flying with fuel in only one tank

[rbridges]

I'm asking this for someone I met yesterday.  Found out shortly after purchasing his D model mooney that it drips from the passenger side tank.  I spoke with him about having it patched vs. reseal/bladders.  He seems to be leaning towards the patch for now.  So my question is this, would flying with fuel in only one wing be a bad idea?  I've never done it so I don't know if the weight shift makes much difference.

 

I figured you can get 2 hours with 30 minutes reserve.  That would get him to someone that can do the patch.  I recommended Joey Cole but there may be someone closer.

 

 

[N201MKTurbo]

I would put some fuel in the leaking tank, just in case.

 

The fuel imbalance is manageable, it is just annoying.

[rbridges]

I would put some fuel in the leaking tank, just in case.

 

The fuel imbalance is manageable, it is just annoying.

 

A local shop kinda freaked when they saw the leak and didn't want to fly with him.  I don't know how bad it is or whether it was a safety issue.  He said it leaked from the bottom of the tank i.e. it starts whenever any fuel is in the tank.  

[triple8s]

i would fill both tanks and start the trip burning off the leaking tank, switch when it got to nearly empty and then burn off the good tank. might not even need to fill it to max cap. but i would end up with the good tank holding my reserve at the end of the trip.

[carusoam]

Find the source of the leak...?

Anything from a fuel line or a fuel level sensor seal can be an easy fix.

Try to avoid flying a plane that has a dripping tank (there are rules for size of the leak in the MM)

There is no firewall between the tank and the cockpit.

Some leaks enter the cabin and soak the rug.

Better to know before you go...

Keep in mind, I am a PP, not a mechanic...

Best regards,

-a-

[mooniac15u]

Convincing yourself it will be ok and starting a flight with a potentially hazardous issue is usually not a good plan.  The maintenance manual has guidance on which leaks are acceptable and which are a flight hazard.  The relevant part is in section 7 starting on page 7-8 (http://www.67m20e.com/Mooney%20M20%20Series%20S-MM%201980.pdf).

[Yetti]

I uploaded the relevant sections of the Service Manual as to what leak is a hazard.

[DAVIDWH]

As a general rule, if anything is going to happen, it will happen when one starts the engine.

 

I think it has a sort of KABOOM sound. Never experienced this myself, just passing on urban legends.

 

With that in mind, if you can start the engine and taxi, the flight should go well.

 

As a side note, when I was a young'un, my dad once stopped a bad tank leak on an old 40 ford with a bar of soap.

 

However, unable to find any documentation under aircraft tank seals for this method of tank sealing.

[cliffy]

You need to determine where the leak is coming from first. If it is a fitting or the fuel level gauge it can be fixed real easy by any A&P right where it is at. Get an A&P to look at it. If it is actually a leak in the internal sealant of the tank a ferry permit can be issued to fly on only one tank to get it to a reseal shop. Just make 1 hr legs and you have lots of reserve. Many Mooney pilots fly long legs by draining one tank completely and finishing on the other. Flying with one tank empty and one full is not a lateral balance problem according to Mooney. I have done it - no issues. Yes it is safe but the other tank needs to be drained so it doesn't leak.

Read your drip limits If it is wet and dripping drain it and go get it fixed.

As an A&P I would sign the ferry permit if I was there given the above inspection and set up.

[triple8s]

I guess i should clarify......if you have a leak on a wing that is a seep that over time leaks on to the ground or down the mlg and gear doors, i wouldnt be too worried. Always consult your maintenance professional and go by mooney recommendations. There are examples of acceptable leaks in the manual.

[mooniac15u]

As a general rule, if anything is going to happen, it will happen when one starts the engine.

 

Based on what?

 

You need three things for a fire: fuel, air, and ignition source. With a leak you have plenty of fuel and air. There are many spark sources on an airplane.

 

In chemical process safety we had a rule that we never relied on absence of an ignition source. If you have fuel and air you have to assume that it WILL find an ignition source.

[rbridges]

I guess i should clarify......if you have a leak on a wing that is a seep that over time leaks on to the ground or down the mlg and gear doors, i wouldnt be too worried. Always consult your maintenance professional and go by mooney recommendations. There are examples of acceptable leaks in the manual.

 

he described it as an actual drip but his tank was empty when I was talking to him.  He is an A&P, and he'd already seen Maxwell's article about finding leaks and sealing them.  

 

Thanks for the help.  I'll tell him where to look in the maintenance manual about the leak description, but I have a feeling he's already seen it. 

[TTaylor]

Back to the original question.  I flew my 63C dry on one side several times and never noticed any difference in handling. 

[jimluper]

Who is Joey Cole? Does he specialize in fuel tank leaks on Mooneys?

[Hank]

Joey is an MSC in Dalton, GA. Moved from Rome last year. He patches tanks and installs bladders, in addition to annuals, maintenance, repairs and upgrades.

[ArtVandelay]

You never said how far you have to fly, if 100 miles, then you don't need to fill the other tank

[rbridges]

You never said how far you have to fly, if 100 miles, then you don't need to fill the other tank

 

we were just kicking around possibilities.  Cole's place is <1.5 hours.  There may be others that are closer.  As far as endurance, it shouldn't be an issue.  I just didn't know how "lopsided" the plane would get with full fuel/no fuel in the wings.  Of course that would only be on takeoff.  You figure he's going to burn several gallons when it comes time to land.

[ArtVandelay]

we were just kicking around possibilities. Cole's place is <1.5 hours. There may be others that are closer. As far as endurance, it shouldn't be an issue. I just didn't know how "lopsided" the plane would get with full fuel/no fuel in the wings. Of course that would only be on takeoff. You figure he's going to burn several gallons when it comes time to land.

25 gals would be enough for 2.5 hrs, that's 150 lbs, not a big difference but if you stalled it you might get a pronounced wing drop, so I wouldn't do any stalls

[N601RX]

The only thing I would add is that if your fuel gets below about 9 gallons the pickup will unport on a long sideslip if the fuel is in the low wing. 

[Hedge]

Back to the original question.  I flew my 63C dry on one side several times and never noticed any difference in handling. 

The mooney manual actually says to fly one wing dry and switch to the other.  I had a leak in one of my wings and that is exactly what I did.  I fly the wing that had a slight leak until it went completely empty, and flew with my non leaking wing to the FBO to repair the leak.

 

Also, the fuel source has to get to the lower explosive limit on the concentration and stay below the Upper explosive limit.  It is tough to get the the LEL outside.  3 feet above a puddle of gasoline is not explosive outside, and that has the factors of safety for determine an explosive area based on fire codes.

[rbridges]

thanks.  Looks like it should be a non-issue if he goes that route.  Just don't want someone to be a headline in an NTSB report.  

[mooniac15u]

Also, the fuel source has to get to the lower explosive limit on the concentration and stay below the Upper explosive limit.  It is tough to get the the LEL outside.  3 feet above a puddle of gasoline is not explosive outside, and that has the factors of safety for determine an explosive area based on fire codes.

 

That's assuming the fuel is leaking directly out of the tank and away from the plane.  Any fuel that leaks into a wing cavity or the belly has the potential to reach the LEL. 

[ArtVandelay]

The mooney manual actually says to fly one wing dry and switch to the other. I had a leak in one of my wings and that is exactly what I did. I fly the wing that had a slight leak until it went completely empty, and flew with my non leaking wing to the FBO to repair the leak.

Also, the fuel source has to get to the lower explosive limit on the concentration and stay below the Upper explosive limit. It is tough to get the the LEL outside. 3 feet above a puddle of gasoline is not explosive outside, and that has the factors of safety for determine an explosive area based on fire codes.

Where in the manual does it say that? I can't find it the J manual.

[mooniac15u]

Where in the manual does it say that? I can't find it the J manual.

 

That was the procedure for maximum endurance in the manual for my 1963 M20D.

[mooniac15u]

Take a look in the M20C manual in downloads (http://mooneyspace.com/files/file/34-owners-manual-1965-mooney-m20c-mark-21/).  On page 21 under Fuel Management it suggests burning an hour of fuel out of one tank and then burning the other dry.