Running a tank dry??

[67M20F]

In my POH is for fuel management you should, run on one tank for one hour, then run on the other one till its dry, then switch back to the first tank.

Anyone follow this, sometime when I sump my left tank I will get some sealant, really don't want this stuff going through my fuel system.

[TurboExec]

The pickup line for fuel is about an inch up off the bottom and has a nice screen around the intlet....chances are you won't get sealant giong through your fuel system.  But either way I have never run a tank dry, I've always had more fuel than needed.

[67M20F]

I usually am the same way,"the only time you have to much fuel is when you are on fire"

But when I go on a golf trip I am pushing my max load so I can't take full or even 50 gal. So if I had 40gal on a 3hr trip I would want my last ten gal in the same tank not 5 and 5.

[eaglebkh]

I have run a tank dry - almost intentionally.  The pre-buy revealed a seeping panel, so right after purchase I had the panel resealed.  On a long flight prior to having the reseal done, I planned to burn the first 2 hours out of the seeping tank to get it as close to empty as I felt comfortable.  Taking off with full fuel (25g in each side), I approach the 2-hour point in my flight and get ready to switch tanks.   Before I make the switch, the engine starts sputtering.  I switched tanks and the engine came back to life.  Somehow I burned 2.5 hours of fuel in just 2 (assuming 10gph).  It probably would have been a little bit more tramatic if I had not already been ready to switch tanks.  Thankfully my wife was very understanding of the situtaion and did not freak out too much.

What caused the higher-than-expected burn rate?  My guess is that it was a combo of hot summer day (more time climbing to altitude), mixture too rich, and general unfamiliarness with operating the plane  I'm much better at predicting burn rates now...

[Magnum]

I did in once with an instructor, right over the field. We were prepared for it and when the fuelpressure went down we switched tanks and fuel pump on. The engine went out for 1-2 seconds and came back to life. No big deal. But what I didn't like was after it came back it overspeeded until the prop governor catched up.

I don't want to do it again, for the engine it is like pushing the power lever from idle to full power instantly.

[TurboExec]

That is interesting that it overspeed....as long as the engine is turning (whether powered or not) it is creating oil pressure and should have been able to keep the prop at the correct pitch.  Did the RPM drop drastically when this occurred?

[airkraft]

Yup, I've run one dry as well (almost intentionally) in our 1966 E model.  The engine came back in just a few (very long) seconds after switching to the other tank.  The boost pump was already operating since we were being vectored to final for Albuquerque Intl.  I backed the throttle to somewhere less than half travel before switching tanks.  I did not get the over-speed.  The owner's manual advises to retard the throttle if a tank runs dry in order to prevent "engine over-speeding and possible mechanical malfunction."

My plan was to operate on the tank that ran dry until the fuel gauge read just above empty, or the engine began to sputter, before switching tanks.  There was no sputter, it quit abruptly.  What was more unsettling, however, was that the fuel gauge on the empty tank was reading just about half way between 36 Lbs. and empty.  The other side read only slightly higher, so I was not sure before I switched tanks if the other side had sufficient fuel quantity to supply an idling engine.  Obviously not prudent fuel management on my part.

I know several Cessna 320 operators who routinely and procedurely run tanks dry in order to maximize range.   I'm hesitant, however, to make this SOP on my longest flights without more anecdotal experiances from injected Lycoming Mooney pilots.

Anyone know if the fuel gauges can be adjusted to be more accurate especially when nearing the low quantity end of the scale?

 

 

[GeorgePerry]

In all my years of flying I've never run a tank dry (except for drop tanks on Tomcats and Hornets) but they are supposed to be run dry.  I can't see any logical reason too. 

Reciprocating engines do "funny" things when they abruptly stop running...esp. because of fuel starvation.  20-30 seconds trying to get an engine started on deck might not seem like a long time...but try 20-30 seconds of flight time with no power.  The pucker factor will be so high that the seat cushion will have to be surgically extracted from your southern most orifice. 

As for switching between tanks, I’m in the 30 minute p/side camp - keeps the weight relatively even side-to-side. Even w/out fancy engine monitoring / Fuel flow equipment, over the course of a 2-3 hour flight an I0-360 burns an average of 11.5 G/hr.  (STTCC+D).  After a flight I like to “calculate” how much fuel it should take to fill up the tanks when I get gas.  I’m usually w/in .5 gallons.  If one uses proper planning techniques and correct leaning procedures, then there shouldn’t be a need to look at those inaccurate old fuel gauges.  A watch and some simple math will tell you exactly how much has been burned and how much is left.

Personal fuel management rule of thumb:

1.       Know exactly how much is in the tanks before takeoff

2.       Know how long the engine has been consuming fuel

3.       Know the “average” cruise burn rate and apply a safety factor (mine is 10g/hr average with 1.5 G/hr Safety Factor)

4.       Know how much fuel it’ll take to fill up after a flight...See how close your predictions are

5.     Try to always find a "suitable" landing site before switching tanks.  Then check pressure, boost on, switch tanks, check pressure, boost off, check pressure.

6.       Never fly with less than 1 hour of fuel left in the tanks...ever. (this also takes care of the VFR/IFR fuel on board requirements)

If any of the “Know” statements turns in to an “I think” remember - there’s a long list of pilots who guessed wrong.  Fly safe, and keep your engines happy with uniterupted gas    

 

[mooniac58]

Flying here in Hawaii I have my own little rule that I don't switch tanks unless there is an island in gliding range of me

I am not sure if this is silly or not, but for some reason I feel like making the tank switch is a time of higher chance to have a failure (like perhaps if the valve used in the mechanism dies in such a way to starve the engine of gas and no longer be able to change tanks).

Am I being too paranoid?

[TurboExec]

I don't think so, I usually will change only when in gliding distance of an airport.  But I crusie high enough that there is almost always an airport within distance.

[mooniac58]

Quote: TurboExec

I don't think so, I usually will change only when in gliding distance of an airport.  But I crusie high enough that there is almost always an airport within distance.

 Not over here - I spend 60% of my flights more than 30 miles from land, let alone one of the rare airports around here.  Within reason I plan my routes to pass close to or over other islands. 

[Magnum]

Quote: TurboExec

That is interesting that it overspeed....as long as the engine is turning (whether powered or not) it is creating oil pressure and should have been able to keep the prop at the correct pitch.  Did the RPM drop drastically when this occurred?

[29-0363]

I've never run a tank dry until the engine quit and would not deliberately do so unless on the ground.  

Before you get to NO fuel you'll have an ERRATIC flow, and the indication before the engine coughs and dies is when the EGT gives a couple of "blips" as the surging flow leans and enriches the mixture.  At that point you've probably got about 10-15 seconds to change tanks.

I'm in the 30 min a side camp for balance, and the other procedure I religiously follow is T/O with RIGHT tank selected knowing that in the event of EFTO I can only move the selector one way, can do so without looking, and there is a fuel tank between the RIGHT and OFF selections.

[airkraft]

I did not get a 10-15 second warning.  The engine, an IO-360A1A, quit immediately.  Maybe the fact that the auxiliary fuel pump was already operating and that I was in a descent had some effect.

[N207LS]

I have never actually run a tank dry, but have been close enough to cause me to take extra precautions.  I was on the ILS into Las Cruces, NM and my gauges were showing that I was still about half full in the left tank and about 1/4 full on the right.  I had recently purchased the airplane and based on my projections should have had about 3 gallons on the left and 5 gallons on the right, or about an hour remaining per the owners manual calculations.  I decided to trust my gauges and left the tank on the left during the ILS.  After landing and taxiing up, I had the tanks filled.  I purchased 24.8 gallons in the left tank and 23.6 gallons on the right.  As a result, I now have an EI FP 5L fuel flow analyzer, new fuel tank sending units, and wing mounted fuel gauges.  I have reset the K factor several times in my EI unit and am confident that it is accurate on a 4 hour flight to within .3 gallons.  My gauges all read accurately now as well.  Maybe I am paranoid, but I hope to never purchase 49+ gallons in my 52 gallon tanks again, especially when my calculations say that I should have purchased about 43 gallons.  The bottom line is that running a tank dry does not seem to make any sense to me, for any reason.  One of my early instructors told be that there are only a couple of things that are not usable in an airplane, the runway left behind you from an intersection departure and the fuel that is not in the tank... 

[rasman]

Well lets see, I have run a tank Dry both Mooneys on a regular basis Stretching the range. When the engine starts to sputter I switch then engage the fuel pump not a major problem.

[knute]

I spoke with the shop foreman at one of the prominent MSCs here on the west coast about this a year or two ago, and they felt pretty strongly that running a tank dry on an early Mooney is a bad idea.  (I didn't ask about the newer ones)  Specifically, as the seals in the fuel selecter age, they don't seal perfectly, and if one tank is empty, the fuel pump can suck in some air from the empty tank even if the selecter is on the full tank. 

Before I knew this, I ran the tank dry on purpose on a long cross country (for fuel management purposes, as per the POH and so that I knew exactly where the remaining fuel was) and it worked fine.  Very undramatic-  I have a FP5 fuel flow, and by the time the reading was where I was expecting the tank to go dry, within another half a gallon (I have the K factor set conservatively) the engine sputtered, then went quiet.  Throttle back slightly, switch to full tank, boost pump on, and in several seconds it was running again as if nothing happened.  The possibility of sucking air doesn't appeal to me, and the guys who wrote the POH were using a brand new fuel selecter and not one that's been flying around for 40 years.  Better safe than sorry, I'm thinking.  My current procedure is to leave at least 2 gallons in the "empty" tank, and just keep good cockpit notes to track which tank has what fuel level based on data from FP5 and a timestamp of when the tank selecter was flipped.

Everybody has an opinion!

(I don't think running a tank dry before switching to a fuller one will necessarily make the plane fall out of the sky, but I minimize risk where I can with the expectation that it all adds up in my benefit)

-Knute

[GeorgePerry]

Quote: rasman

Well lets see, I have run a tank Dry both Mooneys on a regular basis Stretching the range. When the engine starts to sputter I switch then engage the fuel pump not a major problem.

[Greg Ellis]

I agree with the previous post only in the comment that everyone should run their airplanes where they feel comfortable.  I feel completely comfortable running a tank dry.  Now remember I am not running both tanks dry.  I still land with my reserves and have been doing this for 3 years, since I bought my Mooney.

I did not see it in any of the posts but I recommend reading the following by John Deakin.

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

Whether you plan on running the tanks dry or not is your choice but this article makes a lot of sense and it completely works.

As far as the idea of sucking in junk from your tank, John covers it in his article.  It is a good read and even if you are not considering this procedure.

Greg Ellis, 1963 M20C @ KFWS

[Guest Anonymous]

Quote: gellis

... ... I did not see it in any of the posts but I recommend reading the following by John Deakin.

http://www.avweb.com/news/pelican/182044-1.html  ... ...Greg Ellis, 1963 M20C @ KFWS

[airkraft]

This came from MAPAlist. I don't think they'd mind.

 I cut a yardstick down to just over 12" and taped these measurements to the stick.  It's proven very accurate!

[airkraft]

VERY GOOD article.  Thank you, G Ellis...

[GeorgePerry]

These numbers are probably accurate for "sealed" tank mooneys but probably "not" for airplanes having the O&N bladder mod.

[Greg Ellis]

I also calibrated a Paint Stick but was a little more anal about it.  I started with the empty tank and marked off gallon increments (put in a gallon, marked the stick, put in another gallon and marked the stick, etc...) until full.

[rgaines]

On cross country trips I will run the tank to near dry and until the fuel pressure drops and then switch tanks.  This way I will know my exact range and fuel flow on that particular flight based on current tempurature and altitude.  I also run a timer on each tank so I know approximately when it will run dry so I can plan on switching the tank when the fuel pressure drops.  I never have run competely dry to the point where the engine stops, though on a few occasions the engine ran rough - once I switched tanks with the fuel pump on then no big deal.