Tank Switch Procedure

AdamZ

AdamZ

Touchdown! Greaser!
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Adam Zucker
The other day Gary and I were flying to York PA for lunch. I flew the leg out at 4500'. Came time to switch tanks and I went through my normal tank switch procedure that I learned in my primary training:

1) Mixture Rich.
2) Fuel Pump on.
3) Check gauges
4) Switch tank
5) Note time
6) Check Gauges
7) Fuel Pump off
8) Lean mixture

Gary asked why I went Mixture rich. I responded thats how I was taught. So we consulted the POH actually not a POH in a 67 Cherokee 140 but you get the picture. POH was silent as to the issue.

Any thoughts on this. I suppose if I were flying in Idaho tank switch procedure might be different by its 100'-500' MSL here.
 
Do what the book says. If it says "pump on" for switching, turn the pump on. If it says "mixture rich" for switching, rich up the mixture. If it doesn't, don't. There are planes in which turning on the fuel pump at the wrong time can kill the engine. Likewise, at high DA, riching up the mixture can foul the plugs or just kill some of your power. Since each make/model has its own issues, read the book for that plane, and follow that plane's book's procedure.

But no matter what it says in the book, I would keep an eye on fuel flow/pressure as I switch, and be ready to switch back if anything disturbing happens.;)
 
I switch the tanks in my warrior and then monitor the fuel pressure for a few minutes. If it were to drop and it never has I would switch on the electric fuel pump
 
In the RV, I usually flip the fuel gauge over to PSI, change tanks and wait for a few seconds.. Check the fuel pressure, flip back to flow and check that, then go about business as usual. Don't touch mixture or fuel pump, although I tend to check to make sure the fuel pump switch is still mounted in the panel 'just in case'. ;)

I agree with Ron, though... Do what the book says - they probably have a reason for it (or DID at some point in time).
 
When Gary M and I flew to Ohio and WV62, we wouldn't change the mixture. 530 MSG flashed, I called it out, he hit the fuel pump switch, noted pressure, I switched tanks, we confirmed pressure, fuel pump off, confirmed pressure.

I don't see a reason why you would want to change the mixture setting, the engine isn't operating any differently because you are switching tanks, so why mess with it. I never do in the Cessna's either.
 
I had a 66 Cherokee 140. I turned on the fuel pump, switched tanks, watched fuel pressure, and switched off the pump. Never touched the mixture.

I have no idea where I learned the procedure. I no longer have the plane, nor a POH for it.
 
I can see where mixture rich might make sense in an injected engine to let any trapped air or "stuff" to pass through quickly. It would seem to make less sense in a carbureted engine unless there was a concern that the fuel level in the bowl might drop a bit if the new tank wasn't supplying as desired.

But, I would go by the book if there is one for that aircraft.
 
On the fuel injected Dakota I just move the switch and glance at the fuel pressure. I don't expect that procedure to change in the Frankenkota.

The POH just notes that the fuel pump has no standby function and it is not to be used unless vapor suppression is needed (low side) or the mechanical fuel pump fails (high side). It also notes that the optional primer system is just a momentary switch for the low side of the pump.

Such a wealth of knowledge available in the POH! Maybe someday I should actually read it from cover to cover! (that was a joke, I had read all the PIM before purchasing the aircraft - definitely something to do before operating a fuel injected and turbocharged aircraft).
 
On our SR22, turning on the boost pump enrichens the mixture as noted by fuel flow and EGT. We use the pump but don't change mixture.

BTW our 430 says check fuel balance not change tanks. Typically first change is 30 min then 60 min thereafter.

Joe
 
Book doesn't mention anything about mixture or even the fuel pump it says run one tank for 60 min then run other tank dry then back to first tank.

Its what I learned in primary of course I never learned squat about how to lean properly either.
 
In the the Cherokee 140's Owner's Manual there's not a word about a proper technique. We (students at FBO) always switch tanks without any special procedure, just hold hand on the switch for a few moments and watch the fuel pressure, in case. One of Cherokees we have has a switch with poor detent and can go to OFF position easily, this needs to be watched.

I did read the manual and indeed it contains some interesting information. For example, it was traditional to start with primer, like you would do on a lawnmover. I read the manual and convinced the instructors I knew to try start with throttle strokes if temperature was above +5C. Belive it or not, it makes the start easier when it's hot. Still thinking if I should start on left magneto, as manual recommends.

All this is kind of amusing, but I really wish to become rich and buy an airplane that starts easily, has one "power" lever, and is afraid of no shock cooling. Is this too much to ask and will not happen until and unless I graduate to turboprops?

--
Pete

P.S. Just saw Adam's message re. leaning. Actually leaning is mentioned. It is also mentioned in common checklists for Cherokee, in all of start, run-up and cruise checklists. In my case it is a formality for everything except run-up, since my airfield is 5500 MSL. But we always do it religiously, for spark plug benefit if nothing else.
 
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In low wings I always turn on the fuel pump before switching tanks, but I've never found a POH that specified messing with the mixture. And so far all the Cessna High Wings I've flown have had the fuel selector in "both".

The DA40 I fly will indicate low fuel pressure at higher altitudes without the boost pump, so that's on in cruise above 6000 anyway.
 
I hit the fuel pump on, switch the tank, and keep my hand on the tank valve for about 10 seconds while I watch the fuel pressure. Hand comes off fuel valve and fuel pump goes off.

Going full rich on the mixture seems unnecessary as there won't even be a measurable change in fuel flow provided the valve switch happens successfully. It just means that you're shoving a bunch of fuel into the cylinders that isn't needed and then have to go back and readjust to try to find that perfect spot.
 
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Yeah, me neither. Boost, switch, watch, unboost. Repeat when the GPS tells me to. I do love that thing, that alert itself justified the purchase price.
 
jesse said:
I hit the fuel pump on, switch the tank, and keep my hand on the tank valve for about 10 seconds while I watch the fuel pressure. Hand comes off fuel valve and fuel pump goes off.

Going full rich on the mixture seems unnecessary as there won't even be a measurable change in fuel flow provided the valve switch happens successfully. It just means that you're shoving a bunch of fuel into the cylinders that isn't needed and then have to go back and readjust to try to find that perfect spot.
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That has been my proceedure as well. There isn't any reason I can think of to change the mixture control while switching tanks.

Really a minor issue down low, but I can see that going full rich while at a high altitude, high RPM, while leaned out would cause the engine to hiccup.

Gary
 
zaitcev said:
Still thinking if I should start on left magneto, as manual recommends.
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I'm surprised you can actually select which mag is 'hot' with the switch in the 'on' position. The Cherokees I've flown had one key switch that had 'Off - L - R - Both - Start'.

The 'left mag start' procedure is probably due to the impulse coupling being attached to the left mag.
 
CJones said:
I'm surprised you can actually select which mag is 'hot' with the switch in the 'on' position. The Cherokees I've flown had one key switch that had 'Off - L - R - Both - Start'.

The 'left mag start' procedure is probably due to the impulse coupling being attached to the left mag.
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The older Pa28s only have an Off, Left, Right and Both position no Start.
 
no chris they have a separate starter button
 
Gary said:
No, a big shiny push button "Start". Separate from the key. Kinda old school, like the overhead trim crank.

Gary
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Hmmm.. The PA28-180 I used to fly (late 60's model IIRC) had to push in on the key to engage the starter. It was a standard Off - L - R - Both - Start, but you had to push in on the switch while holding over to the 'Start' position.

We have a simple keyless start for the RV. Separate toggles for Master, Left Mag, Right Mag, and a push button for start.
 
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I would have asked the same question - why change the mixture?
 
AdamZ said:
Book doesn't mention anything about mixture or even the fuel pump it says run one tank for 60 min then run other tank dry then back to first tank.
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In that case, I'd just shift the valve and leave it at that.

Its what I learned in primary of course I never learned squat about how to lean properly either.
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There's lots we learn in primary training for which we never learned the reason.
 
The Warrior Information Manual I have states that in flight the electric fuel pump should be turned on prior to switching tanks and left on for a short period after. There is no discussion of changing the mixture to full-rich.
 
To get OT for a moment, the IAR has separate magneto switches. The pilot's manual instructions have you start on the left mag then bring the right one on after the engine starts.

I use to wonder why you should leave the right one off during starting until a old hand brought this to my attention:

From http://www.experimentalaircraft.info/articles/aircraft-engines-ignition.php

Impulse coupling

During starting of the engine, its crankshaft rotates very slowly (around 120 RPM) and the magnetos at 60 RPM. Generated voltage is very low at that point. Ignition timing is fixed at 25° BTDC, this is too early at low RPM and if a cylinder would fire it could cause violent kickback (rotates momentarily in the wrong direction) and probably damage the starter.

A device called a impulse coupling is used to retard the ignition timing to almost at TDC and an acceleration of the magnet (with a coiled spring) in the magneto to spice up the voltage to help igniting the mixture at TDC. When the engine fires and its RPM rises the timing is set back to 25° for normal operation (between 500 and 2700 RPM). The moment the engine fires and runs idle the impulse coupling detaches and timing is reset to 25° BTDC.

(emphasis mine, and on my engine it is 20 deg. BTDC on the mags).

As I understand it, the twist to start key switches ground the right mag (or the one without the impulse coupling) in the Start position. I've read that some engine mag configurations have impulse couplings on both mags.

Back on topic...hi or lo wing FI engines I've flown the published procedure was/is boost pump on, switch tanks, watch fuel pressure to stabilize, turn boost off. Never touched the mixture switching tanks. I've seen the fuel pressure fluctuate a few times when not using the boost pump, but haven't had a engine so much as cough while doing so. I don't spend a lot of time moving the selector valve and I do go through the BOTH position every time I switch tanks.
 
Never heard of enriching the mixture when switching tanks, and can't think of any good reason to do it. Good reason to not do it is what Jesse said - Unnecessary extra fuel burn, and you have to lean it out again.

If you can reach your primary CFI, ask why he taught you that. I'm guessing the answer will either be "That's how I was taught" or "Uhhhhhh..."
 
Ging rich may actually be a good practice in a turbocharged engine. Howard Fenton used to ask me if I had run a tank dry.....
 
Having learned to fly at an elevation of 6,500ft and regularly flown in high DA environments whenever I hear or read 'Mixture - Rich' it makes me cringe, even if it does say so in the POH.
 
AdamZ said:
The other day Gary and I were flying to York PA for lunch. I flew the leg out at 4500'. Came time to switch tanks and I went through my normal tank switch procedure that I learned in my primary training:

1) Mixture Rich.
2) Fuel Pump on.
3) Check gauges
4) Switch tank
5) Note time
6) Check Gauges
7) Fuel Pump off
8) Lean mixture

Gary asked why I went Mixture rich. I responded thats how I was taught. So we consulted the POH actually not a POH in a 67 Cherokee 140 but you get the picture. POH was silent as to the issue.

Any thoughts on this. I suppose if I were flying in Idaho tank switch procedure might be different by its 100'-500' MSL here.
Click to expand...

I can't imagine why you would go mixture rich either, you do that high enough and you can kill the engine.
 
Fuel Pump? Whats a Fuel Pump?:wink2:

Love my gravity feed, no need to switch system!

(and you all rank on high wing, normally carburated aircraft)
 
Rob Schaffer said:
Wait,.. his plane is a 1967!! :eek: WOW, it's immaculate :thumbsup:
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Hey! Old planes I think are typically nice! :(

(pilot of a '68 and a '69 aircraft)

I never touch the mixture when switching tanks. I do, however, keep the fuel pump on (Lycoming engines - Continentals are different) for about 10-15 seconds after switching and keep an eye on the fuel flow. A mixture adjustment is very rarely required.
 
Ted DuPuis said:
Hey! Old planes I think are typically nice! :(

(pilot of a '68 and a '69 aircraft)

I never touch the mixture when switching tanks. I do, however, keep the fuel pump on (Lycoming engines - Continentals are different) for about 10-15 seconds after switching and keep an eye on the fuel flow. A mixture adjustment is very rarely required.
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Never said they weren't nice,.. recall I was flying the '67 C172H for the past year, and I was very happy with that. The paint, interior, and overall condition of Gary's Cherokee is very sharp, and I wouldn't have even thought it was a '67.
 
Rob Schaffer said:
Never said they weren't nice,.. recall I was flying the '67 C172H for the past year, and I was very happy with that. The paint, interior, and overall condition of Gary's Cherokee is very sharp, and I wouldn't have even thought it was a '67.
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I know, just giving you a hard time. ;)
 
ChrisS said:
Having learned to fly at an elevation of 6,500ft and regularly flown in high DA environments whenever I hear or read 'Mixture - Rich' it makes me cringe, even if it does say so in the POH.
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Good point. Blindly following POH/standard procedures has some advantages over winging it, but IMO it's far better to know the systems well enough to understand the reasons behind the steps so you can adapt to unusual conditions and/or take advantage of operational knowledge gained through experience.

POHs are full of good advice but virtually all the one's I've seen for the kind of planes I fly contain some bad advice and or overly restrictive information as well.
 
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