Switching tanks

BillG

BillG

Pre-takeoff checklist
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Bill Greenberg
So I come from the Cessna world of "Both" tanks and have never had to worry about when to switch. If/When I finally pick up my Tiger, though, I need to figure this switching thing out. What strategies do people use? A friend suggested that he burns 30 mins off the left in his Archer II, then goes to an hour on each tank (to keep them roughly within 5 gals of each other). Not sure how he tracks that or remembers to switch though. Suggestions...?
 
I use the watch method. If the minute hand of my watch is on the right side of the dial, I ought to be on the right tank. Ditto the left side. I also record the time I actually do switch. I do not put myself in the position of having to set a timer to switch tanks precisely on the hour and half hour by always planning to have more than a half hour in each tank when I land.
 
I use the watch method also. If I flew with one of the new Tigers all the time with the Garmin 430s, though, I would probably just get in the habit of switching when it started flashing it's reminder message. It seems as good a way as any other.
 
For Pipers, I generally start on the left, and switch every 1/2 hour. I do it by my flight plan when I'm going XC (and usually on the ground at the destination). If I'm not flying XC, it's generally a shorter flight and I do it either by watch or by Hobbs.
 
What most Grumman owners do is get one of those big cheapo digital kitchen timers with a countdown function and velcro it to the panel -- make sure its beeping is loud enough to be heard with your headphones on (yes, I know, standing in the store with your headphones on looks funny, but this is safety, not a beauty pagent). Run 30 off the first tank (I run the left first when solo), then run 60's (keeps it within about 25 lb left/right balance).
 
stupid question - why don't they just allow for both? is there a specific design reason they have it go from side to side? wouldn't that make you unbalanced eventually? do these kinds of planes have more accidents related to running out of fuel?
 
The POH often suggests a method. My Arrow says 1 hr one side, then 2 hrs other side, repeat 2 hrs. Personally this is too much weight discrepancy for me so I switch 30 minutes, then 1 hour.
 
Differing only slightly from what Ron L. posted, I burn 1 hour on departure, climb, & cruise from one tank; then switch to the other tank and burn it 2 hours; then switch back to the first tank and burn it dry, noting time to fumes or exhaustion if I'm going for max range. At that point I have somewhat greater than [(1 + time to exhaustion) - 2] hours left in the second tank. The "somewhat greater" is due to the full power climb being on the first tank while the second tank has been used for cruise flight only. I use this method on the Mooney, and IIRC I used it on the Grumman Tiger prior to the Mooney (I may have killed those brain cells). Net is that I'm at worst ~70# left/right out of balance versus the ~30-40# via Ron's method will create (Ron forgot the first 30 minutes will be in part or in total full power climb fuel burn, not cruise fuel burn). OTOH, depending on what you fly, how high, and how it climbs, 30 minutes may not get you to cruise, but 60 minutes surely will. I prefer to have the climb fuel burn confined to one tank so that I have excess in the second tank. Furthermore, if you want to get overly analytical about lateral out of balance then one should burn the left tank first to compensate for the lard in the left seat which is also out of balance if the pilot is flying solo, or flying with smaller passengers, etc.
 
In my Archer I set a 45 min timer on the Garmin 430. That keeps the plane balanced and tank switches to a reasonable number. I also like to have enough fuel in either tank at all times to get to a alternate along the route in case of a problem on one side or the other.
 
When I had my Tiger I just used my watch. If I forgot to switch, the fuel imbalance would remind me. I could tell after only a half hour. Only works if you hand fly and I didn't have an autopilot.
 
Great ideas. I like flying the side of the watch as well as the timer method. I also have a kitchen timer I used to use for approaches but this plane has a built-in timer so I can use it for the fuel. I'll give both strategies a try and see what happens. What about things like Young Eagles rallies, when I'm just making a bunch of sporadic short flights?
 
woodstock said:
stupid question - why don't they just allow for both? is there a specific design reason they have it go from side to side? wouldn't that make you unbalanced eventually? do these kinds of planes have more accidents related to running out of fuel?
Click to expand...
It's all about gravity and suction. High wing planes gravity feed the fuel down to the engine. If anything happened to the fuel line from one tank while feeding on "both," the fuel from the other engine would keep flowing. Low wing tanks feed by suction, and if anything happened to one line while feeding on "both," air would fill the line and you'd be in trouble. So you only see the "both" position on high wing planes. Ken Ibold can probably best fill you in on comparative accident rates.
 
Ron Levy said:
It's all about gravity and suction. High wing planes gravity feed the fuel down to the engine. If anything happened to the fuel line from one tank while feeding on "both," the fuel from the other engine would keep flowing. Low wing tanks feed by suction, and if anything happened to one line while feeding on "both," air would fill the line and you'd be in trouble. So you only see the "both" position on high wing planes. Ken Ibold can probably best fill you in on comparative accident rates.
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Not quite correct. There are low wing airplanes with a both position, my favorite example being the Commander 112/114/115 series. The problems can be overcome, but I suspect most manufacturers are happy to adhere to the KISS principle of airplane design.
 
If I'm flying a relatively short distance, I fly TO on one tank and FROM on the other. 500-600 mile X-countries require swapping the tanks though. I like the watch method since you can look at your watch and tell if you're on the correct tank or not.
 
Ron Levy said:
Ken Ibold can probably best fill you in on comparative accident rates.
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I don't have any specific figures, because I've never gone through the process of calculating them. Anecdotally, however, it is clear that there are some accidents caused by not having a "both" setting. They fall into two primary categories: fuel selector put on empty tank when other tanks have fuel (fuel mismanagement), and malfunction of the fuel selector itself, either from pilot error of missing a detent or the fuel selector failing mechanically somehow. As for the accidents where the fuel selector doesn't function properly, it's usually apparent upon inspection that the mechanism has been poorly maintained -- either worn, corroded or unlubricated.

However, in my opinion that number is lost in the noise of the relatively large number of accidents that are simply the result of trying to fly 3.5 hours on 3 hours of fuel. I would further go so far as to say that improper leaning (running too rich) is probably responsible for more fuel exhaustion/starvation accidents than any kind of issue relating to not having a "both" setting. I say this with a sense of being charitable because that gives the offending pilots an out when they simply cruise along dumb and happy until it gets quiet up front.
 
I'll add a few more things to keep in mind:

It's good to have a systematic method to keep track of time (hands on the watch, timer, GPS reminder), but I teach students not just to switch automatically when the alarm goes off. I want them to look around and switch, whenever possible, when they're near an airport or over suitable terrain for a power-off landing. Selector valves have been known to break. Air or contaminants in the tank or line from one tank has been known to cause an engine to hiccup (or worse).

Second, be very, very careful during preflight checks and runup. Many checklists/procedures suggest that you start and taxi on one tank and then switch to the other BEFORE starting the runup.

This process does two things:


  1. Ensures that each tank can feed the engine.
  2. The runup and associated pre-takeoff checks take at least a few minutes. Switching to the fullest (or, if both tanks are full, the tank you weren't using during taxi) BEFORE starting the runup helps you find out if that tank contains contaminants like water and is feeding the engine before you launch down the runway.
Please don't switch tanks AFTER the runup and then immediately blast off. The accident statistics contain many examples of people who discovered a fuel problem a few seconds after takeoff.

Another thing: my one complaint about the A36 I instruct in is that the fuel selector valve is located down by the pilot's left foot (many Piper models have a similar arrangement). It's impossible to see from the right seat (and it's hardly in the pilot's direct field of view, either).

When it comes time to switch tanks in these aircraft, I get extra friendly with my students and insist on reaching across to double-check the position of the fuel selector and the fact that it's in the detent (trust, but verify). A pilot unfamiliar with the lever can easily leave it out of position, which is the equivalent of OFF. If you're not used to switching fuel tanks, make sure you thoroughly understand how the selector works, how it feels, and if there are any detents, lock-out devices, etc.

Finally, review the POH for your airplane. Some manuals recommend using the auxiliary fuel pump (another item not familiar to many Cessna pilots) when you switch tanks. Using the pump is not recommened on other aircraft under normal circumstances.
 
Joe Williams said:
Not quite correct. There are low wing airplanes with a both position, my favorite example being the Commander 112/114/115 series. The problems can be overcome, but I suspect most manufacturers are happy to adhere to the KISS principle of airplane design.
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To which I'll add that the prudent Commander owner switches tanks during flight to make sure the fuel burn is balanced between tanks. With the long, slender low-wing tanks, a very slight out-of-trim/slip/skid can result in uneven fuel burn.

"BOTH" is recommended (by the POH/AFM) for takeoff, climb, descent, and landing. My proceedure is to use both on takeoff & climb, switch tanks every 30 minutes or so during flight, and switch back to both within 15-30 minutes of landing (associated with the last tank change/balanced fuel).

And yes, I have a fuel totalizer.

You can extract max range by switching tanks.

Beth, there are also some planes, like the Piper Malibu series that have a maximum differential between fuel quantities in each wings due to stress design criteria.
 
The KISS method as noted by Ken is exactly what I do. And I keep a written log of it. The log also helps me in the post-brief so I can determine fuel burn cross checked to earlier flights to spot any trends.
 
I was taught to switch every thrity (30) minutes. I use my watch and or a timer. It sounds as if this is not a method a lot of folks use. Why would you burn 1/2 hr on one tank then 1 hour on the other then back to do an hour on the first? I suspect its because the first half hour may not include taxi and run up but would include climb which has a higer burn rate. Is this why otherwise, Wouldn't it help balance to burn even times on both wings.
 
All great ideas. I was taught to take a look at the ground before switching, Is there a "good" landing spot nearby if for some reason the fuel does not flow aand the engine quits. Over/near a airport is a good choice . (In North Carolina this is easy for there are MANY airports.) ...........KD
 
Want to maximize range? Take off and run one tank for 30 min (or any other arbitrary short amount of time or to your cruise altitude) so you know that tank "works" and switch to the other. Fly until that other one is dry and immediately switch to the first tank. There is no other fuel management to do in the air; you have the maximum range possibility of the airplane; you're not monitoring a timer; you're not looking for a place to switch that happens to be over an airport; you're not putting wear and tear on the valve and boost pump every half hour. Every aircraft type is different, I know, but in mine the left to right "imbalance" is not noticeable.I do not claim this is a lesson for a primary student, but for longer cross countries it is very simple and effective.
 
Another fine example of CHECK THE POH......


My 64 Musketeer is fuel injected. The pumps send about 14 gph up the the engine. The engine burns about 9 & send the rest back to the left tank no matter what tank you have selected.

If you start off with full tanks & the right tank selected you are overfilling the left tank & 4 gal or so is being sent out the vent tube & you will never know till you run out of fuel an hour or so early.

The Musketeer hold 59 usable. I have my way of flying it. I start off with the left tank, At first levelout I run the right for 5 min switch back to the left, run it dry & check the time (3.25 hrs). Then I run the right tank dry ( 2.25) & I know that I have 1 hour left in the left tank. This does the same as ED G by using the first left tank for the most burn situation.



No way is wrong, But do the same thing every time.

The Traveler & the musketeer will show a drop in the fuel pressure gauge about 10-20 seconds before the engine coughts. A good scaner will see it & be able to switch before it coughts
 
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Adam, if you burn 30-60-60... then your imbalance is never more than a max of 30 mins, as opposed to 60-60-60... In a Tiger that can be important (not that I know from much personal experience yet!)

I don't like the idea of running a tank dry. I always wondered about what crud could be at the bottom of the tank that gets stirred up, or what if the selector broke? I'd rather the airplane just keep running. I've now run my new motorcycle out of gas twice and I don't like it. My old bike had a gas gauge and much more range. This bike has a reserve tank instead (which is more typical). Over 100 miles and I start watching more closely and looking for a gas station. Between 106-109 miles and eventually the engine has no power - flip to the reserve tank, wait a few (long) seconds, and keep motoring... Both times were at highway speeds though - ugh.
 
Didn't the older 182 do the same thing (tank transfer and venting) that Emaon's muskateer does?
 
Lance F said:
Want to maximize range? Take off and run one tank for 30 min (or any other arbitrary short amount of time or to your cruise altitude) so you know that tank "works" and switch to the other. Fly until that other one is dry and immediately switch to the first tank. There is no other fuel management to do in the air; you have the maximum range possibility of the airplane; you're not monitoring a timer; you're not looking for a place to switch that happens to be over an airport; you're not putting wear and tear on the valve and boost pump every half hour. Every aircraft type is different, I know, but in mine the left to right "imbalance" is not noticeable.I do not claim this is a lesson for a primary student, but for longer cross countries it is very simple and effective.
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As a word of warning, check the POH for your plane and use common sense.

A lot of things can happen with this method, leaving you no options.

Consider a turbocharged plane, high up, where manifold pressure is dictated by the turbo, which in turn is driven by the exhaust. If you fly to full "quit engine" & the turbo spins down, will you actually be able to get a good airstart? Is it good to have that happen at operating power?

No thanks, I'll work the valve & boost pump.
 
To Bill's point I am not personally qualified to comment on operating a turbo. However, I do know a very knowledgeable turbo normalized Bonanza owner who operates exactly as I described without problems. Actually I learned it from him.

I posed this method as a way to maximize range with the fuel you're carrying. And it's simple. If you don't like that short sputter, a variation I have used is, after the first tank switch, run the other until the low fuel light for that tank comes on. I know from testing this leaves 4 gallons of useable fuel in that tank.
 
BillG said:
Great ideas. I like flying the side of the watch as well as the timer method. I also have a kitchen timer I used to use for approaches but this plane has a built-in timer so I can use it for the fuel. I'll give both strategies a try and see what happens. What about things like Young Eagles rallies, when I'm just making a bunch of sporadic short flights?
Click to expand...

Switch every flight once you reach your target altitude while still near the airport (or when returning to the pattern). There's no need to switch this often, but this policy will eliminate any need to keep track of how much time you've run on each tank.

Alternately, use the engine hour meter, odd hours on the left and even on the right.
 
Ron Levy said:
It's all about gravity and suction. High wing planes gravity feed the fuel down to the engine. If anything happened to the fuel line from one tank while feeding on "both," the fuel from the other engine would keep flowing. Low wing tanks feed by suction, and if anything happened to one line while feeding on "both," air would fill the line and you'd be in trouble.
Click to expand...

There are low winged planes with a "both" selection, but they have a common header tank in the fuselage that's gravity fed from the wings. Two downsides are the safety issues of having fuel in the cabin, and the propensity for such airplanes to have uneven flow from the two wings given the extremely low "head" from the wings to the header tank. Yak-52's and their cousin the CJ-6 are examples of this arangement, in fact there is no way to select an individual wing tank in these planes.
 
No matter which timing method I'm using for any switch of a tank, low or high wing, I do the switch within easy glide of an airport or have my emergency field in mind and preferably, in view.
 
BillG said:
I don't like the idea of running a tank dry. I always wondered about what crud could be at the bottom of the tank that gets stirred up, or what if the selector broke?
Click to expand...

Unless the "crud" is floating, running a tank dry isn't any more likely to draw it into the fuel system and in any case there are screens on the tank outlets. As to breaking a fuel selector, if you repair/lube/overhaul a selector when it gets a little harder than normal to move you won't have that problem unlike the guy I read about that carried vice-grips because he couldn't create enough leverage on the handle to move the selector without them!

I generally don't run tanks dry for different reasons, mostly because the engine stoppage "concerns" the passengers. And if you're paying as much attention to your fuel state as you should, there's little to be gained by regularly running tanks dry.
 
woodstock said:
stupid question - why don't they just allow for both? is there a specific design reason they have it go from side to side? wouldn't that make you unbalanced eventually? do these kinds of planes have more accidents related to running out of fuel?
Click to expand...

The fuel pump on the engine is often above the tank physically.

Practical experiment: (WATER please, NOT avgas for this) Take two cups and fill one full, the other near empty. Take two large inside diameter straws and put one in each cup to the bottom with the other end of both straws in your mouth at the same time. You're now are in the set up for a garden variety low wing fuel system. Suck. The goal is to empty both cups(tanks) without plugging either line with your tongue(fuel selector). The answer becomes obvious real quick. :eek:

BTW: The above experiment is an excellent way to put a smartypants teenager in their place in a resturaunt. Only needs one cup full of drink with the other straw overboard. -- BTDT watched them suck their brains out trying to get a drink. :D
 
To even consider running an aircraft so long that you have to switch tanks to the last, after you have descended, is just foolhardy. Figure out what your fuel range with reserves is, leave enough in the tank so that once you have descended from altitude, your make/miss and alternate fuel is in ONE tank not requiring any more switching.

It's called Judgement! Do you really expect a plane to fly without an adequate supply of "go" juice?
 
In the warrior I fly 1.5 hours on the left tank then switch to the right tank. I plan on never having to switch back to left tank
 
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