Running a tank dry in flight

[crxcte]

I have never ran a tank dry in a Mooney.  But, in an emergency situation, if the tank were ran dry and the engine quit how would it be restarted?  After switching tanks with the fuel pump on, then see if the engine starts on its own?  Or would the engine have to be started with the starter using a hot start procedure? 

Has any one experience this in flight?

[danb35]

The engine windmills quite nicely.  I haven't run a tank dry, but I have stopped the engine in flight using the mixture control.  With the prop control full forward, the engine was still turning about 1500 rpm.  To restart, I retarded the throttle to about mid-travel, and then slowly advanced the mixture until it fired.

FWIW, the factory recommends (at least in my POH) running the tank dry, but I don't see a reason to do that on a routine basis.

[Piloto]

You can easily restart the engine by throthling back, switching to the other tank and turning the electric pump on (you may not need it). As soon the engine gets fuel (assuming still windmilling) it will restart. It is not advisable to be very low on fuel on the tank you will be using for approach or landing. The fuel tanks pick-ups ports are on the rear side of the tank and on a steep descend with low fuel the fuel will move forward thus unporting the ports and starving the engine. The pick-ups are located in the rear to assure fuel supply during take-off and climb. If you find yourself in a very low fuel situation avoid uncoordinated turns and steep descents.

Running a tank dry maximize your range until you find that you cannot switch the fuel selector because the set screw on the knob became loose.  

José

 

[jlunseth]

If I run a tank dry at cruising altitude the turbo stops spinning, and the engine may not restart at all, at least not until the plane is lower down.

You guys go ahead and run your tanks dry without me.

[crxcte]

Thats interesting and thanks for the input.  I don't run a turbo although I fly in high altitude alot. 

[FAST FLIGHT OPTIONS LLC]

This reminds me of an AOPA article I recently read which suggested after an engine failure you intentionally stall your plane in the event you can't restart all while working the starter to get the prop in a certain position in order to achieve a better glide angle by having the prop perfectly aligned a certain way

[Hank]

I read that article, too. Seems it said to stop the prop if you are at least 6000' agl, since you have to slow well below best glide. If it happens to me, I'm just going to pull the prop lever all the way back and look for a good spot to set her down. At that point, the plane will belong to the insurance company instead of to me.

NOTE:  this is for engine failure. If I'm out of gas, switch tanks and hope for a restart. If no restart, then the above applies.

My Owner's Manual recommends running on one tank for an hour, then running the second tank dry to determine the time left on the first tank. It is not a strategy that I use. YMMV.

[N33GG]

A long time ago, and far, far away, I used to fly an airplane with a rather complex fuel system (read that "horrible fuel system") with multiple tanks, and routinely ran tanks dry to know how much fuel was used.  Switch tanks, and the engine would fire right up.  (Each tank had a very small capacity, and the only way to get range was to fly this tank, then that tank, then another...etc.  One day, I inadvertantly flew one tank dry for the first time, and was amazed how easily the engine started when I switched to the new tank!)  I would definately say I got too comfortable with this...

Then, I was flying another aircraft (incidently, it had the same engine as the aircraft mentioned above that I had previously run tanks dry on a regular basis), and I had a bit of a fuel issue, and decided it would be a good idea to run a tank dry to confirm I had used all I could out of that tank.  I had my wife and all three children on board at something over 10K feet altitude.  Engine quit, I switched tanks, and nothing happened.  I tried everything, and nothing.  Fortunately, I was over terrain that was flat and not much above sea level.  The engine finally fired at about 1500 AGL.  I had already picked out my emergency landing field, and was getting ready to land an aircraft off airport with plenty of fuel on board due to fuel starvation, and pilot stupidity.  Talk about a learning opportunity.

I will never run a tank dry again on purpose, unless there are some pretty pressing reasons to do so.

I read the article too, and had a few private thoughts on the matter.

BTW, I have never run a tank dry on a Mooney, and have no idea how a Mooney might respond.

[thinwing]

I have noticed that every post on this subject assumes the engine completely quits...that is rarely the case...just run the tank down that you want and as your tank gets close to empty start monitoring fuel pressure.As the fuel level gets close to empty /usable fuel it will unport the fuel pickup but not totally...you will have plenty of warning by monitoring your fuel pressure guage...it will start to flicker and the engine will start to run rough if you wait to long,switch tanks at first fuel pressure fluctuation and with boostpump on the engine never quits completely...kpc

[crxcte]

That sounds like a good plan.  Does the fuel pressure guage drop in and out (assume out is low pressure) of the green arc?  Or is it bouncing around in the green arc?

[N33GG]

Quote: thinwing

I have noticed that every post on this subject assumes the engine completely quits...that is rarely the case...just run the tank down that you want and as your tank gets close to empty start monitoring fuel pressure.As the fuel level gets close to empty /usable fuel it will unport the fuel pickup but not totally...you will have plenty of warning by monitoring your fuel pressure guage...it will start to flicker and the engine will start to run rough if you wait to long,switch tanks at first fuel pressure fluctuation and with boostpump on the engine never quits completely...kpc

[Immelman]

I have run a tank dry on a few occasions (all intentional), for purposes of calibrating my fuel dip-stick and totalizer, as well as for maximum cross-country range. I'm writing this from an E model (injected NA engine) perspective.

Assuming you're doing this to get all the fuel out on a long distance flight, you can probably do this with little to no interruption or notice to passengers if you have one eye on the fuel pressure (or a passenger doing that for you) and make the switch immediately as pressure starts to fall. In my airplane, in cruise, the fuel pressure is usally absolutely steady. When it drops justa  pound or two - that's it, you're on your last few seconds of fuel.

I have an accurate fuel totalizer in my airpane so I know when this is coming in advance, yet it still takes a few minutes of someone monitoring it as there's always a bit more usable fuel in the tank than I expect. If you make the switch early, it will be a non-event. If you're a few seconds lateon the switch, power loss may occur and it will take several seconds (maybe 10, maybe 15) before things are running smoothly again. In this case retard the throttle about half way (POH guidance here).

One thing I'd advise against is turning on the electric fuel pump. You won't see this in the POH but there is a big sticker on the dukes pumps stating that they should not be run dry. My IA confirms they don't like to be run dry. Of course, I'd turn it on if for whatever reason the engine did not want to re-start.

[kortopates]

To add to some of the above, this discussoin on ability to restart an engine in flight has a lot to do with the engines fuel system and whether NA or Turbo . A carbureted engine, like the C Model, will restart the easiest since it just needs fuel to be restored to the bowl. An injected engine is a whole different matter as the lines need to be presurrized with fuel. Although understandable that the Mooney POH discusses this practice with the C model, I am surprised danb35 reports his F model POH continues the practice given the added pucker factor with fuel injection. Pulling the mixture will keep the lines presurrized but running the tank dry exposes them to air and will complicate and potentially delay restarting. So I have always avoided this practice in fuel injected engines. A turbo engine adds the complication of altititude to restart. At altitude in a turbo, the mixture may be too rich to get it started above 12K as jluneth pointed out. A turbo POH advises it may take both the low boost fuel pump to clear the line and the high boost pumpt to get fuel to the cylinders plus waiting till below 12K to be able to start - thus possibly several minutes of the kind of excitement that George relayed above. Thanks for sharing that George. 

[N33GG]

FYI...it was a Lycoming IO-540 (non turbo)

[John Pleisse]

Quote: Immelma

One thing I'd advise against is turning on the electric fuel pump. You won't see this in the POH but there is a big sticker on the dukes pumps stating that they should not be run dry. My IA confirms they don't like to be run dry. Of course, I'd turn it on if for whatever reason the engine did not want to re-start.

[Immelman]

Just for grins, here is something else to consider trying, which I doubt many people would find objectionable, with respect to learning engine restart behavior when fuel supply is interrupted:

On the safety of the ground, with the engine running, turn the fuel selector off. Note the time the engine runs, fuel pressure indications, and how it dies. Then, turn the fuel selector back on and re-start it. On the ground. It will take some extra time  and cranking, and will likely cough and sputter as things get back to life.

(FYI, this happens on most every annual because the fuel selector and servo screens are removed for cleaning with the fuel shut off, or after similar maintenance items).

Granted, this isn't like an air start, and I am neglecting turbo'd engine behavior as described in posts above, but it could be useful data for knowing how your engine (whether carburated or injected) behaves.

[scottfromiowa]

Only did this once in my 66 M20E.  I sumped tanks and added 20 gallons for trip from Arkansas to Cedar Rapids, IA.  I had traveled for pleasure to sisters with my 80 year old mom.  (her second flight with me, first being trip down).  Winds were stiffer than forcast and I knew after we got in cruise that fuel would be tight.  I had made decision to make a precautionary landing about 15 minutes (by air) south of CID at Washington, IA.  I had about six gallons in tanks in addition to my two hours flying time added 20 gallons.  I had switched tanks after first hour from left to right.  I had Washington in site and was going to enter a right turn for downwind (at pattern altitude) when about five miles south of airport engine misfired...In a speed never to be replicated I unfastened shoulder harness and switched BACK to original left tank.  I skipped downwind and went straight in at Washington.  Right tank was dry and left tank had that six gallons remaining...I had already planned to land as I knew fuel was low, but that was NOT a good feeling when tank ran dry.  Engine smoothed out immediately after switching tanks.  I did not have to turn on boost pump as engine didn't kill, just had first hint that she was going to die from fuel exhaustion.  I exlained to my mom what had happened (after landing) and she didn't think anything of it...ignorance is bliss.  I had told her right after entering cruise that fuel would be tight and she said "no problem, if you need to land before C.R."...

I had planned to switch to the left tank (fullest tank) in pattern, but it was about a minute ahead of me and made the decision for me.

[kerry]

When doing crosscountry at alt 8-10 ft. I usually run my tank dry.  When watcing my fuel pressure going low I switch tanks.  When I don't and the engine stops my wife hates it, but when I switch tanks it fires right back up.  I've been told there's no harm to engine by running a tank dry.

[FAST FLIGHT OPTIONS LLC]

these are things accidents reports are made from

[eldeano]

Quote: 201-FLYER

Ok I'm a commercial rated pilot and have been flying for over 15 years.  I've owned two Mooney's a J and now a K. I've heard alot of things in my time especially about Mooney's but never anything like this. So I have to ask the question....why in the wild wild west would you want to run your tank dry? What if the other tank's fuel line becomes clogged or blocked for example... then your SOL. These are the thing that NTSB accident reports are made of.  I'm not trying to insult anyones flying or judgement making ability but I just don't get it. 

[kerry]

Quote: eldeano

I'm glad I am not just crazy because I was kind of thinking the same thing.

[kerry]

Quote: eldeano

I'm glad I am not just crazy because I was kind of thinking the same thing.

[FlyDave]

Quote: eldeano

I'm glad I am not just crazy because I was kind of thinking the same thing.

[rob]

Quote: 201-FLYER

Ok I'm a commercial rated pilot and have been flying for over 15 years.  I've owned two Mooney's a J and now a K. I've heard alot of things in my time especially about Mooney's but never anything like this. So I have to ask the question....why in the wild wild west would you want to run your tank dry? What if the other tank's fuel line becomes clogged or blocked for example... then your SOL. These are the thing that NTSB accident reports are made of.  I'm not trying to insult anyones flying or judgement making ability but I just don't get it. 

[FAST FLIGHT OPTIONS LLC]

There is this organization called the Aircraft Owners and Pilots Association, you may have heard of them but maybe not. In any event here is an article for you to read with some statistics on the front page

 

http://www.aopa.org/asf/publications/sa16.pdf