes the final one 13 gallons... but, .... You can't determine the leak just from that... as you look at the wing... it will not fill the first tank then the second and finally the third.. they will all start coming up as you fill the wing... so until just about the time 3 inboard tanks get full you first tank is going to be totally full... kinda thing... Hope this helps G.M> GMAs
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#3
10-21-02, 01:25 AM
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4 Tanks per side
Gmas,
Well, yes, and no. We did open up the bottom inspection panels and have isolated the "probable" area of leakage to the inboard tank, aft inboard side, and I surmise because of the stains that can be seen with a mirror and flashlight directed via one of the rib holes forward of the hose connections to the fuselage that the leak is somewhere above the middle of the tank seem. I haven't proceeded further as I was waiting to hear from you on the screws for the upper panel and boom cover. The screw numbers and related washers/spacers come up blank on both CessnaParts.Com and IWantCessnaParts.Com. The hardware numbers are: Figure 4A - Sheet 2 of 2 - Boom support & Wing Structure Assy. Item 15 - AN509-8R7 QTY: 22-each Item 16 - NAS221-11 QTY: 16-each (These are the High Shear) Figure 7A Wing Skins & Stringers Installation Item 40 - AN509-10R7 QTY: 18-each Item 41 - AN509-10R10 QTY: 19-each Item 41A - NAS221-10 QTY: 01-each Item 41B - S290D1032 QTY: 04-each (Washer) Item 42 - AN509-10R16 QTY: 12-each Item 44 - 1422041-2 QTY: 44-each (Spacer) Also, if it turns out that the leak is not coming from the aft upper inspection hole gasket, and there's a crack, obviously the tank will have to be removed... which then raises the issue of availability of "S51-8" hoses which also come up blank on the parts avails. Intend to put the jacks under the wings tomorrow and level the plane, and with the nose strut depressed, shore up the right boom. I would think that'll be sufficient for stabilizing before removing the upper inboard panel. BTW, this is a '77 P337. We'll be calling Cessna Propeller A/C Support in the morning and see if I can get a detailed drawing on the inboard and specs as to individual tank capacities. Not really necessary, but good to know. BTW, mine has 4-tanks per side, not three, and while the total capacity is 75 gallons between the four tanks (actually a little less with the R/STOL, as my usable is 71.5 per side due to a smaller outboard tank with this installation), with the dihedral of the wing and 38-gallons showing on the Penny Cap indicator the outboard tank at the filler cap is dry. I was just trying to figure out how much of that 38 gallons was in the inboard tank and the immediate outboard tanks... because of the dihedral it obviously wouldn't be 19 gallons each of two tanks or 12.6 between three of the outer tanks. With the inboard being the largest, I was just trying to get an idea of where the leak might be located on the upper part of the tank, either the side or top and knowing how much of this 38 gallons is in the inboard would give a little clue. SkyKing
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#4
10-21-02, 03:55 AM
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Now don't take the whole wing apart....
If in fact you have isolated it to the inboard tank... you only need to take the inboard section of the wing apart.... and the spacers that are in the hat section are re-useable.. so long as you properly torqued the wing screws down.. and they were before... so the spacers you don't need...
Naw its the inspection cover in the middle of the wing tank that is probably leaking... been their done that kinda thing... the inboard tank does not flex much so cracking is not really a option... but, you do need to take the boom cover off on top.. after its remove... you can remove the inboard top panel... and put the boom cover back on to stablize the boom stresses.. if you want.. using the old screws... and don't go drilling holes in the cover either... to try and get just them few screws out... the boom cover is structural and if you start putting holes in it.. your going to have problems... The circuit for the penny cap and the parts are listed in cessnas service manual for the system... You should not need to get inside the tank.. and to replace the indicator gasket... their are plugs that you can remove... and slip it over the cap part of the ring... Again no silicone or tefflon is to be used on the system... use only the products that are approved... As to the hoses.. they have been superceded... and they still are the black rubber.. but, no bradeing on the outside any more... actually the new stuff is silicon rubber radiator hose... blue... with a stripe.. some come red... but, the black hosing is still the old stuff... but, newer now... I will dig up the change if you want for the ne numbers.. but, again I don't think your going to have that problem... and if you do... their is time to get it... as you will have much more work to get the tank in and out... Actually its better if your going to take the tank out.. to remove from the wing tip in... and then go the other way when you put them back in...but,... you should hope to be their yet... Let us know what you are doing.. and maybe take a picture or two... Also the screw list you have is not correct.. as you don't need that many of the different types... again I will look it up.. but, most of the time we pull screws from stock... and when we put them back in we go with the 2 thread rule... even though cessna says a R5-7.. a R5-5 will work without a 1/8 inch of screw hanging out the bottom... you only need two threads.. past the nutplate... the rest is just so much dead weight... so re-sizing the screws are typical.. and when you pull them you will find they are not what the books says they are ... from the factory... so I would get the cover off... making sure the screws are measured for their locations... and then go get screws and gaskets.. etc... you can get them from API in one day... kinda thing... if not you can get them from spruce or another parts house.. in less ... almost... so that should not be stopping the progress... smile.... By the way you coming to LV in may..??? see other thread... G.M> GMAs
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#5
10-21-02, 04:32 AM
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Just to clarify... the Penny Cap sensor, gasket and everything at the forward part of my right inboard tank show no leakage whatsoever, all dry and solid... so with the fuel stains showing above the tank seam at the aft inboard section, yep, you're probably -- and HOPEFULLY -- correctomundo! I'd sure hope we don't have a crack, but as you may recall, Jim's 1973 337G had a recent bout with an inboard tank crack, although I don't know for sure exactly where the crack occurred. He told me it was "on top" of the tank, but the circumstances weren't clear. I was hoping he might expand on the thread he wrote, but nothing yet. He did mention it was about $30 bucks to have welded.
Yes, I do believe we'll make the North LV event. I don't know though, I might be just too politically incorrect for the eastern gang. (Ha!) SkyKing
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#6
10-21-02, 05:59 PM
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Fuel leak & mirrors
Skyking don't mean to be facesious facesius smart, but I did all the scientific thing with mirrors, filling & calculating where the leak on my left hand wing would be and all that sort of stuff but all I ended up doing was waste time and fuel because all the little pertuberances pertooberances ribby bits inside the wing changed the direction of the leaking fuel. In the end I gave up and removed the wing panel where I found a cracked weld on the front inner to middle tank connecting hose. Interesting thing was that all tanks were refurbished about 6 months prior. turns out that the LAME who refitted the tanks must have started the crack on installation cause the inboard tank can be tricky to get in and out. I spose what I'm saying is that it wasn't until I got into it that the problem revealed itself and with the wing panel off it was obvious.
Regards ..... Wayne
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