Switch Tanks Before Takeoff

[blaine beaven]

On 12/9/2023 at 8:31 AM, Pinecone said:

Somewhere on MS there is a 3D design for a holder that uses a spring clamp to hold onto the nose gear door and holds a GATS jar to catch the fuel. 

My friend had to modify the design a bit as it was a bit too small for a recent GATS jar.

That seems like a lot of work when you can just sump fuel from the port on the belly, go into the cabin and switch tanks, then sump it again - all without ever pulling the ring on the floor. 

[EricJ]

55 minutes ago, blaine beaven said:

That seems like a lot of work when you can just sump fuel from the port on the belly, go into the cabin and switch tanks, then sump it again - all without ever pulling the ring on the floor. 

On many Mooneys you can't sump it from outside.   It's not the kind where you can probe it and make it drain, it only drains from the pull ring.

[M20F-1968]

On 12/8/2023 at 11:48 AM, PT20J said:

I switch tanks every half hour. I like to keep the plane balanced and also those brass valves like to be exercised or they get stiff. 

I usually taxi out on one tank and switch before run up. This is primarily to make sure the valve turns freely - I’m really not much concerned that somehow fuel won’t flow through the lines. And, I sumped the tanks, so I know there is no water (BTW, in 6,000 hours of flying a lot of different make and model airplanes, I have found a significant amount of water in the fuel tanks exactly ONCE. But, I still sump the tanks. You never know when twice will occur.)

If you want to avoid the biggest risk, check the handle attachment. The only failure I personally know about was a friend in an Archer that had the screw attaching the handle back out and jam the handle in the trim around the selector in a position between tanks where no fuel flowed. In a slight panic, he tried to force it and jammed it worse. He finally got it unstuck. I could easily see the handle on my J coming loose and getting dropped and rolling under the seat. And then there are models with the valves that you cannot hardly reach without gorilla arms or an extension…

Skip

 

I keep a second handle in the side pocket next to the pilot's seat.  The handle is secured with a roll pin which fits into a slot in the handle, and a set screw.  The set screw keeps it on the shaft.  Both the set screw and the roll pin allow the handle to turn the shaft.  But, if the handle falls off, the second spare handle can be put in place to turn the shaft.  Better than a pair or pliers.

John Breda

[blaine beaven]

5 hours ago, EricJ said:

On many Mooneys you can't sump it from outside.   It's not the kind where you can probe it and make it drain, it only drains from the pull ring.

That makes sense! I guess I am lucky that mine will drain with probing

[Pinecone]

9 hours ago, Schllc said:

Well, not sure how to answer that to be honest.  Not sure what difference it would make if I was landing...  

I think I could count the times I landed with 10gallons or less on one hand.  I do not like to cut it that close

Maybe not needed for landing, but what about a go around?  

[Pinecone]

9 hours ago, blaine beaven said:

That seems like a lot of work when you can just sump fuel from the port on the belly, go into the cabin and switch tanks, then sump it again - all without ever pulling the ring on the floor. 

On some models at least, it is recommended to NOT use a probe for that drain.  To only use the pull ring.

[Schllc]

18 minutes ago, Pinecone said:

Maybe not needed for landing, but what about a go around?  

Well, if I find myself landing with less than 10 gallons on board I would say there are a few more mistakes to review, but either way, I would be on the fullest tank, which is the best option I would have available.  
I tend to tanker fuel, I know a lot of guys don’t, but in the big bore engines, a few hundred extra pounds doesn’t have an attributable affect on performance so I don’t really see any reason to not carry extra. I seldom go anywhere with less than half tanks. I prefer the options extra fuel provides. 
But the question was about switching tanks before take off, and that is not part of my routine. 

[blaine beaven]

4 hours ago, Pinecone said:

On some models at least, it is recommended to NOT use a probe for that drain.  To only use the pull ring.

Good to know. I’ll take a read my J model POH again to see if there is any restriction on this. I learn something every day on this forum!

[Pinecone]

12 hours ago, Schllc said:

Well, if I find myself landing with less than 10 gallons on board I would say there are a few more mistakes to review, but either way, I would be on the fullest tank, which is the best option I would have available.  
I tend to tanker fuel, I know a lot of guys don’t, but in the big bore engines, a few hundred extra pounds doesn’t have an attributable affect on performance so I don’t really see any reason to not carry extra. I seldom go anywhere with less than half tanks. I prefer the options extra fuel provides. 
But the question was about switching tanks before take off, and that is not part of my routine. 

And threads drift.

Ok, so say 15 gallons.  The actual number is not important.  The concept is.  If you are low fuel, it is better to have all your fuel in one tank instead of two.

[Schllc]

2 hours ago, Pinecone said:

And threads drift.

Ok, so say 15 gallons.  The actual number is not important.  The concept is.  If you are low fuel, it is better to have all your fuel in one tank instead of two.

If i was landing i would say it is not that important.  If i was 10 gallons away from landing i would say yes!

[Shadrach]

14 hours ago, Schllc said:

Well, if I find myself landing with less than 10 gallons on board I would say there are a few more mistakes to review, but either way, I would be on the fullest tank, which is the best option I would have available.  
I tend to tanker fuel, I know a lot of guys don’t, but in the big bore engines, a few hundred extra pounds doesn’t have an attributable affect on performance so I don’t really see any reason to not carry extra. I seldom go anywhere with less than half tanks. I prefer the options extra fuel provides. 
But the question was about switching tanks before take off, and that is not part of my routine. 

As a non “big bore” operator (my IO360 bore is a paltry 5.15 inches compared to the 5.25 inches of the TSIO550G), I’m curious if you’ve ever flown a lightweight four-cylinder Mooney? The Acclaim’s factory stated empty weight of 2380lbs (what’s yours weigh) is 700lbs heavier than the actual weight of my modest little F model. That’s a 40% delta. Fortunately the “Big Bores” come with 280hp up front (would you look at that, another 40% delta). That surplus in power makes all the difference in cruise.  In terms of runway performance and initial climb, you’re right, a few hundred pounds isn’t really going to make a big difference for a “big bore”… It’s always going to take nearly twice as much distance to clear 50’ and nearly 1000’ more to get stopped.

 

[Schllc]

IF you took that as a slight, or as a suggestion that the big more mooney's are "better", that was not my intention, nor do I believe that is true.

I have no time in a four cylinder mooney, I have some time in a K but nothing in a non turbo charged other than the ovation.  I realize the four cylinders are a lot lighter, and the take off and landing distances are shorter, but I am not sure what your point was regarding the delta.   Does the gross weight have something to do with switching tanks?

[Shadrach]

2 minutes ago, Schllc said:

IF you took that as a slight, or as a suggestion that the big more mooney's are "better", that was not my intention, nor do I believe that is true.

I have no time in a four cylinder mooney, I have some time in a K but nothing in a non turbo charged other than the ovation.  I realize the four cylinders are a lot lighter, and the take off and landing distances are shorter, but I am not sure what your point was regarding the delta.   Does the gross weight have something to do with switching tanks?

Sorry for the thread creep. I did not take it as a slight. More of a misunderstanding of the performance differences between the models. You’re not the first to do it. The response was entirely based on the notion that the “big bores” can tanker fuel because they have such a surplus of power that they can better handle it.  

I understand why you would not want to land with less than 10 gallons, I feel the same way and that equates to an hour of flight at cruise in my bird. I will make an exception if I’m close to home poking holes in the sky on a VFR day.  One exception I will not make is fuel location. I manage fuel in such a way that if I have less than 15 gallons on board, it’s always in one tank.
 

[Schllc]

Being that I am completely unfamiliar with the W&B of the mid body's in general, I didn't know that.   So, it apparently makes sense to tanker in the more efficient models as well.

Good to know.

 

[Shadrach]

23 hours ago, Schllc said:

Being that I am completely unfamiliar with the W&B of the mid body's in general, I didn't know that.   So, it apparently makes sense to tanker in the more efficient models as well.

Good to know.

 

It’s a testament to the design that it and has been able to adapt so many different configurations and power plants.

If you have an opportunity to fly a lightweight (Some are not so svelte) mid or short body, you should check it out. There are advantages. My solo takeoff weight for a 500nm flight is 2170lbs or 570lbs under gross. Plenty of surplus to tanker fuel and or anything else I might want to carry

[Schllc]

I will fly any Mooney anyone will let me!

I have time in over 30 of them so far!

[Deb]

2 hours ago, Schllc said:

4 hours ago, Pinecone said:

And threads drift.

Ok, so say 15 gallons.  The actual number is not important.  The concept is.  If you are low fuel, it is better to have all your fuel in one tank instead of two.

If i was landing i would say it is not that important.  If i was 10 gallons away from landing i would say yes!

Our Ovation 2 POH states:

FUEL LIMITATIONS

–WARNING– 
Takeoff maneuvers when the selected tank contains less than 12 gallons of fuel have not been demonstrated.

So we’d want more than 12 gallons in the selected tank for landing in case we needed to go around.

[Fly Boomer]

On 12/12/2023 at 9:57 PM, cliffy said:

I guess I'm of the opinion that even if you check it to make sure it works it only tells you it worked that time. No guarantee that it will work

the next time even if you check before takeoff.

When I asked the original question, I was only thinking about assuring myself that I could reliably run the engine from both tanks.  You and some others have pointed out that, even with good gas in the tank, if the selector malfunctions, it's not much different than having an empty tank.

[Fly Boomer]

22 hours ago, Shadrach said:

I manage fuel in such a way that if I have less than 15 gallons on board, it’s always in one tank.

I like this plan.  Seven in each tank=no bueno.

[Fly Boomer]

On 12/13/2023 at 7:23 AM, Pinecone said:

The other reason to run one dry is that you reduce the risk of unporting the fuel pickup on the tank with fuel.

Have you had or heard of issues running a tank dry?  I know guys with carbureted engines that do it, but I also know guys with fuel injection who say that the engine has a tendency to just crap out.  With turbocharging, it could be a long glide down to an altitude with enough air for a relight.

[GeeBee]

With Continental fuel injection you are being really hard on the mechanical fuel pump by running it dry. Not something you want to make a habit.

[cliffy]

I flew a Navajo  for a few years and we would fly the aux tanks (at cruise) until empty by watching the fuel pressure gauge to see when it started to fluctuate (air being drawn into the system-empty tank). Never lost power doing it that way and the aux tanks were completely empty. Tank valves were right by our right hand below the seat so they were easy to get to and we were watching the FP gauge like a hawk. In a couple thousand hours never had an issue. 

Had a friend who did the same thing in a Twin Beech with its 5 tanks also. Running them dry can be done without problems IF you watch what you are doing. I wouldn't make it a practice to run them dry to the point of engine shutdown though. Besides it scares the crap out of the passengers. 

In the case of the Mooney I have no idea why one would need to run a tank that dry on a regular basis. I can see in it in an emergency where you might need to do that but then you've got other problems to deal with  lack of planning for contingencies or say ferry across the ocean!  If you have regular flights where the fuel required is so close to the limit that you need to always run a tank dry then again you're pushing the envelope too close. IMO   Someday that will bite you. 

I've flown a Mooney with one tank empty and one full for maintenance (tank patch) and you really can't tell the difference between that and both full. 

Just because its legal to plan a 30 min reserve doesn't make it a smart idea. 

[Fly Boomer]

3 minutes ago, cliffy said:

I have no idea why one would need to run a tank that dry on a regular basis

Good point.  With 100 gallons of capacity, I can't sit still long enough for this to be a problem.  I guess the question was just academic.

[GeeBee]

A Navajo has a Lycoming with a diaphragm pump. I've ran Navajos dry too and you're right. Watch for the flutter in FF and you can do it. A Continental has a vane type pump. The vane and the vane drive shaft are fuel lubricated. Lack of fuel will cause pump failure fairly quickly. By the time you see flutter in FF, the pump is starving for lubrication. So if you're of a mind to do this with a Continental, make sure your High Boost Electric pump is working, because you're going to need it eventually.

[Shadrach]

20 minutes ago, Fly Boomer said:

I like this plan.  Seven in each tank=no bueno.

It’s certainly not a very conservative way to distribute fuel. I have found that Mooneys are not very sensitive to fuel  imbalance. At least not those with 64gl useable or less.