I have a PA-24 250 with Osborne Tip Tanks. This gives me two fuel selectors a RH Main/RH Tip and a LH Main/LH Tip. I can have two tanks feeding fuel and the same time.

Is there any reason I should not select both mains when landing?

Thank you,

Bill

I do not recommend using the "both" two tank option with the tip tanks or the main tanks because they will not drain equally, and you will end up with a heavy wing. Also, it is very easy to loose track of what amount of fuel in each tank, especially on a long leg. I have a routine that keeps my 250 with 60 gallons in the wings and 30 gallons in the tip reasonably well balance and allows me to keep track of what tanks have the most fuel. Do not land with both mains selected, espescially if one of them is low on gas. You might end up with a big gulp of air in the fuel system on short final.

This has worked well for me since 1977 assuming all tanks are full:
Take off and climb on one main on one main and fly on until 30 minutes after take off.
Switch to the other main for 1/2 hour.
Switch to a tip tank for 1/2 hour.
Switch to the other tip for 1/2 hour.
Back to first tip for 1/2.
Back to second tip for 1/2 hour.
Switch to the "heavy" side main for 1/2 hour.
Alternate mains at 1/2 intervals until the end of the flight.
Land with the selector on the fullest main only.

Jim,

I have followed a very similar routine as you outlined for the 3 years I've had my 250. On my last flight I was returning to MN from Chandler Arizona with my 4 year old daughter. Everything was going well we were VFR on an IFR flight plan. I had finished the last 20 minutes of my left Tip and was going to switch to the right main. At that time my daughter got sick (she was sitting front right). Apparently in my hast I switch to right tip and not main. Everything was going fine for next 15 minutes until it got engine got rough and losing power. I hit carb heat, fuel pump, finally switch to left main all turned out good. I think this took me all of 15 - 30 seconds. Not enough altitude loss to have ATC call me up. This has made me think about my fuel management practices a lot lately.

Bill

I burn them dry, aux tanks first, then mains, I normally never go back to a tank. Never experienced a fuel imbalance.

If fuel is not critical I try to keep the mains somewhat balanced. If fuel is critical I don't want to be swapping tanks near the end.

Just my 2 cents

Mark