long range tanks

[rturbett]

I

I've seen a few Mooney's advertised with long range tanks.   Are these still treated as two tanks- left and right?  Any different fuel management concerns?  

I was taught to leave tanks mostly full when idle to reduce condensation - any different thoughts?

Thanks,

Rob

 

[wombat]

The Monroy long-range tanks I have are physically separate, but there is an open connection between them (two, actually) so there is no fuel management overhead.   From the pilot perspective in flight, it's a single tank in each wing.

[201er]

34 minutes ago, rturbett said:

I

I've seen a few Mooney's advertised with long range tanks.   Are these still treated as two tanks- left and right?  Any different fuel management concerns?  

I was taught to leave tanks mostly full when idle to reduce condensation - any different thoughts?

Thanks,

Rob

 

I have the Monroy tanks on my 201. From a fueling perspective, they are separate. Top the inboard tank first, then the outboard. If the outboard tank is topped and your remove the inboard cap, you will have a gas-geyser so don't do that. The outboard is gravity fed into the inboard so there is no additional fuel management in the cockpit. However, the fuel gauges are totally inaccurate as they read the inboard tank except when full and empty. The inboard tank maintains mid-level for most of the time as the outboard keeps replenishing the inboard. Easily managed using fuel flow and totalizator instead.

This may be slightly different on long bodies with factory long range tanks. I think they only have one fuel cap per wing.

Never had a single drop of water from condensation regardless of fill level despite being parked outside over a decade. However, one time the fuel cap o-ring failed and I pulled 6 cups of water out of the sump at night.

The increased range is tremendous not to mention fuel savings by ferrying your own gas when visiting expensive places.

64g standard vs 98g long range may not sound like that much of an increase but in practice it is due to reserves. On an IFR flight you may well be planning to arrive to destination with 24+ gallons to have fuel remaining for diversion plus reserves.

That's 64g - 24 = 40g usable (about 4 hours/600nm range)
vs
98g - 24 = 74g usable (about 7.4 hours/1110nm)

So, 34 extra gallons nearly doubles your real-world range with comfortable reserves.

[Fly Boomer]

1 hour ago, rturbett said:

I

I've seen a few Mooney's advertised with long range tanks.   Are these still treated as two tanks- left and right?  Any different fuel management concerns?  

I was taught to leave tanks mostly full when idle to reduce condensation - any different thoughts?

Thanks,

Rob

 

The 252 has four fuel caps but, as @wombat points out the two tanks in each wing are connected.  The four caps allow quick fueling, and the pipes or tubes connecting the two tanks in each wing are large enough to allow fuel to flow from the outboard tank to the inboard tank during flight.  The wrinkle is that the fuel level senders and the fuel gauges were not changed so, if you start with full tanks, you have to burn off a ton of fuel before the gauges come off full.  With over 100 gallon capacity on the 252, it may not be a good idea to fill after each flight.  On the next flight, If you want to achieve a balance between fuel load, passenger load, and baggage load, it's going to limit your choices with 600 pounds of fuel in the wings.

[M20F]

Don Maxwell bought the STC from Jose Monroy.  My understanding is they have a DER approval in place to get around FAA/PMA.  The FAA though has not yet processed the STC transfer.  I am on the list for the tanks but as of this writing no news yet.  

[Pinecone]

I have them in my 252.  I just wish the line between the tanks was larger.

It is very hard to get them FULL.  If you fill the inboards first, as you do so, fuel is flowing into the outboards.  This continues after you stop and put the cap on. Then you fill the outboards, and the fuel is flowing back into the inboard.  You fill to the top.

They you repeat on the other side.  And go back to the first side, and it takes several more gallons.  If you wait longer, it takes more.

When I calibrated my fuel dipsticks, I could hear air bubbling out of the inboards when I had already put more in the tanks than they are supposed to hold. 

Mine as supposed to be 52 per side.  From running one side to engine stumbling, I was able to put 55 in that tank, doing it 2.5 gallons at a time and allowing 5 minutes between fuel additions.

[Fritz1]

I have the standard tanks in my Bravo, 89 gal book, if you really top them right under the fuel cap O-rings they hold 101 gal usable, this is already 600 lb, since I keep the tanks always full as advised by weep no more I have to offload fuel when I want to fly more than one passenger, keep Jerrycans in the hangar to offload 30 gal with siphon, and this is about all I can get out with the siphon, long bodies can hold up to 136 gal, my airplane would be over gross with just myself without a toothbrush, bottom line long range tanks turn a lot of birds into one person airplanes and you have to offload fuel when you always keep the tanks full in the hangar and want to fly passengers

[201er]

34 minutes ago, Pinecone said:

They you repeat on the other side.  And go back to the first side, and it takes several more gallons.  If you wait longer, it takes more.

When I calibrated my fuel dipsticks, I could hear air bubbling out of the inboards when I had already put more in the tanks than they are supposed to hold. 

Mine as supposed to be 52 per side.  From running one side to engine stumbling, I was able to put 55 in that tank, doing it 2.5 gallons at a time and allowing 5 minutes between fuel additions.

You can cheat more than intended amount of fuel into them but it isn't required. You should easily be able to make rated capacity just by topping inboards and then outboards rapidly without any more back and forth.

Be careful overfilling like this because on a hot day, the fuel can expand and start pouring out the vent. Not to mention more weight than expected.

[wombat]

I think the extra fuel that you can get into them after topping off is from the rectangular cavities at the top where the ribs are, they hold air that then burbles out or slowly bubbles out from between those rib sections and makes its way up to the filler neck.   

And as @201er says, if you don't leave room for expansion, you could lose a bunch of money ... I mean destroy the environment .... I mean vent overboard a bunch of fuel if it doesn't have any expansion room and it heats up.

[ZuluZulu]

8 hours ago, rturbett said:

I

I've seen a few Mooney's advertised with long range tanks.   Are these still treated as two tanks- left and right?  Any different fuel management concerns?  

I was taught to leave tanks mostly full when idle to reduce condensation - any different thoughts?

Thanks,

Rob

 

Yes, my plane has them and there is literally a sticker on top of the fuel selector covering up the original "32 GAL" capacity and making it "47" instead for each tank.  There's nothing to manage from the cockpit other than selecting the L or R tank.  

As others have said, fill the inboard mains first when fueling, followed by the outboard Monroys.

Remember to sump all four quick drains during your preflight instead of just the two.

The only downside to leaving them full is it's a lot of weight and if you unexpectedly have an extra passenger show up for an impromptu flight you could be overweight.  I've tried to keep mine full unless I was expecting a trip where useful load would be important: camping gear, hot and high airports, four people, etc.  I've been told by some that, supposedly, keeping them all full leads to leaks sooner because of all the extra weight on the sealant.  Not sure if that's true.  But if you're landing with close to a full fuel load often, you probably should make your landings as smooth as possible just to be nice to your tanks.

Another thing to know is there are no approved bladder replacements for the Monroys, so if you get the long range tanks you are stuck with doing strips and reseals once the leaks start, or you have to downgrade to replacing only the mains with bladders and losing the extra capacity.

With that said I love them.  Over the weekend I set my new personal best of 6 hours, 20 minutes nonstop, covering almost 1000 nm with a 10-20 knot headwind.  And landed with almost three more hours of reserves.

[rturbett]

Great info- Thank you

Rob

[Pinecone]

15 hours ago, 201er said:

You can cheat more than intended amount of fuel into them but it isn't required. You should easily be able to make rated capacity just by topping inboards and then outboards rapidly without any more back and forth.

Be careful overfilling like this because on a hot day, the fuel can expand and start pouring out the vent. Not to mention more weight than expected.

Agreed with your second point.  I only do that if I am taking off right away.  Normally when fuel is cheap at that airport.

Other wise I top one side, then the other, than retop the first and then the other again.  That is all.

Not in my plane.  If I only top the inboards then outboards, then wait 30 minutes, I can put more than 10 gallons in.

I have found that filling outboard, then inboard gets me closer to full than inboards first.

[Pinecone]

10 hours ago, ZuluZulu said:

With that said I love them.  Over the weekend I set my new personal best of 6 hours, 20 minutes nonstop, covering almost 1000 nm with a 10-20 knot headwind.  And landed with almost three more hours of reserves.

I recently did 7 hours (and 3 seconds according to Flight Aware) and did 1333 nm and had over 3 hours remaining.  But I had a tail wind the whole way.  Tailwind peaked at 52 knots for a bit.

[Fly Boomer]

1 hour ago, Pinecone said:

I have found that filling outboard, then inboard gets me closer to full than inboards first.

Reading this topic got me thinking about trying something similar to your technique.  Outboard, then inboard, then outboard again if trying for max fuel.

[Danb]

6 hours ago, Pinecone said:

I recently did 7 hours (and 3 seconds according to Flight Aware) and did 1333 nm and had over 3 hours remaining.  But I had a tail wind the whole way.  Tailwind peaked at 52 knots for a bit.

Hope I get your tailwinds this week I’m flying Wilmington De to St Louis then Albuquerque on the Vegas return I’m hoping for good winds staying in KC then don’t know where next. I’m generally unlucky on the winds, limited to 18,000 due to basic med.

[Pinecone]

I have the same altitude limitation.

This was part of the trip to Mooney Max and I had tailwinds to Longview and then tailwings Denver to MD.