Fuel Leaks - Weep No More, Here I Come!

[GeorgePerry]

Since you're nearly done and about to leave Weep No More let me give you a "stupid pilot trick" I pioneered after departing from Paul's place.

 

I departed in poor weather, flew about an hour over a thick layer and then switched tanks.  When I did so the engine began to stumble badly so I immediately switched back to the original tank while worrying about what had gone wrong.  Naturally, I assumed the worst, which was that some free floating sealant had clogged the outlet inside the tank (it's a tube with a small screen on it), meaning I would have to return to Weep No More and have Paul fix it.  Well, fortunately I continued on course until I had about an hour of fuel left in the original tank, landed and checked things out on the ground.  I couldn't duplicate the problem there, which seemed mysterious.  I took off again but, wondering if some of that sealant might ultimately find its way to the fuel spider and cause a real problem, was uneasy for the next several hours.

 

So what was it?  My guess is that, naturally, Paul empties the tanks to do the work, including the fuel lines.  Almost certainly the engine stumble was due to the air bubble working its way through the lines on the second tank.  It probably would have cleared up in seconds but I was so quick in switching tanks that I didn't give it a chance.  I sure didn't want to make an IFR approach with a dead engine.  And the whole time I was cursing Paul for what I figured was his sloppiness.  The lesson?  Be sure to run both tanks on the ground before take off. 

Robert

 

That's a great story!  It warms my heart when people share things like this b/c it makes us all safer.  I had been thinking about the "risks" associated with flying the plane after such a significant maintenance procedure.  I think based on your story I'll likely do an extended 20 min run up on the ground and switch tanks to get at least 10 minutes a side of 7-8 GPH running through the system before I even think about going flying.  Assuming all goes well that should pretty much purge the system and get fresh gas through the pumps, pipes and spider to verify system integrity and function.

 

If you get the chance to stop by one of AOPA's fly-in's please introduce yourself...I definitely owe you an adult beverage!

[Rhumbline]

5 May update posted w/in the first posting

Having had my tanks re-sealed last year, I discovered during the annual this year that the stripper used to digest the old sealant had run into and pooled in a number of locations in the belly.  The stripper took the chromate off of the surfaces so treated that it came in contact with and congealed into something like dried glue which was very difficult to clean up. Though the airplane is old, it is very low time for its age and the innards are nearly pristine so I was a little bummed. I don't know if getting to it sooner would have helped but, in hindsight, I wish I had pulled the skins & panels off as soon as I got the plane home and done a little cleanup.

[jetdriven]

Dont do That!!

Dont change tanks Just before take off,,,   or just before landing!!

 

You should decide early on, which tank you prefer for take off or landing well before you do Either!

Then run on that tank for a Good Long time before it matters!

Yes, seriously, switching tanks before takeoff or landing can be really hazardous. You know your configuration works if you didn't change the tank. Switching right before a critical phase of flight is something different. You'll have to burn off 2-3 gallons to be assured the other tank is free of water, air, and can deliver the proper flow rate. Ground running isn't enough.

[Shadrach]

Yes, seriously, switching tanks before takeoff or landing can be really hazardous. You know your configuration works if you didn't change the tank. Switching right before a critical phase of flight is something different. You'll have to burn off 2-3 gallons to be assured the other tank is free of water, air, and can deliver the proper flow rate. Ground running isn't enough.

I did not think there was that much fuel forward of the selector. I figured less than a 2rd of a gallon. And here I have been starting on one tank and taxing on the other thinking that I am assuring fuel continuity from both tanks. 2-3 gals? Is that a WAG or just a conservative estimate. I no from previous posts that you've been as deep into the fuel system as I have.

I run a tank dry in flight often and given that it takes about 5-7 secs to relight, 2-3gals seems off by quite a bit. If that were the case, would it not have take the Robert the better part of 20 mins to discover the air in the line at the selector.

It would be intersting if not purely academic to do a dye test to see.

[Hank]

I've not tried it myself, but have often heard that there's enough fuel in the lines if switching to a blocked / empty tank (or OFF) to taxi out, runup and start the takeoff roll. One day I will remember to test this on landing--clear the runway, switch to OFF and see how far I go. At my old home, it was less than a half mile from where I started back taxi to my hangar, so that would not be a good test. Now it's easily double that, and more if I don't make the midfield turnoff.

But my Owners Manual does say to not switch tanks just before takeoff. So I either switch it before crank, before I start rolling, or after reaching a safe altitude. I prefer to depart with full tanks, but that's not always possible, so I try to take off on the fullest one. Another benefit of sticking the tanks. But sometimes I forget, and realize it at the hold short, so I just wait.

[jetdriven]

I had to do some math. Assuming 12 ft from the flow divider to the tank pickup and a 7/16" ID fuel line, the volume works out to 21.6 cubic inches, which converts to 12 oz. but you still have to run the thing awhile, long enough to fill the gascolator bowl with water and get water to the fuel injection which will cause engine trouble, alerting you to the fact that the tank selected is bad. So fill the line with fuel and/or water, then fill the gascolator bowl, then continue the water to the fuel divider. A carbureted plane must also fill the float bowl before engine trouble. Call it 24oz, up to maybe a quart. The engine burns 4oz/min at taxi and 34 oz/min at takeoff ff. It takes 32 minutes of taxi to burn a gallon from your selected tank. Takeoff power is 4-5 minutes.

On another kind of airplane I fly, takeoff with all engines feeding from the center tank was prohibited until 400 gallons was sampled. That's about 4 times the fuel line volume.

I don't think it's the air between the fuel selector and the engine that's the problem. It's the air between the fuel selector and the tank. It's a longer column and the boost pump does nothing for that. It's just the diaphragm pump. It will purge it, but takes time if the previous time that tank was used until dry.

I'm a big proponent of running tanks to empty but I also alert the other pilot i ran the tank dry, and it's SOP to never change tanks in a critical phase of flight. When using it for the first time it takes a bit to get steady fuel flow. If it happens on takeoff or abeam the numbers on down wind it could cause serious trouble.

[bonal]

Looks like your re seal has gone well George.  I think all of us are acting test pilots whenever we take that first flight after any maintenance has been done.  For me personally its that first flight post annual that really has me on my A game.  As for fuel selection I always start and stay on fullest tank making no changes until well into flight and my tank changes only occur when I have an acceptable field or runway within glide. I know there are many who would disagree but I will never run a tank dry I don't know why some would say then you never really know how much fuel you have, I know because I know how much I put in and how much I burn. also if you run one dry and then switch what happens if there is a problem with your other tank you have nothing left to go back to. End of flight.

[carusoam]

Data points:

In my first Mooney flight. I taxied quite a distance with the fuel selector in the 'Both' position. The carburetor bowl probably has more fuel in it than a FI system. Enough to attempt T/O...?

From my early O flights, Blocked tank vent, could take considerably longer to detect.

***

Logic:

Test as many things as possible, then taxi, run-up, T/O, climb to altitude on one...

Pay extra attention to FF and/or FP to compare to previous flights.

***

George has sparked a couple of interesting conversations in one thread!

[GeorgePerry]

Thanks!  at lease we aren't talking about bladders v/s reseal.  this is a much better topic to learn from.

[Seth]

  5.5 hours later I landed at Willmar.   

 

 

George-

 

5.5 hours is also my longest leg in the logbooks - from GAI to Minnesota as well.  Not to Wilmar but one of the airports in Minneapolis - KMIC - Crystal.  I had been into flying cloud quite a few times to visit friends and clients.

 

For me it was 5.5 hours there, and 4.5 hours back - tailwinds make a difference.

 

Glad it was a good experience and I plan to take my aicraft Paul at Weep No More when I need it resealed at some point in the future.

 

-Seth

[Marauder]

George-

5.5 hours is also my longest leg in the logbooks - from GAI to Minnesota as well. Not to Wilmar but one of the airports in Minneapolis - KMIC - Crystal. I had been into flying cloud quite a few times to visit friends and clients.

For me it was 5.5 hours there, and 4.5 hours back - tailwinds make a difference.

Glad it was a good experience and I plan to take my aicraft Paul at Weep No More when I need it resealed at some point in the future.

-Seth

Makes you wonder how Stinky Pants does it. Never mind. I know. He has the prostrate the size of a pea.

Sent from my iPad using Tapatalk

[aviatoreb]

I had to do some math. Assuming 12 ft from the flow divider to the tank pickup and a 7/16" ID fuel line, the volume works out to 21.6 cubic inches, which converts to 12 oz. but you still have to run the thing awhile, long enough to fill the gascolator bowl with water and get water to the fuel injection which will cause engine trouble, alerting you to the fact that the tank selected is bad. So fill the line with fuel and/or water, then fill the gascolator bowl, then continue the water to the fuel divider. A carbureted plane must also fill the float bowl before engine trouble. Call it 24oz, up to maybe a quart. The engine burns 4oz/min at taxi and 34 oz/min at takeoff ff. It takes 32 minutes of taxi to burn a gallon from your selected tank. Takeoff power is 4-5 minutes.

On another kind of airplane I fly, takeoff with all engines feeding from the center tank was prohibited until 400 gallons was sampled. That's about 4 times the fuel line volume.

I don't think it's the air between the fuel selector and the engine that's the problem. It's the air between the fuel selector and the tank. It's a longer column and the boost pump does nothing for that. It's just the diaphragm pump. It will purge it, but takes time if the previous time that tank was used until dry.

I'm a big proponent of running tanks to empty but I also alert the other pilot i ran the tank dry, and it's SOP to never change tanks in a critical phase of flight. When using it for the first time it takes a bit to get steady fuel flow. If it happens on takeoff or abeam the numbers on down wind it could cause serious trouble.

 

I understand not switching soon before take off (or landing) and I avoid it - I have a question though given your analysis.  I do switch tanks shortly after start up, as part of my pre-taxi check list to check continuity of both sides.  Am I doing anything useful by doing that? From your above analysis - I don't think I am doing anything and by doing that.

[carusoam]

Testing the ability to move the selector valve to both locations should be helpful. Especially if you intend to use the other tank during the flight...doing it pre-taxi, seems to be the best available option...

Some valves have a tendency to bind more as they age.

Best regards,

-a-

[Hank]

That's what I do, too, Anthony. When I don't remember to change it before startup.

[Loogie]

Checklist says check both left and right tanks during preflight.

Manual also says engine will quit 2-3 sec after placing fuel in shutoff (full throttle). Seems the fuel line will purge pretty quickly.

[Hank]

Loogie, your engine will run out of fuel in 2-3 seconds AT FULL THROTTLE. Please tell me you don't taxi like that. Idle is just 1-2 gph, while WOT in my plane is > 18 gph. Yours should be higher, giving you longer ground running time.

[Loogie]

Off course I do, every time I take off!

So the math is conservatively 20% of full throttle assuming linear curve flow, ergo it should run out in about 3 min or so at idle, just a WAG off course.

Cheers

[Guest]

Looks like your re seal has gone well George.  I think all of us are acting test pilots whenever we take that first flight after any maintenance has been done.  For me personally its that first flight post annual that really has me on my A game.  As for fuel selection I always start and stay on fullest tank making no changes until well into flight and my tank changes only occur when I have an acceptable field or runway within glide. I know there are many who would disagree but I will never run a tank dry I don't know why some would say then you never really know how much fuel you have, I know because I know how much I put in and how much I burn. also if you run one dry and then switch what happens if there is a problem with your other tank you have nothing left to go back to. End of flight.

While in most cases I would agree with your statement about knowing the quantity of fuel on board by what you put in and what has been burn. However a leak in the system or a missing fuel cap etc. throws your calculation off. Hence accurate fuel quantity system is important.

Clarence

[chrisk]

Looks like your re seal has gone well George.  I think all of us are acting test pilots whenever we take that first flight after any maintenance has been done.  For me personally its that first flight post annual that really has me on my A game.  As for fuel selection I always start and stay on fullest tank making no changes until well into flight and my tank changes only occur when I have an acceptable field or runway within glide. I know there are many who would disagree but I will never run a tank dry I don't know why some would say then you never really know how much fuel you have, I know because I know how much I put in and how much I burn. also if you run one dry and then switch what happens if there is a problem with your other tank you have nothing left to go back to.

End of flight.

 

In my book, there are legitimate reasons to run a fuel tank dry.   You might know your fuel burn rate, and how much you put in.  The question is:  How much usable fuel do you have in your tanks and how much fuel was already in there?  If you run one dry, you can find out.   I've done this on a hand full of occasions:  when checking the fuel warning light or for making a fuel stick.  I don't make a habit of running my tanks dry, and I try to do it within gliding distance of an airport. (up high, but not so high that I can't restart the engine).

 

+1 one on the first flight after an annual being a test flight.  It's always a trip around the pattern, and then another close examination.  My last annual cost me 4 hours of waiting for the ceiling to come up  from 400 ft so I could make it home.  --I used to time to learn from the mechanics in Don Maxwell's shop.

[bonal]

As I pointed out "I know there are many who would disagree" and I would love to have an accurate fuel measuring display but at this time I do not so I do what works best for me.  Checking my caps is part of my CIGAR as they are easily seen from cockpit and I have calculated my fuel burn to be within a couple of tenths of a gallon on an over 3 hour leg (repeated many times). your comment about leaks or other factors only supports my approach even more.  if I know that I still have an hours fuel in tank 1 and there ends up being a problem with tank 2 that causes a loss of power...well... I still have an hour to get down safely if tank 1 is dry end of flight. I just cant see the fault in this reasoning but it is good to have these discussions because I always learn from them.

I have also determined what each of my gauges in the old Garwin Cluster is showing but I don't trust it to be accurate so I use the stick the burn and the time and never push my legs.

[wishboneash]

Took my plane up to Troutdale yesterday. Took the coastal route due to some tstorm activity in the Medford area.

It will be 4 weeks+ to get the job done as they have several jobs going right now. It was clear I needed a full strip and reseal. I will be glad to have had this done. Will update when I get pictures back of the progress.

[GeorgePerry]

21 May Update on the First Post

[GeorgePerry]

27 May Update on the first Post....This should be the last update

[wishboneash]

Pictures, before stripping and after stripping.

[chrisk]

Thanks for the pictures.  It's interesting to see where the sumps and fuel pickups are.