Fuel Management Questions - various strategies
 

Good Morning Gents,

I have a T337D. While the T C&D models return fuel goes to the manifold, instead of the main tank, I am still totally paranoid about running a tank dry. Probably a good thing.

The mains have 92 usable, and the aux 36, for a total of 128 gals. If I remember correctly thats out of 131 on board, or about 4 gals in various fuel lines, etc.

My car has a nice way of expressing fuel: X miles to empty.
Would that it be so simple.

I dont want to run a tank until an engine quits. That seems like a bad idea.

I have a totalizer on board. Very nice, but....

For whatever paraboid reason, I assume the tanks may not really be full (even though I fill them), as 210's dont always get full unless perfectly level. Also the heater draws fuel that doesnt run through the totalizer. Etc.

What should I plan to leave in a tank before switching? 4 gals? 2 gals? More? Less?

Whatever the moosh factor, it should apply to all four tanks. If the moosh factor is 4 gals per tank, then that effectively means assume 16 gallons less than 128 available, or 112 available. Maybe too conservative?

My general strategy has been to mostly use the mains. My habit is to refuel always and often. For lots of shorter flights, this means the totalizer is always indicating simply and the aux fuel is 'along for the ride'.

For longer flights, I run the main until they have about 16 gals left, (worst case safely over 30 mins), then switch to aux.

Then run aux down until 8 gals left (4 in each, in case not filled completely or whatever), then back to mains to land.

Thoughts? Discussion? New TSA jokes?

I'm about 1 month from getting my 'thrasher back. She's going to be very very pretty.

D

Fuel burn profile
 

This graph shows the tanks volumes and switchover points.

I assume like a 210 that even though I fill the tanks, they may not be 100% full.

The shadin is set to flash 'low fuel' once 76 gals used, i.e. 16 in mains and 36 in aux

Then burn down 28 of the aux, leaving 8 in the aux just in case.

The shadin also flashes with 40 minutes left, to remind me to go back to mains.

Then switch back to the main for landing, etc.

The 8 in the aux just in case.

I like to think in terms of time in the tanks, rather than gallons. I don't ever want to be at less than IFR reserves, but at a minimum, an hour remaining, or better.

It's hard to run out of fuel if you don't burn off the bottom half of the tanks. This doesn't mean that one should never burn below a half-tank, but simply means that so long as one keeps a healthy margin and doesn't abuse it, running out of fuel isn't an issue.

A good practice is dipping the tanks, rather than simply looking in the tank. It's easy to have a tank appear full, especially with an extended filler neck, and still be able to squeeze considerable fuel into the tank.

In the case of the 210, filling to the bottom of the filler neck leaves the tanks down by a considerable margin; about an hour in each tank.

Simply watching the fuel level in the tank isn't enough. Know how much you anticipate putting into the tank, and verify it with the fuel flow meters on the truck or pump when you do fill the tanks.

Another good practice is to deduct an hour from what you think is in the tanks, and start there. If your best calculation shows five hours of fuel, then plan on four hours max, and take your reserve out of that. I've flown with a lot of individuals who think that being able to squeak the last drop out of each tank of fuel, and being able to run it to the last few ounces was somehow a hallmark of a good aviator. I strongly disagree. I had a new employer once tell me that he expected me to run a tank dry so I'd know just how far I could stretch the fuel. I quit and went elsewhere. No need working around that kind of stupidity.

Fuel flow meters and totalizers work great so long as you've got correct data to begin with. Aircraft gauges are notoriously wrong. If I'm flying cross country, I like to keep a fuel log and compare it to what I calculated I'd have burned when passing each waypoint. Rough calculations are useful, too; half-way there I should see half of the fuel that I calculated in the preflight, gone. Three quarters of the way, three quarters of my planned trip fuel, gone, and so on.

Keep track of your bypass fuel in your tank and burn calculations. There are two basic ways to get silent in flight; one is running out of fuel, but the other is mismanaging (misplacing, misfeeding, etc) the fuel. When fuel is transferred or bypassed from one tank to the other, keep the amount in mind and use accordingly.

Remember, you can always land earlier and take on more fuel. You run out of options, however, if you push it too far. I've flown skymasters with up to a 12 hour endurance if flown properly, and I could do it, but personally I have about a three hour bladder and that's enough. I've done a lot of 6+ hour flights in Skymasters, and that's too long. Land, take a break, and get more fuel. No sense pushing any farther or longer than necessary. Remember, it's supposed to be fun!

I run my tanks the way the owners manual recommends. If you fill them all and refill to take care of any slant caused by unequal fuel weight you should have very close to 128 gallons. Run your mains for the first hour. Then switch to one aux and write down the time. 15 minutes later switch to you other aux. This is so you won't have both tanks running dry at the same time. At cruise you it will take approximately 49 minutes to exhaust your aux tanks. If you pay attention to your fuel flow you will see minor fluctuations before the tank runs dry. Switch then and you won't even notice the event. 15 minutes later you will need to switch your other tank. You will notice yours mains will almost be full again. That is all the fuel you have and you won't be dilly dallying around with "how much do i have in my aux tanks". Also switching from dry mains to aux's is a good way to kill your self. The aux's aren't connected to the aux fuel pumps.

I agree with Ed, do it by the book. I take off and climb to cruise altitude and after about 1 hour on the main tanks, I select both aux tanks. I start my 1 hour timer and after 1 hour I switch the front back to main and leave the rear on the aux. When the rear coughs I switch the rear back to the main and then switch the front back to the aux. When the front coughs I switch the front back to the main. Usually total time on the aux's is 1.25 to 1.3 hours. I watch my clock, fuel gauge and fuel flow for indications. Once in a while the cough will catch me by surprise.

Depending on terrain or location I will stay on mains longer than 1 hour. But for the most it's right around an hour like the book says.

Once the aux's are drained you know that all the fuel you have is in the main tanks. I calculate the time very conservatively and figure my reserve. I know my fuel gauges even though lots of people and pilots in the right seat point and question them. Mine are only trustworthy when they are 1/4 or lower. For the most part they work pretty good and after flying this airplane for 35 years you get to know the systems.

I know have a JPI with fuel flow and I am starting to learn to use it as a tool also. It is amazingly accurate. I have it tied into the Garmin 530 and it continues to amaze me with it's right on numbers.

At times I will put 10 gallons in each aux just to have some fuel sloshing around in the tanks and I have used that hour or so of fuel in some cases but never because the mains were too low. I almost always top the mains after each flight but only use the aux's for cross country flights. I almost never let the mains below 1/2.

Excellent advice. I run tanks dry routinely. It's a safety issue. It was SOP in the piston airliners for decades. (There IS a reason not to run tanks dry on turbines. Different animal)

You want ALL of your fuel in one tank (per engine) when making a max range trip and having your "one hour reserve" IN ONE PLACE. Low, on an approach, sweating weather or nav issues, is NO time to be looking for fuel spread around different tanks, That can kill you and has killed others. Do you want your reserve all in one place and all fuel decisions made or do you want it spread around various tanks, not knowing exactly how much is where when the chips are down?

RUN THEM DRY IN FLIGHT and determine exactly how much REAL usable fuel you have in each tank. Unless you do that, you do not know. Draining the fuel on the ground is not the same and does not work.
Knowing this information could save your life one day.

If you are not comfortable running a tank dry, get an instructor who is and get comfortable with it. It is a safety issue.

I went to work for a firm flying four engine radial powered airplanes, and during the initial ground school, was dismayed to learn that the company actually had a policy of running one engine with a half hour less fuel than the outboards, and one inboard engine with an extra half hour. The theory was that when one engine ran dry, the outboards had a half hour remaining, the other inboard had an hour, and the dry engine could be crossfed off the hour engine.

Most stupid thing I ever heard.

I refused to engage in that idiocy. There is no good reason to run an engine dry.

Why not always carry an extra hour of fuel on board, I asked. Why not, indeed?

It's hard to run out of fuel if you don't burn off the bottom half of the tank, unless you so badly mismanage the fuel that you've left yourself no choice.

Don't run tanks dry. Carry enough you don't have to, and plan ahead to you don't need to engage in that foolishness. It's an unwise thing to do.

We never ran large radials dry, incidentally. The one company had a policy when I arrived, but it didn't take long to get that policy turned around, and I didn't know anyone, personally, who was foolish enough to do it.

That sounds stupid to me, too.


I disagree. There are a number of reasons to run a TANK dry, but I agree, not the entire engine's fuel. A one hour reserve--ALL IN ONE TANK is the safest option.

So, in a Twin Beech, that has three tanks per side, you are recommending leaving fuel in all three tanks? Unless I'm misunderstanding you, let me ask you this. Would you rather have your reserve spread around three tanks or all in one tank with all fuel choices made when you're on approach?

I have no idea who "we" is, but it was SOP at AA, United, Pan AM, Delta and all I know of to run the aux tanks dry in flight on a routine basis. It was a safety issue to have all of the fuel in one place during the approach and possible missed.

Captain John Miller ran R-3350s, four at a time for over 20,000 hours and says he ran the aux tanks dry on EVERY flight because he did not want to look stupid in an NTSB report for smacking the dirt with fuel spread around many tanks.

That said, do as you please. If you are afraid to run tanks dry, one day it is quite possible that you will NEED to and not be comfortable with the process when you need to be.

I run tanks dry routinely on max range trips and have yet to land with less than my one-hour reserve, but it is all in one place with my fuel decisions made more than an hour before landing.

It's not a matter of fear. It's a matter of airmanship and common sense. Running a tank dry is stupid.

Running a wetted component dry is foolish. There's no need.
An hour reseve in one tank should always be kept anyway. It's still no reason to run any other tank dry.

Run an engine dry in flight, you may or may not get it started again. You may or may not damage the fuel pump and fuel system. You may or may not end up cavitating a pump and either damaging it or being unable to restore fuel flow. You run a tank dry and then attempt to switch tanks, and find yourself stuck on the low tank (I've seen it happen), and now all your fuel is in one place...where you can't use it.

Run a tank low. Don't run it dry.

The only exception I've used in the Skymaster has been using tip tanks; pumped into the main based on time, when needed, but only on exceptionally long flights. I found that based on calculated consumption, I could easily push those flights past 9 hours if needed, without ever being concerned about running a tank dry. Nor would I try.

If you continually plan your flights down to the last dregs and find yourself needing to run a tank dry to make up for poor planning, you're doing yourself no favors, nor are you being kind to the airplane. You're abusing your equipment and your chances.

I presently fly (among other things) a large four engine aircraft internationally; fuel management is an important issue. I can't imagine anyone being foolish enough to push fuel to the limits. Land sooner. Plan tech stops. Get more fuel. Don't go as far. I fly into some remote places and fly some very long legs, and I wouldn't ever, ever consider being foolish enough to compromise fuel, let alone run tanks dry. Whether piston or turbine equipment, it makes no difference.

Teaching others to run tanks dry is irresponsible. Hopefully those reading can understand why, or have enough common sense not to go try it themselves.

I'm betting that the four engine aircraft you now fly internationally is a jet or turbo prop. If so, not running tanks dry is proper.

Piston aircraft are different. The WILL restart in flight if they STOP. I've never had an engine not restart--ever... it's part of the FAA certification requirements that you must be able to turn off the fuel, let the engine die and simply add fuel and have it restart. Unless Sir Isaac Newton was wrong, it WILL restart. Putting an aircraft in the dirt (or water) from fuel exhaustion while having fuel spread around other tanks is going to look stupid in an NTSB report. Teaching piston pilots the safety of running tanks dry is the only responsible thing to do. Not running tanks dry on a max range trip in a piston engined aircraft is foolish enough to compromise your fuel situation.

We have the liberty of disagreeing. What should we tell the 400 MILLION flight hours of piston airliners with paying customers on board that ran tanks dry on every flight? What should we tell the thousands of pilots worldwide who are doing this successfully as a matter of routine? That it doesn't work and there are having all sorts of failures as you outline and dying as a result? As Confucius say, "Do not tell man something impossible when he already do it."

That said, do it your way.

Don't call me stupid, Shirley .

Alternatively: http://www.avweb.com/news/pelican/182044-1.html