I quit turning on the electric fuel pump when changing tanks - is this a problem?

[RobertE]

I know the specified procedure.  But the fact is I worry more about leaving the pump on and burning it up (I did that once in a Cherokee) than any problem that might develop because I relied solely on the engine driven pump.  So what's the logic of turning on the electric pump when changing tanks?  I, by the way, quit doing that about 2000 fuel tank changes ago and never had a problem.  Am I unwise but lucky?

[Hank]

I've never done it in my ten years of ownership, but then my C cruises at 2-5 psi fuel oressure, while your J runs ~30 psi or more, right? My Owners Manual also doesn't mention doing so.

Edited April 19, 2017 by Hank

[carusoam]

I did it today...

Check FF, pump on, switch valve, pump off, check FF...

Not hard to forget because it only takes 20 seconds.  Not like departure with the flaps down and the fuel pump on where things are a bit more tense, take a much longer time and have no particular obvious end point to get it done...

plus I wanted to say I did it today not last month or last quarter....

What would happen if you didn't use the pump... a lull in fuel pressure caused by air or vapor...  

would the engine notice it? Probably in extreme cases...

would the engine recover if the pump was turned on later?  Most likely...

Is there a right way? Yes.  POH says so.  They give no reasons though...  

If you want to generate your own procedure that is better for you... include the FF or fuel pressure before and after the valve change would be helpful at giving a heads up to something about to go amiss...

PP thoughts only not a CFI or mechanic.

Best regards...

Edited April 19, 2017 by carusoam

[Bartman]

I don't use the electric fuel pump when changing tanks, and have not used it in ver 10 years.  However, I only change tanks over an airport and never in the pattern. I do keep my finger on the electric boost pump switch and watch the fuel pressure gauge. 

I do this for the same reasons you listed. 

[Bartman]

And I have never seen even so much as a momentary waver in the fuel pressure gauge. 

[Hank]

26 minutes ago, Bartman said:

And I have never seen even so much as a momentary waver in the fuel pressure gauge. 

Me neither. I don't often fly over airports, but I do try not to switch tanks over hostile terrain unless something decent is close. This is more important after the second hour on the first tank (3 hours into the trip), because I can always switch back if there's an unlikely problem, there just isn't a whole lot to switch back to at that time.

[Andy95W]

I turn the pump on for no good reason other than that's what I was told to do in my first Mooney 25 years ago and now it's more like a tradition.

I'll try to stop but I'm doubtful that'll happen just cause it's a habit now.

[Tommy]

I try to switch close to the airport and have the pump on. Just so I don't forget I leave my left hand on the pump switch and right hand on the tank selector. I was taught to do the same with the gear switch don't take your hand off it unless you can verify the switch is completely up or down. 

Th POH is always written with fair bit of margin to account as much as they can the variations between different planes. And in this case the health of your plane's fuel system. If you are lucky then no problem, if you are not, it's a hard way to find out gliding at 7500 in the middle of nowhere.

Best to try when you right above a nice airfield.

 

 

[gsxrpilot]

I've never once turned on the fuel pump when changing tanks. I change tanks based on fuel load, gallons burned, etc. I certainly don't worry about what's beneath me when changing tanks. It takes 5 seconds, and has never caused a problem.

[carqwik]

I don't turn it on either when switching tanks.  I do try to do it when overflying or nearby an airfield when possible. 

[xcrmckenna]

On my flight from Texas to Oregon with my new to me Mooney I would turn the boost pump on before I switched tanks. But by the time I got to Arizona I was over that... I have my 440 programmed to remind me to switch tanks every 30 minutes.


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[gsxrpilot]

Our Mooney's have such good range and also don't seem to be very sensitive to balance between L & R tanks. So I changed pretty early on, to a fuel management regime based on gallons used. The example from my M20C with 52 gal useable, 26 per side. I'd burn 10 gal out of the right tank, then switch and run the left tank all the way dry, then switch back and know I had 16 gal in the right tank.  The exception to this is that I'll always switch to the fullest tank approaching the pattern to land.

The thinking is 26-26, 26-16, 16-16, 6-16, (I don't want to switch back to a tank that only has 6 gallons) so 0-16, 0-10, land.

I think @201er uses a similar technique.

[RLCarter]

My POH doesn't mention running the electric pump while switching, only for Takeoff & Landing

[Danb]

I have my G1000 set up to advise me to change tanks at 30 minute intervals 

[ArtVandelay]

Our Mooney's have such good range and also don't seem to be very sensitive to balance between L & R tanks.

The thinking is 26-26, 26-16, 16-16, 6-16, (I don't want to switch back to a tank that only has 6 gallons) so 0-16, 0-10, land.
I think [mention=8223]201er[/mention] uses a similar technique.

I switch once, at the halfway point, I don't notice the difference. And always above an airport or at least a descent place to land.

[Hank]

4 hours ago, gsxrpilot said:

Our Mooney's have such good range and also don't seem to be very sensitive to balance between L & R tanks. So I changed pretty early on, to a fuel management regime based on gallons used. The example from my M20C with 52 gal useable, 26 per side. I'd burn 10 gal out of the right tank, then switch and run the left tank all the way dry, then switch back and know I had 16 gal in the right tank.  The exception to this is that I'll always switch to the fullest tank approaching the pattern to land.

The thinking is 26-26, 26-16, 16-16, 6-16, (I don't want to switch back to a tank that only has 6 gallons) so 0-16, 0-10, land.

I think @201er uses a similar technique.

That's what my Owners Manual says to do, except it was written using time:  one hour on first tank, run second tank dry, back to first tank. I change every hour.

[gsxrpilot]

So as I figure it, time doesn't matter (poor choice of words). Fuel as measured in time changes depending on altitude, mixture, etc. But gallons never changes. When gallons reaches 0 the engine stops producing power. In my mind time made more sense before we had fuel totalizers and the ability to measure flow and actual gallons used. Back when all we had were gauges which are never as accurate as we wish they were.  But now that I know gallons used to a 1/10 of a gallon, it makes more sense to manage usage based on gallons.  If I base tank changes on time, I have to write down how many gallons are left after the 30 minutes or 1 hour of time. Switching based on fuel used, means I don't have to write it all down and run calculations to determine how much time I have per tank.  

I use the alarm on my iPad/iPhone/IDF540 to alert me to check fuel just in the unlikely event that I get too wrapped up in a podcast to check it.

 

[Tommy]

Never strikes me as a good idea to run a tank dry. If anything I will leave at least 10 gallons in any side for the unlikely event of needing to sideslip the plane on final and forgot to switch.

And 0-16 just doesn't sound like a well balanced plane for landing.
 

[Bartman]

The reason I change tanks at cruise altitude in gliding distance to an airport is the fuel tank selector itself, not that I think she won't pick up fuel in the other tank. I don't know about you guys but I think putting the fuel tank selector in a recessed area under your foot is asking for trouble.   I have heard of stories of gascollators that got stuck in mid travel for what ever reason. I could see a small pebble or piece of debris  getting in the way interfering with the travel of fuel selector.  

[yvesg]

Until about a year ago I was switching after every 30 minutes... but then I realized that if I did 30 minutes on the first then every hour instead, I would switch less often and in case I forget to switch could find eaily how much time I have left in either tank. I am like Bartman switching at gliding distance in cae something breaks while switching.

Yves

[gsxrpilot]

10 minutes ago, Bartman said:

I have heard of stories of gascollators that got stuck in mid travel for what ever reason. I could see a small pebble or piece of debris  getting in the way interfering with the travel of fuel selector.  

I've heard rumors of such things, but have never actually met anyone who it actually happened to and had to make an unexpected landing. I am always aware of such a thing, and during pre-flight, cruise flight, and just prior to changing tanks, give a quick feel to make sure there isn't any FOD in the area.  I also have a "wrench" made of PVC pipe just incase I need extra leverage.

When flying airplanes, everything is risk management. There are plenty of examples of unplanned landings because of fuel mis-management. There are lots of rumors, but very few, if any examples of the same because of a fuel selector issue. Especially on regularly flown, well maintained airplanes.

Therefore I plan fuel management to be simple, fool proof, and accurate. 

[takair]

I still switch every 30 minutes since I do more short flights than long.  It seems to work out that way for multiple flights.  My 396 has an automatic reminder set.  I don't use the pump, but interestingly, I do notice a very slight, momentary, decrease in fuel pressure some seconds after changing tanks.  You literally have to keep watching it to see it happen, and then it is a drop of about a needle width that recovers as fast as it happens. It probably occurs three seconds after flipping the tank and happens every time.  I don't know if the electric pump would make a difference.

[1964-M20E]

I generally do not use the fuel pump when switching tanks.  I use gallons to determine my switch which generally lines up with hours since I choose to use 10 gallons.  After the first 10 gallons about 1 hour I switch tanks.  I then run 20 gallons or 2 hours on the second tank and depending on how far I am traveling.  Most of my flights are right at 3.45 to 4 hours.  If it is a flight planned for longer than 4 hours I will run 25 to 27 gallons out of the second tank 27.4G usable.  This way I am only switching tanks 2 times in the air.

As for those who choose to switch every 30 minutes to each his own but for me that is way to many mental gymnastics to go through for IMHO too little benefit.  Leaned out at altitude you re switching every 4 to 5 gallons.  As for W&B I have never noticed a wing excessively heavy doing it this way our tanks are relatively close to the center line of the aircraft.  Now if we had wing tip tanks that would be different.

[Oscar Avalle]

I switch tanks every 10 gallons consumed, based on the JPI. I have not used the Fuel Pump for several years and I have also wondered if it was the right thing to do. Regarding where I switch tanks, I basically don't factor that into my decision making.

[MyNameIsNobody]

I use the aux fuel pump for prime at engine start.  I have never used for tank changes.  I do not run tanks dry as I fly for pleasure and find stretching my legs, seeing another airport, taking a leak, landing my plane pleasureable.  I switch my tanks on the hour as I have a clock right in front of me with a timer hand.  I bet if the truth be told there are many that do NOT use a boost pump on take-off and landing...