Ramp Fuel Level

[FADEC]

So few months in to ownership and yet another dilemma.  Currently my plane is parked on the ramp, I am on a list for a hanger but I probably have a better chance of winning the lottery then getting a hanger anytime soon. My question is ramp fuel load, I have read and been told the best ramp fuel load for the health of the tanks is full.  However on the last (and first) trip with the wife, kid, dog, and bags I departed with 45 gallons.  As I run weight a balance scenarios I can't see needing to be to much above that. So do I keep the Airplane full when on the ramp then just plan a fuel burn flight a day or two prior?  How long can I let it sit on the ramp at 45 gallons before I need to worry about sealant drying out? 

 

Andy

[wombat]

Over the course of your ownership of the aircraft, I suspect the additional cost of resealing the tanks sooner because they were left half empty will be lower than the cost of burning off excess fuel in order to keep them full but have the plane light enough for your planned flights.

I would recommend a hybrid approach... If you know of a relatively soon family trip with no other flights planned in the meantime, don't fill it all the way up.  If you think the next one will be several weeks away and you don't know if you are going to fly in the meantime, fill it up and then you'll never be flying with your family for the first flight in weeks.  This is kind of what I'm doing with my plane... If I am confident that my next flight will be with more than just me and my wife, I'll leave the plane less than full.  Otherwise, I'll fill it up and this might result in having to go fly before the planned trip, but I'm OK with that.

The additional safety of having flown those extra hours will maybe pay for itself. 

And the additional fun of flying your Mooney around!

[Joshua Blackh4t]

Possibly overthinking it.

I often operate out of fields with no fuel available, so its practically impossible to be there with full fuel.

I can see how fuel might keep the sealant cooler on hotter days, but the top is never covered anyway so not much difference.

Personally I think what is more important is condensation (never had any except the drops around the fuel cap that escaped)

And most important fuel consideration is keep it full so its heavy if there is a strong wind.

All of which is secondary to keeping it covered as much as possible and spraying acf-50 on any suspect areas. Being outside isnt nice.

[Vance Harral]

I recognize it's de rigueur to speculate on how to achieve best longevity of fuel tank sealant, given how expensive and frustrating it is to deal with seeps.  But I think there is much speculation and little (or no) evidence for most of the pet theories.  Even if the pet theories have merit, it's hard to say to what extent non-full tanks compete with hard landings, and operating on grass runways, and differential heating from sun exposure when unhangared, etc. as sources of decreased sealant longevity.  Furthermore, the fuller the tanks when sitting, the more weight sits on the ridiculously expensive landing gear doughnuts, potentially causing them to wear faster, etc.

Call me a contrarian, but my suggestion is that you pay no attention to any of this.  You can't really control most of it, and even if you could, there is no serious evidence for all these pet theories about sealant longevity.  Just fly the airplane in the manner that best suits your needs, keep an eye out for seeps (and other wear items), and address them when needed.

[Fly Boomer]

1 minute ago, Vance Harral said:

I recognize it's de rigueur to speculate on how to achieve best longevity of fuel tank sealant, given how expensive and frustrating it is to deal with seeps.  But I think there is much speculation and little (or no) evidence for most of the pet theories.  Even if the pet theories have merit, it's hard to say to what extent non-full tanks compete with hard landings, and operating on grass runways, and differential heating from sun exposure when unhangared, etc. as sources of decreased sealant longevity.  Furthermore, the fuller the tanks when sitting, the more weight sits on the ridiculously expensive landing gear doughnuts, potentially causing them to wear faster, etc.

Call me a contrarian, but my suggestion is that you pay no attention to any of this.  You can't really control most of it, and even if you could, there is no serious evidence for all these pet theories about sealant longevity.  Just fly the airplane in the manner that best suits your needs, keep an eye out for seeps (and other wear items), and address them when needed.

How do you feel about MMO? 

[PT20J]

I'm with @Vance Harral. Does anyone actually have documentation from the manufacturer or some other authoritative source that tank sealant lasts longer if kept wet? Or, is it just another OWT? 

[Ragsf15e]

1 hour ago, FADEC said:

So few months in to ownership and yet another dilemma.  Currently my plane is parked on the ramp, I am on a list for a hanger but I probably have a better chance of winning the lottery then getting a hanger anytime soon. My question is ramp fuel load, I have read and been told the best ramp fuel load for the health of the tanks is full.  However on the last (and first) trip with the wife, kid, dog, and bags I departed with 45 gallons.  As I run weight a balance scenarios I can't see needing to be to much above that. So do I keep the Airplane full when on the ramp then just plan a fuel burn flight a day or two prior?  How long can I let it sit on the ramp at 45 gallons before I need to worry about sealant drying out? 

 

Andy

I also don’t worry about fuel level on the ramp, but much more of an issue for you is water.  Make sure your caps are properly sealing and you sump all applicable places.

[LANCECASPER]

1 hour ago, FADEC said:

So few months in to ownership and yet another dilemma.  Currently my plane is parked on the ramp, I am on a list for a hanger but I probably have a better chance of winning the lottery then getting a hanger anytime soon. My question is ramp fuel load, I have read and been told the best ramp fuel load for the health of the tanks is full.  However on the last (and first) trip with the wife, kid, dog, and bags I departed with 45 gallons.  As I run weight a balance scenarios I can't see needing to be to much above that. So do I keep the Airplane full when on the ramp then just plan a fuel burn flight a day or two prior?  How long can I let it sit on the ramp at 45 gallons before I need to worry about sealant drying out? 
 
Andy

I think any of us could find you a hangEr.




But finding a hangAr is a little more difficult



 

[PT20J]

Ah, the pedantic bit is set.

[A64Pilot]

54 minutes ago, PT20J said:

I'm with @Vance Harral. Does anyone actually have documentation from the manufacturer or some other authoritative source that tank sealant lasts longer if kept wet? Or, is it just another OWT? 

We can’t even prove cigarettes cause cancer and your asking for this?

I was a manufacturer, you want a letter? Honestly no manufacturer cares because sealant won’t deteriorate for likely decades no matter how you keep it.

It’s been know for longer than I’ve been alive probably that bladders go bad on top most often, the theory is heat, as bladders are a rubber type substance and so is fuel tank sealant it’s logical that heat is the enemy, not being dry, but I thought that leaks on top were relatively rare anyway, They were on the Crop Duster I built anyway and likely there they weren’t noticed because a crop duster was never fully filled. They carried 3 to 4 hours of fuel and no job lasted an hour, so you would grab fuel when you loaded the hopper, because you were usually WAY overgross, making the trees at the end of the runway determined load, so loads got smaller as the day got hotter.

Personally I wouldn’t sweat being 60 or even 80 lbs overweight myself as long as where I’m flying out of has plenty of runway and isn’t at some place demanding max performance to climb out of.  I like having a little extra fuel, excess fuel gives me options, especially with the family on board.

[LANCECASPER]

1 minute ago, PT20J said:

Ah, the pedantic bit is set.

Anyone who uses "pedantic" is . . lol   

[PT20J]

19 minutes ago, A64Pilot said:

We can’t even prove cigarettes cause cancer and your asking for this?

It’s been know for longer than I’ve been alive probably that bladders go bad on top most often, the theory is heat, as bladders are a rubber type substance and so is fuel tank sealant it’s logical that heat is the enemy, not being dry, but I thought that leaks on top were relatively rare anyway.

Personally I wouldn’t sweat being 60 or even 80 lbs overweight myself as long as where I’m flying out of has plenty of runway and isn’t at some place demanding max performance to climb out of.  I like having a little extra fuel, excess fuel gives me options

Bladders are made from an entirely different material than sealants, so it's apples and oranges.

Fuel tank sealant products generally tout their resistance to hydrocarbons because fuel is a strong solvent. It stands to reason that if they can withstand soaking in gas, they can withstand air and heat.

The application is critical. I have a 30-year-old airplane that has no leaks. Maybe I got lucky and my airplane wasn't sealed by some new hire after one of Mooney's many shutdowns and it wasn't done on a Friday 

Did the Army require gas tanks to be kept full?

 

[Fly Boomer]

1 minute ago, PT20J said:

The application is critical. I have a 30-year-old airplane that has no leaks. Maybe I got lucky and my airplane wasn't sealed by some new hire after one of Mooney's many shutdowns and it wasn't done on a Friday

You just got to believe the low man on the totem pole is going to get stuck with that job.

[LANCECASPER]

3 minutes ago, PT20J said:

The application is critical. I have a 30-year-old airplane that has no leaks. Maybe I got lucky and my airplane wasn't sealed by some new hire after one of Mooney's many shutdowns and it wasn't done on a Friday 

There were three or four ladies at Mooney that were experts at sealing a tank when they were being built. They did it for years. I have a theory that when business would pick up and they would hire another three or four people is when they would have quality problems. That would be one explanation of why some airplanes have 40 year old tanks with no re-seals to this day. And some from the same run had to be resealed in half the time.

In the early 2003-2005 era there were tanks that were leaking at the first annual. Then they implemented sealing some of the pieces before the skins ever went on. The last run from 2006 - 2010 appear to be some of the best.

[GeeBee]

The Mooney MM section 5 says to keep tanks half full to prevent corrosion. I suspect corrosion has a lot to do with sealant deterioration as once surface deterioration starts, the sealant no longer adheres.

[MikeOH]

I've never worried about how much fuel is in the tanks when parked outside or inside.

I worry a lot about the condition of the fuel cap O-rings when parked outside!

[StevenL757]

3 hours ago, FADEC said:

So few months in to ownership and yet another dilemma.  Currently my plane is parked on the ramp, I am on a list for a hanger but I probably have a better chance of winning the lottery then getting a hanger anytime soon. My question is ramp fuel load, I have read and been told the best ramp fuel load for the health of the tanks is full.  However on the last (and first) trip with the wife, kid, dog, and bags I departed with 45 gallons.  As I run weight a balance scenarios I can't see needing to be to much above that. So do I keep the Airplane full when on the ramp then just plan a fuel burn flight a day or two prior?  How long can I let it sit on the ramp at 45 gallons before I need to worry about sealant drying out? 

Andy

By leaving your tanks full for long periods, you should be more concerned about the condition of your shock discs than tank sealant.  My IA and I have seen several airplanes pass through his hands during annuals where the discs were compressed beyond acceptable limits.  The owners have admitted to leaving their tanks full for long periods/on a regular basis while not flying.  A tank repair is relatively inexpensive, versus just under $2000 for new discs and labor.

[jetdriven]

It depends. A patch job might be something like two grand, with limited results, but a full reseal is  something like 15 grand.

Long body airplanes, kill the shock discs in a couple or five years no matter what. Meanwhile, a short body airplane can go 20 years. It all depends.

[PT20J]

Yes, they all use the same disks, but the weights are not the same.

It’s easy to check the fuel caps for leakage and should be done every annual. Just get a length of vinyl tubing that fits over the vent tube and blow into it (with your mouth, not shop air) while spraying the caps with soapy water and check for bubbles. Switch the o-rings to fluorosilicone(blue) and avoid the annual replacement expense. Lube the center post with Tri-flow and the big o-ring with Vaseline and they will be easy to remove.

[Echo]

3 hours ago, LANCECASPER said:

I think any of us could find you a hangEr.




But finding a hangAr is a little more difficult



 

Did U have fun?  I know I did laughing at U 4 it...

My friend Otto would call you something...Give it a watch.  It's a real cliff "hanar"

[1980Mooney]

1 minute ago, PT20J said:

Yes, they all use the same disks, but the weights are not the same.

Exactly.

24 minutes ago, jetdriven said:

It depends. A patch job might be something like two grand, with limited results, but a full reseal is  something like 15 grand.

Long body airplanes, kill the shock discs in a couple or five years no matter what. Meanwhile, a short body airplane can go 20 years. It all depends.

By filling the tanks you can easily add about 400 extra pounds of fuel that you don't really need right over the mains  - and you will kill the shock discs even faster.

You are right - a short body with 52 gallon tanks sits on the same shock discs as long bodies (most with 100 gal. tanks - even the early ones had 89 gal.), and anyone with Monroy's which have about 100 gal.   

[DCarlton]

I base it on the price of fuel.  If it’s cheaper I tank up full.  If not, and I don’t need it, I fill to the tabs.  Ever worry about the rapid flow of fuel from the fuel nozzle against the sealant over time?  I do.  Always tweaking the nozzle angle.  

[Fritz1]

After my tanks were sealed by weep no more 5 years ago Paul advised me to keep them full, sitting on an empty tank for a week however he said does not matter, when in doubt he advised to alternate the tank that is not full, it appears that the sealant deteriorates faster in high temperatures, I am fortunate enough to have a hangar and keep the 100 gal tanks full, if needed for a passenger flight I siphon off fuel into Jerrycans, if not flown for a week or longer I put the airplane on jacks to take the weight off the shock discs. If parked outside I would keep one tank full and alternate between tanks, the problem may be overrated, the word is that sealants today are better than 30 yeas ago, better answered by weep no more or wet wingologist or texas tank repair guy

[PT20J]

From the PPG technical data sheet...

PR1422 Class B is an aircraft integral fuel tank sealant. It has a service temperature range from -65F to 250F with intermittent excursions up to 275F.

 

[wombat]

Should we treat those temperatures as an acceptable target as long as we are below it, like many pilots treat Vfe and Vle, or should we treat them like many pilots do the cylinder temperature redline and do everything possible to keep them as far away from that temperature as possible? 

 

On my plane with bladders and several other aircraft with bladders I've used, they leaked from the top of the bladder.   I don't know if that was because the tops got hot and degraded faster over time, or if it's because they were not saturated with fuel as often and degraded faster over time.

My rocket's wet wings were not leaking on the top though; only on the internal ribs to the wings and on the bottoms.   But the sellers assured me that the plane had been hangared its whole life.