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

[cnoe]

In reality in my J there are actually only 2 circumstances where the boost pump is truly necessary: 1) to provide pressure for priming before starting, and 2) to provide pressure in the event of a mechanical pump failure.

On the other hand it seems prudent to use the boost for "redundancy" during the critical take-off phase.

Many (most?) will also use it during the landing phase to reduce their workload during a possible go-around.

Using the boost during tank-switching seems like nothing more than busy-work with little or no benefit and my POH doesn't specify doing so either.

Neither do I look for an airport before switching tanks, but then I have no concerns about intentionally running a tank dry or conducting an in-flight mag check, etc.

This is just me though and everybody should operate within their own comfort zone.


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[Bob_Belville]

• When switching tanks I keep an eye on FP for a few seconds after turning the valve but I do not turn on the electric pump. (I use it for cold start priming and for take off.)
• Fuel management: most of us have lots of timing gadgets aboard. I get a switch tanks reminder (each hour) from the GPS 696. The xponder keeps track of flight time. The GTN probably does as well though I do not use that one. Likewise Garmin Pilot on the tablet. I try to remember to start the clock timer on the yoke.
• If it is a 4 hour plus flight I note the "USD" from the EDM on a scratch pad and keep up with how much is used/available from/in each tank in order to approach/land on the fullest tank.
• For a flight under about 1:45 I will usually not switch tanks. If it ain't broke...

[cnoe]

37 minutes ago, Bob_Belville said:

When switching tanks I keep an eye on FP for a few seconds after turning the valve

Excellent point Bob! That's part of my routine as well.

I have a verbal check I make at each switch that my wife is surely growing tired of hearing in her headset: "Fuel pressure good - fuel pressure steady".

[Raptor05121]

My instructor is a stickler for this. He caught me flipping tanks and questioned why I didn't turn on the boost pump. I tried to reason the mechanical pump pulls harder anyway, and his rebuttal was if there was a temporary air line. IMHO, if there was a spot of air, the mech pump would pull it through faster than the electric pump.

[Marauder]

I switch with boost on and will see an increase in pressure. After the switch, I do like Bob and look at the fuel pressure.


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[Alan Fox]

4 hours ago, gsxrpilot said:

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. 

Paul , I had a small screw prevent the lever from turning , I landed immediately to figure it out , But no forced landing issues...

[Alan Fox]

Fuel pump is VERY important if you fly at high altitude (turbo) , and you are injected with a fuel system that returns fuel to the tank ,   Continental systems return fuel to the tank....Fuel that is warm will Boil at high altitudes , It is not uncommon to vapor lock a turbo at altitude....Increasing pressure will raise the boiling temperature.....  Warm is relative to pressure .....Pressure decreases at altitude.....

Edited April 19, 2017 by Alan Fox

[bradp]

For a normal aspirated J it doesn't add much. Fuel still flows by gravity to your gascolator. If there is air entrained between selector points, it will move through regardless of electric or mechanical pump use. I bought one electric pump already and I don't want to buy another one.

 

I use the JPI alarm to tell me when I have run through 10 gals.

 

 

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[cnoe]

Alan is right, and to be clear, what I do in my NA "J" does not apply to the Conti/turbo planes.


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[Bennett]

I'm old school. I turn on the pump just before changing tanks, and turn it off about 10 seconds after I physically move the selector into to new detent. I check that the selector is actually in the detent before letting go of the handle. As much as possible I only switch tanks over airports. My Mooney selectors have been trouble free, but a Piper Dakota that I was a partner in had a horrible fuel selector system to distribute fuel from four tanks (early Dakota). The system was rebuilt four times, as it was prone to failure upon switching tanks. It happened to me when I was changing to the fullest tank prior to landing, and the selector spider leg jammed and killed fuel flow to the engine. Couldn't switch back, and I dead sticked that airplane to a long runway. Later my partner was severely injured, along with three passengers on a Young Eagles flight when the same problem happened to him. I am wary about switching tanks on a clock schedule, and frankly I would rather fly with a slight wing weight imbalance than to just switch tanks based on time. Personally I would not run a tank dry for concern that for a myriad of reasons I couldn't access the other tank.

 

 

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[Hank]

1 hour ago, Alan Fox said:

Paul , I had a small screw prevent the lever from turning , I landed immediately to figure it out , But no forced landing issues...

That's why I switch it on the ground prior to engine start. The checklist says FUEL SELECTOR--Fullest Tank, and I either put it there, or move it away and back again. Never had a problem on the ground or in the air, making the selector move. But I don't switch over airports, as I'm rarely there, and I don't use the electric pump when switching . . .

Edited April 19, 2017 by Hank

[thinwing]

13 hours ago, gsxrpilot said:

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.

Same here,never have in the Bravo nor any other low wing I have flown or owned...the engine mounted fuel pump is either working or not.Switching from tank to tank doesn't unport in the 1 second it really takes

[LANCECASPER]

10 hours ago, yvesg said:

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 do the same, first change at 30 minutes, then once every hour, keeps the same balance as doing it every 30 minutes.

[Alan Fox]

19 hours ago, Bennett said:

I'm old school. I turn on the pump just before changing tanks, and turn it off about 10 seconds after I physically move the selector into to new detent. I check that the selector is actually in the detent before letting go of the handle. As much as possible I only switch tanks over airports. My Mooney selectors have been trouble free, but a Piper Dakota that I was a partner in had a horrible fuel selector system to distribute fuel from four tanks (early Dakota). The system was rebuilt four times, as it was prone to failure upon switching tanks. It happened to me when I was changing to the fullest tank prior to landing, and the selector spider leg jammed and killed fuel flow to the engine. Couldn't switch back, and I dead sticked that airplane to a long runway. Later my partner was severely injured, along with three passengers on a Young Eagles flight when the same problem happened to him. I am wary about switching tanks on a clock schedule, and frankly I would rather fly with a slight wing weight imbalance than to just switch tanks based on time. Personally I would not run a tank dry for concern that for a myriad of reasons I couldn't access the other tank.

 

 

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This should have been replaced , "rebuilt 4 times" is really unacceptable.....That accident should have never have happened..... Unless it was done 4 times over 25 years...

[Bennett]

This should have been replaced , "rebuilt 4 times" is really unacceptable.....That accident should have never have happened..... Unless it was done 4 times over 25 years...

The selector was rebuilt four times in five years. At that time period Piper had no new ones in their supply chain, and there was only one or two shops rebuilding them. Other then the two situations described, all the other incidents occurred on the ground in the run-up areas. Each time that happened the airplane was returned to its hangar, and a mechanic checked the system, and removed the selector unit and sent it out for rebuild. When the selector was returned it was sent to another facility for testing, and in one instance, the unit was sent back to the rebuilder for still another rebuild after the checking facility found a problem with it. This was a serious situation taken seriously, and after my "dead stick" landing, I chose not to fly this airplane again, and was actively seeking to remove myself from the partnership. The Young Eagle accident came during the period I was negotiating to leave. Unfortunately the accident occurred to a very competent pilot who did not share my concerns about the latest rebuild. The aircraft was destroyed, and I have to credit the pilot for managing to fly the airplane to the best place he could - partially in water, near a mud flat so that this fixed gear airplane would not flip over in landing - one door, and inexperienced passengers. He no longer flys, and fortunately the passengers all recovered, and the settlement was within insurance limits. For what it is worth when Piper built the next version of the aircraft they eliminated the four tank system for a two tank system, with an entirely different fuel selector.

 

 

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[RobertGary1]

I see slight fuel pressure fluctuations if I didn't use the pump in my old engine. With my new engine the mech pump holds pressure right at the top of the green so you don't see any indication when the electric pump is on. 

I did worry about a stuck selector so I preemptively sent mine to Lasar for overhaul. 

-Robert

[HRM]

On 4/18/2017 at 10:10 PM, RobertE said:

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?

Sometimes I just forget and nothing bad has ever happened 

I think it's in the FM to do it, doesn't hurt to follow the rules, but breaking this one doesn't appear to have severe consequences. On the other hand, following it and then forgetting to turn it off is bad, bad, bad...

[cnoe]

I think it's in the FM to do it,

I'd like to know specifically what both the older and newer POHs say about boost pump usage (fuel-injected, non-turbo only). Older manuals can be pretty sparse with info and I'm concerned that the newer ones are sometimes skewed towards mitigating liability concerns. I'm not trying to espouse an opinion on anybody else's operations; I'm just truly curious about this.

My 1978 M20-J POH only states "Use of the fuel boost pump should be limited to starting, takeoff, switching fuel tanks, landing, and emergency situations." This statement is written as an operational limitation though, and not an operational procedure. In the operations section it specifically directs boost-pump usage for takeoff and landing but makes no mention of its usage during a tank-switch.


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[Tommy]

On 20/04/2017 at 1:43 AM, Bennett said:

Personally I would not run a tank dry for concern that for a myriad of reasons I couldn't access the other tank.

 

Agree completely. To run it dry in the same fashion as Paul suggested means risk of flying unbalanced as well as not being able to switch back if there is a problem.

[HRM]

12 hours ago, cnoe said:

I'd like to know specifically what both the older and newer POHs say about boost pump usage

OK, I stand corrected. Here's what the "Owner's Manual" for my E says:

I checked the Flight Manual (the one that came with the plane) and it didn't say anything about turning the aux on during tank changes, so I don't know how it wound up on my checklist. I might have missed it.

So I guess it didn't matter all the times I forgot, probably good to exercise it a few times in flight during changeovers, still very bad to leave it running.