Ah, the 'Blue' Gas Shower!

SkyKing · #1 09-25-02, 08:27 AM

GOOD Morning!

Yep, it's MORNING out here on the "Left Coast" and I haven't been to bed yet! You see, I decided to go flying late yesterday afternoon and flew over to Scappoose, Oregon to 'TOP OFF' my tanks with some of that cheap $1.82 a gallon blue juice. Flight at 5,000 with 27"/2300 RPM and 62 PPH was giving me a DME groundspeed of 166 knots -- good tail wind out of the North. Okay, so far so good. I land, pull up the pumps and the line boy hooks up the ground and I tell him I'll do the pumping. Fine. I fill the left wing first, bring it right up to the rim, filling slowly of course so that the inboard tanks fill to the top too. Then I do the same with the right wing. Just as I'm installing the cap, the line boy says, "Hey, you've got fuel running down the side of your plane!" Oh, GREAT! It was a real gusher. Poor selection of words... it was running all over the place, but primarily down the last window on the right side and all over the fuselage. Well, I needn't ask you... you've probably had one of those "blue showers" before... boy that stuff SURE singes the skin when it runs down into your tennis shoe! Anyway, what to do... the lineboy grabbed a Rubbermaid garbage can, one of those 35-gallon jobbies and we tried catching what we could in it, but since the dihedral of the wing was such, everything was running inboard first. I got out the trusty ratchet screwdriver and took those ga-zillion screws off the inboard panel thinking we might find the culprit on one of the two hoses... no such luck. The lineboy calls his boss while I hold absorbent paper rags to try and keep the gas from running down the side. As the boss arrives, a local A&P is behind him... I've already got the 5/8" socket and ratchet out from my on-board tool kit, clipped the safety wire on the inboard drainplug... and it just so happened that I had four of those 5-gallon red-plastic gas cans with me... the idea was after topping off, I'd take 4-jugs back home with me for later, since our airport still thinks their blue juice is better than all the rest of the airports, i.e., they charge WAY more! Well, as it turns out the AirNav page lists the fuel at Scappoose as a "SUPER DEAL" for $1.82, but then there's the fine print, which I didn't see... SO, with their Fed Excise Tax and State Tax, the price becomes $2.10! So much for the 'SUPER DEAL'. So, with a funnel and the four jugs we pull the drainplug and skim off 20-gallons of the 75 and with each 5-gallon jug being filled the leak stops... but only for a brief time. I borrow a 5th jug and take another 5-gallons out and that slows things to just an intermittant drip. So I told the mechanic, let's button her up, safety wire the drainplug and I'm outta here. Loaded the 5-jugs aboard ... a flying "GASCAN"... YIKES... I told the mechanic if he sees a Roman Candle he'll know what happened. I asked him if I owed him anything, he said no, so I handed him twenty bucks and told him to go buy a jug and enjoy himself. It was GREAT to have somebody come by to help out and I thought $20 bucks was the least I could do. And who knows, I might need his help again sometime. So, what me thinks is because I've not been keeping the tanks topped, generally running with 80-gallons (40 a side)maybe there's an inspection hole with a gasket on the top of the inboard tank that's let go - does that sound like a possibility? When I got back to the hangar it was about 9:30PM, so I got out the Kit Wax and attacked the paint and plexiglass and took all the stains off... for the most part it all cleaned up fine. Oh the landing... when I turned left base from the downwind, I really had to muscle it as that left wing was HEAVY! All the leaking seemed to subside, but there was still a persistent drop every minute or so, so I pulled the lower panels again so that it wouldn't leak against the fuselage, and then put another jug with a funnel up on a step-ladder to catch the drips until I can get my mechanic to come up and help me figure out what's going on. And here I thought with the fuel strainers all done (more on that later), things would be easy sailing! NO SUCH LUCK! Well, I see it's a little after 5Am and I'm pooped...since I don't want to wake up everybody with a shower, I did one of those washcloth cleanup numbers and I'm gonna sleep on the floor tonight with a sleeping bag cuz I still smell like a gas tank. With 25-gallons out and into the gas jugs and then a 10-gallon burn from the right tank on the way home, there's about 40-gallons, so I'm thinking with the way the fuel stains ran in flight... all from the inboard right tank... that it must be leaking from the top, in fact with the lower inspection panel off, when I put a mirror and flashlight up in there you can see fuel stains coming off the side in about the middle of the tank from the top side... I'll have to dig out the manuals later after my nap and see what's what.

Oh, what an absolutely 'FUN' day! Anybody else top their tanks lately and get a surprise like this?

SkyKing

Dale Campbell · #2 09-25-02, 09:24 AM

I had the same thing when I toped my tanks this past winter. We pulled the cover off the top of both inboard tanks. We found the gasket shrunk on inspection cover on top of both left & right inboard tanks. The screws where all loose in covers. We took both gaskets off. They where cork & still soft & in good condition. So we put a aircraft type sealer on gaskets & put them back on. We waited until next morning to put fuel back in. That gave the sealer time to dry. By the way my ship is a 1978 G model.

GMAs · #3 09-25-02, 05:10 PM

Just spent the last 10 min writing up the response to help ya... too bad it got wiped out... you would have liked to have read it probablly... but, I don't have time now to re write it... dammm computer...

Wayne Pearce · #4 09-25-02, 06:34 PM

And I thought I was the only one to have this happen...
My leak was left side with fuel running down side of fuse.....spose given dihedrel slope and lay of the land any excess fluid inside the wing will end up against the side bulkhead......The interesting thing was that you could'nt clearly identify where the leak was until we took off the top wing panel (prior to that I had all sorts of theories as to where the leak was) GMas was good help there.
Anyway the leak turned out to be a broken weld on a weld on socket on the middle face of the inboard tank ie. next to the boom. I said broken weld not cracked because the position of the socket makes it difficult when refitting the tank ie. use care.
Now bear (bare) in mind that all tanks were removed and refurbished only 6 months prior to the leak so obviously damaged when reinstalled.......anyway my theory is that if the interconnecting hose or socket rubs against anything it will fatigue the metal until it fails along with all the other possible causes......
Oh I have used a water based degreaser to remove any signs of fuel or grease non toxic does'nt weaken paint surface etc it is called Tri-Nature Optimate dunno wether you can get it over there.

As I said really peeved me cause I thought I had the only plane that leaked

Regards ......Wayne

GMAs · #5 09-26-02, 07:43 PM

Yep the wing tank towards the center section of the plane...

Two covers on it.. one up forward ... remove the inspection cover for the gas gauge.. and use a flex inspection bore scope.. look along the top of the tank and along the sides... their you should see streaks...

Cracking is a posiablity but, not likely in that tank.. more towards the center one.. as it is bigger and flexes more... common...

When you decide to take the tank out on the inboard section of the boom.. take the boom cover off do not try and take the cover off without removing the boom fwd cover else you will mess up not only the paint on the wing panel but, will bend the metal.. and it won't bend... back...

New screws all around... watch out for losing the plastic hat section spacers... or allowing them to go inside further.. their a bear to get out..

When you put new screws in.. tip...

get a paper cup cap thing.. put some zinc cromate in it... and dip the threads of the screw making it wet before putting it in... keeps the corrosion and rust factor down.. also keeps the screw from coming back out and hitting the rear prop... and messing you back prop up... some take and dip the whole screw... OK... its a big blue thing that they do to the planes they make too...

Don't use a elect or speed wrench on putting the screws back in.. use a new apex bit so that you don't mess them up... yes they have a torque that they should be tightend too.. by screwdriver only...

On taking out the tank... ahhhh... call me.. its a lot of discussion and different ways...

On opening the inspection cover and gas gauge cover... do not just tighten down the screws... the gasket has a set height... and if you think you are going to just tighten it up... forget it ... you spent 20 bucks for screws and a hour just to get here... don't get cheep now...

New gaskets are cork... buy from cessna.. they are different... than what you get at the store....stuff... if you can find viton rubber ones and you will never have this problem again as you will find leaving the tanks empty will cause the cork to dry out.. and no it won't expand again when it gets wet... it will however leak... smile... so keep the tanks at least half full... all the time... good practice...

New gaskets are glued down also... with a special stuff from cessna... don't get cheep and think permatex is going to work here.. won't...

Screws/bolts that hold down the inspection covers are torqued... yep pay attention here... they have little gaskets under the heads... pay attention here with the glue and tightening process... else after you put it all back togeather... you will become a expert at doing it again... safety wire heads like it was... if its been dinked with.. write and we will send you a picture of how it should be... smile...

Good luck .. your going to need it... these tanks are really tempermental... and most get abused by the mechanics when they over tighten the hold downs or over torque the screws...

Oh and by the way... the top skin on the wing... ya its part of the structure stength of the plane... smile... that is why they have them little hat sections... glued on... you don't want to mess with them .. else you could have the wing have problems in the end... smile... good luck.. G.M. GMAs...

SkyKing · #6 09-29-02, 11:18 PM

GMAs,

On our '77 P-model, I have never let it sit with empty tanks... always keep at least 40 to 50 gallons per side, so I don't quite understand how the gasket could have dried out. Plus I keep the plane hangared, so it's protected from the sun and elements.

Inspected things yesterday... with the right fuel gage indicating about 38 gallons, there's no fuel leaking and no new stains anywhere that I could see. Because the left wing has about 65 gallons, the airplane is not setting level... the right wing is canted up a bit higher than normal, so any fuel in any of the three outboard tanks is going to the inboard tank or at least leveling out in the inboard and the first tank outside of the boom. Obviously, if there were a crack in the inboard tank, it would be leaking now, but I suspect you may be correct - that the aft inspection hole cover/gasket was leaking when I topped it off.

With the flaps extended and looking with a mirror and flashlight through the inboard flap rod actuator opening, the fuel stain concentration in the right wing appears to be confined to the aft-inboard area of the lower wing skin along the lower rear spar and does not extend outboard much farther than the furthest outboard fuel drain valve and I don't see any evidence of staining in the area directly beneath or beyond the inboard flap bellcrank.

The heaviest concentraion of stains appear to be in line with and just below the aft cover plate/inspection hole of the inboard tank, which is of course, underneath the wing skin. Was this part of the 337 an "Edsel" design? Hhmmm. And looking at the screws and paint on top of the inboard tank area, it's obvious the upper panel has never been off the plane. BTW, the interior areas are bright and shiny and no corrosion of any kind.

With the square underside inspection panel off as well as the lower aft fairing removed, looking up between the wing inboard rib area and the fuselage, there are no fuel stains forward of the aft fuel line/hose connection to the fuselage. However, what puzzles me is the pictorial in the parts manual for my serial number (0286) doesn't quite match, as I see TWO aft fuel line/hoses coming from the tank and connecting to the fuselage and Figure 114A only shows ONE! Hhmmm.

GMAs, you mentioned something about the tank vent line hookups getting dry and hard and possibly leaking... that this could cause the problem... could you digress a little on that... I don't quite follow. Aren't the vent lines made of aluminum? I'm now wondering if that might be the problem as this same thing happened to me about a year ago when I stopped for fuel along the way and topped off... when I got home there was fuel stains in the same general area, but with 65 gallons a side at that time, there was no leaking that I could detect.

I also opened up the top side inspection cover and inspected the area around the Penny Cap fuel sensor and the only thing I see there is the dark Cessna glue they spread around when installing things... but it is dry on top and no signs of any leakage whatsoever.

Well, that's the rundown for now... I'm REAL curious about those vent lines drying out??? I can't imagine the aft inspection hole of that inboard tank has let go. Anybody know what the capacity of the inboard tank is?

SkyKing