Switch Tanks Before Takeoff

[Schllc]

Just now, T. Peterson said:

Maybe that’s why our oaths are to the Constitution and not to the Government?

exactly...

this has potential for a huge thread drift!!!

[T. Peterson]

2 minutes ago, Schllc said:

exactly...

this has potential for a huge thread drift!!!

Yessir, it certainly does!! Therefore I am going to try real hard to leave it alone!

[cliffy]

Isn't switching tanks patriotic?  :-)

If the tank valve was electric I might be more worried about its non-function before flight but even then

if I had a full tank or landed with ample in the selected tank one could still land somewhere else IF the tank

selector didn't function as long as it wasn't run dry before the switch was tried. . 

Here's a question- IF your procedure is to drain a tank completely and then switch what happens if the selector valve doesn't work at that time?    Just thinking aloud.  :-)

[Hank]

30 minutes ago, cliffy said:

Here's a question- IF your procedure is to drain a tank completely and then switch what happens if the selector valve doesn't work at that time?    Just thinking aloud.  :-)

Then you land and get it fixed!

[T. Peterson]

1 hour ago, cliffy said:

Isn't switching tanks patriotic?  :-)

If the tank valve was electric I might be more worried about its non-function before flight but even then

if I had a full tank or landed with ample in the selected tank one could still land somewhere else IF the tank

selector didn't function as long as it wasn't run dry before the switch was tried. . 

Here's a question- IF your procedure is to drain a tank completely and then switch what happens if the selector valve doesn't work at that time?    Just thinking aloud.  :-)

Then you are between the proverbial rock and a hard place!

Actually, your point is well taken. As a relative newbie to GA and small airplanes compared to the vast experience on this forum, I am very interested in this discussion. Many good points have been made and I am taking them all under advisement as I plan my own fuel management strategy. So far, my strategy has been to top off at every stop. My wife and I don’t like to fly more than 3 hour legs so I always land with plenty of fuel. However we would like to at least take some shorter trips with another couple.  My UL is 930 lbs so I will launching with no more than 50 gallons or even less. This will make fuel management critical. 
I totally get the wisdom of having enough fuel in the landing tank to safely cover a go around which implies by default that the cruising tank is going to be sucked down much further than the landing tank. I know many excellent pilots on this forum speak of actually emptying the cruising tank, but that’s a little rich for my blood. As you pointed out if something should go wrong and you are out of gas in one tank and can’t access the other, you will probably say a bad word!

 I’m thinking that landing with 12 gallons in one tank and 5 in the other is as risky as I want to go. Of course that is not written in stone, and I certainly welcome further insight from the group.

[dkkim73]

@wombat

Thoughtful response. 

So, do you "minimize" switching tanks in flight, IAW points #2 and #3? Ie. not do it unless you have an operational need so as one tank running low or a noticable lateral imbalance? 

 

[cliffy]

12 hours ago, Hank said:

Then you land and get it fixed!

So the tank is empty and the valve doesn't turn so you do what? Again just thinking aloud :-)

There again, how many times has this ever happened? Can anyone cite an example?

It a simple twist plug mechanical valve. The only one I have ever had was on my C-140 and it just got tight to turn over time. Lots of notice..

Could be we are getting worked up over something highly unlikely to happen 

For me the longer I fly (now over 60 years) the more cautious I get. Age has a way of tempering exuberance.

I carry as much fuel as I can and in my case that's always full tanks. I always land with a couple hours left in the tanks. 

In our short body Mooneys we only have 2 pounds of unuseable fuel on each side (4 pounds total), 1/3 of a gallon each side. Some of our tribe have over a gallon each side. In testing mine I have drained it dry in flight (risk factor accepted for those test flights) and found I can use ALL 26 gallons if needed with a side slip flight attitude. AND when refilled it is exactly 26 gallons in each tank (separate flight test for each tank :-)  )

I don't normally operate in that regime but its nice to know what my airplane can do if it was ever needed. 

No different than hand flying every 3rd approach to mins (or 50 ft CAT III) in good weather just in case IT was ever needed. 

Knowing what you and your airplane is capable of keeps one out of trouble. Knowing that, you don;t have to venture into the realm of the unknown at a difficult time can, it can save your life.

Thinking about ways out of trouble long before faced with the actual event may save your life.

I've always  treated flying as a game of baseball and I'm the catcher. Everyone is throwing  curveballs at me from all directions on the field and its my job to catch every one of them. Once you make a game out of it that lowers the anxiety of what can go wrong this time because you are ahead of the game. You're always thinking ahead. It actually gets fun when nothing can catch you by surprise. 

Experience is the greatest teacher. All the training in the world can't replace experience.

You're not a safe pilot until you have been tempered and you're not tempered until you do something in an airplane that scares the crap out of you and you know you did it, to yourself. Flying takes on an entirely different perspective after that. 

[wombat]

13 hours ago, dkkim73 said:

@wombat

Thoughtful response. 

So, do you "minimize" switching tanks in flight, IAW points #2 and #3? Ie. not do it unless you have an operational need so as one tank running low or a noticable lateral imbalance? 

 

Not sure I'd call it minimizing, but I don't do it every 30 minutes or less.   My GPS currently has a 30 minute "Switch Tanks" timer that I should get rid of because I mostly ignore it.  My perceived risk for this failure mode (valve failure in flight) is very low so I typically don't think about it at all as a risk, although I do watch the fuel flow during and shortly after switching, for perhaps 10 seconds.   My typical pattern would be to switch tanks maybe every hour, so every 20 gallons out of 52.5 per side.

There are incidents & accidents for throttle linkages failing in flight as well but not enough that I make fewer throttle changes  to minimize the risk and I view the fuel valve the same way.

Overall I think the risk of some sort of failure that can be identified on the ground through a pre-takeoff fuel tank switch is high enough that it's worth doing, but the overall risk mitigated by this is still quite low and if someone didn't do it my concern would be much more about what else they are failing to do rather than this specific risk.  Is all of preflight not worth it to them?  What about annual inspection?  Medical? BFR?  IFR currency? Being licensed at all?  

[dkkim73]

21 hours ago, Schllc said:

exactly...

this has potential for a huge thread drift!!!

Blame me. More than a little drift; I've already accidentally landed on a parallel threadway... 

[Hank]

6 minutes ago, dkkim73 said:

Blame me. More than a little drift; I've already accidentally landed on a parallel threadway... 

Landing on one is OK. Just be careful creating those parallel threadways . . . .

[PeteMc]

7 hours ago, cliffy said:

So the tank is empty and the valve doesn't turn so you do what? Again just thinking aloud :-)

There again, how many times has this ever happened? Can anyone cite an example?

I know there are a lot of people that teach and recommend that you fly one tank dry and then continue on with the other tank.  But your question is EXACTLY why I don't do that.  Over the years, equipment, cables, connectors, switches, etc., etc., have all worked on a show UNTIL THEY DON'T. 

And I have heard of people talking about how the handle has come off in their hand.  Sure, you can fiddle around with it and probably get it to work, as long as the shaft didn't break off with the handle.  But even if it just the handle, you're now with a dead engine cuz you ran the tank dry...  Best Glide or do you fiddle with the handle?   

[Fly Boomer]

1 hour ago, wombat said:

if someone didn't do it my concern would be much more about what else they are failing to do rather than this specific risk.  Is all of preflight not worth it to them?  What about annual inspection?  Medical? BFR?  IFR currency? Being licensed at all?  

You might be surprised.  I don't know of anyone who widely advertises these shortcomings, but word gets around the community eventually.

[Andy95W]

I find it ironic that folks worry about single points of failure (such as the fuel valve or only one GPS) but have no problem flying over mountains, at night, or in low IMC in a single engine airplane.

[wombat]

8 minutes ago, Andy95W said:

I find it ironic that folks worry about single points of failure (such as the fuel valve or only one GPS) but have no problem flying over mountains, at night, or in low IMC in a single engine airplane.

Or flying an instrument approach or any of the visual approach indicator systems on final approach.... If your engine quits, you will not be landing on the runway this time.

But it's all about the different risk profile that different people are willing to accept.  Some people are confident that their engine will not quit in cruise flight, therefore their assessment of the risk of night flight over mountains is low.   Some people have low confidence in their GPS hardware, so a second GPS makes them feel safer.

Probably worthwhile to look at what the causes of actual accidents are and mitigate those rather than perceived risks that have negligible actual accidents.

[Fly Boomer]

14 minutes ago, wombat said:

But it's all about the different risk profile that different people are willing to accept.  Some people are confident that their engine will not quit in cruise flight, therefore their assessment of the risk of night flight over mountains is low.   Some people have low confidence in their GPS hardware, so a second GPS makes them feel safer.

Assuming they have thought about it at all.  I see quite a lot of "I've been flying this airplane for a zillion hours, and it's never happened -- therefore, it never will".

[T. Peterson]

We probably all have some inconsistencies in our risk assessments, but I thought it very unkind for you fellas to point out all of mine!!

[Hank]

27 minutes ago, T. Peterson said:

We probably all have some inconsistencies in our risk assessments, but I thought it very unkind for you fellas to point out all of mine!!

You have the most comprehensive list!

[dkkim73]

4 hours ago, PeteMc said:

And I have heard of people talking about how the handle has come off in their hand.  

OK, I'll bite as a new owner. 

Is there anything about our planes that makes this more likely than in, say, the PA-28's? Is it a known weak point? 

[PeteMc]

9 minutes ago, dkkim73 said:

OK, I'll bite as a new owner. 

Is there anything about our planes that makes this more likely than in, say, the PA-28's? Is it a known weak point? 

Sorry!  Didn't mean to give you the wrong impression....   I actually don't remember what planes I had heard about the handles come off.  It's just one of those things you read or hear about over the years.  And now that you mention it, I think a PA28 might have been one of the planes.  My point was more on the discussion of the possible failure and how you can't go by "it worked a minute ago!" concept.  MANY things on the Mooney may out last me, but that doesn't stop something from failing while in-flight.  (Have I told you how I shut down JFK when a cylinder decided to burn through... )  

It's just that I think it's better to think about the What If scenarios.  In my case, I'm not going to drain a tank, as I personally don't think it's a smart thing to do.  (Maybe as a test to really empty the tank at 6000AGL over an Apt.)  If it just so happens that the valve screws up, the handle/shaft does break, it was a sunny day and I was oblivious to the fact the sump on the other tank has been leaking for the last hour and there's no gas in the other tank (OH NO ).  I was just point out that you should have a Plan and maybe a Plan B just in case.  For me, if I can't switch tanks, I hopefully will have enough in the orig. tank to get to an airport or get out of the worst of the mountains to find a nice road in a valley. 

[Shadrach]

18 hours ago, PeteMc said:

I know there are a lot of people that teach and recommend that you fly one tank dry and then continue on with the other tank.  But your question is EXACTLY why I don't do that.  Over the years, equipment, cables, connectors, switches, etc., etc., have all worked on a show UNTIL THEY DON'T. 

And I have heard of people talking about how the handle has come off in their hand.  Sure, you can fiddle around with it and probably get it to work, as long as the shaft didn't break off with the handle.  But even if it just the handle, you're now with a dead engine cuz you ran the tank dry...  Best Glide or do you fiddle with the handle?   

Do you think an analysis of fuel exhaustion accidents would show more incidents involving malfunctioning selector switches or unselected fuel tanks with usable fuel inside?

[PeteMc]

1 hour ago, Shadrach said:

Do you think an analysis of fuel exhaustion accidents would show more incidents involving malfunctioning selector switches or unselected fuel tanks with usable fuel inside?

I think the numbers probably show I'm over thinking.  But for years my job was to think of what could go wrong and have a plan.  Even when the odds were miniscule, you still had to go through the thought process.  (And the WORST JINX EVER is when one of the crew would say "this is going to be an easy show."  Something ALWAYS happened! )

 

[Shadrach]

41 minutes ago, PeteMc said:

I think the numbers probably show I'm over thinking.  But for years my job was to think of what could go wrong and have a plan.  Even when the odds were miniscule, you still had to go through the thought process.  (And the WORST JINX EVER is when one of the crew would say "this is going to be an easy show."  Something ALWAYS happened! )

 

True but this way of thinking is sort of like saying don’t reduce the throttle from cruise until the runway is made because there are no guarantees that you’ll be able to advance it again. It’s absolutely true that the throttle linkage could fail, it’s also true that I could probably learn to manage my approaches to a single power reduction but it would be silly and impractical to do so. It’s much easier just to keep the equipment inspected and in good working order

[Shadrach]

On 12/15/2023 at 1:45 PM, N201MKTurbo said:

None of these pumps are going to be harmed by a few seconds of no fuel. There is enough residual fuel in the pump to lubricate it. The one thing you don't want to do is try to prime a dry fuel system using one of these pumps (aux or engine driven) after the fuel system has been opened up for service. I always remove the fuel hose at the firewall and let the system fill with fuel by gravity before turning the pump on, and then using the aux pump to prime the engine driven pump.

The Aeromotor's modified Dukes pump has sealed external bearings (originally had fuel lubricated sleeve bearings). It has been dry run tested for hundreds of hours without adverse effects. Using it to prime should not be detrimental in the least.

[PeteMc]

9 minutes ago, Shadrach said:

True but this way of thinking is sort of like saying don’t reduce the throttle from cruise until the runway is made

Well...  Sort of think you're over thinking what I'm saying.   By no means am I on the edge of my seat thinking "oh no, this could go wrong or that could go wrong!"  Far from it.  

On the throttle linkage, not one in my wheel house cuz that would really be one of those "sh*t happens."  As for the fuel selector numbers...  I never really cared, but a quick search shows that since 2008 there have been 104 accidents and nothing showed up for throttle linkage (which I'm sure there were some, but too small for my search).  That tracks with hangar flying where I've heard of issues with the fuel selector more than I have about throttle linkage.

 

[N201MKTurbo]

2 minutes ago, Shadrach said:

The Aeromotor's modified Dukes pump has sealed external bearings (originally had fuel lubricated sleeve bearings). It has been dry run tested for hundreds of hours without adverse effects. Using it to prime should not be detrimental in the least.

It’s not the bearings, it is the vanes. They are running on the housing. The old pumps had metal vanes. About 30 years ago they changed to plastic vanes. They look like carbon filled nylon, but who knows. You are right, it probably won’t hurt, but priming by gravity works better and only takes a minute.