Max fuel differential

[Marek7]

I'm struggling to find some numbers. What is the max allowable fuel differential in the for a m20k.   I have the auxiliary tanks, however one has inevitably started to leak. The plan is to cap that one and fly it back to be resealed. The mains are fine.  Would I be able to still safely use the auxiliary tank on the opposite wing while one remains bone dry?   

The extra range would be very helpful for my ferry trip.

[kortopates]

There is no max differential published. But there is an implied one due to the limitation in the POH not to take off without at least 12 gal per tank. If you have a leak in the extended range tank only, you shouldn't have a problem with the main tank at half capacity. The extended tank is dry when the main is at half (18 gal).And likely you can more in than that before you get to the leak. I assume your leak is much worse than a seep, since a seep would not prevent you using it.


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[Greg_D]

4 hours ago, kortopates said:

There is no max differential published. But there is an implied one due to the limitation in the POH not to take off without at least 12 gal per tank. If you have a leak in the extended range tank only, you shouldn't have a problem with the main tank at half capacity. The extended tank is dry when the main is at half (18 gal).And likely you can more in than that before you get to the leak. I assume your leak is much worse than a seep, since a seep would not prevent you using it.


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Where exactly is that limitation in the POH?  My POH just has a note that states takeoff maneuvers with less than 12 gallons in the *selected* tank were not demonstrated.

[N201MKTurbo]

I've flown my plane with one empty tank and one full tank. No big deal. 

But flying without a spare tank is not something you want to do a major cross country with.

[gsxrpilot]

I flew my K with the left tank full and the right tank stripped and obviously empty. It was only a short flight, but it flew and landed just fine.

[ziggysanchez]

I did the same today. 20 gallons in the left and empty on the right. No problem.

[kortopates]

2 hours ago, Greg_D said:

Where exactly is that limitation in the POH?  My POH just has a note that states takeoff maneuvers with less than 12 gallons in the *selected* tank were not demonstrated.

In the limitations section and you are correct it says the "selected" tank making you a test pilot because of the concern of unporting the fuel pick up. 

Of course ferry flights would be the only time most of us would consider flying this way.

[Greg_D]

Just now, kortopates said:

In the limitations section and you are correct it says the "selected" tank making you a test pilot because of the concern of unporting the fuel pick up. 

Of course ferry flights would be the only time most of us would consider flying this way.

My old C model used to have a procedure in the book where you would run a tank dry.  I will still run one side down to a gallon or two and leave at least 12 in the other side for landing.

Regardless, there is no limitation, implied or otherwise on fuel imbalance that I am aware of.

[Hank]

28 minutes ago, Greg_D said:

My old C model used to have a procedure in the book where you would run a tank dry.  I will still run one side down to a gallon or two and leave at least 12 in the other side for landing.

Regardless, there is no limitation, implied or otherwise on fuel imbalance that I am aware of.

The Owner's Manual for my C says to takeoff and fly for an hiur on one tank, then switch tanks and fly the other tank empty.  I don't do that, but it's approved by the manufacturer . . . . 

[jlunseth]

Well, the 12 gallon limitation is there because the angle of the aircraft is so high on takeoff.  There has to be sufficient fuel so that even at a high angle, fuel will reach the outlet. You only need twelve gallons in one tank, and the valve switched to that tank, and you are ok.  My standard practice in my 231 is pretty much what Hank describes.  I take off and climb on one tank, and once I reach cruise, I will switch to the other tank.  I don’t run it completely dry, but pretty close.  Then I know that I have plenty of fuel in the second tank for descent and landing.  Its not a problem in my Mooney if the tanks are out of balance.

[gsxrpilot]

9 hours ago, Greg_D said:

My old C model used to have a procedure in the book where you would run a tank dry.  I will still run one side down to a gallon or two and leave at least 12 in the other side for landing.

I'm in the "run a tank dry" camp.  I did this in my C and now do it regularly in my K. Take off on the Right tank and burn 15 gal or so. Switch to the Left and run it dry. Switch back to the Right for the remainder of the flight and landing. 

There are a few conditions such as I always run the tank dry at altitude and in cruise. Never on the decent or in the pattern or on approach.