Running tanks dry in cruise
- Thread starter zbrown5
- Start date
I used to burn a tank dry until I had the rear engine on a Skymaster refuse to relight.
Turned out, the fuel selector decided to fail right after I ground checked it during run-up.
Since then, I leave 10 gallons or so in the tank in case I gotta switch back. I haven't noticed any significant loss of range as a result of the practice.
Turned out, the fuel selector decided to fail right after I ground checked it during run-up.
Since then, I leave 10 gallons or so in the tank in case I gotta switch back. I haven't noticed any significant loss of range as a result of the practice.
Any aircraft that has shafts and U-joints to connect the fuel select handle and the valve(s) give me chills when I have to move them in flight.
Have one of those shafts break in flight in the mountains or over water and you'll understand...
Every airplane I have owned has a lever directly mounted to the fuel valve and in fact my new airplane has an oversized billet handle that is beefy and won't break!
EdFred
Taxi to Parking
I have almost a thousand nautical mile range on my plane but the fuel is in four tanks. Are you suggesting I should just get a 90 gallon tank and mounted on top of the fuselage? GTFOOHWTS.This. Good grief. Stop for fuel or get a longer range plane.
Silvaire
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Silvaire
Bottom line is there is no good reason to do this. Run a tank dry and switch to the other one and if something happens to be wrong with that one or it's lines you can't undo the switch. Knowing exactly to the ounce how much fuel you have in your one remaining tank sounds neat but are you really shaving it that close? If you are then either you have enough to make it or you don't, knowing isn't gonna change that.
EdFred
Taxi to Parking
Except I've already run on the other tanks so I know things are good. I take off on both mains I shut one down climb on the other switch to the tip tanks for cruise (and continue to switch back and forth between the tip tanks to keep the balance even) off both of those shut one off dry tank one dry tank the other back to the main tank that I know is working and back to the other main tank that I know is working. So where exactly is my problem?
The way some of you talk it's like we should only have one tank and never switch.
ircphoenix
En-Route
Seriously. Can you imagine if cars were like that?
EdFred
Taxi to Parking
How many cars have weight and balance to worry about?
Clip4
Touchdown! Greaser!
If you actually do some flight planning and in flight monitoring, you should easily be able to determine when to switch tanks with 10 minutes useable fuel remaining. Pilots who just run the tank dry are lazy. There, I said it.
“Passengers, this is the captain speaking. In a few moments the engines will stop temporarily because other wise I have no way of determining I have enough fuel in the other tank”.
“Passengers, this is the captain speaking. In a few moments the engines will stop temporarily because other wise I have no way of determining I have enough fuel in the other tank”.
KSCessnaDriver
Pattern Altitude
That's just your opinion. Obviously the FAA has zero problems with it, so why do you?
Clip4
Touchdown! Greaser!
I know that operating a fuel pump dry is not a good thing and the electric fuel pumps on many of the aircraft we fly will not produce sufficient fuel flow at full power. So I like to be nice to my engine driven pump.
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Drake the Outlaw
What basis do you have for that claim?
BrianNC
En-Route
Which shows you don’t know what it’s about. It’s about determining the exact amount of fuel/fuel burn you have in a tank, and using that info to your advantage. And many pilots more knowledgeable than you or me have been using it as SOP for decades.
I'm curious as well. Most of the electric pumps in planes I've flown (Bos and Navions) will produce MORE pressure than the engine driven pump. In fact, you specifically don't run these pumps unless you suspect you have a problem with the engine pump.
WannFly
Final Approach
My electric fuel pump produces more pressure than the engine driven one too. Unless that comment was specific to an airplane, I would chalk that up to OWT
midwestpa24
Final Approach
I've run tanks dry. It's no big deal. Fuel pump on switch tanks. The engine is still spinning (way faster than a starter turns it BTW), the plugs are still sparking, and reintroducing fuel will fire right back up again. I've also incidentally killed an engine with the mixture when leaning (about 1mm between running/not running), it comes right back.
For all those worried about the fuel selector. Guess what, if the selector breaks that couple of gallons you left isn't going to take you much further either. Leaving 10 gallons in each tank seriously reduces the range of your aircraft, unnecessarily IMO. Hell, our aux tanks are only 15 gallons in the first place.
For all those worried about the fuel selector. Guess what, if the selector breaks that couple of gallons you left isn't going to take you much further either. Leaving 10 gallons in each tank seriously reduces the range of your aircraft, unnecessarily IMO. Hell, our aux tanks are only 15 gallons in the first place.
Timbeck2
Final Approach
You fellas can run 'em dry all you want. For me, I'll just switch tanks at the top and half of the hour then land and get more when they get down below my comfort level.
Eric Stoltz
Line Up and Wait
I tell ya what.... Went aviating today and had the opportunity to run the tank dry. I need to OH the drain, kinda fussy, but it works, figured this would be the day to not have to drain the tank much. But I just couldn't do it! Even after reading this thread. I tried and totally chickened out with about 4 gallons in there. Perfect VFR day, over my airport, and I just couldn't. I know I'll be considered a failure by some of you, but that law of primacy got the better of me.
Better luck next time?
Better luck next time?
Huckster79
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I’m the same way...I don’t think I could do it- so ur not alone.
My thought is I have 4 hours of flying fuel but my back and bladder only have about a 2.5 hr range, so at this point in my flying career it’s nothing more than a theoretical excercise...
My thought is I have 4 hours of flying fuel but my back and bladder only have about a 2.5 hr range, so at this point in my flying career it’s nothing more than a theoretical excercise...
Zeldman
Touchdown! Greaser!
All of them have weight limits. Although that seems to be either unknown or ignored. When getting into the bigger trucks and recreational vehicles some have weight limits in different cargo areas, and the big trucks will have axle weight limits.
simtech
En-Route
And balance issues as well when loading and toteing a travel trailer. Too much or too little weight on the hitch can cause serious issues. Most people don't think of weighr with their vehicles and I understand but I see way to many half ton trucks pulling trailers that they shouldn't be. It's not safe but they do and have caused serious accidents.
Huckster79
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This topic has led me to do some fuel tank measuring on my new airplane:
With both tanks completely empty and the plane sitting on all three wheels, I'll add one gallon at a time in each tank and measure the depth of the fuel with a dipstick. With the stick vertical and touching the bottom of the tank and the rear of the filler neck, I'll make marks for every gallon in each tank, alternately. I'll also take a photo of the respective fuel gauge after each gallon.
Since my useful load is restricted by my body weight being 70 pounds higher than it was last time I flew a C-140 (getting old and fat sucks), I'll need to know exactly how much fuel is in my tanks in order to stay under max gross weight with a (skinny) passenger!
Following that endeavor, I'll fly the plane on a smooth day and run each tank dry (on separate flights, of course) to see how the fuel gauge indicates in the level, in flight attitude. That will also make me familiar with how the plane reacts with an empty tank.
I plan to take my little airplane on many long flights in the future, so fuel management will be a primary consideration in my flight planning. I believe in using every drop of fuel to get where you are going and I also believe in knowing exactly how much fuel you have in order to make it.
This should be fun.
I was thinking about doing that on my 140 as well,as a visual/finger dip check is difficult being tanks on angle... seems like 30 mins of flying our gas sipper and I can’t easily check it.
What would be best way to drain a tank if I don’t want to burn it dry? Get as close as I can and put clean bucket under the gascolator drain?
I wouldn’t be opposed to running em dry once if I had one of my high time buddies with me... just to see where my unusable mark is in each tank before or after doing the marking on a stick...
Rgbeard
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I've done this in a Cherokee Six, many times, on extended trips.
With four tanks, it's too easy to have a phantom hour of fuel left.
Seventeen-gallon tips are a perfect one-hour of fuel.
With four tanks, it's too easy to have a phantom hour of fuel left.
Seventeen-gallon tips are a perfect one-hour of fuel.
I like to know where my usable fuel is and I like it to be all in one tank when I get below an hour of fuel. So yeah, I run it dry. I don’t get what you think you are gaining by not doing so. Leaving 10 minutes of fuel in there is actually reducing your safety factor by 10 minutes.
There no reason your engine won’t keep running that wouldn’t also be a problem if you switch it some other time. Unless you’re going to use the second tank as only a reserve / backup, which is ridiculous.
With the gauges I can predict it within 3 minutes, and with the totalizer within 1. I only do it on long flights, so I’m at high altitude. It’s a non event.
There no reason your engine won’t keep running that wouldn’t also be a problem if you switch it some other time. Unless you’re going to use the second tank as only a reserve / backup, which is ridiculous.
With the gauges I can predict it within 3 minutes, and with the totalizer within 1. I only do it on long flights, so I’m at high altitude. It’s a non event.
EdFred
Taxi to Parking
When I had my mvp50 installed last year I dry tanked three tanks and circled above the airport with the last one down to about 15 mins minutes of fuel so we could calibrate the tanks and sending units.
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Greg Bockelman
You sure it wasn’t 30 minutes? Wink Wink.
EdFred
Taxi to Parking
Yep, because I arrived at my destination, which was also where I took off from, with more than 30 minutes of fuel when I departed.
§91.151 Fuel requirements for flight in VFR conditions.
(a) No person may begin a flight in an airplane under VFR conditions unless (considering wind and forecast weather conditions) there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed—
(1) During the day, to fly after that for at least 30 minutes; or
midwestpa24
Final Approach
You only have to take off with enough fuel to reach your destination with 30 minute reserve. Doesn't say you have to land with 30 minutes of fuel. Granted, that is more air in the tanks than I'd normally be comfortable with.
Juliet Hotel
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Juliet Hotel
So many wives tales in this thread. So many.
I've run tanks dry more times than I care to count. Used to do it regularly while flying at 350 agl. Banner tow super cub had four tanks. Aux tanks fed the mains, mains fed the engine. You had to burn down the main and then refill the main by pumping from the aux. Aux tanks had no gauges,, mains just had the standard super cub float tubes. Those float tubes made it impossible to see exactly when the main was full because the ball is hidden in the top of the tube and if you overfilled the main you would just be pumping your aux fuel overboard out the vent.
So the typical procedure was to burn fuel off one main until it was down to half. Then burn the other main till the motor quit. Switch back to the first main and run the pump to refill the dry main from the outboard aux tank. Run the second main till the motor quits, switch to the now full main and refill the dry main from its outboard aux.
Could usually predict within 5 minutes or so when the motor would quit. And the motor quitting served as good verification that my fuel burn calculations were correct. The motor quitting itself could not have been more of a non-event. It would run smooth and steady right until it quit. When it quit, the RPM would start to drop just as though someone was pulling the throttle back at a relatively slow but steady pace. Reach down switch tanks and the RPM would come right back. Typical RPM drop from the time it quit until it came back online was generally 200 or so and all of about 4 seconds. ASI and altimeter wouldn't even twitch. Total non-event.
Now lets look at some of those wives tales.
I've run tanks dry more times than I care to count. Used to do it regularly while flying at 350 agl. Banner tow super cub had four tanks. Aux tanks fed the mains, mains fed the engine. You had to burn down the main and then refill the main by pumping from the aux. Aux tanks had no gauges,, mains just had the standard super cub float tubes. Those float tubes made it impossible to see exactly when the main was full because the ball is hidden in the top of the tube and if you overfilled the main you would just be pumping your aux fuel overboard out the vent.
So the typical procedure was to burn fuel off one main until it was down to half. Then burn the other main till the motor quit. Switch back to the first main and run the pump to refill the dry main from the outboard aux tank. Run the second main till the motor quits, switch to the now full main and refill the dry main from its outboard aux.
Could usually predict within 5 minutes or so when the motor would quit. And the motor quitting served as good verification that my fuel burn calculations were correct. The motor quitting itself could not have been more of a non-event. It would run smooth and steady right until it quit. When it quit, the RPM would start to drop just as though someone was pulling the throttle back at a relatively slow but steady pace. Reach down switch tanks and the RPM would come right back. Typical RPM drop from the time it quit until it came back online was generally 200 or so and all of about 4 seconds. ASI and altimeter wouldn't even twitch. Total non-event.
Now lets look at some of those wives tales.
The remaining amount is water? Think about that for a minute. Really think about it.
It really couldn't be less of an event.
I was towing banners when I did it. Unscheduled fuel stops were extremely costly in that game. Obviously most folks are not towing banners and therefore unscheduled fuel stops aren't as big of a deal for them. But fuel planning is fuel planning. In a many four tank airplanes, if you're not running tanks dry, you're putting weight (i.e. fuel) into the plane that is doing nothing for you.
Absolutely true in a dirt simple 172 or anything similar. But not every airplane is a dirt simple 172 with a gravity fed fuel supply from a pair of tanks routed through a fuel selector with a both position.
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Greg Bockelman
I knew that was coming. But I could see a situation where an overzealous FAA inspector would make a case where you intended to land with less than 30 minutes fuel onboard and issue a 91.151 fuel violation.
EdFred
Taxi to Parking
And he'd lose if he went after me with that. I would find a way to make *his* life hell. I learned not to play defense, but to play offense. I know enough people with enough connections he would regret ever bringing it up.
ja_user
Pattern Altitude
In what plane does switching tanks every 30 minutes make sense?
EdFred
Taxi to Parking
Well if you burned the first tank for 15 minutes then went half hour half hour half hour half hour half hour in a Cherokee you would be what I call OCD. When I had my Cherokee I would fly half hour, then an hour, then an hour then dry tank (90 mins) and I should have an hour left. If that tank goes empty before 90 minutes I land early.
Timbeck2
Final Approach
Well, I guess I'm either senseless or OCD. Maybe a bit of both.
EdFred
Taxi to Parking
Why a half hour and not an hour? If you want to keep the tanks that balanced why not every 15 minutes?
Timbeck2
Final Approach
Because a lot of my flights are between here and Phoenix which is an hour. Actually on those flights its more like 20/40 because of climb out.
EdFred
Taxi to Parking
That actually makes sense, but what about when you go to do a 4-hour flight? Yes I did multiple 4 + hour flights in my Cherokee.
Timbeck2
Final Approach
I don't have a good answer for ya Fred, I've just always done it every 30 minutes. If I'm solo, I try to burn more out of the left tank than the right. Maybe because that's the way I was taught, maybe because I've had heavy wing issues in the past and want to rule out fuel imbalance, I honestly can't tell you why. It isn't a sin is it?
EdFred
Taxi to Parking
Not a sin. I just like to get the thought process. I have almost 7 hours of fuel in my current plane and if I did half an hour switches that would be 13 tank switches to min fuel as opposed to 4 or 5 that I currently do. I also burn off the left main first because I'm sitting on the left side and it definitely wants to bank left if I burn right side first.