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Running tank dry

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Bob B

Joined: 30 Nov 2011
Posts: 2
Location: United States

Posted: Wed Nov 30, 2011 10:27 pm Post subject: Running tank dry

Last July I purchased Jim Johannes's beautiful Lightning from his estate.  I now have 32 hrs and 77 landings, it just gets better!



I'm writing to ask the experience of the group in running one tank dry.  How long does it take to restart after you switch to the other tank?  Does one need to use the boost pump?  



My fuel selector does not have a "both" position.



Thanks to all who take the time to answer.



Bob Belshe

N563J

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N1BZRich(at)AOL.COM
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Posted: Thu Dec 01, 2011 3:58 am Post subject: Running tank dry

Good morning Bob,

     Congratulations on your Lightning, and as you said,  it just gets better and better.  To answer your question, I have run a  tank dry during phase one testing on several occasions when calibrating my  fuel quantity gauges and it starts up pretty quickly when you do switch  tanks.  But there are a few things to think about.  The main  thing that caught me slightly off guard was that it quit immediately - no  surging or missing a little before quitting as I have seen when I used to  run a tank dry on long cross countries in past Bonanzas I have owned.  With  those there would be some surging before it actually quit and that would  give you some time to change tanks before the engine actually quite.  Not  so on this set up - it would be running fine, then silence.  Even though I  was expecting it, it was a little startling to have it just stop  running all at once.  I'm not sure why this happens, but  perhaps because of the carb instead of a fuel injection as on the  Bonanzas.  But when I switched to the other tank, it started almost  immediately.  Quickly enough that I didn't have time to switch on  the electric fuel boost pump.  

     However, having done this a few times, I now know  that there is at least one thing you can see that will give you some  warning that the engine is getting ready to stop as it runs out of  fuel.  Just watch the fuel flow indicator and you will see it increase  just before the engine quits.  What is happening is that as the fuel flow  is interrupted, and some air is now in the fuel line, the fuel flow transmitter  will start to spin faster thus giving a false indication of increased fuel  flow.  So if you happen to be watching the fuel flow as the exact time the  fuel tank is being exhausted, you will see the fuel flow go up.   Switch tanks at this time and the engine will not quit before you  get better fuel flow from the new tank.  

     As with all things experimental, this is based on  my experience.  Your mileage may vary.

 Blue Skies,

 Buz Rich   

  

  In a message dated 12/1/2011 1:31:07 A.M. Eastern Standard Time,  rbelshe(at)comcast.net writes:

  	  Quote: 	
		  -->    Lightning-List message posted by: "rbelshe(at)comcast.net"    <rbelshe(at)comcast.net>



Last July I purchased Jim Johannes's    beautiful Lightning from his estate.  I now have 32 hrs and 77 landings,    it just gets better!



I'm writing to ask the experience of the group in    running one tank dry.  How long does it take to restart after you switch    to the other tank?  Does one need to use the boost pump?  



My    fuel selector does not have a "both" position.



Thanks to all who take    the time to answer.



Bob Belshe

N563J





Read this    topic online    here:



http://forums.matronics.com/viewtopic.php?p=359983#359983

	


 [quote][b]

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selwyn

Joined: 12 Mar 2008
Posts: 102
Location: Australia

Posted: Mon Feb 13, 2012 7:42 pm Post subject: Re: Running tank dry

Hi Bob,



A little delayed I know but I thought I would share my experience with running a tank dry.  In October I (with my wife) flew our Lightning from our home in Horsham Victoria to Perth WA for a round trip of some 3000NM (plus sightseeing).  On the way beck we had one long leg from Forrest in the middle of the Nullarbor to Port Pirie, north of Adelaide and I decided to run one tank to close to exhaustion to get a good handle on my fuel situation.  In the event, about two minutes before the clock said zero fuel the tank ran dry.  The engine did not cut dead but ran really rough and probably was not putting out much power.  You will understand that this is my impression in the five seconds or so it took me to flick on the fuel pump and change tanks, I didn't stop to take notes .  



In the event we covered the 530 mile leg in a tick over 4 hours with around 50 min fuel remaining which I think makes the Lightning a fair to middling cross country aeroplane.  Overall we did 33 hours flying at 130kt TAS, 24lph fuel and just under one liter of oil all up.   We had friends in a C172 XP accompanying us and they were 10 knots behind on speed and 10 lph ahead on fuel used.



I think it an advantage that you don't have a "both" option on your fuel management.  If you have both tanks on the engine stops when the first one runs dry and you then have to fiddle about turning tanks off to isolate the empty one by trial and error.  Not a good idea.

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_________________
Cheers, Selwyn
Kit 66 VH-ELZ

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